SYNTHETIC APPROACHES TO 1,2- .CYCLOOCTATRIENEDIONE Thesis for the Degree of Ph. D. MICHIGAN SFATE UNIVERSITY THOMAS R. KOWAR 1972 This is to certify that the thesis entitled Synthetic Approaches to 1,2-Cyclooctatr1enedione presented by Thomas R. Kowar has been accepted towards fulfillment of the requirements for Ph.D. degree in Chemigtzy Mfimmmmuxi Date September 11, 1972 0-76” [illlll'lll‘rlll‘ [(l'lf‘ [{i.||||-[ .[lf'll ABSTRACT SYNTHETIC APPROACHES TO 1,2-CYCLOOCTATRIENEDIONE BY Thomas R. Kowar Synthetic approaches to 1,2-cyclooctatrienedione g and its valence tautomer, bicyclo[4.2.0]-2,4-octadiene- 7,8-dione ég, were investigated.‘ Treatment of 7,8-bis(trimethylsiloxy)-cis-bicyclo- [4.2.0]-3,7-octadiene Sz with pyridinium hydrobromide perbromide afforded 3,4-dibromobicyclo[4.2.0]-6-octene-7,8- dione Ql which was converted to benzocyclobutadienoquinone QQ by the action of l,5-diazabicyclo[4.3.0]-S-nonene. Bromination of éz with N-bromosuccinimide afforded QQ directly. The boron trifluoride etherate catalyzed oxidation of 5,6-epoxycyclooctene with dimethylsulfoxide afforded 2- hydroxy—S-cyclooctenone ZQ which was subsequently oxidized to S-cyclooctene-l,2-dione 93. Bromination of Q2 with cupric bromide gave trans-3,8-dibromo-5-cyclooctene-1,Z-dione SS. Attempts to form g by the dehydrobromination of SS were unsuccessful but the use of hexamethylphosphoric triamide as the base provided 3-bromo-2-hydroxy-Z,5,7-cyclooctatrienone 2 Thomas R. Kowar SS. Bromination of SS with N-bromosuccinimide afforded 3,7- dibromo-3,5-cyclooctadiene-1,2-dione SSS. Treatment of SSS with triethylamine resulted in the formation of SS. The reaction of SS with o-phenylenediamine afforded 2,7- dibromo-10,ll-benzo-9,12-diazabicyclo[6.4.0]-4,8,10,12- dodecatetraene SS which was subsequently dehydrobrominated with l,5-diazabicyc10[4.3.0]-S-none to form 10,11-benzo-9,12- diazabicyclo[6.4.0]-2,4,6,8,10,12-dodecahexaene SS. The Spectroscopic properties of SS, the quinoxaline derivative of S, indicated a nonplanar geometry for the eight membered ring. Attempts to synthesize the bis ethylene ketal of SS from SS or from the bis ethylene ketal of SS, 1,2-bis-(spiro-1',3'- dioxolane)-5-cyclooctene SS,2 were not successful. The reaction of SS and p-anisaldehyde provided 3,8-di- (p-methoxybenzilidene)-S-cyclooctene-1,2-dione SS. An attempt to isomerize SS to the dibenzyl derivative of S using palladium failed. Birch reduction of SS afforded 3,8-di(p- methoxybenzyl)-5-cyclooctene-l,2-dione SSS. References l. P. Yates, E. G. Lewars, and P. H. McCabe, Can. J. Chem., SS, 788 (1970). 2. P. Yates and B. G. Lewars, Chem. Commun., 1537 (1971). SYNTHETIC APPROACHES TO 1,2-CYCLOOCTATRIENEDIONE BY . “" Thomas Ri Kowar A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1972 To Who My Mother and Father Have Given Me So Much ii ACKNOWLEDGMENTS The author wishes to thank Dr. Eugene LeGoff for his enthusiasm, encouragement, and patience during the course of this work. Gratitude is also expressed to the Department of Chemistry at Michigan State University for providing teaching assistantships during this time. Financial support provided by the National Science Foundation, the National Institutes of Health, and the Petroleum Research Fund is gratefully acknowledged. Special thanks are extended to my fellow graduate students who have made the last five years interesting and, at times, enjoyable. iii TABLE OF CONTENTS Page INTRODUCTION. . . . . . . . . . . . . . . . . . . . 1 Previous Approaches to 1,2-cycloocta- trienedione. . . . . . . . . . . . . . . . . . 12 RESULTS AND DISCUSSION. . . . . . . . . . . . . . . 17 Suggestions for Future Study . . . . . . . . . 7O EXPERIMENTAL. . . . . . . . . . . . . . . . . . . . 71 General Procedures . . . . . . . . . . . . . . 71 3, 4- -Dibromobicyclo[4. 2. O]- -6- -octene- 7, 8- dione (Dione SS) . . . . . . . . 72 Reaction of 3,4- dibromobicyclo[4. 2. 0]- -6- octene-7,8-dione SS and 1, 5- diazabicyclo- [4.3.0]-5-nonene enzocyclobutadieno- quinone SS). . . . . . . . . . . . 73 Reaction of 7,8-bis(trimethylsiloxyycis- bicyclo[4.2.0]-3,7-octadiene and N-bromo- succinimide (Benzocyclobutadienquinone SS) . . 74 7, 8- -Bis(trimethylsiloxy)-truns -bicyclo[4. 2. 0]- 3, 7- octadiene (Bis ether SS) . . . . . . . 75 Z-Hydroxy-S-cyclooctenone (Ketone SS). . . . . 76 5-Cyclooctene-l,2-dione (Diketone SS). . . . . 77 10,11-Benzo-9, lZ-diazabicyclo[6. 4. 0]-4, 8,10, 12- dodecatetraene (Quinoxaline SS) . . . . 78 3,8-Di(p-methoxybenzilidene)-S-cyclooctene- 1,2-dione (Dione fig) 0 o o o o o o o o o o o o 79 trans-3,8-Dibromo-5-cyclooctene-1,2-dione (Dibromide SS) . . . . . . . . . . . . . . . . 80 iv ‘Ill. llli’ *[I1f 'JII-llltlliyi (It’ll. TABLE OF CONTENTS (Continued) Page 2, 7-Dibromo-10,11-benzo-9,12-diazabicyclo- [6. 4. 0]- 4, 8, 10, 12- dodecatetraene (Quinoxaline 88) . . . . . . . . . . . . . 81 10,11-Benzo-9,12-diazabicyclo[6.4.0]-2,4,6, 8,10,12-dodeahexaene (Quinoxaline 88). . . . . 82 3—Bromo-2-hydroxy-2,S,7-cyclooctatrienone (Ketone 88). . . . . . . . . . . . . . . . . . 83 1,2-Bis(spiro-1',2'-dioxolane)-S-cyclooctene (Bis ethylene ketal 88). . . . . . . . . . . . 84 l-(2'-bromoethoxy)-2-(spiro-1',3'-dioxolane)- 5-bromo-9-oxabicyclo[4.2.1]nonane (Ketal 88 or 888). . . . . . . . . . . . . . . . . . . . 85 3, 8- -Di(p- methoxybenzy1)- -S- cyclooctene- 1, 2- dione (Dione 888). . . . . . . . . . . . . . 86 3,7-Dibromo-3,S-cyclooctadiene-l,Z-dione (Dione 888). . . . . . . . . . . . . . . . . . 87 Reaction of 3,7-dibromo-3,S-cyclooctadiene- 1,2-dione 1 8 and triethylamine (Benzocyclo- butadienoquinone 88) . . . . . . . . . . . . . 88 BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . 89 APPENDIX. . . . . . . . . . . . . . . . . . . . . . 101 l[({|1.[!\ll ‘11 II {‘I' ll'l‘ll' ll [‘1 III TABLE II III IV VI VII VIII IX LIST OF TABLES Summary of attempts to dehydrobrominate Synthetic approaches to bis ketal 88. Summary of couplings and coupling constants of the bromination product of 88 . . . . . . . . . . . . . . Mass Spectrum of 3,4-Dibromobicyclo- [4.2.0]-6-octene-7,8-dione. . . . Mass Spectrum of S-Cyclooctene-l,2-dione. Mass Spectrum of trans-3,8-dibromo-S- cyclooctene-l,2-dione . . . . . . . Mass Spectrum of 10,11-benzo-9,12- diazabicyclo[6. 4. 0]-2, 4, 6, 8, 10,12- dodecahexaene . . . . . . Mass Spectrum of 3-bromo-2-hydroxy- 2,5,7-cyclooctatrienone . . . Mass Spectrum of 3,7-dibromo-3,S- cyclooctadiene-l,Z-dione. . vi Page 42 48 64 101 102 103 104 105 106 [[{IIII' {[(Il.lllll1lLl[[f|ll‘[[!1.{l[[/| FIGURE 10 11 12 13 LIST OF FIGURES Infrared spectrum of 3,4-dibromobicyclo [4.2.0]-6-octene-7,8-dione 88 (CHC13). Infrared spectrum of 5-cyclooctene-1,2- dione 88 (CHClS) . . . . . . . . . . Infrared spectrum of trans-3,8-dibromo- S-cyclooctene-1,2-dione 88 (CHClS) Infrared Spectrum of 10,1l-benzo-9,12- diazabicyclo[6.4.0]-2,4,6,8,10,12- dodecahexaene 88 (CHC13) . . . . . Infrared spectrum of 3-bromo-2-hydroxy- 2,5,7-cycloctatrienone 88 (CHClS). Infrared spectrum of 3,7—dibromo-3,5- cyclooctadiene-l,2-dione 888 (CHCls) . Nmr spectrum of 3, 4- -dibromobicyclo[4. 2. 0]- 6- -octene- 7, 8- dione 88 (CDC13). Nmr spectrum of S-cyclooctene-1,2-dione 88 (CDC13) . . . . . . . . . . . . . Nmr spectrum of trans-3,8-dibromo-5- cyclooctene-1,2-dione 88 (CDC13) Nmr spectrum of 10,11-benzo-9,12-diaza- bicyclo[6. 4. 0L -2 ,4 6, 8, 10, 12- dodeca- hexaene 88 (CDC13) . . . . . . . . Nmr spectrum of 3-bromo-2-hydroxy-2,5,7- cyclooctatrienone 88 (CDC13) Nmr spectrum of 3-bromo-2-hydroxy-2,S,7- cyclooctatrienone 88 (DMSO-d6) . Nmr spectrum of 3,7-dibromo-3,5-cyclo- octadiene-1,2-dione 888 (CDC13). vii Page 107 108 109 110 111 112 113 113 114 114 115 115 116 SCHEME II III IV VI VII VIII IX XI XII LIST OF SCHEMES Proposed synthetic route to bicyclo [4.2.0]-2,4-octadiene-7,8-dione 88. Pr0posed synthetic route to bicyclo [4.2.0]-2,4-octadiene-7,8-dione 88. Proposed synthetic route to 1,2-cyclo- octatrienedione 8 . . . . . . . . . Proposed synthetic route to 1,2-cyclo- octatrienedione 8 . . . . . . . Proposed synthetic route to S-cyclo- octene-l,2-dione 88 . . . . . . . Synthetic route to S-cyclooctene-l,2- dione 88. . . . . . . . . . . . . . . Proposed synthetic route to 1,2-cyclo- octatrienedione 8 . . . . . . . . . . . Proposed synthetic route to 3,8-dibromo- 1,2-bis(spiro-l',3'-dioxolane)-S- cyclooctene 95. . . . . . . . . Proposed synthetic route to 1,2—cyclo- octatrienedione 8 . . . Proposed synthetic route to 3, 8- -di(p- methoxybenzyl)- -1, 2- -cyclooctatrienedione 888. Pr0posed synthetic route to 3,8-di(p- methoxybenzyl)-1,2-cyclooctatrienedione 108 . . . . . . . . . . . Proposed synthetic route to 3, 8- dihydroxy- 1, 2- cyclooctatrienedione 888.. . viii Page 18 20 26 27 28 30 47 49 52 54 57 59 I'll!!!“ {{(‘II‘ [1 .[fl‘ .A {{ llI’I‘!‘ ('1‘ LIST OF SCHEMES (Continued) SCHEME Page XIII Proposed synthetic route to 6-cyclo- octene-l,2,3,4-tetraone 888. . . . . . . . 60 XIV Proposed synthetic route to 6-cyclo- octene-l,2,3,4-tetraone 888. . . . . . . . 61 SYNTHETIC APPROACHES TO 1,2-CYCLOOCTATRIENEDIONE INTRODUCTION During the latter half of the nineteenth century the stability of benzene relative to acyclic olefins presented organic chemists with a formidable problem. In 1872 Kekule1 concluded that benzene had a 1,3,5- cyclohexatriene structure in which the n-electrons are delocalized. Thus electron delocalization became associated with enhanced stability. This idea was developed quantitatively with the advent of molecular orbital theory by Hiickel2 in 1931. The molecular orbital method places the n-electrons of benzene into molecular orbitals which are common to all of the carbon atoms. Hfickel recognized that when the bonding molecular orbitals were completely filled, stability enhancement resulted in a manner analogous to that encountered with the rare gas atomic orbital configurations. Thus Hfickel was able to predict that compounds whose bonding molecular orbitals were completely filled would possess the enhanced stability exhibited by benzene. The conditions for this aromatic stabilization are contained in the Hfickel rule2 which states that "amongst fully conjugated, planar, monocyclic polyolefins only those possessing (4n + 2) n-electrons, where n is an integer, will have special aromatic stability.11 The prOphesy of Hfickel's rule has prompted organic chemists to synthesize a wealth of interesting compounds in order to test the validity of the concept of aromaticity. There is, perhaps, no other theory in organic chemistry which has been more critically examined than that of aromaticity. Interestingly, the aromatic theory has also proven to be one of the most durable concepts of organic chemistry. The (4n + 2) rule was originally intended to be valid only for symmetrical, monocyclic systems but has since been successfully applied to many polycyclic and heterocyclic compounds. Molecular orbital theory allows for the calculation of the delocalization energy (DE), a measure of the extent to which a particular system is stabilized relative to a model system containing the same number of localized n-electrons. Hfickel molecular orbital (HMO) calculations of delocalization energies are based on certain inaccurate assumptions and thus must be interpreted with caution. More sophisticated types of molecular orbital calculations have been developed to circumvent these problems. During the following discussion delocalization energies will be used only in a qualitative sense. During the past twenty-five years several types of organic ions containing (4n + 2) n-electrons have been synthesized and have been shown to be aromatic. Breslow3 described the synthesis of triphenylcyclo- propenium tetrafluoroborate in 1957. This salt was found to be stable and is considered to be aromatic. Recently the parent ion has been prepared.