MSU LIBRARIES .-_‘—. RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped be10w. PHOTOCHEMISTRY OF STERICALLY CONGESTED KETONES By BoIi Zhou A DISSERTATION Submitted to Michigan State University In partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1988 ABSTRACT PHOTOCHEMISTRY OF STERICALLY CONGESTED KETONES by Boli Zhou The photochemistry of various a-arylacetophenone derivatives was investigated. Three types of reactions were observed with these ketones: ot-cleavage, 6-hydrogen abstraction, and 1,3-aryl migration. The photoreactivity proved to be very sensitive to the substitution in the ketones - one minor structural change could lead to a completely different reaction. Dynamic NMR studies revealed that the ketones under investigation represented a group of sterically congested ketones. Bond rotation rates in these ketones are substantially slower than the rates of the photoreactions. On the time scale of the photoreactions, the molecules are locked into conformations from which only certain reactions are allowed to occur. Since different molecules have different ground state conformations, the photoreactivity of congested ketones is very diverse. The considerable decrease in the 6-hydrogen abstraction rate for ot-monosubstituted ketones is attributed to the non-ideal geometry from ' which the reaction occurs. The photokinetic data and conformational analyses of the ketones allowed us to quantitatively correlate the decreased hydrogen abstraction rate to the non-ideal geometric parameters of the reacting conformations. :ci'ie c. ”In” P - ul nab ' | “v'4‘fisl all y; ‘ b It was concluded that a charge transfer process from the on-mesityl group to the carbonyl oxygen in the a-mesityl ketones initiated the unusual 1,3-aryl migration observed. The release of steric congestion in the charge transfer complex is the driving force behind 1,3-aryl migration. The enchancement of on-cleavage rates for a-mesitylisobutyrophenone 7 , on -mesityl-2,4,6-trimethylacetophenone 1 4 , and o:-rnesityl-a-phenyl-2,4,6-trimethylacetophenone 11 is due to either the release of the steric congestion during the reaction or the fact that the ground state conformation favors this reaction. As an extention of the above studies, the photoreactions of these on-aryl ketones in the solid state and the photochemistry of several p-arylpropiophenone derivatives were studied. The photocylization of the p-arylpropiophenone derivatives involves the formation of a 1,6-biradica1 via an intramolecular abstraction of an o-alkyl hydrogen by the excited carbonyl oxygen which cyclizes to the corresponding ‘ 1,2,3,4-tetrahydronaphthols. The low quantum efficiency of product formation is due to the competition of the well known charge. transfer quenching of the triplet ketones by the p-aryl group. The enhancement of the product formation in methanol was attributed to an acid-catalyzed formation of the biradical from the charge transfer complex. 155151 I kfi‘m ran... Acknowledgments The author wishes to thank Professor Peter I. Wagner for his inspiring guidance throughout the course of this work. His inght, advice, encouragement, and sense of humor have made my graduate career both a pleasant and fruitful one. The author is grateful to the National Science Foundation and Michigan State University for financial support in the form of teaching and research assistantships. The author would also like to thank the Chemistry Department for the use of its excellent facilities. Very special thanks are extended to my family members for their support and love. iv Table of Contents Chapter Page List of Tables viii List of Figures xiv Introduction 1 Results 40 I. a-Arylacetophenone derivatives 40 A. Photoreactions in Solution 40 1. General Preparations of the Ketones 40 2. Identification of Photoproducts 40 3 Kinetic Data 53 4. Dynamic NMR Studies 64 5 Molecular Mechanics Calculations 72 6 Relative Conformation of Carbonyl Aryl and Carbonyl Group 78 7. X—Ray Crystallography 79 8. Spectroscopy 79 a. Ultraviolet-Visible Absorption Spectra 79 b. Phosphorescence Spectra 85 B. Photoreactions in Solid State 85 II. p-Arylpropiophenone Derivatives 89 A. Identification of Photoproducts 89 8. Kinetic Data 93 ..... r1 ’v H C. Molecular Mechanics Calculations 93 D. Spectroscopy 95 1. Ultraviolet—Visible Absorption Spectra 95 2. Phosphorescence Spectra 95 11]. Representative Low Temperature N MR and Phosphorescence Spectra 96 Discussion 120 I. o-Arylacetophenone Derivatives 120 A. Photochemistry in Solution 120 1. Triplet Lifetimes and Reaction Rates 120 2. What Determines the Excited State Decay Mode? ~— 127 3. ot-Substituent Effect on 5-Hydrogen Abstraction 129 4. Formations of Aryl Vinyl Ethers 141 5. ot—Cleavage Reactions 150 6. Kinetic Rotational Control in on-Mesitylvalerophenone- 158 7. Possible Formation of the 1,5-Biradica1 via a Proton Transfer from a Charge Transfer Complex 162 8. Photoenolization of ot-(2,4,6-Triisopropylphenyl)- acetophenone 165 B. Photochemistry in Solid State 168 II. p-Arylpropiophenone Derivatives 172 III. Derivation of Equation (25) 178 Experimental 181 1. Purification of Chemicals 181 A. Solvents and Additives 181 8. Internal Standards 182 C. Quenchers 182 11. Equipment and Procedures A. 3191,0095 G. H. Spectroscopic Measurements III. Preparation of Starting Ketones IV. Isolation and Identification of Photoproducts V. Irradiation in Solid State A. B. VI. Irradiation in Cyclodextrin Complexes VII. Dynamic NMR Measurements VIII.Molecular Mechanics Calculations D(. X-Ray Crystallograpgy Appendix References Photochemical Glassware Sample Preparations Degassing Procedures Irradiation Procedures Analysis Procedures Calculation of Quantum Yields Methods Used for Product Isolation In Powder Form In Crystal 183 183 183 184 184 185 185 187 187 188 212 226 227 229 @RSEQE” lable h.) it u List of Tables Table Page 1 lifetimes of o-Arylacetophenones 54 2 Quantum Yields of Photoproducts from ot-Arylacetophenonesu 55 3 Dependence of Z/ E Ratios of Aryl Vinyl Ethers upon Relative Absorbances at 365 nm 63 4 Kinetic Parameters of C Q—CO Bond Rotation for ot-(o-Tolyl)isobutyrophenone 4 66 5 Kinetic Parameters of CQ-Mes Bond Rotation for on-Mesitylpropiophenone 5 I 67 6 Kinetic Parameters of Col-Mes Bond Rotation for ot-Mesitylvalerophenone 6 68 7 Kinetic Parameters of CQ—CO Bond Rotation for ot-Mesitylisobutyrophenone 7 A 69 8 Kinetic Parameters of CQ-Mes Bond Rotation for ot-Mesitylisobutyrophenone 7 70 9 Kinetic Parameters of C a-Mes Bond Rotation for ot-Mesityl-a-Phenylacetophenone & 71 10 Relative Energies of Different Conformations of o-Arylacetophenones . 73 11 Spectroscopic Data Related to Ar and C=O Conjugation --- 79 12 UV Absorption Maxima and Extinction Coefficients of ot-Arylacetophenones 80 viii 13 14 15 16 17 18 19 20 21 24 26 Phosphorescene Maxima (90,0) and Triplet Energy of a-Arylacetophenones Relative Yields of Photoproducts from Irradiation in Powder-- Relative Yields of Photoproducts from Irradiation in Crystal-- Triplet Lifetimes of p-ArylprOpiophenones in Benzene—--- Quantum Yields of Tetrahydronaphthols in various solvents- Relative Energies of Different Conforrnations of p-Arylpropiophenones UV Absorption Maxima and Extinction Coefficients of p-Arylpropiophenones Phosphorescene Maxima (7&0’0) and Triplet Energy of p-ArylPropiophenones Quantum Yields and Rate Constants of Reactions of o-Arylacetophenones Quantum Yields of Aryl Vinyl Ether Formations in Benzene- Rate Constants for e-Hydrogen Abstraction in Several Ketones- Kinetic Data of Cq-CO Bond Rotation for ot-(o-Tolyl)isobutyrophenone Kinetic Data of CQ-Mes Bond Rotation for ot-Mesitylpropiophenone Kinetic Data of C a-Mes Bond Rotation for o-Mesitylvalerophenone Kinetic Data of C q-CO Bond Rotation for o-Mesitylisobutyrophenone Kinetic Data of Ca-Mes Bond Rotation for ot-Mesitylisobutyrophenone Kinetic Data of CQ-Mes Bond Rotation for ix 85 89 92 92 93 95 96 123 142 174 237 237 239 31 32 35 37 39 a-Mesityl-ot-Phenylacetophenone Quenching Indanol Formation from on-(o—Tolyl)-p—Methoxy- acetophenone with 2,5-Dimethyl-2,4-Hexadiene in Benzene at 313 nxn Quenching Benzaldehyde Formation from ot-(o-Tolyl)propio- phenone with Naphthalene in Benzene with 0.007 M Dodecanthiol at 365 run Quenching Benzaldehyde Formation from o-(o-Tolyl)propio- phenone with Naphthalene in Benzene with 0.007 M Dodecanthiol at 365 nm Quenching a-(o-Tolyl)acetophenone Formation from o-(o-Tolyl)valerophenone with 2,5-Dimethyl—2,4-Hexadiene in Benzene at 313 nm Quenching o-(o-Tolyl)acetophenone Formation from ot-(o-Tolyl)valerophenone with 2,5-Dimethyl-2,4-Hexadiene in Benzene at 313 nm Quenching Benzaldehyde Formation from ct-(o-Tolyl)iso- butyrophenone with Naphthalene in Benzene with 0.007 M Dodecanthiol at 365 nm Quenching Benzaldehyde Formation from ot-(o-Tolyl)iso- butyrophenone with Naphthalene in Benzene with 0.007 M Dodecanthiol at 365 nm Quenching Indanol Formation from ot-Mesit'yl- propiophenone with Naphthalene in Benzene at 365 nrn-—-- Quenching Indanol Formation from o-Mesityl- propiophenone with Naphthalene in Benzene at 365 nm—---- Quenching Indanol Formation from ot-Mesityl- 239 240 240 241 241 242 243 243 244 244 41 45 47 valerophenone with Naphthalene in Benzene at 365 nm—--'- Quenching Indanol Formation from ot-Mesityl- valerophenone with Naphthalene in Benzene at 365 nm--- Quenching Benzaldehyde Formation from o-Mesityliso- butyrophenone with Naphthalene in Benzene with 0.007 M Dodecanthiol at 365 nm Quenching Benzaldehyde Formation from a-Mesityliso- butyrophenone with Naphthalene in Benzene with 0.007 M Dodecanthiol at 365 nm Quenching Indanol Formation from ot-Mesityl-ot-Phenyl- acetophenone with 2,5- Dimethyl-ZAJ-Iexadiene in Benzene at 365nm Quenching Indanol Formation from ot-Mesityl-ot-Phenyl- acetophenone with 2,5—Dimethyl-2,4-I-Iexadiene in Hexane at 365 nm Quenching Aryl Vinyl Ether Formation from ot-Mesityl-ot- Phenylacetophenone with 2,5-Dimethyl-2,4-I-Iexadiene in Hexane at 365 nrn Quenching Indanol Formation from Q'MESIIYI'Q' Phenyl-p-Methoxyacetophenone with Naphthalene in Benzene at 365 nm Quenching Indanol Formation from Q‘MQSIIYI'Q' Phenyl-p-Methoxyacetophenone with Naphthalene in Benzene at 365 nm Quenching Aryl Vinyl Ether Formation from q-Mesityl-ot- Phenyl-p-Methoxyacetophenone with Naphthalene in Benzene at 365 nm xi 245 246 247 247 248 249 250 251 251 252 52 33 35 37 49 51 52 53 55 57 Quenching Aryl Vinyl Ether Formation from Q'MQSII‘YI-Q- Phenyl-p—Methoxyacetophenone with Naphthalene in Benzene at 365 nm Quenching Aryl Vinyl Ether Formation from on-Mesityl-on- Phenyl-p-Cyanoacetophenone with 2,5-Dimethyl-2,4- Hexadiene in Benzene at 365 nm Quenching Mesitaldehyde Formation from ot-Phenyl- 2,4,6-Trimethylacetophenone with 2,5-Dimethyl-2,4- Hexadiene in Benzene with 0.007 M Dodecanthiol at 313 nm— Quenching Indanol Formation from on-Mesityl-o-Methyl- acetophenone with Naphthalene in Benzene at 365 nm—--—- Quenching Indanol Formation from ot-Mesityl-o-Methyl- acetophenone with Naphthalene in Benzene at 365 nm--«—---« Quenching Mesitaldehyde Formation from ot-Mesityl- 2,4,6-Trimethylacetophenone with 2,5-Dimethyl—2,4- Hexadiene in Benzene with 0.007 M Dodecanthiol at 313 nm-- Quenching Mesitaldehyde Formation from ot-Mesityl- 2,4,6—Trimethylacetophenone with 2,5-Dimethyl-2,4— Hexadiene in Benzene with 0.007 M Dodecanthiol at 313 nm- Quenching Mesitaldehyde Formation from Q'MQSII‘YI‘ ot-Phenyl-2,4,6-Trimethylacetophenone with 2,5-Dimethyl-2,4- Hexadiene in Benzene with 0.007 M Dodecanthiol at 313 nm— Quenching Mesitaldehyde Formation from Q'MESII’YI' a-Phenyl-2,4,6-Trimethylacetophenone with 2,5-Dimethyl-2,4- Hexadiene in Benzene with 0.007 M Dodecanthiol at 313 nm- Quenching Tetralol Formation from p-(o—Tolyl)isobutyro- phenone with 2,5-Dimethyl—2,4-Hexadiene in Benzene xii 252 253 255 255 257 259 61 62 mmw “Kw 67 59 61 62 2 67 69 at 313 nm Quenching Tetralol Formation from p-Mesitylisobutyro- phenonewith 2,5-Dimethyl-2,4—Hexadiene in Benzene at 313 nm Quenching Tetralol Formation from p-Mesitylisobutyro— phenone with 2,5-Dimethyl-2,4~Hexadiene in Benzene at 313 nm Quenching Tetralol Formation from p-Mesitylpropio- phenone with 2,5-Dimethyl-2,4-Hexadiene in Benzene at 313 nm GC Response Factors HPLC Response Factors Uncorrected HPLC Z/ E Ratios of Aryl Vinyl Ethers—--—---—- Quantum Yields of Photoproducts from Q-AIYI- acetophenone Derivatives Quantum Yields of Photoproducts from p-Aryl- propiophenone Derivatives X-Ray Crystallographic Parameters for ot-Mesityl- valerophenone X-Ray Crystallographic Parameters for ot-Mesityl-2,4,6- Trimethylacetophenone X—Ray Crystallographic Parameters for Q'MQSII‘YI‘Q’PhCflYl- acetophenone 259 260 260 261 262 263 266 272 274 292 Figure WQV¢UI§OJNH t—It—It—t NH0 13 14 15 16 List of Figures Page Polar Transition State for on-Clevage 9 Transition State for Hydrogen Abstraction 11 ot-Cycloalkyl-p-Chloroacetophenones 31 2-Methyl-3-Pheny1-2,3-Dihydrobenzofurans 44 2-Methyl-1-Phenylcyclobutanols 44 2-t-Butyl-l-Phenylcyclobutanols 44 3-Hydroxy-3-Methyl-2-Phenyl-23-Dihydrobenzofurans-—--—— 45 3,4,6—Trimethyl-2-Phenyl-2-Indanols 46 4,6-Dirnethyl-2-Phenyl-3-Propyl-2-Indanols 47 4,6-Dimethyl-2,3-Diphenyl-2-Indanols 47 1-Mesitoxy-1,2-Diphenylethylene 48 Deuterium NMR Spectrum of Reaction Mixture from a-(2,4,6-Triisopropylphenyl)acetophenone—d2 49 1H NMR Spectrum of Reaction Mixture from ot-(2,4,6-Triisopropylphenyl)acetophenone 50 Stern-Volmer Plot for o-Mesitylvalerophenone 58 Dependence of Benzaldehyde Formation from ot-(o-Tolyl)- prOpiophenone on the Concentration of Dodecanthiol 59 Dependence of Benzaldehyde Formation from Q‘(O-TOIYI)‘ isobutyrophenone on the Concentration on Dodecanthiol—~- 60 xiv 17 18 19 20 21 24 26 27 29 30 31 32 $31 37 39 Plot of 1/ (bisc vs. [cis-Stilbene] in Sensitized Isomerization of cis-Stilbene by on-Mesityl-ot-Phenylacet0phenone Restricted Rotation of C a-CO Bond in Ketone 4 Restricted Rotation of COL-Mes Bond in Ketone 5, 6, 8--—-—- Restricted Rotations of COL—CO and Cg-Mes Bonds in Ketone 7 Plot of lnk vs. 1/ T for CQ-CO Bond in Ketone 4 Plot of lnk vs. 1/ T for C a-Mes Bond in Ketone Fr Plot of lnk vs. 1/ T for C a-Mes Bond in Ketone 6 Plot of lnk vs. 1/ T for C Q-CO Bond in Ketone 7 Plot of Ink vs. 1/ T for CQ-Mes Bond in Ketone 7 Plot of Ink vs. 1/ T for C Q-Mes Bond in Ketone 8 X-Ray Structure of oL-Mesitylvalerophenone 5r X-Ray Structure of a-Mesityl-a-Phenylacetophenone 8—-—-——- X-Ray Structure of ot-Mesityl-2,4,6-Trimethyl- acetophenone 14 2-Methyl-l-Phenylcyclohexanols 1H NMR of on-(o-Tolyl)isobutyrophenone 4 at 260 K 1H NMR of ot-(o-Tolyl)isobutyrophenone 4 at 180 K 1H NMR of ot-(o-Tolyl)isobutyrophenone 4 at 170 K 1H NMR of ot-Mesitylpropiophenone 5 at 300 K 1H NMR of ot-Mesitylpropiophenone 5 at 24.0 K 1H NMR of a-Mesitylpropiophenone 5 at 200 K 1H NMR of o-Mesitylvalerophenone 6 at 340 K 1H NMR of ot-Mesitylvalerophenone 6 at 260 K 1H NMR of o-Mesitylvalerophenone 6 at 230 K 1H NMR of of ot-Mesityl-ot-Phenylacetophenone 8 at 300 K--- XV 61 65 67 69 70 71 81 82 91 97 98 100 101 102 103 104 105 106 i9 32 53 NM 41 8 45 47 49 51 52 8} 57 59 1H NMR of of on-Mesityl—ot-Phenylacetophenone 8 at 188 K-- 1H NMR of of on-Mesityl-ot-Phenylacetophenone 8 at 170 K-- 1H NMR of of oz-Mesitylisobutyrophenone 7 at 300 K------— 1H NMR of of on-Mesitylisobutyrophenone 7 at 200 K—---------- 1H NMR of of o-Mesitylisobutyrophenone 7 at 185 Km 1H NMR of of ox-Mesitylisobutyrophenone 7 at 170 K Phosphorescence Spectrum of ot-Mesitylpropio- phenone 5 at 77 K Phosphorescence Spectrum of ot-Mesitylvalero- phenone 6 at 77 K Phosphorescence Spectrum of ot-Mesitylisobutyro- phenone 7 at 77 K _ Phosphorescence Spectrum of a-Mesityl-a-Phenylaceto— phenone 8 at 77 K Phosphorescence Spectrum of o-Mesityl-a-Phenyl-2,4,6- Trimethylacetophenone 11 at 77 K Phosphorescence Spectrum of o-Mesityl-2,4,6-Trirnethyl- acetophenone 14 at 77 K Phosphorescence Spectrum of p-Mesitylisobutyro- phenone 21 at 77 K Geometric Parameters for Hydrogen Abs traction Ideal Geometry for 6-Hydrogen Abstraction Restricted Bond Rotation for ot-Momosubstituted ot-Mesitylacetophenones Steric Interaction during Mesityl Rotation Steric Interaction in the Ideal Geometry Conformation for Charge Transfer xvi 107 108 109 110 111 112 113 114 115 116 117 118 119 130 131 133 134 135 147 60 61 60 61 62 67 69 70 Conformation of 1,2,2-Trimesitylethanone Restricted Rotation in or-Arylisobutyrophenones Conformation of ot-Arylisobutyrophenones Twisted conformation of ot-Mesitylisobutyrophenone-——-—- Transition State of ot-Cleavage from o-Mesityl-2,4,6- Trimethylacetophenone Conformation of ot-Mesityl-ot-Phenyl-Z,4,6- Trimethylacetophenone Destabilized Transition State of y-Hydrogen Abstraction from a-Mesitylvalerophenone 1,6-Biradical Generated in e-Hydrogen Abstraction Ideal Geometry for s-Hydrogen Abstraction Conformational Interconversion in p-Aryl- propiophenones Glassware for Irradiation in Crystal xvii 149 151 152 153 156 157 162 172 173 175 227 Introduction Carbonyl compounds comprise a large and important class of organic substances. The chemistry of this functional group is essential to the understanding of many chemical and biochemical processes. It has been the most widely studied functional group in organic chemistry since the early stage of chemistry. Photochemistry of ketones likewise has occupied the mainstream of organic photochemistry. The study of the photochemistry of carbonyl compounds has helped in the understanding of very fundamental 31 _ kisc '1' k, 1 hV kr kd kp kt ka Products 3° ' L Products Schemel questions in photochemistry. These questions have to be answered to understand how light produces chemical changes in more sophisticated 1 chemical and biological systems. The photophysical and photochemical processes of molecules can be best described with a Iablonski1 diagram (Scheme 1). Absorption of a photon promotes energetically a molecule from the ground state to the singlet excited state. The excited state molecule can decay to the ground state via emission of light (fluorescence) or radiationless decay. The former has a rate constant (kf) on the order of 106-1095'1, and the latter (kd) 105-108 s‘l.2 PhotOchemical reations are possible from the excited singlet. The excited singlet can also undergo intersystem crossing to an excited triplet state. Typical rate constants for intersytem crossing (kisc) are on the order of 107-1010 s'l.2 Direct population of the triplet state from the ground state by absorption of light is forbidden by spin selection rules. The excited triplet can decay via radiative deactivation (phosphorescence) with a rate constant, kp, from 101-~104 s‘l.2 It can also undergo radiationless decay and chemical reaction. Quenching of the triplet state by energy transfer and charge transfer can occur with a rate constant as high as the rate of diffusion in a given solvent (<1010 M"I s‘l).3 For phenyl ketones, the rate constant of intersystem crossing, kisc' is about 1011 34,4 so fluorescence and radiationless decay are negligible. As a result, the quantum yields of intersystem crossing in phenyl ketones are close to unity.5b'c Thus irradiation of a phenyl ketone results in an indirect population of its lowest excited triplet state. Phenyl ketones have two low lying triplets, a 11,11. triplet and a mn‘ triplet, whose energy levels are affected by the ring substituents. The n,n' triplet comes from excitation of a nonbonding electron of the carbonyl group to a n-antibonding orbital, creating an electron deficient oxygen. The chemical behavior of the n,n‘ triplet state is thus similar to that of an alkoxyl radical. ot-Cleavage, hydrogen abstraction, and charge transfer from an 3 electron donor are the reactions frequently observed.6'8 The mu" triplet, on the other hand, arises from promotion of an electron form a n-bonding orbital to a nI-antibonding orbital. This results in a shift of electron density from the aromatic n-system to the carbonyl oxygen, generating an electron rich oxygen (Scheme 2), and makes the mn‘ triplet much less reactive than I’ . . . . . the ma tnplet, or nonreactive, 1n the reactions mentioned above. However, Scheme 2 thermal equilibration between the triplets can occur, if they are close enough in energy. As a result, ketones with a 11,11’ lowest triplet state do undergo typical n,n‘ triplet reactions, but with a slower rate, which is a reflection of the population of reacting n,n. state in the equilibration. The reaction rate constant can be expressed as follows, kobs = k,(n,n)X(n,n) (1) where kobs is the observed rate constant, kr(n,n) is the intrinsic rate constant of the n,1r’ state, and X(n,1r) is the percentage population of the n,n" state in the equilibrium.53I9"11 During the course of research involving the photochemistry of ketones, a wide variety of reactions have been reported. The reactions closely related to the research presented in this thesis are summarized below. ot-Cleavage Reactions An excited ketone can undergo ot-cleavage reaction. The cleavage is followed by disproportionation, coupling, or hydrogen abstraction from a hydrogen donor, of the radicals generated by the cleavage. This reaction is frequently referred to as N orrish Type I reaction (SCheme 3).23a-b O O h v II z/JL\\ -—-—--—D> PhC- + R' Ph R 4.» Products (disproportionation, coupling, hydrogen abstraction) Scheme 3 The rate constant of the reaction depends on the nature of the excited state, on the relative stability of the alkyl radicals formed, and probably on the degree of steric crowding in the reactant ketone. These points are demonstrated with the following examples. The reaction has been generally recognized as a reaction of a n,n * excitation. The simple concept of n,n" excitation resulting in weakening of the or-carbon bond by overlap with the vacant n orbital has been a useful theoretical model for the reaction.12 This simple picture is also consistent with the well known behavior of alkoxy radicals.l3"14 When the excited state configuration is n,n*, no such overlap is possible and the reaction does not occur. Lewis15 has shown that pivalophenone, which has a lowest n,n* triplet state cleaves with a rate constant of around 107 5'1, but p-methoxypivalo- phenone with a mu" lowest triplet state has only a reaction rate constant of only 105 s'l. Furthermore, in the same study, p-phenylpivalophenone, which also has a mn‘ lowest triplet state, is essentially stable to photolysis (Reaction 1). hV ’ )I. + (CH3)3C° R=H, pivalophenone R=p-CH3OPh, p-methoxypivaphenone R=Ph, p-phenylpivalophenone Reaction 1 Baum16 reported a similar study with 2-phenyl-1-indanone and 2,6-diphenyl-1-indanone. Although 2-phenyl—1-indanone cleaves efficiently to isomeric products, 2,6-diphenyl-1-indanone affords little product. This observation is consistent with the fact that 2-phenyl-1-indanone has a n,n* lowest triplet and 2,6-diphenyl-1-indanone has a 11,11" lowest triplet (Reaction 2). 6 In the case of aliphatic ketones, where both singlet and triplet. state can be populated, it has been shown that the triplet state of an aliphatic ketone cleaves about 100 times faster than the first formed singlet.17'18 Turro17 has estimated the n,1r" singlet and triplet reactivity towards or-cleavage with several cyclic ketones. It was concluded that the triplet rate constant of these ketones was larger than 5x1010 s'l,and on the other hand the singlet rate constant was smaller than 2.5x108 s'l. R=H, 2-phenyl-1-indanone R=Ph, 2,6-diphenyl-1-indanone Reaction 2 In a separate study, Yang18 observed that di-tert-butyl ketone underwent the type I process with a rate of 6x107 s'1 from the singlet excited state and with a rate of 7-9x109 s‘1 from the triplet. While or-cleavage is the major mode of deactivation for certain aliphatic ketones,19 phenyl ketones undergo o-cleavage at much slower rates. Even in or,o-dimethylvalerophenone, y-hydrogen abstraction is sufficiently fast that on-cleavage comprises only about 5% of the reactivity.20 In fact triplet aliphatic t-butyl ketones ot-cleave about 4000 times faster than triplet pivalophenone.21 The triplet energy of aliphatic ketones is normally larger than 79 Kcal/ mole, while that of phenyl ketones is around 74 Kcal/mole.22 The energetic difference is an important factor responsible for the different activities towards ot-cleavage reaction between aliphatic and phenyl ketones. High triplet energy facilitates the breaking-down of the strong OC-R bond (80-90 Kcal/mole).20r24c O ) Ar h v R1 R2 + PhCOCOPh + ArCI—lRle 1/ 1 (5‘1) R1=R2=H, Ar=Ph 1.6x106 R1=Hv R2=CHs Ar=Ph 2.1x107 R1=R2=CHs Ar=Ph 1.2x108 R1=H, R2=Ph, Ar=Ph 1.0x103 R1=R2=H, Ar=p-C1Ph 1.9x106 R1=R2=H, Ar=p-FPh 2.8x 1 o6 R1=R2=H, Ar=p-MePh 3.6x106 Reaction 3 Lewis24 reported a detailed study of the photochemistry of ox-phenylacetophenones (Reaction 3). The products observed upon the irradiation of ketones can be accounted for in terms of a general mechanism shown in scheme 4. The radicals are formed initially in a solvent cage. Possible cage reactions of the caged radical pairs include recombination of the radicals to give ground state ketones, diffusion to separated radical pairs, and disproportionation .in the cases where it is possible. Noncage reactions include recombination, coupling, hydrogen abstraction from an external hydrogen atom donor, and disproportionation where it is possible. The formation of caged radical pairs is demonstrated by the fact that 33% of s-(+)-or~phenylpropiophenone undergoes racemization upon irradiation. The racemization arises from the recombination of the radical pairs in solvent cages.24C 0 w 0 I \ Ph P/kPh z [P/IK ] ——' PhCHO «FY ' ' Ph \ kdiff J K“ / RSH PhCOCOPh + Ph—|-—+—Ph PhCHO + RSSR + Y Ph Scheme 4 The separated radicals can be trapped with radical scavengers such as thiols. Lewis has shown that addition of low concentration of dodecanethiol greatly increases the quantum yields for benzaldehyde formation. The quantum yields rise to a maximum of ca. 0.45 at 2x10’3 M thiol concentration.24a'b .T his is the point where all the outcage benzoyl radicals have been trapped to form benzaldehyde. Electron donating groups on the ot-ring accelerate the reaction, indicating an early trasition state with a moderate degree of ionic character. The transition state can be depicted as in Figure 1.24 0* .ALyGX 5+ Figure 1 a-Substituents also speed up the cleavage. However, it was concluded that the effect of substituents upon triplet lifetimes shows that the rate constants do not depend on the stability of the resulting radicals, but rather on the ground state steric effects with these ketones.”b Hydrogen Abstraction Reactions Photoexcited ketones undergo characteristic hydrogen abstraction from compounds having reactive hydrogens. This reaction was first observed by Ciamician and Silber at the begining of this century.25 When benzophenone was irradiated in ethanol, benzpinacol was formed by coupling of benZOphenone ketyl radicals generated by hydrogen abstraction from ethanol by her.“ 10 by benzophenone (Reaction 4). 0 11V ’ CH3CH20H + CH3CHOH Reaction 4 ’ Ph OH OH . )\ + —— Ph ‘Sx ‘ SchemeS Since then a wide varity of photochemical hydrogen abstractions have 11 been reported. Intramolecular hydrogen abstraction reactions are probably the most important development of the initially discovered reaction. Norrish Type II reaction is the classic example of intramolecular hydrogen abstractions.23cr5a This reaction involves formation of a 1,4-biradical via abstraction of a y-hydrogen by the excited carbonyl oxygen. The biradical can either cleave into an olefin and the enol of a smaller ketone, or cyclize to a cyclobutanol (Scheme 5). The rate constant for internal hydrogen abstraction depends on electronic configuration, on C-H bond strength, and on conformational factors. It has been well accepted that hydrogen abstractions occur from the n,n" excited state of the ketones. The radical-like oxygen of a n,n* excited ketone behaves in the same way as an alkoxy radical (Figure 2). Hydrogen abstraction is one of the most frequently observed reactions for an alkoxy radical.26 ' Simple phenyl ketones undergo hydrogen abstraction reactions from their n,n‘ triplet states. Ring substituents that lower the n,n" level below n,n" level derease the observed rate constants for the reactions. Figure 2 Yang9 has shown that methyl and methoxy substituents lower the reactivity of acetophenone in its photoreduction. Wagnerw’11 has reported a 12 study of substituent effects on the photoreactivity of ring substituted valerophenones. Phenyl, methoxy, thiomethoxy, cyano, and methyl groups as well as chlorine atom alter the n,n" and mu" energy such that the 11,11" is the lowest triplet for the phenyl ketones with such substituent. As a result, these substituents decrease the chemical reactivity of the ketone triplets. The triplet reactivity of the ketones decreases as the energy gap AET between the n,n" and 11,11" triplets increases. The following scheme (scheme 6) outlines the kinetic possibilities of the excited ketones. Population of n,n" singlets is achieved by direct irradiation. The excited singlet states then undergo intersystem crossing to the triplets, which can either react, or decay to the ground states. A fast equilibrium is assumed between the two'triplet states. In Products GS Scheme 6 general, the possibility exists for direct decay of the n,n" triplet to the ground state ketone, but for most simple ketones k,“ >> kdn with kdn being < 106 5'].2 The mu" triplet can decay to ground state, or possibly react slowly. However, the n,n* triplet is frequently considered nonreactive on the 13 time-scale of the n,11" reactions. 2—Acetonaphthone is known to have a 11,11" state so much below its n,11‘ state that it can not be photoreduced by secondary alcohols. Although it does react with a more powerful hydrogen donor such as tri--n-butylstannane,27a the deactivation of the ketone towards the photoreduction is well illustrated. 2-Valeronaphthone undergoes type II reaction with very low quantum efficiency. The reaction is unquenchable by triplet quenchers, and thus is believed to occur from its singlet state, rather than from its n,11" triplet.27b'C 4-Phenylbenzophenone provides another example of the reduced photoreactivity for a ketone with a 11,11" lowest triplet. The reduction of 4-phenylbenzophenone proceeds with a rate constant of 1x103 M‘ls'l, 10‘4 times as great as that displayed by ketones with n,11‘ lowest triplet (Reaction 5).23 OHOH h Ph—O—coph v 5 Ar I I Ar 2-Propanol I I Ph Ph . Reaction5 The naphyl and biphenyl ketones discussed above have 11,11" triplet levels so much below their n,11“ triplet states that equilibration may not be possible. The reactivity shown can be viewed as the intrinsic one for 11,11" excitation, like what is observed with c=c double bonds,29 and reflects the amount of unpaired spin density on oxygen in the 11,11‘ triplet. n,11* Singlet ketones abstract hydrogen atoms as rapidly as n,11" triplet 14 ketones do, if the intersystem crossing is slow enough to allow a substantial population of the singlet states. In fact, the type II reaction was one of the first in which involvement of both triplets and singlets was demonstrated.30 However it was noticed that the details of the singlet and triplet reactions are very different. It is now recognized that the two excited states follow different mechanisms. Although a biradical is generally involved in a triplet intramolecular hydrogen abstraction, a singlet reaction prefers non-biradical mechanismssar31 Any intramolecular reaction requires the two interacting groups to get close to each other in such a way that proper orbital overlap and reaction can occur. This requirement makes photochemical intramolecular hydrogen * x Y 111) x Y k, U ——> U >Products k-t k1 hV * XWY ——> X Y ———> Decay Scheme 7 abstraction reactions very sensitive to conformational limitations, since the photochemical processes can occur at a competitive or faster rate with respect to the conformational motions. Scheme 7 summarizes the general problems}32 The ground state is composed of an equilibrium mixture of mom Xand ext excited c coefficie: crime tut do D—& ’K“ p) 15 conformations with generally a small fraction favorable for reactions between X and excited Y. Excitation instantaneously produces the same distribution of excited conformers modified only by any slight difference in extinction coefficients between different conformers. The competition between conformational change, reaction, and decay (all other excited state processes that do not lead to the product in question) provides three boundary conditions: 1. Excited State Conformational Equilibrium k1, k_1 >> k1,, Rd 2. Ground State Control k1, k_1 << krr kd 3. Rotational Control k1 ~ kd, k_1 < kl' Excited state conformational equilibrium is the most commonly observed control factors in photochemistry, since in most sterically non-rigid molecules, conformational changes can occur prior to any photoreactions. A number of examples have been reported in literature.33'35I37‘ In general, the larger the fraction of excited state molecules in the conformation favorable for the photoreaction, the larger the observed rate constant for the reaction. For example, it was found that y-hydrogen abstraction is more rapid in cyclic ketones than in acyclic ketones.33 The reaction rates are shown above. It was suggested that the rate enhancements reflect the increased number of "frozen" C-C bonds in the reactant, i.e., a decreased probability that molecules can exist in a conformation unsuitable for the reaction. In support of this interpretation, 2-benzoylnorbornane 16 shows the same triplet activation energy as valerophenone but an activation entropy that is 8 eu less negative. 