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I THESIS [Immaunllzlllllllllll‘lllllllull 1 93 01778 9821 LIBRARY Michigan State University This is to certify that the dissertation entitled Syntheses of Conjugated Oligomers and Macrocycles Containing Thiophene, Pyrrole, Furan, 1,3,4—Thiadiazole and ThiazoloIS,4-d]thiazole presented by Seaver Shieh has been accepted towards fulfillment of the requirements for Ph.D Chemistry degree in Date 0?] Md/(I /?Z:7 MSU is an Affirmative Action/Equal Opportunity Institution 0—12771 PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINE return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 1/98 cICiRCIDdeDmpes-p.“ Syntheses of Conjugated Oligomers and Macrocycles Containing Thiophene, Pyrrole, Furan, 1,3,4-Thiadiazole and Thiazolo[5,4-d]thiazole By Seaver Shieh A Dissertation Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1997 ABSTRACT Synthesis of Conjugated Oligomers and Macrocycles Containing Thiophene, Pyrrole, Furan, 1,3,4-Thiadiazole and Thiazolo[5,4-d]thiazole By Seaver Shieh Study of the structural influences of conducting polymers is one of the most important research in this area. Because conducting polymers containing carbon-nitrogen double bonds in the conduction pathway still have not thoroughly been explored36 and study on this aspect can provide information on the heteroatom (nitrogen) influence on the properties of the conductive polymers, preparation of conductive polymers and Oligomers with C=N bond in the conductive main chain have been studied and discussed in this thesis. Several new mixed Oligomers which contain thiophene, furan, pyrrole, 1,3,4-thiadiazole and thiazolo[4,5-d]thiazole have been synthesized and some spectroscopic properties have been studied. The results show that 1,3,4-thiadiazole increases the bandgaps because of the electron withdrawing properties of this heterocycle. Thiazolo[4,5-d]thiazole decreases the bandgaps because of the bigger conjugation property of the n-electrons in it. In the course of synthesis of mixed thiophene Oligomers containing l,3,4~thiadiazole an efficient and practical method for the preparation of 2,5-diaryl-1,3,4-thiadiazoles in one pot has been developed. The value of this reaction has been shown by the syntheses of a variety of 2,5-diaryl-1,3,4-thiadiazoles with high yield ( >90% yield for most reactions). By using this method, 2,5-di(4- hydroxylphenyl)-1,3,4-thiadiazole and 2,5-dipyridyl-l,3,4- thiadiazoles have been synthesized in one pot with high yield. The traditional syntheses of these two kinds of compounds usually require several steps and use expensive reagents42'43. 1,4-Diketones are important intermediate compounds for the syntheses of thiophenes, pyrroles, furans and other heterocycles. In the search for a good method for the preparation of 1,4-diketones, oxidative coupling of trimethylsilyl enol ethers with Cerie Ammonium Nitrate(CAN) has been shown to be a practical method for the syntheses of 3,4-dialkyl-l,4-(2-thienyl)-l,4-butanediones. VOClg/Pyridine has been found to be a good oxidative reagent for the oxidative coupling of trimethylsilyl enol ethers to 1,4-diketones. By using VOCl3/Pyridine as an oxidation reagent the reaction time is shorter compared to that with CAN. In the approaches of syntheses of conjugated macrocycles a hexathiophene macrocycle has been synthesized with low yield (1.5%). The formation of this compound was confirmed by mass spectrum, 1H-NMR and UV-Vis. The results show that there is only a little aromatic property of this compound, which is inconsistent with that predicted by Huckel rule and MM2 calculation. Further research in the structure of this compound is necessary. This thesis is dedicated with love to my Father, Shu-Lin Xie and my Mother, Qiao-Ying Chi To my wife, Lillian H. Shieh for her love, support and understanding ACKNOWLEDGEMENTS The author is greatly indebted to Professor Eugene LeGoff, for his patience and guidance during the course of research. Under his guidance, my studies and research in Michigan State University have been always fun and exciting. I am also indebted to Professor Chi Kwong Chang for his supports and encouragement in a variety ways during the research. Thanks also go to Professor Mercouri Kanatzidis and Dr. Chengang Wang for collaboration in the studies of soluble conductive polymers. Thanks also go to Professor Kim Dunbar for her many valuable suggestions during my second year oral examination. I would like to thank Drs. Evaldo DeArmas, Bryon Anderson Merril and Michael Benz and Weishi Wu. Dr. Evaldo DeArmas helped me for some electrochemical studies of conductive polymers. Dr. Bryon Anderson Merril gave me valuable introduction to his research work at MSU. Drs. Michael Benz Weishi Wu provided varieties of helps including Laboratory techniques, supplies and valuable discussions. I also would like to thank Michael Waldo for his help in many aspects. It is he who make the work environment much more fun and I enjoyed working with him here. Special thanks go to my wife, Lillian Shieh, and my son, Peyton Shieh, for their understanding and endless supports. Thanks go to the Chemistry Department and Center for Fundamental Materials Research at Michigan State University for financial supports in the forms of Teaching and Research Assistantships. vi TABLE OF CONTENT page List of Figures ................................................ ix List of Schemes .............. . ..................... . .......... xii Introduction ................................................. 1 Chapter 1 Synthesis of Tricyclic Compounds as Monomers for the Synthesis of Some New Conductive Polymers 7 1.1 Attempt at the Synthesis of a Phenylene Bridged Tricycle .......... 7 1.2 Syntheses of 2,5-diaryl-thiazolo- [5,4-d]thiazole 16 1.3 Syntheses of Tricyclic Compounds Containning 1,3,4-Thiadiazole ............. 24 1.4 Syntheses of 3,4-Dialkyl-2,5-di(2-thienyl) thiophenes, Pyrroles and Furans 37 1.4.1 Synthesis of 3,4-Dialkyl-2,5—di(2-thienyl) thiophene by Grignard Coupling Reaction 40 1.4.2 Syntheses of 3,4-Dialkyl-2,5-di(2-thienyl) thiophenes, Pyrroles and Furans by the 1,4-Diketone Route ........ . 44 1.4.2.1 Synthesis of 3,4-Dibutyl-1,4-(2-Thienyl)- 1,4-Butanedione by the Oxidative Coupling of Dimethylsilyl Bis-enol Ether .................. 45 1.4.2.2 1.4.2.3 1.4.2.4 Chapter 2 Chapter 3 3.1 3.2 3.3 3.4 viii Synthesis of 3,4-Dialkyl-l,4-(2-Thienyl)- 1,4-Butanedionc by the Oxidative Coupling of Trimethylsilyl Enol Ethers With Ceric Ammonium Nitrate(CAN) ......................... 48 Synthesis of 3,4-Dialkyl-l,4-(2-Thienyl)- 1,4-Butanedione by the Oxidative Coupling of Trimethylsilyl Enol Ethers With VOCl3/Pyridine ........ ....... 52 Synthesis of 3,4-Dialkyl-2,5-di(2-thienyl) thiophenes, Pyrroles and Furans .................. 55 Syntheses And Spectroscopic Studies of The Thiophenc and Mixed Thiophenc Oligomers ......................................... 60 Synthetic Approaches of Some New Conjugated Macrocyclic Compounds ......... 73 Synthetic Approaches of A New Tetrapyrrolic Macrocyclc Containing 1,3,4-Thiadiazole ..... 94 Synthesis of A New Hexathiophene Macrocyclc Containingl,3,4-thiadiazol ...... 101 Synthetic Approaches of A New Hexathiophcne Macrocyclc .. ..................... 106 Synthesis of A New Hexathiophene Macrocyclic Compound ....................................... 112 Conclusions ..... ix Experimental Sections ......................................... List of References Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 2-1 2-2 3-1 3-2 3-3 3-4 [26]Porphyrin[3,3,3,3) LIST OF FIGURES Structures of Some Conducting Polymers Band Structures of Conducting Polymers ...... Structures of Metalloporphyrin and Metallophthalocyanines . . . . . . . . Two Conjugated Monomers With C=N Dond Structure of Thiazolo[5,4-d]thiazole Resonance Structure of 2-Formyl Pyrrole .. Cyclic Voltamgram of 2,5-Di(2-thienyl) thiazolo[5,4-d]thiazole Structure of 1,3,4-Thiadiazole Structure of Dimethyl Chlorosilyl Mono-enol Ether 0..O.I.000......OOOOOOOOOOOOOIOOOOOOOOO0.. Some Thiophenc Oligomers Containing 1,3,4- thiadiazole and Thiazolo[5,4—dlthiazole .. ...... Some Thiophenc Oligomers The Change of Resonce Energy with The Number of n-Electrons Structure of Turcasarin Structure of Metalloporphyrins and Phthalocyamines Structure of [1,3,1,3]Platyrin, [1,5,1,5]Platyrin [22]Porphyrin(],3,1,3) and Page 17 21 23 25 47 61 62 74 75 77 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 3-10 3-11 3-12 3-13 3-14 3-15 xi Structure of [34]Porphyrin(5,5,5,5) and Porphocyanine Structure of Footballene Structure of Porphyrin(2,1,0,1), Pentaphyrin, Sapphyrin, Thiasapphyrin, Dioxasapphyrin and Oxasapphyrin Structure of Hexaphyrin, Rubyrin and Rosarin Structure of Porphycene, Bridged Porphycene, [22]Porphyrin(2,2,2,2), Porphyrinoids, [26]Porphyrin(6,0,6,0), and Acetylene-Cumulene Heterocyclic Expanded Porphycenes 115, 116 Structure of Tetraethylporphyrin, Corrole, Isocorrole and Their Expanded Compounds Structure of Some Furan and Thiophenc Analogs of Porphyrins and Their Expanded Compounds Structure of Some Other Conjugated Macrocycles Structures of 1,3,4-Thiadiazole Expanded Porphyrins Space-filling Structures of 1,3,4-Thiadiazole Expanded Porphyrins Structure of 1,3,4-Thiadiazole Expanded Hexathiophene Macrocyclc ....... . ............ 82 84 85 87 92 94 95 102 Figure Figure Figure Figure 3-16 3-17 3-18 3-19 xii Space-filling Structures of 1,3,4-Thiadiazole Expanded Hexathiophene Macrocyclc ......... 95 Space-filling Structures of An Expanded Hexathiophene Macrocyclc ................... 107 Space-filling Structures of Another Expanded Hexathiophene Macrocyclc ................... 108 Space-filling Structures of Another Expanded Hexathiophene Macrocyclc ................... 112 Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme I-l 1-1 1-2 1-3 1-9 1-10 LIST OF SCHEMES Structure of Some p-Doped Comducting Polymers Structures of A Multidimension Conjugated Polymers Synthesis of Phenylene Diamine Bridged Tricyclic Compounds Synthesis of 1,2,5-Triphenylpyrrole Proposed Miller and Ploechel Reaction to Synthesize Phenylene Diamine Bridged Tricyclic Compounds ..... . . . ..... . . . ...... . ..... Synthesis of N,N'-Dicyano(2-thienyl)methyl Phenylene Diamine ..... . . . . . ..... . .......... Miller and Ploechel Reaction .......... . ....... Reaction Mechanism of Miller and Ploechel Reaction . ............................. . ....... A Synthetic Method to Synthesize New Conducting Polymers ....................... Synthesis of Polymers Containing Thiazolo- [5,4-d]thiazole Synthesis of 2,5-Di(2-thienyl)thiazolo- [5,4-d]thiazole xiii Page 8 11 13 13 l4 l6 l8 Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme 1-10.1 1-11 1-12 1-13 1-14 1-15 1-16 l-17 1-18 1-19 1-20 1-21 1-22 1-23 xiv Fragmentation of 2,5-Di(2-thienyl)thiazolo- [5,4-d]thiazole Under High Energy Electron Impact ......................................... Synthesis of 2,5-Di(2-pyrryl)thiazolo- [5,4-d]thiazole ............... Synthesis of Conduting Polymers Containing 1,3,4-thiadiazole Synthesis of 2,5-Diaryl-1,3,4-thiadiazoles ...... Synthesis of 2-Alkyl-5~(4-hydroxylphenyl)- 1,3,4-thiadiazolc . ..... ......... . ........... Synthesis of 2,5-Dipyridyl-1,3,4-thiadiazole Another Synthesis of 2,5-Diaryl-l,3,4- thiadiazoles Synthesis of 2,5-Di(2-thienyl)-1,3,4- thiadiazole Reaction Machanism for Synthesis of 2,5- Di(2-thienyl)-l ,3,4-thiadiazole ............... Synthesis of 2,5-Di(2-furry1)-1,3,4- thiadiazole ........... . ..... . ................. Attempt Synthesis of 2,5-Di(2-pyrryl)- 1,3,4-thiadiazole ......... . . . . . . . . ............ Synthesis of 2,5-Di(2-pyrryl)—l,3,4- thiadiazole Synthesis of 2,5-di(6-methyl-2-pyridyl)- 1,3,4’thiadia2016 0.0000000000000000 Synthesis of 2,5-di(4-hydroxylphenyl)- 1,3,4-thiadiazole 20 22 26 29 29 32 33 35 Scheme 1-24 Scheme 1-25 Scheme 1-26 Scheme 1-27 Scheme 1-28 Scheme 1-29 Scheme 1-30 Scheme 1-31 Scheme 1-32 Scheme 1-33 Scheme 1-34 Scheme 1-35 Scheme 1-36 Scheme 1-37 Scheme 1-38 XV Synthesis of 2,5-diphenyl-l,3,4-thiadiazole 36 Polymerization of 3-Alkylthiophene ............ 38 Polymerization of 3,4-Dialkythiophene .......... 39 Polymerization of 3,3'-Dialkyl-2,2'-bithienyl 39 Polymerization of 3,4-Dialkyl-2,5— bis(2-thienyl) Thiophenc ...................... 39 Synthesis of 3,4-Dibutyl-2,5-bis(2-thienyl) Thiophenc ....................................... 41 Synthesis of 3,4-Dibutyl Thiophenc ............. 41 Synthesis of 2,5-Dibromo-3,4-dibutyl Thiophenc ...................................... 42 Synthesis of 3,4-Dibutyl-2,5-bis(2-thienyl) Thiophenc with Grignard Coupling .............. 43 Synthesis of 3,4-Dibutyl-2,5-bis(2-thienyl) Thiophene, Pyrrole and Funan .................. 45 Synthesis of 2,3-Dibuty1-l,4-bis(2-thienyl) Butanedione ....................... ...... 46 Synthesis of 2,3-Dibutyl-1,4-bis(2-thienyl) Butanedione .................................... 49 Reaction Mechanism of Oxidative Coupling of Trimethylsilyl Enol Ether with CAN ........... 49 Synthesis of 2,3-Dialkyl—1,4-bis(2-thicnyl) Butanedione ................................... 50 Attempt Synthesis of 1,4-Di(2-pyrryl)-1,4- butanedione ................................... 51 Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme Scheme 1-39 1-40 1-41 1-42 1-43 2-1 2-2 2-3 xvi Synthesis of 2,3-Dialkyl-l,4-bis(2-thienyl) Butanedione By Oxidative Coupling of Trimethylsilyl Enol Ether with VOC13 ......... Synthesis of 1,4-Di(2-pyrryl)-1,4- butanedione ................................... Synthesis of 3,4-Dialkyl-2,5-bis(2-thienyl) Thiophenes . ..................................... Synthesis of 3,4-Dialkyl-2,5-bis(2-thienyl) Pyrroles ............. ............ Synthesis of 3,4-Dialkyl-2,5-bis(2-thienyl) Furans ...................................... Synthesis of Quinquethiophene and its Pyrrole Synthesis of 1,4-Bis(5-(3',4'-dibutyl-2,2',5'2"- terthienyl))-1,4-butanedione By Friedel-Crafts and Furan Analogs Synthesis of l,4-Bis(5-(3',4'-dibutyl-2,2',5'2"- Acylation .OOOOOOOOOOOOOOO terthienyl))-l,4—butanedione By Stetter's Reaction Synthesis of 3',3""',4',4"'"-Tctrabutyl-2,2',5',2", 5",2'",5"',2"",5"",2""',5""',2"""-quinqucthiophenc Synthesis of 2,5-Bis(5-(3',4'-dibutyl-2,2',5'2"- terthienyl))pyrrole Synthesis of 2,5-Bis(5-(3',4'-dibutyl-2,2',5'2"- terthienyl))furan 52 56 58 59 63 64 65 66 xvii Scheme 2-7 Synthesis of 2,5-Bis(5-(3',4'-dibutyl-2,2',5'2"- terthienyl))-1,3 ,4-thiadiazole .................. 70 Scheme 2-8 Synthesis of 2,5-Bis(5-(3',4'-dibutyl-2,2',5'2"- terthienyl))thiazolo[5,4-b]thiazole ' ............. 71 Scheme 3-1 A Retrosynthetic Analysis of Macrocyclc 140 ........ ........... 96 Scheme 3-2 A Proposed Method for the Synthesis of Macrocyclc 142 ................. 97 Scheme 3-3 Synthesis of 5,5'-Diformyl-2,2'- dipyrrylmethane .............. . ..... . . . . ...... 