“ The aromatic character of the cyclopropenium ion was confirmed by it's nuclear magnetic resonance (nmr) spectrum which exhibits a singlet absorption at 6 11.1 relative to tetramethylsilane (TMS). When this absorption position is corrected5 for strain, charge, and alteration of ring current, it's value is approximated to occur in the aromatic region of the nmr Spectrum. The DB of the cyclopropenium ion is calculated to be 2.00 8.5 The first deliberate synthesis of the cycloheptatrienyl (trOpylium) cation was reported by Doering and Knox in 1954.7 Comparison of the infrared and raman Spectra of tropylium bromide confirm that the carbonium ion is symmetrical with the positive charge evenly distributed over all seven carbons.7’° The nmr spectrum of the trOpylium ion consists of a singlet absorption at 6 9.2 relative to TMS.9 This absorption position is indicative of an aromatic species when it is corrected for charge. HMO calculations indicate that the tropylium ion Should have a DB of 2.99 8.6 The cyclOpropenone system does not meet the conditions for aromaticity as required by Hfickel's rule, but neverthe- less, is considered to possess aromatic character. Cyclopropenones are expected to be highly strained species due to the incorporation of three Sp; hybridized carbon atoms into a three-membered ring. Breslow, however, in 195910 reported the synthesis of diphenyl- cyclopropenone 8 as a stable, crystalline material. The less strained cycloprOpanone system, first reported by Turro, Hammond, and Leermakers11 in 1965, is quite unstable and undergoes reactions which result in the relief of ring strain. The difference in stability between these two systems must be attributed to the aromatic character conferred to cyclopropenones by resonance forms such as 8' which contain the aromatic cyclopropenium ion moiety. 0 o‘ A <——> A ¢ % ¢ ¢ % ¢ Supplementary evidence for this argument is obtained from the fact that cyclopropenones react readily with strong acids to form hydroxycycloprOpenium salts 8,10b:12 O OH ,A, VAN X- 4; é The infrared carbonyl absorption frequency of 1 diphenylcyclopropenone’"a,13 occurs at 1640 cm' while that of tetramethylcycloprOpanone11 occurs at 1840 cm-1 indicating that the carbonyl group of cyclopropenones possesses considerable single bond character. Dipole moment data also support the importance of the dipolar resonance forms of cyclopropenones. Diphenyl- cyclopropenone has a dipole moment of 5.08 D13 while benzophenone has a dipole moment of only 2.97 D indicating appreciable polarization of the cyclopropenone carbonyl double bond. The DB of the parent cyclopr0penone is calculated to be 1.36 8.1“ The first example of a cycloheptatrienone derivative 5 was recognized in 1945 when Dewar1 proposed the tropone skeleton 8 for the structure of the natural product stepiatic acid 8. Since then many natural products containing the tropone skeleton have been isolated and a large number of synthetic tropones and tropolones have been prepared. By analogy to cyclopropenone, the tropone system may be considered to be aromatic in nature as a resonance form 8 containing the aromatic tropylium ion can be visualized. O O O OH HO O H 84:- 80 801 N The protons of tropone exhibit absorption in the aromatic region of the nmr Spectrum.1 The infrared carbonyl absorption of tropone occurs at 1590 cm'117 which is lower than that of 2,6-cycloheptadienone (1647 cm'l)18 reflecting the single bond character of the carbonyl double bond. TrOpone has a dipole moment of 4.3 D19 which compared to a value of 3.04 D2° for cycloheptanone indicates a small but significant contribution from the dipolar resonance form. Like the cyclOpropenones, tropones react with strong acids to form hydroxytropylium salts. HMO calculations predict tropone to have a DB of 2.55 8.21 Despite the convincing arguments put forth for the aromatic nature of tropones there have recently appeared several papers which provide evidence which defines these compounds as being more polyenoic than aromatic in nature.“’23 Recently 4,9-methano[ll]annulenone 8, a 10 n-electron analog of trOpone, has been synthesized by Grimme, Reisdorff, Junemann, and Vogel.2“ This compound appears to be a polyenone in the ground state based on an analysis of the lOO-MHz nmr spectrum. When 8 was treated with deuteriotrifluoroacetic acid, the aromatic 4-hydroxy- bicyclo[5.4.l]dodecapentaenylium ion 8 was formed. The primary goal of research described in this thesis was the synthesis of 1,2-cyclooctatrienedione 8 which can be considered to be a formal analog of tropone and is a member of a family of cyclic unsaturated a-diketones of type 88. These compounds are expected to be aromatic when m is an odd integer as resonance forms containing (4n + 2) n-electrons such as 88 can be visualized. The only known members of this family at the present time are the cyclobutenediones and the cyclo- hexadiene-l,25diones. Dione 8 is expected to be aromatic or at least to exhibit some aromatic character by virtue of the contribution of the dipolar resonance form 88 which contains the cyclooctatrienium dication moiety. Although the cyclooctatrienium dication has not been observed directly, it has been implicated as an intermediate in the anodic oxidation of cyclooctatetraenezs:26 and is expected to be aromatic in accordance with Hfickel's rule. /\ 2 There are serious objections to dipolar resonance form 88. The charge separation and the electrostatic charge repulsion between the negative charges on the oxygen atoms will increase the energy of 88 and thereby decrease it's importance as a contributor to the overall structure of the molecule. Similar problems are encountered in a consideration of the cyclobutenediones 8827 whose surprising stability has been attributed to the dipolar resonance form 88 which contains the 2 n-electron aromatic cyclobutenium dication moiety. This case is not completely analogous to cyclooctatriene-l,2- dione, however, as there is no increase in ring Strain upon going to the dipolar resonance form and, in addition, cross ring resonance forms 88 and 88 can be visualized. 0 I o ' o' 3 ' R' I! R' R 88 MonOprotonation of 1,2-cycloctatrienedione would reduce the repulsion between the oxygen atoms and would be expected to increase the importance of the aromatic resonance contributor 88. +0-H -0 H”. 9 81 o \ /\ \V Such a species could also exist as the homotropylium ion 88 analogous to the homotropylium ion 88 formed upon protonation of 2,4,6-cyclooctatrienone 88.28 O —_—> @011 6 0H £8 a $8 $8 0 Diprotonation of 1,2-cyclooctatrienedione would further reduce the problem of charge repulsion and, in fact, the resulting dication would be the 1,2-dihydroxycyclo- octatrienium dication. Recent molecular orbital calculations by Gund and Carpino29 indicate that 1,2-cyclooctatrienedione should possess aromatic stabilization. HMO calculations assign a delocalization energy of 3.07 B to the dione 8 while the more refined Streitwieser-Coulson molecular orbital 10 (SCMO) calculations predict a DB of 2.76 B for 8. The SCMO calculations indicate that tropone should have a DB of 2.19 B which is equivalent to a DB to ring atom ratio of 0.31 B when the oxygen atom is neglected. The corresponding ratio for 1,2-cyclooctatrienedione is 0.35 B. The strain resulting from the planar conformation required for aromaticity in 8 is, of course, greater than that required for planarity in the seven-membered ring of tropone. This ring strain should be similar to that resulting from planar cyclooctatetraene which has been estimated2113° to be approximately 27 Kcal/mole. The SCMO DE for 1,2-cyclooctatrienedione is 45.6 Kcal/mole and thus the ring strain is not a prohibitive factor in the potential aromaticity of 8. Chemical evidence also infers that 1,2-cycloocta- trienedione will be a stable, isolable compound. Heptafulvene 88 is the methylene homolog of tropone.31 While trOpone is a distillable liquid, heptafulvene polymerizes at temperatures greater than -80°C. The bis methylene homolog of dione 8, 7,8-dimethylene-l,3,5- cyclooctatriene 88, was reported independently in 1966 by Elix, Sargent, and Sondheimer32 and by Anet and Gregorovich.33 This compound was synthesized from it's immediate precursor at 25°C and was shown to be stable in the absence of oxygen and light. The exocyclic methylene groups of this compound constitute an extremely 11 reactive dienophilic moiety which, in part, accounts for it's high reactivity. The substitution of carbonyl groups for the methylene groups would be expected to decrease such reactivity and by analogy to the difference in stability between heptafulvene and tropone, it would be expected that 1,2-cyclooctatrienedione would be more stable than the corresponding bis methylene cyclooctatriene. 55 9 Q5 § 4 ’\4 Considering the skepticism concerning the aromaticity of trOpones and the demonstration of the polyenoic nature of 8 it might be Optimistic to expect that 1,2-cyclo- octatrienedione would be aromatic. It is, however, an interesting molecule and was deemed a worthy synthetic goal. The protonated forms of the target compound would be more likely candidates as aromatic Species. The preparation of such ions would bear directly on the problems of the aromatic character of homotr0pylium ions and cyclooctatrienium dications. 12 Previous Approaches to 1,Z-cyclooctatrienedione. Although one benzo derivative of 1,2-cyclooctatriene- dione is known, the parent system has eluded previous synthetic attempts. The isomeric 1,4-cyclooctatriene- dione system has received some attention since the arguments presented for the potential aromaticity of the 1,2-dione apply equally well to the 1,4-dione. Cava and Ratts, in 1962, reported that the oxidation of the biphenylenes gé and fig yields the corresponding halodibenzocyclooctatriene-1,4-diones gé and g3 31% respectively. These authors, however, failed to comment on the potential aromaticity of these systems. \\ /’ ‘x \ / X g§X=Br g§X=Br g4 X = C1 gé X = C1 In 1966 McIntyre, Proctor, and Reesa5 attempted the synthesis of benzocycloocta-l,4,6-triene-3,8-dione gz in order to determine the possibility of electron delocalization in such systems. Bromination of benzo- cyclooctene-3,8-dione gg with N-bromosuccinimide (NBS) . failed to give the expected 4,7-dibromobenzocyclooctene- 3,8-dione %g which was to be converted to the desired 13 product by treatment with a suitable base. Instead the isomeric 4,4-dibromobenzocyclooctene-3,8-dione éQ was' formed. a There have been two syntheses of dibenzo[a,e]cyclo- octene-5,6-dione é}. Acyloin condensation of bis aldehyde fig followed by oxidation afforded Bendall and Neumer36 the desired él. 0 0H 0 ' H0 0 , O O —> -> éé [€11 This compound was shown not to be aromatic on the basis of various physical and spectroscopic properties. Such a result is expected due to the annelation effect of the benzene rings. Indeed, dibenzotropones has been shown to to be nonaromatic. 14 Yates, Lewars, and McCabe37 synthesized Q; by an alternate route. Bromination of dibenzocycloocta-l,5- diene éé with N-bromosuccinimide provided 5,11-dibromo- 5,6,11,lZ-tetrahydrodibenzo[a,e]cyclooctene ég. Treatment of éé with dimethylsulfoxide and collidine gave dibenzo[a,e]cyclooctene-5(6H)-one ég which was subsequently oxidized to él by use of selenium dioixde in dioxane. 0 00—51" ~00 o 1% r34. 13% > 0 G '31; Cyclooctatetraene ég undergoes a reversible electro- cyclic ring closure to bicyclo[4.2.0]octa-2,4,7-triene éZ' It is expected that 1,2-cyclooctatrienedione should also be capable of an electrocyclic conversion to bicyclo[4.2.0]octa-2,4-diene-7,8-dione ég. O O - / _\_ / | A / /O T- \L._J : \ M éé a 2 éé H 15 There have been two reported synthetic approaches to the bicyclic form of l,2-cyclooctatrienedione. Pappas, Pappas, and Portnoy38 photolyzed Zémethoxy- 1,4-benzoquinone £2 in the presence of dimethylacetylene %Q with the aim of obtaining bicyclic diketone él. Reduction of %I followed by hydrolysis and then oxidation was expected to lead to g; which is a valence tautomer of 4,S-dimethylcyclooctatriene-1,Z-dione $é. O OH OCH3 3 \ CH3 + I l —> I: 1’ 0 £3 4% 0 /. __2> / /’ 4'5 42% I I E] :12 34> n—o—n—n (N a: V [— These authors, however, were frustrated at the initial step of their synthetic plan as the photolysis product obtained was the isomeric bicyclic diketone $4. 