8-1 RH, 10 5 Ba, Kcal AS+, eu 70.0 3.7 -4 H COPh Alexander34 has shown that an excited state equilibrium between the two triplet ketone conformers is an important factor in the photochemistry of cyclobutyl phenyl ketone. The rapid ring puckering motions of cyclobutane allows conformational equilibrium to be established before excited states decay. The low quantum yield of type II reaction and long triplet lifetime was ascribed to a very low equilibrium population of the pseudoaxial conformer, from which the reaction is to occur (Scheme 8). Wagner35 hasfound that ct-(o-alkylpheny1)acetophenones undergo photocyclization to 2-indanols via triplet 6-hydrogen abstraction, with the 17 * Nico/V 4 ' ———> Ph/\0* 9 ° on Scheme 8 kinetic data listed below (Reaction 6). The photocyclization of the ketones is quite sensitive to the substitution on the ot-ring. This manifests itself in two different effects. Q h V OH MEI/It » R“ P h P h ‘t"1x10'9 ot—(o-Tolyl)acetophenone 0.16 or-(2,5—Dimethylphenyl)acetophenone 0.26 ot-Mesitylacetophenone 1.1 Reaction 6 First, alkyl substituents on the ot-ring increase the rate of hydrogen abstraction by inductive dffects. However, several literature“!36 reports indicate that inductive effects result in only a 1.2 to 1.8 fold greater reactivity for mesitylene relative to toluene in benzylic hydrogen abstraction. So such inductive effects can't alone explain the observation that 18 ct-mesitylacetophenone is nearly 7 times more reactive than a-(o—tolyl)acetophenone. COL. *— » 1.. LL syn anti K... Scheme 9 A interpretation of the results based on conformational restriction was thenprovided by the authors.35 It is assumed that there are two possible conformations for ot-(o-tolyl)acetophenone. Both of them have their Ca-Ar bond eclipsing with the C=O bond. The tolyl group, however, can be Oriented with the o-methyl group either on the same side (syn conformer), or different side (anti conformer) with the carbonyl group, with the latter being favored (Scheme 9). 5-Hydrogen abstraction is not possible in the anti conformation, since the o-methyl group is not accessible to the carbonyl group. The ot-ring has to rotate to the less stable syn conformation in order for the reaction to occur. Symmetric 2,6-dimethyl substitution of the ot-phenyl group, as in ot-mesitylacetophenone, would eliminate the possibility of an anti conformer, leaving only the syn conformation (Scheme 9). Hence, the difference in the lifetimes for ot-mesitylacetophenone and 19 ct-(o-tolyl)acetophenone is partially due to the lack of any unreactive anti conformer for ot-mesitylacetophenone. Wagner and Meador37 have estimated the excited state conformational equilibrium constant for o-(benzyloxy)benzophenone, o-(benzyloxy)benzo- phenone which is known to produce the corresponding dihydrobenzo- furanol,38 presumably by cyclization of the 1,5-biradical formed by 6-hydrogen abstraction (Reaction 7). PhCHZO 0 ||\ Q. Ph 111’ Ph , ‘Ph OH Reaction 7 The excited ketone is believed to be able to achieve a dynamic conformational equilibrium before decaying (Scheme 10). There are two different rotamers for o-(benzyloxy)benzophenone, a syn rotamer, and an anti rotamer. 6-Hydrogen abstraction can only occur directly from the syn conformer. However, the anti rotamer can give rise to hydrogen abstraction by first rotating to the syn rotamer. In dibenzoyl ketone, there is always a carbonyl group near the benzyl C-H bonds no matter which way the alkoxy group is twisted. The 10 folds rate enhencement afforded by the extra benzoyl group suggests an equilibrium constant of 10 for rotation of the alkoxy group about the phenyl bond, with the unreactive anti rotamer favored in the monoketone. . In molecules where conformational changes are comparable or slower 20 PhCHz PhCHZ {1“ o o ——> Ph ‘ O ‘\ Ph anti syn Ph Scheme 10 than their photoreactions, either ground state control or rotational control may occur. PhCH2 PhCHZO L lol\ 0 0K g Ph Ph/ Ph 1'1x10‘7 1.8 20 Several benzoylcyclohexane derivatives have provided the most clear-cut examples of ground state control in photoreactions. Lewis39 has 21 investigated conformational effects in the photochemistry of l-methylcyclohexyl phenyl ketone and a number of substituted analogues H OvPh H 0v Ph H0 Ph hV COPh hv COPh - _, + PhCO Scheme 11 (scheme 11). Lewis found that for l-methylcyclohexylphenyl ketone, there exist two different ketone triplets each leading to different photoproducts. The ketone conformer with the benzoyl group in an axial position undergoes y-hydrogen abstraction followed by cyclization to the corresponding 6-hydroxy-1-methyl—6-phenylbicyclo-[3.1.ll-heptanes. The ketone conformer having the benzoyl group in an equatorial position can not undergo hydrogen abstraction since the carbonyl group is oriented away from those hydrogens. Instead, it undergoes acyl cleavage giving rise to benzaldehyde as well as other products expected from the benzoyl and 1-methylcyclohexyl radicals. Lewis has found that the ratio of the products from the two different 22 pathways is entirely dependent upon the ground state population of each ketone conformer. * 0 CH3 L CH3 OK CH2 OH R 111) [5) R >109 5'1 . R —’ a syn 1 ~107 S'l IOK OK R W 3 ———> CH3 CH3 anti Scheme 12 A well defined example of rotational control in a photochemical reaction is provided by the photoenolization of o-alkylphenyl ketones (Scheme 13.4042 This basic photochromic system remained mechanistically confusing until it was realized that two kinetically and conformationally distinct triplets are involved.43 Sensitization studies revealed that ketones such as o-methylacetophenone and o-methylbenzophenone produce two distinct triplets, one with a subnanosecond lifetime and another with a ~30 ns lifetime. Recent flash kinectic flash work has verified these conclusions.“ The two triplets correspond to syn and anti conformers, which is indicated by 23 the behavior of 8-methyl-1-tetralone. This ketone is locked into a syn conformation and displays only a nanosecond triplet. Rapid enolization occurs from the geometrically perfect syn conformer.The decay of a longer lived triplet corresponds to anti->syn rotation. * IO CH3 0 KR hv /b 2 ~16 eh Scheme 13 CH3 Another closely related photochemical system ‘ involves the photochemistry of 2,4,6-trialkylphenyl ketones (Scheme 13). The introduction of additional alkyl groups to the phenyl ring causes dramatic changes in the photohaviors of the ketones. In an extensive study of 2, 4,6-trialkylphenyl ketones, Matsuura45 observed that cyclobutenol formation was the prefered course of the reaction. They also deduced that dienols were first formed and then underwent ring closure to give cyclobutenols. 1 Wagner43 studied a group of 2,4,6—trimethylvalerophenone derivatives (Scheme 14). It was concluded that there are two kinetically distinct excited 3X106 s“1 24 * CH3 0 5x107 5'1 5 :IK/Y > >109 3‘1 CH2 OH Scheme 14 25 triplets, one with a twisted form with respect to the carbonyl and aromatic ring, the other with a planar form. The more twisted triplet can undergo type II hydrogen abstraction or rotate with a rate constant of 5x107 5‘1 to the more planar form, which can readily abstract an ortho-benzylic hydrogen. The long-lived triplet decays with a rate of 106-107 5‘1 but does not produce benzocyclobutenol. The short-lived triplet forms benzocyclobutenol with a rate constant of ~109 5‘1. Unusual 1,3-Aryl Migrations Hart‘1'6'47 has reported a novel 1,3-aryl migration reacrion with 1,2,2-trimesitylethanone and 2,2-dimesityl-1-phenylethanone (Reaction 8). Irradiation of the ketones afforded the corresponding aryl vinyl ethers. There was only one precedent of the reaction in literature, reported by Heine in the case of 1,2,2,2-tetraphenylethanone.48 No mechanistic detail was presented in these reports. K... W ' /—\ H Ar Mes Ar=Mes,Ph Reaction 8 The initial objective of our research started with the following question. There are at least three decay modes for excited 1,2,2-trimesitylethanone: 26 ot-cleavage,24 5-hydrogen abstraction to form the coressponding indanol,35 and y-hydrogen abstraction to give the cyclobutenol.43"1*S The last two reactions are known to have a rate constant of ~109 5'1. However, none of these reactions were observed. Instead the ketone underwent a 1,3-aryl migration. Why is it so? A similar question can also be applied to 2,2-dimesityl-1-phenylethanone. We envisioned that conformational factors must be responsible, since it was noted that all the ketones which undergo the 1,3-aryl migration are sterically congested. In addition, the examples of conformational effects on photochemistry in literature have shown that photoreactions can be very sensitive to conformational factors in certain systems. We investigated a series of ot-arylacetophenone derivatives with varying steric congestion. We found that these ketones represent a group of sterically rigid compounds. The bond rotations in the molecules are restricted. The molecules are locked into certain conformations on the time-scale of photoreactions. Only the reactions allowed by the conformation in which the molecules are set can occur. Therefore, the reactions have shown great individuality. The detail of the study will be discussed later. The results from ot-arylacetophenone system encouraged us to extend our studies further. We decided to extend our studies in two directions. First, we started to investigate microenvironmental effects on the photobehavior of the ketones. The photochemistry of organic molecules in organized assemblies are being studied with great interest in order to understand the features controlling the selectivity in the photoreactions brought by these media.49'52 These studies have paved the way to an intriguing number of possibilities by which photoreactivities can be modified. Second, we increased the number of methylene groups between the carbonyl group and aryl 27 groups. We studied several p-arylpropiophenones to investigate the possibility of long-range c-hydrogen abstraction competing with a fast charge transfer quenching process of the excited ketones by the p-aryl groups. Photoreactions in Organized Assemblies such as Solid State and Cyclodextrin complexes. Many unimolecular organic photorearrangements take place by mechanism requiring drastic conformational or configurational changes along the reaction coordinate. Equally obvious is the idea that physical restraints on a given set of atomic and molecular motions can prevent these motions and lead to alternative pathways. Crystal lattice provides an excellent physical restraint. HO Solid State 8 ——> ‘ H O hv O 3 O H- OH / Solution OH Reaction 9 Sheffer has reported a dramatic change of photoreactivity of 4a,5,8,8a-tetrahydro-6,7-dimethyl-1-naphthoquin-4~ol going from solution to 28 solid state. Direct or benzophenone sensitized irradiation of benzene solution of the tetrahydronaphthoquinol affords essentially quantitative yield of intramolecular [2+2] cycloaddition product.53 In contrast, irradiation of the substrate in solid state gives no cage product. Irradiation of polycrystalline samples (powder) of the starting compound gives high yield of the keto alcohol (Reaction 9).54 X-ray crystallography provided the conformation of the tetrahydronaphthoquinol in solid state, which can be described as consisting of a half-chair cyclohexene ring cis fused to a second half-chair-like cyclohexenone moiety. The inmobility of the molecule in solid state prevents H I ‘ hv [2+2] ——> -——-> O Cycloaddition O Scheme 15 it from getting to the geometry for [2 +2] cycloaddition, therefore no cage product is formed. On the other hand, the formation of the keto alcohol, a reaction requiring less molecular motions, can be achieved by a C-5 to C-3 29 R3 OH — O OH — + [—- / R1 R1 N\ R P2 OH I O 2 N JY \. .. R1 O @333 O | J N\RZ hV CH2 R3 R1 I OH O )H ”\. 2 R1 ( R3 R3 Scheme 16 30 allylic hydrogen transfer and subsequent C-2 to C-5 bonding in the intermediate so produced (Scheme 15). Aoyamass‘56 reported a very interesting solid phase study of intramolecular type 11 hydrogen abstraction in the N ,N -dialkyl-ot-oxoamide system. The samples were irradiated in solutions and solid state respectively. Product P3 is the major product in solution, but the minor product in solid phase. Product P1 and P2 (type II products) are the minor products in solution, but the major products in solid state. The authors proposed that product P3 is formed through a 1,4—hydrogen shift in the initially formed . '0“? 0H (inns R: I a N Rotate CO-COH N ‘ . r» \ R1 '/ \Ra E). ; R2 3 H - .. 'Ci-IR3 i1 | b N / ' 0/ \R2 01-] Scheme 17 l,4~biradical, followed by a cyclization and ketonization (Scheme 16). This process involves considerably more molecular motions of the 1,4-biradical intermediate than does formation of P1 and P2. The 1,4-hydrogen migration is constrained to a planar or nearly planar cisoid transition state (scheme 17),57 which requires the rotation of the C(OH)-CO bond of the initially 31 formed 1,4-biradical since y-hydrogen abstraction in the starting oxoamides leads to a transoid biradical. Such molecular motions are possible in solution but prevented by crystal lattice restraints in solid state. Scheffer58 has studied the solid photochemistry of a group of ot-cycloalkyl-p-chloroacetophenones (Figure 3). All of these compounds undergo smooth type II reaction in crystalline phase.Analyses of geometric parameters from X-ray crystallography and photochemical results lead to the following conclusions. 1) A chair-like six atom ground state geometry is not a necessary requirement for the type H reaction. 2) Abstraction can occur over distances substantially longer than the previously supposed lirnitations.59"60 3) There is no strict requirement that the hydrogen undergoing abstraction be in the plane of the carbonyl n-orbital. IV. ./G/ R = cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, exo-2-norbony1, 1-adamantyl Figure 3 Another specific subarea of photochemistry in organized assemblies concerns reactivity of molecules incorporated in "host-guest" compounds.61 Cyclodextrins, one of the most commonly used"host" systems, possess hydrophobic cavities that are able to include in aqueous solution a variety of 32 0 Type I + .Ik Ph 0 OR K .s Ph .. i .. O ' P T I ype I h Ph R = methyl, ethyl, isopropyl OR > PhCOCOPh + Ph I : Ph + PhCI-IO OR y OH O b O\/IK + 0 Ph Ph Ph Scheme 18 33 organic compounds. Although the potential of cyclodextrins as "reaction vessels" for thermal reactions has been widely acknowledged, their use in photochemical reactions is yet to be fully explored. One of the most dramatic alteration of photobehavior from solutions to cyclodextrin complexes has been reported by Ramamurthy.62 The authors studied the photochemistry of several benzoin alkyl ethers. It was found that the type II process which is absent in benzene and methanol occurs in competition with the type I process in aqueous cyclodextrin complex solutions (Scheme 18). Most importantly, the photolysis of solid cyclodextrin complexes results in the type II products near quantitative yields. A B V v Type I and Type II Products Type I Products Scheme 19 Complexes A and B (Scheme 19) are two representative possible Structures of the benzoin alkyl ethers in cyclodextrin. While complex A can 34 give both type I and type II reactions, complex B can undergo only type I reaction. The enhancement of type II products can be due to either the suppression of type‘I reaction by the increased cage effect in cyclodextrin complexes, which reduces the possibility of paired radicals to escape out of the cage and enhance the number of molecules to recombine to the ground state starting ketones,63'64 or the increased possibility for conformation A in cyclodextrin complexes. Charge Transfer Quenching of Excited Ketones by Aromatic Compounds rm . _, 070K. \ \ 5+ V L\\ Photoproducts Ph Scheme 20 The ability of aromatic rings to deactivate n,11" carbonyl triplet has been recognized for a number of years. Wagner65 showed some years ago that even weak electron donors like alkylbenzenes reduce highly electron 35 deficient ketones by a charge transfer mechanism. This charge transfer quenching process occurs most efficiently when it happens intramolecularly and the aromatic ring is two carbons away from the carbonyl group, such as in p—arylpropiophenones. In 1970, three independent reports by Wagner,66 Stermitz,67 and Whitten,68 clearly illustrated the effect. It was found that p-phenylpropiophenone derivatives undergo type II reaction or photoreduction with significantly lower quantum yields and much shorter lifetimes than those for the analogous ketones without p-phenyl group. It was concluded that the n,11" triplets undergo a very rapid irreversible intramolecular quenching process which specifically requires a p-phenyl ring. This process is now generally considered as a charge transfer quenching involving nonemitting exciplex intermediates (Scheme 20). Scaiano69 recently published a detailed. flash photolysis study of the photochemistry of p-arylpropiophenones. The results indicate that the triplet lifetimes of various ketones are rather insensitive to substituent effects on the p-aryl rings, all of the order of 109 5'1. Scaiano suggested that the rate of the intramolecular quenching is mainly controlled by the ability of the substrate to achieve a critical conformation required for the interaction. Therefore, it does not vary with the electron donating ability of the p-rings. This process resembles a diffusion controlled intermolecular quenching process where the rate depends on how fast the molecules can get close to each other. Since a great deal of the work presented in this thesis deals with conformational analysis of the sterically congested ketones. A introduction of two most frequently used tools is given briefly. Dynamic NMR Studies 36 Dynamic NMR (DNMR) studies the effects of chemical exchange processes on NMR spectra, and is used to provide information about changes in the environment of magnetic nuclei. DNMR spectra may be interpreted to give information not only on structures of conformations but also on energy differences between conformers and on energy barriers.7O Conformational energy differences can be determined by measuring the relative populations of various conformers at a single temperature. Use of Boltaman equation then leads to the energy differences between the conformers. Determination of barrier height requires comparasion of NMR spectra at several temperatures. As the temperature changes, the rate of interconversion changes. At low temperature, the rate of rotation may be slow enough that signals of a proton in different enviroments can be separated in its NMR spectrum. At high temperature, interconversion may become so rapid that a single proton moves back and forth between different enviroments within the time required for the NMR measurements. The resulting spectrum often becomes simpler since the separate chemical shift peaks for a proton in different conformations merge into a single peak representive of the averaged environments At intermediate exchange, two peaks merge into one peak and strong broadening is observed. If the nuclei are protons and the two sites are equally populated, the rotational rate can be derived with equation (2),71 where w is the Iinewidth at the halfheight of the signal in Hz, Av is the difference of chemical shifts in different environments in Hz. k ={111.\.12[(Av/=isckrTP (4) 1/1 = kr + kd (5) where ‘bisc is the intersystem crossing quantum yield, k, is the rate constant for the reaction, kd is the rate constant for triplet decay other than the interested reaction, 1 is the triplet lifetime, and P is the probability that the intermediate will go on to the products. In the presence of an external quencher, (5) becomes 1/T=kr+kd+quQI (6) 39 where kq is the bimolecular quenching rate constant. A mathematical relationship, referred to as the Stern-Volmer equation, can be derived between the ratio of'photoproduct in the absence and presence of quencher and the concentration of quencher used, °/ = 1 + kq‘tlQ] (7) Thus a plot of °/ versus [Q] should give a straight line with an intercept of 1.0 and a slope of qu. In most cases, the rate of energy transfer quenching by dienes or naphthalene is close to the rate of diffusion in a given solvent. For example, kq is known to eaual to 5-6x109M"ls"1 in benzene at room temperatures“!89 Therefore, the triplet lifetime can be calculated from the slope of the Stern-Volmer plot. In this thesis, the photochemistry of ot-arylacetophenone derivatives will be presented, along with the preliminary results concerning the phtoreactivities of these ketones in organized assemblies and the photochemistry of several p-arylpropiophenone derivatives. Results 1. ot-Arylacetophenone Derivatives A. Photoreactions in Solutions 1. General Preparations of the Ketones ot-(o-Tolyl)propiophenone, ct-(o-tolyl)valerophenone and ot-(o-tolyl)- isobutyrophenone were prepared by alkylation of ct-(o-tolyl)acetophenone with methyl iodide, or propyl bromide. ot-Mesitylpropiophenone, ot-mesitylvalerophenone, ot-mesitylisobutyrophenone, and ot-mesityl-o- methylacetophenone were prepared by the reaction of corresponding nitriles with aryl magnesium bromide. ot-Mesityl-2,4,6-trimethylacetophenone, ot-mesityl-ot-phenyl-p-methoxyacetophenone, ot-mesityl-ot-phenyl-2,4,6- trimethylacetophenone ot-phenyI-2,4,6-trimethylacetophenone, and ot-(o-tolyI)-p-methoxyacetophenone were synthesized by Friedel-Crafts acylation with corresponding acetyl chloride and aromatic substrates. ot-Mesityl-ot-phenylacetophenone and ot-mesityI-ot-phenyl-p-cyanoaceto- phenone were prepared by Friedel-Crafts alkylation of mesitylene with or ~chloro-ot -phenylacetophenone and ot ~chloro-ot -phenyl-p-cyanoaceto- phenone. 2. Identification of Photoproducts Irradiation of approximately 0.3 g of ot-arylacetophenone derivatives in 500 ml cyclohexane or benzene with a Pyrex filter afforded a mixture of R1 R0 0 hi) _.__. . 'K KAr Ar R2 R3 R4 R2 R3 R4 R1 OH R3V0Mes + + R2 R3R4 1 R0=CH3, R1=R2=R3=R4=H, Ar=p-MeOPh, on-(o-Tolyl)-p-Methoxyacetophenone 2 R0=R4=CH3, R1=R2=R3=H, Ar=Ph, ot-(o-Tolyl)propiophenone 2-d R0=R4=CH3, R1=R2=H, R3=D, Ar=Ph, a~(o-Tolyl)propiophenone-d1 3 R0=CH3, R1=R2=R3=H, R4=(CH2)2CH3, Ar=Ph, ct-(o-Tolyl)valerophenone 4 R0=R3=R4=CH3, R1=R2=H, Ar=Ph, ot-(o-Tolyl)isobutyrophenone S R0=R1=R2=R3=CH3, R4=H, Ar=Ph, ot-Mesitylpropiophenone 6 =R1=R2=CH3, R3=H, R4=(CH2)2CH3, Ar=Ph, ct-Mesitylvalerophenone 7 R0=R1=R2=R3=R4=CH3, Ar=Ph, ot-Mesitylisobutyrophenone 8 R0=R1=R2=CH3, R3=H, R4=Ph, Ar=Ph, on-Mesityl-ot-Phenylacet0phenone 8-d R0=R1=R2=CH3, R3=D, R4=Ph, Ar=Ph, ot-Mesityl-ot-Phenylacetophenone-dl 9 R0=R1=R2=CH3, R3=H, R4=Ph, Ar=p-Ch3OPh, a-Mesityl-ot-Phenyl-p-Methoxyacetophenone 10 ll 13 14 15 16 42 R0=R1=R2=CH3, R3=H, R4=Ph, Ar=p-CNPh, ot-Mesityl-ot-Phenyl-p-Cyanoacetophenone RO=R1=R2=CH3, R3=H, R4=Ph, Ar=Mesityl, ot-Mesityl-on-Phenyl-2,4,6-Trimethylacetophenone R0=R1 =R2=R3=R4=H, Ar=MesityI, at-Phenyl-2,4,6-Trimethylacetophenone R0=R1=R2=CH3, R3=R4=H, Ar=o-Tolyl, ct-Mesityl-o-Methylacetophenone R0=R1=R2=CH3, R3=R4=H, Ar=Mesit-yl, ot-Mesityl-2,4,6-Trimethylacetophenone . Ros-CH3, R1=R2=R3=R4=H, Ar=Ph, ot-(o-Tolyl)acetophenone R0=R1=R2=CH3, R3=R4=H, Ar=Ph, ot-Mesitylacetophenone 16-d R0=R1=R2=CH3, R3=R4=D, Ar=Ph, ot-Mesitylacetophenone-dz 17 R0=R1=R2=CH(CH3)2, R3=R4=H, Ar=Ph, ot-(2,4,6-Triisopropylphenyl)acetophenone 17-d RO=R1=R2=CH(CH3)2, R3=R4=D, Ar=Ph, ct-(2,4,6—Triisopropylphenyl)acetophenone-d2 Reaction 10 43 ot-cleavage products, type II products, corresponding 2-phenyl-2-indanols, and aryl vinyl ethers in the cases of several ot-mesitylacetophenones (Reaction 10). The products were normally isolated by GC. Preparative tlc plates were used for isolations of products from ot-mesityl-ot-phenylacetophenone 8, ot-mesityl-ot-phenyl-p-methoxyacetophenone 9, and ot-mesityl-ot-phenyl-p- cyanoacetophenone 10, using a mixture of hexane and ethyl acetate as eluent. The photoreactivities of the ketones showed an unsually sensitive substituent effect. Irradiation of ketone 5, 6, 8, 9 and 10 led to the formation of type I products, indanols, and aryl vinyl ethers, while type I reaction was the only reaction observed for ketones 4, 7, 12 and 14. Although type II products were the major products formed from 3, ketone 6 only gave trace amount of type 11 products. Structural assignments of the photoproducts were based on spectral data (1H and 13C NMR, IR, UV, and MS). The characteristic feature of the indanol derivatives is an AB quartet appearing between 3.0 ppm and 4.0 ppm in 1H NMR, which corresponds to the methylene portion of the five~member ring. , OK hv Ph 4 . Reaction 1 1 ot-Mesitylpropiophenone 4 gave a mixture of stereoisomeric indanols, with a Z/E ratio of 5.1/1 in cyclohexane by GC (Reacton 11). 1H NMR was 44 used to assign the stereochemistry of the diastereomers. Oi? 1::3 5CH3 0.74 ppm 1.37 ppm Figure 4 P a p p a s 7 4 has reported that the diastereomer of 2-methyl-3-phenyl—2,3-dihydrobenzofuran in which the phenyl and methyl substituents are cis to each other has a methyl signal at 0.74 ppm. The methyl group in the the trans isomer appears at 1.37 ppm (Figure 4). Lewis75 observed the same effect for the two diastereomers of 2-methyl-1-phenylcyclobutanols (Figure 5). Wagner76a has found that the same was true with the t-butyl groups of Z/ E 2-t-butyl-1~phenylcyclobutanols HO H H0 CH3 ph Ph CH 3 H 5 CH3 0.60 ppm 1.10 ppm Figure 5 (Figure 6). The three methyl groups of the t-butyl group in the E isomer absorb 0.45 ppm more upfield than the ones of the Z isomer. Wagner and 45 HO HO H C(CH3) 3 Ph Ph C(CH3)3 H 5(CH3)3 0.50 ppm 0.95 ppm Figure6 Meador76b reported that a similar effect was also observed with stereoisomeric 3-hydroxy-3-methyl-2-phenyl-2,3-dihydrobenzofurans. The methyl group of E-3-hydroxy—3-methyl-Z-phenyl-2,3-dihydrobenzofuran absorbs upfield of the methyl group of the Z isomer (Figure 7). Thus the stereochemical assignments of the indanol products from ot-mesitylpropiophenone 5 were based upon these considerations. 50%;, 1.11 ppm 1.70 ppm Figure 7 When the methyl group of 3,4,6-trirnethyl-2-phenyl-2-indanol is cis to the phenyl group, it appears upfield of the methyl group in the trans form, because it is in the shielding cone of the benzene ring. Therefore, the isomer 46 with its methyl group at 1.32 ppm is assigned as the 2 form; the one with the methyl group at 0.75 ppm as the E isomer (Figure 8). ot-(o-Tolyl)propiophenone 2, ot-mesitylvalerophonene 6, and at-mesityl-ot-phenylacetophenone 8 all afforded only one of the possible isomeric indanols. The sructural assignment is made difficult by the fact that there is no comparison like what there is with two isomers. However there are indications that all of these indanols are the Z isomers, where the ot-substituent is cis to the hydroxyl group. The methyl group of the indanol from o-(o-tolyl)propiophenone 2 absorbs at 1.26 ppm, very close to the methyl group of Z-3,4,6-trimethyl-2-phenyl-2-indanol, indicating a Z structrue. SCH3 1.32 ppm 0.75 ppm Figure 8 A Z structure is assigned to 4,6-dimethyl-2-phenyl-3-propyl-2-indanol from ot-mesitylvalerophonene 6, based upon the consideration that the chemical shifts of the diastereOmeric methylene protons (1.64—1.98 ppm) are too downfield to be the one of the E form. The increment in ppm of a proton signal changing from a methyl group to a methylene group is approximately 0.25. The adjustment of the methyl signal of E-3,4,6-trimethyl-2-phenyl- 2-indanol by 0.25 ppm gives a chemical shift of 1.0 ppm, while the same adjustment made for Z-3,4,6—trimethyl-2-phenyl-2—indanol gives a chemical 47 shift 1.57 ppm. The chemical shift of the Ciz protons of 4,6-dimethyI-2-phenyl-3-propyl-2-indanol appears in better agreement with a Z assignment (Figure 9). Scaz 1.64 - 1.98 ppm Figure 9 Figure 10 A simple inspection of a model shows that the steric congestion between the two phenyl groups in cis-4,6-dimethyI-2,3-diphenyl-2-indanol requires them to face each other (Figure 10). This will make the phenyl proton NMR signals appear relatively upfield. Farnia and Knorr77'78 have shown that the aromatic signals of several 2,3-diphenylindans are as far upfield as 6.30 ppm when the phenyl groups are cis to each other. The fact that the two phenyl groups of 4,6-dimethyl-2 3odiphenyl-2-indanol have 48 signals ranging from 7.00 to 7.43 ppm suggests that the trans (E) isomer was formed. P h OMe s H OMe s V \_/ I-i/—\Ph Ph/—\ Ph 5CH3 5.97 ppm 5.43 ppm Figure 11 The vinyl protons of the enol ethers absorb between 5.0 ppm and 6.0 ppm in most of the cases. The Z and E form of the ethers are assigned, assuming that the vinyl proton of the Z form would shift downfield from the one of the E form due to the deshielding by the phenyl group.46 For instance, the vinyl proton of 5.97 ppm is assigned to Z-1-mesitoxy-1,2- diphenylethylene, and the vinyl proton of 5.43 ppm is assigned to D R o + K Ph Rab E-1-mesitoxy-1,2-diphenylethylene (Figure 11). Reaction 12 49 N iconoAQBmoaA—encezmEmoaofltheevtuv-6 Soc 84%va conges— wo 558% £22 63.8.39 NH saw.— tx/Kfi Sam and Enn— Ed 5mm 96 ococonmozooflEcosmimoumoflt Etc. 16-6 :5: 82me coco—8% mo 83:“.on M22 I~ .2 2:9..— Z a. 3.. 3. 3.. LL 3w Su 5‘ S _ _ — . . p u _ .—, . p . —r . .u p . p p p, . p. — F .p p. r - pt u- p . rt F1 .IPLi» .p-,.Pt P. FIP — Lir —, PIP P.h.l-rlht t—irlbtir bltptL rib. r— r hr». u .- Elvirthll— <1 11 1 1. 1 s. - .. lijxlllltlllll .1llttl11l/I\ [it - (is! l 51 The following deuterium exchange experiments were conducted in order to confirm the machanism proposed by Wagner79 for the photoenolization of ot-(2,4,6-triisopropylphenyl)acetophenone and ot-mesityl- acetophenone. All the samples were degassed by bubbling through Argon gas prior to irradiation. ot-(2,4,6-Triisopropylphenyl)acetophenone-d2 17-d was irradiated in carbon tetrachloride in a pyrex NMR tube at 365 run until the the relative amount of the indanol formed to the remained ketone was 35% (by the area ratio of one of methyl signals (0.78 ppm) at C1 of the indanol to the ortho proton signal of the benzoyl group in the starting ketone in NMR). 1H NMR of the irradiated sample showed the appearance of the ot-methylene protons at 4.46 ppm in the unreacted ketone. The relative area ratio of the ot-methylene peak to the benzoyl ortho proton peaks in the unreacted ketone was 0.11 by integration. This indicated that ~22% of the unreacted ketone underwent deuterium exchange. 2H NMR of a separately irradiated sample showed deuterium migration from the ot-carbon to the benzylic carbon (Figure 12). The ot-methylene deuterium signal in the remained starting ketone was identified by its position away from CDC13 signal in a separate sample with added CDCI3. This peak was then zeroed at 4.45 ppm. Due to the similarity of the chemical shifts in 1H and 2H NMR, the deuterium absorptions at 3.81 ppm and 2.82 ppm thus coresspond to the methylene deuteriums in the indanol and the benzylic deuteriums in the ketone respectively. The benzylic deuterium signal of the ketone at 2.82 ppm overlaps with one of the ot-methylene deuteriums which should be around 3.08 ppm. Similar experiments were performed on oi-(o-tolyl)propiophenone-d1 2-d, ot-mesitylacetophenone-dz 16-d, and ot-mesityl-ot-phenylaceto- 52 phenone-d1 8-d. The deuterated ketones dissolved in carbon tetrachloride or benzene-d6 in a pyrex NMR tube were irradiated at 365 nm. The irradiation time was controlled -so that the the relative amount of the indanol formed to the remained ketone was 20% for ot-(o—tolyl)propiophenone-d1 2-d (by the area ratio of ot-methyl signal in the product and unreacted ketone), 35% for ot-mesitylacetophenone-dz 16-d (by the area ratio of mesityl methyl signal in the product and unreacted ketone), 25% for ot-mesityl-ot-phenylaceto- phenone-d1 8-d (by the area ratio of mesityl methyl signal in the product and unreacted ketone). 