98 Scheme 3-4 Attempt Synthesis of Macrocyclc 142 98 Scheme 3-5 A Proposed Synthesis of Macrocyclc 150 ..... 99 Scheme 3-6 Synthesis of 5,5'—Diformyl-3,3'4,4'- tetramethyl-2,2'-dipyrrylmethane . . . . . . . . . . . 100 Scheme 3-7 Attempt Synthesis of Macrocyclc 150 101 Scheme 3-8 A Proposed Synthesis of Macrocyclc 154 104 Scheme 3-9 A Synthesis 5,5"-bisformyl-3'4'-dibutyl- 2,2',5',2"-terthiophene 104 Scheme 3-10 Another Synthesis 5,5"-bisformyl-3'4'- dibutyl-2,2',5',2"—terthiophene ............... 105 Scheme 3-11 Synthesis of Macrocyclc 154 ................ 105 Scheme 3-12 A Retrosynthetic Analysis of Macrocyclic Diketone Compound 159 109 Scheme 3-13 A Proposed Synthesis of Macrocyclc 159 110 Scheme 3-14 A Synthesis of 5,5"-Bisacetyl-3',4'-dibutyl-2,2', 5 ',2"-terthiophene ............................ 1 10 Scheme Scheme Scheme Scheme Scheme Scheme Scheme 3-15 3-16 3-17 3-18 3-19 3-20 3-21 xviii Condensation Reaction of 5,5"-bisformyl- 3'4'-dibutyl—2,2',5',2"-terthiophene with 5,5"-Bisacetyl-3',4'-dibutyl-2,2',5',2"- terthiophene ................................ Reaction of 5,5"-bisformyl-3'4'-dibutyl- 2,2',5',2"-terthiophene with Ammonium Salts .......................................... Self Condensation of 5,5'-bis(aminomethyl) dipyrrylmethane ............................. A Proposed Method to Synthesize Macrocyclc 166 .......................................... Synthesis of 5,5"-bis(aminomethyl)-3'4'- dibutyl-2,2',5',2"-terthiophene .. ............. Synthesis of Macrocycle 165 ................. Synthesis of Macrocyclc 166 ................. 111 114 115 117 117 Syntheses of Conjugated Oligomers and Macrocycles Containing Thiophene, Pyrrole, Furan, 1,3,4-Thiadiazole and Thiazolo[5,4-d]thiazole INTRODUCTION Since the 1970's a number of special polymers have been found which exhibit electrical conductivity when they are submitted to oxidation or reduction. These kinds of special materials are called conducting polymers. They are new materials with many potential 1-4 applications , such as rechargeable polymer batterys'é, electrochromic displays”, antistatic and transparent conducting 10.11 material9, chemical sensors , memory devices”, polymer based diodes and transistors13'15 . The common feature of conducting polymers is that they are structurally conjugated. Some conducting polymer structures are shown in Figure I-l. Neutral conjugated organic polymers can not conduct electricity because of the lack of electrical carriers. In order to become a conductor or semiconductor, it is necessary to introduce charge carriers into neutral polymers. These typical processes are called doping. Generally, there are two methods to introduce charge Figure H W polyecetylene “nil-i- POlenIIIn. / \ X / pclypyrrcle, pclythlcphen X \ I X and pclyturan X: NH, 8, 0 carriers. One is to take off one or more electrons from the neutral polymers by oxidation, which introduces positive charges in the polymers. This process is called p-doping. The other is to introduce negative charges by the addition of electrons (reduction), which is described as n-doping. Scheme 1-1 shows some p-dopcd conducting polymer structures. Although there has been much progress in the research of conducting polymers, the conductive mechanism is still unclear. Generally, in analogy to inorganic conductors or semiconductors, band theory is utilized to explain the conductive mechanisms. In a conjugated polymer, the highest occupied electronic orbitals constitute the valence band (VB) and the lowest unoccupied orbitals form the conduction band (CB). The width between the VB and CB is called the bandgap(Eg). The intrinsic conductivity of an organic conducting polymer is determined by the bandgap. Neutral Scheme I-l Neutral One polaron Two polarons One bipolarcn x= NH, 8, O; R: H, AIkyl groups etc conjugated polymers are intrinsically insulators because of large bandgaps. The result of doping lowers the bandgap so as to increase the electrical conductivity”. The band structures of neutral and doped conductive polymers are shown in Figure I-2. Polyacetylene is the first and most electrically conductive polymer reported so far. Its conductivity has been reported as high Figure I-2 CB bandgap |< .S I sHI .Vrll sill sill a ~ N E The bandgap of neutral conjugated polymers 9' F The bandgap of one polaron c. The bandgap of two polarons P- The bandgap of one bipolaron e. The bandgap of doped conductive polymers as 160008/cm per unit weigh”. However, its applications have been limited by its low stability and poor processing properties. In contrast, polypyrrole, polythiophene, polyfuran and some other polyheteroaromatic compounds show reasonable electrical conductivity and high stability”. Another advantage of polyheteroaromatic compounds over polyacetylene is the ease of modifying the polymer chains to achieve the processing requirement by simple substitutions. Many conductive polymers, soluble in both organic solvent and water, have been synthesized in this way19‘24. Generally speaking, the knowledge of the relationship between the chemical structures of monomers and the electrical properties of the resulting polymers is important both in the understanding of electrical conduction mechanisms of conductive polymers and in the preparation of new kinds of conductive polymers. Although there has been lots of progress in understanding the monomer structural influences on the conductivity and other properties of the corresponding polymers, the reported results so far are not enough to understand the conductive mechanisms or functions of some heteroatoms e.g. sulfur and nitrogen in the conductivity or other properties of polyheteroaromatic systems. If we consider polyacetylene as a basic conjugated system, polypyrrole, polythiophene and polyfuran can be rationalized as NH, S, and O functionalized polyacetylene derivatives. Structural modifications are commonly used strategies in the study of monomer structural influences on the properties of the resulting polymers. For the polyheteroaromatic systems there are two ways to modify the conductive polymer structures. One is to synthesize heteroaromatic monomers with different substituents and then study the substituent influences on the properties of resulting polymers. The other is to synthesize monomers with special structures so that the resulting polymers will have different main chain structures. By this way, the relationship of the monomer structures with the properties of the conducting polymers can be easily studied. Conducting polymers synthesized from 3- and/or 4- alkyl substituted pyrroles, thiophenes and furans belong to the first kind but polyisothianaphthene (PITP)25, polythieno[3,2- b]thiophene(PTT)26, etc. can be considered as the second. Considering that studies on the influences of the main chain structures on the properties of the conducting polymers are less than those on the side chain influences, the syntheses of new structural monomers and oligomers is one of the goals in my Ph.D. thesis research. In Chapter 1 and 2 of this thesis the syntheses of some new conjugated oligomers containing thiophene, pyrrole, furan, 1,3,4-thiadiazole and thiazolo[5,4-d]thiazole will be presented. Conjugated macrocyclic compounds are other kinds of organic conductors with the metalloporphyrins and metallophthalocyanines )27. as two common compounds for this purpose (Figure I-3 Figure 1-3 The basic requirement for these kinds of organic conductors is that the constituent molecules must be essentially planar. The planar structure allows them to stack close enough to be a conductor or semiconductor. This basic requirement allows chemists to design and synthesize new macrocyclic compounds which are structurally planar or nearly planar and then study the molecular size effects on the conductivity and other properties. Expanded porphyrins are one of these kinds of macrocyclic compounds. In Chapter 3 of this thesis the attempted syntheses of some new conjugated macrocyclic compounds will be presented and discussed. Chapter 1 Syntheses of Some Tricyclic Compounds as Monomers for the Syntheses of New Conductive Polymers 1.1 Attempt at the Synthesis of a Phenylene Bridged Tricycle Although there are lots of reports on the monomer structure influences on electrical properties of the conductive polymers27'30, research on the study of structural influences of the properties of conductive polymers is still an interesting area, and there is still lot of work to be done in understanding the relationship of monomer structures and the electrical conductivity. Generally, polypyrrole, polythiophene, polyfuran and some other polyheteroaromatic compounds can form linear, one- dimensional chains. Monomers with three or more reactive positions can form conductive polymers with multi-dimensions. Scheme 1-1 shows one of the possible multi-dimension conductive polymers. Preparation and electrical property studies of multi- dimensional conductive polymers are important both in the understanding of conductive mechanisms and in the exploration of new kinds of conductive polymers. The heteroaromatic tricycles with a phenylene bridge have been suggested31 as monomers of multi-dimensional conductive polymers (Scheme 1-1). Scheme 1-1 /\ X /\ e /\ x /\ x \/ x x \/ x n 1 2 one-dimension X/\X ”E?” /\N/\ X\IX 3 I\NI\ X\IX 4 multi—dimensions The synthesis of symmetric heteroaromatic tricycles with a phenylene bridge has been achieved by Merrill in this laboratory by using Stetter's reaction to prepare the correspondent 1,4-diketones and then condensed with p-phenylene diamine (Scheme 1-2)“. Scheme 1-2 IX \ IX \ I \ [LO—Di... Mom 5a-c 6a-c \ xI \N I \ XI 3a-c a, X=NH; b, X=S; c, X=O a. thiazolium salt (cat.), Et3N, divinyl sulfone, dioxane, 80 °C b. phenylene diamine, HOAc, reflux Although the above route seems to be a good one to the synthesis of this kind of system there still are some problems which have to be solved. First, the electrically rich property of pyrrole ring makes Stetter's reaction not good for the unsubstituted 2-formyl pyrrole”. When unsubstituted 2-formyl pyrrole is used protection with an electron withdrawing group is necessary. Second, although condensation of the 1,4-diketone with phenylene diamine in two steps gave moderate yield of the expected p-phenylene bridged tricyclic compound 3, one step condensation resulted in very low yield“. Third, Stetter's reaction requires expensive reagents such as divinyl sulfone and only symmetric monomers can be synthesized in this method. Therefore, to find another route for the synthesis of compound 3 is still necessary. Miller and Ploechel” in 1898 reported that the addition of anilinophenylacetonitrile(7)(Ar1=Ph) to cinnamaldehyde(8) yields 10 1,2,5- triphenylpyrrole (9)(Ar1=Ph, Arz, Ar4=Ph, R=H) (Scheme 1-3). A similar reaction has also been reported by Clark and Lapworth33. Further research and the applications of this reaction has been demonstrated by Treibs and Dam“. Scheme 1-3 As an application of the Miller-Ploechel reaction, the following project has been proposed (Scheme 1-4). Starting with 2-acetyl derivatives of thiophene, furan or pyrrole and using Mannich reaction followed by treating with bases the unsaturated ketones(12) can be synthesized (reaction 1 in Scheme 1-4). Synthesis of the corresponding aminonitriles(l3) can be achieved by the condensations of the 2-formyl thiophene, furan or pyrrole with hydrogen cyanide and p-phenylene diamine (reaction 2 in Scheme 1- 4). If the Miller-Ploechel reaction can be utilized in this system the reaction of the unsaturated ketones(12) with the aminonitrile(l3) will lead to the expected compound 3 (reaction 3 in Scheme 14). 11 Scheme 1-4 CH 0 O 3 conc.HCI 1. / \ 1 \NH.HCI + I/ W #- X1 CH3/‘ 0V0 95% ethanOI 1 0 / \ 0 base / \ 0 x1 N:.HCI 7 X1 1 1 1 2 CN "“2 OH-U / X2 C—j HN x2 NH2 HI! x2 5 CH CN 1 3 °“ .0 0.0.0 | HNCH X2 X1 N X2 0 base 3. Mi ‘ x x N x “New 0-0-0 1 2 CN 1 3 3 X1,X2=NH,S,O While this research work was being conducted, we thought that one would want to know whether the Miller-Ploechel reaction is a 12 reliable reaction, and whether it can be applied to this system. As a model reaction the aminonitrile 13 with X=S has been synthesized and reacted it with acrolein in the reported standard condition. The reasons for choosing it as a model reaction are: (1). The thiophene ring is relatively more stable than pyrrole and furan. (2). Conducting polymers synthesized from thiophene derivatives show higher conductivity than those from pyrrole or furan analogs. (3) Acrolein has been reported as a good reagent for the Miller-Ploechel reaction. Unknown compound 15 was the expected product in this model synthesis. Compound 13b(X2=S) has been synthesized by the condensation of 2-formyl thiophene, NaCN, AcOH, p-phenylene diamine in ethanol with 90% yield (Scheme 1-5). When compound 13b reacted with acrolein in the reported reaction condition, it had been found that the imine compound 16 was the only isolated product. This result indicates that before the Miller-Ploechel reaction occurs the aminonitrile loses two molecules of hydrogen cyanide in the basic reaction conditions (Scheme 1-6). Considering the reaction mechanism of the Miller-Ploechel reaction (Scheme 1-7) and this unexpected result we thought that Miller-Ploechel reaction might not be a general reaction as it is difficult to apply to the synthesis of compound 3. Because of the unsuccessful application of the Miller~Ploechel reaction to the synthesis of compound 15 further research on above project has not been attempted. Research has been guided to the 13 syntheses of new kinds of conductive polymers which contain C=N double bonds or other heterocycles aside from pyrroles, thiophenes and furans in the conductive pathway. Scheme 1-5 Scheme 1-6 base -HCN 14 Scheme 1-7 2 H 2 H 2 An, H—CN Ar H-CN Ar H—CN ——b- 0 ——-b- H A Ar4Cl-=CH—(g—R At, P-I—Cl-hg—R Art H-CH=8-R 13- 2 "‘ E. A. .311. Considering that conducting polymers containing carbon- nitrogen double bond in the conduction pathway still have not thoroughly been studied36 and study on the conductive polymers containing C=N double bond might provide information on the heteroatom (nitrogen) influence on the properties of the conductive polymers, preparation of conductive polymers with C=N double bond in the conductive main chain is necessary. In order to synthesize conductive polymers with C=N double bond in the conduction pathway, monomers 16, 17 (Figure 1-1) are the simplest candidates. 