0 CH OCH 3 0 OCH3 3 A L__/ - '29 —-> (:41 o 2.3 4,4 16 Gund and Carpino29 developed a clever synthetic scheme for the synthesis of the bicyclic valence tautomer of dione 2. Cycloaddition of 1,3-cyclohexadiene gé and dichloroketene QQ readily provided bicyclic ketone 51 which was successfully brominated with N-bromosuccinimide. When bicyclic bromoketone 4Q was treated with 1,5-diaza- bicyclo[4.3.0]nona-5-ene (DBN) to effect dehydro- halogenation, the elimination proceeded in an unexpected fashion and gave 3,3-dichlorotricyclo[5.1.0.0]oct-5-ene— Z-one 3% as the product. - . *O B 7° ——> ’ 00/ -1-> ©3241 —'> SCI-16L) 0:116“ @Q 45, . a at u _020 yo CTN RESULTS AND DISCUSSION The primary goal of the research described in this thesis was the synthesis of 1,2-cyclooctatrienedione Q. As mentioned previously 3 should be capable of undergoing an electrocyclic ring closure to bicyclo[4.2.0]-2,4- octadiene-7,8-dione éfi. The reverse reaction is also an allowed process and g and éQ are therefore expected to exist as an equilibrium mixture. Thus the synthesis of 2 can be approached from either of two directions. A number of different types of synthetic approaches to g have been investigated, two of which were directed tOward the preparation of bicyclic dione éfi. The initial approach to ég was based on the capability of cyclobutadiene QQ to enter into cyclo- addition reactions with olefins. Generation of cyclo- butadiene in the presence of dimethylmaleate él affords endb, cis-S,6-dicarbomethoxybicyclo[2.2.0]-2-hexene ég.39 K“ ”H ——> CO2 CH3 éQ . g; COZCH3 17 18 It seemed reasonable therefore that cycloaddition of an appropriately substituted cyclobutene and cyclo- butadiene would provide an endb-tricyclo[4.2.0.02’5]-3- octene éé which could then be transformed into S4 by a photochemical orbital symmetry allowed disrotatory“° cyclobutene ring Opening. The cyclobutane functionalities of §& were then to be converted to the requisite ae diketone moiety of éé as depicted in Scheme I. Scheme I éQ a Y, \ / / / ‘\ --rfir \\ h—J Y' O 1% 1% The first cyclobutene investigated was 1,1-dif1uoro- 2,2-dichloro-S-phenylcyclobutene §§“1 whose geminal dihalogen groups were to serve as potential carbonyl groups. Treatment of $5 with cyclobutadiene generated in situ from its iron tricarbonyl complex in acetone solution according to the method of Pettit39’“2 afforded only the starting cyclobutene upon workup. 19 It seemed possible that the electron withdrawing effect of the geminal dihalogen groups was deactivating the double bond of SS to such an extent that no cyclo- addition occurred. In order to partially counter this effect the cycloaddition of cyclobutadiene and 2,2- dichloro-S-phenylcyclobutenone SS“1 was attempted. In_ this case some reaction had occurred as evidenced by the isolation of a small amount of a brown intractable material in addition to two thirds of the starting material. F U + /Z/ 2C1 6 (D «E9 ¢ \1 / 1 c1 F F éé O + 1—__>I'¢ éQ «Ska / ’0 C1 C1 Apparently cyclobutadiene dimerization occurs much more rapidly than the cyclobutadiene-cyclobutene SS cycloaddition reaction. In the case of cyclobutene SS reaction with cyclobutadiene was Somewhat competitive with the dimerization reaction, but the lack of any evidence for the formation of a derivative of SS suggested that either a cycloaddition was not occurring or that the cycloadduct was unstable under the reaction conditions.‘ Accordingly a different route to SS was sought. 20 The second synthetic approach to SS as outlined in Scheme II utilized 7,8-bis(trimethylsiloxy)bicyc10[4,2,0]- 3,7-octadiene SS, a compound which is easily synthesized from cis-l,2-dicarbomethoxy-4-cyclohexene SS by “3 as the Bloomfield's modified acyloin condensation, starting material. The l,2-bis(trimethylsiloxy)cyclo- butene moiety was to serve as a precursor to the Cyclo- butanedione portion of SS while the double bond was to be converted to the requisite 1,4-butadiene by a bromination- dehydrobromination sequence. Scheme II , OTMS Br / / f ._1 . —-> -> C I V TMS Br L—JR \ L—J§O «'31 £2 éé Wynberg““ has recently demonstrated that bromine reacts with l,2—bis(trimethylsiloxy)cycloalkenes by an addition-elimination mechanism to produce 1,2-cyclo- alkanediones, This method seemed ideal for the conversion of S1 to SS as the bromination of the double bond could be performed simultaneously to the formation of the dione moiety. There would remain then only the dehydro- 21 bromination of 3,4-dibromobicyclo[4.2.0]-7,8-octanedione SS. This step suffered potential difficulties as Gund and Carpino29 have demonstrated that bromoketone SS undergoes a 1,3-dehydrobromination upon treatment with DBN to form SS. It was expected however that different dehydrobromination conditions would induce SS to dehydro- brominate in a normal fashion. Addition of a solution of two equivalents of bromine in chloroform to a solution of SS in chloroform maintained at 0° followed by removal of the solvent under reduced pressure at room temperature afforded a red-brown oil which yielded a small amount of light yellow crystals upon purification. This same product was obtained in greater yield upon treatment of a Solution of SS in tetrahydrofuran maintained at -78° with a solution of pyridinium hydrobromide perbromide"5 in tetrahydrofuran. This crystalline material melted at 161-164° with the evolution of a gas which was acidic to moist pH paper and upon cooling a yellow crystalline material of melting point 127-130° was obtained. The ir spectrum of this thermal product exhibited carbonyl absorptions. at 1808, 1780, and 1760 cm'1 while the nmr spectrum consisted simply of an AA'BB' aromatic multiplet centered at 6 8.0- This data identified the thermal product as benzocyclobutadienoquinone SQ“‘ and was consistent with the nmr and ir spectra reported“5’“7 for an authentic 22 sample of SS. The formation of SS from the bromination product of SS by the thermal elimination of hydrogen bromide suggested that the expected product SS was not obtained. The mass spectrum of the bromination product SS showed parent peaks at m/e 296, 294, and 292 with an intensity ratio of 1:2:1 in accordance with that expected for a molecule containing two bromine atoms. This data together with the elemental analysis indicated a molecular formula of CBH6Br202 for SS. The nmr spectrum of SS showed a one proton multiplet at 6 4.74 and a two proton multiplet at 6 3.67. The low ‘field nmr multiplet was assigned to a bromomethine hydrogen while the signal at 6 3.67 indicated the presence of allylic hydrogens. The most distinct features of the ir spectrum of SS were a cyclobutanone singlet carbonyl absorption at 1795 cm'1 and an olefinic absorption at 1615 cm-1. These ir absorption frequencies were very similar to those reported for phenylcyclobutadienoquinone“°. Dissolution of the bromination product SS in deuterated dimethylsulfoxide (DMSO), a mild base, resulted in the formation of SS as evidenced by the nmr spectrum of the solution. Treatment of SS with DBN“9 resulted in the quantitative formation of benzocyclobutadienoquinone SS. In addition, SS was not reduced under mild conditions 23 of hydrogenation (10 lb/inz, Pd/C) and failed to react with bromine paralleling the resistance to such reagents exhibited by phenylcyclobutadienoquinone. It appeared, therefore, as if SS contained a cyclo- butadienoquinone moiety and accordingly it was concluded that SS was 3,4-dibromobicyclo[4.2.0]-7,8-octanedione. OTMs Br 0 I, f9 rs ' ‘ 33.1110 ‘9 Qfl OTMs 0 £1 Qé Q9 It seems likely that the desired dibromide SS is an intermediate in the formation of SS. Acid catalyzed bromination of SS followed by spontaneous loss of hydrogen bromide would lead to the observed product. Ofi/OTMS ,9 Br £170 Br . u —» an —>;Oc \OTMs k—wgo Br LII-KO B £1 £2 Q& \ (\o An alternative method of bromination of SS which might have circumvented the problems encountered in the direct bromination procedure was the use of NBS. This reagent is known to generate bromine in low concentrationss° 24 and it was anticipated that the introduction of the bridgehead bromine could possibly be avoided. The expected product from NBS bromination of SS was bromo- ketone SS which could be dehydrobrominated to SS. Br TMs —> I OTMs 2 Treatment of SS with three equivalents of NBS in \ \O O l ._—__—;> \\ §O O éZ % éé refluxing carbon tetrachloride under sunlamp irradiation provided a red-brown oil which led to the isolation of a yellow crystalline material, mp 127-130°, upon purification. This product was identifiedas benzo- cyclobutadienoquinone SS by comparison of its nmr and ir spectra to those of an authentic sample. One can envision a number of plausable mechanisms which account for the formation of SS. Production of SS followed by loss of hydrogen bromide in either of two ways would result in the formation of SS or SS. Subsequent bromination and dehydrobromination of these intermediates would provide SS. 25 4/0 f0 /—> ’\ —> 'V‘ ‘\o “0 SS Br Br ¢0 / / \l m 0 Q2 or ——>: i \\ L—dgb Br QC éé Alternatively intermediate SS could be brominated at_ the bridgehead positions followed by dehydrobromination to produce SS. _ , , . -_.__—-————— 0 Sr ,OTMs 7 z/0 w I J ——> I ’7 ————> C:\ ——> I\ .\OTMs ,\ 1h? \0 ’/’ §0 «21 94’s 99. Diethylamino-l,4-butadiene SS51 has been shown to undergo Diels-Alder cycloadditions with a number of electrophilic olefins.5”52 Ciabattoni and Berchtold53 have shown that this diene reacts with diphenylcyclo- propenone S to produce 2,7-diphenyltropone SS. The 26 product arises presumably from the Diels-Alder adduct S1 upon elimination of diethylamine. LNJ LN; ff? + il>x=o '-€> [:;:;£§L=o --9>[::::E:13 \ (p H} ¢ ¢ feé 3: 9% 92 It was expected that cycloaddition of diene SS with a suitably substituted cyclobutene would produce inter- mediate SS which could then eliminate diethylamine with the formation of a potential precursor to dione g. This synthetic plan is outlined in Scheme III. Scheme III LJ ’ LJ Lx' X' ' i' ———> ——> —> 2 r—Y ‘7’ Y Y x Y' Y! [j 3 / \ Qé With this aim 2,2-dichloro-3-pheny1cyclobutenone SS was treated with SS in refluxing benzene. The only isolable product from this reaction was the starting cyclobutene SS. 27 When phenylcyclobutadienoquinone was utilized as the dienophilic component in benzene at room temperature, a red-brown gum was obtained from which an identifiable product could not be isolated. Accordingly this synthetic approach was abandoned. The synthetic plan directed toward the synthesis of S which received the major share of attention was based on the synthesis of the novel diketone S-cyclooctene-1,2- dione SS5“ and is depicted in Scheme IV. Scheme IV Br 0 0 0 ——> ——> o 0 0 Br BR 2 Since SS is functionalized such that theoretically bromine can be introduced into either the allylic or a-carbonyl positions, a bromination-dehydrobromination sequence was envisioned for the introduction of the double bonds. The initial attempt to synthesize SS was based on the work of Bloomfield"3 who has reported the orbital symmetry allowed thermal conrotatory ring opening of {S to cycloOctatriene SS. 28 CH TMS TMs . TMs TMs £1 19 1% It was therefore anticipated that SS would be available from trans-l,2-dicarbomethoxy-4-cyclohexene zgss by a modified acyloin condensation followed by thermal ring opening and hydrolysis as shown in Scheme V. Such a sequence has been used by Mori, Nakahara, and Nozaki56 for the synthesis of large ring a-diketones. Scheme V /. COZCH 3 | ::->O::TMS ‘ a -- TMs ‘0 ’COZCH3 zz Zé 1s . 22 This sequence was successful to a point. Trans ester 1% was prepared according to literature methods57 and successfully cyclized to ZS. The thermal ring opening of ZS was initially performed in tetrachloro- ethylene in order that the reaction could be monitored by nmr spectroscopy. The appearance of additional 29 olefinic and allylic hydrogen absorptions in the nmr spectrum of a solution of SS which had been heated at 105° for several hours indicated that the conversion of ZS to ZS was proceeding as expected. Attempts to force the reaction to completion by heating the sample for longer periods of time were frustrated. The maximum concentration of ZS was attained after nine hours of heating at 105° and thereafter decreased with time. When a sample of the ZS-ZS equilibrium mixture was hydrolyzed an oily mixture was obtained. The ir spectrum of this mixture showed some evidence of the presence of SS but the unfavorable equilibrium position rendered this synthetic scheme rather impractical and a new synthesis of S2 was sought. The boron trifluoride etherate catalyzed conversion of epoxides to acyloins by the use of DMSO58 proceeds in high yield and has been successfully applied to the oxidation of epoxycyclooctane to Z-hydroxycyclooctanone.59 It seemed reasonable therefore that the known 5,6-epoxy- cyclooctene ZS5° could be easily converted to Z-hydroxy- S-cyclooctenone ZS which in turn could be oxidized to diketone SS as outlined in Scheme VI. 30 Scheme VI 0 ———> e0: 0H 0 LE 1Q 22 This sequence proved successful as ZS was converted to ZS by DMSO - boron trifluoride etherate in 75% yield. Oxidation of ZS with cupric acetate61 in acetic acid - water afforded SS in 51% yield. Attempts to increase the yield of this step by use of ferric chloride,62 3 cerium nitrate,6“ bismuth oxide,°"63 bismuth acetate,6 and ammonium nitrate-cupric acetate65 were not successful. The structure of SS was confirmed by spectroscopic data. The ir spectrum of SS exhibits carbonyl absorptions at 1723 and 1708 cm'1 with a shoulder at 1693 cm-1. Such multiplet carbonyl absorption is characteristic66 of a-diketones and arises from coupling of the symmetric and antisymmetric stretching modes of the carbonyl groups. Also present are absorptiOns at 3530 and 3380 cm'1 corresponding, respectively, to the intermolecular and intramolecular hydrogen bonded hydroxyl group of the enol form of SS. These absorptions are weak, however, and SS exists mainly as a diketone. 