1H NMR showed no appearance of the ot-methylene proton signal at 4.30 ppm for ot-mesitylacetophenone, or the ot-methine proton signals at 4.26 ppm and 5.99 ppm for ot-(o-tolyl)propiophenone 2 and ot-mesityl-ot-phenylacetophenone 8, respectively. or-(2,4,6-Triisopropylphenyl)acetophenone 17 was irradiated in benzene-d6 in a Pyrex NMR tube at 365 run until the relative amount of the indanol formed to the remained ketone was 80% (by the area ratio of one of methyl signals (0.78 ppm) at C1 of the indanol to the ot-methylene proton signal of the starting ketone in NMR). A peak was observed at 6.13 ppm in the 1H NMR spectrum of the reaction mixture (Figure 13). It did not disappear after 20 hr. standing at room temperature. But with a drop of acetic acid, it slowly disappeared over a period of 3 days. It was found later that this peak disappeared over 3 days even without adding acetic acid. This signal is assigned to the vinyl proton of the Z enol of the ketone.79 The signal for the E enol as reported by Wagner was not observed. The area ratio of the the vinyl proton signal to the methyl signal (0.78 ppm) at C1 of the indanol is 1/ 2.9, indicating a ratio of 1 for the enol and indanol. 53 3. Kinetic Data The initial ketone concentrations for all the measurements were 0.025-0.06 M. The ketone conversion was normally controlled at 7%-12%. In the cases of ot-mesityl-ot-phenylacetophenone 8, ot-mesityl-ot-phenyl-p- methoxyacetophenone 9, ot-mesityl-ot-phenyl-p-cyanoacetophenone 10, and ot-(2,4,6-triisopropyl)acetophenone, samples were analysized with lower ketone conversion, i.e. 4%-7%. Benzaldehyde formation was quenched with naphthalene in benzene with ca. 0.07 M dodecanthiol at 365 nm for ot-(o-tolyl)propiophenone 2, ot-(o-tolyl)isobutyrophenone 4, and ot-mesityl- isobutyrophenone 7. ot-(o-Tolyl)acetophenone was quenched with 2,5-dimethyl-2,4-hexadiene in benzene at 313 nm for ot-(o-tolyl)valero- phenone 3. Indanol formation was quenched with naphthalene in benzene at 365 nm for ot-mesitylpropiophenone 5, ot-mesitylvalerophenone 6, and ot-mesityl-o-methylacetophenone 13, with 2,5-dimethyl-2,4-hexadiene in benzene at 313 nm for ot-(o-tolyl)-p-methoxyacetophenone 1. Both indanol and enol ethers were quenched with 2,5-dimethyl-2,4-hexadiene in benzene at 365 nm for ot-mesityl-ot-phenylacetophenone 8 and ot-mesityI-ot- phenyl-p-methoxyacetophenone 9, with the exception that the enol ethers from o-mesityl-ot-phenylacetophenone 8 was quenched in hexane. Enol ethers were quenched with 2,5-dimethyl-2,4-hexadiene in benzene at 365 nm for ot-mesityl-ot-phenyl-p-cyanoacetophenone 10. Mesitaldehyde was quenched with 2,5-dimethyl-2,4—hexadiene in benzene with ca. 0.07 M dodecanthiol at 313 nm for or-mesity1-2,4,6-trimethylacetophenone 14, ot-mesityl-ot-phenyl-2,4,6-trimethylacetophenone 11, and ot-phenyI-2,4,6- trimethylacetophenone 12. The suspected type H cyclization products could not be separated from Table l. Lifetimesa of o-Arylacetophenones Ketones #1331: It'lxlO'9 1 2900b 0.0017 2 97.8 (10)f 0.051 3 27.7 (1.1)8 0.18 4 121 (16)f 0.041 5 17.2 (1.5)C 0.29 6 A curved Stern-Volmer plot was obstained 7 7.28 (1.3)f . 0.69 8 0.94 (0.04)C, 0.79‘2 5.3 9 46.9 (1.0)C, 41.8 (1.7)91 0.11 10 1.18d 3.2 11 0.62 (0.2)f 8.1 12 3.80 (0.7)f 1.38 13 1.87 (1.0)b 2.7 1L 6.88 (0.8)f 0.73 a. Measured in benzene at 313 nm unless otherwise stated, with ketlone conversions of 4-7% for 8, 9, 10 and 7-12% for the others. it = 5x109 5' is used. Precisions of repeated measurements in parentheseg. b. Quenchin indanol. c. Quenching indanol at 365 nm. d. Quenchin enol ethers at 36% nm. e. Quenching enol ethers in hexane at 365 nm. f. enchin aldehyde formation in the presence of 0.007 M dodecanthiol. g. Quenching type II cleavage product. 55 Table 2. Quantum Yields of Photoproducts from o-Arylacetophenones Ketones mawb QQC owl benzene polar solvent benzene mlar solvent _1 0.54 0.021,e _2 0.28 0.048 0.018f0.0158 _.2:cL 0.044 0.06 (0.02)1m 3 0.03 0.201013)m 0.014J __4 0.38 0.55,h 0.010,h 5 0.017 0.24 074.510.681' 0.0; 0007730012] 0.37,h 0.0051,h 6 0.0063 0.12 0.7(Li0.78i 0.0038 0.0047.i0.00531’ z 0.31 0.033,h 0.020h 8 0.0038 0.020 0.069.i 0.0491' 0.025 0.1m} 0.021 _§;d 0.018 0.02; L 0.005; 0.024 0.0411‘ 0.0084 0.00121‘ 10 0.0058 0.0077 0.0121‘ 0.0046 0.0049h 11 0.33 __12 0.016 13 0.029 0.035 0.04_9.f0.0511< 14 0.35 _16 0.44 0.48,i0.541 163d 0.43 Table 2 (cont'd) 12 023 0.0161‘ _1z;1 0.38 0.sz a. Aldehyde in 0.007 M dodecanthiol. b. T e II cleavage roduct. c. Indanol. d. Enol ethers. e. Acetonitrile with 2% >320. f. t-Buty alcohol. If 0.5 M yridine in benzene. h. 2 M dioxane in benzene. i. Acetonitrile. j.‘ ethanol. . Dioxane. l. 1 M yridine in benzene. m. Quantum yields for a mixture of two suspected cyc obutanols in parentheses. n. Measured at 365 nm with ketone conversions of 4-7% for ketones 8, 9, 10, 15, IS-d and at 313 nm with ketone conversions of 7-12% for the others. 57 each other by GC. The 1H NMR of the mixture (possibly with other impurities) was two complex to be resolved. However the pattern of the spectrum and the solvent effect in the quantum yield indicate the identity of the cyclobutanols. The riplet lifetimes and photoproduct quantum yields of the ketones were measured and are given in Table 1 and Table 2. Flash photolysis of on-mesityl-a-phenyl-p-methoxyacetophenone 9 indicated a triplet lifetime of 10.0 ns.80 Our quenching study provided a kq‘t value of 47. A kq value of 4.7x109 M'ls'1 is thus derived for this ketone. This verifies that energy transfer quenching in our system is still diffusion-controlled within experimental error. Therefore, a kq value of 5.0x109 M'1 s'1 is used to obtain the lifetimes of the ketones studied. A curved Stern-Volmer plot was obtained in the case of a-mesitylvalerophonene 6 (Figure 14). This usually indicates the existence of more than one excited state of which the rate of interconversion is comparable to the rates of excited state decay.81 It has been known that the radicals generated by Norrish type I cleavage exist in a solvent cage as radical pairs. The radical pair can either recombine to the starting ketone or diffuse apart. The free radicals can be trapped by added hydrogen donors, such as thiols.”):24 All the type I quantum yields in Table 1 were measured in the presence of approximately 0.07 M dodecanthiol or octadecanthiol. The dependence of the a—cleavage efficiency on the concentration of dodecanthiol for o-(o-tolyl)propiophenone 2 and a-(o-tolyl)isobutyrophenone 4 was given in Figure 15 and Figure 16. The plateau indicates 100% trapping of the out-cage radicals. The intersystem crossing quantum yield was measured for a-mesityl-cx-phenylacetophenone 8, and found to be ~1.0. The measurement Table 14. Stern-Volmer Plot for a-Mesitylvalerophenone 12 10 d>°/ 0 O 0.5 1.0 1.5 [Q] 59 Table 15. De dence of Benzaldehyde Formation from a- o-Tolyl)prop1ophenone on the Concentration of Dodecanthiol 0.4 0.3 0.2 a l 0.0 - 0.000 0.001 0.002 0.003 0.004 0.005 0.1 [RSI-I] Table 16. Dependence of Benzaldehyde Formation from 01- o- Tol l)isobu henone on the Concentr ti f Dodecanyt’hiol tyrop a on o 0.4 0.3 0.2 0.1 L 0.000 0.001 0.002 0.003 0.004 0.005 0.006 [RSH] 61 Figure 17. Plot of 1/ (bisom versus 1/ [cis-Stilbene] in Sensitized Isomerization of cis-Stilbene by o:-Mesityl-a-Phenylacetophenone 8 10 l/ l/[cis-Stilbene] 62 was conducted by using the ketone to sensitize the isomerization of cis-stilbene.97c The quantum efficiency of cis to trans isomerization of stilbene, ¢isoml is given by equation (8),81 <0 15m = 2.50 iscquSI/<1isc can be derived from the intercept, 1/ (bisom = 2-5¢isc(1 4' kdt/quSD (9) Benzene solutions of 0.04 M o:~mesityl-a-phenylacetophenone 8 with varing cis-stiblene concentrations were irradiated at 365 nm. The quantum yields of trans-stiblene formation were measured. Reciprocal ¢isom values were plotted versus recipocal cis-stilbene concentrations (Figure 17). An intercept of 1.86 was obtained, which corresponds to a ‘bisc of 1.31. The Z/ E ratios of the aryl vinyl ethers from a-mesityl-a-phenylaceto- phenone 8, o:-mesityl- 3.3 figs—gm mo 5:3qu “6098—95 .0 6:2 m \NIEozon 6280280 :33 cos—65:00:00 0:206. fiumfitmoh .n .* 0:200. Gob E050 35> 1.81m >< u .6 0.23 3:: 3:: a m m><fi _ 0.2.328 $63de 8: N 33.... :23 SE6 8 m m>< a $8.823 $3.085 S N 923 oi? 338 a. m 05¢. a 662.22; 63583 N N .0E:_._£=:wm n:o_m..0>:ou 33 4:223:00 .19:qu «Slag 10:5 .6 860 EN .6 23. EN .6 6666. EN 8:69.83. 35> :2 a: mom .6 6863.866. 6566.8. 82:. 66% 8650 35> E6. 06 8:60 EN .6 85.6568 .n 636“. 64 absorbances of the aryl viny ethers at 365 nm. 4. Dynamic NMR Studies Dynamic proton NMR spectra (Figure 31-33) of a-(mtolylfisobutyro- phenone 4 showed broadening of the two cat-methyl group signals below 220 K, indicating that rotation is restrained along the C a-CO bond (Figure 18). They coalescenced at around 180 K, and separated at 1.52 ppm and 1.78 ppm at 170 K. 5 R=CI-I3, 6 R=CH3(CHZ)2, 8 R=Ph Figure 19 Restricted rotations around the bond between cut-carbon and mesityl group were observed with ot-mesitylpropiophenone 5, a-mesitylvalero- 65 phenone 6, and a-mesityl-a-phenylacetophenone 8 (Figure 19). The two o-methyl groups coalescenced at 240 K for 5, 260 K for 6, and 188 Figure 20 K for 8. The same two methyl groups of 5 appeared at 1.90 ppm and 2.59 ppm at 200 K, the ones of 6 at 2.01 ppm and 2.59 ppm at 230 K, and the ones of 8 at 1.96 ppm and 2.44 ppm at 170 K (Figure 34-42). a-Mesitylisobutyrophenone 7 showed restricted rotations along a-carbon and mesityl bond as well as Ca -CO bond (Figure 20). The coalescence temperatures of the two bond rotations are 200 K and 183 K respectively (Figure 43-46). Linewidth analyses of the broadened NMR signals using equation (2) afforded the rotational rate constants at various temperatures. Based on equation (10) and (11), values of lnl< are ploted against 1/ T. The activation k = A x Exp(-E/RT) (10) lnk=lnA-E/RT (11) energy E and the A factor are calculated from the intercept and slope of the plots withequation (12) and (13) The rate constant at 300K is calculated from Table 4. Kinetic Parameters of C Q-CO Bond Rotation for 01- (o—Tolyl)isobutyrophenone 4 1‘00 185 190 195 200 l<(s'1) 156 282 399 896 1/Tx103 5.41 5.26 5.13 5.00 lnk 5.05 5.64 5.99 6.63 E(Kcal[mole)=7.43x103 A=9.53x1010 l<(300K)=3.66x105_ 5 r r r . 0.0049 0.0051 0.0053 0.0055 l/T Figure 21. Plot of Ink vs. 1 / T for Ca -CO Bond Rotation 1n a-(o-Tolyl)isobutyrophenone 4 67 Table 5. Kinetic Parameters of C Q-Mes Bond Rotation for a-Mesitylpropiophenone 5 T(K) 250 260 270 280 290 k(s'1) 723 1170 2117 3770 6260 1/Tx103 4.00 3.85 3.70 3.57 3.45 Ink 6.58 7.06 7.66 6.23 8.74 Excal/mole)=7.89x103 A=5.31x109 k(3001<)=9.50x103_ 8.5 " lnk 7.5 ‘ 6.5 r r v I # 0.0034 0.0036 0.0038 0.0040 l/T Figure 2. Plot of Ink vs. 1 / T for Ca-Mes Bond Rotation in a-Msitylpropiophenone S Table 6. Kinetic Parameters of C Q-Mes Bond Rotation for o:— Mesitylvalerophenone 6 T(K) 280 290 300 310 320 k(s'1) 625 827 1400 2070 3090 Hum3 3.57 3.45 3.33 3.23 3.13 Ink 6.44 6.72 7.24 7.64 8.04 E(I _Ph K Ph —R3 0 R4 Rz 18 R1=R2=R3=R4=H, p-(o-tolyl)propiophenone 19 R1=R2=R3=H, R4=CH3, p-(o-tolyl)isobutyrophenone 20 R1=R2=CH3, R3=R4=H, p-mesitylpropiophenone 20-d R1=R2=CH3, R3=R4=D, p-mesitylpropiophenone—dz 21 R1=R2=R3=CH3, R4=H, p-mesitylisobutyrophenone 21-d R1=R2=R3=CH3, R4=D, p-mesitylisobutyrophenone-dl Reaction 16 Irradition of approximately 0.3 g of several p-arylpropiophenone derivatives in 500 ml cyclohexane or benzene through a Pyrex filter afforded the corresponding 1,2,3,4—tetrahydro-2-naphthols (Reaction 16). The chemical yields of the products range from 60% to 90%. The structural identification of the photoproducts are based upon their 1H NMR, 13C NMR, MS, and IR spectra. The detailed spectral information is presented in the experimental section. A common feature of 1H NMR of the products is an AB quartet appearing at 2.90-3.50 ppm, which represents the methylene group at 01. Although the irradiation of p-(o-tolyl)propiophenone 18 did lead to the formation of photoproducts, as detected by CC, the conversion is too low, even after weeks' irradiation, for the products to be isolated and identified. In the case of 1,2,3,4-tetrahydro-B-methyl-Z-phenyl-2-naphthol and dfific of iht meflr conc Q-me pnsu grou; ENOdL phenc 91 1,2,3,4—tetrahydro-3,S,7-trimethyl-Z-phenyl-Z-naphthol, either a z isomer or a E isomer can be formed. It has been reported that the methyl 1H NMR signal of Z-2-methyl-1—phenylcyclohexanol is upfield of the one of the E isomer, because it is shielded by the phenyl group, however the difference is only 0.10 ppm (Figure 30).87 The assignment of the stereochemistry of the naphthols is made difficult by lack of comparasion because only one isomer was formed in both of the cases. On the other hand, the difference of the axial and equatorial methyl signal in 2-methyl-l~phenylcyclohexanol is too small to draw any conclusion upon. However, Lewis 75 has shown that a-methylbutyrophenone gave only trans (Z) cyclobutanol upon irradiation, presumably, due to the less congested arrangement of the methyl and phenyl groups in the Z form. It therefore seems reasonable to assume that the products formed here are also the trans (2) products. OH OH CH3 H H CH3 SCH3 0.50 ppm 0.60 ppm Figure30 Irradiation of p-mesitylpropiophenone-dz 20-d and p-mesitylisobutyro- phenone-d1 21-d was conducted to test the hypothesis that the enols of the 92 Table 16. Triplet lifetimesa of p-arylpropiophenones in Benzene __Igetones kqlb gins) 1'1x10'8(sec'1L 18 6.8C 1.4 7.1 19 8.0 1.6 6.3 20 4.8( 4.3‘) 0.96(0.86C) 10.4(11.6C) JL S.5(0.5) 1.1 9.1 a. Measured at 313 nm. k =5x109 5'1 is used. b. Precisiorgpf re ated measuremets in pareng'leses. c. Measured by Scaiano wit flash photolysis. ketones could have been formed from the intermediate biradical. The ketone samples (0.30 g) in benzene (500 ml) and dioxane (500 ml) were irradiated in a preparative photolysis apparatus with a Pyrex filter until ~20% conversion, 1H NMR of the irradiated sample showed no appearance of the cat-protons of the ketones. Table 17. Quantum Yields of Tetrahydronaphthols Formation in Various Solvents Ketones Benzene Dioxanea Acetoni_trile Methanol 19 0.00020 0.00017 0.00014 0.00032 20 0.00023 0.00028 0.00027 0.0012 zo-dz 0.00020 0.00025 21 0.0022 0.0023 0.0015 0.012 21.-d 0.0019 0.0019 a. 2 M dioxane in benzene 93 8. Kinetic Data The formation of the tetrahydronaphthols is quenched by typical triplet quenchers such as 2,5-dimethyl-2,4-hexadiene. The triplet lifetimes were measured by Stern-Volmer quenching in benzene. The quantum yields of the photoproducts in various solvents were also measured. Both of the measurements were done at 313 nm. The results are listed in Table 16 and Table 17. C. MMPMI Calculations Table 18. Relative Energies of Different Conformations for p-Arylpropio- phenones Steric Energy Pi Resonance Energy Total Energy Letone Conformation (Kcal [ mole) (Kgl/ mole) CI9P-F.LPY\~.I>:FIHIPrtrlplgl-},¥l}ELLIEILFLLELE.1ttLEEIrEIFEL11P A: 98 n . Q ~ . t. b... ‘ ,>.,>.1P:>:&:\Plr>, L ,. 2:) w n ~ x 2: a e 26:262.:3692:6538 .6 $22 5 .mm eswa CL.— 2 n m n a. r n r n e n n n e u n u e p n 1;. ..r » \rlr g-..thLrLthlPlr)lLukFEgLiELEEEEEE1>l B 0 LL 99 6. oh .6 e 6:65:85369238.668 do ”:22 3 .8 “=sz ELL _ SN w~ s. .4. a... me am mm 3.. m... 2. mp as . p . b, h P piPlP —1P.bl.h -plh.,rb .- l- _ b! h LP P _ ,lPl h: rrhh .*lr\r;1lr PltP kip .P. .-Ly b: _ F ...P;,P p; htLléP P-.r_ {P y»: .-I.P--HI¥II,P .- Pl—znr ,5: - {11:52: 100 v— oom an m ococonmoaoagzmmfia no £22 I_ .3” 0.59m a. ... aw m~ a. m. a... :Lwr em mm an an o... n. a ... . . . . . .. . . h . .. s . H . P . . E c. . . s ‘ s x s .._ x . . .-l_.l.n.r.>;->s‘ 4121.73.92 Ptr pg. P5 . 5.; Pier?» _--.P1..u\.- » _.....-r F-r.~,- 9 ,5 . . -13.; tlil, iii 101 v— ovu .6 m ococonmoioaazmm—zd «o 522 1— .mm mama CLL s. w. a~ m~ an an n... nr an an e,u nu an w. an . ‘f P > 5 . ‘ P: .P tbf-\.| ‘ b .L. P . h P 5!.P i ‘1 P h. .b p E X A P. p.lhlr\>|\r\f_kr1‘1,>. rkr bl‘ \h Kn:..PlP.‘v Pv.> far; .bi b. 1?-C-—ll\fr b! 5.. > .hl P11? (\P..‘i..h..nz.fi .b, E . [1.11 |||| I I. 1.1!. 11. \ 102 _ s. 9V v. com 8 m mcozonmoaoufibfimvzé mo M22 I" .8 «5&5 ELL mm an m. e: .m.. am an au we a» An ea . P1... . ‘ . p L s. h P p l. . h .51.. . 1. . E- #1» p. u v 5. \Pi Pt pr..l>1-.p I\P1l~ll~. PLLlFi‘LlPLlLthrP sulL. ht >l*-¥._tPL.l? tut-[ht tillrrLlertlfiLan < J 1‘ t. 14 :1: l ‘tlll‘llt ill. 103 v. own .6 o mcocozmoSEZEGm—zé .6 M22 IF .mm «5&5 ELL 3. .,._ 2» wV 9. we a... m; 3.». am a... nu 3» n. . _ . . . . ‘ . . . 5‘ . .1. »1_ ,... . . _,.p .. .p; .; h b Pl... 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Q \| ___/ 106 M com 3 & «553286155?6-3.82-8 .6 M22 T: .3 «5&2 SN Sm 5r ELL 9m am a... an 1 p. -1.-1>.-;. 53?? .L Plr:hl P lPrPlL,— >1.Pib11[llbl-[.> hFEEELLIELIFEEE 1131! lo] . 1 111. 1 ullllt| lll1l'llrlllx . 1 ql‘lllll 107 M mm. .a a «555.2285Raga—18-338216 Mo M22 IF .3 «3&5 :1... a. m. s~ me. an mn e...m.. an mm an no op n5 3... — . b...— . _ bi», P-* ~11». p1 1P -1_ p1 F pr..- ‘ P .P. P11? _1..1»l11~(.rr—11P11F11Plrl—11P11Plrr1rhl{Plrlr—lLlLllPlLlLIrrEEhllrirtlhikrlb.1L1:P1_:51 Pltnllr1—1ltp1 1 1.1 1. 1.1 1. . ..l 1 1 . .1 1 3-131 1111 1.11,.I.-11l1 I 111111111l111111 . .lll..ll1|l- 111111.111! \llllll/ 11, 2. x, K... .. 1% /\- 1 \\ \ 108 v. on. .m a «so:«;mo.««£>:«.a-d13:82-6 Mo M2 2 .1: .me «..:&E :1... SN 8 H 95. 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L .p 1 . “Ibipi p11» — .- P11p11r _1>1 FtP .L1LIP111P11P bl—Lrlhl Pl»- _|1\r1r111r tbllblrtr- >11Pl1_11l£.1rlP111_1L11P|1P1Llh11rlrr.Lu L11>.1.P1Pl—|1P1L1 .P >11.‘l1~1 J . 7: 1 81-111111111111111111._ P.1......_1. . ....._ b... .— SN v. m: .m . «555.284.5982.:8216 .0 M22 I— .5. «5&2 m. c... m. r necLuem m u no an n. e. 1 8 W B .1P .. 1. 1..,l1._1 PI...‘ ..l1.1.-_1 P. p11... 1.,Ib11r1r r1.11_11lr 1....1..1..P .5 11P1 P111..1,Ll|b.lrtplr_.ttpll.llPltpLlel1£ll , x .1, . \ v. on. .a . «:o:«;mo§5n0m=b_m«218 Mo M22 IF .3 «5&E . c... e n q 9.. me am an am mm e an «e _ 9 N m S m 8 P m P .11..-. _-... p-.. 1? _l. 1— .1 h _ .11.- P r —1» ,.,1,..1.1,_1L r.F11Pl—11rr1rr_l.r:rlPL'—11L11rFIL11—E|Err1 _111.111P1E|Ll.111r.11_l1 . 1a , , 1- 5 1 :1<21. ._, 112 113 IL 1 L 1 1 1 L a L L 1 l 1 L L l I: V V V V r r '— T U r V r V V ' 380nm 530nm Figure 47. Phosphorescence Spectrum of d-Mesitylpropiophenone 5 at 77 K 114 L 1 L 1 1 n L n L r 1 1 n 1 1 I r t ‘7' v I I I I V V r v t t ' ‘ 380nm 530 nm Figure 48. Phosphorescence Spectrum of d-Mesitylvalerophenone 6 at 77 K L L l 1— 4 r r v ‘1' D p «I- II «1- - q- ‘11- ll: 380nm 530nm Figure 49. ghfisphorescence Spectrum of a-Mesitylisobutyrophenone 7 at 116 F' 1' ‘1- ‘1- ‘11 fit- '1- 11- ‘1' ‘1' 111- ‘1- ‘1- «11- Figure 50. Pho73phorescence Spectrum of a-Mesityl-cat-Phenylacetophenone 8 at K 117 /\J A l l L l U r l T : lr V 1r 5 If f‘ 3r : 1 g g I I i— . j 370 nm 530 nm Figure 51. Phosphorescence Spectrum of a-Mesityl-a-Phenyl-2,4,6- A Trimethylacetophenone 11 at 77 K 118 L 1 1 1 1 1 1_ L 1 1 1 1 1 I [—— I V V V ‘ V I r V t r f V I 370 nm 500 nm Figure 52. Phosphorescence 153mm of c:-Mesityl-2,4,6-Trimethylaceto— phenone 14 at 77 119 L 1 1 1_ 1 1 L 1_ 1_ L 1 L 1 1 L l '— ' v V I U I r r V r’ v ' r I 380 nm 530 nm Figure 53 Phosphorescence Spectrum of p-Mesitylisobutyrophenone 21 at 77K 120 Discussion 1. a-Arylacetophenone Derivatives A. Photochemistry in Solution 1. Triplet Lifetimes and Reaction Rates The Triplet lifetimes of the ketones can be calculated from the following equafion: ‘t = Slope/kq (15) However, a limitation of Stern-Volmer method is that it requires reliable kq values. It is obvious that the chosen kq values are of great importance in the accurate determination of triplet lifetimes from the above equafion. It is widely accepted that the rate constant for the quenching of triplets by energy transfer in benzene at 25°C is 5.0-6.0x109 Ml’s"l,3 about half of the diffusion-controlled limit. Scaiano89 has undertaken a rather extensive study of the energy transfer quenching of various organic molecules with a number of triplet quenchers and has found this value to be accurate. Although it is generally true that energy transfer quenching of organic molecules is diffusion-controlled, steric hindrance is expected to reduce the rate constant for energy transfer for some extremely congested molecules. Scaiano and Wagner89 have measured the kq values by nanosecond laser flash spectroscopy for a number of o-alkoxyphenyl ketones, having o-alkoxy 121 substituents of various sizes. The results demonstrate that the energy transfer quenching is sensitive to the degree of steric congestion ortho to the carbonyl group. The most sterically crowded ketone in this study, 2,2-dibenzyloxybenzophenone, has a kq value of 8.4x108 M'ls’1 in benzene. Since our study involves sterically congested ketones, we were concerned about the possibility that the kq values for our compounds may be smaller than the ones under diffusion-controlled condition. A combination of Stern-Volmer quenching and flash photolysis studies of ot-mesityl-a-phenyl-p-methoxyacetophenone 9 provided a kq value of 4:.7x109 M'ls‘1 in benzene. This justifies that a kq value of 5.0x109 M'ls’l can be used to obtain the lifetimes of the ketones studied. Triplet lifetimes indicate how fast the excited triplet states can decay. Reciprocal triplet lifetimes are the sum of the rate constants of all the physical deactivations and chemical reactions that excited states undergo, i.e. 1/1 = 2191+ dei (16) Hence, in the case that there are more than one process involved, it is desirable to estimate all the individual contributions of each process to the overall triplet lifetime. Radiationless decay is a physical deactivation an excited molecule could undergo. Typical values for the rate constant, Rd, in phenyl ketones are on the order of 105-106 54.15 24b, ”'91 For instance, Lewis15 measured the kd's for acetophenone, propiophenone, and isobutyrophenoene. and found them to be 3.4x105 s'l, 3.2x]05 5'1, and 3.4x105 s:1 respectively. Lewis24b also reported that the ltd value for a-phenylacetophenone is smaller than 5x105 -1 s . 122 It seems unlikely that kd values for the q-arylacetophenone derivatives we studied would differ greatly from Lewis's values. There is no known reason why Rd values should be sensitive to the nature of the alkyl groups on the a-ring. Thus, radiationless decay accounts for less than 1% of the overall triplet decay of the ketones. For practical consideration, the contribution of radiationless decay to the lifetimes can be ignored. Radiative decay of triplet phenyl ketones (phosphorescence) normally takes place with a rate constant of ~103 s'l. It can by no means compete with the reactions of these'ketones. Three types of reactions were observed with the a-arylacetophenone derivatives, cat-cleavage, formation of indanol, and 1,3-aryl migration. Which reaction predominates depends on the natureof the substituents. Generally, a-dimethylation or 2,4,6ctrimethylation of on-arylacetophenones leads to exclusive cat-cleavage reactions. ct-Monosubstitution enhances the formation of 1,3-aryl shift products, and reduces the formation of indanols except for cx-mesitylpropiophenone 5 and ox-mesitylvalerophenone 6 in polar solvents. The quantum yields and rate constants for all the reactions are estimated and presented in Table 21. How these values are derived are described as follows for cat-cleavage and 6-hydrrogen abstraction. The evaluation of charge transfer rate constants will be discussed in the section for enol ethers formation. It has been well established that can-cleavage reactions involve the formation of caged radical pairs, which can then diffuse apart to give various products. The separated radicals can be trapped with radical scavengers such as thiols (Scheme 21). In Lewis's study of can-cleavage from a series of a-phenylacetophenone derivatives,24 the quantum yields of benzaldehyde formation are greatly increased with the addition of low concentration of dodecanethiol and rise to a maximum of ca. 0.45 at 2xlO'3 M thiol 123 Table 21. Quantum Yields and Rate Constants of Reactions of a-Arylacetophenones mtg—ameQaLOJE'll‘JsflQ'BLS‘lld_lsd.m'81§‘1f. 1 0.54 0.017 2 0.7 3.6 <0.15 3 0.08 0.013 1.5 0.023 4 0.38f 4.4 5 0.04 0.55 1.2 1.6 1.2 6 0.015 0.37 A curved Stern-Volmer plot obtained 7 0.31f 69 8 0.01 0.033 5.8 1.8 50.6 9 0.013 0.041 0.14 0.045 1.0 10 0.021 0.012 6.7 0.38 31.0 11 0.33f 810 12 0.040 5.5 13 0.073 20 14 0.35f 73 15 1.0 1.6 16 0.54 6.8 5.8 TMES >1.o93 a. Quantum yield of a-cleava e. b. Maximized quantum yields of indanol in the presence of Lewis bases. c. te constant of a-cleavage. d. Rate constant of 6-hydrogen abstraction. e. Rate constant of charge transfer. f. Maximized quantum yield of aldehyde formation. g. 1,2,3-trimesitylethanone. 124 concentration. This is the point where all the outcage benzoyl radicals have been trapped to form benzaldehyde. o 0 O )K J1... II II Ph R PhC- 'R ——” PhC- + R- RSH PhCHO Cage Products Scheme 21 In our study, with the ketones which undergo can-cleavage reactions, the quantum yields of benzaldehyde increase to a maximum value from 0.31 to 0.38 (Table 2) at more or less the same thiol concentration as in Lewis's study (Figure 15 and 16). Since a-cleavage is the only reaction that these ketones undergo, the maximized quantum yields of benzaldehyde formation in the presence of dodecanethiol can be taken as a measure for the cage-effect in the cit-cleavage reactions of these ketones. The quantum yields obtained in Lewis's and our studies average approximately 0.4.. This indicates that only 40% of the initialy formed radicals are able to undergo reactions which give rise to products other than starting ketones. The other 60% of the radicals simply recombine in solvent cages to return to the starting ketones. Keeping this in mind, we multiplied all the maximized quantum yields for benzaldehyde formation by 1/ 0.4 to give the estimated values of 125 cat-cleavage quantum yields, (cx). Since a-cleavage quantum yield is related to the rate constant for can-cleavage, kg, and the triplet lifetime, 1, in the following way: (No) = ka‘t (17) kc can then be estimated by equation (18), for the ketones which undergo cat-cleavage as well as other reactions: kc = (<:n)‘t’I (18) The results so obtained are listed in Table 21. Wagner31 has deduced that the formation of indanols is from a 6-hydrogen abstraction followed by the cyclization of the biradical produced.The identity of the biradical has been established by its transient UV absorption spectrum with flash photolysis technique.92 The estimation of rate constants for 6-hydrogen abstraction can be accomplished in a similar way: k5 = (6>t'1 (19) where k 5 is the rate constant for 6-hydrogen abstraction, (6) is the quantum yield for indanol formation, 1: is the triplet lifetime, However, in order for the equation to hold true, maximized quantum yields should be used. A maximized quantum yield is the quantum yield for product formation under the circumstance where all the biradicals react to give the indanol products. It is now well known that any hydroxybiradical type of intermediate can 126 undergo reverse hydrogen transfer to generate ground state starting ketones, resulting in low quantum yields for product formation. Solvents that are reasonable Lewis bases can prevent the reversion by forming a hydrogen bond with the hydroxy group, therefore, making the hydroxy hydrogen not accessible (Scheme 22).93 The quantum yields measured in the presence of a Lewis base can hence be used as the maximized quantum yields for indanol formations (Table 2). , H--- B I I “you +9011 011 Ph + )\ Ph \ ' OH Scheme 22 The quantum yields of indanol from a-mesitylpropiophenone 5, a-mesitylvalerophenone 6, and a-mesityl-a-phenylacetophenone 8 in benzene with 2 M dioxane are used as the maximized quantum yields. Although the quantum yields in acetonitrile and methanol are higher, they are thought to be due to the increased formation of products from the charge transfer complexes involved in polar solvents. This will be discussed later. forma The L‘ subsh corres know differ the h come 1W1 keton altera SUChe trimet 0f the Cont“ 127 For q-(o-tolyl)propiophen0ne 2, the quantum yield of indanol formation decreases in the presence of Lewis bases for an unknown reason. The upper limit of .of 6-hydrogen abstraction rate is thus estimated by substraction of 1‘01 from 1'1 of the ketone. The estimated k 5 values are given Table 21. It is noted that for the Q'mESitYI ketones, the sum of kg and kc corresponds to only a portion of the total decay rate. Since there is no other known excited state decay process for these ketones, it is believed that the difference represents the rates of the charge transfer reactions which lead to the formation of 1,3-aryl migration products in several ketones. We will come back to this point in the discussion of the migration reaction. 2. What Determines the Excited State Decay Modes? As mentioned above, the photochemistry of these sterically congested ketones has shown such a sensitive substituent effect that only a minor alteration of structural features leads to completely different photoreactions, such as in Reactions 16-19. a-Mesitylacetophenone, 1,2,2-trimesitylethanone, d-mesityl-2,4,6- trimethylacetophenone 14 are all structurally capable of undergoing all three of the above reactions, however, only one reaction occurs in each case. What controls the photoreactivity? It has been noticed that a general trend in the change of photoreactivity is that cat-substitution reduces the reactivity of the triplet ketones towards 5-hydrogen abstraction, and causes the emergence of other products, such as can-cleavage and 1,3-aryl migration products. The discussion will be presented following this logic line. fik 128 1‘” Q —-> Reaction 1645 0 OH K 1112 Ph Ph D Mes |\ 1w V m Mes . H /—\ Mes. Mes Reaction 1847 Reaction 1735 OMes 0 11V : k —-——> + . MesCO Mes ° Reaction 19 129 3. a-Substituent Effect on 6-Hydrogen Abstraction Indanol formation is observed with the ketones shown in Reaction 20-21. The estimates of the rate constants are given in Table 21 which indicates a decrease of reactivity with a-substitution. O OH K h V 5 + Q-Cleavage Ph Ph Products R R + T e II Products R = H, CH3 , CH3 (CW2 yp Reaction 20 O 08 k 1"” : + Q-Cleavage Ph Ph Products R R R = a, ca3 , CH3 (c112,)2 , R OMes Ph + V H A Ph Reaction 21 For a hydrogen abstraction reaction, five parameters characterize the geometric relationship between the abstracting oxygen atom and the hydrogen atom being abstracted. These are d, the oxygen to hydrogen 130 distance; n, the angle defined by the oxygen...hydrogen vector and its projection on the nodal plane of the carbonyl group; A, the angle between the carbonyl carbon, the carbonyl oxygen, and the target hydrogen atom; 6, the angle between the carbonyl oxygen, the hydrogen atom, and the carbon to which the hydrogen atom is attached; 9, the angle defined by the vector between the hydrogen atom and the carbon to which the hydrogen atom is attached and its projection on the nodal plane of the carbonyl group (Figure 54).58,88a The structure on the right is viewed from oxygen along the C=O bond. Figure 54 Scheffer58r88a has pointed out that the generally recognized ideal values for n, A, e, and p are 0°, 90°, 180°, and 0° respectively. This is not a surprising conclusion if we realize that it is the half-filled n orbital of the oxygen which is responsible for the reaction. The conformation in Figure 55 is thus the best geometry possible for s-hydrogen abstraction from a-arylacetophenone derivatives on the basis of above consideration. This conformation may or may not be a conformation with a minized energy of the molecule. It is the ideal transiton state geometry for the reaction. 131 Figure 55 Any structural features destabilizing the ideal geometry for 5-hydrogen abstraction relative to the most stable conformations ofthe molecules will reduce the reaction rate. The discussion how cat-substituents will affect 6-hydrogen abstraction rate is classified by the types of ketones. d-Arylacetophenones Molecular mechanics calculations show that a-(o-tolyl)acetophenone 15 has two stable conformations of comparable energies, conformation 155 and conformation 158'. The difference between these conformations is the orientation of the tolyl group. The methyl group can either point toward or away from the carbonyl group. 