15 Monomers 16 and 17 with X=S have been prepared by the reaction of 2-formyl thiophene with p-phenylene diamine and hydrazine in benzene in the presence of HCl catalyst (best yield can be obtained when pH value is controlled between 5 and 6). Unfortunately when they are submitted to the electrical polymerization monomers 16 and 17 do not polymerize in normal electrical polymerization conditions. Chemical polymerization by FeCl3 in dried CH2C12 also fails to synthesize conductive polymers by using the imine compounds 16 and 17 as monomers. Generally, electrically inactive monomers are difficult to polymerize by using common chemical oxidation methods and the reactivity of C=N double bonds with Grignard reagents excludes the possibility of using a Grignard coupling reaction to synthesize the conjugated polymers with these imine monomers. No further attempts have been made to synthesize conductive polymers from these imine monomers and research was immediately turned to other kinds of monomers which contain C=N double bond or other heterocyclic compounds in the conductive polymer main chains. Monomers 16 and 17 contain two pyrrole, thiophene or furan rings at the ends and the middle parts are structurally different fragments. It was thought that if the middle parts are modified in a 16 proper way, many monomers with different structures can be synthesized and electrical or chemical polymerization of these monomers will lead to many new kinds of conductive polymers. In this way the structural influences of the monomers on the properties of the resulted conductive polymers can be easily studied. Following this strategy and considering the chemical reactivity of monomers l6 and 17, we think that one of the choices for the middle parts is to incorporate a special heterocyclic compound between two pyrroles, thiophenes or furans. Scheme 1-8 shows this strategy. Scheme 1-8 \ etero I \ “M /x x /x\ t. x X: NH, S,O With this strategy in hand the next step was to choose which heterocyclic compounds were to be used. The guideline is to choose a heterocyclic compound which contains special groups or atoms whose importance to the conductivity are to be studied. In the following sections, how this strategy has been used for the synthesis of some tricyclic compounds as candidates for the syntheses of new conductive polymers and higher oligomers will be presented. 1.2 Syntheses of 2,5-Diaryl-thiazolo[5,4-d]thiazoles Thiazolo[5,4-d]thiazole(20) is an aromatic compound with 10 n-electrons. The chemical structure of thiazolo[5,4-d]thiazole is isoelectronic with that of naphthalene and that of thieno[3,2-b] thiophene (Figure 1-2). Figure 1-2 s N s (I) (I) s / s N 18 19 2 0 Naphthalene Thieno[3,2-b]thiophene Thiazolo[5,4--d]thiazole Thiazolo[S,4-d]thiazole(20) is thought to be a good candidate as a heterocyclic compound for the incorporation in the thiophene oligomers because of its structural similarity to thieno[3,2- b]thiophene(l9) and it contains two C=N double bonds. Syntheses and studies of conjugated oligomers or polymers containing thiazolo[5,4-d] thiazole may provide some information on the influence of a nitrogen atom or a C=N double bond on the properties of conductive polymers. From literature, it was known that thiazolo[5,4-d]thiazole itself can not polymerize electrochemically”. Lithiation of thiazolo[5,4- d]thiazole followed by oxidation with CuClz gave a completely disordered polymer”. In our opinion, it is difficult to use this 17 18 homopolymerization result to study the influence of structure on the properties of conductive polymers. As an attempt to study the influence of thiazolo[5,4-djthiazole on the properties of the thiophene based oligomers or polymers one part of my research was to synthesize some tricyclic compounds which contain thiazolo[5,4-d]thiazole, and then use these tricyclic compounds as monomers for the syntheses of new conductive polymers (Scheme 1-9). Compounds 21b and 21c are known but 21a is an unknown compound. All the expected polymers 22a, 22b and 22c are new. Scheme 1-9 S S WEI/+0 ——-> 4.3% ’ZIHQW. 21a-c 22a-c a, X=NH; b, X=S; c, X=O Compounds 21b and 21c have been prepared by the condensation of 2-formyl thiophene and 2-formyl furan with dithiooximide via the reported procedure (Scheme 1-10)37'38. Condensation of 2-formyl thiophene with dithiooximide in the absence of solvent at 170 °C gave 41% yield of 2,5-di(2- thienyl)thiazolo[5,4-d]thiazole 21b. Similarly, reaction of 2-formyl furan with dithiooximide gave 2,5-di(2-furanyl)thiazolo[5,4- dlthiazole 21c in 37% yield (Scheme 1-10). However, the reaction of 2-formy1 pyrrole with dithiooximide in the same condition fails to 19 give the expected product, 2,5-dipyrryl thiazolo[5,4-dlthiazole, 21a (Scheme 1-10). Scheme 1-10 NH2 neat/170°C Q—CHo+ 8: >Q4Nl 8H8 \) H2N s 41% SIN 5b 2 3 21 b 8 Mia neat/170°C Um + I i M" ;I >42) 0 H2N s 37% 5c 23 2% Mia neat/1760 UCHO + S: w (/ \H/NIS) [I \) H2N S a S NI 3 58 2 3 2 13 Changing reaction condition by using DMF as solvent does not improve the yield of 2,5-di(2-thienyl)thiazolo[5,4-d]thiazole 21b and 2,5-di(2-furanyl)thiazolo[5,4-d]thiazole 210. It also failed to give any isolated yield of 2,5-dipyrry1 thiazolo[5,4-dlthiazole, 21a. The failure of the condensation of 2-formyl pyrrole with dithiooximide might be attributed to the most electronically rich character of 2-formyl pyrrole among these three 2-formyl compounds which makes 20 it unstable. Another reason for this failure might be attributed to the hydrogen in the 1-position of 2-formyl pyrrole. The resonance hybrid structure39 difficult (Figure 1-3). of 2-formyl pyrrole make the condensation Figure 1-3 The structures of 21b and 21c confirmed by lH--NMR, mass spectra, UV-Vis spectra and other spectroscopies. For example, the three sets of doublet doublet peaks with chemical shift of 7.58 ( J=4.1, 1.0Hz), 7.47(J=5.4, 1.0Hz) and 7.12ppm (J=5.4, 4.1Hz) shows the characteristic of the pattern of a-monosubstituted thiophene. EI-mass spectra shows a strong molecular ion peak at mlz=306 (relatively intensity 61.4) which is in support of the structure of 21b. The base-line at m/z=88 corresponds to the structure of CZSZ“ which is consistent with the loss of two a-cyanothiophene (Scheme 1-10.1). The UV-Vis maximum absorption at 388nm shows a bathochromic shift of about 30nm of tit-terthiophene, another indication of extended conjugated structure of 21b. 21 Scheme 1-10.1 / N S -e N s + (94‘ Him—Q ——+[Q—<5Wl 2&0,“ + s=c=c=s+ s m/z-=88 In order to synthesize 2,5-di(2-pyrryl)thiazolo[5,4- d]thiazole(21a) it is necessary to protect the pyrrole ring with an electron withdrawing group. Reaction of 2-formyl pyrrole with ClSOzPh in CH2C12 with the presence of NaOH gave the expected 2- formyl-l-phenylsulfonyl pyrrole(25) in 91% yield. Condensation of 2-formyl-l~phenylsulfony1 pyrrole(25) dithiooximide in DMF lead to the formation of the expected 2,5-di(1-phenylsulfonyl-2-pyrryl) 'thiazolo[5,4-d]thiazole(26) in 25% yield. Hydrolysis of 2,5-di(l- phenylsulfonyl-2-pyrryl)thiazolo[5,4-d]thiazole(26) with NaOH in refluxing EtOH for 8 hours gave a 72% yield of the 2,5-di(2- pyrryl)thiazolo[5,4-d]thiazole(21a) (Scheme 1-11). 22 Scheme 1-11 b / N S Q—CHO _8.. [3.0m _. WSINW 26 H 302% SOzPh 302% 24 25 c / N S (ii—(SI? it) 2 1a a) PhSOzCl(1.1 eq). NaOH, CH2C12/I-120, rt, 24hrs, 91%; b) DMF, 150 °C, 40min, 25%; c) NaOH, EtOH, reflux, 8hrs, 72%. Chemical polymerization of 2,5-di(2-thienyl)thiazolo[5,4-d] thiazole with FeCl3 in CH2C12 fails to give a high molecular weight polymer. The resultant products are orange colored low molecular weight oligomers. The molecular weight were determined by end- group of Hl-NMR with about 3,000 to 6,000. UV-Vis spectra show a maximum absorption at 497nm. When monomers 21b & c were submitted to electrical polymerization they polymerize easily under normal conditions. Figure 1-4 shows the cyclic voltamgram result of 21c. 23 Figure 1-4 EXP. CONDITIONS. INIT IIIVI" 300 HIGH £(IIIV1- $700 LON EIMV) " 300 V (nil/8801' 800 SNEEP SEGMENTI- I 88191. INT.(MV1" 8 10M 1 I J +0.200 From Figure 1-4 the oxidation peak covers a broad range centered at about 1.53V which corresponds to the oxidation potential of the monomer, the formed oligomers or the polymer. This low oxidation potential indicates monomer 21b might be a good candidate for the synthesis of new conducting polymer 22b and could be used as a component for copolymerization with other monomers e.g. pyrrole, thiophene, etc. The UV-absorption of 2,5-di(2-thienyl)thiazolo[5,4-d]thiazole has been determined and compared with that of a -terthienyl. The results are presented in Table 1-1. These results show that the heterocycle thiazolo[4,5-dlthiazole cause a bathochromic shift of about 30nm for the rt-zr“ absorption band (Table 1-1). Similar results are obtained for the furan and pyrrole oligomers systems (Table 1- 1). 24 Table 1-1 Structures UV-Vis(nm) Structures UV-Vis(nm) mm) 356 M 0Q mmb) 333 M 0‘29) 35‘ Q 0% @(21c) 380 mm“ 360 Q @Q 0(21a) 39‘ Q. If we compare these results with the p-phenyl analogs40, the long wavelength absorption band means that the conjugated polymers containing thiazolo[4,5-d]thiazole will have a lower bandgap. 1.3 Syntheses of Tricyclic Compounds Containing 1,3,4-Thiadiazole 1,3,4-Thiadiazole(32) is a heterocyclic compound with 6 n-electrons. It is structurally similar to the thiophene and thiazole except that it contains two nitrogen atoms. The structural similarity of thiophene, thiazole and 1,3,4-thiadiazole are shown in Figure 1-5. 25 Figure 1-5 8 S S t /7 t I f I N N—N 3 0 3 1 3 2 Thiophenc Thiazole 1 ,3 ,4-thiadiazole In a study of the influence of heterocyclic compounds on the properties of polythiophene, polypyrrole and polyfuran we thought that the incorporation of 1,3,4-thiadiazole into the thiophene, pyrrole or furan oligomers or polymers may provide some information on the influence of the nitrogen atom on the properties of these systems. For example, if we use the tricyclic compounds 2,5-di(2- thienyl)-1,3,4-thiadiazole, 2,5-di(2-pyrryl)-l,3,4-thiadiazole or 2,5- di(2-furryl)-1,3,4-thiadiazloe as a monomers, chemical or electrochemical polymerization of these monomers will give polymers containing 1,3,4-thiadiazole. Study of these polymers and comparison with the homopolypyrrole, polythiophene or polyfuran will give us an understanding of the influence of 1,3,4-thiadiazole to the properties of polypyrrole, polythiophene or polyfuran. Scheme 1-12 N-N N’N (2)4942) ———-> WSW—h X: NR, 8, 0, Te, etc 26 Based on this consideration, a part of my research has been involved in the syntheses and property studies of tricyclic compounds which contains a 1,3,4-thiadiazole. A common route to the syntheses of 2,5-diaryl-l,3,4- thiadiazoles is the reaction of a precursor hydrazide with P28 5 or Lawesson's reagent4l(Scheme 1-13). Scheme 1-13 0 0 Xylene N-N II II Ar—C-NH—NH-C—Ar + P235 W ”—48%” Although this route is classical and has been used to synthesize many 1,3,4-thiadiazole derivatives, the precursor hydrazides are not common reagents and sometimes must be synthesized via several steps. For example, the syntheses of arylhydrazides containing hydroxyl, amino or other functional groups which can react with acyl chlorides generally need protection of the functional groups. Protection and deprotection increase the number of reaction steps. For instance, 2,5-di(4-hydroxylphenyl)-1,3,4-thiadiazole is an important precursor for the syntheses of liquid crystals or biological active compounds. The synthesis of the hydrazide requires the protection of hydroxyl group42 (Scheme 1-14). Another example of the difficulty of the syntheses of 2,5- diaryl-l,3,4-thiadiazoles by the route of using hydrazides as the precursors is the syntheses of 2,5-dipyridyl-1,3,4-thiadiazoles. The 27 reactivity of pyridine with acyl chlorides make this route impractical. Scheme 1-15 shows a patented route to the synthesis of 2,5- dipyridyl-l,3,4-thiadiazole43. Scheme 1-144 2 o O . . O O R'—6-NHNH2 + Cl-g—Q—OOCCZHS Pyridine Rba-NHNHZO—Q—Ooccsz (3 9 (4 Q P285 (4 1) -N 1) KOH,H20,MeOH N-N Fr__£ls»_—<>_OH : 2) W R4SL—©_mCCZH5 (4 3i (4 2 a) R'=C10H21: b) 0C9H19 Scheme 1-1543 (43) (44) (45) i PhMe,SOC12 H 5W / \ If — H’s , \ 93' 0 _ — s \ x” QWTT—Q SaLaqKOH (47) (46) l [0] ’ \ / \ —' (48) Reaction of an aromatic aldehyde with hydrazine and elemental sulfur is another route for the synthesis of 2,5-diaryl-1,3,4- thiadiazole (Scheme 1-16). As we know, aldehydes, hydrazine and sulfur are all common and inexpensive reagents, and this one-pot procedure make it a promising route to the syntheses of 2,5-diaryl substituted 1,3,4-thiadiazoles. Although it has been claimed that this method has been used for the syntheses of some 2,5-diaryl-1,3,4- thiadiazoles“, in our hand, the reported procedure45 is only good for the syntheses of 2,5-dialky1-l,3,4-thiadiazoles. There is no published procedure to synthesize 2,5-diaryl-1,3,4-thiadiazoles by the reaction of aromatic aldehydes, hydrazine and sulfur. 29 Scheme 1 -16 N-N R—CHO + N2H4 + S —> R—(SS—R Use of a similar procedure and reaction condition to the condensation of thiophene 2-carboxylaldehyde, hydrazine monohydrate and two equivalent sulfur at 90 °C for 24 hours failed to give the expected 2,5-di(2-thienyl)-1,3,4-thiadiazole. The major product isolated is the imine compound with a less than 10% yield of the 2,5-di(2-thienyl)-l,3,4-thiadiazole. This unexpected result indicates that the reaction condition might be too mild. Increase of the temperature to 110-130 °C and extension of the reaction time to two days in the presence of a high boiling amine (e.g, tributylamine) and an excess sulfur (four or more equivalents) allow the reaction to go smoothly. For example, reaction of thiophene 2-carboxylaldehyde, hydrazine monohydrate and excess sulfur (6 equivalents) in propylene glycol at 130 °C for 2 days in the presence of tributylamine gave 2,5-di(2-thienyl)-l,3,4-thiadiazole in a 90% yield (Scheme 1-17). Scheme 1-17 o C H O N-N W +N2H4-H20 +S(excess) 3 8 2 , WSW H 130°C, 2 days 3 90% ( 3 3 ) 30 This procedure provides a convenient synthesis of 2,5-di(2- thienyl)-1,3,4-thiadiazole. Although the details of the reaction mechanisms are not known, one of the possible mechanisms is shown in Scheme 1-18. Reaction of the thiophene 2-carboxaldehyde with hydrazine forms the imine product. Reduction of sulfur with hydrazine give to the formation of hydrogen sulfide which then reacts with amine to form hydrogen sulfide anion. Nucleophilic addition of the hydrogen sulfide anion with the imine to form the intermediate imine thiol which then cyclizes to form the tetrahydro-l,3,4-thiadiazole derivative. Oxidation of the tetrahydro-l,3,4-thiadiazole by sulfur lead to the formation of the expected 2,5-di(2-thienyl)-l,3,4- thiadiazole (Scheme 1-18). Scheme 1-18 [1 .. _ I” QCHO N2H4 S H’C-N-N-CD 28 + N2H4 —> 2H23 + N2 H28 + NBU3 ——> HS- + HN+BU3 H28 Q4LQ <— QSHI ,H s s ”PW-'3? s \ / ls / \ M / \ S S 8 As an extension of this procedure, the syntheses of 2,5-di(2- pyrryl)-1,3,4-thiadiazole and 2,5-di(2-furry1)-1,3,4-thiadiazoles by the condensation of the correspondent carboxaldehydes with hydrazine monohydrate and elemental sulfur have been attempted. Condensation of 2-furan carboxaldehyde with hydrazine monohydrate and excess elemental sulfur in propylene glycol at 130 °C for two days gave only a very low yield (about 3%) after several trials. Extension of reaction time to five days gave only intractable materials. Shortening the reaction time to one day gave a 5% of product and 12% of the imine intermediate. Decreasing the temperature to 110 °C and lengthening the reaction time to five days gave 15% of the isolated 2,5-di(2-furryl)-1,3,4-thiadiazole (Scheme 1-19). Further attempts to improve the product yield by changing the reaction conditions (e.g. temperature, reaction time and the ratio of reagents) did not succeed. 