31 Leonard and Mader67 have studied the ultraviolet spectra of a series of a-diketones and have established that the absorption maximum of these systems undergoes a hypsochromic shift as the geometry of the carbonyl groups changes from a cis or trans coplanar configuration to a perpendicular configuration. The intercarbonyl angle of 3,3,7,7-tetramethyl- 1,2-cycloheptanedione ZZ has been estimated to be 90-llO° on the basis of space filling molecular models, while the value for 3,3,8,8-tetramethyl-l,Z-cyclooctane- dione ZS was approximated to be loo-140°. 11 1% Compounds ZZ and ZS have ultraviolet absorption maxima of 337 nm and 343 nm respectively in 95% ethanol solution. Using this data the angle between the carbonyl groups of SS can be estimated. A solution of SS in 95% ethanol shows an ultraviolet absorption maximum of 335 nm and accordingly its intercarbonyl angle is approximated to be 90-100°. 32 Birnbaum, Cookson, and Lewin68 have compared the ultraviolet spectra of diketones ZS and SS. 12 132 Compound SS in cyclohexane showed a band at 238 nm (e 2600) which was absent in the spectrum of ZS. This band was interpreted to be a result of an intramolecular charge transfer between the double bond and the diketone moiety of SS. Dione SS in cyclohexane exhibits an ultraviolet absorption maximum at 230 nm (e 99). The Spectrum reported for ZS does not include a maximum in the region of 230 nm. This suggests that the 230 nm absorption of SS may be due to an intramolecular charge transfer effect although a comparison of the extinction coefficients indicates that only a weak interaction is occurring. The nmr spectrum of SS consists of an olefinic proton triplet at 6 5.88 and a multiplet at 6 2.53 which corresponds to the a-carbonyl and allylic protons. The multiplet was resolved into two separate multiplets when the spectrum was recorded in the presence of tris (dipivalomethano)europium (III).69 33 The mass spectrum of SS exhibited a parent peak at m/e 138 and prominent peaks at m/e 110 and 82 which arise from the fragments resulting from the loss of one and two molecules of carbon monoxide respectively. The structure of SS was further confirmed by the formation of the quinoxaline derivative SS, mp 117-119°, whose spectroscopic pr0perties were in full accord with the assigned structure. In addition, the conversion of SS to 3,8-di(p-methoxybenzilidene)-5-cyclooctene-l,2- dione SS served to confirm that SS contained two a-carbonyl methylene groups. The properties of this interesting molecule will be discussed subsequently. CH30¢ N o / NI) . ék CH3°¢ éé The initial attempt to convert SS to S was a simple oxidation by dichlorodicyanoquinone (DDQ). This procedure was used by Vogel to convert ketone SS to ketone Z.2“ ‘ l ‘ ‘1. k. £223 1 34 As discussed previously, ketone Z does not exhibit any aromatic properties. The ease of oxidation of,SS is due, apparently, to the formation of a fully conjugated system. It was anticipated that a similar effect would be operative in the oxidation of SS to S. Heating a solution of SS and DDQ in benzene in a sealed tube at 120° for eight hours, however, failed to produce a reaction. The dione SS was recovered unchanged. Returning to the synthetic plan outlined in Scheme IV, the bromination of SS was considered. Allylic bromination of SS with NBS might be expected to provide dibromodiketone SS although allylic radical rearrangements7° would certainly occur and decrease the yield of SS. Dehydro- bromination of SS would then produce S. B o 0 O —-> ——> Br Q2 1% 2 When a solution of SS and two equivalents of NBS in refluxing carbon tetrachloride containing a catalytic amount of benzoyl peroxide was irradiated with a sunlamp, a black tar was produced. This material failed to provide any identifiable product. An attempt to effect the desired bromination without irradiation or initiator afforded the same intractable material. 35 The alternative mode of bromination would provide dibromodiketone SS which was expected to afford S upon' dehydrobromination. $22 a Br , a The initial attempt to synthesize SS utilized pyrrolidone hydrotribromide (PHT)71 as the brominating reagent. A solution of SS and PHT in tetrahydrofuran was stirred at room temperature for twenty hours. Bromination had occurred as evidenced by the precipitation of pyrrolidone hydrobromide from the reaction solution and upon workup several oils were obtained. All of these products showed infrared carbonyl absorptions. The nmr spectra, however, revealed that all of these products were deficient in olefinic proton absorptions due to the bromination of the double bond. Treatment of SS with cupric bromide72 in 1:1 chloro- form-ethyl acetate solution at 70° for twelve hours afforded SS as white crystals, mp 138-141°. The structure proof of SS was based mainly on spectroscopic evidence. The elemental analysis and mass spectral parent peaks of m/e 298, 296, and 294 which occurred in a ratio 36 of 1:2:1 as expected for a dibromide established the correct molecular formula of C8H8Br202 for SS. *The position of the infrared carbonyl absorption of a-halogen cycloalkanones has been used as a tool in configurational analysis.73 When an a-bromine atom occupies an equatorial position of a cycloalkanone and is approximately coplanar with the carbonyl group, the infrared carbonyl absorption is shifted 15-22 cm.1 to higher frequency relative to that of the unsubstituted cycloalkanone. There is no change in position when the bromine is in an axial position. Leonard and Robinson’“ have utilized such an infrared analysis to assign the stereochemistry to the isomeric 3,7-dibromo-3,7-dibenzy1-1,2-cycloheptanediones SS and SZ. The cis isomer SS has one bromine atom in an SS - cis SZ - trans equatorial position and one in an axial position. Accordingly its ir spectrum showed carbonyl absorptions of 1715 and 1698 cm-1 corresponding to the carbonyl groups adjacent to the equatorial and axial bromine atoms 37 respectively. The trans isomer éz is symmetrical with both bromine atoms in equatorial positions and shows the expected single infrared carbonyl absorption at 1720 cm'l. The stereochemistry assigned to dibromide §§ is trans. Molecular models indicate that the trans diequatorial configuration should be the most stable. This assignment is confirmed by the infrared carbonyl 1 absorptions of §§ at 1740 and 1727 cm- which are, respectively, 17 and 19 cm.1 higher than the corresponding peaks of diketone Qg at 1723 and 1708 cm-1. The effect of a-carbonyl halogen atoms on the uv spectrum is Opposite that encountered in the infrared spectrum. Axial bromine atoms cause a bathochromic shift of the uv maximum of the carbonyl group of a-bromo cycloalkanones relative to the corresponding unsubstituted cycloalkanones. An equatorial bromine atom, on the other hand, causes little or no change in the uv absorption position of the carbonyl group. The magnitude of the effect of an axial bromine atom is approximately 28 nm with an attendant increase of the extinction coefficient by a factor of 100.73e»73f’75 Dibromodiketone fié does not seem to be amenable to configurational analysis by uv spectroscopy. The positions of the uv absorptions of 11 are essentially unchanged relative to those of Q2 although the extinction coefficients are markedly greater. 38 The assigned trans diequatorial configuration of Vgé is further substantiated by its nmr spectrum. It has been determined that a-bromo carbonyl methine protons which have axial configurations are deshielded and therefore have chemical shifts further downfield than their equatorial counter parts.76 For example, the methine proton of cis-4-phenyl-Z-bromocyclohexanone occupies an axial position and gives rise to an nmr signal at 6 4.87. The methine proton of the corresponding trans isomer is equatorial and exhibits an nmr signal at 5 4.38. Thus the single methine proton nmr absorption of éé at 6 5.15 is consistent with a trans diequatorial configuration. This nmr absorption consists of a four line pattern which was expected for an X portion of an ABX system. Further features of the nmr spectrum of §§ inc1ude an olefinic multiplet at 6 6.05 and a multiplet at 6 2.90 representing the AB part of the ABX system. These assignments were verified by decoupling experiments. Chemical evidence confirming the structure of 8% was obtained by the formation of the quinoxaline derivative 88. Compound 88 was also of interest as it served as the precursor to the quinoxaline derivative of the target compound l,2-cyclooctatrienedione. 39 Br 2 H‘ ./ f)» 31) N Hs B 6 7 I' 4% 8% 82 Treatment of 88 with DBN in DMSO led to the formation of 88, the quinoxaline derivative of g. The structure of 88 was confirmed by its spectroscopic properties. The mass spectral parent peak of m/e 206 together with the elemental analysis established the correct molecular formula of C14H10N2 for 88. The nmr spectrum of 88 shows an aromatic AA'BB' pattern at 6 7.92 corresponding to the hydrogens of the benzene ring. The a-imino hydrogens, H2 and H7, appear as a doublet of an AB quartet, J = 11.5 Hz, at 6 6.88. The other half of the AB quartet at 6 6.43 arises from H3 and H6 and appears as a doublet of doublets, J = 1.5 Hz, due to the coupling to hydrogens H4 and HS which appear as a doublet at 6 6.15. The coupling constant for the coupling of H3 and H4 (H5 and H6) is expected to be 9-13 H277 if a planar triene moiety is present in 88. The observed value of 1.5 Hz demonstrates that only a weak interaction is occurring and therefore it was concluded that 88 exists in a nonplanar conformation such as 88. 40 @3113 ’51) \. \x 28 88 This idea is further substantiated by the electronic spectuum of 88 which exhibits an absorption maximum at 354 nm. The quinoxaline derivative of dione 88 shows an absorption maximum at 323 nm.67 On the basis of this value the absorption maximum of 88 is predicted to be 353 nm. Since the uv spectrum of 88 agrees almost exactly with that expected for 88, it must be concluded that the C4-CS double bond does not possess a geometry which allows for n-orbital interaction as expected for conformation 88. It is expected that 88 should be more planar than 8 because the imino carbon atoms are maintained in a fully unsaturated six-membered ring. The carbonyl groups of 8, on the other hand, are expected to repel each other due to electrostatic interaction and thereby cause a deviation from a planar geometry. The nonplanity of 88 clearly suggests that 8 will not be a planar molecule and therefore any aromatic character which it might possess will be obscured. The conversion of 88 to 8 appeared to be a simple task as a variety of dehydrohalogenation reagents are known. This, however, was not the case. Dibromide 88 reacted easily with a number of different dehydro- 41 halogenating reagents under a variety of conditions but the products of the reaction were generally intractable materials. Table I summarizes the unsuccessful attempts to dehydrobrominate 88. ’ It was clear from these experiments that the dehydrohalogenation was complicated by side reactions and possibly that the desired product 8, if formed, was undergoing further transformations under the reaction conditions. In several experiments the starting dibromide 88 was the only product which could be isolated although the quantity obtained was usually less than the original amount. Another interesting observation was the fact that material balance was not maintained in all cases indicating that some of the product material was water soluble. This