6-Hydrogen abs traction can only occur from conformation ‘155, which happens to be the the ideal geometry for the reaction. In order for conformation ’155' to react, the tolyl group has to rotate 180° to achieve conformation ‘155. For a ketone with a 2,6-symmetrically methylated d-ring, such as a-mesitylacetophenone 16, molecular mechanics calculations reveal that conformation 165 is the most stable conformation. The impossibility for 132 a-mesitylacetophenone 16 to have a nonreactive conformation like 155' accounts for the rate increase from 15 to 16. OH 1112 ,. 153 > 155 a 03< Ph hv * 155' > 158' Scheme 2 This argument was orignally made by Wagner and Meador,35 although conformations proposed there are slightly different from the ones obtained from molecular mechanics calculations. An excited state equilibration between 155 and 155' was assumed, and an equilibrium constant of 4 was estimated for the excited state interconversion between 155 and 155' in favor of 155' (Scheme 23). The above argument was reinforced by our results, hoWever‘ an equilibrium constant of 4 is now believed to be inaccurate, because it is realized that the hydrogen abstraction rate from d-mesitylacetophenone 16 is only 6.8x108 5‘1 (Table 21) and that a charge transfer quenching of the ketone is responsible for the rest of the excited state decay. A revised procedure following the same logic, assuming that d-mesitylacetophene 16 reacts by 6-hydrogen abstraction only 4 times as fast as q-(o-tolyl)acetophenone 15 (Table 21), gives an equilibrium constant of 1 between excited 155 and 155'. It agrees very well with the results from molecular mechanics calculations. 133 The most stable or one of the most stable conformations of the a-arylacetophenone happens to be the conformation ideal for s-hydrogen abstraction. Therefore, fast hydrogen abstraction is observed with these ketones, compared to their d-monosubstituted derivatives. d-Arylpropiophenones, q-Arylvalerophenone and a-Mesityl-a-Phenyl- acetophenone When a alkyl group is added to the can-carbon of the acetophenones, dynamic NMR studies indicate that there is a significant restriction on the rotation of the mesityl group in o: -mesitylpropiophenone 5, d-mesitylvalerophenone 6 and or-mesityl-on-phenylacetophenone 8 (Figure 56). The two o-methyl groups differentiate themselves at low temperatures (Figure 34-42). Analyses of linebroadening give rate constants of 9.5x103 s'l, 1.4x103 s‘1 and 4.4x104 5‘1 for the mesityl rotation in a-mesitylpropioiphenone 5, d-mesitylvalerophenone 6 and a-mesityl-cx-phenylacetophenone 8 respectively (Table 5, 6 and 9). Figure 56 134 These results imply that a strong steric interaction will arise if the mesityl o—methyl groups are close to the d-alkyl group in the molecules (Figure 57). Molecular mechanics calculations also reveal an unfavorable interaction between the aryl o-methyl groups and the can-substituents in the a-arylpropiophenones, a-arylvalerophenones and a-mesityl-a-phenylaceto- phenone 8, when they are near each other. All the energy-minimized conformations of the molecules have these two groups as far apart as possible. A conformation in which they are close together can't become an energy-minimized conformation of the molecules. It is noted that the ideal conformation for 6-hydrogen abstraction is such a destabilized conformation (Figure 58). Figure 57 Based upon these results, it is reasonable to conclude that the conformation required for d-hydrogen abstraction is destabilized due to the steric repulsion between the aryl o-methyl groups and the a-alkyl group. It is an unstable (non-minimized) conformation of the molecule. The energy-minimized conformations of these molecules have been calculated for the ketones. They are 2(3/36, 26730, and 213/313 for 135 a-(o-tolyl)propiophenone 2 and a-(o—tolyl)valerophenone 3, 56/66 and 512/613. for d-mesitylpropiophenone 5 and d-mesitylvalerophenone 6, and 8E and 86 for d-mesityl-d-phenylacetophenone 8, with 26 / 36 and 56/66 being the most stable ones for the corresponding ketones and 8E and 86 having comparable energies. Figure S8 The X-ray structures of a -mesitylvalerophenone 6 and a-mesityl-d-phenylacetophenone 8 have shown that these two ketones adopt a conformation similar to 66 and 86 in solid state (Figure 27 and 28). If it is assumed that these molecules do crystallize in their most stable conforamtions, the crystallographic results suggest that 66 and 86 are the most stable conformations of the molecules in solution. This conclusion does not contradict the results from molecular mechanics calculations, although calculations have shown that on-mesityl-a-phenylacetophenone 8 has conformation 8F. besides 86. This seems to suggest the possible coexistence of the two conformations in solution. From the results presented so for, it is clear that the substituent at the cat-carbon of d-arylacetophenones has two conformational effects: 136 a. it changes the structures of the most stable conformations for the ketones. b. it makes the geometry ideal for s-hydrogen abstraction an unstable (non-minimized) conformation. How will the conformational changes affect the photoreactivities of the ketones Let's assume that an excited state equilibrium between different conformations is established prior to the 6-hydrogen abstraction for all the ketones which undergo the reaction except for a-mesitylvalerophenone 6. The interconversion between the conformations of the ketones requires a CQ-CO bond rotation. Although on-arylisobutyrophenones have restricted rotations along their CQ-CO bonds, we believe that the additional methyl group at the a-carbon plays an important role. With three large substituents at the d-carbon, any rotation larger than 60° will suffer from a disfavored interaction between the phenyl group attached to the C=0 group and one of the cut-substituents. The interconversion between the energy-minimized conformations of the a-arylpropiophenones, d-tolylvalerophenqne 3 and o:-mesityl-a-phenylacetophenone 8 however can be achieved without creating such steric interaction in the molecules. In addition, the more rigid orientation of the a-aryl ring imposed by the two can-methyl groups in d-arylisobutyrophenones can cause more resistence towards the rotation. The a-aryl groups are oriented in such a way (46 and 76) that they will interfere strongly with the carbonyl phenyl group during rotation. On. the other hand, the more flaxible orientation of the a-aryl ring in ketones 2, 3, 5, and 8 makes it easier to avoid such interference. As it has been pointed out, the ideal geometry for 6-hydrogen 137 abstraction is destabilized by d-substitution. d-Mesitylpropiophenone 5 and d-mesitylvalerophenone 6 have an activation energy as high as ca. 8 Kcal/ mole regarding the mesityl rotation in the molecules (Table 5 and 6). Although the energy barrier of the conformational change from the most stable conformations to the ideal geometry for 6-hydrogen abstraction in these molecules is not quite the same as that of mesityl rotation in 5 and 6, it is obvious that such conformational change has to be an up-hill process of substantial magnitude in terms of energetics, because the ideal geometry suffers from a similar disfavored steric interaction between the o-methyl groups of the mesityl group and the cat-substituent as in the transition state of the mesityl rotation (Figure 57 and 58). So it is reasonable to conclude that the 6-hydrogen abstraction of these ketones can not occur from the ideal geometry with these cat-substituted d-arylacetophenones. It is generally accepted that when the geometric parameters of hydrogen abstraction deviate from their ideal values, the reaction rate will be reduced. But no experimental results have been reported so far in literature to demonstrate to what extent the rate will be decreased. Scheffers8 has reported that there is no strict geometric requirement for hydrogen abstraction to occur in a group of a-cycloalkyl-p-chloro- acetophenone in solid state. This result suggests that hydrogen abstraction can indeed occur form a non-ideal geometry, although probably with a slower rate. The stable conformations by molecular mechanics for the car-substituted d-arylacetophenones can be classified into two types, the conformations with the Can-Ar bond eclipsing with the carbonyl group (the E type), and the conformations with Cor-Ar bond rotated ca. 120° away from the carbonyl group (the 6 type). In the cases of a-tolyl ketones, the tolyl group may be 138 oriented differently with regard to the placement of the tolyl o-methyl group. Since it has been concluded that it is impossible for the ketones to rotate to the ideal geometry and react from there, we believe that the reaction proceeds from some of these stable conformations which are not ideal but still possible for the hydrogen abstraction to occur. Conformations 26/ 36, and 2E/3E can be ruled out immediately due to the obviously unfavorable arrangements of the tolyl o-methyl group for the reaction. Careful examination of models suggests a A of 70-80°, n of 60-70°, e of 160-170° and p of 60-70° for 26'/ 36', 56/66, and 86; and a A of 80-90°, n of ca. 90°, 9 of 170-180° and p of 30-40° for 5E-/6E, and 8E between the carbonyl oxygen and the o-methyl group of the a-aryl group near the carbonyl group in these conformations. Although the E type conformations of ketones 5, 6, and 8 have very attractive A, 6 and p values, a n of ca. 90° indicates an almost perpenticular orientation of the hydrogen...oxygen vector to the n-orbital of the carbonyl oxygen. Such arrangement does not seem to be possible for the hydrogen to be abstracted at a reasonable rate. 50 we conclude that the 5-hydrogen abstraction occurs form the 6 type conformations (26'36', 56/66, and 86) of these car-substituted a-arylacetophenones. SE ——> 5B 1 1.. / W. hV a: 5G ——-> Scheme 24 139 In support of the above proposal is the fact that a-mesitylvalerophenone 6 and o:-mesityl-d-phenylacetophenone 8 undergo 6-hydrogen abstraction to give the indanols with high chemical yields in solid state, and X-ray crystallographic results show that the ketones adopt conformations similar to conformation 66 and 86 in solid state. A mechanistic scheme is thus provided (Scheme 24), using a-mesitylpropiophenone as an example. The molecules are excited in their stable conformations 56 and 5E, between which an excited state equilibrium is established. The hydrogen abstraction then occurs from 56. The rate constant has the following expression, kobs = kng(r) _ (20) where kobs is the observed rate constant, k 5" is intrinsic rate constant from the reacting conformation, X(r) is the percentage population of the reacting conformer of the ketone in the excited state equilibrium. Scheme 24 can be applied to all the other or -substituted a-arylacetophenones ecxcept for a-mesitylvalerophenone 6, which shows two non-equilibrated excited states , and will be disscussed later. The decrease of 6-hydrogen abstraction rate in the cat-substituted ketones can be due to two factors, a decrease in the intrinsic rate of the reacting conformation caused by non-ideal geometric arrangement, or a decrease in the percentage population of the reacting conformer. Since conformation 56 is the most stable conformation of d-mesitylpropiophenone 5, like 165 being the one of a-mesityacetophenone 16, majority of the excited molecules will be in this conformation. Therefore, a 4 fold decrease of the reaction rate from ketone 16 to ketone 5 can't be 140 explained by the reduced population of the reacting conformation. The only alternative explanation is then that the reaction occurs from 56 of ketone 5 with a rate of 4 times slower than that from 165 of ketone 16. A rate decrease of at least 10 times from a-(o—tolyl)acetophenone 15 to d-(o-tolyl)propiophenone 2 is due to a combination of a reduced p0pulation as well as a reduced intrinsic rate constant of the reacting conformer 26'. If the same reduction (4 fold) in rate constant is assumed from conformation 155 of ketone 1 5 to conformaton 26' of ketone 2 as from d-mesityacetophenone 16 to d-mesitylpropiophenone 5, then at least 2.5 fold reduction has to be attributed to the decreased number of reacting conformer 26' for ketone 2 , compared to the population of 155 for a-(o-tolyl)acetophenone 15. It is noted that ketone 2 has conformation 26, which is more stable than 26', as the most stable conformation of the molecules by calculations. Similarly a-mesityl-o:-phenylacetophenone 8 is also affected by both of the factors, a decreased population and a decreased intrinsic rate of the reacting conformer. Because an car-phenyl and a-methyl group may impose different steric congestions around d-mesityl group, it does not seem justified to assume that conformation 86 of ct-mesityl-or-phenylacetophenone 8 has the same intrinsic rate as conformation 56 of d-mesitylpropiophenone 5. Such difference is indicated by the different activation energies of mesityl rotation for ketone 5 and 8, with the phenyl group having a weaker steric resistence towards the rotation (Table 5 and 9). A less sterically congested mesityl group may be able to undergo a faster reaction. If it is assumed that ketone 8 has an excited state equilibrium constant of ca. 1 between 86 and 8E, as indicated by molecular mechanics calculations, 2 fold out of the overall 4 fold decrease of the reaction rate from d-mesitylacetophenone 16 to 141 a-mesityl-a-phenylacetophenone 8 is then caused by the reduced population of reacting conformer 86, and another 2 fold reduction is due to the bad geometric parameters for the reaction for a~mesityl-o:-phenylacetophenone 8. a-(o-Tolyl)valerophenone 3 can be described qualitatively in the same way, although lack of data makes it impossible to do any quantitative analyses. 4. Formations of Aryl Vinyl Ethers 1.3-Aryl shift has been observed with the several ketones (Reaction 22). Table 22 shows that the quantum yields generally increase with the increasing bulk of the ketones. The least congested a-mesitylacetophenone gives no aryl vinyl ethers. On the other hand, the most crowded 1,2,2-trimesitylethanone forms the ethers with a quantum yield of 0.4. The ketones with varing steric congestions in between the two ketones give the ethers with quantum yields between the extreme values. OH L hv + "(x-Cleavage PhX Phx Products R R s CH3, CH3 (c112)2 R OMes with X a H R-Ph + A?“ with x = H, CN, oca3 Reactoin 22 142 The ether formations is quenched with typical triplet quenchers such as 2,5-dimethyl-2,4-hexadiene and naphthalene. The lifetimes obtained from quenching the ethers and indanols with d-mesityl-a-phenylacetophenone 8 and on-mesityl-a-phenyl—p-methoxyacetophenone 9 are identical within experimental error. This implies that the two different photoproducts have the same triplet precursor. Table 22. Quantum Yields of Aryl Vinyl Ether Formations in Bezene Ketones 16 S 6 8 9 10 'I'MEa DMAPa £(E) 0.0 0.012 0.0038 0.025 0.0084 0.0046 0.4 low a. a-DMAPud,o:-dimesitylacetophenone,4° TME--1,2,2-trimesitylethanone47 It has been well documented that p-methoxy phenyl ketones have a run" triplet as their lowest triplet state. Such a ketone shows a dramatic decrease in the rate constants for any n,n‘ reactions, which reflects the reduced population of the reactive n,n" triplets in a n,n" and 11,11" equilibrium.5ar9‘11 A nearest example of this effect is provided by a-(o-tolyl)-p-methoxyacetophenone 1. This ketone undergoes 6-hydrogen abstraction with a rate ca. 100 times slower than that of or-(o-tolyl)acetophenone 15. This conclusion can be used vice versa. If a reaction displays a reduced reactivity with the introduction of a methoxy group, it is probably a n,11‘ reaction. The observation that a-mesityl-<——’ Ph ° Ph 4696 '7 OH 00 Ph Scheme25 Irradiation of d-mesitylacetophenone l6 afffords 5,7-dimethyl-2-phenyl- 2-indanol as the only product. But the quantum yield of the product reaches only 0.54 in the presence of Lewis bases.31 This brings up a question: where do the other 46% of the excited ketones go (Scheme 25)? An explanation is that the formation of the corresponding enols of the ketone through the 1,5-biradical generated in the s-hydrogen abstraction (Scheme 26). This is a sound possibility, since Wagner79 has reported that a-(2,4,6-triisopropylphenyl)acetophenone forms the indanol product as well as its enols upon irradiation. 144 H---s I ’I o 0 11V ' K «+—" ' Ph ' Ph OH OH L W . m ph P Scheme 26 g If the enol formation is indeed involved, irradiation of a-mesitylacetophenone—dz 16-d is expected to lead to a deuterium exchange in the starting ketone and an isotope effect in the indanol formation, with d-mesitylacetophenone-dz 16-d showing a higher quantum efficiency for the product formation (Scheme 27).94 However, the negative results of the isotope labling experiments rule out possible enol formation. As we have noticed before, the same type of quantum inefficiency exists with the other a-mesityl ketones. The sum of the rates of the known reactions for the ketones corresponds to only a portion of the total triplet decay rate. This therefore leaves us a task of finding a mechanism which requires participation of the excited ketones, but produces no products. It is recalled that p-arylpropiophenones undergo a fast intramolecular charge transfer quenching of n,n“ states by the p-rings.°°'°9 It is possible that such 145 quenching process can also occur with a-mesitylacetophenone 16 and its several derivatives. 0 k 111) . Ph D D D D 0H L «t L Ph '/ Ph H D D Scheme 27 The mesityl group is known to be a good elctron donor.88b It is not far beyond imagination that a charge transfer complex can be formed between an electron defficient oxygen and an electron rich mesityl group in these ketones. The charge transfer complex can decay to the ground state starting ketones, which will account for the quantum inefficiency in the formations of the photoproducts from these ketones. The complex may also rearrange to form an intermediate with a four-member ring, which is a procursor for the aryl vinyl ethers. Opening-up of the ring will afford the ethers (Scheme 28). 146 As it has been pointed, the least crowded a-mesitylacetophenone 16 does not form the corresponding aryl vinyl ether. Only the more crowded ketones can undrgo such a reaction. The formation of the intermediate with a four-member ring is expected to be an up-hill process in terms of energetics, due to the strain of the structure. 50 its formation is limited to sterically congested ketones. The release of the steric congestion in the ketones can be a driving force for the transformation. 0 t .- 0° a" . N ‘ R Ar Ground States 54 Scheme 28 In Rapport's extensive study of ketone-enol interconversion of simple ketones,95 it has been found that the steric congestion in the ketones makes the ketones less stable than their enol forms which are sterically favorable. 147 For instance, the enol of 1,2,2-trimesitylethanone is so much more stable than the ketone itself, no successful synthesis of the ketone was reported until recently by Rapport. The spectroscopic data of the ketone indicates severe distortions in the molecule, which can be released by forming the corresponding enols. The breaking-up of the four-member ring intermediate then leaves a twisted C=C bond. This structure pictures the geometry of an excited aryl vinyl ether. Since it is well known that an excited stiblene decays to its ground state with a Z:E ratio of roughly 1:1,96'97 the fact that Z:E ratios of the ethers are indeed close to 1:1 in all the cases where they can be experimentally measured strongly suggest the idea of forming an excited aryl viny ether. The strained structure of the four-member ring intermediate implys that such a process may be accessable energetically. The initially formed excited C=C then decays to the ground state with a Z:E ratio of 1:1. The intermediate may also return to the starting ketones. This will provide an additional pathway responsible for the low quantum efficiency of enol ether formation. 0 ' < Ar Figure 59 The rate constant of charge transfer can be derived by substracting 1‘01 148 and k 5 from the reciprocal lifetime for each ketone, kct=l/t-kq-k5 (21) The results are listed in Table 21. The charge transfer process seems to require a geometry more or less with the aryl-Ca bond eclipsing with the carbonyl group and the aryl ring perpendicular to the plane of the carbonyl group (Figure 59). This geometry is not an energy-minimized conformation of d-mesitylacetophenone 16. The ketone therefore has to rotate to this geometry to react. The reaction can occur from all the conformations. The charge transfer rate has an expression including the contributions from all the conformers in an excited state equilibrium, kc, = 2 X(i)kcti (22) If the conformations other than the most stable conformation can be neglected, then k ct = kctm (23) where kctm is the rate constant of the most stable conformer. The most stable conformation of a-mesitylacetophenone 16 is in the neighbourhood of the geometry in Figure 59. As a result, 4a decent rate constant is observed with this ketone. One of the energy-minimized conformations of d-mesitylpropio- phenone 5 and a-mesityl-o:-phenylacetophenone 8, i.e. 5E/6E and 8E by 149 molecular mechanics, happens to have a similar structure to the ideal geometry indicated in Figure 59. The charge transfer occurs from this conformer in an excited state equilibrium. The reaction rate equals the intrinsic rate from the reacting conformer multiplied by its percentage population in the equilibrium, kCt = X(r)kctr (24) where X(r) is the percentage population of the reacting conformer, kctr is the rate constant of the reacting conformer. Any changes in X(r) will affect the overall kct: Molecular mechanics calculations have suggested the steric energy of the reacting conformer is lowered significantly from cx-mesitylpropiophenone 5 to a-mesityl-a-phenylacetophenone 8. This corresponds to a bigger X(r), and thus a larger kct for d-mesityl-o:-phenylacetophenone 8. Figure 60 Rappoport95‘ has reported that 1,2,2-trimesitylethanone has a conformation as given in Figure 60. Both 6-hydrogen abstraction and charge 150 transfer are easily accessible from this conformation. However, it has been concluded that 5-hydrogen abstraction occurs with a rate constant of ~5x108 s'1 even when the ketone has the right conformation, such as in the case of d-mesitylacetophenone 16. On the other hand, the charge transfer can have a rate constant as fast as ~5x109 s’1 with d-mesityl-a-phenylacetophenone 8, implying that such process could be significantly faster than 6-hydrogen abstraction in 1,2,2-trimesitylethanone too. The carbonyl mesityl group of 1,2,2-trimesitylethanone is twisted by ~50°. This could very well reduce the rate of y-hydrogen abstraction in the ketone. 50 a mechanistic picture for 1,2,2-trimesitylethanone would be that a fast charge transfer, dominating over the other two hydrogen abstraction processes, leads to the formation of the complex upon irradiation, which is then forced to form the enol ethers by the steric congestion in the ketone. 5. (rt-Cleavage Reactions or-(o-Tolyl)isobutyrophenone 4, a-mesitylisobutyrophenone 7, or-mesityl-2,4,6-trimethylacetophenone 14, and d-mesityl-a-phenyl-2,4,6- trimethylacetophenone 11 undergo exclusive d-cleavage reactions. The lifetimes of these ketones and the quantum yields of the aldehydes formed as the trapping products of the benzoyl radicals generated in the cleavages by dodecanethiol are listed in Table 1 and 2. The reciprocal triplet lifetimes are taken as the cleavage rates. There are two interesting aspects of the reactions. First, although all these ketones can undergo reactions such as the formation of indanols or aryl vinyl ethers in terms of structural possibilities, none of the reactions are observed, except for a-cleavage. 151 Second, these ketones have triplet lifetimes much shorter than the ones of their less congested analogues, which also undergo only cat-cleavage, e.g. a-phenylacetophenone, and 01-phenylisobutyrophenone.24 Since the individual ketones all have different structure-reactivity relationships, we will pursue the discussions by the types of the ketones. cr-Arylisobutyrophenones Low temperature 1H NMR studies of at-(o-tolyl)isobutryophenone 4 and a-mesitylisobutyrophenone 7 show restricted rotations of the CQ-CO bond in the molecules (Figure 61). The rate constants are estimated to be on the order of 104-105 5'1 at 25°C (table 4 and 7). Figure 61 The two methyl groups are differentiated at low temperatures (Figure 31-33, 43-46). The different chemical shifts of the two methyl groups indicate an asymmetric arrangement of the methyl groups with' respect to the molecular plane (the plane which contains the carbonyl group). So it is suggested that the conformation in Figure 62 is the most stable conformation of the molecules, in which one of the methyl groups is more of less eclipsing 152 the carbonyl group, and the other 120° away from it. Molecular mechanics calculations agree very well with this notion. The mesityl rotation in a-mesitylisobutyrophenone 7 also suffers from restriction. The rotational rate constant is 1.7x105 s’1 at 25°C (Table 8). The conformation in Figure 62 complies with the requirement that the o-methyl groups of the methyl groups be as far away from the can-methyl groups as possible. The separated o-methyl signal at 1.90 ppm in low temperature NMR spectra is thought to be the one of the methyl group near the carbonyl group, because it is somewhat in the shielding zone of the C=O bond. The methyl group at 2.63 ppm is the methyl group away from the carbonyl group (Figure 43-46). . Figure 62 The steric interaction between the o-methyl group away from the carbonyl group and the two cat-methyl group in Figure 62 raises the energy of this conformation relative to the one of the conformation in Figure 63 for or-mesitylisobutyrophenone 7, which is the energetic peak along the (IQ-mesityl bond rotation. Thus a-mesitylisobutyrophenone 7 has a mesityl rotational rate constant greater than d-mesitylpropiophenone 5 (Table 5 and 8). Figure 63 The tolyl methyl group in a-(o-tolyl)isobutyrophenone 4 has a methyl signal at 1.98 ppm, implying that the methyl group is near the shielding zone of the C=O bond, such as in conformation 46. Molecular mechanics calculations also suggest that conformation 46 is the most stable conformation for this ketone, in which the unfavorable interaction between the tolyl methyl group and the two a-methyl groups can be avoided. The photoreactivities of the d-arylisobutyrophenones are completely governed by their ground state confornmations. Irradiation of the ketones generates the excited molecules in their ground state conformations. Since the rotations of the molecules to obtain the conformations reqmred either for the s-hydrogen abstraction or for the charge transfer quenching are as slow as 104-105 5'1 per mole (table 4 and 7), and the cat-cleavage rates range from ca. 108-109 s"1 per mole (table 1), it is not surprising that d-cleavage reactions are the only reactions observed for these ketones (Scheme 29). Although it has been concluded that ketones 2, 3, 5, 6, and 8 undergo 5-hydrogen abstraction from the nonideal conformations in which they are set, a-arylisobutyrophenones 4 and 7 have their aryl rings oriented differently in their ground state conformations from these 154 a-monosubstituted ketones. The aryl rings in ketones 4 and 7 have to parallel with the (IQ-CO bond of the ketones due to the presence of the two cat-methyl groups , which makes the benzylic methyl group of the aryl groups more distant from the carbonyl oxygen than in the monosubstituted ketones. '0 Ar SCI-I3 CH3 4 r. 10 -10' 109-109 ‘ CH3 > Cleaves Ar CH3 Scheme 29 hv /\ ----/< \ Scheme 30 155 Furthermore, the more rigid orientation of the aryl groups imposed by the two methyl groups prohibits slight movement of the rings to reach a reasonable transition state gecmetry. Lewis24 has measured the rate of cit-cleavage with d-phenyliso- butyrophenone, and found that the rate constant is 1.2x108 s'l. The cleavage rate constant for a-mesitylisobutyrophenone 7 is 7.3x108 s'l. The significant enhancement in the rates reflects the extent of release of the indicated steric congestion in d-mesitylisobutyrophenone 7 on going to the transition state (Scheme 30). a-Mesityl-2,4,6-trimethylacetophenone X-ray crystallography shows that a-mesityl-2,4,6-trimethylacetophenone 14 has a conformation as given in Figure 29 in solid state. Let's assume that this ketone has the same conformation in solution as in solid state. This assumption is supported by molecular mechanics calculations (Conformation 14E) and other spectrOSCOpic data. Phenyl ketones absorb strongly around 240 nm due to an allowed transition (K band) which may be represented by PhC=O -—> +Ph=C-O’. The K band absorbance (c) of the ketones depends on the extent of conjugation between the phenyl and carbonyl group, therefore on the coplanarity of the phenyl and carbonyl group. nonplanarity caused by o-methylation on the phenyl ring reduces the extent of the conjugation. Loss of conjugation will in turn lead to a decrease in 686 IR absortion of C=O bond is another measure for the Ph-CO conjugation. The resonance structure +Ph=C-O' as a result of conjugation weakens the C=O bond and causes a bathochromic shift in the absorption 156 frequency. A reduced conjugation will, on the other hand, produce a hypsochromic shift.85 13C NMR absorption of the carbonyl carbon in a phenyl ketone is also affected by the extent of conjugation between the phenyl and carbonyl group. Acetone absorbs at 203.8 ppm. Replacement of the methyl group of acetone by a phenyl group causes an upfield shift of the C=O absorption to 195.7 ppm. Presumably, charge delocalization by the benzene ring makes the carbonyl carbon less electron deficient. If the conjugation is restricted by any means, the C=O absorption is expected to experience an downfield shift.84 The spectroscopic data of several ketones are given in Table 11. The disappearance of the K band in UV, the hypsochromic shift of the C=O absorption in IR, and the downfield shift in 13C NMR of a-mesityl-2,4,6-trimethylacetophenone 14 support the stucture with the carbonyl group orthogonal to the mesityl groups (14E). Such a structure simply makes the hyrogens not available for either the 6-hydrogen abstraction to give the indanol, or the y-hydrogen abstraction to give the cyclobutenol. 157 Lewisz4 has reported that a-phenylacetophenone cleaves with a rate constant of 2.4x106 s'l. The or -cleavage rate constant for at-mesityl-2,4,6-trimethylacetophenone is on the order of 103-109 s'1 (Table 1). The dramatic increase of the rate is due to the perfect geometry of the molecule for the cleavage. The two mesityl groups are properly oriented to stablize the radical centers produced by the cleavage (Figure 64). a-Mesityl-a-Phenyl-2,4,6-trimethylacetophenone Rappoport95 has reported the X-ray structure of a-Mesityl-d-Phenyl- 2,4,6-trimethylacetophenone 11 in solid state as described in Figure 65. Spectroscopic studies of the ketone in solution suggest a similar structure for the ketone. The mesityl group attached to the carbonyl group is twisted ca. 70° with respect to the plane of the carbonyl group. d-Mesityl-o:-phenyl-2,4,6-trimethylacetophenone 11 undergoes cat-cleavage at a rate of 8.1x109 5'1 per mole (Table 1). Two factors may be responsible for the fast cleavage. Figure 65 158 First, the nearly orthogonal arrangement of the phenyl group and the mesityl group attached to the carbonyl group with respect to the carbonyl group favors the the cleavage due to the stabilization of the radicals by the aromatic T! system. Second, the release of steric strain in the molecule accompanying the cleavage may serve as an additional driving force for the reaction. Neither the hydrogen abstractions (y and 5) nor the 1,3-aryl shift can occur with the conformation of the ketone at a rate comparable to the one for Cleavage, since the mesityl groups are badly oriented for these reactions. Furthermore, 6-hydrogen abstraction can't compete with the cleavage even if the mesityl group has the right geometry, if we recall that a-mesitylacetophenone undergoes the hydrogen abstraction only with a rate constant of 5.8x108 5’1. 