32 Scheme 1-19 CaHeoz <;)~< + N H -H O + S(excess) .. U l \ U 2 4 2 130°C, 2 days 0 ° 3% (34) 03 H ”O + N2H4- H20 + S(excess) —3—-—2> Intractable Products 130°C 5 days C H O + N2H4-H20 + S(excess) iii» U U U 130°C ' ° 24hr 5‘70 4. U _ . O (35) m 12% 4 H + N2H4-H20 4. S(excess) wwwu 110°C. 5days 0 1 °. 5/ (34) The condensation of 2-formylpyrrole or 2-formy1-1-methyl- pyrrole with hydrazine monohydrate and elemental sulfur at 130 °C for two days or at 110 °C for five days both failed to give 2,5-di(2- pyrry1)-1,3,4-thiadiazole or 2,5-di(l-methyl-2-pyrryl)-1,3,4- thiadiazole (Scheme 1-20). 33 Scheme 1-20 H o @‘ctim N2H4-i-l20 + S(excesé) 41%;» ms )—O F3 110 c 5 days (36) c H o N‘ [Lem-t N2H4-H20 + S(excess) 3433» 048 m 130 °C 9 2 days R (36) R a, R=H; b, R=Methyl The differences of the condensation reactions of 2-formyl pyrrole and 2-formyl furan from that of the thiophene analog may be attributed either to the electron richer characters of pyrrole and furan rings which reduce the reactivity of the corresponding aldehydes, imines and other relative derivatives to form the expected thiadiazoles or to the instability of pyrrole and furan derivatives which make the side reactions (e.g. oxidation, ring opening etc.) more competitive. In order to overcome the above difficulties and explore the possibility of the above reaction for the synthesis of 2,5-di(2-pyrryl)-1,3,4-thiadiazole protection of the pyrrole l-nitrogen with an electron withdrawing group has been investigated. 34 Condensation of 2-formyl-phenylsulfonepyrrole with hydrazine monohydrate and excess sulfur gave the expected product, 2,5-di(1- phenylsulfone-Z-pyrryl)-1,3,4-thiadiazole(38) in 61% yield. Base hydrolysis of 2,5-di(1-phenylsulfone-Z-pyrryl)-1,3,4-thiadiazole(38) gave the 2,5-di(2-pyrryl)-1,3,4-thiadiazole in 89% yield (Scheme 1- 21). The generality of this synthesis of 2,5-diaryl-1,3,4-thiadiazoles has also been investigated by the use of different arylaldehydes. For example, reaction of 4-pyridinecarboxaldehyde or 6-methyl-2- pyridinecarboxaldehyde with hydrazine monohydrate and elemental sulfur gave good yield of the correspondent 2,5-di(4-pyridyl)-l,3,4- thiadiazole and 2,5-di(6-methyl-2-pyridyl)-l,3,4-thiadiazole (Scheme 1-22). Scheme 1-21 N-N WCHO+ N2H4-H20 + S(BXCGSS) Cal-.802 / \ I m ’ 'i‘ 120°C N S [:1 (3R7) 2days.61% R (38) a NaOH/EtOH reflux, 5 hrs R=802Ph 89% N-N / \ / 3 Z] y '2‘ S r}: H H 35 Scheme 1-22 _. Propylene glycol __ N-N NQ—CHO'I- N2H4H20+ S > N / l \ / \N (excess) 130 °C, BuaN \ 3 ~— (44) 2 days, 76%) (48) __ Propylene glycol _ N-N \ I CHO+ N2H4H20 + S b \ I i \ / \ M N (excess) 130 °C, BuaN N 3 N- e 2 days, 82% M9 M9 (49) (so) Some other 2,5-diaryl-1,3,4-thiadiazoles have also been synthesized by the condensation of the correspondent aryl aldehydes with hydrazine monohydrate and elemental sulfur. Scheme 1-23 shows some of the results. Scheme 1-23 Propylene glycol . (excess) 130 °C, BuaN S (51) 2 ”a” (52) Aldehydes Yield ( isolated thiadiazoles °/c ) a, R = H 83% b, R = OCH3 84% c, R = OH 79% 36 Scheme 1-24 ethylene glycol Al'_‘€HO + N2H4 . H20 4' S O > AF-‘Q—fi' (excess) 130 C, BU3N 2 days Aldehydes Yield of Thiadiazoles Q—cno ' 71% @4310 66% CHsG-Q—CHO 60% The solvent effect has also been investigated briefly. Generally, an alcoholic solvent is necessary. The low boiling point alcohols, e.g. methanol, ethanol or propanol are not very good solvents because the cyclization reaction requires high temperature. The use of high boiling solvent, e.g. DMF, DMSO, etc. gave a very low yield of product (IO-20%). Change of solvent from propylene glycol to ethylene glycol results in a slightly lower yield of products. Scheme 1-24 shows some of the results. The low yield of product in ethylene glycol may be attributed to the lower solubility of the starting aldehydes, the 37 intermediate imines and the products in ethylene glycol than those in propylene glycol. The above results indicate that the condensation of arylaldehydes with hydrazine monohydrate and elemental sulfur is a general, efficient and most convenient route to the syntheses of 2,5- diaryl-l,3,4-thiadiazoles. The value of this reaction has been shown by the high yield of the syntheses of 2,5-dipyridyl-l,3,4-thiadiazoles, which can not been synthesized by the classical route or need several steps by a patented route. Propylene glycol is a good solvent for this reaction. 1.4 Synthesis of 3,4-Dialkyl-2,5-di(2-thienyl) Thiophenes, Pyrroles and Furans Although polythiophene, polypyrrole and polyfuran are good organic conductors, their B-unsubstituted polymers show low solubility in common organic solvents. The low solubility of B-unsubstituted thiophene, pyrrole and furan results in the low processibility so as to limit their applications. In order to improve the solubility and processibility of polythiophene, polypyrrole and polyfuran, generally, C4-C13 alkyl substitution in the 3- and/or 4- positions of the thiophene46‘48, 5° rings has been used as monomers. Poly-3- pyrrole49 or furan alkylthiophenes are the most common soluble and processible conductive polymers. Although poly-3-alkylthiophene can improve 38 the solubility and processibility to some extent the polymerization of 3-alkylthiophene may occur in head to head, head to tail or tail to tail manners. The resulting poly-3-alkylthiophenes are complicated mixtures (Scheme 1-25). The lack of regularity of the alkyl substituents in poly-3-alkylthiophene make it difficult to study the structural influences on the properties of correspondent conducting polymers. Scheme 1--2547 1' RMgBr/Ether Pdldppplmz' FGCI3/CH2CI2 In order to solve the regularity and solubility problems of polythiophene, several other monomers have been used. For example, the use of 3,4-dialkylthiophene as monomer can lead to the formation of a regular polythiophene (Scheme 1-26). However, the steric effects of the bulky alkyl groups reduce the conjugation of the polymers so as to reduce the conductivity“. 39 Scheme 1-265' The use of 3,3'-dialkyl-2,2'-bithienyl as a monomer can also lead to the formation of regular polythiophenes. However, synthesis of the monomer generally require several steps52 (Scheme 1-27). Scheme 1-2752 B n n n s s s s " Another method of solving the solubility and regularity problems is the use of 3,4-dialkyl-2,5-di(2-thienyl) thiophene as monomer which has been synthesized by Dr. Michael Benz in our laboratory53'54. Scheme 1-2854 an R n /\/\/\ m3, /\/ /\ s s s s s s" 40 Because 3,4-dialkyl-2,5-di(2-thienyl) thiophene, pyrrole and furan are good monomers for the syntheses of soluble and regular conducting polymers and can be also used as precursors for the construction of some new polythiophene macrocyclic compounds a reliable and practical route to the syntheses of these compounds has to be developed. A part of my research has been involved in this and the results are presented in the following sections. 1.4.1 Synthesis of 3,4-Dialkyl-2,5-di(2—thienyl) thiophene by Grignard Coupling Reaction One of the obvious route to the synthesis of 3,4-dialkyl-2,S- di(2-thienyl)thiophene is the use of a Grignard's coupling reaction as a key step. This route has been described by Michael Benzs3 as a good route to the synthesis of 3,4-dibutyl-2,5-di(2-thienyl)thiophene (Scheme 1-29). 41 Scheme 1-295 3 Br 3, “904 cm Ni(dPPP)C12 / \ 2 BngC H9 / \ 2 s S + 4 EM ZS S (5 a (5 ‘9 lBI‘z/CHzClg H904 c4H9 Bng—Q (5 0 H9O‘ C4H9 / \ / \ I \ r . err—Zia, S S S Nl(dppp)C12 S Ether (5 7) (5 5 Grignard coupling of 3,4-dibromothiophene with n-butyl magnesium bromide in anhydrous ether at room temperature with the catalysis of [1,3-di(diphenylphosphino)propane]Ni(II) chloride (Ni(dppp)C12) gave good yield of 3,4-dibutylthiophene (Scheme 1- 30). This result is consistent with the reported result”. Scheme 1-30 Br Br H904 C4H9 N. 2/ § + 2 BngC4H9 "mm” » 2/ \S S Ether, n. 12 hrs S 68-84% (53) (54) 42 Bromination of 3,4-dibutylthiophene with bromine in CH2C12 gave a good yield of 2,5-dibromo-3,4-dibutyl-thiophene (Scheme 1- 31). Scheme 1-31 H9C4 C4H9 B H9C4 C4H9 Z/ ( —'2——» Z/ \S 0.1 C Br Br 8 9120/:2 S (5 4) (5 5 Grignard coupling of 2,5-dibromo-3,4-dibutyl-thiophene with 2-thienyl magnesium bromide by the catalysis of Ni(dppp)C12 in ether at room temperature for 24 hours gave a 21% yield of 3,4- dibutyl-2,5-di(2-thienyl)thiophene(57) and 35% of the monocoupling product 2-bromo-3,4-dibutyl-5-(2- thienyl)thiophene(58). Lengthen the reaction time to 72 hours to give 58% yield of 3,4-dibutyl-2,5-di(2-thienyl)thiophene and 6% of 2-bromo-3,4-dibutyl-5-(2-thienyl)thiophene (Scheme 1-32). It is difficult to eliminate the formation of 2-bromo-3,4-dibutyl-5-(2— thienyl)thiophene. This result shows some difference from that reported by M. Benz”. Scheme 1-32 H904 C4H9 Br ‘U— Br S (55) 43 B'MO—Q (5 6 ) H9C‘ C4He H964 04He [/§ 2/ \S [I \ +Br—Zl—m Ni(dppp)C12 S S S S S Ether,rt,24hr (57) (58) 21 0/0 350/0 BrMo—O (56) ”9° C4Hs W + arm Ni(dppp)C12 Ether,rt,72hr (57) (58) 58% 6% The formation of the monocoupling product 2-bromo-3,4- dibutyl-S-(2-thienyl)thiophene(58) indicates that the coupling of 2,5-dibromo-3,4-dibutyl-thiophene with 2-thienyl magnesium bromide is a step-wise reaction and the second-step of the coupling reaction is a slow reaction. 1.4.2 Synthesis of 3,4-Dialkyl-2,5-di(2-thienyl)thiophenes, Pyrroles and Furans by the 1,4-Diketone Route 1,4-Diketones are versatile intermediates for the syntheses of thiophenes, pyrroles, furans and many other heterocyclic compounds. Although many synthetic routes have been reported for the syntheses of 1,4-diketones4‘5‘50 , one of the most promising routes is the oxidative coupling of ketones. Oxidative coupling of ketone enolates with Cu2+ and other transition metal ions5 1'52 has been reported and has become one of the most useful methods. However, the syntheses of 1,4-diketones from ketones by oxidative coupling of silyl enol ether usually can provide more reliable results and lead to a good yield of 1,4-diketones. So far, Ce“, Cu2+, Pb(OAc)4 and hypervalent iodide53’56 have been reported as good oxidants for this purpose. Recently, a new procedure for the syntheses of 1,4- diketones by the treatment of silyl enol ether with VO(OEt)C12 in dichloromethane has also been reported”. In Sections 1.4.2.1-3 the syntheses of 3,4-dialkyl-1,4-(2-thienyl)-1,4-butanediones will be presented and the results will be discussed. 44 1.4.2.1 Synthesis of 3,4-Dibutyl-l,4-(2-Thienyl)-1,4-Butanedione by the Oxidative Coupling of Dimethylsilyl bis-enol ether The importance of 3,4-dibutyl-2,5-di(2-thienyl)thiophene, pyrrole and furan as precursors for the syntheses of conductive polymers and macrocyclic compounds has encouraged us to search for a general and practical route to synthesize these compounds. Because of the easy transformation of 1,4-diketone to thiophene, pyrrole and furan, synthesis of 3,4—dibuty1-1,4-(2-thienyl)-l,4- butanedione is the key step (Scheme 1-33). Scheme 1-33 H9C4 C4H9 / \ / \ S o 0 s (60 H904 (54)-g9 H904 c4H9 H904 C4H9 /\/\/\ /\/\/\/\/\/\ S S s S u s S O S (57d) (61d) (6 21) The first synthesis of 2,3-dibutyl-1,4-di(2-thienyl) butanedione was reported by Wiepart58 in 1990. The author used 45 46 the oxidative coupling of the dimethylsilyl bis-enol ether with ceric ammonium nitrate(CAN) (Scheme 1-34). The reported yield is 48% and the reaction was run in small scale. Scheme 1-34 C4Hg H9004 (EN/05“" + Cl zsiMcQ filial/EQN \S 0 Me \Me 8 l/ <5 3 <6 4) /NH4)2CC(N03)6 NaHCO3 MeCN “904 C4H9 / \ / \ S o o s (6 0d) This method had been used by Dr. Michael Benz59 to synthesize 3,4-dibutyl-2,5-di(2-thienyl)thiophene, pyrrole and furan. In order to make full use of this reaction to synthesize a large quantity of 2,3- dibutyl-l,4-di(2-thienyl) butanedione some questions still must be answered. First, how general is this coupling reaction? Second, can the yield be improved and the reaction be run on a large scale (e.g. 100 grams or more)? In order to answer the above questions, one of my efforts was on the study of the influences of reaction conditions on the coupling of dimethylsilyl bis-enol ether with ceric ammonium nitrate(CAN). 47 After several trials, it was found that the oxidative coupling reaction is highly depended on the quality of the starting dimethylsilyl bis-enol ether. Then, research was concentrated on the preparation of good quality dimethylsilyl bis-enol ether. Unfortunately, the use of excess of dimethylsilyl chloride or the change of reaction conditions, e.g. change the reagent addition procedure or run the reaction at different temperature (-20, 0, and 40 0C) did not give any better results. It was latter found that the crude dimethylsilyl bis-enol ether was still contaminated with some dimethyl chlorosilyl mono-enol ether(65) . The dimethyl chlorosilyl mono-enol ether(65) hydrolyzes during the work-up to form the silicone hydroxyl compound(66) (Figure 1-6). The hydroxyl group in the hydrolyzed product(66) might affect the oxidative coupling reaction of dimethylsilyl bis-enol ether to form the 1,4-diketones. And indeed, the use of purified dimethylsilyl bis-enol ether as starting material increased the yield of 1,4-diketons from 48% to 57% in one experiment. Figure 1-6 C4He C4H9 \ ./C' \ ./OH SI‘ /SI‘ Me/ Me — Me Me \ S \ S 48 Because of the difficulty of purification of dimethylsilyl bis- enol ether, a further attempt to improve this reaction has not been made and research was turned to use trimethylsilyl enol ether instead of dimethylsilyl bis-enol ether and the results are presented in section 1.4.2.2. 1.4.2.2 Synthesis of 3,4-Dialkyl-l,4-(2-thienyl)-l,4-butanedione by the Oxidative Coupling of Trimethylsilyl Enol Ethers With Ceric Ammonium Nitrate(CAN) During the search of reaction conditions useful for the preparation of good quality silyl enol ether it was found that a good quality of silyl enol ether can be easily prepared by the reaction of cholorotrimethylsilane with a ketone by using a slight excess of the former reagent. By this route it is easy to prepare a crude silyl enol other with >95% purity (by NMR data) which can be used as a starting material for oxidative coupling with high isolated yield of the 1,4-diketones (55%-67% based on the starting ketone) (Scheme 1-35). Scheme 1-36 shows one of the possible reaction mechanisms. Oxidation of silyl enol other by Ce+4 with one electron transferred leads to the formation of a radical cation which then loses a trimethyl silyl cation and forms a carbonyl radical. Then, the carbonyl radical can be self-coupled or reacts with another molecule of silyl enol ether to form another radical which is then oxidized by Ce+4 with the lost of +SiMe3 to form the expected 1,4-diketone. 