was verified by the colored aqueous washes in the workups of the various reactions. Attempts to isolate products from the aqueous phases, however, were fruitless. Particularly interesting is the fact that the ir spectra of the oils obtained in experiments 1 and 13 were nearly identical. The carbonyl infrared absorption at 1800 cm.1 suggested that the product might be the bicyclic tautomer 88. The nmr spectrum of these oils did not bear out this contention and suggested that a mixture of materials was present. The small amount of material obtained precluded a further purification and 42 Table I. Summary of attempts to dehydrobrominate 88. Exp. Dehydrggzégfiinatlng Conditions Results* Ref. 1 DBU DMSO, 25°, intractable 78 12 hr material and yellow-red oil with ir carbonyl absorption at 1800 cm-1 2 DBU CHClS, 25°, intractable 78 4 hr material 3 Et3N C6H6, 25°, brown oil 79 4 hr which yielded 50% s.m. 4 LiCl DMP, 140°, brown oil 80 1 hr exhibiting broad ir carbonyl absorptions 5 NaHCO3 DMSO, 100°, brown oil 81 4 hr consisting of four components none of which showed ir carbonyl absorptions 6 DBU EtZO, 0°, 50% s.m. 78 2 hr recovered 7 AgNO3 EtOH, 60°, 60% s.m. 82 1 hr recovered 8 HMPA 130°, yellow oil 83 1/2 hr consisting of three components; ir carbonyl absorptions at 1775 and 1650 cm'1 43 Table I. (Continued) Dehydrohalogenating . . * Exp. reagent Condltions Result Ref. 9 Et4N+C1' CHSCN, 82°, 60% s.m. 84 18 hr recovered 10 DBN CH2C12, 0°, brown oil 49 2 hr 11 Proton Sponge DMSO, 60°, s.m. 85 4 hr recovered 12 LiCl HMPA, 54°, red-brown oil 86 10 hr 13 LiBr, LiZCO3 HMPA, 55°, yellow oil 86 4 hr exhibiting ir carbonyl absorption at 1800 cm-1 14 LiCl DMF, 85°, 33% s.m. 80 21 hr recovered 15 CaCO3 DMF, 80°, s.m. 87 3 hr recovered 16 DBN THF, -76°, s.m. 49 1 hr recovered 17 DBN THF, -33°, s.m. 49 1 hr recovered 18 DBU 2:1 DMSO- s.m. and 78 THF, 0°, brown gum 1/2 hr 19 DBU/TCNE CHZCIZ, 0°, intractable 78 1 hr material *slm. = starting material 44 structure elucidation. One can visualize a Favorski type elimination product 88 which would explain the presence of a cyclobutanone moiety. Compound 88 could Br Br 2% then undergo further reaction to product a number of additional products. Experiment 19 describes an attempt to trap any dehydrohalogenation products of 88 by the use of tetracyanoethylene as a dienophile. Unfortunately only intractable material was obtained from this experiment. Hexamethylphosphoramide (HMPA) has been used successfully in the past to effect dehydrohalogenation.83 The yellow oil obtained in experiment 8 was interesting as it exhibited a carbonyl ir absorption at 1650 cm-1 indicating thepresence of an a,B-unsaturated carbonyl group. The small quantities of product which were being obtained prompted a reduction in the temperature at which the reaction was being performed. When a solution of 88 in HMPA was heated to 75° for four hours only one product, in addition to unreacted starting material, was obtained. 45 This crystalline compound, mp 101-103°, was shown to have an elemental composition of C8H7BrO2 on the basis of its mass spectral parent peaks of m/e 216 and 214 whose intensity ratio was 1:1 and the elemental analysis. The ir spectrum of this material showed carbonyl and olefinic absorptions at 1662, 1622, and 1600 cm-1 respectively as well a hydroxylic absorption at 3365 cm-1 indicating the presence of an intramolecular hydrogen bonded hydroxyl group. One sample of this material showed, in addition to these absorptions, a carbonyl absorption at 1714 cm-1 in conjunction with a reduced hydroxylic absorption. This suggested that an enol-keto tautomerization was occurring at a position substituted with an equatorial bromine atom. The peak at 1662 cm-1 is characteristic of a,B-unsaturated ketones and, in fact, is identical to that reported for 2,4-cycloocta- dienone.88 The nmr spectrum of this material in deuterated chloroform showed a one proton singlet corresponding to an intramolecularly hydrogen bonded hydroxylic hydrogen at 6 7.86, a three proton olefinic hydrogen multiplet at 6 6.64, a one proton olefinic hydrogen at 6 5.73, and a broad two proton allylic hydrogen singlet at 6 3.16. When the nmr spectrum was taken on the sample in deuterated DMSO the hydroxyl proton was observed as a broad singlet at 6 10.5-8.5. In addition, the broad 46 singlet at 6 3.16 was resolved into a sharp two proton doublet, J = 8.0 Hz. The magnitude of this coupling constant is characteristic of the coupling observed between allylic hydrogens and the adjacent olefinic hydrogen. On the basis of this spectroscopic data it was concluded that this material was 3-bromo-2-hydroxy- 2,5,7-cyclooctatrienone 88. This novel ketone results from a single dehydrobromination of 88 to form 3-bromo- 5,7-cyclooctadiene-1,2-dione 88 followed by enolization. r Br :r -H l/O O ____£> ——e> 0 CH30¢ CHso" é€ éé $Q§ SS p-Methoxybenzaldehyde was selected as the condensating agent for the conversion of 88 to 88 because its aromatic hydrogens would appear as a well defined AB quartet in the nmr spectrum and thereby be easily distinguished from any aromatic absorptions which might arise from the parent ring of 888. The piperidine catalyzed condensation of 88 and p-methoxybenzaldehyde proceeded readily with the production of beautiful yellow crystals, mp 162.5-165°, of 88 in 39% yield. The structural assignment of 88 was confirmed by spectroscopic data. The molecular formula of C24H2204 was established by elemental analysis and the mass spectral parent peak at m/e 374. The ir Spectrum of 88 showed a conjugated carbonyl absorption at 1675 cm’l. The most interesting aspect of the nmr spectrum of 88 was the position of the absorption of the olefinic benzilidene hydrogens which appears as a singlet at 6 7.9. The ring olefinic protons show resonance at 6 6.25. The difference between these two absorption positions is due to the benzilidene olefinic hydrogen being in the 9 This serves deshielding region of the carbonyl group.9 to confirm that the phenyl groups are trans to the diketone moiety in agreement with the stereochemistry expected on the basis of a consideration of the mechanistic aspects of the condensation reaction.‘°° 56 The isomerization of 88 to 888 was conducted in refluxing triethylene glycol with 10% palladium on charcoal as the catalyst. The resulting brown oil consisted of six components for which a chromatographic separation did not seem feasable. The spectrum of the crude mixture contained a hydroxylic absorption at 3500 cm-1 suggesting the presence of an alcohol as one of the components of the mixture. Also present was a broad carbonyl absorption from 1685 to 1725 cm'l. The nmr spectrum of the crude mixture did not exhibit the expected AB aromatic quartet but rather an adulterated triplet aromatic absorption. The integration ratio of aromatic to methoxy protons, however, remained 4:3. There was no olefinic proton absorption present. This indicates that the desired 888 was not present in the crude reaction mixture. Compound 88 was useful for other purposes however. Lithium in ammonia”l reduction of 88 provided 3,8-di(p- methoxybenzyl)-S-cyclooctene-1,2-dione 888 in 85% yield. The structure of 888 was in full accord with its spectroscopic properties and elemental analysis. It was expected that 888 could be brominated at the a-carbonylpositions to form 888 as the 3,7- dibromo-S,7-dibenzy1-1,2-cycloheptanediones 88 and 88 are known. Dehydrobromination of 888 was to then be 57 effected by the use of tetraethylammonium chloridea“ a reagent which has been shown to dehydrobrominate 2- benzyl-Z-bromoketone 888 exclusively to the corresponding endocyclic a,B-unsaturated ketone 888. ®w¢ 88% ééé This synthetic sequence is shown in Scheme XI. Scheme XI CH30 CH30 CH38£ CH30¢ / o o —_;> '—-€> ‘llilpE:ér_e> 'lli!.E:o \ :: Br CH 0¢ - CH30¢ CHso CH3O¢ 3 R $132 M9 «UR Attempts to brominate 888 with cupric bromide or pyrrolidone hydrotribromide resulted only in the recovery of starting material. A light yellow oil was obtained upon treatment of 888 with pyridinium hydrobromide tribromide in acetic acid solution. This oil showed an ir carbonyl absorption 58 at 1735 cm-1 indicating that a bromination had occurred. The nmr spectrum of this oil, however, exhibited a very low ratio of phenyl protons to methoxy protons indicating that extensive bromination of the phenyl rings had occurred. One attempt to chlorinate the three and eight 1°2 in carbon positions of 888 with sulfuryl chloride tetrachloride led only to the recovery of starting material. An interesting derivative of 8 is 3,8-dihydroxy- l,2-cyclooctatrienedione 888. An attractive feature of this compound is that the hydrogen bonding between the hydroxyl and carbonyl groups was expected to confer a measured degree of planarity to the molecule and thereby enhance any aromatic character which might be present. Several brief attempts to synthesize 888 from diketone 88 were made. Synthetically the plan was a simple one as shown in Scheme XII. There are a number of conceivable methods available for the conversion of 88 to S-cyclooctene-1,2,3,4-tetraone 888. The tetraketone was then expected to tautomerize to 888 as a fully ,conjugated system would result. 59 Scheme XII O-H O 0 O ——> ——> O O 0 O O-H {8% Ré Ré 1°3 is a reagent which has been Selenium dioxide shown to oxidize a-carbonyl methylene groups to carbonyl functions. Upon treatment of 88 with selenium dioxide in either acetic anhydride or in aqueous dioxane solution only asphalt like material was obtained. There are available a number of indirect methods of converting ketones into a-diketones. a-Oximino ketones, which are prepared by the action of alkyl nitrites on ketones, have been hydrolyzed to diketones by a number of different types of reagents such as iron pentacarbonyl in the presence of a catalytic amount of °“ pyruvic acid,”5 and boron trifluoride etherate,1 levulinic acid.”6 It was therefore anticipated that the bis a-oximino diketone 888 could be prepared from diketone 88 and then hydrolyzed to tetraketone 888 as depicted in Scheme XIII. 60 Scheme XIII /' ' \‘ 0 0 o 0 £2 HIE 'l/L‘x’: 1°7 in methanol Treatment of 88 with isoamyl nitrite in the presence of anhydrous hydrogen chloride at -10° failed to produce any reaction and the starting material was recovered unchanged. The use of methyl nitrite108 in the place of isoamyl nitrite produced the same result. As discussed previously geminal dihalides can be , hydrolyzed to carbonyl groups. It was conceivable that bromination of 88 might result in the formation of 3,3,8,8-tetrabromo-S-cyclooctene-1,Z-dione 888. This tetrabromide could then be hydrolyzed to 888 by a reagent such as silver trifluoroacetate."‘6 Interestingly when 88 was treated with cupric bromide the starting material was recovered quantitatively. Apparently 88 is not susceptable to further bromination presumably due to the steric hindrance which would result. Another promising method for the conversion of 88 to 888 involves the Kr6nke reactions.”9 In this sequence an a-bromoketone is converted to the corresponding pyridinium bromide which is then reacted with p-nitroso- 61 N,N-dimethylaniline to form a nitrone. Upon hydrolysis the nitrone yields an a-diketone. Accordingly gé was to be converted to its bis pyridinium salt ll; which in turn was to be reacted with p-nitroso-N,N-dimethylaniline to form nitrone ll§ which could be hydrolyzed to tetra- ketone 4%& as shown in Scheme XIV. Scheme XIV + ¢- NCCHS) 0\N/ Br 0 a :——> O ‘ N r o/+ \¢- -N(CH3) 85 117 118 114 ’Vb ’Vb’b N'b’b ’Vb’b Unfortunately treatment of @§ with pyridine in refluxing toluene failed to produce any llz, rather a black intractable material was obtained. Another derivative of g whose synthesis seemed plausible was 3-bromo—l,2-cyclooctatrienedione llg. The reaction of g; with NBS was expected to lead to four possible bromination products, lgg, lgl, lzg, and téé'. It was interesting though that each of these conceivable products would lead to the same product, llg upon treatment with base. 62 r r Br r BI‘ Br OH 2 5 + : O o Ré 24 %%9 iii Br r Br 0 Br Iéé Iéé The synthesis of llg suffered one major disadvantage. Its bicyclic tautomer %%4 would be capable of forming benzocyclobutadienoquinone by elimination of hydrogen bromide. 