6. Kinetic Rotational Control in a-Mesitylvalerophenone An interesting observation with a-mesitylvalerophenone 6 is. that this ketone shows a substantially lower quenching efficiency than can-mesityl- propiophenone 5. In another word, the excited state of a-mesitylvalero- phenone 6 decays faster than the one of d-mesitylpropiophenone 5 (Figure 14). d-Mesitylvalerophenone 6 can undergo the same types of reactions as a-mesitylpropiophenone 5 except that type II reaction could occur with ot-mesitylvalerophenone 6, but not with .a-mesitylpropiophenone 5. The observation that a-mesitylvalerophenone 6 gives only trace amount of type II products even in the presence of a lewis base eliminates the possibility that type II reaction is responsible for the faster decay of d-mesitylvalerophenone 159 6 triplets, although the molecule seems to have the right conformation for the reaction. 50 the faster decay of a-mesitylvalerophenone can't be explained with what“ we have known about this ketone. In addition, Stern-Volmer quenching of a-mesitylvalerophenone 6 gives rise to a curved plot, which indicates the existence of two excited states interconverting at a rate comparable with the rates of photoreactions. Molecular mechanics calculations reveal that a-mesitylvalerophenone 6 has two conformations with minimized energies. One is the most stable conformation, 66. The other with the mesityl group more or less eclipsing with the carbonyl group can be depicted as conformation 6E. . 5-H abstraction Q R1 1 k)! *66 “—————' 68 / k-i kct Other decays k d t Charge transfer Other decays <(—-——— 68 Scheme 31 cit-Cleavage can occur from both conformation 66 and 6E. On the other hand, 1,3-aryl migration is limited to 6E, and 5-hydrogen abstraction as well as type II reaction to 66. It can be assumed that only conformation 66 is populated in ground state, since a 3-4 Kcal/ mole energy gap is suggested by molecular mechanics calculations between the two conformations. It corresponds to an equilibrium constant of >153 in favor of conformation 66. Irradiation generates the excited molecules in conformation 66, which then 160 can convert to conformation 6E, or undergo the reactions possible for conformation 66. Conformation 6E can either return to 66, or react. A general scheme, which includes the population of 6B in ground state, illustrates all the possible decay pathways (Scheme 31). A stern-volmer equation concerning the quenching of the indanol is derived based on the scheme (Equation 26), °/ = (1 + AIQ] + BIQ]2)/(1 + (101) (25) A = qu/M, B = qu/M, C = k (k5 - X(6E)k5)/N q L=k5 +kd'+k,i+kct+kd+ki M = k_ikg + kctké + kdkg + k—ikd + kctkd' + kdkd' + kikct + kikd N = k_ikg + kctké + kdkg - X(6E)kctk5 - X(6E)kdk5 where X(6E) is the percentage population of conformation 6E in ground state. If X(6E) = 0, then, N = k_ik5 + kctk5 + de5 C =- qu5 / N The detail of the derivation of the equation is given at the end of the chapter.. A curve fitting of the experimental data dispalyed in Figure 14 by 161 KINFIT affords the estimated values for the individual parameters in the equafion, A =3.6 B =3.9 C =0.10 The ratio of A and B equals approximately 1. Thus we can obtain the following equation, A/B=L/kq=l (26) This leads to an estimate of 5x109 (kq) for L, which is a sum of several rate constants. The rotational rate from 66 to 6B, ki, is expected to be slow because 66 is more stable than 6E. The 6-hydrogen abstrasction rate. constant from conformation 66, k 5, should substantially smaller than the one for d-mesitylacetophenone 16, 6.8x10°. So 1‘1 and k 5 can both be neglected along with kd' and kd in equation (26). Then equation (26) becomes, L = k_i + kct = 5x109 (27) This gives an upper limit of 5x109 s'1 for either k-i or kct' Therefore, the fast triplet decay of ot-mesitylvalerophenone 6 can be attributed to the fast decay of conformation 6E by the charge transfer mechanism, and the rapid interconversion between 66 and 6E. The inefficiency of type II reaction from a-mesitylvalerophenone 6 can be due to the two facts. First, the type II reaction from conformation 66 has to compete with the conformational change from 66 to 6B, followed by a fast decay of 6E. This will reduce the efficiency of the type II reaction from 162 conformation 66. Figure 66 Second, the type 1] reaction from comformation 66 may very well be limited by the structure of a-mesitylvalerophenone 6 itself. Carefull inspection of a molecular model shows that a pseudo chair transition state for type II reaction with the Ca-Cp bond eclipsing with the carbonyl group will suffer from a steric interaction between one of mesityl methyl groups and the methylene group at CY (Figure 66) This interaction will decrease the rate for type II reaction. 7. Possible Formation of the 1,5-Biradical via a Proton Transfer form a Charge Transfer Complex The indanol formation quantum yields of a-mesitylpropiophenone 5, cx-mesitylvalerophenone 6, and o:-mesityl-d-phenylacetophenone 8. change with the nature of the solvents used. They are increased in benzene with 2M dioxane, acetontril'e, and methanol (Table 2). The enchancement in the presence of dioxane is thought to be due to the ability of the added dioxane to 163 form a hydrogen bond with the hydroxy group in the biradical, and retard the reserse hydrogen transfer to give the starting ketones. More increase of the quantum yields in acetonitrile than in 2 M dioxane is most amazing, since acetonitrile is known to be a less efficient lewis base to stop the reserse hydrogen transfer. H transfer . OH + H transfer '\Ph < R Scheme 32 One important aspect of well studied ketone photoreduction reaction is the fact that hydrogen atom abstraction can occur directly or via a charge transfer followed by a proton transfer to give the same radicals as the direct hydrogen abstraction will. The charge transfer path was first evident with amine donors, which are orders of magnitude more reactive than they would be as simple hydrogen atom sources.99'100 Wagner65 has pointed out the possibility that the photoreduction of triplet ketones by alkylbenzenes might occur under certain conditions by a combination of competing charge transfer 164 and direct hydrogen atom abstraction. A recent publication by 'Wagner101 reported the extent to which such direct abstraction competes with the charge transfer mechanism: The ketones we studied may represent an intramolecular case of such competition. The geometry of the charge transfer complex is believed to have the Cq-Ar bond eclipsing with the carbonyl group and the mesityl group perpenticular to the nodal plane of carbonyl group. This conformation is not suitable for the proton transfer. In order for it to occur, the mesityl group in the complex has to rotate to a geometry which has the right geometry and is energetically accessible as well. The conformational change will inevitably create an charge separation in the complex. Such charge separation has to be compensated by either solvation in polar solvents, or a favorable steric energy gain during the conformational change. The 6 type conformatoins of d-mesitylpropiophenone 5, d-mesitylvalerophenone 6 satisfy all the above requirements. They are more stable than their E type conformatoins. The conformational change from the charge transfer complex to a charge—separated intermediate with the 6 type conformation is a down-hill process in terms of steric energy. The proton transfer from the 6 type conformations is excepted to have a reasonable rate, since even the more geometry-requiring hydrogen atom transfer can occur from them (Scheme 32). The charge separation can be furthermore compensated by solvatoin in polar solvents. Acetonitrile and methanol can both serve as polar solvents to stabilize the charge separation through dipole-dipole interaction with the Charges in the complex. This atemative pathway for forming the 1.5-biradical from the charge transfer complex will increase the quantum yields of the indanols from the ketones in polar solvents. Although the quantum yield of indanol from a-mesityl-or-phenylaceto- 165 phenone 8 is doubled in acetonitrile as in 2 M dioxane in benzene, the absolute amount is only a few percent. This is not surprising if we realize that conformation 86 has comparable steric energy as conformation SE, which happens to be the geometry of the charge transfer complex. These two conformations are the most stable conformations of the ketone by calculations. The lack of a drive from the steric energy difference during the conformational change from 8E to 86 or any other possible conformations is responsible for the reluctant proton transfer in the complex of ketone 8. Similar result was observed with d-mesitylacetophenone 16. The quantum yield for indanol formation from 16 in acetonitrile is essentially the same as in benzene, implying that the proton transfer in the charge transfer complex does not occur in significant amount with this ketone. We believe that this is due to the same reason as in the case of a-mesityl-or-phenylacetophenone 8. The conformation adopted by the charge transfer complex from ketone 16 is calculated to be only 0.5 Kcal/mOle less stable than the most stable conformation of the ketone, 16S, and more stable than 166. The charge transfer complex therefore can't find a conformation which will allow the proton transfer and provide a steric energy compensation. 8. Photoenolization of or-(2,4,6-Triisopropylphenyl)acetophenone Wagner79 has reported that a-(2,4,6-triisopropylphenylacetophenone) forms 4,6-diisopropyl-1-dimethyl-2-phenyl-indanol as well as the enols of the ketone. It has been postulated that the enols are formed from the 1,5-biradical involved in the 6-hydrogen abstraction. However, this postulation needs experimental proof, since a photochemically allowed 1,3-hydrogen shift could 166 also lead to the formation of the same products. For this purpose, deuteriated a-(2,4,6-triisopropylphenylacetophenone) was studied. 1I-1 and 2H NMR studies revealed the deuterium exchange which can only be explained by the involvement of the biradical (Scheme 33). Furthermore, an isotope effect in the indanol formation was observed. The quantum yield of the indanol is approximately doubled with on-(2,4,6-triisopropylphenyl)acetophenone-d2 16 (Table 2), because d-deuteriation disfavors the formation of the enols by the primary isotope effect. . R OH O IIV K——> _. Ph ' Ph RDD RDD R = iso-Propyl Group Scheme 3 The quantum yield of indanol formation is decreased more than ten times for both a-(2,4,6-triisopropylphenyl)acetophenone and 167 a-(2,4,6—triisopropylphenyl)acetophenone-d2 16 in dioxane. The hydrogen bonding of the hydroxy group in the 1,5-biradical by the solvent increases the steric crowding around the hydroxy group, and hence slows down the cyclization of the biradical due to the reluctance for the two congested radical centers to get close. As a result, the enol formation is enhanced as an alternative decay pathway for the biradical.79 Since Wagner79 has observed a ratio of 15/1 for the enols and indanol in dioxane, while the ratio is found to be 1/ 1 in benzene, the quantum yields of the enols in dioxane and benzene are estimated to be 0.24 and 0.23 respectively. B. Photochemistry in Solid State The photochemical studies of the ketones in organized assemblies are just initiated, especially in the area concerning cyclodextrin complexes. However, the preliminary results will be discussed here. or-(2,4,6-Triisopropylphenyl)acetophenone The irradiation of a-(2,4,6-triisopropylphenyl)acetophenone in solution is known to give the corresponding indanol and the enols of the ketone. The indanol formation is as efficient as the enol formation in benzene. We have just established that the enols are formed from the biradical produced in the 6-hydrogen abstraction. In solid state, the ketone gives the enol as the major product, with a product composition of 91.1%, and the indanol as the minor product, with a product composition of 9.9%. The confinement imposed by crystal lattices makes it difficult for the 168 biradical to rotate ca. 90° to achieve the critical conformation for the indanol formation. While the enol formation requires almost no rotation of the 2,4,6-triisopropylphenyl group. The indanol formation is thus retarded by the difficulty in the rotation of the aryl ring in solid state (Scheme 34). R = iso-propyl group Enols Indanol Scheme 34 Although dioxane does increase the enol formation in solution, it is due to a different reason. d-(o-Tolyl)pr0piophenone a-(o-Tolyl)propiophenone 2 forms 2,3-di(o-tolyl)butane as the major a-cleavage product and 3-methyl-2-phenyl-2-indanol in solution. The irradiation of this ketone in crystal eliminates the formation of the coupling 169 product 2,3-di(o-tolyl)butane, and in the meantime, the can-cleavage reaction takes the course of forming benzaldehyde by disproportionation between the initially formed' radicals. An unusual rearranged product, p-(o-tolyl)propiophenone, is produced upon the irradiation in crystal or powder, along with the indanol. P/OH/Tflé [Pycinrml] ——> PhCHO arfi Tol Impossible in crystal “ff i - l | 2 T01 T0]. T0]. P l/ ———> . + PhCOCOPh Scheme35 The failure of forming 2,3-di(o-tolyl)butane in crystal is caused by the impossibility of the benzyl radicals to move around coupling with each other. Instead the benzoyl and benzyl radicals disproportionate to give the benzaldehyde and tolylethylene (Scheme 35). Turro has reported that a-phenylisobutyrophenone gives disproportionation products as the major cleavage products in micelle, presumably due to the increased cage-effect in the medium.°3d The rearrangement of a-(o-tolyl)propiophenone 2 to p-(o-tolyl)- propiophenone is believed to be a result of a secondary reaction of the 170 ot-cleavage products (Scheme 36). In solution, such a rearrangement requires that benzoyl radicals escape the solvent cage, and then react with a-(o-tolyl)ethylene molecules. Since disproportionation is not the major o \ o 92' + W'I'ol ’ PJMTOI O PhCHO O P Tol P Scheme 36 mode of the reactions that benzoyl and benzyl radicals undergo in solution, the concentration of a-(o—tolyl)ethylene is limited. Benzoyl radicals will also have to face the competitions from some other fast reactions in solution, such as coupling between the radicals. Thus the rearrangement is not favored in solution. In solid state, a-(o-tolyl)ethylene and benazaldehyde molecules exist in a fairly high concentration, because the disproportionation now is the major mode of the radical reactions and solid state is a very condensed phase. There is a good statistic chance that a benzoyl radical is produced nearby or-(o-tolyl)ethylene and benzaldehyde molecule. The inability of the radicals to undergo other reactons in solid adds another plus factor for the rearrangement. d-Mesitylpropiophenone, a-Mesitylvalerophenone, and a-Mesityl-a- Phenyl-acetophenone 171 Irradiations of d-mesitylpropiophenone 5, a-mesitylvalerophenone 6 , and a-mesityl-on-phenylacetophenone 8 in solid state afford nearly quantitatively the coressopnding indanols. The X-ray crystallography of ot-mesitylvalerophenone 6 and a-mesityl-a—phenylacetophenone 8 has provided the conformations of the ketones in solid state (Figure 27 and 28), which deviate substantially from the ideal conformation for s-hydrogen abstraction (Figure 55). However careful examinations of the structures reveal that the geometric factors concerning hydrogen abstractions of these ketones in solid state are ca. 60°-70° for n, 70°-80° for A, 160-170° for e, and 60-70° for 9. They are by no means the ideal values. But they do not stop the reaction in solid state. Scheffer58 has reported a similar observation that in the solid state photochemistry of several on-cycloalkyl-p-chloroacetopheone derivatives, there is no strict requirement for the hydrogen being abstracted to be in the plane of the carbonyl oxygen 11 orbital, and n and A, paticularly the former, can vary quite considerably from its optimum values of 0° and 90°. These results indicate that the deviation of the geometric factors from the ideal values may reduce the the hydrogen abstraction rate, but only to a certain extent. ' The disappearence of 1,3-aryl shift products for these ketones in solid state supports the suggestion that the charge transfer quenching requires a geometry as mentioned before for a maximum orbital overlap of the aryl group and oxygen. The solid state conformations of the ketones are such that the interaction between the aryl 11 electrons and the oxygen n orbital is unlikely. Interestingly, a-mesitylpropiophenone 5 forms only one of the isomeric indanols, the Z isomer. The Z:E ratio in cyclohexane is 5.1:1. Apparently, the biradical formed in solid state is too restrained to rotate to give the E isomer. 172 II. p-Arylpropiophenone Derivatives It has been known for a number of years that aromatic rings can deactivate nut" carbonyl triplets by a charge transfer mechanism. The process van be very effieient when it takes place intramolecularly as illustrated in the case of p-phenylpropiophenones.68 Detailed time-resolved studies of the R1 R3 Ph OH Figure 67 transient photoprocess in the photochemistry of various ring substituted p-phenylpropiophenones have been published recently.69 However, in all of those studies, no formation of photoproducts has been reported. We have for the first time found out the formation of substituted 1,2,3,4-tetrahydro-2-naphthols from several p-arylpropiophenones 1841 upon irradiation (Reaction 16). The product formation is quenched by typical triplet quencher such as 2,5-dimethyl-2,4-hexadiene. The triplet lifetimes and the quantum yields of product formation in various solvents are listed in Table 16 and 17 respectively. The reaction is believed to be via a 1,6-biradical generated from long range e-hydrogen abstraction of the triplet ketones (Figure 67). Based upon the consideration of the geometric parameters defined before, the conformation in Figure 68 is believed to be the best conformation 173 for the e-hydrogen abstraction. This conformation happens to be one of the energy-minimized conformations of the p-arylpropiophenones, the A type copnformations. Figure 68 The triplet lifetimes of the ketones are rather insensitive to Cit-methylation, or the methylation of the p-ring. Scaiano°9 has shown that the rate of intramolecular charge transfer quenching is mainly controlled by the molecular motion to achieve the critical geometry. It is like a intermolecular quenching process which is controlled by the diffusion rate in a given solvent. Introduction of a cat-methyl group or a methyl group on the p-ring does not alter the rate of molecular motion substantially, which is in turn reflected by the similar triplet lifetimes for these ketones. Although the triplet lifetimes of the ketones are not affected by the car-methylation, the quantum yield of the product formation is increased about 10 times by the addition of a methyl group at the can-carbon, or by changing from an o-tolyl group to a mesityl group at the p-carbon. The quantum yield is directly associated with the population of the molecules in 174 the conformation accessible for the hydrogen abstraction in terms of the reaction rate constant. The rate constant for the reaction equals the intrinsic rate constant multiplied by the percentage population of the suitable conformation. So the hydrogen abstration rate is expected to be sensitive to any conformational change. If an excited state equilibrium is assumed between different conformers of the ketones, the quantum yield can be expressed as follows, CD = k1 = X(r)kr‘t (28) where X(r) is the percentage population of the reacting conformer, kr is the intrinsic rate of the reacting conformer, k is the observed rate constant, 1 is the triplet lifetime. An increase in X(r) will raise the quantum yield for the product formation. The observed rate constant can then be calculated from the measured quantum yields and lifetimes, k = er(r) = <— 19A 19A' Figure 69 Our molecular mechanics calculations suggest that the cat-methylation lowers the energy of the A type conformations relative to other calculated conformations. This result is understandable in the following sense. The aryl groups in the A type conformations are anti to the d-substutent, and they are gauche to the d-substutent in the 6 type conformations. For ketone 19 an 21 with a d-methyl group, the aryl groups prefer the anti arrangement more than for ketone 18 and 20 having no or -substutent. Since A type conformations are responsible to the s-hydrogen abstraction, the k of e-hydrogen abstraction and the quantum yield of the product formation are enchanced dramatically by the cat-substitution. It is noticed that there is an aproximately ten fold increase of quantum yield from p-(o-tolyl)isobutyrophenone 18 to p-mesitylisobutyrophenone 20 in benzene or benzene with 2M dioxane. This corresponds to a eighteen fold increase in the k value (Table 23). The same type of conformational arguments as used by Wagner3S can be used to account for the observation. 176 As Wagner has pointed out, the enchancement of 5-hydrogen abstraction rate from a-(o-tolyl)acetophenone 15 to a-mesitylacetophenone 16 is in part due to the fact that a-mesitylacetophenone 16 does not have an unreactive conformation with regard to the orientation of the a-aryl group like a-(o—tolyl)acetophenone 15. It is believed that we have a similar case here with these p-arylpropiophenones. There are two factors affecting the k of the reaction. An increase in the biradical stability will speed up the reaction by making a larger 1‘1" A factor of 2 can thus be attributed to the inductive stablization of the benzyl radical by the additional two methyl group°5r102 on the p-ring in the 1,6-biradical. The remaining factor of nine is due to the conformational effect, i.e. changes of X(r). Molecular mechanics calculations indicate that p-(o-tolyl)isobutyrophenone 19 has two conformations with different orientations of the tolyl group, 19A and 19A' (Figure 69). Conformation 19A can undergo the e-hydrogen abstraction directly, but conformation 19A' has to rotate to 19A in order to react. The calculations also suggest that conformation 19A' is the more stable one of the two conformations, which are in an excited state equilibrium prior to the reaction. The reaction rate is proportional to the population of 19A. With p~mesitylisobutyrophenone 21, there is only one possible arrangement concerning the orientation of the mesityl group, 21 A, which makes the reacting conformation for the ketone. The population of the reacting conformer is thus enchanced, .and so are the k and qantum yield of product formation. If it is assumed that the replacement of a o-tolyl group by a mesityl group does not alter the relative population of other unconcerned conformers, the following equations can be used to estimate the relative concentration of conformation 19A and 19A', where K is the equilibrium constant between the two conformations, 177 [19A] + [19A'] = [21A] (30) [21A] = 9x[19A] (31) 50, [19A'] = 8x[19A] or K = [19A']/[19A] = 8 (32) The quantum yields for the product formation increase ca. 5 times in protic solvents such as methanol. Wagner27c has reported a solvent specific photoreaction from p-naphthyl y-dimethylaminopropyl ketone. The most significant aspect of the photochemistry of this ketone is that methanol allows the lowest triplet to react with a moderate efficiency. In all the solvents, a charge transfer complex is formed. immediately upon irradiation, but only in methanol, the complex rearranges to the 1,4-biradical. The biradical is formed with the help of an external protonation of the partially negative oxygen from methanol. . Our studies of p-arylpropiophenones reveal similiar acid-catalysis in the reaction. The fact that dioxane does not enchance the the quantum yields eliminates the possibility that methanol makes the reaction more efficient by preventing the reverse hydrogen transfer from occuring, because dioxane is known to have the same capability. The enhancement of product formation in methanol therefore has to arise from a different mechanism. The most likely alternative is that a proton transfer in the charge transfer complex can occur in methanol to generate the same biradical as what is given by a direct hydrogen atom transfer from a ketone triplet.°sr101 However, since acetonitrile does not affect the quantum yields, it can not be a simple proton transfer through a Charge-separated geometry or a solvated radical-ion pair dissociated from the complex, which can be stablized by methanol. Instead, 178 protonation of the negative oxygen in the complex by methanol must be responsible. So it is concluded that direct e-hydrogen abstraction competes with the charge transfer quenching of the triplet excited ketones in all the solvents, and in methanol, a good portion of the biradical is formed from the charge transfer complex via an external protonation of the oxygen in the complex by methanol (Scheme 37). 11V methanol .p Scheme 37 III. Derivation of Equation (25) 179 Derivation of Stern-Volmer Equation for or-Mesitylvalerophenone 6 Let A=[6(3], B=[6E], °=k5A/(kd'A+k5A+kdB+kctB) From steady state assumption, kiA+X(6E)I=k_iB+kdB+kctB =kd'A+k5A+kdB+kctB, I = amount of light absorbed So, kiA+X(6E)(kd'A+k5A+kdB+kctB)=k,iB+kdB+kctB A=[k_iB+(1-X(6E))(kdB+kctB)] / [ki+X(6E)(kd'+k5)] =(1+A[Q]+B[Q]2)/(1 +CIQI) .. _ 2 - _ A—qu/M, B—kq /M, C-kq(k5 X(6E)k5)/N L=kd'+k5 +k_i+kd+kct+ki M=k,ik5 +l is 0.33108 for acetophenone, and 0.01643 a for o-methylacetophenone, 187 I = [Ari/0.33 ’ (36) or I = [ml/0.016 (37) The response factors for each photoproduct on 6C or HPLC were obtained by the following equation, Rf = (M°1°5Photo/ MOIQSSthAStd/Aphoto) (38) These response factors are presented in Appendix. G. Mehtods Used for Product Isolation All the photoproducts were isolated either with a Varian Aerograph 900 Gas Chromatogram equipped with a 20% 5E-30 column and a thermal conductivity detector or a AN ALTECH preparative thin layer silica gel plate. H. Spectroscopic Measurements 1H NMR spectra were recorded on either a Varian T-60 or a Bruker WM-250 Fourier Transform Spectrometer.13C NMR spectra were recorded on the Bruker WM-250 instrument. Infrared spectra were recorded on a Perkin-Elmer 599 IR Spectrometer. Ultraviolet-visible spectra were recorded on either a Varian Carey 219 or a Shimadzu UV-160 Spectrometer. Mass spectra were recorded on a Finnigan 4000 GC/ MS. Phosphorescence spectra were recorded on a Perkin-Elmer MPF-44A Fluorescence Spectrometer. 188 III. Preparation of Starting Ketones or-(o-Tolyl)-p-Methoxyacetophenone108 - a-(o-Tolyl)acetic acid (Aldrich, 12.0 g, 0.080 mole) in phosphorus trichloride (MC/ B, 11.4 g, 0.083 mole) was heated at 70-80°c for 2 hr. The mixture was cooled and mixed with anisole (60 ml). The resulting solution was added to anhydrous aluminium chloride (MCB, 11.4 g, 0.085 mole) in anisole (30 ml) at 0°C. The mixture was stirred at r.t. for 15 min until all the aluminium chloride had dissolved and then heated at 75°C for 2 hr. After cooling, it was poured into iced aqueous hydrochloric acid (38%). The aqueous phase was separated and extracted with a mixture of benzene and ether (1:1, 2xlSO ml). The extracts were washed with saturated sodium bicarbonate solution and distilled water, and dried over sodium sulfate. The solvent was evaporated. The crude product was recrystallized from ethanol to give the pure product as colorless crystal (10.8 g, 56.3% yield).m.p. 76.0-77.2°C 1H NMR (250 MHz, CDC13) 2.27 (s, 3H, ArCI-I3), 3.87 (s, 3H, OCT-I3), 4.26 (s, 2H, ArCHz), 6.84807 (m, 8H, ArH) ‘ 13C NMR (250 MHz, CDC13) 19.69, 43.02, 55.34, 113.70, 125.96, 126.98, 129.85, 130.12, 130.20, 13053, 133.78, 136.87, 163.43, 195.95 ' MS 240 (Mt), 135 (base), 105,91, 77 IR (CO4) 3080-2860, 1685 (C=O), 1605, 1512, 1465, 1262, 1170 <:1«-(o-Tolyl)propiophenone109 - A solution of or-(o-tolyl)acetophenone (10.0 g, 0.048 mole) in dry tolune (40ml) was added to a suspension of sodium hydride (Aldrich, 80% dispension in mineral oil, 1.4 g, 0.047 mole) in dry tolune (120 ml), and the mixture was refluxed for 1 hr. The solution was cooled, and methyl iodide (Baker, 20.0 g, 0.142 mole) was introduced at 25°C. 189 The mixture was refluxed for 12 hr, then cooled and filtered. The filtrate was diluted with ether (150 m1), then washed with distilled water, and dried over sodium sulfate. The. solvent was evaporated. Distillation of the residue gave the ketone, which was then recrystallized from ethanol as colorless crystal (6.2 g, 58.1% yield). m.p. 46.5-47.S°C. 1H NMR (250 MHz, CDCl3) 1.48 (d, 1:7.3 Hz, 3H, MH%), 2.50 (s, 3H, ArCH3), 4.76 (q, #73 Hz, 1H, ArCflCH3), 7.05-7.85 (m, 9H. ArH) 13C NMR (250 MHz, CDC13) 17.72, 19.22, 44.21, 126.44, 126.57, 128.14, 128.20, 130.68, 132.29, 134.21, 136.25, 136.61,139.87, 200.42 MS 224 (M+), 119, 105 (base), 91, 77 IR (CC14) 3080-2860, 1693 (C=O), 1608, 1498, 1453, 1335, 1230 d-(o-Tolyl)valerophenone - d-(o-Tolyl)aCetophenone (7.0 g, 0.033 mole) in dry tolune (30 ml) was added to a suspension of sodium hydride (Aldrich, 80% dispension in mineral oil, 1.0 g, 0.033 mole) in dry tolune (80 ml), and the mixture was refluxed for 1 hr. The solution was cooled, and propyl bromide (Baker, 8.1 g, 0.066 mole) was introduced at 25°C. The mixture was refluxed for 24 hr, then cooled and filtered. The filtrate was diluted with ether (150 ml), then washed with distilled water, and dried over sodium sulfate." The solvent was evaporated. The crude product was purified by column chromatography with 40% benzene in hexane as eluent. The same purification procedure was repeated two more times to obtain the product as colorless liquid (4.0 g, 48.1% yield). 1H NMR (250 MHz, CD03) 0.94 (t, 1=7.7 Hz, 3H, (CH2)2CH3), 1.23-7.09 (m, 4H, (CH2)2CH3), 2.01 (s, 3H, ArCH3), 4.42 (dd, 11=7.8 Hz, 12.-.57 Hz, 1H, ArCHPr), 7.07-7.86 (61,911, ArH) 13C NMR (250 MHz, CDC13) 14.02, 19.60, 20.95, 35.65, 49.25, 126.37, 126.57, 190 126.96, 128.05, 128.22, 130.69, 132.36, 134.70, 137.12, 138.37, 200.17 MS 252 (M+), 210, 147, 131, 117, 105 (base), 91, 77 IR 3065-2875, 1690 (C=O), 1603, 1495, 1455, 1252, 1230 on-(o-Tolyl)isobutyrophenone - Potassium (6.0 g, 0.154 mole) was dissolved in dry t-butyl alcohol (Baker, 150 ml). d-(o-Tolyl)acetophenone (7.0 g, 0.033 ml) was added as solid. The mixture was refluxed for 4 hr. Methyl iodide (Baker, 6.8 g, 0.048 mole) was added at r.t.. The content was refluxed for 8 hr. Second portion of methyl iodide (6.8 g, 0.048 mole) was introduced after cooling, and it was refluxed for another 4 hr. The mixture was filtered at r.t., and the filtrate was diluted with ether (150 ml), washed with distilled water, and dried over sodium sulfate. After evaporation of solvent, the mixture of product and starting material was treated with sodium hydride (Aldrich, 80% dispension in mineral oil, 1.0 g, 0.033 mole) and methyl iodide (6.8 g, 0.048 mole) in toluene (140 ml) using the procedure described for the preparation of d-(o-tolyl)propiophenone. The crude product was first distilled under vacuum, and then the portion collected at 106° / 1 torr was purified several times by column Chromatography with 20% benzene in hexane to afford the pure product as colorless liquid (1.5 g, 19% yield). 1H NMR (250 MHz, CDC13) 1.67 (s, 6H, macaw), 2.07 (s, 3H, ArCH3), 7.03-7.67 (m, 9H, ArH) 13c NMR (250 MHz, CDC13) 20.33, 27.51, 51.44, 124.45, 126.59, 126.76, 127.79, 129.09, 132.01, 132.12, 135.46, 135.90, 143.85, 203.90 M5 238 (M+), 223, 133, 115, 105 (base), 91,77 IR 3080-2885, 1692 (C=O), 1605, 1475, 1458, 1250, 1175 cr-Mesitylpropiophenone 191 a-Mesitylpropiophenone was prepared by the reaction of phenyl magnisium bromide with ot-mesitylpropionitrile following the route given below. NaCN LDA ) ——> CH2 Cl DMSO CH2 CN MeI, THF 0 1) PhMgBr, Ether - k \quCN 2) HCl, H20 Ph CH3 g-Mesitylacetonitrile - A mixture of sodium cyanide (Fisher, 8.7 g, 0.189 mole) and dimethyl sulfoxide (100 ml) was heated at 80°C until all of the sodium cyanide had dissolved. 2,4,6-Trimethylbenzyl chloride (Aldrich, 20.0 g, 0.119 mole) was added to this solution. The mixture was stirred at this temperature overnight. It was then cooled to r.t. and poured into distilled water (300 ml). The resulting solution was extracted with ether (2x150 ml). The ether layers were combined, washed with distilled water, and dried over sodium sulfate. The solvent was removed to afford a-mesitylacetonitrile as a brown solid (17.4 g, 92% yield). The crude product was used without further purification. 