49 Scheme 1-35 . 0 H9 CISIMC3 ‘ / \ 05H" » / \ / S NaI/Et3N,MeCN S o rt, 1'2 hr, 97% OSlM93 (63d) (67d) (NH4)2Ce(N03)6 NaHC03,MeCN 69% H904 C4Hg / \ / \ S o o 3 (60d) Scheme 1-36 / \ C4H9 Cc” c,H, gun—L /S\ cm, S / OSiMeg OSIMG3 O 0 He / \ / ‘ S OSIM93 “904 C4H9 “904 C4He Ce+4 / \ / \ _ / \ . / \ H904 2 WC‘HG W S O 50 The generality of this synthesis of 1,4-diketones has also been investigated by using different alkyl groups and the results are summarized in Scheme 1-37. All the structures of the 1,4-diketones have been characterized by lH-NMR, l3C-NMR, mass spectra and IR spectra. Generally speaking, the reaction is reliable for different alkyl groups and the yield is quite stable. This is consistent with the proposed radical reaction mechanism (Scheme 1-36). Scheme 1-37 R R R / ClSiMe s\ Nat/ErskiMecfi (67) Wham»; I \ / \ 0 Fl. 12 hr, NaHC03, MeCN S O o S (63) (60) Starting Ketones Yield of 1,4-diketones(isolated,%) R = H 5 5 R = Me 6 5 R =- Et 60 R = Butyl 67 R - Hexyl 63 51 In general, the use of trimethylsilyl enol ether instead of dimethylsilyl bis-enol ether usually can give a better yield of 1,4- diketones. This provides a general and practical route to the synthesis of 1,4-di(2-thienyl)-2,3-dialkyl-1,4-butanediones. As an extension of this reaction, an attempt at the synthesis of 1,4-di(2-pyrryl)-l,4,-butanedione has been conducted. Reaction of 2- acetyl pyrrole with 2.2 equivalents of chlorotrimethylsilane in the presence of NaI(2.2 eq.) and Et3N (2.2 eq) gave 2-(1-trimethylsilyl pyrryl)-trimethylsilyl ethenol ether(77) in 91% yield. Oxidation with ceric ammonium nitrate(CAN) gave an intractable product. No 1,4- di(2-pyrryl)-l,4,-butanedione(78) was isolated (Scheme 1-38). Scheme 1-38 H - MS CAN H N I, ClS M 2.2 TM a 1 e3( eq): 8 _ a: T H NEt3,MeCN,rt,4hrs 9Q ' D D 91% MeCN (76) (77) (78) Failure of oxidative coupling of 2-(1-trimethylsilyl pyrryl)- trimethylsilyl ethenol ether to form the l,4-di(2-pyrryl)-l,4- butanedione by the use of CAN as oxidant might be attributed either to the acidity of proton of the ammonium ion in the reagent or the instability of the starting silyl enol ether, the intermediates or the product in the oxidative condition. Because of this unexpected result, some of my efforts have been involved in the use of different 52 oxidants as coupling reagents and the results are presented in section 1.4.2.3. , 1.4.2.3 Synthesis of 3,4-Dialkyl-1,4-(2-thienyl)-l,4-butanedione by the Oxidative Coupling of Trimethylsilyl Enol Ethers with VOCl3/Pyridine In the previous section, a convenient synthesis of 2,3-dialkyl- 1,4-di(2-thienyl)-1,4-butanediones by the oxidative coupling of the silyl enol ethers with ceric ammonium nitrate(CAN) was described. In the search for new oxidative reagents for the syntheses of 1,4- diketones from ketones we found that VOClg/pyridine can also bring about the oxidative coupling reaction of silyl enol ethers to form the expected 1,4-diketones. Scheme 1 -39 O TMSO 0 0 JVR‘ Nal, ClSiM93 R VOCI3/Pyridine R j» —— > R, H MeCN/EtaN R R- MeCN R R R'Ru Re R. Some of the results are listed in table 1-2. Table 1-2 53 Starting Ketones 1,4-Diketones Yield(Overall, %) o _.o o 0* a o ‘9 (68) (69) o o o S S 50 \ / \ / \ / o S 0 O S M 55 \ / \ / 4 9 H904 C4H9 \ / (63d) (60d) 0 S O O S S 54 \ / \ / \ / CeHra H1306 06H“, (639) (609) 0 o 0 C5 (515 5‘ (70) (71) 0 o o )k M .7 (72) (73) O O , M 6'1 (75) 54 The reaction mechanism is thought to be similar to that obtained by using CAN as oxidant. The use of pyridine as a base makes the reaction in a milder condition so as to increase the yield of products. Acetonitrile is a good solvent for this reaction. The use of other solvents e.g. THF and CH2C12 leads to a lower yield. By this procedure, the synthesis of 1,4-di(2-pyrryl)-l,4- butanedione by the oxidative coupling of the silyl enol ether has been attempted by using several different conditions. Oxidation of the protected silyl enol ether, 2-(l-trimethylsilyl pyrryl)- trimethylsilyl ethenol ether, with vanadium oxytrichloride and 1.0 eq of pyridine in acetonitrile at 0 °C for 15 minutes gave a low yield of the expected 1,4-diketone (Scheme 1-43). Both lowering the temperature to -40 °C and extending the reaction time to one hour both did not lead to a higher yield of product. Nor did the use of VO(OEt)C12 as an oxidation reagent in dichloromethane improve the yield of 1,4-diketone. The lower yield of 1,4-di(2-pyrryl)-1,4—butanedione from the oxidative coupling reaction of 2-(1-trimethylsilyl pyrryl)- trimethylsilyl ethenol ether with VOCl3, or VO(OEt)C12 reagents might be attributed to the instability of the starting material, the intermediates and the product. The shorter reaction time assures the survival of some of the product, which lead to the isolation of a low yield of 1,4-di(2-pyrryl)-1 ,4-butanedione. 55 Scheme 1-40 H Nal, CISiMe3(2.2 eq) MS "TMS VOClale> NEt3, MeCN. rt. 4 hm= 91% 0°C, 15 min (76) (77) (78) In summary, a new procedure for the synthesis of 1,4- diketones from ketones by the oxidative coupling of the silyl enol ether with VOClg/pyridine has been developed. By this method an alternative route to the syntheses of 3,4-dialkyl-2,5-di(2- thienyl)thiophenes, pyrroles and furans has also been achieved and the results are presented and discussed in section 1.4.2.4. Generally speaking, the synthesis of 1,4-diketones by the oxidation of silyl enol ethers with CAN is more convenient and suitable for large scale synthesis, but oxidative coupling of silyl enol ethers with VOClg/pyridine is more convenient for small scale synthesis. 1.4.2.4 Synthesis of 3,4-Dialkyl-2,5-di(2-thienyl)thiophenes, Pyrroles and F urans In section 1.4.1 the synthesis of 3,4-dibutyl-2,5-di(2- thienyl)thiophene by the Grignard coupling reaction was discussed and the results are compared with those reported. Generally speaking, the reaction is good only for small scale synthesis 56 of 3,4-dibutyl-2,5-di(2-thienyl)thiophene. It is difficult to synthesize 3,4-dialkyl-2,5-di(2-thienyl)pyrroles because of the acidity of the proton on pyrrole nitrogen. Because large quantity of l,4-di(2-thienyl)-2,3-dialkyl-1,4- butanediones have been synthesized by the oxidative coupling of silyl enol ether with ceric ammonium nitrate or VOCl3/pyridine as described in Sections 1.4.2.2 and 1.4.2.3 it is reasonable to synthesize 3,4-dialkyl-2,5-di(2-thienyl)thiophenes, pyrroles and furans by the use of these 1,4-diketone precursors. Reaction of l,4-di(2-thienyl)-2,3-dialkyl-l,4-butanediones with P285 or Lawesson's reagent gave high yield of 3,4-dialkyl-2,5- di(2-thienyl) thiophene. Some of the results are summarized in Scheme 1-41. The structures of the terthiophenes have been characterized by lH—NMR, 13C-NMR, mass spectra, UV-Vis and compared with the results from Grignard coupling products. Scheme 1-41 R R R R / \ / \ Lawessons > / \ / \ / \ s O O S Toluene, reflux S S S (60) 4 h' (57) 57 Starting 1,4-diketones Isolated Yield of Terthiophenes(%) a, R-H b, R=Me c,R=Et d, R=Butyl e, R=Hexyl 82 84 88 81 89 The high yield of thiophene formation plus the easy synthesis of 2,3-dialkyl-l,4-di(2-thienyl)-1,4-butanediones it a practical route to the synthesis of 3,4-dialkyl-2,5-di(2-thienyl) thiophenes. It also makes the synthesis of 3,4-dialkyl-2,5-di(2-thienyl) pyrroles and furans ease. For instance, reaction of the 2,3-dialkyl-1,4-di(2-thienyl)-l,4- butanediones with NH4Ac, AcOH, (Ac)20 gave good yield of 3,4- dialkyl-2,5-di(2-thienyl)pyrroles. Scheme 1-42 shows some of the results. The structures for the formation of the pyrrole derivatives is characterized by 1H-NMR, 13C-NMR, mass spectra, UV-Vis. 58 Scheme 1-42 R R R R ON: / \ / \ "H‘ : / \ / \ / \ S o o s MOH-Aozo s N s reflux, 2 days H (60) (61) Starting 1,4-Diketones Isolated Yield of Products(%) a,R=H 78 b, R=Me 75 c, R=Et 74 d, R=Butyl 80 e, R=Hexyl 81 Reaction of the 2,3-dialkyl-1,4-di(2-thienyl)-l,4- butanediones(60) in HCl/Aczo at 80 °C for 15 hours gave good to moderate yield of 3,4-dialkyl-2,5-di(2-thienyl)furans. Some of the results are summaried in Scheme 1-41. The structures of the furan derivatives is characterized by lH-NMR, 13C-NMR, mass spectra, UV- Vis etc.. 59 Scheme 1-43 R R R R HCI /\ /( (g..,>/\,\/\ S O O S AC2O, 85 0C S O S (60) 10 hr (62) Starting 1,4-Diketones Yield of Products(%) a, R -= H 71 b, R = Me 65 c, R - Et ()4 d, R a Butyl 69 e, R = Hexyl 61 In summary, the oxidative coupling of trimethylsilyl enol ethers with ceric ammonium nitrate(CAN) is a general and practical route for the synthesis of 2,3-dialkyl-1,4-di(2-thienyl)-l,4- butanediones. By this method the syntheses of several 3,4-dialkyl- 2,5-di(2-thienyl)thiophenes, pyrroles and furans have been achieved. In addition, the oxidative coupling of trimethylsilyl enol ethers with VOCl3/pyridine reagent provides a convenient route to the syntheses of variety of 1,4-diketones. Chapter 2 Syntheses and Spectroscopic Studies of Thiophenc and Mixed Thiophenc Oligomers Synthesis and property study of conductive oligomers is another interesting research area. The information from the study of conductive oligomers can help us to understand the conductive mechanisms of conjugated organic polymers. So far, one of the major problems in this research area is the difficulty of synthesizing specific molecular weight of conjugated oligomers or single oligomer. In this chapter, the synthesis and property study of some new conjugated thiophene and mixed thiophene oligomers will be presented. The study of the influence of thiazolo[5,4-d1thiazole and 1,3,4- thiadiazole on the properties of thiophene oligomers has encouraged us to synthesize mixed thiophene oligomers which contain thiazolo[5,4-d1thiazole and 1,3,4-thiadiazole rings. Several B- unsubstituted mixed thiophene oligomers have been synthesized (Figure 2-1). During the research, one of the major problems was the low solubility of the oligomers. For example, although unsubstituted pentathiophene still shows some solubility in organic solvent, the analog heptathiophene shows very low solubility in most organic solvents, e.g. CHC13, CH2C12, acetone, acetonitrile, etc.. The mixed thiophene oligomers show ever lower solubility in common organic 60 61 solvents. For instance, although terthiophene is very soluble in most organic solvents the analogs 2,5-di(2-thienyl)thiazolo[5,4-d]thiazole and 2,5-di(2-thienyl)-l,3,4-thadiazole show low solubility in hexanes, CH2C12, etc. The higher oligomers are only slightly soluble in CHC13, CH2C12, acetone, acetonitrile, etc. The low solubility of these unsubstituted thiophene oligomers make it difficult to study relationship of structures and properties. Figure 2-1 s s s s ,N 8 s WEI—U U—(s In; §\ [7 (33) (21b) 3 s s s s s s j“ 3 s s Wm Wire-Du u (79) (80) Ssssss sssflssss WWW WSIWI u w (31) (82) In order to improve the solubility of these thiophene oligomers, butyl groups have been introduced in the thiophene B-positions. In Section 1.4 of this thesis an improved and practical route to the synthesis of 3,4-dialkyl-2,5-di(2-thienyl)thiophene, pyrrole and furan has been described. By this route large quantity of 3,4-dibutyl- 2,5—di(2-thienyl)thiophene were synthesized. The high solubility and regularity of this thiophene oligomer make it a good precursor for the syntheses of higher thiophene oligomers. 62 Although there are many reports on the study of thiophene 71-74 oligomers research on the influence of heterocyclic systems to the thiophene oligomers is relatively spare75. In order to provide more information on the influence of heterocycles to the properties of polythiophene, the following oligomers 83-87 were chosen as candidate model oligomers (Figure 2-2). Figure 2-2 (83) (84) (85) (86) 63 Considering that thiophene, pyrrole and furan can be easily synthesized by the reaction of 1,4-diketone with Lawesson's reagent (or P2S5), NH4OAc, HCI/Aczo, one of the key steps in the syntheses of compounds 83-85 is to synthesize the precursor 1,4-diketone 88 (Scheme 2-1). Scheme 2-1 Lawesson's Reagent (88) The synthesis of the l,4-diketone(88) has been achieved by two different methods. One is Friedel-Crafts acylation of the or-terthiophene with succinyl chloride. Reaction of 3',4'-dibutyl- 2,2',5',2"-terthiophene with succinyl chloride by using tin(IV) chloride as a catalyst in dichloromethane at 0 °C gave 22% yield of the expected 1,4-diketone 88 (Scheme 2-2). 64 Scheme 2-2 anl4/CHzcl2 0 °C, 2 hr 22% The 1,4-diketone(88) is a stable yellow needle compound with a melting point 178-179 °C. UV—Vis shows a maximum absorption at 390nm. lH-NMR shows the two b-protons of the thiophene rings which are close to the carbonyl groups with chemical shift at 7.73 and 7.17 ppm respectively and coupling each other. The coupling constant is 4.4Hz. The three protons on the terminal thiophene rings show a typical pattern of an tar-substituted thiophene. The chemical shifts are 7.32, 7.14, and 7.05 and the coupling constants 5.3, 4.4 and 1.3Hz respectively. The mass spectrum shows a relatively stable molecular ion with the relatively intensity 55.7. The base line is at m/z=415. The peak with m/z=401 may correspond to the molecular ion with two positive charges. This compound may be used as a model compound for the study of polaron formation by doping and polaron interaction through a non conjugated carbon-carbon chain. Another route for the synthesis of 1,4-diketones is the use of Stetter's reaction“. Reaction of 5-formyl-3',4'-dibutyl-2,2',5',2"- terthiophene with divinyl sulfone catalyzed by 3,4-dimethyl-5-(2- 65 hydroxyethyl)-thiazolium iodide gave 67% of the l,4-diketone 88 (Scheme 2-3). Scheme 2-3 Cat.‘ NaOAc, EtOH: 80 °C, 24 hrs Cat. = 3,4-Dimethyl-5-(2-hydroxyethyl)-thiazolium iodide The synthesis of the a-heptathiophene(83) have been accomplished by treatment of the l,4-diketone(88) with P285 or Lawesson's reagent in toluene. For example, reaction of 88 with 1.2 equivalent Lawesson's reagent (excess) in refluxing toluene for two hours gave the heptathiophene(83) in 82% yield (Scheme 2-4). 