1‘ Br 0 __./ 4 cm a *° klfi %%A $2 Surprisingly NBS bromination of 2; produced a single yellow crystalline product, mp 106-109°, in 85% yield. The composition of this material was C8H602Br2 as determined by elemental analysis and the mass spectral parent peaks of m/e 296, 294, and 292 whose relative intensities were 1:2:1 respectively. 63 The infrared spectrum of this material lacked the hydroxyl absorption exhibited by the starting material indicating that the molecule was existing as a diketone. The two distinct ir carbonyl frequencies at 1677 and 1724 cm.1 confirmed this idea. The carbonyl absorption at 1677 cm"1 suggested the presence of an a,B-unsaturated ketone while that at 1724 cm-1 could be interpreted as either an a-bromoketone or simply as an a-methylene ketone. The nmr spectrum of the bromination product exhibited a doublet at 6 7.68 (HA), an overlapping pair of doublets at 6 6.55 (HB), a pair of doublets at 6 5.95 (HC), a heptet at 6 5.23 (HD), a pair of doublets at 6 3.84 (HE)’ and a pair of doublets converged to a triplet at 6 3.22 (HF). Each signal integrated for one proton. A consideration of the observed coupling constants in conjunction with decoupling experiments established the couplings and coupling constants reported in Table III. The absorptions at 6 3.84 and 6 3.22 suggested the presence of either two allylic hydrogens or two a-carbonyl hydrogens. Another possibility is the presence of an allylic and an a-carbonyl hydrogen. The chemical shift of the absorption due to HA together with the observation that HA is coupled only to HC indicated that HA might be a B-hydrogen of an a-bromo-a,B-unsaturated ketone moiety. 64 Table III. Summary of couplings and coupling constants of the bromination product of 33. Coupling Coupling Constant (Hz) HA - HC 6.0 HB - HC 12.0 HB - HD 8. HD - HE 5.5 HD - HF 13.5 HE - HF 13.5 The most critical requirement which any structural formulation for the bromination product must meet is the presence of a hydrogen (HD) which is coupled to three other hydrogens (HB, HE, and HF). Three of the expected bromination products 121, 12%, and 123 fail to meet this requirement. Compound lgg possesses a hydrogen atom which fulfills the coupling constraints of HD. This structural formulation fails, however, as lgg possesses a plane of symmetry which requires that the allylic hydrogens be equivalent. A structure for the unknown which is consistent with all of the constraints imposed by the nmr data is 4%- 65 The coupling constants observed for the bromination product are reasonably close to those expected for 125. The coupling between HA and HC’ however, is lower than the expected 9-13 Hz.77 The observed value of 6 Hz is consistent with a conformation in which the angle between HA and HC is approximately 45°. The uv spectrum of the unknown is also consistent with a conformation in which the double bonds of 125 are not coplanar. The calculated absorption maximum of 125 is 339 nm. The experimental value of 299 nm reflects the lack of complete conjugation between the double bonds. A molecular model of the conformation of 125 in which the angle between the double bonds is approximately 45° shows that the angles between HD and HE and HF are - H D E and HD - HF coupling constants of 5.5 and 13.5 Hz, approximately 80° and 170° respectively. The H respectively, are consistent with the general relationship between the dihedral angle and coupling constant of vicinal hydrogens as deduced by Karplus.11° 66 The carbOnyl absorptions of diketone 55 occur at 1723 and 1708 cm.1 due to coupling of the symmetric and antisymmetric stretching modes of the individual carbonyl groups. It has been suggested that the absorption position of the individual carbonyl groups can be approximated by the mean of the coupled frequencies.111 Accordingly the unperturbed frequency of the carbonyl groups of 55 is estimated to be 1716 cm-1. The carbonyl absorption of 555 at 1724 cm'1 is slightly high when compared to that of 55.‘ The bent conformation of 555, however, provides a plausible explanation. In this conformation the nonconjugated carbonyl group of 555 has a configuration which very roughly approximates that of a cyc10pentanone. It seems reasonable that this slight compression of the carbonyl bond angle should be sufficient to cause the increase in the carbonyl frequency relative to that expected. Two plausible mechanisms can be envisioned for the formation of 555 as outlined below. Mechanism I Br OH O 426% 67 Mechanism II éék kéé kéé In mechanism I rearrangement of the initially formed radical 555 would lead to the bicyclic radical 555 which could be brominated to form bicyclic dibromide 555. The acid catalyzed rearrangement of 555 would then afford 555. ' Alternatively enolization of 55 would provide 3-bromo-l,2-dihydroxycyclooctatetraene 555 which could be oxidized to form radical 555. Rearrangement of 555 to radical 555 followed by bromination would lead to the formation of the enol 555 of 555. Neither of these mechanisms is completely satisfactory. Mechanism I suffers from the fact that intermediate 555 is expected to be a reasonably stable compound. Molecular models do not reveal an inordinate 68 amount of ring strain in 555 thereby eliminating the relief of strain as a driving force for the ring opening. Mechanism II is deficient as the cyclooctatetraene derivative 555 seems to be more strained than 55 on the basis of a comparison of the molecular models of these compounds. Furthermore, there was no evidence of the presence of 555 in the samples of 55. Although 555 was not one of the expected products from the bromination of 55, it was a suitable precursor to 555. Treatment of 555 with triethylamine in chloroform solution produced an immediate reaction. The ir spectrum of the reaction mixture showed a carbonyl absorption which is characteristic of benzocyclobutadienoquine 55 and lacked the carbonyl absorptions of 555. When a sample of 555 in deuterated chloroform was treated with a limited amount of triethylamine, the nmr spectrum of the reaction mixture showed the aromatic proton AA'BB' pattern of 55 along with the signals due to the starting material. There as no indication of the presence of the expected products 555 and 555. Thin layer chromatographic analysis of the reaction mixture revealed the presence of 55 as the only product in addition to nonmoving brown material. From these experiments it was concluded that 555 had been formed. The production of 55 from 555 requires 69 Br Br Br ép ," // 1’ Cr» if cue—e c- B‘ 5&5 } 4&2 \ ({r 4% QR the intermediacy of the 555-555 equilibrium mixture. The factthat neither of these intermediates could be observed in the nmr spectrum of the reaction mixture was surprising as 1,3,5-cyclooctatriene and its bicyclic valence tautomer exist as a 85%-15% equilibrium mixture at 100°.112 The energy of activation for the inter- conversion of 555 and 555 must be small since 55 is formed immediately from 555 at room temperature. The dehydrobromination of 555 was expected to proceed readily with the formation of an aromatic system as the driving force. Although l,2-cyclooctatrienedione was not isolated, some interesting organic chemistry has been generated. The failure of 55 to produce 5 upon treatment with base suggests that 5 may not be a stable compound. The demonstration of the nonplanarity of 55 implies that 5 will not be planar and therefore not aromatic. 70 Suggestions for Future Stugy_ The synthetic plan outlined in Scheme II should be successful when a slight modification is incorporated. cis-l,2-Dimethyl-4-cyclohexene-l,2-dicarboxylic acid 555 is available from the cycloaddition of 2,3-dimethylma1eic anhydride and butadiene.113 Esterification of 555 followed by the modified acyloin condensation would be expected to lead to the formation of 555. Treatment of 555 with pyridinium hydrobromide perbromide would then provide 555. The presence of the bridgehead methyl groups in 555 would prevent the bromination - dehydrobromination which had occurred in the formation of 55 from 55. Dehydrobromination of 555 would result in the formation of 555, the bicyclic tautomer of 3,8-dimethy1-l,2-cyclo- octatrienedione 555. OTMs co2 CH3 l l --5> @coj——> H ——>O00:3 CH3 _>CL\OTMS iéé Br 44/) / {—f0 > Br£L\o > \ ‘ o T— Ré 12% R1 EXPERIMENTAL General Procedures The infrared spectra were recorded on a Perkin-Elmer Model 237B spectrOphotomer. The nmr spectra were obtained using a Varian T-60 spectrometer with chemical shifts reported as 6 values measured from an internal standard of tetramethylsilane. The uv spectra were recorded on a Unicam Model SP-800 spectrophotometer using 1 cm quartz cells. Mass spectra were obtained with a Hitachi Perkin-Elmer RMU-6 mass spectrometer. Melting points were determined on a Thomas Hoover melting point apparatus and are uncorrected. Microanalyses were performed by Spang Microanalytical Laboratory, Ann Arbor, Michigan or Galbraith Laboratories, Inc. , Knoxville, Tennessee. Molecular models were constructed from Framework Molecular Models by Prentice-Hall, Inc., Bnglewood Cliffs, New Jersey. 71 72 3,4-Dibromobicyclo[4.2.0]~6-octene-7,8-dione (Dione 55). 2 To a solution of 2.82 g (l x 10' mol) of 7,8-bis (trimethylsiloxy)--c11.9-bicyclo[4.2.0]-3,7-octadiene‘*3 in 50 ml of anhydrous tetrahydrofuran maintain at -78° 2 mol) of was added dropwise a solution of 6.4 g (2 x 10' pyridinium hydrobromide perbromide in 50 ml of anhydrous tetrahydrofuran over a period of an hour. The solution was stirred for an additional hour. Upon warming to room temperature the solid pyridinium hydrobromide was filtered and the solvent removed under reduced pressure at room temperature. The resulting red-brown oily crystals were triturated with ether and filtered. Recrystallization of the crude product from methylene chloride-cyclohexane produced 0.8 g (27%) of dione 55 as very light yellow crystals: mp l6l-164°; ir (CHClS) 3000 (C-H), 1795 (c=0), and 1615 cm’1 (C=C); nmr (00013) 6 4.74 (m, 2, CflBr) and 6 3.67 (m, 4, allylic); mass spectrum (70eV) 134 (parent). 4 5235. Calcd for C H Br 0 8 6 2 2‘ Found: C, 32.63; H, 2.04. C, 32.65; H, 2.04. 73 Reaction of 3,4:dibr0m0bicyclo[4.2.0]-6-octene-7,8-dione 55 and 1,5-diazabicyclo[4.3.0]—5-nonene (Benzocyclo- butadienoquinone 55). To a solution of 0.6 g (2.04 x 10'3 mol) of 3,4- dibromobicyc10[4.2.0]-6-octene-7,8-dione in 30 ml of methylene chloride was added dropwise, over a period of 3 mol) of 1,5— an hour, a solution of 0.5 g (4 x 10' diazabicyclo[4.3.0]-5-nonene in 15 ml of methylene chloride. The solution was then stirred at room temperature for 20 hr. The solution was then washed well with water and saturated sodium chloride solution and then dried over anhydrous magnesium sulfate. Removal of the solvent afforded 250 mg (92.5%) of benzocyclobutadienoquinone 55: mp 129-132°; ir (CHC13) 1808, 1777, and 1760 cm'1 (c=0); nmr (CDClS) 6 8.00 (AA'BB' pattern, aromatic); mass spectrum (70eV) m/e 132 (parent). 74 Reaction of 7,8-bis(trimethylsiloxftpis-bicycloj4.2.0]- §,J-octadiene and N-bromosuccinimide (Benzocyclobutadien- quinone 55). A solution of 2.82 g (1 x 10' 2 mol) of 7,8-bis (trimethylsiloxy)cis-bicyclo[4.2.0]-3,7-0ctadiene and a catalytic amount of benzoyl peroxide in 60 ml of carbon tetrachlordde and 5.4 g (3 x 10'2 mol) of N-bromo- succinimide was heated to reflux with simultaneous irradiation with a sunlamp for 15 min. Upon cooling the succinimide was filtered and the solvent removed under reduced pressure at room temperature. The orange oily residue was chromatographed on silicic acid with chloro- form as the elutant. The first component eluted gave yellow crystals upon removal of the solvent. Recrystallization of this material from methylene chloride - petroleum ether (bp 40-60°) (1:1) gave 58 mg (4.4%) of benzocyclobutadienoquinone: mp 129-132°; ir (CHC13) 1808, 1777, and 1760 cm‘1 (c=0); nmr (00013) 6 8.00 (AA'BB' pattern, aromatic); mass spectrum (70eV) m/e 132 (parent). 75 7,8-Bis(trimethylsiloxiktrane-bicyclo[4.2.QJ-3,7- octadiene (Bis ether 55). Through a column containing 35 g of basic alumina was passed 150 ml of toluene directly into a 500 m1 ~three neck round bottom flask equipped with a nitrogen inlet tube, a reflux condensor, and a magnetic stirrer. To the flask was then added 3.0 g (1.32 x 10'1 mol) of small, cleanly cut pieces of sodium followed by the addition of a solution of 16.0 g (1.5 x 10.1 mol) of chlorotrimethylsilane and 6.0 g (3 x 10-2 mol) of trans- dimethy1-4-cyclohexene-l,2-dicarboxylate in 25 ml of toluene. The mixture was then refluxed with stirring under nitrogen for 48 hr. Upon cooling the solid material was filtered and the solvent removed under reduced pressure. The yellow residue was distilled under reduced pressure giving 5.9 g (70%) of his ether 55 as a colorless oil: bp 7l-72° (0.025 mm); ir (film) 3000, 2950, 2900, 2840 (C-H) and 1685 cm'1 (TMS-O-C=C-OTMS); nmr (CC14, CHCl3 internal standard) 6 5.67 (s, 2, olefinic), 6 2.16 (s, 6, allylic and cyclobutenyl), and 6 0.15 (s, 18, TMS). 