1H NMR (60 MHz, CDC13) 2.30 (s, 3H), 2.38 (s, 6H), 3.60 (s, 2H), 6.92 (s, 2H) g-Mesitylpropionitrile - Diisopropylamine (Aldrich, 10.8 g, 0.107 mole) in dry THF (70 ml) was added to n-butyl lithium (Aldrich, 2.5 M in hexane, 45 192 ml, 0.115 mole) at 0°C. The mixture was stirred for 15 min, and then cooled to -78°c with a dry-ice/ acetone bath.110 a-Mesitylacetonitrile (17.4 g, 0.109 mole) in dry THF (140 ml) was added. The content was warmed to r.t., and stirred for 2 hr. Methyl iodide (baker, 16.9 g, 0.119 mole) was added. The mixture was stirred at r.t. for another 2 hr, and then refluxed overnight. The solution was cooled and the solvent was removed. Ether (150 ml) and distilled water (150 ml) was added to the residue, and then separated. The aqueous phase was extracted with ether (2xlSO ml). The combined ether layers were washed with distilled water, dried over sodium sulfate. Evaporation of the solvent gave the product as a brown liguid (18.2 g, 97% yield), which was used without further purification. 1H NMR (60 MHz, CDC13) 1.55 (d, 3H), 225 (s, 3H), 2.42 (s, 6H), 4.23 (q, 1H), 6.83 (s, 2H) ' g-Mesiglpropiophenone - Bromobenzene (Fisher, 17.3 g, 0.110 mole) in anhydrous ether (100 ml) was added to magnisium shavings (MC/ B, 10.0 g, 0.411 mole) in anhydrous ether (50 ml) activated with small amount of 1,2-dibromoethane under nitrogen atomsphere at r.t.. The mixture was refluxed for 3 hr. q-Mesitylpropionitrile (18.2 g, 0.105 mole) in anhydrous ether (150 ml) was added. The mixture was refluxed overnight, and then cooled. The solid was collected by filtration, to which aqueous hydrochloric acid (19%) was added. The solution was refluxed for 10 hr. After cooling, it was extracted with ether (2xZOO ml). The ether extracts were combined, washed with saturated aqueous sodium bicarbonate solution and dried over sodium sulfate. The ether was removed to give a dark brown solid. The crude product was Chromatographed on silica gel using 40% benzene in hexane as the eluent, and then recrystallized from ethanol (10.2 g, 39% yield). m.p. 76.5-77.5°c. 193 1H NMR (250 MHz, CDC13) 1.48 (d, 1:7.3 Hz, 3H, MH%), 2.11 (s, 3H, p-Mes-CHg), 2.16 (s, 6H, o-Mes-CH3), 4.50 (q, 1:73 Hz, 1H, ArCl;i_CH3), 6.78-7.73 (m, 7H, ArH) 13C NMR (250 MHz, CDC13) 14.96, 20.36, 20.63, 45.74, 128.14, 130.23, 132.34, 13532, 136.00, 136.79, 202.30 MS 252 (M+), 147 (base), 105,91, 77 IR (C614) 3100-2890, 1693 (C=O), 1602, 1488, 1455, 1325, 1230, 1187 q-Mesitylvalerophenone d-Mesitylvalerophenone was prepared by the reaction of phenyl magnisium bromide with d-Mesitylvaleronitrile. Witylvaleronitrile - d-Mesitylvaleronitrile was synthesized by alkylation of a-mesitylacetonitrile with propyl bromide. (Aldrich) following the same procedure described for a-mesitylpropionitrile. The crude product (90% yield) was used for the next reaction without further purification. 1H NMR (60 MHz, CDCl3) 1.02 (t, 3H),1.37-2.14(m, 4H), 226 (s, 310,242 (5, 6H), 4.14 (dd, 1H), 6.87 (s, 2H) I g-Mesitylvalerophenone - This ketone was prepared by the reaction of phenyl magnisium bromide with a-mesitylvaleronitrile following the same procedure described for a-mesitylpropiophenone. The crude product was purified by chromatography, - with 30% benzene in hexane, and then recrystallized from ethanol as white crystal (45% yield). m.p. 61.8-63.0°C. 1H NMR (250 MHz, CDC13) 0.97 (t, 1=7.3 Hz, 3H, (CH2)ZCH3), 1.25-254 (m, 4H, (CHZ)ZCH3), 2.19 (s, 3H, p-Mes-CH3), 2.28 (s, 6H, o-Mes-CH3), 4.42 (dd, 11:73 Hz, 12:47 Hz, 1H, ArCLIPr), 6.78-7.76 (m, 7H, ArH) 13C NMR (250 MHz, c1303) 14.40, 20.61, 20.79, 21.45, 32.66, 50.97, 128.04, 194 128.14, 130.27, 130.32, 132.20, 135.84, 135.89,137.56, 201.58 MS 280 (M+), 175, 133 (base), 105,91, 77 IR (CO4) 3060-2875,.1689 (C=O), 1602, 1485, 1453, 1253,1215 or-Mesitylisobutyrophenone a-Mesitylisobutyrophenone was prepared by the reaction of phenyl magnisium bromide with a-mesitylisobutyronitrile following the route given below. NaCN LDA p > CH2 Cl DMSO ' CH2 CN MeI, THF LDA > CN CH CN MeI, THF CH3 0 1) PhMgBr, Ether » |\ Ph 2) HCl, H2 0 g-Mgsitylisgbutyrgnitrilg - Diisopropylamine (Aldrich, 12.3 g, 0.122 mole) in dry THF (80 ml) was added to n-butyl lithium (Aldrich, 2.5 M in hexane, 47 ml, 0.118 mole) at 0°C. The mixture was stirred for 15 min. d-Mesitylpropionitrile (20.0 g, 0.115 mole) in dry THF (160 ml) was added 195 after it was cooled to -78°c with a dry-ice/ acetone bath. The content was warmed to r.t., and stirred for 2 hr. Methyl iodide (Baker, 16.5 g, 0.116 mole) was added and the mixture was stirred at r.t. for another 2 hr, and then refluxed overnight. The solution was cooled and the solvent was removed. Ether (150 ml) and distilled water (150 ml) was added to the residue, and then separated. The aqueous phase was extracted with ether (2x150 ml). The combined ether layers were washed with distilled water, dried over sodium sulfate. Evaporation of the solvent gave the product as a dark brown liguid (21.0 g, 90.5% yield), which was used without further purification. 1H NMR (60 MHz, CDC13) 1.94 (s, 6H), 228 (s, 3H), 256 (s, 6H), 6.86 (s, 2H) g-Mesitylisobutyrophenone - a-Mesitylisobutyrophenone was prepared by the reaction of phenyl magnisium bromide made in ether with d-mesitylisobutyronitrile in benzene following the same procedure described for ot-mesitylpropiophenone. Hydrolysis with aqueous hydrochloric acid (19%) for 80 hr and normal work-up afforded the crude product, which was then purified by Chromatography with 40% benzene in hexane and recrystallization from ethanol to give the pure ketone as white crystal (41.2% yield). m.p. 64.5-66.0°C. 1H NMR (250 MHz, my 1.72 (s, 6H, ArC(%)fi 223 (s, 3H, p-Mes-CH3), 2.30 (s, 6H, o-Mes-CH3), 6.77-7.74 (m, 7H, ArH) 13C NMR (250 MHz, CDC13) 20.30, 23.60, 28.29, 53.28, 127.87, 129.38, 132.07, 132.12, 135.38, 135.55, 135.95, 139.37, 203.95 MS 266(M+), 251, 236, 161 (base), 133, 121, 105, 91, 77 IR (CO4) 3070-2870, 1686 (C=O), 1600, 1480, 1455, 1245, 1166 cr-Mesityl-ot-Phenylacetophenone111 - Desyl Chloride (Aldrich, 10.0 g, 0.043 mole) in mesitylene (Aldrich, 30 ml) was added to anhydrous 196 aluminum chloride (MCB, 9.0 g, 0.067 mole) in mesitylene (10 ml). The mixture was heated at 45—50°c for 4 hr, and then poured into iced aqueous hydrochloric acid (38%) after being cooled. The aqueous phase was extracted with ether. The extracts were washed with saturated sodium bicarbonate solution and dried over sodium sulfate. After evaporation of the solvent, the crude product was recrystallized from ethanol to give pure colorless crystal (7.3 g, 53.4% yield). m.p. 112.5-113.5°c. 1H NMR (250 MHz, CDC13) 2.19 (s, 6H, o-Mes-CH3), 2.28 (s, 3H, p-Mes-CH3'), 5.99 (s, 1H, ArHPh), 6.89-7.93 (m, 12H, ArH) 13C NMR (250 MHz, c003) 20.63, 21.05, 56.62, 126.55, 127.99, 128.19, 128.57, 129.30, 130.20, 132.54, 133.22, 136.66, 136.84, 137.00, 137.08, 199.63 MS 314(M+), 209 (base), 105,91, 77 IR (CO4) 3090-2860, 1697 (C=O), 1603, 1500, 1452, 1210 or-Mesityl-o:-Phenyl-p-Cyanoacetophenone a-Mesityl-ot-phenyl-p-cyanoacetophenone was prepared by the reaction of d-chloro-on-phenyl-p-cyanoacetophenone with mesitylene following the route given below. gPhenyl-EHuoroacetophenone - a-Phenylacetic acid (Aldrich, 25.0 g, 0.184 mole) in phosphorus trichloride (MC/ B, 40.0 g, 0.291 mole) was heated at 70-80°c for 3 hr. Exess phosphorus trichloride was distilled. The residue was mixed with fluorobenzene (Aldrich, 80 ml), and was added to aluminium Chloride in (MCB, 33.0 g, 0.246 mole) in fluorobenzene (80 ml). The mixture was stirred for 2 hr at r.t. and then heated at 50-60°c for 3 hr. The reaction mixture was poured over ice after cooling. The aqueous phase was extracted with ether (2x200 ml). The extracts were washed with saturated 197 sodium bicarbonate solution and dried' over sodium sulfate. The solvent were evapored. The crude product was used for the next reaction without further reaction (23 g, 58.4% yield). 1H NMR (60 MHz, CDC13) 4.24 (s, 2H), 7.07-8.06 (m, 9H) 0 O PhF K > so2 C12 0 NaCN 4:1; - DMSO CN mesitylene AlCl3 g-Phenyl-gCyanoacetophenone - Sodium cyanide (Fisher, 6.0 g, 0.122 mole) and dimethyl sulfoxide (100 ml) was heated at 80°C until all of the CN sodium cyanide had dissolved. a-Phenyl-p-fluoroacetophenone (23 g, 0.107 mole) was added. The mixture was heated at 120°C overnight. After cooling, it was poured into distilled water (300 ml) The aqueous phase was extracted with ether (2x150 ml). The extracts were washed with distilled water, and dried over sodium sulfate. After the solvent was evapored, the_residue was distilled at reduced pressure to afford the product (7.0 g, 29.6% yield) as 198 yellowish solid. 1H NMR (60 MHz, CDC13) 4.31 (s, 2H), 7.20-8.06 (m, 9H) g.-Chloro-g;;-Phenyl-p-Cyanoacetophenone112 - Sulfuryl chloride (MC/ B, 4.2 g, 0.031 mole) was added to well grounded a-phenyl-p- cyanoacetophenone (6.0 g, 0.027 mole) at r.t.. The addition was slow enough not to warm up the mixture. The mixture was stirred at r.t. for 5 hr with a mechanic stirrer, and then dissolved in benzene (100 ml). The organic phase was washed with distilled water, and dried over sodium sulfate. The solvent was evapored. The crude product, which contained 15% dichlorinated product, was used for the next reaction without further purification (7.0 g). 1H NMR (60 MHz, CDC13) 6.25 (s, 1H), 7.35-8.06 (m, 9H) g-Mesityl-g-Phenyl-p-Cyanoacetophenong - d-Chloro-d-phenyl-p- cyanoacetophenone (7.0 g, crude) in mesitylene (Aldrich, 20 ml) was added to anhydrous aluminium Chloride (MCB, 5.6 g, 0.042 mole) in mesitylene (8.0 ml). The mixture was heated at 50-60°c for 7 hr, and then poured into iced aqueous hydrochloric acid (38%) after being cooled. The aqueous phase was extracted with methylene chloride (2xlOO ml). The extracts were washed with saturated sodium bicarbonate solution and dried over sodium sulfate. Evaporation of the solvent afforded a dark colored solid, which washed with - hexane and ethanol. The crude product was recrystallized from a mixture of ethanol and chloroform to give the pure product (2.2 g). m.p. 159.0-160.0°c. 1H NMR (250 MHz, CDC13) 217 (s, 6H, o-Mes—CH3), 228 (s, 3H, p-Mes-CH3), 5.90 (s, 1H, ArHPh), 6.88-7.90 (m, 11H, ArH) 13C NMR (250 MHz, CDC13) 20.70, 21.00, 56.97, 115.74, 117.79,-126.97, 128.17, 128.58, 129.28, 130.46, 132.13, 135.82, 136.75, 137.34, 140.09, 198.60 MS 339 (M+), 209 (base), 130, 102, 91, 77 IR (CC14) 3095-2870, 1700 (C=O), 2230 (CN), 1614, 1502, 1456, 1298, 1210 199 on-Mesityl-d-Phenyl-p-Methoxyacetophenone a-Mesityl-o:phenyl-p-methoxyacetophenone was prepared from a-mesityl-q-Phenylacetic acid and benzene. g-Mesityl-g-Phenylacetic acid - Stannic chloride (Alfa, 68.5 g, 0.263 mole) was added slowly to a solution of mandelic acid (20.0 g, 0.131 mole) in mesitylene (Aldrich, 100 ml) at 65-70°c. The resulting solution was stirred for 6 hr at this temperature, and it was decomposed with ice water after cooling. The mixture was extracted with ether (3x300 ml). The extracts were washed with distilled water and dried over sodium sulfate. Evaporation of solvent afforded the crude product, which was then recrystallized from a mixture of hexane and chloroform (36.7 g, 54.9% yield). . 1H NMR (60 MHz, CDC13) 2.09 (s, 6H), 225 (s, 3H), 5.45 (s, 1H), 6.92-7.25 (m, ArH), 10.25 (s, 1H) g-Mesityl-g -Phenyl-p-Methoxyacetophenone - d-mesityl-or -Phenyl- acetic acid (5.0 g, 0.020 mole) in phosphorus trichloride (MC/ B, 6.3 g, 0.046 mole) was heated at 70-80°c for 2 hr. The mixture was cooled and mixed with anisole (20 ml). The resulting solution was added to anhydrous aluminium chloride (MCB, 3.0 g, 0.022 mole) in anisole (5.0 ml) at 0°C. The mixture was heated at 75°C for 3 hr. After cooling, it was poured into iced aqueous hydrochloric acid 1 (38%). The aqueous phase was separated and extracted with a mixture of benzene and ether (1:1, 2xlSO ml). The extracts were washed with saturated sodium bicarbonate solution and distilled water, and dried over sodium sulfate. The solvent was evapored. The crude product was purified by column chromatography with 7.5% ethyl acetate in hexane and recrystallization fromiethanol (3.0 g, 47.8% yield). m.p. 96.4-98.5°C. 1H NMR (250 MHz, CDC13) 2.18 (s, 6H, o-Mes-CH3), 227 (s, 3H, p-Mes-CH3), 200 3.80 (s, 3H, OCH3), 5.92 (s, 1H, ArCHPh), 6.80-7.84 (m, 11H, ArH) 13C NMR (250 MHz, c003) 20.69, 21.12, 55.14, 56.44, 113.42, 126.49, 127.99, 12935, 130.07, 130.20, 130.50,133.67, 136.60, 136.91, 137.37, 162.97, 198.25 MS 344 (W), 209, 135 (Base), 107,91, 77 IR (C04) 3090-2840, 1690 (C=O), 1600, 1514,1460, 1313, 1265, 1216,1175 q-Mesityl-d-Phenyl-2,4,6-Trimethylacetophenone - cat-Mesityl- oz-phenylacetic acid (10.0 g, 0.037 mole) in phosphorus trichloride (MC/ B, 15.7 g, 0.114 mole) was heated at 70-80°c for 3 hr. The mixture was cooled and mixed with mesitylene (Aldrich, 8 ml). The resulted solution was added to anhydrous aluminium chloride (MCB, 6.0 g, 0.045 mole) in a mixture of mesitylene (8.0 ml) and carbon disulfide (Mallinckrodt, 16 ml) at 0°C. The mixture was refluxed for 2 hr. After cooling, it was poured into iced aqueous hydrochloric acid (38%). The aqueous phase was separated and extracted with a mixture of benzene and ether (1:1, 2xlSO ml). The extracts were washed with saturated sodium bicarbonate solution and distilled water, and dried over sodium sulfate. Evaporation of solvent, purification by column Chromatography with 30% benzene in hexane, and recrystallization from ethanol and chloroform afforded the product as white crystal (5.7 g, 43.3% yield). m.p. 161.0-162.0 °C 1H NMR (250 MHz, CDCl3) 1.93 (s, 12H, o-Mes-CH3), 227 (s, 6H, p-Mes-CH3), 5.98 (s, 1H, ArCHPh), 6.73 (s, 2H, ArH), 6.81 (s, 2H, ArH), 7.24-7.37 (m, 5H, ArH) 13C NMR (250 MHz, CDC13) 18.42, 20.67, 20.93, 57.51, 126.14, 127.64, 128.22, 128.37, 129.26, 130.22, 133.70, 137.16, 138.22, 138.54, 139.45, 204.48 MS 356 (M+), 209, 147 (base), 119, 103, 91, 77 201 IR (CC14) 3090-2860, 1705 (C=O), 1615, 1506, 1458, 1235, 1161 d-Mesityl-2,4,6-Trime thylacetophenone a-Mesityl-2,4,6-trimethylacetophenone was synthesized from d-mesitylacetic acid and mesitylene. g-Mesitylacetic aeid113 - A mixture of a-mesitylacetonitrile (37.0 g, 0.172 mole) and potassium hydroxide (Baker, 27.0 g, 0.481 mole) in ethylene glycol (Baker, 340 ml) was heated at 155°C for 6 hr. After cooling, the solution was acidified with aqueous hydrochloric acid (38%). The solid was filtered, washed with distilled water, and recrystallized from acetone to afford the acid (23.6 g, 96.6% yield). 1H NMR (60 MHz, c003) 2.22 (s, 3H), 2.28 (s, 6H), 3.64 (s, 2H), 6.82 (s, 2H) d—MesiLil-2,4,6-Trimethylacetophenone114 - d-Mesitylacetic acid (10.0 g, 0.056 mole) in phosphorus trichloride (MC/ B, 31.0 g, 0.226 mole) was heated at 70-80°c for 3 hr. The mixture was cooled and mixed with mesitylene (Aldrich, 5 ml). The resulting solution was added to anhydrous aluminium chloride (MCB, 12.5 g, 0.094 mole) in a mixture of mesitylene (15.0 ml) and carbon disulfide (Mallinckrodt, 20 ml) at 0°C. The mixture was refluxed fOr 15 hr. After cooling, it was poured into iced aqueous hydrochloric acid (38%). The aqueous phase was separated and extracted with a mixture of benzene and ether (1:1, 2xlSO ml). The extracts were washed with saturated sodium bicarbonate solution and distilled water, and dried over sodium sulfate. Evaporation of solvent and recrystallization from methanol afforded the product as white crystal (8.5 g, 54.2% yield). m.p. 91.0-92.5°C. 1H NMR (250 MHz, CDC13) 2.16 (s, 6H, o-Mes-CH3), 2.20 (s, 6H, o-Mes—CH3), 2.25 (s, 3H, p-Mes-CH3), 2.27 (s, 3H, p-Mes-CH3), 4.07 (s, 2H, ArCHz), 6.81 (s, 202 2H, ArH), 6.86 (s, 2H, ArH) 13c NMR (250 MHz, CDCl:,) 19.11, 20.39, 20.76, 20.89, 45.89, 127.43, 128.44, 128.99, 132.67, 136.42, 137.22, 138.16, 139.40, 206.08 MS 280 (M+), 147 (base), 133, 119, 91, 77 IR (C(14) 3010-2870, 1710 (C=O), 1620, 1490, 1455, 1262 a-Mesityl-o-Methylacetophenone - o-Bromotoluene (Aldrich, 12.0 g, 0.070 mole) in anhydrous ether (100 ml) was added to magnisium shavings (MC/ B, 6.8 g, 0.280 mole) in anhydrous ether (50 ml) activated with small amount of 1,2-dibromoethane under nitrogen atomsphere at r.t.. The mixture was refluxed for 3 hr. d-Mesitylacetonitrile (11.0 g, 0.069 mole) in anhydrous ether (100 ml) was added. The mixture was refluxed overnight, and then cooled. The solid was collected by filtration, to which aqueous hydrochloric acid (19%) was added. The solution was refluxed for 10 hr. After cooling, it was extracted with ether (2x200 ml). The ether extracts were combined, washed with saturated aqueous sodium bicarbonate solution and dried over sodium sulfate. The ether was removed to give a dark brown solid. The crude proeuct was Chromatographed on silica gel using 30% benzene in hexane as the eluent, and then recrystallized from ethanol (6.5 g, 37.4% yield). m.p. 33.6-35°c. 1H NMR (250 MHz, CD03) 2.20 (s, 6H, o-Mes-CH3), 2.28 (s, 3H, ArCI-I3), 2.47 (s, 3H, ArCI-I3), 4.26 (s, 2H, ArCHz), 6.92-7.80 (m, 6H, ArH) 13C NMR (250 MHz, CDC13) 20.12, 20.79, 20.92, 42.23, 125.55, 127.82, 128.71, 129.15, 131.02, 131.78, 136.11, 136.58, 137.67, 138.27, 201.11 MS 252 (Mt), 133, 119 (base), 105, 91,77 IR (C04) 3100-2865, 1692 (C=O), 1615, 1485, 1458,1320, 1218 203 a-Phenyl-2,4,6-Trimethylacetophenone - a-Phenylacetic acid (Aldrich, 10.0 g, 0.073 mole) in phosphorus trichloride (MC/ B, 15.7 g, 0.114 mole) was heated at 70-80°c for 4 hr. The cooled mixture was mixed with mesitylene (Aldrich, 6 ml), and added to anhydrous aluminium chloride (MCB, 16.0 g, 0.120 mole) in a mixture of mesitylene (16.0 ml) and carbon disulfide (Mallinckrodt, 26 ml) at 0°C. The mixture was refluxed for 5 hr. After cooled, it was poured into iced aqueous hydrochloric acid (38%). The aqueous phase was separated and extracted with a mixture of benzene and ether (1:1, 2x150 ml). The extracts were washed with saturated sodium bicarbonate solution and distilled water, and dried over sodium sulfate. The solvent were evapored. The crude product was purified by column chromatography with 30.0% benzene in hexane and recrystallization from methanol at -30°c (7.0 g, 40.2% yield). 1H NMR (250 MHz, CDCl3) 2.12 (s, 6H, o-Mes-CH3), 229 (s, 3H, p-Mes—CH3), 4.00 (s, 2H, ArCHZ), 6.83-7.35 (m, 7H, ArH). 13c NMR (250 MHz, CDC13) 18.98, 20.86, 51.57, 126.87, 128.32, 129.69, 13255, 133.15, 138.27, 139.00, 207.21 Ms 238 (Mt), 147 (base), 119, 103, 91, 77 IR 3085-2820, 1704 (C=O), 1615, 1500, 1460, 1210, 1038 p-(o-Tolyl)propiophenone p-(o-tolyl)propiophenone was prepared by alkylation and acylation of t-butyl malonate with a-bromo-o-xylene and benzoyl chloride following the route given below.115 t-Butyl (o-Tolylmethylzmalonate - Sodium hydride (Aldrich, 80% dispension in mineral oil, 2.5 g, 0.083 mole) was added to t-butyl malonateu° 204 O m kor-Hu NaH Br. + D» ' [’JDt-Bu t-BuOH O O O L\\ 82 L\\O jt-Bu NaH, BzCl t-Bu .- . r: 17.-BU benzene rOt‘BU O O p-MePhSOZOH . )- acetic acid 0 (18.0 g, 0.083 mole) in t-butyl alcohol (Baker, 110 ml), and stirred at r.t. for 3 hr. a-Bromo-o—xylene (15 g, 0.081 mole) in t-butyl alcohol (40 ml) was added and stirred at 65°C for 2 hr. The mixture was cooled and diluted with distilled water. The organic phase was separated. The aqueous phase was extracted with ether (2x150 ml). The extracts were washed with distilled water and dried over sodium sulfate with small amount of potassium carbonate. After evaporation of the solvent, the crude product was used without further purification (24.0 g, 100% yield). 1H NMR (60 MHz, CDC13) 1.42 (s, 18H), 2.43 (s, 3H), 3.18 (d, 2H), 3.49 (t, 3H), 7.12 (s, 4H) . a-(o-Tolyl)propiophenone - Sodium hydride (Aldrich, 80% dispension in mineral oil, 3.3 g, 0.110 mole) was added to t-butyl (o-tolyl- 205 methyl)malonate (22.0 g, 0.075 mole) in bezene (450 ml), and stirred at 80°C for 4 hr. Benzoyl Chloride (Fisher, 10.9 g, 0.078 mole) in benzene (150 ml) was added . The mixture was stirred for another 4 hr. It was then cooled and the excess sodium hydride was decomposed by addition of p-toluenesulfonic acid monohydrate (Aldrich, 3.6 g). The salt was removed by filtration. After evaporation of solvent, the residue was refluxed with p-toluenesulfonic acid monohydrate (2.0 g) in glacial acetic acid (Mallinckrodt, 450 ml) containing acetic anhydride (Baker, 9 ml). The solution was cooled, poured over ice, and neutralized with 10% aqeous potassium hydroxide solution. The aqueous phase was extracted with ether (2x300 ml). The extracts were washed with distilled water, and dried over sodium sulfate. The solvent were evapored. The crude product was purified by vaccum distillation and recrystallization from ethanol to give the pure ketone as colorless crystal (5.0 g, 29.8%). m.p. 46.5-47.S°c. 1H NMR (250 MHz, CDC13) 2.35 (s, 3H, ArCH3), 3.07, 3.24 (A2B2, I=8.5 Hz, Ar(CH2)2), 7.11-7.99 (m, 9H, ArH) 13C NMR (250 MHz, c1303) 19.18, 27.32, 38.89, 126.03, 126.17, 127.88, 128.46, 128.58, 130.19, 13290, 135.79, 136.70, 139.23, 199.06 Ms 224(M+), 206, 119, 105 (base), 91, 77 IR 3100-2900, 1697 (C=O), 1606, 1500, 1455, 1210 p-(o-Tolyl)isobutyrophenone - Diisopropylamine (Aldrich, 15.2 g, 0.150 mole) in dry THF (100 ml) was added to n-butyl lithium (Aldrich, 2.5 M in hexane, 60 ml, 0.150 mole) at 0°C. The mixture was stirred for 10 min, and then cooled to -78°c with a dry-ice/ acetone bath. Propiophenone (Mallinckrodt, 19.0 g, 0.142 mole) was added. The content was stirred for 30 min, and a-chloro-o-xylene (Aldrich, 20.0 g, 0.142 mole) in dry THF (100 ml) 206 was added. The mixture was warmed to r.t., stirred for 2 hr, and then refluxed for 4 hr. The solution was cooled and the THF was removed. Ether (150 ml) and distilled water (150 ml) was added to the residue, and then separated. The aqueous phase was extracted with ether (2x150 ml). The combined ether layers were washed with distilled water, dried over sodium sulfate. The solvent was evaporated and the residue was distilled under reduced pressure to afford a colorless liquid (15 g, 47.2% yield). 1H NMR (250 MHZ, CDCI3) 1.21 (d, I=6.9 Hz, 3H, CHCH3), 2.34 (s, 3H, ArCH3), 2.74 (A), 3.14 (B), 3.78 (X) (ABX, JAB=14.9 Hz, IBX=7.7 Hz, 3H, ArC_l_12Cii_CH3), 7.06-7.92 (m, 9H, ArH) 13C NMR (250 MHz, CDCl3) 17.42, 19.42, 36.17, 41.03, 125.67, 126.10, 127.99, 128.38, 129.50, 130.11, 132.66, 135.89, 136.33, 137.86, 203.65 Ms 238 (M+), 220, 133, 117, 105 (base), 91,77 IR 3060-2875, 1695 (C=O), 1600, 1492, 1450, 1230 p-Mesitylpropiophenone - p-Mesitylpropiophenone was synthesized by alkylation and acylation of t-butyl malonate with 2,4,6-trimethylbenzyl chloride and benzoyl Chloride, using the procedure described for p-(o-tolyl)propiophenone. mp. 81 .0-82.0°c. 1H NMR (250 MHz, CDC13) 2.27 (s, 3H, p-Mes-CH3), 2.32 (s, 6H, o-Mes-CH3) 3.08, 3.24 (m, 4H, Ar(CH2)2), 6.78-7.79 (m, 7H, ArH) 13C NMR (250 MHz, CDC13) 19.66, 20.72, 23.63, 37.82, 127.93, 128.55, 128.99, 132.99, 134.72, 135.37, 135.96, 136.72, 199.45 MS 252 (Mt), 234,219, 147, 132, 117, 105, 91, 77 (base) IR 3090-2860, 1695 (C=O), 1602, 1490, 1452, 1290, 1208 p-Mesitylisobutyrophenone 207 p-Mesitylisobutyrophenone was prepared by the reaction of a-chloroisobutyrophenone with mesitylene following the route given below. g-Chloroisobutyrophenon - Sulfuryl chloride (MC/ B, 27.6 g, 0.204 mole) was slowly added to isobutyrophenone (OR, 30.0 g, 0.203 mole) at r.t.. After the addition was complete, the mixture was stirred for 3 hr. Benzene (200 ml) was added. The organic phase was washed with distilled water, and dried over sodium sulfate. After evaporation of the solvent, the residue was distilled at reduced pressure to afford the product (25.0 g, 67.5% yield). 1H NMR (60 MHz, CDC13) 1.90 (s, 6H), 7.34-8.16 (m, 5H, ArH) °iork * 01k“ mesitylene I» A1C13 n-Mgsitylisobutyrophengne - d-Chloroisobutyrophenone (15.0 g, 0.082 mole) in mesitylene (Aldrich, 45 ml) was added to anhydrous aluminum Chloride (MCB, 13.5 g, 0.101 mole) in mesitylene (15 ml). The mixture was heated at 50-60°c overnight, and then poured into iced aqueous hydrochloric acid (38%) after being cooled. The aqueous phase was extracted with ether (3x150 ml). The extracts were washed with saturated sodium bicarbonate solution and dried over sodium sulfate. After evaporation of the solvent, the 208 crude product was purified by column chromatography with 30% benzene in hexane and recrystallization from ethanol to give pure colorless crystal (10.6 g, 48.6% yield). m.p. 53.0-54.0°C. 1H NMR (250 MHz, CDC13) 1.19 (d, 1=7.3 Hz, 3H CHLML 2.22 (s, 3H, p—Mes-CH3), 2.32 (s, 6H, o-Mes—CH3), 2.96 (m, 2H, ArCI-Iz), 3.76 (m, 1H, CHZCHCH3), 6.82-7.86 (m, 7H, ArH) 13C NMR (250 MHz, CDC13) 17.27, 20.29, 20.62, 32.33, 40.67, 128.02, 128.39, 129.01, 132.69, 133.56, 135.22, 136.42, 136.59, 204.62 MS 266 (Mt), 248, 233, 161, 145, 133 (base), 105,91, 77 IR 3090-2870, 1693 (C=O), 1600,1482, 1450, 1225 Preparation of d-Deuteriated Ketones The percentage of deuteriation was Checked with MS. The M+-1 or M+-2 (for di-deuteriated ketones only) peak of deuteriated ketones can be from two sources, the undeuteriated impurity or the loss of one or two protons from the molecular ions of the ketones. The corrections for the loss of protons were made by comparing with the mass spectra of the undeuteriated ketones taken under the same condition. The values obtained from multiplying the intensities of the M+ -1 or M“'-2 peaks of the deuteriated ketones by the ratios of the same peaks to the M1“ peak for the undeuteriated ketones were substracted from the intensities of these peaks of the deuteriated ketones. The remained intensities were considered to be from the undeuteriated ketones. The percentages of deuteriation were given with each ketones. For a better evaluation, the much stronger M13105 (benzoyl group) peak was used in the case of d-mesitylacetophenone d-(o-tolyl)propiophenone, or-(2,4,6-triisopropylphenyl)acetophenone, and 209 d-mesityl-o:-phenylacetophenone. d-Mesitylacetophenone was a -deuteriated by the following procedure.117 The ketone (0.020mole) in dioxane (Mallinckrodt, 200 ml) was added to sodium carbonate (Mallinckrodt, 40 g, 0.378 mole) in D20 (Baker, 170 ml). The solution was refluxed overnight. The organic phase was separated. The aqueous phase was extracted with ether (2x250 ml). The extracts were combined, and dried over sodium sulfate. After evaporation of solvent, the crude product was recrystillized from hexane or ethanol-d1. a-(o-Tolyl)propiophenone, a-(2,4,6-triisopropylphenyl)acetophenone, d-mesityl-o:-phenylacetophenone were ox-deuteriated by the same precedure, but the reaction scale was reduced 50%. at-(o-Tolyl)propiophenone-dl 1H NMR (250 MHz, CDCl3) 1.48 (s, 3H, ArCHCH3), 2.50 (s, 3H, ArCH3), 7.05-7.85 (m, 9H, ArH) Ms 225 (MT), 120, 105 (base), 91, 77 Relative intensity of the relevant peaks: ketone 2 224 (2.71), 223 (0.0), 119 (19.00), 118 (1.52) ketone 2-d 225 (4.41), 224 (0.0), 120 (16.58), 119(2.46) Percentage of undeuteriated ketone 6.0% c-Mesitylacetophenone-dz 1H NMR (250 MHz, CDC13) 2.21 (s, 6H, o-Mes-CH3), 2.32 (s, 3H, p-Mes-CH3), 6.92-8.12 (s, 7H, ArH) Ms 240 (M+), 135, 119, 105, 91,77 Relative intensity of the relevant peaks: 210 ketone 16 238 (6.07), 237 (0.0), 236 (0.0), 133 (39.23), 132 (1.18), 131 (0.87) ketone 16-d2 240 (6.56), 239 (0.0), 238 (0.0), 135 (41.86), 134 (2.27), 133 (0.92) Percentage of undeuteriated ketone 0.0%, percentage of mono-deuteriated ketone 2.4% d-(2,4,6-Triisopropylphenyl)acetophenone-d2 1H NMR (250 MHz, CD03) 1.23 (overlapping d's, 18H, CH(CB_3)2), 2.86 (m, 3H, Cfl(CH3)2), 7.05-8.10 (m, 7H, ArH) Ms 324 (M+), 219, 203, 105, 95, 91, 77 Relative intensity of the relevant peaks: ketone 17 322 (2.51), 321 (0.0), 320 (0.0), 217 (42.18), 216 (0.0), 215 (0.97) ketone 17-dz 324 (2.53), 323 (0.0), 322 (0.0), 219 (42.22), 218 (1.62), 217 (0.67) Percentage of undeuteriated ketone 0.0%, percentage of mono-deuteriated ketone 3.7% d-Mesityl-a-phenylacetophenone-d 1H NMR (250 MHz, CD03) 2.19 (s, 6H, o-Mes-CH3), 2.28 (s, 3H, p—Mes-CH3), 6.89-7.93 (m, 12H, ArH) Ms 315 (MT), 210 (base), 193, 179, 105, 91,77 Relative intensity of the relevant peaks: ketone 8 314 (5.61), 313 (0.0), 209 (82.14), 208 (0.0) ketone 8-d 315 (4.89), 314 (0.50), 210 (80.79), 209(3.62) Percentage of undeuteriated ketone 4.3% p-Mesitylpropiophenone, p-mesitylisobutyrophenone were undeuteriated by the following procedure.117 The ketone (0.010 mole) in dioxane (Mallinckrodt, 100 ml) was added to 211 sodium hydroxide (Mallinckrodt, 6.0 g, 0.150 mole) in D20 (Baker, 100 ml). The solution was refluxed overnight. The organic phase was separated. The aqueous phase was extracted with ether (2x250 ml). The extracts were combined, and dried over sodium sulfate. After evaporation of solvent, the crude product was recrystillized from hexane. p-Mesitylpropiophenone-dz 1H NMR (250 MHz, CD03) 2.27 (s, 3H, p-Mes-CH3), 2.32 (s, 6H, o-Mes-CH3) 3.08 (s, 2H, ArCHzCDz), 6.78-7.79 (m, 7H, ArH) Ms 254 (M+), 236, 149, 132, 117, 105, 91, 77 (base) Relative intensity of the relevant peaks: ketone 20 252 (2.11), 251 (0.0), 250 (0.0) ketone 20-d2 254 (4.08), 253 (0.28), 252 (0.0) . Percentage of mono-deuteriated ketone 6.4%, percentage of undeuteriated ketone 0.0% p-Mesitylisobutyrophenone-d 1H NMR (250 MHz, CD03) 1.19 (s, 3H, CDC_H3), 2.22 (s, 3H, p-Mes-CH3), 2.32 (s, 6H, o-Mes-CH3), 2.86, 3.03 (AB quartet, I=14.9 Hz, 2H, ArCHz), 6.82-7.86 (m, 7H, ArH) MS 267 (M+), 249, 162, 145, 133 (base), 117, 105, 91, 77 Relative intensity of the relevant peaks: ketone 21 266 (2.63), 265 (0.08) ketone 21-d 267 (1.64), 266 (0.0) Percentage of undeuteriated ketone 0.0% 212 IV. Isolation and Identification of Photoproducts All the 6C separations were performed on a VA 900 Gas Chromatogram with a SE-30 column. The carrier gas flow was adjusted at 55 ml/ min. The injector and detector temperatures were maintained at 250°C and 270°C respectively. The separated components were collected with a s-shaped glass tube at the outlet of the GC. A dry-ice/ acetone bath was used for cooling when low-boiling components were being collected. The sample was collected starting from the peak height which equals 20-30% of the overall peak height to avoid overlapping contaminations. The tlc separations were done with a mixture of hexane and ethyl acetate as eluent. The separated components were collected along with silica gel, and then extracted with chloroform, and filtered. The solvent was removed. Products from or-(o-Tolyl)-p-Methoxyacetophenone ct-(o-tolyl)-p-methoxyacetophenone (0.30 g) in cyclohexane (500 ml) was irradiated until 100% ketone conversion by HPLC. The solvent was removed, and the crude product was analysized by HPLC to contain one major component (>98%). The product was rescrystallized and identified by its spectroscopic data as 2-(p-methoxyphenyl)-2-indanol. 2-(2;Methoxyphenyl)-2-Indanol mp. 206-208°C 1H NMR (250 MHz, CD03) 1.96 (s, 1H, OH), 3.29, 3.51 (AB quartet, I=16.6 Hz, 4H, ArCHz), 3.82 (s, 3H, OCH3), 6.83-7.56 (m, 4H, ArH) 13C NMR (250 MHz, c003) MS 240 (M+), 222 (M+-18), 207, 135 (base), 105, 91, 77 Jul 213 IR (C04) 3600, 3080-2840, 1612, 1515, 1250, 1180, 1042 Products from at-(o-Tolyl)propiophenone a-(o-Tolyl)propiophenone (0.30 g) in cyclohexane (500 ml) was irradiated until 100% ketone conversion by GC. Three major components were isolated by GC at 240°C and identified by their spectroscopic data. The isomeric 2,3-di(o-tolyl)butanes were partially separated by the GC. Collections starting from half height of the peaks were able to isolate the two isomers with ca. 85-90% purity. The formation of benzaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and GC. g-l-MethLl-;-Phergl-g-Indanol 1H NMR (250 MHz, CD03) 1.25 (d, 1=7.3 Hz, 3H, CHCH3), 1.94 (s, 1H, 0H), 3.17, 3.52 (AB quartet, I=16.6 Hz, 2H, ArCHz), 3.58 (q, I=7.3 Hz, 1H, CHCH3), 7.25-7.65 (m, 9H, ArH) 13C NMR (250 MHz, CD03) 10.9, 49.27, 50.38, 85.39, 123.66, 124.84, 125.35, 126.91, 127.01, 128.13, 128.60, 140.09, 144.17, 145.11 Ms 224 (M+), 206 (M+-18), 191, 165, 119,105 (base), 91, 77 IR (CD03) 3500, 3095-2860, 1608, 1480, 1455, 1183, 1080, 1020 2,3-Di(o—tolyl)butane (Two Diastereomers) Diastereomer (1) 1H NMR (250 MHz, CD03) 0.98 (d, 1-=7.7 Hz, 6H, CHCI_13), 2.38 (s, 6H, ArCH3), 3.25 (m, 2H, C_I-_1CH3), 6.93-7.32 (m, 8H, ArH) Ms 238 (M+), 202, 119 (Base), 105, 91,77 Diasteromer (2) 1H NMR (250 MHz, CD03) 1.32 (d, 1-=7.7 Hz, 6H, CHCHa), 2.15 (s, 6H, 214 ArCH3), 3.28 (m, 2H, CHCH3), 6.92-7.30 (m, 8H, ArH) Ms 238 (M+), 202, 119 (Base), 105, 91, 77 Products from ot-(o-Tolyl)valerophenone a-(o-Tolyl)valerophenone (0.30 g) in cyclohexane (500 ml) was irradiated until 100% ketone conversion by GC. The products were isolated by GC at 250°C. The major product was 2-phenyl-2-indanol. A very minor product was identified as 2-phenyl-3-propyl-2-indanol by 1H NMR. Isolation of photoproducts at approximately 40% ketone conversion gave ot-(o-tolyl)acetophenone as well as the above products. ct-(o-Tolyl)- acetophenone was characterized by its identical spectra with the ones of authentic sample. The formation of small amount of benzaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and GC. 2-Phenyl-2-Indanol 2-Phenyl-2-indanol was verified by its identical spectra with the ones of authentic sample. Z-2-Phenyl-3-Propyl-2—Indanol 1H NMR (250 MHz, CD03) 0.84 (d, 1:7.3 Hz, 3H, (CH2)2CH3), 1.25-1.82 (m, 4H, (CHZ)ZCH3), 2.01 (s, 1H, OH), 3.17, 3.44 (AB quartet, I=16.6 Hz, 2H, ArCHz), 3.58 (t, 1:55 Hz, 1H, CHPr), 7.24-7.63 (m, 9H, ArH) Products from a-(o-Tolyl)isobutyrophenone The ketone (0.30 g) in benzene (500 ml) with 0.007 M dodecanthiol was irradiated to 100% ketone conversion by GC. Two major products were 215 isolated by GC at 180°C and identified as benzaldehyde and o-cymene. The formation of benzaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and GC. Benzaldehyde 1H NMR (250 MHz, c003) 7.52-7.93 (m, 5H, ArH), 10.11 (s, 1H, CH0) W 1H NMR (250 MHz, CD03) 1.23 (d, 1:7.3 Hz, 6H, CH(CH3)2), 234 (s, 3H, ArCH3), 3.14 (sep, 1:7.3 Hz, 1H, CH(CH3)2), 7.12-7.18 (m, 4H, ArH) Products from d-Mesitylpropiophenone The ketone (0.30 g) in cyclohexane (500 ml) was irradiated to 100% ketone conversion by GC. The products were isolated by GC at 260°C and identified by their spectroscopic data. The formation of small amount of benzaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and GC. Z-l ,5,7-Trimethyl-2-Phenyl-2-Indanol 1H NMR (250 MHz, CD03) 1.25 (d, 1:8.5 Hz, 3H, CHCHa), 2.02 (s, 1H, OH), 2.30 (s, 3H, ArCH3), 2.32 (s, 3H, ArH3), 3.28, 3.36 (AB quartet, I=18.6 Hz, 2H, Ara-12), 3.51 (q, 1:8.5 Hz, 1H, CH_CH3), 6.87-7.51 (m, 7H, ArH) 13c NMR (250 MHz, CD03) 13.51, 19.08, 21.12, 47.80, 49.85, 83.90, 122.82, 125.80, 126.81, 128.10, 129.73, 133.87, 136.62, 140.08, 141.02, 146.91 Ms 252(Mt), 234 (Mt-18), 219, 147, 105 (base), 91 77 IR (C04) 3600, 3095-2878, 1610, 1480, 1450, 1176, 1072 E-l 5,7-Trimethyl-2-Phen yl-Z-lndanol 216 The sample of E-1,5,7-trimethyl-Z-phenyl-Z—indanol can not be freed of the Z isomer. Its 1H NMR is derived from the spectrum of the mixture. 