66 Scheme 2-4 Lawesson's reagent 7' Toluene, reflux 2hr, 82o/o (83) The orange needles of heptathiophene 83 melts at 129-130 °C. The UV—Vis spectra show a maximum absorption at 429nm. Compared with other alkyl substituted heptathiophene, it seems the two butyl groups on the B-positions of the same thiophene ring lower the‘conjugation of the oligomer. For instance, the or, or'-di-terbutyl- heptathiophene shows a UV-maximum absorption at 451nm, and the B-monobutyl-substituted heptathiophene shows a UV-maximum absorption at 440nm (Table 2-1). The mass spectrum shows that the molecular ion peak is the base line, which means that removal of one electron from the heptathiophene leads to a relatively stable radical cation. Removal of one more electron from the original formed molecular ion radical lead to the formation of a new molecular ion with two positive charges. This is indicated by relatively strong peak at m/z=400 (relative intensity 25.15%). This result shows that heptathiophene may be a good candidate as a model compound for the study of polaron and bipolaron formation by doping. Further research with this compound may provide more interesting results. 67 Compounds UV(nm) Maximum Absorption 0000000 OQDDDMHOO 4404 OOQWWSDQO 435‘ 0000000 00003000 466 68 The transformation of the l,4-diketone(88) to pyrrole derivative(85) has been achieved by the reaction of the 1,4-diketone with NH40Ac/AcOH/AC20 at 100 °C under N2 for 24 hours. The isolated yield is relatively low(25%) (Scheme 2-5). The low isolated yield of the pyrrole derivative 85 might be attributed to the instability of the starting diketone 88 and/or the product 85 in the acidic condition. Attempts to improve the yield by changing the reaction conditions (e.g. temperature or reaction time) failed. Scheme 2-5 S S S 0 o S S 8 NH OAc/Ac O HOAc ' / \ / \ / \ / \ / 4 2 ' > 100 °C, 24hrs (33) 25% H S S S N S s \/ \/ \/ \/ \/ \/ \S/ (35) Compound 85 is an orange solid with melting point of 141-142 °C. The UV-Vis spectrum shows a maximum absorption at 437nm(CHCl3), which corresponds to a bathochromic shift of 8nm compared with that of the thiophene analog 83. This indicates that the replacement of a thiophene ring with a pyrrole in the thiophene oligomers increases the conjugation so as to lower the bandgap. The mass spectrum shows that the molecular peak is the base line, which means 69 that the removal of one electron from the neutral molecule forms a relatively stable radical cation. This is similar to the result of heptathiophene 83. The furan derivative 85 has been synthesized by the acid induced cyclization of the 1,4-diketone(88) with 19% yield (Scheme 2-6). This unusually low yield of furan may be attributed to the instability of the starting 1.4-diketone 88 and the product 85 in the acidic environment. Attempts to improve the yield by changing the reaction temperature and reaction time or by using different acids (e.g. H2804, H3PO4) were not successful. Scheme 2-6 \8 S S 00 s s s HCI/A020 \ / \/ \/ \/ \/ 95°C,10hrs> 1 9% (88) S S S 0 S s \ \/\/\/\/\/\S/ (84) Compound 84 is an orange solid with melting point 112-114 °C. The UV-Vis spectrum shows a maximum absorption at431nm (CHC13), a 2nm bathochromic shift compared to that of the thiophene analog 83 (see Table 2-1). The mass spectrum shows the base-line at mlz=784 which corresponds to the molecular ion peak. 70 The successful syntheses of the thiophene oligomer 83 and the pyrrole and furan derivatives 85 and 84 encouraged us to search for the possibility of syntheses of the 1,3,4-thiadiazole and thiazolo[5,4- d] thiazole derivative oligomers 86 and 87. The synthesis of the 1,3,4-thiadiazole derivative(86) has been achieved by the condensation of the (Jr-terthiophene monoaldehyde (89) with hydrazine monohydrate and elemental sulfur. The isolated yield is low (12%) (Scheme 2-7). This low yield may be attributed to the instability of the starting material and/or the product in the reaction conditions. Attempts to improve the yield by changing the reaction conditions (reaction time, temperature, and ratio of sulfur) failed. Scheme 2-7 7 H0 Pro lene 1 001 m D D + N2H4.H20 + S(excess) py g y : 120°C, 481113 12% (89) Compound 86 crystallizes as orange needles which melts at 206-208 oC(decomp.). The UV-Vis spectrum shows the maximum absorption at 417nm, which is a12nm shift to shorter wavelength 71 compared with the result of the thiophene analog(83) (see Table 2- 1). This means that the replacement of a thiophene ring in the heptathiophene with a 1,3,4-thiadiazole ring reduces the conjugation and increases the bandgap. The synthesis of the thiazolo-[5,4-b]thiazole has been achieved by the condensation of the terthiophene monoaldehyde with dithiooximide. Condensation of the a-terthiophene monoaldehyde (89) with dithiooximide in refluxing DMF under N2 for 30 minutes gave a 34% yield of the expected thiazolo-[5,4-b]thiazole derivative(87) (Scheme 2-8). Scheme 2-8 The thiazolo[5,4-blthiazole derivative(87) is an orange-red needle compound with a melting point 178 °C(decomp). The UV-Vis spectrum shows the maximum absorption at 466nm. The mass 72 spectrum shows that the molecular ion is not as stable as that of the corresponding thiophene oligomer. Further study may provide more information on the influence of thiazolo[5,4-b]thiazole on properties of the thiophene oligomers. Chapter 3 Synthetic Approachs of Some New Conjugated Macrocyclic Compounds Synthesis and study of conjugated macrocyclic compounds with 18 or more n-electrons is one of the promising research areas that evolve from the traditional annulenes chemistry", to relatively new applications in photo therapy77, organic conductors and organic superconductors". Annulene chemistry is one of the branchs of chemistry that deals with conjugated cyclic polyenes. The central role of annulene chemistry is to study the aromatic and antiaromatic properties of conjugated cyclic compounds. According to Huckel's theory a planar conjugated cyclic compound is aromatic if the number of n-electrons in the conjugated system is 4n+2, where n is an integer. Whereas, a planar conjugated cyclic compound with 4n n-electrons is known as antiaromatic. Theoretical calculations of the resonance energy show that planar conjugated cyclic compounds with [4n+2] n-electrons possesses positive resonance energy which stabilizes the systems while those with [4n] u-electrons possess negative resonance energy which destabilizes the systems. The calculations also predicted that the resonance energies might vanish when the number of n-electrons 73 74 exceeds 2679 and the molecule is planar. The change of resonance energy with the number of n-electrons is shown in Figure 3-1. Figure 3-1 > >3 >: >3: >8 -O.5 " 4 The Huckel aromatic theory is still meeting the challenge of experimentalists. Synthetic organic chemists are still interested in the synthesis and study of new annulenes. So far, the largest autiaromatic annulene synthesized and characterized is the 40 1c- Clcctrons expanded porphyrin, turcasarin80 (Figure 3-2). 75 Figure 3-2 Turcasarin The successful synthesis of turcasarin indicates that the resonance energy of aromatic and antiaromatic may be not significant when the n-electrons of the conjugated macrocycles exceed 26. Medical use and bioactivity are other important impetus to the research of conjugated macrocycles. Photo dynamic therapy of cancer by the use of expanded porphyrins is one of the examples. Porphyrin is a well-known heteroannulene compound with 18 u-electrons. Hematoporphyrin derivatives (HPD) have been used as photo sensitizers for the photoradiation therapy of cancer since 19752. Hematoporphyrin derivatives photoradiation therapy of cancer relies on the discovery of that hematoporphyrin derivatives are selectively retained by the cancer cells. When a human body affected with cancer is injected with a certain dose of HPD in vein the HPD will be selectively retained by the cancer cells for 2-3 days. If the body is exposed to a laser light with the wavelength of 625-635nm (red 76 light), the HPD will be excited by the light. Then, the excited state of HPD transfer the energy to the ground triplet state of the oxygen(302) to form the excited singlet state of oxygen(102) in the cells. The excited singlet state of oxygen(102) in the cells in turn oxidizes the substrate of the cancer cells and kills them. Although HPD photo radiation therapy of cancer have many advantages over chemotherapy, the similarity of the adsorption wavelength of hematoporphyrin derivatives to that of the natural heme porphyrins of the human body limit its clinical applications. One of the improved methods is the use of expanded metalloporphyrins which have different adsorption wavelength from the heme porphyrins in the human body. The potential application of expanded metalloporphyrins in photo therapy of cancer makes the synthesis and property study of expanded porphyrins and other conjugated macrocyclic compounds one of the promising research areas. The use of conjugated macrocyclic compounds as potential organic conductors and superconductors is another interesting research area. Several conjugated metallomacrocyclic compounds and their low-dimensional polymeric compounds have been extensively investigated. Similar to the linear conjugated polymers, the stack of undoped conjugated macrocyclic compounds behaves as an insulator and the doped form shows a conductivity as high as 100831. For this kind of organic conductors, one of the most important things is the regularity of stack. Good conductivity has been found if the metallomacrocycles can form good and regular stacks. In order to form a good and regular stack the macrocyclic compounds should be 77 planar or almost planar. Of all the macrocyclic compounds, metalloporphyrins and phthalocyanines are two kinds of common compounds which have been more extensively investigated (Figure 3-3). Figure 3-3 The importance of conjugated macrocyclic compounds have inspired many chemists to do research on the synthesis and studies of these compounds, and a large number of conjugated macrocyclic compounds have been synthesized and characterized. For example, expansion of the porphyrin macrocycles by inserting odd numbers of carbon atoms alternately between the pyrrolic rings gives rise to a family of expanded porphyrins. These kind of compounds has been named platyrins by Professor E. LeGoff in Michigan State University, and [l,3,l,3]platyrin(9l)82, and [l,S,l,5]platyrin(92)83 have been synthesized. By a similar strategy, several other analogs of this kind of expanded porphyrins, [22]porphyrin(1,3,l,3)(93)84, [26]porphyrin(1,5,1,5)(95)85, 14-aza[26]porphyrin(l,51,5)(96)85, [26]porphyrin(3,3,3,3)(94)86 and [34]porphyrin(5,5,5,5)(97)87 have also been reported by different groups with the 78 [34]porphyrin(5,5,5,5)(97) as the largest aromatic system (Figure 3- 4). Figure 3-4 (9 l) (9 2) [1,3,1,3]Platyrin [1,5,1,5]Platyrin (93) (94) [22]Porphyrin(],3,l,3) [26]Porphyrin(3,3,3,3) 79 (9 5) (9 6) [26]porphyrin(l,5,1,5) 14 aza[26]porphyrin(1,5,l,5) R=H, Ph, Et (97) [34]Porphyrin(5,5,5,5) By inserting a benzene, pyridine or other heterocyclic rings between the pyrrolic rings of porphyrin macrocycle several other expanded porphyrins have also been synthesized recently. For instance, the syntheses of new expanded porphyrins(98, 99)88 and the porphocyanine(100)89 have been reported. Structurally, expanded porphyrins 100 is similar to [l,3,l,3]platyrin 91 but 98 and 99 are different (Figure 3-5). Actually, compounds 98 and 99 80 are not conjugated in the macrocyclic system, but [l,3,l,3]platyrin and porphocyanine(100) are conjugated. Figure 3-5 (100) Porphocyanine Footballene(101)90 is another expanded porphyrin with the replacement of two pyrrolic rings to the two methine group in porphyrin. Footballene 101 an antiaromatic annulene with 24 1t- 81 electrons. It can be named as [24]porphyrin(l,4,l,4). Molecular calculation of force field by the program MM2 has predicted that footballene 101 might be present in three different oxidation states with 22, 24, and 26 u-electrons respectively31 (Figure 3-6). Research on the possibility of these different oxidation states may provide direct evidence of aromatic and antiaromatic properties of heteroanullenes. Figure 3-6 (1 0 l ) Footballene . 22-1t Sapphyrin(104)91 is a modified structure of pentaphyrin(103)92. It contains five pyrrolic rings and four methine groups in the macrocyclic system, one methine group short compared with that of pentaphyrin. Sapphyrin can be also thought as the expanded ring system of porphyrin(2,l,0,l)(102)91. By the replacement of one or two pyrrolic rings of sapphyrin with furan or thiophene, oxasapphyrin(107)92, thiasapphyrin(105)92 and dioxasapphyrin(106)92 have also been reported (Figure 3-7). Figure 3-7 9 Me Et Et H H El Et Me H H Me (1 0 2) Porphyrin(2,l ,0,1) (l 0 3 ) Pentaphyrin 83 (1 04) (105) Sapphyrin Thiasapphyrin Me Me (1 0 6) (l 0 7 ) Dioxasapphyrin Oxasapphyrin Other expanded porphyrins reported includes hexaphyrin (103)?3 rubyrin(109)94, and rosarin(110)95. Hexaphyrin(108)93 is an expanded porphyrin which contains six pyrrolic rings and six methine groups in the macrocyclic ring system. Rubyrin(109)94 contains six pyrrolic rings and four methine groups which is two methine groups short compared with that of hexaphyrin 108. 