76 2-Hydroxy-5-cyclooctenone (Ketone 55). A solution of 62 g (0.5 mol) of 5,6-epoxycyclooctene in 200 ml of dimethylsulfoxide was stirred at 95° for 90 hr. Boron trifluoride etherate was added in one ml portions at 0, 24, 48, and 72 hr. After cooling the solution was poured into 400 ml of water and extracted with three 100 m1 portions of chloroform. The combined extracts were washed with 50 m1 of water and then dried over anhydrous magnesium sulfate. Removal of the solvent provided a yellow oil which was distilled under reduced pressure. A forerun of 4.4 g of a mixture of starting epoxide and product was collected followed by 52.7 g (75%) of 2-hydroxy-S-cyclooctenone: bp 78-79° (0.5 mm); ir (neat) 3400 (C-OH), 3000, 2912 (C-H), 1700 (C=O), and 1685 cm‘1 (0:0); nmr (0014) 6 5.72 (m, 2, olefinic), 6 4.30 (m, 2, HC-OH), 6 2.0-3.0 (m, 6, allylic and a-carbonyl), and 6 1.70 (m, 2, -CE -CHOH). 2 77 S-Cyclooctene-l,2-dione (Diketone 55). A three neck one liter round bottom flask equipped with a mechanical stirrer and a reflux condensor was charged with 52.7 g (0.375 mol) of 2-hydroxy-S-cyclo- octenone, 168 g (0.84 mol) of cupric acetate monohydrate, 35 m1 of methanol, and 420 ml of 50% aqueous acetic acid. The mixture was heated with an open flame to reflux with stirring for two hr. After cooling the solid material was filtered and washed with water and ether. The combined filtrate and washes were poured into 500 ml of saturated sodium chloride solution. The aqueous solution was then extracted with six 100 ml portions of ether. The combined extracts were washed with saturated sodium bicarbonate solution until neutral and then with saturated sodium chloride solution. After drying over anhydrous magnesium sulfate the ether was removed. The resulting yellow oil was distilled under reduced pressure yielding 26.4 g (51%) of 5-cyclooctene-l,2-dione: bp 56-57° (0.5 mm); mp 35-36.5° ir (CHC13) 3050 (C-H), 1723, 1708, and 1692 cm'1 (C=O); nmr (00013) 6 5.88 (m, 2, olefinic) and 6 2.53 (m, 8, allylic and a-carbonyl); uv max (cyclo- hexane) 230 (e 99), 281 (a 35.6), 288 (c 33.3), and 345 nm (a 17.2); mass spectrum (70eV) m/e 138 (parent), 110 (-00), and 82 (-200). £335. Calcd for C H 0 ° C, 69.62; H, 7.30. 8 10 2' Found: C, 69.40: H, 7.16. 78 10,11-Benzo-9,12-diazabicyclo[6.4.01-4,8,10,12-dodeca- tetraene (Quinoxaline 55). 3 To a solution of 0.69 g (5 x 10' mol) of S-cyclo- octene-l,2-dione in 50 ml of glacial acetic acid was added a solution of 0.54 g (5 x 10'3 mol) of technical o-phenylenediamine in 20 ml of glacial acetic acid. The resulting solution was stirred at 60° for 12 hr. The solution was then poured into water and the resulting precipitate was filtered. This solid was recrystallized from water-methanol and then chromatographed on silicic acid eluting with chloroform. Removal of the solvent from the main chromatographic fraction provided 0.6 g (57%) of the quinoxaline as white crystals: mp 117-119°; ir (CHClS) 2975 cm‘1 (C-H); nmr (00013) 6 7.9 (AA'BB' pattern, 4, aromatic), 6 5.56 (t, J = 4 Hz, 2, olefinic), 6 3.42 (t, J = 7H2, 4, a-imino), and 6 2.74 (m, 4, allylic); mass spectrum (70eV) m/e 210 (parent). Aggl. Calcd for C H N ° C, 80.07; H, 6.72. l4 l4 2' Found: C, 79.93; H, 6.77. 79 3,8-Di(p-meth0xybenzilidene)-S-cyclooctene-l,2-dione '(Dione 55). A solution of 3.5 g (2.54 x 10' 1 2 mol) of S-cyclooctene- 1,2-dione, 14.2 g (l x 10' mol) of p-anisladehyde, and 25 drops of piperidine in 30 ml of absolute ethanol was refluxed with stirring for nine hr. Upon cooling a yellow crystalline material was obtained. This material was recrystallized from acetone giving 3.7 g (39%) of dione 55 as beautiful yellow crystals: mp l62.5-165°; ir (CHClS) 3000, 2950 (C-H) and 1675 cm'1 (C=O); nmr (00013) 6 7.9 (s, 2, olefinic), 6 7.3 (AB quartet, J = 8 Hz, AB 8, aromatic), 6 6.25 (t, 2, olefinic), 6 3.9 (s, 6, methoxy), and 6 3.38 (d, 4, allylic); uv max (cyclohexane) 208 (e 2.8 x 10'3), 233 (e 2.08 x 103), and 327 nm (e 2.18 x 103); mass spectrum (70eV) m/e 374 (parent). Anal. Calcd for C H 04: C, 77.07; H, 5.93. 24 22 Found: C, 76.96; H, 5.96. 80 truns-3,8-Dibromo-S-cyclooctene-l,Z-dione (Dibromide 85). A three neck 500 ml round bottom flask equipped with a magnetic stirrer, a gas inlet tube, and a reflux condensor was charged with 6.9 g (5 x 10‘2 mol) of 5- cyclooctene-1,2-dione, 44.6 g (0.2 mol) of cupric bromide, and 200 ml of a 1:1 ethyl acetate-chloroform solution. The mixture was stirred under nitrogen for 15 min at room temperature and then at 75° for 12 hr. Upon cooling the cuprous bromide was filtered and washed with chloro- form. The combined filtrate and wash was washed with water until neutral followed by a wash with saturated sodium chloride solution. After drying over anhydrous magnesium sulfate, the solvents were removed giving a brown solid material. Trituration with cyclohexane removed the brown material affording white crystals. Recrystallization of the crude product from methylene chloride-cyclohexane provided 5.0 g (34%) of dibromide 85, mp 136—139fi An analytical sample was obtained by sublimation: mp 138-141°; ir (CHC13) 3000, 2925 (C-H) and 1740, 1727 cm'1 (C=O); nmr (00013) 6 6.07 (m, 2, olefinic), 6 5.15 (ABX quartet, 2, CHBr), and 6 2.90 (m, 4, allylic); uv max (cyclohexane) 288 (e 244), 280 (e 302) and 224 (e 742); mass spectrum (70eV) m/e 298, 296, 294 (parent). Anal. Calcd for C H Br 0 8 8 2 2‘ Found: C, 32.71; H, 2.82. C, 32.46; H, 2.73. 81 2,7-Dibromo-10,ll-benzo-9,lZ-diazabigyclo[6.4.0]-4,8,10,12- dOdecatetraene (Quinoxaline 88). To a solution of 3.4 g (0.15 x 10-2 mol) of 3,8- dibromo-S-cyclooctene-l,Z-dione in 140 ml of glacial acetic acid was added a solution of 1.24 g (0.15 x 10.2 mol) of freshly distilled o-phenylenediamine in 40 ml of glacial acetic acid. The resulting solution was stirred at room temperature for 24 hr. The solution was poured into 500 m1 of water and extracted with four 100 ml portions of ether. The extracts were washed with water, saturated sodium bicarbonate solution, water, and saturated sodium chloride solution and then dried over anhyrous sodium sulfate. Removal of the solvent gave 3.9 g (72%) of quinoxaline 88 as a white powder, mp 177-182°. An analytical sample was prepared by sublimation: mp 180- 182°; ir (CHC13) 2975 cm'1 (C-H); nmr (CDClS) 6 8.00 (AA'BB' pattern, 4, aromatic), 6 5.93 (t, J = 9 Hz, 2, CHBr), 6 5.54 (t, J = 4 Hz, 2, olefinic), and 6 3.30 (m, 4, allylic); mass spectrum (70eV) m/e 370, 368, 366 (parent) Anal. Calcd for C H Br N 14 12 2 2‘ Found: C, 45.72; H, 3.28. C, 45.69; H, 3.29. 82 10,ll-Benzo-9,12-diazabigyclo(§,4.9]-2,4,6,8,10,12- dodeahexaene (Quinoxaline 88). 2 To a solution of 3.68 g (l x 10' mol) of quinoxaline 88 in 85 ml of dimethylsulfoxide was added a solution of 2.5 g (2 x 10'2 mol) of 1,5-diazabicyclo[4.3.0]nona-S-ene in 25 ml of dimethyl-sulfoxide and the resulting solution was stirred at room temperature for 18 hr. The reaction mixture was poured into 500 ml of water and extracted with five 100 ml portions of methylene chloride. The extracts were washed well with water and saturated sodium chloride solution and then dried over anhydrous sodium sulfate. Removal of the solvent gave 1.6 g of a red powder which was chromatographed on neutral alumina eluting with benzene. The first three 20 ml fractions which were collected consisted of a mixture of starting material and product. Subsequent fractions upon removal of the solvent provided 1.0 g (48.5%) of quinoxaline 88 as a very light yellow powder. An analytical sample was prepared by recrystallization from pentane: mp 143-145°; ir (CHC13) 6 7.94 (AA'BB' pattern, 4, aromatic), 6 6.88 (d of AB quartet, JAB = 11.5 Hz, 2, H2’ H7), 6 6.43 (coupled d of AB quartet, JBC = 1.5 Hz, 2, H H6), and 6.15 (d, 2, H 3’ 4’ H5); uv max (cyclohexane) 354 (e 3.09 x 104), 334 (8 5.15 x 103), 284 (e 4.12 x 103), 245 (e 227 x 104), and 205 nm (e 2.78 x 104); mass spectrum (70eV) m/e 206 (parent). Anal. Calcd for C H N ° C, 81.62; H, 4.89; 14 10 2' Found: C, 81.54; H, 4.84. 83 3-Bromo-2-hydroxy-2,5,7-cyclooctatrienone (Ketone 88). f2 A solution of 3.0 g (1 x 10 mol) of 3,8-dibromo- S-cyclooctene-l,2-dione in 70 ml of dry hexamethyl- phosphoric triamide was maintained at 80° with stirring for 18 hr. The yellow-red solution was poured into 500 m1 of saturated sodium chloride solution and extracted with four 100 m1 portions of cyclohexane. The extracts were washed with two 150 ml portions of water and then saturated sodium chloride solution and dried over anhydrous sodium sulfate. Removal of the solvent under reduced pressure provided 0.8 g of a red-brown semisolid which was chromatographed on silicic acid eluting with carbon tetrachloride-benzene (10:2). Fractions 6-18 (20 m1) afforded 0.325 g (15.0%) of ketone 88. Sublimation of the crude product afforded88 as white crystals: imp 101-103°; ir (CHClS) 3365 (O-H), 1662 (C=O), 1622 and 1600 cm'1 (C=C); nmr (CDClS) 6 7.86 (s, 1, hydroxyl), 6 6.64 (m, 3, H H7, H8), 6 6.73 (q, J = 8 Hz, 1, H5), 6’ and 6 3.16 (bd. m, 2, allylic); uv max (cyclohexane) 297 (e 5 x 103), 254 (e 1.27 x 104), 246 (e 1.23 x 104), 239 (e 1.04 x 104) and 198 nm (e 6.55 x 103); mass spectrum (70eV) 216, 214 (parent). Anal. Calcd for C8H BrOz: C, 44.69; H, 3.28. 7 Found: C, 44.65; H, 3.27. 84 l,2-Bis(§piro-l',3'-dioxolane)-5-gyclooctene (Bis ethylene ketal 88). A 100 ml round bottom flask equipped with a Dean—Stark trap and a reflux condensor was charged with 2.7 g (2 x 10-2 2 mol) of S-cyclooctene-l,2-dione, 2.48 g (4 x 10' mol) of ethylene glycol, 45 ml of benzene, and a catalytic amount of tosic acid. The mixture was refluxed with the separation of water for 20 hr. Upon cooling the solution was washed with two 10 m1 portions of 10% sodium hydroxide solution followed by several washes with water and then saturated sodium chloride solution. After drying over potassium carbonate, the solvent was removed under reduced pressure. The resulting yellow oil was distilled at reduced pressure giving 2.7 g (60%) of ketal 88 as a colorless oil which crystallized upon standing; bp 80° (0.1 mm); mp 66-67°; ir (CHClS) 2940 and 2870 cm'1 (C-H); nmr (CDC13) 6 5.78 (t, 2, olefinic), 6 4.02 (s, 4, ketal methylene), 6 3.98 (s, 4, ketal methylene), 6 2.22 (m, 4, allylic), and 6 1.90 (m, 4, a-ketal methylene); mass 'spectrum (70eV) m/e 226 (parent). Anal. Calcd for C H O ' C, 63.77; H, 8.03. 12 18 4' Found: C, 63.77; H, 7.96. 85 l-(2'-bromoethoxy)-2-(spiro-1',3'-dioxolane)-5-bromo-9- oxabicyclo[4.2.l]nonane (Ketal 88 or 888): 3 To a solution of 1.13 g (5 x 10- mol) of 1,2-bis- (spiro-l',3'-dioxolane)-S-cyclooctene in 10 m1 of tetra- hydrofuran was added a solution of 1.6 g (5 x 10'3 mol) of pyridinium hydrobromide perbromide in 10 ml of tetra- I hydrofuran with stirring over a period of 30 min. The pyridinium hydrobromide was filtered and the solvent removed under reduced pressure at room temperature.4 The resultant yellow oil crystallized upon cooling. Recrystallization of this material from hexane afforded 0.8 g (42%) of ketal 88 or 88 as feathery white crystals: mp 77-79°; ir (CHcls) 2900 and 2950 cm'1 (C-H); nmr (CDC13) 6 4.8-4.4 (m, l, ether bridge methine), 6 4.4-3.6 (m, 7, ketal methylene, bromomethine, and -O-CH2-CH2Br), 6 3.6-3.3 (m, 2, -O-CH2CH2Br), and 6 2.6-1.7 (m, 8, eight membered ring aliphatic). Anal. Calcd for C12H18Br204: Found: C, 37.45; H, 4.65. C, 37.34; H, 4.70. 