1H NMR (250 MHz, CD03) 0.74 (d,1:8.1 Hz, 3H,CHC1_-13), 2.21 (s, 1H, 0H), 2.32 (s, 3H, ArCH3), 2.37 (s, 3H, ArH3), 3.03, 3.88 (AB quartet, I=18.6 Hz, 2H, ArCHz), 3.95 (q, I=8.1 Hz, 1H, CHCH3), 7.03-7.43 (m, 7H, ArH) GC—MS 252 (M+), 234 (M+-18), 219, 203, 149, 105 (base), 91, 77 Z E-l-Mesitox -1-Phen 1 r0 ene The Z/E forms can not be separated. The sample collected from CC contained the Z/ E isomers in a ratio of 1:4. The following spectroscopic data are derived from the spectra of the mixture. 1H NMR (250 MHz, CD03) Z-Isomer: 1.52 (d, J=8.1 Hz, 3H, CHCH3), 2.18 (s, 3H, p-Mes-CH3), 2.24 (s, 6H, o-Mes-CH3), 5.19 (q, 1:8.1 Hz, 1H, CHCH3), 6.74-7.42 (m, 7H, ArH) E—Isomer: 1.64 (d, 1:8.1 Hz, 3H, CHCfiq), 2.22 (s, 6H, o-Mes-CH3), 2.31 (s, 3H, p-Mes-CH3), 4.38 (q, I=8.1 Hz, 1H, CHCH3), 6.91-7.66 (m, 7H, ArH) MS (Mixture) 252 (W), 223, 147, 136 (base), 115, 105, 91, 77 Products from cr-Mesitylvalerophenone The ketone (0.30 g) in cyclohexane (500 ml) was irradiated to 100% ketone conversiOn by GC. The major product was isolated by GC at 260°C and Characterized as Z-5,7-dimethyl-2-phenyl-l-propyl-Z-indanol. A minor product was identified by GC—MS as 1-mesitoxy-1-phenylpentene. The formation of‘ small amount of benzaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and GC. When irradiated in benzene and benzene with 1 M dioxane to 100% ketone conversion, a small peak on GC 217 (column #1, 165°C) was identified as 4,6-dimethyl-Z-phenyl-Z-indanol (the type II product) by coinjection with authentic sample on GC. The area ratio of this peak to Z-5,7-dimethyl-2-phenyl-1-propyl-2-indanol was 0.046 and 0.065 in benzene and benzene with 1 M dioxane respectively. However, in a quantum yield measurement in benzene with 1 M dioxane where irradiation was controlled at low ketone conversion, the relative amount of this peakto the indanol seemed much smaller than the above value, and was too small to be measured. Z-5,7-Dimethyl-2-Phenyl—1-Propyl-2-Indanol 1H NMR (250 MHz, CD03) 0.93 (t, 1:8.1 Hz, 3H, (CH2)2CH3), 1.10-2.01 (m, 4H, (CH2)2CH3), 2.07 (s, 1H, OH), 2.22 (s, 3H, ArCH3), 2.29 (s, 3H, ArH3), 3.25, 3.40 (AB quartet, I=16.6 Hz, 2H, ArCHz), 3.51 (dd, 11:4.7 Hz, Iz=3.4 Hz, 1H, CLIPr), 6.81-7.38 (m, 7H, ArH) 13C NMR (250 MHz, CD03) 14.54, 18.92, 21.01, 21.41, 32.52, 47.51, 54.00, 83.38, 122.21, 124.70, 126.47, 127.87, 129.20, 133.28, 136.13, 139.97, 141.37, 149.11 MS 280(M”), 262 (Mt-18), 233, 218, 175, 146, 133, 105 (Bsae), 91, 77 IR (C04) 3610, 3090-2875, 1600, 1455, 1065, 1040 1-Mesitoxy-1-Phenylgntene The identification was based on the Characteristic flagrnentation of the enol ethers giving an ion peak at 136 in MS. GC-MS 280 (M+), 223, 145, 136 (base), 115, 105, 91, 77 Products from d-Mesitylisobutyrophenone The ketone (0.30 g) in cyclohexane (500 ml) was irradiated to 100% ketone conversion by HPLC. Two major products were isolated by GC at 180°C and identified as benzaldehyde and 2-mesitylpropene. The formation of 218 benzaldehyde was verified by irradiation of the ketone in the presence of 0.005 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and 6C. Benzaldeh de 1H NMR (250 MHz, CD03) 752-793 (m, 5H, ArH), 10.11 (s, 1H, CHO) 2-Mesiglpromne 1H NMR (250 MHz, c003) 1.97 (s, 3H, =CCH3), 2.27 (s, 6H, o-Mes-CH3), 2.33 (s, 3H, p-Mes-CH3), 4.78 (d, 1:2.1 Hz, 1H, vinyl H), 5.29 (d, 1:21 Hz, 1H, vinyl H), 6.90 (s, 2H, ArH) Products from a-Mesityl-d-Phenylacetophenone The ketone (0.30 g) in cyclohexane (500 ml) was irradiated to 100% ketone conversion by HPLC. Three major products were separated by GC at 270°C and identified by their spectroscopic data. The formation of small amount of benzaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and 6C. 1 2-5 ,7-Dimethyl-1 ,2-Diphenyl-2-Indanol 1H NMR (250 MHz, CD03) 1.57 (s, 1H, CH), 1.83 (s, 3H, ArCH3), 2.37 (s, 3H, ArH3), 3.37, 3.50 (AB quartet, I=16.8 Hz, 2H, ArCHz), 4.66 (s, 1H, ArCflPh), 6.68-7.43 (m, 11H, ArH) 13C NMR (250 MHz, CD03) 19.27, 21.28, 48.70, 63.25, 83.09, 12252, 124.88, 126.77, 127.44, 128.11, 128.68, 129.49, 129.70, 134.78, 137.46, 137.54, 138.59, 141.90, 147.81 Ms 314 (M+), 296 (M+-18), 209, 105 (base), 91, 77 IR (CD03) 3560, 3090-2860, 1608, 1500,1455, 1180, 1060 219 E-1-Mesitoxy-1,2-Diphenylethylene 1H NMR (250 MHz, c003) 2.29 (s, 6H, o-Mes-CH3), 2.32 (s, 3H, p-Mes-H3), 5.43 (s, 1H, vinyl H), 7.00-7.60 (m, 12H, ArH) 13C NMR (250 MHz, CD03) 16.25, 20.76, 103.03, 117.79, 125.42, 126.41, 127.11, 127.91, 128.32, 128.62, 128.81, 129.23, 1295312970, 131.12 Ms 314 (M+), 223, 209, 179, 178 (base), 136, 105,91, 77 IR (CD03) 3560, 3070-2860, 1608, 1500,1455, 1180, 1060 Z-l-Mesitoxy-l ,2-Diphenylethylene m.p. 97.5-100°c (recrystallized from hexane) 1H NMR (250 MHz, coc13) 2.28 (s, 3H, p-Mes-H3), 2.56 (s, 6H, o-Mes-CH3), 5.97 (s, 1H, vinyl H), 6.68-7.82 (m, 12H, ArH) O 13c NMR (250 MHz, CD03) 17.10, 20.46, 111.30, 126.34, 127.11, 127.92, 128.23, 128.34, 128.81, 129.72, 132.75, 136.25, 136.59, 150.28, 153.63 Ms 314 (M+), 223, 209, 179, 178, 136 (base), 105, 91, 77 IR 3080-2860, 1640, 1605, 1480, 1290, 1210, 1148, 1060 d-Mesityl-ct-Phenyl-p-Methoxyacetophenone The ketone (0.30 g) in benzene (500 ml) was irradiated to 100% ketOne conversion by HPLC. Three major products were separated by preparative tlc with 5% ethyl acetate in hexane as eluent and identified by their spectroscopic data. The order of elution follows the E-enol ether, Z-enol ether closely behind, and indanol. The formation of small amount of p-methoxybenzaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and GC. Z-5 7-Dimeth 1-2- -Methox hen l-l-Phen l-2—Indanol 220 1H NMR (250 MHz, CD03) 1.73 (s, 1H, 0H), 1.85 (s, 3H, ArCH3), 2.38 (s, 3H, ArH3), 3.36, 3.48 (AB quartet, 1:168 Hz, 2H, ArCHz), 3.82 (s, 3H, OCT-I3), 4.63 (s, 1H, ArcHPh), 6.65-7.42 (m, 11H, ArH) 13C NMR (250 MHz, CD03) 19.20, 21.25, 48.57, 55.20, 63.11, 82.92, 113.42, 12249, 126.10, 127.34, 128.61, 129.50, 129.63, 134.73, 137.37, 137.70, 138.72, 139.99, 141.90 Ms 344 (M+), 253,209, 105,91, 77, 43 (base) IR (c003) 3530, 3070-2845,1610,1500, 1250, 1180, 1035 E—1-Mesito -1- -Methox hen l 2-Phen leth lene 1H NMR (250 MHz, CD03) 2.28 (s, 6H, o-Mes-CH3), 2.34 (s, 3H, p-Mes-H3), 3.86 (s, 3H, OCH3), 5.47 (s, 1H, vinyl H), 6.87-7.56 (m, 11H, ArH) 13c NMR (250 MHz, c003) 17.10, 20.80, 55.24, 110.09, 113.34, 113.70, 124.29, 125.25, 126.04, 127.93, 128.31, 128.49, 128.64, 128.72, 129.49, 129.69, 130.55 Ms 344 (M+), 135 (base), 105, 91, 77 IR (CD03) 3050-2870, 1640, 1610, 1515, 1480, 1250, 1210, 1175 Z-l-Mesitoxy-l-(p-Methoxyphenyl)-2-Phenylethylene m.p. 95.5-97.5°c (recrystallized from methanol) 1H NMR (250 MHz, CD03) 219 (s, 3H, p-Mes-H3), 2.28 (s, 6H, o-Mes-CH3), 3.78 (s, 3H, OCT-I3), 5.91 (s, 1H, vinyl H), 6.71-7.81 (m, 11H, ArH) 13c NMR (250 MHz, c003) 17.10, 22.67, 55.14, 110.09, 113.35, 124.37, 126.05, 127.93, 128.31, 128.49,128.64, 128.88, 129.49, 129.69, 130.55, 132.67, 136.47 Ms 344 (M+), 135 (base), 105, 91, 77 IR (CD03) 3040-2850, 1640, 1610, 1510, 1480, 1255, 1215, 1180 Products from d-Mesityl-o:-Phenyl-p-Cyanoacetophenone The ketone (0.30 g) in benzene (500 ml) was irradiated to 100% ketone 21 conversion by HPLC. Three major products were separated by preparative tlc with 7% ethyl acetate in hexane as eluent and identified by their spectroscopic data. The order of elution follows the E-enol ether, Z-enol ether closely behind, and indanol. The formation of small amount of p-cyanobenzaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and GC. Z—5,7-Dimethyl-2-(p-Cyanophenyl)-1-Phenyl-2-Indanol m.p. 168.7-170°c (recrystallized from methanol) 1H NMR (250 MHz, c003) 1.72 (s, 1H, OH), 1.85 (s, 3H, AICH3), 237 (s, 3H, Ari-I3), 3.38, 3.44 (AB quartet, I=16.8 Hz, 2H, ArCHz), 4.53 (s, 1H, ArC_1-_I_Ph), 6.88-7.61 (m, 11H, ArH) 13c NMR (250 MHz, CD03) 19.05, 21.24, 48.47, 63.02, 826611058, 118.87, 122.45, 125.57, 127.79, 128.90, 129.29, 129.96, 131.96, 134.83, 136.83, 137.85, 138.07, 141.11,153.49 ‘ MS 339 (MT), 209, 197, 130, 105, 91, 77, 43 (base) IR (CD03) 3525, 3090-2860, 2225, 1610, 1495, 1456, 1250, 1090-1010 E-1-Me itox -1- -C ano hen l 2-Phen leth lene 1H NMR (250 MHz, CD03) 2.19 (s, 6H, o-Mes-CH3), 225 (s, 3H, p-Mes-H3), 551 (s, 1H, vinyl H), 6.83-7.62 (m, 11H, ArH) 13c NMR (250 MHz, CD03) 16.16, 20.76, 104.55, 126.28, 128.28, 128.95, 129.30, 129.71, 129.89, 130.53, 132.00, 134.76, 135.61, 140.00, 148.06, 152.02 Ms 339 (M+), 248,209, 204, 203, 136 (base), 105, 91, 77 IR (CD03) 3090-2860, 2225, 1635, 1475, 1200, 1137 Z-1-Mesitoxy-1-(gCyanophenyltZ-Phenylethylene m.p. 173-174.7°c (recrystallized from methanol) 1H NMR (250 MHz, CD03) 2.16 (s, 3H, p-Mes-H3), 2.23 (s, 6H, o-Mes-CH3), 222 6.04 (s, 1H, vinyl H), 6.69-7.79 (m, 11H, ArH) 13c NMR (250 MHz, CD03) 17.02, 20.45, 111.55, 113.70, 118.53, 127.21, 127.44, 127.64, 128.47, 129.13, 130.01, 131.82, 133.36, 135.35, 142.10, 149.82, 15282 Ms 339 (Wt), 248, 209, 204, 203, 136 (base), 135, 105, 91, 77 IR (CDQ3) 3060-2840, 2220, 1630, 1475, 1205, 1138 Products from o-Mesityl-a-Phenyl-2,4,6-Trimethylacetophenone The ketone (0.30 g) in cyclohexane was irradiated to 100% ketone conversion by HPLC. The major product was isolated by tlc with 2% ethyl acetate in hexane and identified as 1,2-dimesityl-1,2-di-phenylethane. The formation of mesitaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjection with authentic sample on HPLC and GC. 1,2-Dimesigl-1,2-Diphenylethane (Two Diastereomers) The two diastereomers can not be separated and the following spectra are from the ones of the mixtures. The identification was based on the comparison with literature data.118 Diastereomer (1) 1H NMR (250 MHz, c003) 2.07 (s, 6H, AICH3), 212 (s, 6H, ArCH3), 2.22 (s, 6H, ArCH3), 5.46 (s, 2H, ArCI-IPh), 6.55-7.09 (m, 14H, ArH) Diastereomer (2) 1H NMR (250 MHz, CD03) 2.10 (s, 6H, ArCH3), 221 (s, 6H, ArCH3), 231 (s, 6H, ArCH3), 5.48 (s, 2H, ArCI-IPh), 6.72-7.24 (m, 14H, ArH) MS 318 (M+), 209 (M+/2) Products from a-Mesityl-2,4,6-Trimethylacetophenone 223 The ketone (0.30 g) in cyclohexane was irradiated to 100% ketone conversion by HPLC. The major product was isolated by GC at 250°C and identified as 1,2-dimesitylethane. The formation of mesitaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjection with authentic sample on HPLC and GC. 1,2-Dimesitylethane 1H NMR (250 MHz, CD03) 2.27 (s, 3H, p-Mes-H3), 2.37 (s, 6H, o-Mes-CH3), 279 (s, 4H, ArCHZ), 6.85 (s, 4H, ArH) Ms 266 (Mt), 221, 204, 189, 161, 139, 133 (base), 117, 105, 91, 77 Products from a-Mesityl-o-Methylacetophenone The ketone (0.30 g) in cyclohexane was irradiated to 100% ketone conversion by GC. The NMR of the crude product showed the major products were 3,5-dimethyl-2-(o-tolyl)-2-indanol and 1,2-dimesityl-ethane The products were isolated by GC at 260°C. 3,5-Dimethyl-2-(o-tolyl)2-indanol partially dehydrates on the preparative GC and quantitatively dehydrates on the analytical GC. The formation of tolaldehyde was verified by irradiation of the ketone in the presence of 0.007 M dodecanthiol in benzene and coinjections with authentic sample on HPLC and 6C. 3,5;Dimethyl-2-(o-tolyl)—2-Indanol 1H NMR (250 MHz, c1903) 2.26 (s, 3H, AICH3), 232 (s, 3H, ArH3), 252 (s, 3H, o-CH3), 2.26, 3.62 (2 AB quartets, I=16.6 Hz, 4H, ArCHz), 6.87-7.62 (m, 6H, ArH) 13c NMR (250 MHz, CD03) 18.98, 21.18, 21.72, 46.49, 48.22, 83.60, 12287, 12556, 125.79, 127.33, 128.54, 129.06, 132.29, 133.88, 136.28, 136.58, 140.64, 143.08 Ms 252 (M+), 234 (base, M+-18), 219, 204, 133, 119,91, 77 IR (C04) 3600, 3060-2860, 1615,1482, 1452, 1220,1048 224 Products from B-(o-Tolyl)propiophenone The ketone (0.30 g) in cyclohexane (500 ml) was irradiated for 14 days. The conversion was too low for any products to be isolated and identified, although there were peaks of products on GC. Products from fi-(o-Tolylfisobutyrophenone The ketone (0.30 g) in cyclohexane (500 ml) was irradited for 14 days to approximately 25% ketone conversion by GC. The major product was isolated by GC at 260°C and identified as 3-methyl-1,2,3,4-tetrahydro—2-naphthol. 3-Methyl-1 ,2,3,4-Tetrahydro-2-Naphthol _ 1H NMR (250 MHz, CD03) 0.77 (d,1:6.7 Hz, 3H, CHcHg), 2.35 (s, 1H, OH), 2.37-2.81 (m, 3H, ArCI_i_2C_1-1CH3), 2.95, 3.37 (AB quartet, I=17.3 Hz, 2H, AlCHz), 3.58 (q, I=7.3 Hz, 1H, CHCH3), 7.06-7.53 (m, 9H, ArH) 13C NMR (250 MHz, CD03) 15.87, 34.67, 36.83, 45.60, 74.81, 124.94, 124.95, 126.01, 126.14, 126.61, 128.28, 128.67, 129.34, 134.29, 136.20, 146.81 Ms 238 (W), 220 (Mt-18), 205, 133, 105 (base), 91, 77 IR (CD03) 3510, 3060-2855, 1450, 1180, 1130 Products from p—Mesitylpropiophenone The ketone (0.30 g) in methanol (500 ml) was irradited for 18 days to 100% ketone conversion by GC. The major product was isolated by GC at 260°C and identified as 5,7-dimethyl-1,2,3,4-tetrahydro-2-naphthol. 5,7-Dimethyl-1 l2,3,4r-Tetrahydro-2-Naphthol 1H NMR (250 MHz, CD03) 2.18 (s, 3H, ArCH3), 2.12 (s, 1H, OH), 226 (s, 3H, 225 ArCH3), 2.35-2.82 (m, 4H, ArCflzCflz), 294, 3.28 (AB quartet, 1:175 Hz, 2H, ArCHz), 6.75-7.50 (m, 7H, ArH) 13c NMR (250 MHz, CD03) 19.35, 20.77, 23.72, 35.34, 43.85, 72.14, 124.84, 126.93, 127.63, 128.23, 128.56,130.64, 133.32, 134.10, 135.13, 147.55 Ms 252 (M+), 234 (M+-18), 219,202,143, 132, 115, 105 (base), 91, 77 IR (c003) 3580, 30802860, 1445, 1225,1175, 1100 Products from p-Mesitylisobutyrophenone The ketone (0.30 g) in cyclohexane (500 ml) was irradited for 14 days to 100% ketone conversion by GC. The product was isolated by GC at 260°C and identified as 3,5,7-trimethyl-1,2,3,4-tetrahydro-2-naphthol. 3 ,5,7-Trimethyl-1 ,2,3 ,4-Tetrahydro-2-Naphthol 1H NMR (250 MHz, CD03) 0.83 (d, 1:7.1 Hz, 3H, CHCH3), 1.78 (s, 1H, OH), 2.27 (s, 3H, AI'CH3), 2.30 (s, 3H, ArCH3), 2.38-2.82 (m, 3H, AI'C1_'12CI'I_CI'I3), 2.92, 3.48 (AB quartet, 1:171 Hz, 2H, ArCHz), 677-755 (m, 7H, ArH) 13c NMR (250 MHz, c1903) 1563,1936, 20.77, 3222, 36.85, 45.87, 7454, 124.90, 126.38, 127.56, 128.12, 128.58, 131.05, 133.73, 135.10, 136.00, 146.68 Ms 266 (Mt), 248 (M+-18), 233, 132, 117, 105 (base), 91, 77 IR (CD03) 3610, 3100-2840, 1605, 1490, 1450, 1180, 1075 NMR Studies of Photoproducts from c:-(2,4,6-Triisopropylphenyl)- acetophenone and or-(2,4,6-Triisopropylphenyl)acetophenone-dz or-(2,4,6-Triisopropylphenyl)acetophenone 17 in benzene-d6 in a Pyrex NMR tube was irradiated at 365 nm for 8 hr (sample #1), and 22 hr (sample #2). NMR showed that the area ratio of one of the methyl signals at C1 of the 226 indanol (0.78 ppm) to the cat-methylene signal of the remained ketone (4.32 ppm) was 1.08 (sample #1) and 1.35 (sample #2). The relative amount of the indanol to the ketone was then 0.72 (sample #1) and 0.90 (sample #2). The area ratio of the vinyl proton signal of the enol (6.13 ppm) to the same methyl signal of the indanol was 1/ 2.3 (sample #1) and 1/ 3.5 (sample #2), averaging 1/ 2.9. o:-(2,4,6-Triisopropylphenyl)acetophenone-d2 17-d2 in C04 in a Pyrex NMR tube was irradiated at 465 run until the area ratio of the methyl signal (0.78 ppm) at C1 of the indanol to the ortho proton signal of the benzoyl group (8.10 ppm) in the remained ketone reached ca. 0.5 by 60 MHz NMR. The solvent was evaporated and CD03 was added. A 250 MHz NMR was then taken. The area ratio of the same signals was 0.527, indicating a ratio of 0.35 for the indanol and the remained ketone. The area ratio of the d-methylene signal appearing at 4.45 ppm to the ortho proton signal of the benzoyl group in the ketone was 0.11. The deuterium NMR of the irradiated sample was taken in CH03 on a Bruker WH-180 spectrometer with a 10 mm broadband probe. V. Irradiation in Solid State Irradiation in solid state has been conducted in powder form or crystal. The ketones to be irradiated were first dissolved in spectral grade methylene chloride, and the resulting solutions were transfered onto small glass plates (2.5x1 cm) to form a liquid layer. The samples were air-dried, and then dried under vacuum. The glass plates were placed in pyrex tubes (100x13 mm) sealed with rubber septa. The samples were irradiated with a medium pressure merury lamp filtered through an uranium sleeve for ketone 17 and 227 a Pyrex tube for the others, degassed by means of needles through the septa with argon gas during the reaction. Alternatively, the ketones can be irradiated in crystaline form. A pyrex test tube (100x13 mm) was stretched and cut in the middle witha natural gas g: 15/ fl Crystal T _L [mmll] Figure 70 torch (Figure 70). Fine crystals of the ketones were placed in the sealed stretched end of the test tube, which was degassed and irradiated the same way as in the powder reactions with a Pyrex sleeve. The products were dissolved in benzene and identified by a combination of coinjection with authentic samples on 6C or HPLC and spectroscopic data. The product ratios were measured by 6C or HPLC. A. In Powder Form The following ketones have been irradiated in powder form with the general procedure described above. 228 ct-(o-Tolyl)acet0phenone The ketone was irradiated for 24 hr, and the product was identified as 2-phenyl-2-indanol by its identical 1H NMR spectrum with the authentic sample. The NMR was taken from the reaction mixture without separation. al-(o-Tolyl)prop iophenone The ketone was irradiated for 24 hr. Two of the products were identified by GC-MS and coinjection with authentic samples on GC as Z-1-methyl-2-phenyl-2-indanol and 2,3-di(o-tolyl)butane. The third product was isolated by GC at 240°C and Characterized as p-(o-tolyl)propi0phenone by its identical 1H NMR spectrum with the authentic sample. Benzaldehyde was identified by coinjection with the authentic sample. The product ratio was measured by GC. The irradiated sample (0.1 g) was dissolved in 2 ml benzene with 0.004 M heptadecane. Benzaldehyde was analysized on column #4 at 100°C. The other components were analysized on column #2 at 145°. The ralative area ratio of the components was as follows: indanol/18/(ArCHR)2/benzaldehyde = 5.07/1.00/ 1.77/ 1.20, which was then corrected by multiplying each numbers with the 6C response factors listed in appendix for the individual compounds. The response factor for (ArCHR)2 was estimated to be 0.944 by dividing its number of carbon atoms into 17 (the carbon number of heptadecane). The corrected realtive ratio was given as indanol/18/(ArCHR)2/benzaldehyde = 6.03/1.40/1.67/3.08. The sum of the four number was 12.18. The percentage of product distributation was obtained by dividing each of the four numbers by 12.18. 229 a-Mesitylacetophenone The ketone was irradiated for 24 hr. 4,6-Dimethyl-Z-phenyl-Z-indanol and 1,2-dimesitylethane were identified by GC-MS and coinjection with authentic samples on GC. Dibenzil was identified by coinjection with the authentic sample on GC. The product ratio was measured by GC with column # 4 ( 100°C for 5 min and then raising the temperature mannually ca. 10°c/ min to 165°C). The relative area ratio of the products was indanol/(ArCH2)2/dibenzil = 41.94/16.94/ 1.00. The following carbon atom numbers of each compounds were divided into each number in the relative ratio. The carbon atom number was 16.5 for the indanol, 20 for (ArC1-12)2, and 12 for dibenzil (single-oxygen-bonded carbon atom contributes only 0.5 and double-oxygen-bonded carbon atom contributes 0). The corrected ratio was then indanol/ (ArCH2)2/dibenzil = 2.54 / 0.847/ 0.0833. The product percentages were obtained by dividing each of the corrected numbers by their sum (3.47). at-(2,4,6-Triisopropylphenyl)acetophenone The ketone was irradiated for 48 hr with an uranium sleeve. The products were dissolved in CC13D and characterized. The product ratio was measured by 1H NMR The area ratio of the indanol methyl signal at 0.78 ppm to the cat-methylene proton signal of the the ketone at 4.45 ppm was 0.055. The ratio of the vinyl proton signal of the Z-enol at 6.07 pm to the same methyl signal of the indanol was 3.04. B. InCrystal 230 The following ketones have been irradiated in crystal with the general procedure described above. al-(o-Tolyl)propiophenone The ketone was irradiated for 36 hr, and the products was identified by coinjection with authentic samples on GC as Z-1-methyl—2-phenyl-2-indanol, p—(o-tolyl)propiophenone and benzaldehyde. The product ratio was measured the same way as in the powder reaction. The uncorrected relative ratio was indanol/18/benzaldehyde = 14.03/1.00/270. a-Mesitylpropiophenone The ketone was irradiated for 15 hr to 100% conversion. The major product formed was identified as Z-l,5,7-trimethyl-Z-phenyl—Z-indanol by its identical 1H NMR spectrum taken from the crude product with the authentic sample. There were two small peaks appearing immediately after solvent peak on GC (column #2, 160°C). The area ratio of the indanol to the sum of the small peaks was 99/ 1. or-Mesitylvalerophenone The ketone was irradiated for 15 hr to 100% conversion. The major product formed was identified as Z-S,7-dimethyl-1-propyl-2-phenyl-2-indanol by its identical 1H spectrum taken from the crude product with the authentic sample. A second experiment was conducted. The ketone was irradiated for 10.5 231 hr. The irradiation was stopped while the sample remained as crystal. The major product formed was identified as Z-5,7-dimethyl-1-propyl-2- phenyl-Z-indanol by its identical 1H spectrum taken from the reaction mixture with the authentic sample. The area ratio of the indanol to the starting ketone on GC (column #2, 165°C) was 0.29, indicating a conversion of 23%. There were 5 small peaks on 6C, two of which appeared immediately after solvent peak. The area ratio of the indanol to the sum of the small peaks was 11/ 1. One of the peak was identified as a-mesitylacetophenone, and another 4,6-dimethyl-2—phenyl-Z-indanol (type 11 products) by coinjection with authentic samples on GC. The area ratio of the two peaks to the indanol was 0.0165/1 and 0.0382/1 respectively, which was then corrected by the response factors listed in Appendix and became 0.0192/1 and 0.0422/1. at-Mesityl-d-Phenylacetophenone The ketone was irradiated for 10 days. Since the photoproducts were solid which remained where they were formed, preventing light from penetrating the sample, the reaction seemed to occur only on the surface of the sample. The NMR of the reaction mixture showed that the major prOduct was Z-5,7-dimethyl- 1,2-diphenyl-2-indanol (>90%). The enol ethers were not detected by NMR. The area ratio of the methyl signal of the indanol at 2.37 ppm to the ortho benzoyl proton signal of the starting ketone at 7.9 ppm was 1.35, indicating a conversion of 47%. VI. Irradiation in Cyclodextrin Complexes The cyclodextrin complexes of the ketones were prepared by the 232 following general procedure. The ketones (1 equiv, 0.05-0.20 g) were added to aqueous cyclodextrin solutions (1 equiv). The solutions were stirred overnight. The precipitated complexes were filtered, washed with ether, and dried at 65°C in an oven for 12 hr. at -(o-Tolyl)propiophenone, a-(o-tolyl)valerophenone, o:-(o-tolyl)-isobutyrophenone all formed complexes with p-cyclodextrin. ot-Mesitylpropiophenone, ct-mesitylvalero- phenone did not form complexes with p-cyclodextrin, however they did form complexes with y-cyclodextrin. The saturated aqueous solutions of the complexes (approx. 0.05 g in 500 ml) were irradiated for 36 hr in an irradiator with a medium pressure mercury lamp under argon. The products were extracted with chloroform until no more products could be extracted, and identified by coinjection with authentic sample on GC. ol-(o-Tolyl)isobutyropropiophenone All the products have very short retention times on GC with a Magabore DB210 column, indicating the products from cleavage. Benzaldehyde was identified by coinjection with authentic sample on GC. q-Mesitylpropiophenone The major product was Z-1,5,7-trimethyl-2-phenyl-2-indanol, and very small amount of E-,5,7-Trimethyl-2-Phenyl-2-Indanol was also identified, by coinjection with authentic samples on GC. The Z/E ratio was 40/ 1. 233 VII. Dynamic N MR Measurements All the low temperature N MR studies were performed on a Bruker 250 MHZ NMR spectrometer with the chosen solvent depending on the temperature ranges. CD03 was used for at-mesitylvalerophenone. Acetone-d6 was used for ot-mesitylpropiophenone. A mixture of CD202 and methanol-d4 (7:1) was used in the cases of or-(o-tolyl)isobutyrophenone and or-mesitylisobutyrophenone. A mixture of ethanol-d6 and acetone-d6 was used for d-mesityl-ot-phenylacetophenone. The temperature ranges within which DNMR measurements were conducted was 170K-300K for ct-(o-tolyl)isobutyrophenone, tat-mesityl- isobutyrophenone, and ot-mesityl-ot-phenylacetophenone, 200K-320K for ol-mesitylpropiophenone, and 220K-350K for ot-mesitylvalerophenone. Equation (2) was used to calculated the rotational rate constants at various temperatures. The linewidths of the broadened merged peaks along with the differences in Chemical shift of the separated signals were accessed. The linewidths was measured mannually by means of a magnifying glass and a 0.5 mm ruler. For ct-(o-tolyl)isobutyrophenone, its a-methyl signals were measured; for d-mesitylpropiophenone, a-mesitylvalerophenone, their mesityl o-methyl signals; for a-mesitylisobutyrophenone, its d-methyl as well as mesityl o-methyl signals; for ct-mesityl-ot-phenylacetophenone, its m-mesityl proton signals, which was due to the difficulty in measuring its mesityl o-methyl signals caused by overlapping with the p-mesityl methyl signal. The raw data are given in Appendix. 234 VIII. Molecular Mechanism Calculations The calculations were performed on an IBM PC with an enchanced graphics adaptor. MMPMI, an advanced version of MM2 with MMP1 Pi subroutines incorporated for delocalized Pi electron systems by Allinger, was used for molecular mechanics calculations. STRPI incorporated in MIO by Gilbert and Gajewsk was used to generate the structural input for MMPMI. The additional software were a 4027 emulator and Microsoft Pcplot3 (V3.6). ° Two dihedral angle drive options were available with MMPMI. The use of dihedral angle drive could insure the findings of all the local minima. The calculations were generally done in the following way. A structural input was generated with MIO, and submitted to MMPMI for calculations. The resulting output structure was then reput into MMPMI for a second calculation. The purpose of this procedure was to supply MMPMI with a better input structure. The second calculation was performed with a dihedral angle drive operating first regarding the Ca-CO bond rotation; then this rotation was fixed at angles producing conformations with minimized energies, and a second dehedral angle drive was applied to the rotation of the a-aryl group. Combinations of the two dihedral drives provided the conformations with energetic minima regarding Cq-CO and CQ-Ar bond rotations. Finally, these energy-minimized structures were used as inputs for calculations without dihedral angle drive for verifications. For p-arylpropiophenones, there were three bond rotations that need to be examined, CQ—CO, Cq-Cp, and Cp—Ar. The two dihedral drives were not 235 enough to do calculations with three angles fixed. Thus the third dihedral drive was done by rotating the p-aryl group without fixing the first two dihedral angles. The results showed that rotation of the p-aryl group did not change the first dihedral angles from where they were input, as was hoped. IX. X-Ray Crystallography Samples of or-mesityl-2,4,6-trimethylacetophenone, cat-mesityl- valerophenone, and o:-mesityl-ot-phenylacetophenone were dissolved in ethanol in a vial. The resulted solution was then poured in a Petri dish, and allowed to stand for 2-3 days until the crystal started to grow. The solvent was removed by a disposable pipet, and the crystal was washed quickly with cold ethanol, and dried by air. The samples were submitted to Dr. D. Ward. The data collections were performed with Mo K01 radiation ()1 = 0.71073 A) on a Nicolet P3F diffractometer. The structures were solved by direct methods. The X-ray structures of the ketones are given in the result section (Figure 27-29), and the crystallographic parameters are presented in the appendix. Appendix 237 Table 24. Kinetic Data of C Q-CO Bond Rotation for ot-(o-Tolyl)- isobutyrophenone Av = 0.24 ppm = 60 Hz, (.0 (300K) = 0.007 ppm NO 185 190 195 200 (0(ppm) 0.20 0.09 0.06 0.03 (D(HZ) 50 22.5 15 7.5 k(s'1) 156 282 399 896 1 /Tx103 5.41 5.26 5.13 5.00 lnk 5.05 5.64 5.99 6.63 Table 25. Kinetic Data of Ca-Mes Bond Rotation for ol-Mesityl- propiophenone Av = 0.69 ppm = 173 Hz, (0(320K) = 0.013 ppm T(K) 250 260 270 280 290 u)(ppm) 0.30 0.17 0.09 0.05 0.03 (D(Hz) 75 42.5 22.5 12.5 7.5 lt(s‘1) 723 1170 2117 3770 6260 1 /Tx103 4.00 3.85 3.70 3.57 3.45 lnk 6.58 7.06 7.66 6 23 8.74 Table 26. Kinetic Data of C a-Mes Bond Rotation for ol-Mesityl- Av : 0.56 ppm : 140 Hz, (0(330K) : 0.02 ppm valerophenone r00 280 290 300 310 320 w(ppm) 0.20 0.16 0.09 0.06 0.04 (0(Hz) 50 40 22.5 15 10 k(s'1) 625 827 1400 2070 3090 I/Tx103 3.57 3.45 3.33 3.23 3.13 Ink 6.44 6.72 224: LQL 8.04 Table 27. Kinetic Data of CQ-CO Bond Rotation for d-Mesityl- isobu tyrophenone Av = 0.19 ppm = 48 Hz, (0(300K) = 0.003 ppm T(K) 185 190 . 200 210 (D(ppm) 0.22 0.12 0.05 0.03 (0012) 55 30 12.5 7.5 k(s‘1) 89 152 305 489 1/Tx103 5.41 5.26 5.00 4.76 lnk 4.49 5.02 5.12 6.19 239 Table 28. Kinetic Data of Ca-Mes Bond Rotation for ol-Mesityl- isobu tyrophenone Av = 0.72 ppm = 180 Hz, (D(BOOK) = 0.005 ppm T(K) 210 220 230 240 w(ppm) 0.14 0.06 0.03 0.02 60012) 35 15 7.5 5 k(s'1) 1510 3410 6790 10200 1/Tx103 5.41 5.26 5.13 5.00 lnk 5.12 5.63 . ' 6.14 6.80 Table 29. Kinetic Data of COL-Mes Bond Rotation for a-Mesityl-ol- Phenylacetophenone Av = 0.26 ppm = 64 Hz, (0(300K) = 0.007 ppm T(K) 180 185 190 210 230 (D(ppm) 0.29 0.19 0.11 0.02 0.014 u)(Hz) 725 47.5 275. 5 2.5 k(s'1) 125 184 273 1314 2616 1/Tx103 5.56 5.41 5.26 4.76 4.35 lnk 4.83 5.21 5.61 7.18 7.87 240 Table 30. Quenching Indanol Formation from ot-(o-Tolyl)-p- Methoxyaceto henone with 2,5-Dimethyl-2,4-Hexadiene in Benzene at 31 nm HPLC anal sis with ultras here Si column Hexane/ e yl acetate 95: , 1.5 ml/ min Methyl benzoate as internal standard (0.00264 M) [Q]. 104 M A(photo)/A(std) 52°le>___ 0.000 0.782 (0.778, 0.786) 0.880 0.641 1.20 1.76 0.492 1.59 3.51 0.399 1.96 4.33 0.348 2.25 5.20 0.310 2.52 [Ketone] = 0.015 M, [Indanol] = 0.000782 M Table 31. Quenching Benzaldehyde Formation From a-(o-Tol(yl)— gapiophenone with Naphthalene in Benzene with .007 M ecanthiol at 365 nm HPLC analtysis with ultras here Si column Haxane/e yl acetate 99: , 1.2 ml/ min Octyl benzoate as internal standard (0.00726 M) IQI, 10’2 M A(photo)[A(stdL 52°19.— 0.00 0.726 (0.714, 0.738) 1.36 0.407 1.78 2.72 0.228 3.18 5.45 0.120 6.05 8.17 0.0825 8.80 9.53 0.0727 9.99 [Ketone] = 0.042 M, [Benzaldehyde] = 0.00482 M 241 Table 32. Quenching Benzaldehyde Formation from ol-(o-Tolyl)- ro iophenone with Naphthalene in Benzene with 0.007 M ecanthiol at 365 nm HPLC analtysis with ultras here 5i column Haxane/e yl acetate 99: , 1.2 ml/ min Octyl benzoate as internal standard (0.00810 M) [Q]. 