84 Because there are two pairs of pyrrolic rings connected together directly rubyrin can be thought as an expanded porphycene (see below). Rosarin(110)95 contains six pyrrolic rings and three methine groups (Figure 3-8). Figure 3-8 (109) (110) Rubyrin Rosarin 85 In addition to the many reports on the syntheses and studies of conjugated macrocycles based on the expansion of porphyrins, there are many interests on the systems of expanded isomeric porphyrins. For example, porphycene(lll)96 is an isomeric porphyrin with 18 rt-electrons. It can be identified as porphyrin(2,0,2,0). The ethylene bridged porphycene-like(112) is a [20]heteroannulene97. By inserting a certain number of methine groups or a five or six member cyclic ring between the connected pyrrolic rings of the porphycene, several new macrocyclic compounds, expanded porphycenes, have been synthesized. For example, [22]porphyrin(2,2,2,2)(ll3)97 and the acetylene-cumulene porphyrinoid(ll4)97, the expanded porphycene [26]porphyrin(6,0,6,0)(l15)”, as well as the heterocyclic expanded porphycenes (116)”, (117)100 have been synthesized (Figure 3-9). Figure 3-9 (111) (112) Porphycene Bridged Porphycene Et H Et (1 l 3) [22]Porphyrin(2,2,2,2) 86 Et Et Ei E H H H H El Et Et Et (1 1 4 ) Acetylene-Cumulene Porphyrinoids 87 Corrole(ll9)1°l, the aromatic basic structure of the ring framework of vitamin B12, and its isomer, isocorrole(120)102 both contain four pyrrolic rings and three methine groups, one methine group short compared to the structure of porphyrins(118) (Figure 3- 10). The conjugated pentapyrrolic macrocycle(121)103 can be thought as the expanded isocorrole. The furan analogs(122, 123)104 of macrocycle 121 have also been reported in the literature (Figure 3-10). Figure 3 - 10 E‘ E1 Me 6 H H E! El El Et E1 E1 M9 H M9 (1 l 8 ) (l l 9 ) Tetraethylporphyrin Corrole 88 H Me Et E‘ H Me Et Et H Me Me Me (120) (12 1) Isocorrole H Me (122) (123) Another area of research on the syntheses and studies of porphyrin analogs and their expanded systems is the use of furan, thiophene, pyridine or other heterocyclic compounds in place of the pyrrole ring of porphyrins. Because of the similar structure and chemical reactivity of furan and thiophene with pyrrole, many efforts have been involved in the syntheses and studies of furan and thiophene analogs of porphyrin, porphycene and their expanded systems. For instance, although the oxygen or sulfur-bridged 89 [20]annulene tetraoxaisophlorin(125) and tetrathiaisophlorin(127) are unknown, their oxidized dications, the furan and thiophene analogs of porphyrin, (124)105 and (126)106 have been reported. The furan analogous of porphycene (128) and (129) have also been synthesizedlm. Because of the size of sulfur atom the thiophene analog of porphycene (130) is still unknown. However, a mixed thiophene and pyrrole containing porphycene analog (131)108 has been reported recently. The expanded tetraoxaporphycene (133) and it's dication (132) have also reported109. A tetraoxa[26]- porphyrin(3,3,3,3)(l36) and the expanded tetrathiaporphycene (134) and (135) have also been synthesized110 (Figure 3-11). Figure 3-11 9O 91 92 Some other conjugated macrocyclic compounds which contain heterocyclic compounds other than pyrrole, furan and thiophene have been also synthesized. For example, texaphyrin(l37, 138)111 is a kind of conjugated macrocyclic compounds which contain imine groups in the conjugated systems, and may be used as photo- sensitizers in the photo dynamic therapy. Other macrocyclic )1“ compounds synthesized include the macrocyclic ketone (139 and the imidazole containing coronand(l40)“2, etc. (Figure 3-12). Figure 3 -12 Me Me El El I \ / l 1 NH ['1' l OMe MBOKIN N OMe MeO I): 0M9 All H H Pl 0M6 N N I / \ I El El MeMe (138) 93 1,3,4-Thiadiazole is a heterocyclic compound with a broad range of bioactivities113'115. In Chapter 1 Section 1.3 a convenient, and efficient one-pot procedure for the synthesis of 2,5-diary-l,3,4- thiadiazole has been described. Considering that the shape similarity of 1,3,4-thiadiazole with pyrrole, thiophene and furan, and there is no report in the syntheses of macrocyclic compounds containing 1,3,4-thiadiazole part of my efforts has been involved in the attempted syntheses of several new conjugated macrocyclic compounds which contain 1,3,4-thiadiazole rings. The results will be described in Sections 3.1 and 3.2. Another part of my research is on the syntheses of new conjugated hexathiophene macrocyclic compounds and the results will be reported on Sections 3.3 and 3.4. 3.1 Synthetic Approaches of A New Tetrapyrrolic Macrocyclc Containing 1,3,4-Thiadiazole The convenient procedure for the synthesis of 2,5-diaryl-l,3,4- thiadiazoles which has been described in Section 1.3 of this thesis encouraged us to do research on the application of this procedure to the synthesis of a new 1,3,4-thiadiazole containing tetrapyrrolic macrocyclic compound(141). It can be predicted that compound 141 can resonance to another unknown macrocyclic compound(l42) (Figure 3-13). Molecular modeling with MM2 shows that compound 142 is the lower energy state. Figure 3-13 N-N N=N I \ /, S /l / / S \ \ N l-P N N— / H ri‘ H / S N —N N I I S / , , / \ \ ’ / N'N N=N (141) (142) The molecule is expected to be essentially planar by force field calculation. The three dimensional structrue and space-filling structures of compound 142 are shown in Figure 3-14. 94 95 Figure 3-14 (142a) (142b) 96 (l42c) (142d) Retrosynthetic analysis shows compound 141 might be synthesized by the oxidation of the unknown macrocyclic compound 143 which in turn might be synthesized by the condensation of 5,5'- bisformyl dipyrrylmethane with hydrazine monohydrate and elemental sulfur (Scheme 3-1). Scheme 3-1 97 Obviously, the key step in this synthetic strategy is the macrocyclization of compound 143 (Scheme 3-2). By the use of the synthetic procedure of 1,3,4-thiadiazole described in Section 1.3 we have attempted to synthesize the unknown macrocyclic compound (143) and the results are presented and discussed as follows. Scheme 3-2 \ / H ‘u r.’ H 0 o (144) N2H4-H20/S Propylene Glycol r ? The precursor 5,5'-bisformyl-dipyrrylmethane 144 has been synthesized in four steps starting with pyrrole by a modified experimental procedure described by Clezy and coworker113 (Scheme 3-3). 98 Scheme 3-3 5 o (I \j + i benzene M H202,KOH,H20/E(E):{ \\ // fl 0' 0' 31% fl ('1'. 89% 7 u n (145) (146) (147) o NaBH4 .4“, HM Eenzolehloride M O 0 84% H H (144) (148) When 5,5'-bisformyl-2,2'-dipyrrylmethane(l44) was submitted to the reaction with hydrazine monohydrate and elemental sulfur, only intractable tar-like materials were formed and flash column chromatography failed to isolate any cyclized product. Changing reaction conditions by reducing the reaction temperature and/or shortening the reaction time did not give any isolable cyclization product either(Scheme 3-4). One major reason for the failure of this reaction might be attributed to the instability of the starting material, 5,5'-bisformyl-2,2'-dipyrry1methane(144) and/or product in the reaction conditions. Scheme 3 -4 l; ’ / N2H4.H20/S H H u » Intractable Materials 0 O H Propylene Glycol . 120 °C, 2 days, N2 99 Considering that that B-substituent alkyl groups might favor the macrocyclization and stabilize the pyrrole rings, research was turned to the synthesis of the macrocyclic compound 150 with methyl groups on the B-positions of pyrroles (Scheme 3-5). Scheme 3-5 \ / H \ N N / N2H4.HzO/S _; O H H O H Propylene Glycol ? (149) (150) 5,5'-Bisformyl-3,3',4,4'-tetramethyl-2,2'-dipyrrylmethanel49 was synthesized by six steps(Scheme 3-6). Reaction of 2- ethoxycarbonyl-3,4,5-trimethylpyrrole(15l) with Pb(OAc)4 in acetic acid at room temperature for three hours gave the 2- ethoxycarbonyl-3,4-dimethyl-5-acetyloxylmethylpyrrole(152) in 85% yield. Refluxing 2-ethoxycarbonyl-3,4-dimethyl-5- acetyloxylmethylpyrrole(152) in ethanol with the catalysis of concentrated HCI for two hours gave the 5,5'-ethoxycarbonyl- 3,3',4,4'-tetramethyldipyrrylmethane(153) in 79% yield. Hydrolysis of 5,5'-ethoxycarbonyl-3,3',4,4'-tetramethyldipyrrylmethane(153) followed by decarboxylation gave the 3,3',4,4'-tetramethyl-2,2'- dipyrrylmethane(154) in 92% yield. Formylation of the 3,3',4,4'- tetramethyl-2,2'-dipyrrylmethane(154) with DMF and benzoyl 100 chloride gave the 5,5'-bisformyl-3,3',4,4'-tetramethyl-2,2'- dipyrrylmethane(l49) in 87% yield (Scheme 3—6). Scheme 3-6 / \ Pb(OAC)4, AcOH / \ CH rl. 3hr r 3020 u 3 85% ElOzc n CH20Ac (151) (152) HCl(conc.) ElOH reflux, 2hr 79% 1)EtOH. 5120. Na'OH re ux, 24 rs /\ H300”: /\ /\ N 2) '° N co El u H 3) 170 °C. 5hrsE‘OZC u H 2 92% (154) (153) DMF,PhCOCl -20 °C, 2hrs 87% N CHO DHC u H (149) Reaction of 5,5'-bisformyl-3,3',4,4'-tetramethyl-2,2'- dipyrrylmethane(l49) with hydrazine monohydrate and elemental 101 sulfur in the presence of small amount of tributylamine at 120 °C for two days led to the formation of an intractable tar—like material, and no cyclized product was isolated by flash column chromatography (Scheme 3-7). The change of reaction conditions by reducing the temperature and/or shortening the reaction time failed to give an isolable yield of cyclized product. Because of this failure of the synthesis of compound 142, further research on the synthesis of compound 140 was not attempted. Other efforts were expended on the attempted synthesis of other new conjugated macrocyclic compounds and the results are presented in Sections 3.2-3.4. Scheme 3-7 N-N \ I \ / \ \ / I szJ'IzO/S, BU3N \ S m I H u N \ \\ > “LI H H H O O PmpylekGlycol I hr. S N \ 120°C, 48hrs / \ \ N-N 3.2 Synthesis of A New Hexathiophene Macrocycle Containing 1,3,4-Thiadiazole In Section 1.4 of this thesis, an improved and practical route to the synthesis of 3',4'-dialkyl-2,2',5',2"-terthiophene was described. By this method, a large quantity of 3',4'-dibutyl-2,2',5',2"- terthiophene has been synthesized in this laboratory. By the 102 combination with the efficient procedure for the synthesis of 2,5- diaryl-l,3,4-thiadiazoles described in Section 1.3 of this thesis, a new macrocyclic compound which contains six thiophene rings and two 1,3,4-thiodiazole rings 154 has been chosen as a target compound. And part of my research work has been involved in the synthesis of this new compound (Figure 3-15). Figure 3-15 154 Molecular calculation of force field shows that the structure of this compound is not planar, but like a crown. MM2 energy minimized molecular structure, three dimensional structure and space-filling structures are shown in Figure 3-16. 103 Figure 3-16 7/////////// ....... / 154d Retrosynthetic analysis shows macrocycle 154 might be synthesized by the condensation of 5,5"-bisformyl-3',4'-dibutyl— 2,2',5',2"-terthiophene with hydrazine monohydrate and elemental sulfur (Scheme 3-8)- 104 Scheme 3-8 /\ /\ /\ +N2H4+S ? SCHO OHC S S (155 ) (154 ) Synthesis of 5,5"-bisformyl-3',4'-dibutyl-2,2',5',2"- terthiophenelSS has been achieved by the lithiation of the 3',4'- dibutyl-2,2',5',2"-terthiophene followed by the reaction with DMF (Scheme 3-9). It also has been synthesized by a Vilsmeier reaction (Scheme 3-10). Scheme 3-9 Him—(Big OHC S S S CHO (57) (155) a, BuLi(2.1 eq), hexane/THF b, DMF(2.4 eq), THF, Yield 81% 105 Scheme 3-10 M W” /\ I\ /\ /\ IS\ 3 s s 900' 2*" OHC s [\s CHO 77% (57) (155) Condensation of the 5,5"-bisformyl-3',4'-dibutyl-2,2',5',2"- terthiophene with hydrazine monohydrate and elemental sulfur at 120°C for two days gave only a polymeric product with no isolable yield of cyclized product. Shortening the reaction time to 24 hours led to the formation of polymeric product as the major product with a trace of cyclized product which was determined by mass spectrum to be 154 (Scheme 3-11). Scheme 3-1 1 S M WW 3 N (154 ) CHO Propylene glycol NS 120 °C, 24h (155 ) 106 Attempts to improve the yield of the macrocyclic compound 154 by the use of two step synthesis or high dilution technique failed. 3.3 Synthetic Approaches of A New Hexathiophene Macrocyclc When my effort was on the syntheses of new macrocyclic compounds by the use of 3',4'-dibutyl-2,2',5',2"-terthiophene as a precursor, one of the target compounds was compound 157. Compound 157 is a thiophene-derived annulene with 28 n-electrons and force field molecular calculation shows that it is not a planar molecule (Figure 3-17). Unfortunately, when I was going to synthesize this new macrocyclic compound, a synthesis of a similar macrocycle appeared in Tetrahedron Letterlog. At this time, my research was guided to the synthesis of a new hexathiophene macrocyclic compound 158. Compound 158 contains six thiophene rings and six methine groups in the macrocyclic system and is a 30 n-electron annulene (Figure 3-18). 107 Figure 3-17 R R R R (157) (157a) (157b) (1576) (157d) 108 Figure 3-18 Retrosynthetic analysis suggests that one of the approaches to synthesize compound 158 might be from the unknown macrocyclic ketone 15 9, and the preparation of compound 159 might be by the condensation of 5,5"-bisformyl-3',4'-dibutyl-2,2',5',2"- terthiophene(155) with 5,5"-bisacetyl-3',4'-dibutyl-2,2',5',2"- terthiophene(l60) (Scheme 3-12). 109 Scheme 3—12 m + / DHC SSS S S 8 CH0 (155) (160) By this strategy, one of the key steps is to synthesize the unknown macroketone 159 by condensation of 5,5"-bisformyl-3',4'- dibutyl-2,2',5',2"-terthiophene(155) with 5,5"-bisacetyl-3',4'- dibutyl-2,2',5',2"-terthiophene(160). Therefore, part of my effort has been invOlved in the synthesis of macrocyclic ketone 159 (Scheme 3-13). 110 Scheme 3-13 /\ /\ /\ ones 5 S CHO + MeOCS S SCOMe \/ \I \/ The 5,5"-bisacetyl-3',4‘-dibuty1-2,2',5',2"-terthiophene(160) has been synthesized by a Lewis's acid catalyzed acetylation of 3',4'- dibutyl-2,2',5',2"-terthiophene with 84% yield (Scheme 3-14 ). 5,5"- Bisacetyl-3',4'-dibutyl-2,2',5',2"~terthiophene(l60) is a stable orange colored needle solid compound with a melting point of 96-965 0C (uncorrected). The UV-Vis maximum absorption is 395nm. Scheme 3-14 I\/\ /\+c|_3_m HM /\ .- s s s n. 2hr. 84% H3000 s s s coca, (57) (160) Condensation of the 5,5"-bisacetyl-3',4'-dibutyl-2,2',5',2"- terthiophene(l60) with the 5,5"-bisformyl-3',4'-dibutyl-2,2',5',2"- 111 terthiophene(155) has been attempted in several different conditions(NaOEt/EtOH, NazCOg/EIOH and NaH/DMSO). Unfortunately, the only product isolated was polymeric materials. There was no trace of cyclization products isolated by flash column chromatography. It seems that the condensation reaction of 5,5"- bisacetyl-3',4'-dibutyl-2,2',5',2"-terthiophene and S,S"-bisformyl- 3',4'-dibutyl-2,2',5',2"-terthiophene is a step wise reaction. The two ends hardly react at the same time. When one end of 5,5"-bisacetyl- 3',4'-dibutyl-2,2',5',2"-terthiophene reacts with one end of the 5,5"- bisformyl-3',4'-dibutyl-2,2',5',2"-terthiophene a rigid dimeric compound formed which make the cyclization of the other ends difficult (Scheme 3-15). Scheme 3-15 base I \ I \ / \ + / \ I \ / \ , OHC S S S CHO H3COC S S S COCH3 The failure for the synthesis of the macrocyclic ketone by the condensation of 5,5"-bisacetyl-3',4'-dibutyl-2,2',5',2"-terthiophene with the 5,5"-bisformyl-3',4'-dibutyl-2,2',5',2"-terthiophene made us 112 to search for an alternate route to the synthesis of macrocyclic compound 15 8 . 3.4 Synthesis of A New Hexathiophene Macrocyclic Compound Another macrocyclic compound which is interesting to us is the new macrocyclic compound 161. Molecular mechanic calculation shows it is an aromatic compound with 30 n-electrons. MM2 molecular modeling shows that it has a perfect planar structure. The tetrahedral angles are calculated all less than 0.5°. The bond distances and bond angles are shown in 161d and 16le of Figure 3- 19. Figure 3-19 113 S 120.93° N N 134.58° 161d l61e The first attempt at the synthesis of this new compound was on the condensation of S,5"-bisformyl-3,4-3',4'-dibutyl-2,2',5',2"- terthiophene with an ammonium salt. However, all the results showed the ammonium salt is not as reactive as expected. For example, refluxing 5,5"-bisformyl-3',4'-dibutyl-2,2',5',2"- terthiophene with 2.0 equivalents of ammonium chloride in butanol 114 for 24 hours gave 85% of recovery of starting 5,5"-bisformyl-3‘,4'- dibutyl-2,2',5',2"-terthiophene. Extension of reaction time to 3 days leads to the formation of some intractable tarry materials with the recovery of 30% of starting materials. The use of ammonium acetate or ammonium sulfate in place of ammonium chloride did not improve the results (Scheme 3-16). Scheme 3 - 1 6 NH4C19 BUOH / \ I \ I \ + NH4OAC or ————> Recovery of Starting Materials OHC s S S CHO (NH4)2SO4 reflux 24hr (1 5 5 ) Condensation of the bismethylene amine was thought as an alternate route and it had been used by Dolphin and coworkers39 for the synthesis of porphocyanine(l63) by the self condensation of 5,5'-bis(aminomethyl)dipyrrylmethane(162) (Scheme 3-17). Some of research efforts was involved in the synthesis of the unknown macrocyclic compound 161 by the self condensation of 5,5"- bis(aminomethyl)-3',4'-dibutyl-2,2',5',2"terthiophene(l64) (Scheme 3-1 8). 