86 3,8-Di(p-methoxybenzyl)-5-cyclooctene-l,2-dione (Dione 888). To a solution of 2.0 g (2.9 x 10'1 g -atoms) of lithium in one liter of liquid ammonia was added dropwise, 2 mol) of with stirring, a solution of 15.0 g (4 x 10- 3, 8 - di (p-methoxybenzilidene) -5-cycloctene-1 ,Z-dione in 400 ml of tetrahydrofuran over a period of 15 min. When the addition was complete 60.0 g of ammonium chloride was added in portions and the ammonia was allowed to evaporate. The residue was poured into water and extracted with four 100 ml portions of ether. The extracts were washed with water until neutral and then dried over anhydorus magnesium sulfate. Removal of the solvent gave a light yellow oil which crystallized upon standing overnight. Recrystallization of this material from petroleum ether (bp 40-60°)-methylene chloride (5:1) afforded 12.8 g (85%) of dione 888: mp 91.5-94°; ir (CHC13) 2930 (C-H) and 1705 cm'1 (C=O); nmr (CDC13) 8 7.03 (AB quartet, JAB = 8 Hz, 8, aromatic), 6 5.85 (t, 2, olefinic), 6 3.80 (s, 6, methoxy), and 6 2.0-3.4 (m, 10, allylic, benzylic, and a-carbonyl); mass spectrum (70eV) m/e 378 (parent). £231. Calcd for C O C, 76.25; H, 6.93. 24H26 4‘ Found: C, 76.06; H, 6.85. 87 3,7-Dibromo-3,S-cyclooctadiene-l,2-dione (Dione 888). ' 4 A solution of 108.7 mg (5.0 x 10- mol) of 3-bromo- 2-hydroxy-2,5,7-cycloctatrienone and a catalytic amount of benzoyl peroxide in 15 ml of carbon tetrachloride and 89.0 mg (5.0 x 10"4 mol) of N-bromosuccinimide were heated to reflux with simultaneous irradiation with a sunlamp for 30 min. The succinimide was filtered upon cooling and the solvent removed under reduced pressure. The residue was purified by preparative thin layer chromatography on silicic acid eluting with benzene- methylene chloride (10:12). ,There was obtained 125 mg (85%) of dione 888 as a yellow crystalline material. An analytical sample was obtained by sublimation: mp 106-109°; ir (CHClS) 1724, 1677 (C=O) and 1575 cm‘1 (C=C); nmr (CDC13) 6 7.68 (d, l, olefinic, HA), 6 6.55 (d of d, 1, olefinic, HB), 6 5.95 (d of d, 1, olefinic, HC), 6 5.23 (heptet, l, bromo methine, HD), 6 3.84 (d of d, l, a-carbon carbonyl, HE), and 6 3.22 (t, l, a-carbonyl, HF); uv max (cyclohexane) 299 (e 7.5 x 103), 235 (e 3.83 x 103), and 212 (8 6.47 x 103); mass spectrum (70eV) m/e 296, 294, 292 (parent). H Br 0 8 6 2 2‘ Found: C, 32.68; H, 2.11. Anal. Calcd for C C, 32.65; H, 2.04. 88 Reaction of 3,7-dibromo-3,S-cyclooctadiene-l,Z-dione 888 and triethylamine (Benzocyclobutadienoquinone 88). To a solution of 100 mg (4.65 x 10'4 mol) of 3,7- dibromo-3,5-cyclooctadiene-1,2-dione in 0.4 m1 of deuterated chloroform was added one drop of triethylamine. The solution immediately turned light brown. The nmr spectrum of the reaction mixture showed absorptions corresponding to the starting material and benzocyclobuta- dienoquinone. The ir Spectrum of the reaction mixture exhibited the carbonyl absorptions characteristic of 88. Thin layer chromatographic analysis of the reaction mixture on silicic acid eluting with chloroform demonstrated the presence of 88 as the only identifiable product. B IBLIOGRAPHY gt..- 4. \‘ LI“ 2‘...“ .. ..~ (N BIBLIOGRAPHY F. A. Kekule, Ann., 162, 77 (1872). E. Hfickel, Z.Physik, lg, 204 (1931); l;, 310 (1931). R. Breslow, J. Amer. Chem. Soc., lg, 5318 (1957). (a) R. Breslow, J. T. Groves, and C. Ryan, ibid., 83, 5048 (1967); (b) D. G. Farnum, G. Mehta, and R. S. Silberman, ihid,, 8;, 5049 (1967). R. Breslow, H. Hover, and H. W. 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Phys., 88, 11 (1959); (b) M. Karplus, J. Amer. Chem. Soc., 88, 2870 (1963). W. A. E. R. H C. R B 3167 . T. Davison, J. Chem. Soc., 2456 (1951). COpe, A. C. Haven, Jr., P. L. Ramp, and . Trumbull, J. Amer. Chem. Soc., ;8, 4867 (1952). . Woodward and R. B. Loftfield, ibid., 88, (1941). APPENDIX 101 Table IV. Mass Spectrum of 3,4-Dibromobicyclo— [4.2.0]-6-octene-7,8-dione Rel. Rel. m/e Inten- m/e Inten- sity sit; 296 1.4 82 1.3 294 2.8 81 1.7 292 1.4 80 1.3 79 15.5 268 2.5 78 100.0 266 4.8 77 17.5 264 2.5 76 62.5 75 5.5 188 0.5 74 37.8 187 4.1 73 3.3 186 0.5 185 4.1 66 2.5 65 0.9 160 0.3 64 0.8 159 2.0 63 6.3 158 0.2 62 3.3 157 2.2 61 3.3 60 2.5 134 0.3 133 0.3 54 0.6 132 0.6 53 4.4 131 0.3 52 15.6 130 0.2 51 35.9 50 38.0 121 0.6 49 8.4 119 0.8 48 10.3 117 0.5 41 0.6 107 0.6 40 1.1 106 5.2 39 17.5 105 2.7 38 13.9 104 3.0 37 10.6 36 1.4 95 0.6 93 0.6 102 Table V. Mass Spectrum of S-Cyclooctene-1,2-dione Rel Rel m/e Inten- m/e Inten- 51ty sitY 139 7.0 69 13.9 138 69.6 68 57.4 67 56.5 110 15.7 66 16.5 109 8.7 65 13.0 63 5.2 96 3.5 62 3.5 95 13.9 61 2.6 94 29.6 93 2.6 56 3.5 92 5.2 55 22.6 91 3.5 54 , 100.0 53 85.2 83 7.0 52 10.4 82 50.4 51 15.7 81 52.2 50 10.4 80 2.6 79 10.4 44 2.6 78 2.6 43 7.8 77 5.2 42 30.4 41 76.5 40 36.5 39 99.1 38 11.3 37 4.4 32 4.4 103 Table VI. Mass Spectrum of trans-3,8-dibromo-5- cyclooctene-1,2-dione Rel. Rel. Rel. m/e Inten- m/e Inten- m/e Inten- sity. ;§;ty, sit; 298 1.2 127 3.1 69 5 4 296 2.3 123 1.2 68 20.4 294 1.2 122 2.3 67 62.3 121 3.5 66 62 3 218 1.5 120 3.9 65 28.1 217 8.5 119 3.9 64 2.7 216 1.9 118 3.9 63 8.5 215 8.5 62 4.2 110 4.2 61 2.3 190 1.5 109 21.2 189 11.2 107 21.9 57 5.4 188 1.9 107 30.4 56 5.0 187 11.5 106 1.9 55 36.5 105 5.4 54 17.7 162 2.3 104 2.3 53 41.5 161 5.4 52 20.8 160 2.3 96 3.1 51 26.2 159 5.4 95 8.1 50 17.3 94 32.3 49 3.1 148 1.2 93 3.1 147 3.1 92 2.7 44 2.7 146 1.2 91 5.4 43 7.7 145 3.1 90 2.3 42 7.3 89 1.9 41 36.5 138 8.9 40 20.4 137 15.8 85 3.5 39 21.2 136 14.2 84 2.3 38 11.5 135 14.6 83 3.1 37 4.6 82 18.9 36 7.3 134 3.1 81 45.0 35 1.5 133 1.5 80 42.3 132 2.7 79 100 0 78 13.9 77 44.2 76 3.1 75 1.9 74 3.1 73 1.2 104 Table VII. Mass Spectrum of 10,11-benzo-9,12-diaza- bicyclo[6.4.0]-2,4,6,8,10,12-dodecahexaene. IRel. Rel. ' m/e Inten- m/e Inten- sity sit; 207 4.2 91 2.1 206 27.5 90 7.3 205 39.4 89 9.8 88 6.2 180 7.3 87 4.7 179 8.3 86 1.6 178 4.2 177 3.1 79 3.1 78 31.1 154 2.1 77 39.9 153 3.1 76 60.1 152 4.7 75 44.6 140 2.1 74 23.8 73 2.1 130 1.6 129 5.7 66 2.1 128 3.1 65 5.7 127 4.2 64 19.7 126 2.1 63 37.8 62 17.6 116 2.1 61 6.7 115 2.6 114 2.6 53 6.2 113 1.6 52 43.0 51 71.5 104 4.2 50 100.0 103 13.5 49 3.7 102 22.8 101 7.3 43 11.4 100 4.2 42 4.2 99 3.7 41 12.9 98 2.6 40 7.8 39 61.2 38 31.1 37 16.1 32 12.9 105 Table VIII. Mass Spectrum of 3-bromo-2—hydroxy- 2,5,7-cyclooctatrienone on 40 pan 01 N N _Re1. Rel. m/e Inten- m/e Inten- sity_, sitx 217 1. 67 2.6 216 13. 66 6.1 215 1 65 18.3 214 13 64 7.8 63 13.9 188 2 62 7.0 187 0. 61 4.4 186 2 185 0 57 3.5 56 3.5 174 93 55 12.2 172 100 54 2.6 53 24.4 136 4 52 20.0 135 16 51 40.0 134 2 50 21.7 49 3.5 108 4 44 18.3 107 37 43 7.8 8.7 6.1 4.4 3.5 9.1 8.7 8.7 7.8 0.9 H O U" H 4:. O O 0 O O C O C O O O O C O O O O O O O O O O O O . #MMOOMN#WNONWH4§O\ (DH->4:- O‘U’l-h DO 0000‘ 50\IO\I 4:. H 106 Table IX. Mass Spectrum of 3,7-dibromo-3,5- cyclooctadiene-l,Z-dione. Rel. Rel. Rel m/e Inten- m/e Inten- m/e Inten- s;ty s;tx sit; 296 0.06 147 1.3 85 0.6 294 0.12 146 0.9 84 0.3 292 0.06 145 7.6 83 0.4 144 0.8 82 35.6 266 0.1 143 6.9 81 15.5 254 0.2 141 0.5 80 36.5 252 0.3 136 1.3 79 2.3 250 0.2 135 7.0 78 86.3 134 25.0 77 100.0 220 0.3 133 4.5 76 16.3 217 0.5 132 0.9 75 6.0 216 4.8 131 0.6 74 8.5 215 8.4 130 0.4 73 3.0 214 5.9 129 0.3 213 8.3 128 0.5 66 3.0 212 1.1 127 0.3 65 11.3 122 0.5 64 9.0 198 0.6 119 2.5 63 17.5 196 0.5 118 0.7 62 7.8 194 0.4 117 2.4 61 4.8 189 0.3 116 0.4 56 4.0 188 2.8 115 0.4 55 6.8 187 14.1 54 1.8 186 8.1 109 1.0 53 16.9 185 5.3 108 1.5 52 25.3 107 13.1 50 36.3 175 2.1 106 9.9 49 12.5 174 22.6 105 15.6 44 6.2 173 5.4 104 0.5 43 0.9 172 21.7 103 0.5 42 7.5 171 3.8 102 0.3 41 3.0 170 0.3 101 0.2 40 9.8 169 0.3 39 36.2 168 0.3 95 9.4 38 25.0 167 0.3 94 1.7 37 12.5 166 0.5 93 3.6 36 1.7 165 0.9 92 5.0 32 75.0 160 0.8 91 1.3 159 8.5 90 1.4 158 5.0 89 3.1 157 8.8 88 0.4 156 4.5 87 0.6 155 6.3 86 0.7 107 2.5 -' "- 3.0 3.5 410 M1930”? 5.0 6.0 8.0 80 40 TRANSMITTANCE (7'3) 20 2000. 3500 3000 2500 2000 1500 ” moueau 1cm) 5.0 i 6.0 7.0 8.0 M'CRONS 10.0 11.0 12.0 18.0 100 -- ' " ‘ -; f; " 1;:u " ”710° -, 1 edits q. A ' 80 80 60 60 A O TRANSMITTANCE (~73) O .'..’ ; ; ... . . .1'1 : ' 2000 1800 1600 1400 I200 moo ucv 1m"; 1000 800 Figure 1. Infrared spectrum of 3,4-dibromobicyc1o- [4.2.0]-6-octene-7,8-dione 88 (CHCIS) 108 2.5 ' 3.0 3.5 4.0 M‘CRONS 5:0 6.0 3 8.0 . 1 . , . . 100 80 80 0 O 60 :3. O 40 1RAN5MHTANCE(%) u » Q - a- - ... . 4 -, .-.. . . 1 . . . . - .. - . . - ,- .:. . . . . - . - . . ‘ . , . . . . . . .. 1 . . o 1 . . . . . .. .1 . . ._ . 9 u . - . 3 u 1 . . . . . 20 _. ..... _.. _ .. . . . _. 20 . . . . -. 1 . . ..... . 1- . . u . . o 4 I . I . 1.- . . . ‘... . . . 1 . . . . . . . . . 1 l . 1. . . , . ., ' I 1 . , . . 1 u . ...... _ . ,. -. _.. 1 . .-..- . .1 V -g...--_...-——. ------- 01°1::.,._ ‘3 4000 3500 3000 2500 2000 1500 FREQUEVCI (CM ‘) 5.0 « 6.0 7.0 8.0 M'CRONS 10.0 11.0120 _ 18.0 100 . 3. , O) O .-.1 O O TRANSMHTANCE(%) h C) i 8.-.-.. 20 -i: 3 3 -'§ 3'3 3 3 3 3 333 3.3 s 3 3.333320 —-g .o- .. _.. . . . .. '. ' ' ‘ ' 1 . 1 1 ....... otdz. 3' 3-1331 3.:.. 33 :1 .s’ 2000 1800 1600 1400 1200 1000 800 FREOU£N4 Y (CM') Figure 2. Infrared spectrum of 5-cyc1ooctene- l,2-dione 88 (CHC13) TRANSMITTANCE (7'5) TRANSMITTANCE (‘11) 109 MICRONS 40 3500 3000 2500 2000 1500 a. mauuaa (can) 30 7 MICRONS 1800 1600 1400 1200 1000 800 l” IIEOUINO (04" 1 _ Figure 3. Infrared spectrum of trans-3,8-dibromo- S-cyclooctene-1,2-dione 88 (CHC13) 110 2.5 1 3‘ 3.0 3.5 4.0 M'CRONS 5.0 8.0 3 8.0 100 100 1 I . . ~ ...—.-u I u—_.--.—— l..."- TRANSMITTANCE (7.3) 0 3'3 7 1-. 3' 3 '3 ‘ I f . 3'33.- 3... '33- '33 L. ". .3: .' :. 3 .3' '.". '17"? 3' ' 3 . 3.’ 7'3. ."_ I . '.. v o 4000 3500 3000 2500 . 2000 1500 IREOUE‘I’ LY (CM'U 5.0 ' 8.0 7.0 8.0 M'CRONS 10.0 11.0 12.0 . 18.0 100 ' ‘ ~' ‘ ‘ ‘ ' ‘ 100 ¢_. _... 80 60 3340 TRANSMITTANCE (76) t. O 20 ' - . 1 1400 1200 "mun-1c v 1am -4 H 1800 .1.-. 1000 800 1600 V n- '2'. 0 2000 Figure 4. Infrared spectrum of 10,11-benzo-9,12- diazabicyclo[6.4.0]-2,4,6,8,10,12- dodecahexaene 88 (CHC13) 111 I _- MICRONS 40 TRANSMHTANCE(%) 3500 3000 2500 2000 1500 "EQUINC‘ I CM" 1 MICRONS TRANSMITTAI ICE (%) 1800 1600 1400 1200 1000 800 rascal \{Y (CM '1 Figure 5. Infrared spectrum of 3-bromo-2-hydroxy- 2,5,7-cyclooctatrienone 88 (CHC13) 112 MICRONS LU U 2 < )— '2 31 z 40 < :5 . 3500 3000 2500 2000 1500 0.- d.- FREQUENC' (on; 50 'I _ 7 MICRONS “ 80 Lu 2 L < E 5 U7 2 < a ’— 1600 1400 1200 1000 800 FREOUE 4C" 1“" 1 1800 .1 I. Figure 6. Infrared Spectrum of 3,7-dibromo-3,5- cyclooctadiene—1,2-dione 888 (CHClS) s 4 ' 7‘. Hfl'fivjrr'jlt'vv VjWOIV'IT vvvavvvvlvvrrrv rvrrv v v Ii v v Viv—V‘Vi‘v I VrT V—‘V‘Vfiv I v frr‘fiY v vi I v ‘j‘rf 77f rfi l v Br 49 1" 1 '4... “Wm rum-7'48: wHWL-MWJQJL'V VMWM 1.-.- ---l-...-11.1.11-114111..11#--11 ....... . . ' I I I I I ‘A‘ LAAA LJAA ALLA AL‘L AJAA AAA+ A‘AJIAAJA A 0.0 1.0 on 0.0 man I}! 4.0 u 2.0 u q ,__f_! Figure 7. Nmr spectrum of 3,4-dibromobicyclo[4.2.0]- 6-octene-7,8-dione 88 (CDC13) nuns-m A “COAL Y I V V I V r T 1 Ti V 1" V I T T V I I Y T V V T V l T V V I I I f 1—1 f ‘ '7 1' - I V V ' Y—T *5 l 1' T r fl Y -T j - I 0 V r l' V r T i W I no on no no II. on m —- -“aa-m——— .1 1 1.31;. 1- 8 A .1. 1 ;J 3 z 3 t t 3:5— '1.‘ Figure 8. Nmr spectrum of 5-cy c1ooctene-l, 2- dione 88 (00013) 114 L l A A L A A I A A A l A A A j in. M l " . “I... i ' ' A A Figure 9. .fiur Specrrum 6f £rans-3,8-dibromo-S- cyclooctene-1,2-dione g; (CDClS) «mun _*7L “CUM A r V V I I 1 r I ' I V V j I "r j V I Y I V ' l r 7" I T r‘ r f fir o ' I r j I 'f ' I j I ' I ' f 1 SN 40. M 3.. m 0* H. / \ 1 1.. g. :1‘ if fil '1‘}! 1'1 1 I I 4 L A 1 L L ’ A 4 1 A9 A.‘ A A l L A A J ' A A A n i A A L A ' L t L L 0.0 n u 3.. _Jn « . u u . u 6 Figure 10. Nmr spectrum of 10,11-benzo-9,12-diazabicyclo [6.4.0]-2,4,6,8,10,12-dodecahexaene ég (CDC13) 115 2:13." 1 )1 r"T‘~"'J jfi‘f 'firl ' ]' Iiv J' 'fj_'_'—T—' fi""1*'. Ir Afi*ujt*. 11""."v‘1 an .1 3. ON I. OH In» 1 I 1 E ‘ 1 1 1. i i E 1 NJ “M“ l. .'- .4.A'..A.l ...L....JL-AAL.;.-1-..A.LA.I .14...IA...1. 1L.ALIA-AAE....LA_A_A.IA-..r. " '* “ 9.:nvutf . “ .mg‘ . ." ' Figure 11. Nmr spectrum of S-bromo-Z-hydroxy- 2,5,7-cyclooctatrienone gé (CDC13) mm H ' ”nu—“m” 'lm—u cc, ,-.. .l.. ..l. -.., . gL.. .Tfi I r'f‘ ' I f'c"‘ 1 Tfil'fl' I ' It. 4“ 3“ I“ ' I . L l . l 1 . . l A A A A - l A A . A ‘ A A A A A A 1 A A A A A A . A A . I A A L A 1 L A A A l A A A A l A A A A; 1 AL A A P l I A A A; l A A A L I A AA. A A I A A A A M 7.. u M NICO! M ‘I' u u 0 .0“. . . Figure 12. Nmr spectrum cf 3-bromoeiehydroxy- 2,5,7-cyclooctatrienone 2g (DMSO-d6) 116 Figure 13. Nmr spectrum of 3,7-dibromo-3,S- cyclooctadiene-1,2-dione $£§ (CDC13) mm A F l 1' J U '1‘ fl l FYT'VI ‘7 4‘ I, u mfi l‘ f.' j l '- ‘I .1 ' ft; m 0. O. I“ Ch D-I’ 4 l i: .5 I h !i la . r-E v: '3 E ;' . I PF M‘ i 3'5 1. I t“: '1 ‘ ll! 1 . l ’5: it w 1 ' I y H . afiVV ~\M " 1. .L 'iiilA.i+'...1.LL..l..=...1. —I ;IAA LIAILAIAAQI‘; AIALALIIA¥AAI:LLALI u u u “....mr-1'3'....‘.'.. . u “m“? . . u ' o 1. III [Ill-nil IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII ummmmnuunmmmuwwmn 3 1293