10'2 M A(photo)jA(std) 52°L<12___ 0.00 0.698 0.508 0.506 1.38 1.02 0.369 1.89 1.52 0.278 2.51 2.03 0.242 2.88 254 0217 3.2L [Ketone] = 0.045 M, [Benzaldehyde] = 0.00517 M Table 33. Quenchin a-(o—Tolyl)acetophenone Formation from d-(o-Toly valerophenone with 2,5-Dimethyl-2,4—Hexadiene in Benzene at 313 nm 6C analysis with column #1, 230°C Pentadecane as internal standard (0.00930 M) [QL 10'1 M A(ph6to)/A(std) 43°ng 0.00 0.207 (0.207, 0.206) 0.260 0.118 1.75 0.520 0.0807 2.56 0.780 0.0649 3.19 1.04 0.0533 3.88 1.56 0.0386 5.36 [Ketone] = 0.028 M, [Product] = 0.00222 M 242 Table 34. Quenenching ot-(o-Tolyl)aceto henone Formation from . ol-(o-Tolyl)valerophenone wi 2,5-Dimethyl-2,4-Hexadiene in Benzene at 313 nm GC analysis with column #1, 230°C Pentadecane as internal standard (0.00388 M) [Q]. 10-2 M A(photo)/A(std) 40L.-. 0.00 0.347 (0.362, 0.332) 0.520 0.283 1.23 1.04 0.257 1.35 1.56 0.231 1.50 2.08 0.225 1.54 2.60 0.208 1.67 3g 0.184 1.89 [Ketone] = 0.020, [Product] = 0.00155 M 243 Table 35. Quenching Benzaldeh de Formation from ct-(o-Tolyl)- isobu ophenone wi Naphthalene in Benzene wrth 0.007 M Do ecanthiol at 365 nm HPLC analtysis with ultras here 5i column Haxane/ e yl acetate 99: , 1.2 ml/ min Octyl benzoate as internal standard (0.00718 M) [Q], 10'2 M A(photo)/A(stj1L 4°15]; 0.00 0.814 (0.817, 0.811) ' 0.942 0.401 202 1.88 0.248 3.31 2.83 0.184 4.42 3.77 0.143 5.69 4.71 0.124 6.56 5.65 0.104 7.83 [Ketone] = 0.035 M, [Benzaldehyde] = 0.00536 M Table 36. Quenching Benzaldeh de Formation from a-(o-Tolyl)- isobutyrophenone wi Na hthalene in Benzene with 0.007 M Dodecanthiol at 36 nm HPLC analtysis with ultras here 5i column . Haxane/ e yl acetate 99: , 1.2 ml/ min ' Octyl benzoate as internal standard (0.00800 M) [QL 10'2 M A(photo)/A(std) QOL 0.00 0581 (0.572, 0.590) 0.22 > 0.484 1.20 0.44 0.385 151 0.66 0.352 1.65 0.88 0.301 1.93 1.11 0.270 $.15 [Ketone] = 0.045 M, [Benzaldehyde] = 0.0042 M 244 Table 37. Quenching Indanol Formation from ot-Mesitglpropio- phenone with Naphthalene in Benzene at 36 nm 6C analysis with column #1, 250°C Octadecane as internal standard (0.00738 M) [Q]. 10-2 M A(photo)/A(std) 42°22 0.00 0.367 (0.370, 0.364) 1.87 0.271 1.35 3.74 0.221 1.66 5.62 0.185 1.98 7.49 0.164 .2.24 9.36 0.144 2.55 10.3 0.111 ' ‘ 3.31 [Ketone] = 0.027 M, [Indanol] = 0.00290 M Table 38. Quenching Indanol Formation from ct-Megigzlpropio- phenone with Naphthalene in Benzene at nm 6C analysis with column #1, 250°C Octadecane as internal standard (0.00351 M) [(21,104 M A(_photo)/A(§t_<_i) 52°19 0.00 0.538 (0.551, 0.525) 0.368 0.294 1.83 0.735 0.226 2.38 1.10 0.171 3.15 1.47 0.1g 3.78 [Ketone] = 0.025 M, [Indanol] = 0.00202 M 245 Table 39. Quenching Indanol Formation from a-Mesi lvalero- phenone with Naphthalene in Benzene at nm GC analysis with column #1, 250°C N onadecane as internal standard (0.00573 M) [Q]. 10'1 M A(photo)1 A(stc_l) AW 9 0.00 0.436 (0.432, 0.441) 0.871 0.323 1.35 1.74 0.246 1.77 2.61 0.200 2.13 3.48 0.158 2.75 4.35 0.125 3.49 5.22 0.107 4.07 6.09 - 0.0915 4.77 [Ketone] = 0.033 M, [Indanol] = 0.00287 246 Table 40. Quenching Indanol Formation from ot-Mesi lvalero- phenone with Naphthalene in Benzene at nm 6C analysis with column #2, 165°C N onadecane as internal standard (0.00718 M) [Q]. 10-1 M A(photo)/A(std) SIP/L. 0.00 0.551 (0.537, 0.564) 0.964 0.381 1.45 1.93 0.284 1.94 2.89 0.228 2.42 3.85 0.190 2.90 4.82 0.160 3.44 5.78 0.132 4.17 6.75 0.112 4.92 8.67 0.0842 654 10.6 0.0687 8.02 12.5 0.00516 10; [Ketone] = 0.047 M, [Indanol] = 0.00455 247 Table 41. Quenching Benzaldeh de Formation from d-Mesityl- isobutyro henone wit Na hthalene in Benzene wrth 0.007 M ecanthiol at nm HPLC analtysis with ultras here Si column Hexane/ e yl acetate 99: ,1.2 ml/ min Octyl benzoate as internal standard (0.00688 M) [QL M A(photo)/A(std) AOL. _. 0.000 0.290 (0.289, 0.284, 0.297) 0.103 0.159 1.82 0.206 0.115 2.52 0.309 0.0904 3.21 0.412 0.0706 4.11 0.515 0.0588 4.74 [Ketone] = 0.022 M, [Benzaldehyde] = 0.00182 M Table 42. Quenching Benzaldeh de Formation from d-Mesityliso- bu o henone with aphthalene in Benzene with 0.007 M ecanthiol at 365 nm HPLC analtysis with ultras here 5i column Hexane/ e yl acetate 99: , 1.2 ml/ min Octyl benzoate as internal standard (0.00663 M). [01.10‘1 M A(photo)[A(std) 520/512 0.000 0.311 (0.301, 0.320) 0.557 0.257 1.21 1.11 0.214 1.45 1.67 0.166 1.87 2.23 0.139 J2_;3_ [Ketone] = 0.023 M, [Benzaldehyde] = 0.00188 M 248 Table 43. Quenching Indanol Formation from e-Mesityl-ot-Phenyl- acetophenone with 2,5-Dimethyl-2,4-Hexadiene in Benzene at 365 nm HPLC analtysis with ultras here Si column Hexane/ e yl acetate 99: , 1.2 ml/ min Methyl benzoate as internal standard (0.00870 M) [O]. M A(ghoto)/ Ami fioL 0.00 0.257 (0.256, 0.258) 0.167 0.225 1.14 0.334 0.200 1.29 0.500 0.179 1.44 0.834 0.151 1.71 1.00 0.132 1.95 1.57 0.104 2.47 [Ketone] = 0.033 M, [Indanol] = 0.00175 M 249 Table 44. Quenching Indanol Formation from ot-Mesityl-ot-Phenyl- aceto henone with 2,5-Dimethyl-2,4-Hexadiene in Hexane at 36 nm HPLC anal sis with ultras here Si column Hexane/ ethyl acetate 99: , 1.2 1111/ min Methyl benzoate as internal standard (0.00430 M) [O], M A(photo)/A(std) 52°12 __. 0.00 0.159 0.265 0.140 1.14 0.529 0.103 1.54 0.793 0.0826 1.92 1.32 0.0712 2.24 1.59 0.06121 2.56 . [Ketone] = 0.027, [Indanol] = 0.000539 250 The area ratios of the enol ethers (ketone 8, 9, 10) to the standards are ‘ven in a combined form for the Z and E ' mers, an orrected by 0% response f tors A( hoto)/A(std) = [A (photo) «1- A (photo) ] /A(std . The ratios of 2/ E isomers at ° erent ketone conversions are given in table 64. Table 45. Quenching Aryl Vinyl Ether Formation from d-Mesityl-ot- Phenylaceto henone with 2,5-Dimethyl-2,4-Hexadiene in Hexane at 5 nm HPLC analtysis with ultras here Si column Hexane/ e yl acetate 99: , 1.2 ml/ min Methyl benzoate as internal standard (0.00432 M) [O]. M A(photo)/ A std a 0°19— 0.00 0.159 (0.158, 0.159) 0.265 0.130 1.2.2 0.529 0.113 1.41 0.794 0.0957 1.66 1.06 0.0862 1.84 1.32 0.0772 2.05 1.59 0.0714 2.22 fizgl 0.0574 #277 [Ketone] = 0.027 M, [Enol Ether] = 0.000687 251 Table 46. Quenching Indanol Formation from a-Mesityl-ol-Phenyl- gMethoxyacetophenone with Naphthalene In Benzene at 5 nm HPLC analtysis with ultras here 5i column Hexane/ e lacetate 97: , 1.2 ml/min Butyl p-me oxybenzoate as internal standard (0.00300 M) [QL 10'1 M A(photo)/A(std) 20L 0.00 0.225 (0.227, 0.223) 0.0133 0.149 1.51 0.0268 0.104 2.16 0.0399 0.0784 2.88 0.0532 0.0658 3.42 0.0665 0.0558 4.03 [Ketone] = 0.037 M, [Indanol] = 0.00196 M Table 47. Quenching Indanol Formation from a-Mesityl-ol-Phenyl- p-Methoxyacetophenone with Naphthalene m Benzene at 365 nm HPLC anaiysis with ultrasphere Si column Hexane/ e edyl acetate 97: ,1.2 rnl/ min Butyl p-m oxybenzoate as internal standard (0.00602 M) [QL 10‘1 M A(photo)[ Ag std) AW Q 0.00 0.281 (0.275, 0.287) 0.00984 0.170 1.65 0.0197 0.132 2.13 0.0295 0.115 2.44 0.0394 0.0926 2.88 0.0492 0.0849 3.31 [Ketone] = 0.047 M, [Indanol] = 0.00491 M 252 Table 48. Quenchin 1 Vinyl Ether Formation from ol-Mesityl-ot- Phenyl-p- et oxyacetophenone with Naphthalene in Benzene at 365 nm HPLC anal sis with ultras here Si column Hexane/ e dyl acetate 97: , 1.2 ml/ min Butyl p-me oxybenzoate as internal standard (0.00300 M) [QL 10'1 M A(_photcfl[A(std) 52°L42. 0.00 0.231 (0.227, 0.235) 0.0133 0.147 1.57 0.0268 0.108 2.14 0.0399 0.0846 2.73 0.0532 0.0731 3.16 0.0665 0.0605 3.8L [Ketone] = 0.037 M, [Enol Ether] = 0.000693 M Table 49. Quenchin 1 Vinyl Ether Formation from ol-Mesityl-a- Phenyl-p- e oxyacetophenone with Naphthalene in Benzene at 365 nm HPLC anal sis with ultras here Si column Hexane/ e l acetate 97: , 1.2 ml/ min Butyl p-me oxybenzoate as internal standard [0.00602 M] [01 10'1 M A(photo)/A(std) 4°19 0.00 0.272 (0.276, 0.268) 0.00984 0.188 1.45 0.0197 0.137 1.98 0.0295 0.119 228 0.0492 0.0862 3.16 [Ketone] = 0.047 m, [Enol Ether] = 0.00164 M 253 Table 50. Quenching Aryl Vinyl Ether Formation from or-Mesityl- or-Phenyl-p-Cyeanoacetophenone with 2,5-Dimethyl-2,4- Hexadiene in nzene at 365 nm HPLC analflysis with ultras here 5i column Hexane/e yl acetate 95: , 1.2 ml/ min Benzene as internal standard (0.00580 M) [Q], 10-1 M A(photo)/ A(std) Q°IL_ 0.00 0.0729 (0.0747, 0.0712) 0.244 0.0550 133 0.488 0.0452 1.61 0.732 0.0369 1.98 0.976 0.0341 214 1.22 0.0293 ' 249 1.46 0.0264 42.76 [Ketone] = 0.015 M, [Enol Ether] = 0.000423 M Table 51. Quenching Mesitaldehyde Formation from d-Phenyl-2,4,6- Trimethylaceto henone with 2,5-Dimethyl-2,4-Hexadiene in Benzene wit 0.007 M Dodecanthiol at 313 nm HPLC analtysis with ultras here Si column Hexane/ e yl acetate 99: , 1.2 ml/ min Octyl benzoate as internal standard (0.00938 M) [O]. M A(photo)/A(st;l) . 52019—— 0.00 0.737 (0.731, 0.744) 0.127 0.577 1.28 0.253 0.387 1.90 0.380 0.294 2.50 0.506 0.261 2.82 0.633 0.218 3.40 0.760 0.193 % [Ketone] = 0.021 M, [Mesitaldehyde] = 0.000465 M 255 Table 52. Quenching Indanol Formation from or-Mesityl-o-Methyl- acetophenone with Naphthalene in Benzene at 365 nm 6C analysis with column #1, 250°C Nonadecane as internal standard (0.00600 M) [(21.101 M A(photo)llflgti 5120292..-. _ 0.00 0.472 (0.461, 0.483) 0.125 0.352 1.34 0.251 0.311 1.52 0.376 0.274 1.72 0.501 0.230 2.05 0.626 0.217 2.18 0.752 0.193 245 [Ketone] = 0.040 M, [Indanol] = 0.00360 M Table 53. Quenching Indanol Formation from ct-Mesityl-o-Methyl- acetophenone with Naphthalene in Benzene at 365 nm 6C analysis with column #1, 250°C Nonadecane as internal standard (0.00356 M) [OL 10‘1 M A(Dhoto)[A(std) 5h°19 0.00 0.859 0.775 0.687 1 .25 1 .55 0.636 1 .35 2.33 0.51 1 1.68 3.10 0.452? 1 .90 [Ketone] = 0.033 M, [Indanol] = 0.00356 M Table 54. Quenching Mesitaldehyde Formation from cat-Mesityl- 2,4,6-Trimethylacetophenone with 2,5-Dimeth l-2,4- Hexadiene in Benzene with 0.007 M Dodecant '01 at 313 nm HPLC anal sis with ultras here Si column Hexane/ethyl acetate 99: , 1.2 ml/ min Octyl benzoate as internal standard (0.00864 M) 101 10-1 M A(photo)/A(std) 52°22 __ 0.000 1.95 (1.87, 2.03) 0.383 1.71 1.14 0.765 1.45 1.34 1.15 1.12 1.74 1.53 0.941 2.07 2.30 0.632 3.09 3.44 0.504 3.87 4.59 0.470 4.15 5.74 0.404 #483 [Ketone] = 0.021 M, [Mesitaldehyde] = 0.00113 M 257 Table 55. Quenching Mesitaldehyde Formation from tat-Mesityl- 246-Trimethylacetophenone with 2,5-Dimeth l-2,4- Hexadiene in Benzene with 0.007 M Dodecant '01 at 313 nm HPLC anal sis with ultras here Si column Hexane/ethyl acetate 99: , 1.2 ml/ min Octyl benzoate as internal standard (0.00854 M) [Q], 10‘1 M A(photm/ A(std) 52019—— 0.000 1.39 (1.40, 1.38, 1.40) 0.220 1.19 1.17 0.440 1.12 1.25 0.659 1.01 1.38 0.879 0.913 1.53 1.10 0.874 1.59 1.32 0.809 1.72 1.76 0.645 2.16 2.20 0.525 2.65 2.42 0.451 3.09 3.08 0.366 3.81 3.74 0.346 4.03 4.40 0.315 4Q 5.06 0.296 4.71 6.37 0.254 5.48 7.20 0.234 5.95 7.92 0.215 6.48 8.64 0.208 6.70 9.36 0.190 7.33 [Ketone] = 0.020 M, [Mesitaldehyde] = 0.000789 M Table 56. Quenchin Mesitaldeh de Formation from d-Mesityl-ct- Phen 1-2, ,6-Trimethy acetophenone with 2,5-Dimethyl— 2,4- exadiene in Benzene w1th 0.007 M Dodecanthiol at 313 n HPLC analtysis with ultras here 5i column Hexane/ e l acetate 99: , 1.2 ml/ min Butyl p-me oxybenzoate as internal standard (0.00730 M) [QL M A(photo) [A(std) 52°19.— 0.000 0.583 (0.600, 0.561, 0.588) 0.244 0.464 1.26 0.487 0.441 1.32 0.741 0.403 1.45 0.975 0.360 . 1.62 1.34 0.289 2.02 1.70 0.279 92.09 [Ketone] = 0.026 M, [Mesitaldehyde] = 0.00165 M 259 Table 57. Quenchin Mesitaldeh de Formation from d-Mesityl-a- Phen 1-2, ,6-Trimethy acetophenone with 2,5-Dimethyl— 2,4- exadiene in Benzene wrth 0.007 M Dodecanthiol at 313nm HPLC analtysis with ultras here Si column Hexane/ e lacetate 99: , 1.2 ml/ min Butyl p-me oxybenzoate as internal standard (0.00681 M) [01 M A(photo)/A(std) 52°19. 0.000 0.510 (0.504, 0.516) 0.394 0.389 1.31 0.788 0.295 . 1.73 1.18 0.256 1.99 1.97 0.196 - ' 260 ' [Ketone] : 0.028 M, [Mesitaldehyde] : 0.00135 M Table 58. Quenching Tetralol Formation from p-(o-Tolyl)- isobutyrophenone with 2,5-Dimethyl-2,4-Hexadiene in Benzene at 313 nm 6C analysis with column #2, 155°C Eicosane as internal standard (0.00850 M) [QLM A(Qoto)/A(§td) 512°Lsk__ 0.000 0.0254 0.109 0.0143 1.78 0.218 0.00897 283 0.327 0.00715 3.60 0.435 0.00557 4.56 0.544 ' 0.00470 5.39 [Ketone] = 0.059 M, [Tetralol] = 0.000250 M 260 Table 59. Quenching Tetralol Formation from p-Mesitylisobutyro— henone with 2,5-Dimethyl-2,4-Hexadiene in Benzene at 13 nm GC analysis with column #3, temperature programming, 90°C for 5 min, 5°c/ min to 160°C. Nonadecane as internal standard (0.00658 M) [Q]. 10‘1 M A(photo)/ A(std) 9901.0" 0.000 0.264 (0.274, 0.264) 0.964 0.175 1.51 1.93 0.134 1.97 2.89 0.104 2.54 3.87 0.0864 3.06 4.842 0.0730 3.6; [Ketone] = 0.042 M, [Tetralol] = 0.00230 M Table 60. Quenching Tetralol Formation from p—Mesitylisobutyro— phenone with 2,5-Dimethyl-2,4-Hexadiene in Benzene at 13 nm 6C analysis with column #3, temperature programming, 90°C for 5 min, 5°c/ min to 160°C. Nonadecane as internal standard (0.00706 M] [Q]. 101 M A(photo)/A(std) 52°L__ 0.000 0.222 0.452 0.166 1.34 0.905 0.145 1.53 1.36 0.108 205 2.27 0.0899 4,47 [Ketone] = 0.046 M, [Tetralol] = 0.00207 M 261 Table 61. Quenching Tetralol Formation from p-Mesi lpropio- henone with 2,5-Dimethyl-2,4-Hexadiene in nzene at 13 nm GC analysis with column #1, 160°C Eicosane as internal standard (0.00346 M) [O]. M A(photo)/ A(std) QOL 0.000 0.0751 (0.0738, 0.0764) 0.113 0.0527 1.43 0.227 0.0376 2.00 0.340 0.0298 2.52 0.454 0.0234 3.21 0.567 0.0187 4.02 [Ketone] = 0.052 M, [T etralol] = 0.000320 M 262 Table 62. 6C Response Factors Componds Standard Conditiona_gf_ Z-1-Methyl-2-Phenyl-2-Inda_nol Heptadecane #1, 210°g_1_._12 g—(o-Toly12acetophenone Pentadecane #1 230°c_1_.15_ Z-1,5,7-Trimethyl-2-Phenyl-g-Indamil Octadecane #1 250°___1_._0_7 E-1,§,7-Trimethyl- -I>heny1-2-Indan61 Octadecane #1 250°e_10_7 lflersitoxl-l-Phenylmpene Octadecane #1 250°_1_.0_6 Z-5,7-Dimethyl-2-Phenyl-1-propyl-2-Indanol Nonadecane #1, 250°_fi5 3::Dimethyl-2-(o-Toly12indene Nonadecane #1 , 250°ng kMethxl-l,2,3,4-Tetl'ahydrO-2-Tetralol lame #2, 155°C 1.16 5,7-Dimethyl-1,Zé,4-Tetrahydro-2-Tetralol Eigane #2I 160°C 1.23 35,7-Trimethyl-1,23,4-Tetrahydro-2-Tetralol Nonadecane T Programb 1.32 Heptadecane #4, 100°C 2.57 Benzaldehyde Pentadecane T Prggram°_2_.1_6 gMethogbenzaldehyde Pentadecane T Program°_2._22_ gymgbenzaldehyde PentadecaneTPrggram°_2_.1_§ 4,6-Dimethyl-2-Phenyl-2-Indanol Nonadecane #2, 1fi°g_1._27_ g-Mesitylacetophenone Nonadecane #2 165° 1.34 a. Column #, temperature. b. #3, 90°C for 5 min, 5°c/ min to 160°C. c. #3, 70°C, for 8 min, 5°c/ min to 130°C. (1. #3, 80°C, for 8 min, 5°c/ min to 130°C. 263 Table 63. HPLC Response Factorsa Compounds Z-SgMethomhenyl)-2-Indanolb 3“EDirnethyl-Z-phenyl-2-Indanolc Standard R4; Methyl Benzoate 0.379 Methyl Benzoate 0.767 4,6-Diisopropyl-l,1-Dimethyl- g-Phenyl-g-IndanolC 3,5-Dimethoxy benzonitrile 1.64 Z-5,7-Dimethyl-1,2-Diphen3Ll-2-Indanold Methyl Benzoate 0.784 E-l-Mesitoxy-1,2-Diphenylethylened Methyl Benzoate 0.212 Z-l-Mesitoxy-1n3-Diphenylethfiened Methyl Benzoate 0.115 Z—5,7-Dimethyl-2-(p—Methoxyphenyl)- 1-Phenyl-2-Indanole E-1-Mesitoxy-l-(p-Methoxyphenyl)- Butyl gMethoxybenzoate 2.90 2-Phenylethylenee Z-l-Mesitoxy-1-(p-Methoxyphenyl)- 2--Phenylethylenee Butyl gMethoxybenzoate 0.391 Bugl zMethoxybenzoatg 0.328 Z-5,7-Dimethyl-Z-(p—Cyanophenyl) 1-Phenyl-2-Indanof hlorobe l anid 0.175 E-1-Mesitoxy-1-(p—Cyanophenyl)- 2-Phenylethylenef Morobelzyl Cyanide 0.0469 Z-1-Mesitoxy-1-(p-Cyanophenyl)- 2-Phenylethylenef hloro 1C anide 0.0224 Methyl Benzoate 0.960 Benzaldehyded Octyl B_e_nzo_a_t_e 0.914 o-Tolaldehyded Octyl Benzoate ' 1.18 Butyl p-Methoxybenzoate 0.388 Mesitaldehyded We 0.0672 264 Table 63 (cont'd) a. 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Kg? 82 «We ofimifld finiéggjj m: amiamaswu 38.53 Nowfiofid +$.m+8.n 83 «we «1H,—«Maia wanna“; 9:83 8 03g 274 Table 67. X-Ray Crystallographic Parameters for. a-Msitylvalerophenone 6 275 Table of Bond Angles (in Degrees) for a-mesitylvalerophenone Atoml Atom2 Atom3 Angle C2 C1 C6 120.2(2) C1 C2 C3 120.4(2) C2 C3 C4 119.7(2) C3 C4 C5 120.4(2) C4 C5 C6 120.9(2) C1 C6 C5 118.5(2) C1 C6 C7 123.4(2) C5 C6 C7 118.1(2) 01 C7 C6 119.9(2) 01 C7 C8 120.3(2) C6 C7 C8 119.7(2) C7 C8 C9 115.0(1) C7 C8 C18 110.3(2) C9 C8 C18 113.5(2) C8 C9 C10 121.5(2) C8 C9 C14 119.6(1) C10 C9 C14 118.8(1) C9 C10 C11 119.6(2) C9 C10 C15 123.3(1) C11 C10 C15 117.2(2) C10 C11 C12 122.1(2) C11 C12 C13 117.8(2) C11 C12 C16 120.8(2) C13 C12 C16 121.4(2) 276 Table of Bond Angles (Continued) for a-mesitylvalerophenone Atoml AtomZ Atom3 Angle C12 C13 C14 122.5(2) C9 C14 C13 119.2(2) C9 C14 C17 123.4(1) C13 C14 C17 117.4(2) C8 C18 C19 114.3(2) C18 C19 C20 111.7(2) C2 C1 H1 120.(1) C6 C1 H1 119.(1) C1 C2 H2 120.(1) C3 C2 H2 . 120.(1) C2 C3 H3 122.(2) C4 C3 H3 119.(2) C3 C4 H4 118.(2) C5 C4 H4 121.(2) C4 C5 HS 123.(1) C6 C5 H5 116.(1) C7 C8 H8 103.(1) C9 C8 HS 108.8(9) C18 C8 88 105.3(9) C10 C11 H11 117.(l) C12 C11 H11 120.(1) C12 C13 H13 120.6(8) C14 C13 .H13 116.8(8) C10 C15 3158 110.(2) 277 Table of Bond Angles (Continued) for a-mesitylvalerophenone Atoml AtomZ Atom3 Angle C10 C15 Hle 114.(2) C10 C15 H15c 109.(2) H15a C15 Hle 108.(2) 815a C15 H15c 110.(2) H15b C15 H15c 105.(2) C12 C16 816a 115.(1) C12 C16 Hl6b 110.(1) C12 C16 H16c 118.(2) H16a C16 Hl6b 108.(3) H16a C16 H16c 106.(2) H16b C16 H16c 98.(3) C14 C17 817a 112.(1) C14 C17 H17b 117.(1) C14 C17 Hl7c 116.(2) H17a C17 H17b 105.(2) 317a C17 817: 105.(2) H17b C17 817: 100.(2) C8 C18 H18a 108.(1) C8 C18 H18b 108.(1) C19 C18 H18a 110.(1) C19 C18 Hle 104.(1) H18a C18 H18b 112.(2) C18 C19 H19a 106.(1) C18 C19 HlQb 108.(1) 278 Table of Bond Angles (Continued) for a-mesitylvalerophenone Atoml Atom2 Atom3 Angle C20 C19 819a 107.(l) C20 C19 Hl9b 111.(l) H19a C19 H19b 112.(2) C19 C20 H20a 113.(2) C19 C20 H20b 110.(2) C19 C20 H20c 112.(2) H20a C20 H20b 101.(2) H20a C20 H20c 103.(2) H20b C20 HZOc 117.(2) Numbers in parentheses are estimated standard deviations in the least significant digits. Tat 279 Table of Bond Distances (in Angstroms) for a—mesitylvalerophenone Atoml Atom2 Distance 01 07 1.216(3) 01 02 1.391(3) 01 C6 1.387(3) 02 03 1.380(4) 03 04 1.375(4) 04 05 1.375(4) 05 C6 1.396(3) C6 07 1.491(3) 07 C8 1.537(3) C8 09 1.530(2) C8 C18 1.539(3) 09 010 1.402(2) 09 014 1.411(3) 010 011 1.392(2) 010 015 1.518(3)’ 011 012 1.380(3) 012 013 1.379(3) 012 C16 1.517(2) 013 014 1.390(2) 014 017 1.512(3) C18 019 1.512(3) 019 020 1.536(3) 01 a1 0.94(2) C2 HZ 0.95(2) ZN) Table of Bond Distances (Continued) for a-mesitylvalerophenone Atoml Atom2 Distance C3 H3 0.98(3) C4 H4 1.04(3) C5 HS 0.98(2) C8 88 l.02(2) C11 H11 1.04(2) C13 H13 0.94(2) C15 HlSa 0.93(2) C15 H15b l.03(2) C15 8150 1.00(3) C16 816a l.02(3) C16 H16b 0.92(3) C16 H16c 0.96(3) C17 H17a 0.9l(2) C17 Hl7b l.03(3) C17 H170 0.99(2) C18 818a 1.01(2) C18 H18b l.06(2) C19 819a 1.11(2) C19 H19b 0.99(2) C20 H20a 1.01(3) C20 HZOb 1.04(2) C20 820c 0.96(3) Numbers in parentheses are estimated standard deviations 111 the least significant digits. 281 Table of Torsion Angles in Degrees for a-mesitylvalerophenone Atom 1 Atom 2 Atom 3 Atom 4 Angle C6 C1 C2 C3 -0.90 0.32) C2 C1 C6 C5 0.21 0.30) C2 C1 C6 C7 -177.28 0.19) C1 C2 C3 C4 0.53 0.35) C2 C3 C4 C5 0.53 0.37) C3 C4 C5 C6 -1.23 0.36) C4 C5 C6 Cl 0.85 0.32) C4 C5 C6 C7 178.47 0.20) C1 C6 C7 01 162.30 0.20) 01 ,C6 07 C8 -14.45 0.28) C5 C6 C7 01 -15.20 0.29) C5 C6 C7 C8 168.05 0.18) 01 C7 C8 C9 128.94 0.19) 01 C7 C8 C18 -0.86 0.26) C6 C7 C8 C9 -54.32 0.24) C6 C7 C8 C18 175.88 0.17) C7 C8 C9 C10 -51.69 0.23) C7 C8 C9 C14 131.10 0.17) C18 C8 C9 C10 76.52 0.22) C18 C8 C9 C14 -100.69 0.20) C7 C8 C18 C19 -169.38 0.17) C9 C8 C18 C19 60.00 0.23) C8 C9 C10 C11 -176.15 0.16) C8 C9 C10 C15 4.71 0.27) 282 Table of Torsion Angles (Continued) for a-mesitylvalerophenone Atom 1 Atom 2 Atom 3 Atom 4 Angle 014 09 010 011 1.08 ( C14 C9 C10 C15 -178.06 ( C8 C9 C14 C13 177.01 ( C8 C9 C14 C17 -2.45 ( C10 C9 C14 C13 -0.28 ( C10 C9 C14 C17 -179.74 ( C9 C10 C11 C12 -0.94 ( C15 C10 C11 C12 178.25 ( C10 C11 C12 C13 -0.05 ( C10 C11 C12 C16 179.35 ( C11 C12 C13 C14 0.90 ( C16 C12 C13 C14 -178.50 ( C12 C13 C14 C9 -0.74 ( C12 C13 C14 C17 178.76 ( C8 C18 C19 C20 176.52 ( C6 C1 C2 HZ 174.65 ( H1 C1 C2 C3 -177.81 ( H1 C1 C2 H2 -2.26 ( H1 C1 C6 C5 177.14 ( 81 'C1 C6 C7 -0.3S ( C1 C2 C3 H3 179.36 ( H2 C2 C3 C4 -175.02 ( H2 C2 C3 H3 3.81 ( C2 C3 C4 H4 -173.91 ( 0.25) 0.17) 0.15) 0.25) 0.26) 0.16) 0.29) 0.18) 0.29) 0.19) 0.28) 0.18) 0.27) 0.17) 0.19) 1.44) 1.27) 1.93) 1.27) 1.29) 1.65) 1.44) 2.20) 1.65) 283 Table of Torsion Angles (Continued) for a-mesitylvalerophenone Atom 1 H3 C3 H3 C3 C3 C4 H4 C4 H4 C4 H5 C5 HS CS 01 C7 C6 C7 38 C8 H8 C8 C7 C8 C7 C8 C9 C8 C9 - C8 H8 C8 H8 C8 H8 C8 C9 C10 C15 C10 C9 C10 C9 C10 C9 C10 C11 C10 C4 C4 C5 C5 C5 C6 C6 C8 C8 C9 C9 C18 C18 C18 C18 C18 C18 C18 C11 ~ C11 C15 C15 C15 C15 C5 H4 H5 C6 HS C1 C7 H8 H8 C10 C14 H18a H18b H18a Hle C19 818a H18b Hll Hll H1$a H15b H15c HlSa 175.17 -58.86 177.96 56.31 -177.88 1.31 -158.44 -36.72 80.30 22.40 ( 1.60) ( 2.31) ( 1.47) ( 1.68) ( 2.25) ( 1.37) ( 1.38) ( 0.88) ( 0.89) ( 0.98) ( 1.00) ( 1.19) ( 1.20) ( 1.20) ( 1.20) ( 1.01) ( 1.54) ( 1.55) ( 1.20) ( 1.22) ( 1.54) ( 1.56) ( 1.44) ( 1.56) 284 Table of Torsion Angles (Continued) for a-mesitylvalerophenone Atom 1 Atom 2 Atom 3 Atom 4 Angle C11 C10 C15 Hle 144.12 C11 C10 C15 H15c -98.86 Hll C11 C12 C13 176.81 Hll C11 C12 C16 -3.79 C11 C12 C13 H13 -l75.76 C16 C12 C13 H13 4.84 C11 C12 C16 H16a -70.l3 C11 C12 C16 Hl6b 167.20 C11 C12 C16 8160 56.34 C13 C12 C16 816a 109.25 C13 C12 C16 Hl6b -l3.42 C13 C12 C16 H16c -124.28 813 C13 C14 C9 176.04 813 C13 C14 C17 -4.46 C9 C14 C17 H17a —177.68 C9 C14 C17 Hl7b -56.S3 C9 C14 C17 H17c 61.75 C13 C14 C17 817a 2.84 C13 C14 C17 Hl7b 124.00 C13 C14 C17 H17c -117.73 C8 C18 C19 819a 59.85 C8 C18 C19 Hl9b -60.85 H18a C18 C19 C20 -61.51 818a C18 C19 H198 -l78.l7 1.54) 1.44) 1.24) 1.27) 1.16) 1.19) 1.55) 1.70) 2.21) 1.95) 1.71) 2.20) 1.11) 1.13) 1.47) 1.40) 1.55) 1.49) 1.39) 1.54) 1.08) 1.32) 1.09) 1.51) 285 Table of Torsion Angles (Continued) for a-mesitylvalerophenone Atom 1 Atom 2 Atom 3 Atom 4 Angle H18a C18 C19 Hl9b 61.12 ( 1.70) H18b C18 C19 C20 59.30 ( 1.12) H18b C18 C19 8198 -57 36 ( 1.53) H18b C18 C19 H19b -178.06 ( 1.70) C18 C19 C20 820a -l77.52 ( 1.63) C18 C19 C20 H20b -65.83 ( 1.68) C18 C19 C20 H200 65.91 ( 1.93) H19a C19 C20 H20a -61.50 ( 2.04) 8198 C19 C20 H20b 50.19 ( 2.08) 819a C19 C20 8200 -178.07 ( 2.27) Hl9b C19 C20 820a 61.66 ( 2.17) Hl9b C19 C20 HZOb 173.35 ( 2.19) Hl9b C19 C20 H200 -54.91 ( 2.40) Numbers in parentheses are estimated standard deviations in the least significant digits. Table 68. X-Ray Crystallographic Parameters for d-Mesityl-2,4,6-Trimethyl- acetophenone 14 Table of Bond Angles (in Degrees) for 1,2-Dimesitylethanone Atoml Atom2 Atom3 Angle C2 C1 C6 118.9(2) C2 C1 C15 119.6(3) C6 C1 C15 121.5(2) C1 C2 C3 122.2(3) C2 C3 C4 117.9(3) C2 C3 C16 121.1(3) C4 C3 C16 121.0(3) C3 C4 C5 122.0(3) C4 C5 C6 119.0(3) C4 C5 C17 119.6(3) C6 C5 C17 121.4(2) C1 C6 C5 119.9(2) C1 C6 C7 119.7(2) C5 C6 C7 120.4(2) 01 C7 C6 121.5(2) 01 C7 C8 122.1(2) C6 C7 C8 116.4(2) C7 C8 C9 115.4(2) C8 C9 C10 120.5(2) C8 C9 C14 120.2(2) C10 C9 C14 119.3(2) C9 C10 C11 118.9(3) C9 C10 C18 121.9(2) C11 C10 C18 119.1(3) C10 C11 C12 122.6(3) C11 C12 C13 117.4(3) C11 C12 C19 121.8(3) C13 C12 C19 120.9(3) C12 C13 C14 122.1(3) C9 C14 C13 119.6(3) C9 C14 C20 121.4(2) C13 C14 C20 119.0(2) 287 Table of Bond Angles (Continued) for 1,2-Dimesity1ethanone Atoml Atom2 Atom3 Angle C1 C2 H2 119.0 C3 C2 82 118.9 C3 C4 84 118.9 C5 C4 84 119.1 C7 C8 88a 108.2 C7 C8 88b 107.7 C9 C8 88a 108.5 C9 C8 88b 107.4 88a C8 88b 109.5 C10 C11 811 118.8 C12 C11 811 118.6 C12 C13 813 118.6 C14 C13 813 119.3 C1 C15 8158 109.8 C1 C15 Hle 109.0 C1 C15 H150 109.5 C1 C15 815d 109.7 C1 C15 815e 109.7 C1 C15 Hle 109.0 815a C15 Hle 109.5 815a C15 8150 109.5 815a C15 815d 140.5 815a C15 HlSe 57.0 815a C15 Hle 55.3 Hle C15 8150 109.5 815b C15 815d 55.2 Hle C15 HlSe 141.2 815b C15 Hle 57.4 8150 C15 815d 57.1 8150 C15 HlSe 55.5 8150 C15 Hle 141.4 815d C15 HlSe 109.5 815d C15 Hle 109.5 HlSe C15 815f 109.5 C3 C16 816a 109.8 C3 C16 Hl6b 109.6 C3 C16 8160 109.0 C3 C16 816d 109.7 C3 C16 Hl6e 109.2 C3 C16 816f 109.5 816a C16 Hl6b 109.5 816a C16 8160 109 5 8168 C16 816d 140.4 8168 C16 816e 57.6 8168 C16 Hl6f 54.7 Hl6b C16 8160 109.5 Hl6b C15 ’816d 54.6 Hl6b C16 8168 141.2 816b C16 Hl6f 57.9 288 Table of Bond Angles (Continued) for 1.2—Dimesityleth8none Atoml AtomZ Atom3 Angle 8160 C16 816d 57.7 8160 C16 Hl6e 55.0 8160 C16 816f 141.5 816d C16 Hl6e 109.5 816d C16 Hl6f 109.5 Hl6e C16 Hl6f 109.5 C5 C17 817a 109.6 C5 C17 Hl7b 109.3 C5 C17 8170 109.5 8178 C17 Hl7b 109.5 8178 C17 8170 109.5 Hl7b C17 8170 109.5 C10 C18 818a 109.9 C10 C18 818b 109.4 C10 C18 8180 109.1 8188 C18 818b 109.5 818a C18 8180 109.5 818b C18 8180 109.5 C12 C19 8198 109.8 C12 C19 Hl9b 109.3 C12 C19 8190 109.4 C12 C19 819d 110.2 C12 C19 819e 109.1 C12 C19 819f 109.1 8198 C19 Hl9b 109.5 8198 C19 8190 109.5 8198 C19 819d 140.0 8198 C19 819e 56.2 8198 C19 819f 55.9 Hl9b C19 8190 109.5 Hl9b C19 819d 56.0 Hl9b C19 819e 141.6 Hl9b C19 Hl9f 56.7 8190 C19 819d 56.1 8190 C19 819e 56.6 8190 C19 819f 141.5 819d C19 819e 109.5 819d C19 819f 109.5 819e C19 819f 109.5 C14 C20 8208 109.2 C14 C20 820b 109.8 C14 C20 8200 109.4 8208 C20 820b 109.5 8208 C20 8200 109.5 820b C20 8200 109.5 Numbers in parentheses are estimated standard deviations in the least significant digits. 289 Table of Bond Distances (in Angstroms) for 1.2-Dimesity1eth8none 01 C7 1.200(3) C1 C2 1.391(4) C1 C6 1.393(4) C1 C15 1.509(4) C2 C3 1.381(4) C3 C4 1.381(4) C3 C16 1.512(4) C4 C5 1.388(4) C5 C6 1.401(4) C5 C17 1.514(4) C6 C7 1.503(4) C7 C8 1.515(4) C8 C9 1.518(4) C9 C10 1.399(4) C9 C14 1.390(4) C10 C11 1.393(4) C10 C18 1.511(4) C11 C12 1.375(4) C12 C13 1.382(4) C12 C19 1.512(4) C13 C14 1.390(4) 1 1(4) 290 Table of Bond Distances (Continued) for 1,2-Dimesity1ethanone Atoml Atom2 Distance C2 82 0.95 C4 84 0.95 C8 888 0.95 C8 88b 0.95 C11 811 0.95 C13 813 0.95 C15 8158 0.95 C15 Hle 0.95 C15 8150 0.95 C15 815d 0.95 C15 815e 0.95 C15 Hle 0.95 C16 8168 0.95 C16 816b 0.95 C16 8160 0.95 C16 816d 0.95 C16 Hl6e 0.95 C16 Hl6f 0.95 C17 8178 0.95 C17 Hl7b 0.95 C17 8170 0.95 C18 8188 0.95 C18 818b 0.95 C18 8180 0.95 C19 8198 0.95 C19 Hl9b 0.95 C19 8190 0.95 C19 819d 0.95 C19 819e 0.95 C19 Hl9f 0.95 C20 8208 0.95 C20 820b 0.95 C20 8200 0.95 Numbers in parentheses are estimated standard deviations in the least significant digits. 291 Table 69. X-Ray Crystallographic Parameters for q-Mesityl-ot-Phenylaceto- phenone 8 Table of Bond Angles (in Degrees) for 2-Hesityl-1,2-dipheny1ethanone Atoml Atom2 Atom3 Angle C2 C1 C6 120.4(4) C1 C2 C3 120.1(6) C2 C3 C4 120.3(5) C3 C4 C5 120.6(4) C4 C5 C6 119.7(6) C1 C6 C5 119.0(4) C1 C6 C7 122.5(4) C5 C6 C7 118.6(5) 01 C7 C6 120.2(4) 01 C7 C8 121.4(4) C6 C7 C8 118.3(5) C7 C8 C9 114.4(4) C7 C8 C15 117.1(4) C9 C8 C15 111.5(3) C8 C9 C10 120.6(4) C8 C9 C14 121.4(4) C10 C9 C14 117.9(4) C9 C10 C11 121.2(5) C10 C11 C12 120.3(5) C11 C12 C13 119.2(5) C12 C13 C14 121.2(5) C9 C14 C13 120.1(5) C8 C15 C16 123.6(5) C8 C15 C20 117.5(4) C16 C15 C20 118.9(5) C15 C16 C17 119.4(5) C15 C16 C21 123.0(5) C17 C16 C21 117.5(5) C16 C17 C18 122.3(5) C17 C18 C19 118.3(6) C17 C18 C22 121.5(5) C19 C18 C22 120.2(6) C18 C19 C20 121.2(5) C15 C20 C19 119.9(5) C15 C20 C23 121.5(5) C19 C20 C23 118.7(5) 292 Table of Bond Angles (Continued) for Z-Mesityl-l,Z-diphenylethanone Atoml Atom2 Atom3 Angle C2 C1 81 120.3 C6 C1 81 119.3 C1 C2 82 120.1 C3 C2 82 119.9 C2 C3 83 119.8 C4 C3 83 119.8 C3 C4 84 119.5 C5 C4 84 119.9 C4 C5 85 120.7 C6 C5 85 119.6 C7 C8 88 100.9 C9 C8 88 106.9 C15 C8 88 104.4 C9 C10 810 118.9 C11 C10 810 119.9 C10 C11 811 120.2 C12 C11 811 119.5 C11 C12 812 120.1 C13 C12 812 120.7 C12 C13 813 119.1 C14 C13 813 119.7 C9 C14 814 119.0 C13 C14 814 120.8 C16 C17 817 119.5 C18 C17 817 118.2 C18 C19 819 119.4 C20 C19 819 119.3 C16 C21 8218 109 6 C16 C21 821b 108.5 C16 C21 8210 110.3 C16 C21 821d 109.4 C16 C21 821e 110.4 C16 C21 821f 108.6 8218 C21 821b 109.5 8218 C21 8210 109.5 8218 C21 821d 141.1 8218 C21 821e 55.7 8218 C21 821f 56.8 821b C21 8210 109.5 821b C21 821d 56.8 821b C21 821e 141.1 821b C21 821f 55.7 8210 C21 821d 55.7 8210 C21 821e 56.8 8210 C21 821f 141.1 821d C21 8210 109.5 821d C21 821f 109.5 821e C21 821f 109.5 C18 C22 8228 110.6 293 Table of Bond Angles (Continued) for 2-Mesityl-1,2-dipheny1ethanone Atoml Atom2 Atom3 Angle C18 C22 822b 108.9 C18 C22 8220 108.9 C18 C22 822d 108.3 C18 C22 822e 110.0 C18 C22 822E 110.1 8228 C22 822b 109.5 8228 C22 8220 109.5 8228 C22 822d 141.0 8228 C22 822e 57.8 8228 C22 822i 54.7 822b C22 8220 109.5 822b C22 822d 54.7 822b C22 822e 141.0 822b C22 822E 57.8 8220 C22 822d 57.8 8220 C22 822e 54.7 8220 C22 822E 141.0 822d C22 822e 109.5 822d C22 822f 109.5 822e C22 822f 109.5 C20 C23 8238 109.9 C20 C23 823b 109.6 C20 C23 8230 108.9 8238 C23 823b 109.5 8238. C23 8230 109. 5 823b C23 8230 109. 5 Numbers in parentheses are estimated standard deviations in the least significant digits. Table of Bond Distances (in Angstroms) for Z-Mesityl-l,2-dipheny1ethanone Atoml Atom2 Distance 01 C7 1.231(7) C1 C2 1.381(6) C1 C6 1.389(8) C2 C3 1.354(7) C3 C4 1.375(9) C4 C5 1.376(7) C5 C6 1.386(6) C6 C7 1.506(6) C7 C8 1.514(6) C8 C9 1.521(6) C8 C15 1.528(7) C9 C10 1.386(7) C9 C14 1.380(6) C10 C11 1.379(6) C11 C12 1.367(8) C12 C13 1.360(8) C13 C14 1.390(6) C15 C16 1.393(7) C15 C20 1.398(7) C16 C17 1.382(9) C16 C21 1.522(9) C17 C18 1.366(9) C18 C19 1.381(8) C18 C22 1.512(10) C19 C20 1.384(8) C20 C23 1.499(7) 295 Table of Bond Distances (Continued) for Z-Hesityl-l,2-dipheny1ethanone Atoml Atom2 Distance C1 81 0.95 C2 82 0.95 C3 83 0.95 C4 84 0.95 C5 85 0.95 C8 88 0.95 C10 810 0.95 C11 811 0.95 C12 812 0.95 C13 813 0.95 C14 814 0.95 C17 817 0.95 C19 819 0.95 C21 8218 0.95 C21 821b 0.95 C21 8210 0.95 C21 821d 0.95 C21 821e 0.95 C21 821f 0.95 C22 8228 0.95 C22 822b 0.95 C22 8220 0.95 C22 822d 0.95 C22 822e 0.95 C22 822E 0.95 C23 8238 0.95 C23 823b 0.95 C23 8230 0.95 Numbers in parentheses are estimated standard deviations in the least significant digits. 296 Table of Torsion Angles in Degrees for Z-Mesityl-l,2—dipheny1ethanone Atom 1 Atom 2 Atom 3 Atom 4 Angle C9 C8 C15 C20 81.24 ( 0.49) C8 C9 C10 C11 173.84 ( 0.48) C14 C9 C10 C11 -3.26 ( 0.77) C8 C9 C14 C13 -175.05 ( 0.47) C10 C9 C14 C13 2.02 ( 0.75) C9 C10 C11 C12 2.47 ( 0.86) C10 C11 C12 C13 -0.35 ( 0.88) C11 C12 C13 C14 -0.87 ( 0.86) C12 C13 C14 C9 0.02 ( 1.27) C8 C15 C16 C17 175.03 ( 0.41) C8 C15 C16 C21 -3.76 ( 0.68) C20 C15 C16 C17 -0.74 ( 0.64) C20 C15 C16 C21 -179.52 ( 0.43) C8 C15 C20 C19 -175.18 ( 0.37) C8 C15 C20 C23 4.54 ( 0.56) C16 C15 C20 C19 0.85 ( 0.60) C16 C15 C20 C23 -179.44 ( 0.39) C15 C16 C17 C18 -0.43 ( 0.73) C21 C16- C17 C18 178.42 ( 0.46) C16 C17 C18 C19 1.47 ( 0.73) C16 C17 C18 C22 -178.05 ( 0.48) C17 C18 C19 C20 -1.35 ( 0.68) C22 C18 C19 C20 178.18 ( 0.44) C18 C19 C20 C15 0.21 ( 0.65) C18 C19 C20 C23 -179.52 ( 0.40) ""I‘ A "‘ 297 Table of Torsion Angles in Degrees(0ontinued) Z-Mesityl-l,Z-diphenylethanone Atom 1 Atom 2 Atom 3 Atom 4 Angle C6 C1 C2 C3 -1.41 0.86) C2 C1 C6 C5 2.35 0.82) C2 C1 C6 C7 -178.23 0.51) C1 C2 C3 C4 -0.24 0.85) C2 C3 C4 C5 0.92 0.84) C3 C4 C5 C6 0.06 0.77) C4 C5 C6 C1 -l.66 0.80) C4 C5 C6 C7 178.89 0.49) C1 C6 C7 01 -171.90 0.53) C1 C6 C7 C8 3.44 0.76) C5 C6 C7 01 7.53 0.77) C5 C6 C7 C8 -177.13 0.47) 01 C7 C8 C9 5.87 0.72) 01 C7 C8 C15 -127.31 0.51) C6 C7 C8 C9 -l69.41 0.44) C6 C7 C8 C15 57.41 0.60) C7 C8 C9 C10 87.40 0.58) C7 C8 C9 C14 -95.60 0.56) C15 C8 C9 C10 -136.82 0.48) C15 C8 C9 C14 40.18 0.62) C7 C8 C15 C16 39.87 0.59) C7 C8 C15 C20 -144.30 0.41) C9 C8 C15 C16 -94.58 0.51) Numbers in parentheses are estimated standard deviations in the least significant digits. 298 Table of Torsion Angles in Degrees for 1,2-Dimesitylethanone Atom 1 Atom 2 Atom 3 Atom 4 Angle C6 C1 C2 C3 0.90 C15 C1 C2 C3 -l77.54 C2 C1 C6 C5 -2.56 C2 C1 C6 C7 178.03 C15 C1 C6 C5 175.85 C15 C1 C6 C7 -3.56 C1 C2 C3 C4 1.17 C1 C2 C3 C16 179.85 C2 C3 C4 C5 -1.62 C16 C3 C4 C5 179.69 C3 C4 C5 C6 0.00 C3 C4 C5 C17 178.34 C4 C5 C6 Cl 2.13 C4 C5 C6 C7 -178.46 C17 C5 C6 C1 -176.19 C17 C5 C6 C7 3.22 C1 C6 C7 01 78.99 C1 C6 C7 C8 -99.95 C5 C6 C7 01 -100.42 C5 C6 C7 C8 80.64 01 C7 C8 C9 -3.06 C6 C7 C8 C9 175.88 C7 C8 C9 C10 -96.44 C7 C8 C9 C14 81.65 C8 C9 C10 C11 177.45 C8 C9 C10 C18 -3.38 C14 C9 C10 C11 -0.64 C14 C9 C10 C18 178.52 C8 C9 C14 C13 -177.17 C8 C9 C14 C20 2.59 C10 C9 C14 C13 0.94 C10 C9 C14 C20 -179.31 C9 C10 C11 C12 -0.75 C18 C10 C11 C12 -179.94 C10 C11 C12 C13 1.78 C10 C11 C12 C19 -178.48 C11 C12 C13 C14 -1.47 C19 C12 C13 C14 178.79 C12 C13 C14 C9 0.14 C12 C13 C14 C20 —179.62 AAAAAAAAAAAAAAA‘AAAAAAAAAAAAAAAAAAAAAAAA eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee NuNU’NU’U’WNWWNNWWNNNNW‘A’WNwWNNwNfiNbNWWNNWNW OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv 4. a. 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