115 Scheme 3-17 N 1)THF/CH30H reflux,N2 / \ l \ 2)02CHCl>rt “1'1ch2 N N CHzNHz o 2 2: H H \ N (162) \ (163) Scheme 3—18 I\ I\ I\ S S S I\ I\ /\ > HN NH HzNHzc s s s 012an ? \SI \SI \S/ (164) (165) 5,5"-Bis(aminomethyl)-3',4'-dibutyl-2,2',5',2"-terthiophene has been synthesized in three steps in an overall yield of 59% (Scheme 3- 19). 116 Scheme 3-19 lssscn\l\/\ /\/SS\I\ one fiHONHC S CHNOH (155) (167) /\ISS\I\ WW HZNHZCS 0121911:— (164) (168) a, NHzOH, EtOH; b, AczO; c, LiAlI-I4, THF 5,5"-Bis(aminomethyl)-3',4'-dibutyl-2,2',5',2"-terthiophene 164 is an orange oil which solidified when cooled in a refrigerator. The solid looks like wax and it is difficult to recrystalize. When treated with dilute HCI/HzO solution a dark-orange crystal formed which can be purified by recrystalization from ethanol. When 5,5"-bis(aminomethyl)-3',4'-dibutyl-2,2',5',2"- terthiophene was refluxed in THF/CH3OH (1:1) for 5 hours under N2, one of the products isolated is thought to be the high molecular weight polymeric material because it shows very dark-colored and low solubility (yield 45%). The other products are wax-like solids which was thought to be a mixture of low molecular weight polymer and some cyclized macrocycles (yield 41%) (Scheme 3-20). 117 Scheme 3-20 THF/CH30H(1:1) I \ I \ I \ I \ I\ I\ 5hr f-ngflz s aria-L— HZNHZC s s s €112an C S S (164) (169) /\ I\ I s s s + HN NH 8 s s \I \l \I (165) Air oxidation of the low molecular portion followed by double column chromatography and recrystalization from CH2C12/hexane gave the macrocyclic compound 166 in low yield (1.5%). Compound 166 is a purple luster crystal with a melting point of 254-255 °C (uncorrected). The UV—Vis maximum absorption is at 483nm. Scheme 3-21 118 Structurally, compound 166 is an azaannulene with 30 1t- electrons. By Huckel rule it is an aromatic compound and should exhibit diamagnetic ring current in 1H-NMR spectrum. However, our experiments showed that the diamagnetic ring current is very small because the chemical shifts of protons in compound 166, 8.21 ( s, 4H 3, 7.54 (d, J=4.4Hz, 4H) and 7.38(d, 4.4Hz, 4H) ppm. This low diamagnetic ring current is inconsistent with the prediction of aromatic nature of this compound. This might be correspondent to a nonplanar structure. Further research on elucidation of the structure of this compound is still necessary. Conclusions (1). Studies of the influence of heteroatom such as S, N, etc. on the properties of conductive polymers are very important for search of low bandgap organic conductors. In the studies of C=N double bound influences on the properties of conducting polymers, it has been shown that the incorporation of thiazolo[4,5-d]thiazole can lower the bandgap. In order confirm this effect, several new mixed thiophene oligomers containing thiazolo[4,5-d]thiazole have been synthesized and UV-Vis and other spectroscopic properties have been studied. (2). l,4-Diketones are important intermediate compounds for the syntheses of thiophenes, pyrroles, furans and other heterocyclic compounds. In the search of efficient and practical methods for the syntheses of l,4-diketones, it has been demonstrated that l,4- diketones can be synthesized by the oxidative coupling of trimethylsilyl enol ethers with ceric ammonium nitrate (CAN). This method has been shown to be a practical method for the syntheses of a variety of 1,4-diketones. VOCl3/Pyridine has been shown to be a new and efficient oxidation reagent for the syntheses of l,4-diketones via oxidative coupling of trimethylsilyl enol ethers. The reaction time is shorter compared with that using ceric ammonium nitrate as oxidation reagent. 119 120 (3). 1,3,4-Thiadiazoles based conductive polymers are important compounds which are stable at high temperature. During the research of syntheses of mixed thiophene oligomers and polymers which contain 1,3,4-thiadiazole, an efficient and practical method of one step synthesis of 2,5-diary-l,3,4-thiadiazoles has been discovered. The application of this method has been shown by the syntheses of several new mixed thiophene, furan and pyrrole oligomers which contain 1,3,4-thiadiazole. UV-Vis and other spectroscopic properties of these new compounds have been also studied. And UV-Vis spectra show that 1,3,4-thiadiazole increases the bandgap. (5). A new hexathiophene macrocycle which contains C=N bound has been synthesized in low yield (1.5%). lH-NMR shows there is not much aromatic property of this compound, which is inconsistent with the predictions of Huckel rule and MM2 calculation. Further research on the structure of this new compound is necessary. Experimental Section General: Pentane, hexane and petroleum ether were dried by distillation over CaCl2, discarded the first 10% forerun and stored in 500ml glass-stoppered bottles. Toluene was dried by distillation under argon over sodium-benzophenone ketyl. Triethylamine was dried by distillation under argon over calcium hydride. Ethanol was dried by distillation over magnesium. Acetonitrile was dried by distillation from calcium hydride and fractionated from P205 and stored over activated molecular sieves 3A in 100ml bottles. Dichloromethane and chloroform were dried by distillation over calcium hydride and redistillation from P205. Tetrahydrofuran was dried by distillation over calcium hydride and redistillation from potassium under argon. N,N-Dimethylformamide(DMF) was dried by stirring overnight with CaO and vacuum distillation (the first 10% forerun was discarded). Melting points were determined on a Thomas-Hoover capillary melting point apparatus and are uncorrected. Proton nuclear magnetic resonance (lH-NMR) spectra were obtained on a Varian Gemini 300 MHz and/or Varian VXR 500 MHz spectrometers. Chemical shifts are reported in parts per million (ppm) using the residual solvent proton resonance as the internal reference (acetone, 2.04; acetonitrile, 1.93; chloroform, 7.24; dichloromethane, 5.32; DMSO, 2.49; methanol, 3.30; tetrahydrofuran, 1.73). 1H-NMR data are 121 122 reported as follows: chemical shift multiplicity (s, singlet; br s, broad singlet; d, doublet, dd, doublet of doublets; t, triplet; q, quartet; m, multiplet), coupling constant (Hz), number of protons. 13C nuclear magnetic resonance (BC-NMR) spectra were recorded on a Varian Gemini (75.4 MHz) spectrometer. Chemical shift values are reported in parts per million using the solvent peak as the internal reference (acetone, 29.8; chloroform, 77.0; DMSO, 39.5; methanol, 49.0; tetrahydrofuran, 67.4). Infrared(IR) spectra were obtained from Nujol mull for solids or neat for liquids and recorded on a Nicolet IR/42 spectrometer. Ultraviolet and visible (UV—vis) spectra were recorded in dichloromethane or chloroform solution by using 1cm matched quartz cells with a Shimadzu UV-l60 spectrophotometer. EI mass spectra were obtained on a TRIO-1 spectrometer with El at 70 eV. High resolution maSs spectra were obtained on JOEL HX110 high resolution mass spectrometer in the mass facility at the department of biochemistry at Michigan State University. Synthesis of N,N'-dicyano(2-thienyl)methyl phenylene diamine(l3b): To a mixture of 2-thiophenecarboxaldehyde(2.24 g, 20.0 mmole), sodium cyanide(1.33 g, 20.5 mmole) and p-phenylene diamine(1.08 g, 10.0 mmole) in 20 ml of dry benzene was added 5 ml of acetic acid. The reaction mixture was stirred at room temperature for 24 hours and than quenched with saturated sodium bicarbonate solution. The yellow precipitate was filtered, washed with 5% aqueous sodium bicarbonate solution (2x20ml), 123 water(2x20 ml) and saturated sodium chloride solution (2x15 ml). The resulting yellow solid was dried in vacuum. Flash column chromatographic purification from silica gel with ethyl acetate/hexanes (35/65) as eluent gave 13b as a white solid. Yield 3.15 g (90%). mp. 157-158 °C (uncorrected). lH-NMR(DMSO-d5): 7.61(d, J=5.7Hz, 2H), 7.30(d, J=1.0Hz, 2H), 7.08(dd, J=5.7Hz, 1.0Hz, 2H), 6.77(s, 4H), 6.36(d, 11.3Hz, 2H), 6.l4(d, 11.3Hz, 2H); 13C-NMR(DMSO- d5): 45.6, 115.7, 119.1, 122.3, 126.3, 126.9, 127.0, 138.6; EI-MS, mlz(relative intensity): 350(M+, 1.06), 296(base), l47(14.1), 134(5.63), 115(19.5), 102(7.04), 77(5.41). Synthesis of 2,5-di(2-thienyl)thiazolo[5,4-d]thiazole(2lb): a) A mixture of 2-thiophenecarboxaldehyde (2.0 g, 17.8 mmole) and dithiooximide(l.0 g, 8.3 mmole) was heated neat at 170 0C under N2 for 30 min. The dark red reaction mixture was cooled to room temperature and the solid product was collected by filtration, washed with ice-cold methanol(2x10ml) and dried in vacuum. Column chromatographic purification over silica gel with ethyl acetate/hexanes(35/65) as eluent followed by crystallization from ethyl acetate/ethanol(50/50) gave the 2,5-di(2-thienyl)thiazolo[5,4- d]thiazole(21b) as yellow needles. Yield, 1.04 g (41%). m.p.=236-238 °C (uncorrected). 1H-NMR(DMSO-d6): 7.58(dd, J=4.1Hz, 1.0Hz, 2H), 7.47(dd, J=5.4Hz, 1.0Hz, 2H), 7.12(dd, J=5.4Hz, 4.1Hz); EI-MS, mlz(relative intensity): 308(M++2, 11.2), 307(M*+1, 10.7), 306(M+, 61.4), 153(4.35), 127(4.38), 109(14.9), 90(13.8), I24 89(5.04), 88(base), 69(7.73), 45(11.4); UV-Vis(maximum absorption): 388nm (CHCl3). b) A mixture of 2-thiophene carboxaldehyde (6.0 g, 53.3 mmole) and dithiooximide (1.0 g, 8.3 mmole) in 10 ml DMF was heated at reflux under N2 for 40 minutes. The dark red reaction mixture was cooled and the precipitated product was collected by filtration, washed with water (2x20 ml) and ice-cold methanol (3x10 ml). Then the yellow solid was dried in vacuum. Column chromatographic purification over silica gel with ethyl acetate/hexanes(35/65) as eluent followed by crystallization from ethyl acetate/ethanol (50/50) gave the product as yellow needles. Yield, 2.45 g (32%). All the spectroscopic characterizations are the same as those from method(a). Synthesis of 2,5-di(2-furanyl)thiazolo[5,4-d]thiazole(21c): a) A mixture of 2-furan carboxaldehyde (1.21 g, 12.6 mmole) and dithiooximide (0.74 g, 6.17 mmole) was heated neat at 170 °C under N2 for 35min. The dark red reaction mixture was cooled and the solid product had been collected by filtration, washed with ice- cold MeOH (2x10 ml) and dried in vacuum. Column chromatographic purification over silica gel with ethyl acetate/hexanes(35/65) as eluent followed by crystallization from ethyl acetate/ethanol(50/50) gave the product as yellow needles. Yield, 0.63 g (37%). m.p.=240- 241 °c (tit.S 238-240 °C). ‘H-NMR(DMSO-d5): 7.55(dd, J=3.4Hz, 0.7Hz. 125 2H), 7.08(dd, J=4.8Hz, 0.7Hz, 2H), 6.59(dd, J=4.8Hz, 3.4Hz); EI-MS, mlz(relative intensity): 276(M++2, 10.4), 275(M++1, 15.8), 274(M+, base), 246(7.55), 137(12.3), lll(l4.9), 93(ll.4), 88(98.8), 64(9.32), 39(11.0). UV-Vis(maximum absorption): 380nm (CHCl3). b) A mixture of 2-furan carboxaldehyde (3.0 g, 31.3 mmole) and dithiooximide(l.8 g, 15.0 mmole) in 10 ml DMF was heated at reflux under N2 for 30 min. The dark red reaction mixture was cooled and the precipitated product was collected by suction filtration, washed with water(2x20ml) and ice-cold methanol (3x10 ml). Then the yellow solid was dried in vacuum. Column chromatographic purification over silica gel with ethyl acetate/hexanes (35/65) as eluent followed by crystallization from ethyl acetate/ethanol (50/50) gave the product as yellow needles. Yield, 1.29 g (31%). All the physical properties are the same as those from method (a). Synthesis of 2,5-di(1-phenylsulfonyl-2-pyrryl)thiazolo[5,4- d]thiazole(26): A mixture of 1-phenylsulfonyl-2-pyrrole carboxaldehyde(25) (2.35 g,10.0 mmole) and dithiooximide (0.59 g, 4.9 mmole) in 20 ml DMF was heated at reflux under N2 for 40 min. The dark red reaction mixture was cooled and the precipitated product was collected by suction filtration, washed with water (2x20 ml) and ice-cold methanol (3x10 ml). Then the solid was dried in vacuum to give a 126 tan solid as crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes/CH2C12 (50/20/30) as eluent followed by crystallization from ethyl acetate/ethanol/hexanes (60/25/15) gave the product as light tan solid. Yield, 2.70 g (25%). m.p. 276-278 °C (decomp.). lH-NMR(DMSO-d5): 7.90(d, J=7.4Hz, 4H), 7.76(dd, J=4.1Hz, 1.6Hz, 2H), 7.50-7.39(m, 6H), 7.07(dd, J=3.9Hz, 1.6Hz, 2H), 6.32(dd, J=4.1Hz, 3.9Hz, 2H). 13C-NMR(DMSO-d6): 159.1, 148.7, 137.9, 133.0, 132.4, 129.5, 128.1, 127.8, 123.2, 110.1; high resolution mass spectra: calcd for C24H16N4O4S4, 552.648, found: 552.496. Synthesis of 2,5-di(2-pyrryl)thiazolo[5,4-d]thiazole(2la): A mixture of 2,5-di(1-phenylsulfonyl-2-pyrryl)thiazolo[5,4- d]thiazole(26)(1.5 g, 2.7 mmole), sodium hydroxide (0.3 g, 7.5 mmole) in 100ml of ethanol was refluxed for 12 hours. Then the reaction mixture was cooled and the ethanol was removed by a rotary evaporator. The residue was extracted with chloroform (4x25 ml) and the combined chloroform was washed with water (3x15 ml) and saturated aqueous sodium chloride solution (20 ml), dried over sodium sulfate. The organic solvent was removed by a rotary evaporator to give a dark brown solid as the crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (25/75) as the eluent followed by crystallization from ethyl acetate/ethanol (SO/50) gave the product as yellow powders. Yield, 0.53 g (72%). m.p.=251-253 °C 127 (uncorrected). lH-NMR(DMSO-d6): 12.1(s, br., 2H), 7.21(m, 2H), 7.01(m, 2H), 6.28(m, 2H); 13C-NMR(DMSO-d5): 153.8, 147.6, 132.8, 128.4, 120.1, 110.3; high resolution mass spectra: calculated for C12H3N4S2, 272.344, found: 272.391; UV-Vis maximum absorption: 391nm (CHCl3). Synthesis of 2,5-di(2-thienyl)-1,3,4-thiadiazole(33): A mixture of 2-thiophene carboxaldehyde (3.6 g, 32.1 mmole), hydrazine monohydrate (0.77 g, 15.5 mmole), elemental sulfur (1.1 g, 34.4 mmole), and tributylamine (0.3 g, 1.6 mmole) in 20ml of propylene glycol was heated at 130 0C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was filtered by suction filtration. The solid was washed with ice-cold methanol (3x20 ml) and carbon disulfide (3x15 ml); dried in vacuum to give a yellow solid as crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (35/65) as eluent followed by crystallization from ethanol/ethyl acetate (SO/50) gave the 2,5-di(2-thienyl)-1,3,4-thiadiazole(33) as yellow needles. Yield: 3.49 g (90%). m.p.=155-156 °C (uncorrected). lH-NMR(DMSO- d5): 7.86(dd, J=5.6Hz, 1.3Hz, 2H), 7.77(dd, J=4.2Hz, 1.3Hz, 2H), 7.24(dd, J=5.6Hz, 4.2112, 2H); 13C-NMR(DMSO-d5): 160.3, 130.5, 130.3, 130.1, 128.1; EI-MS, mlz(relative intensity): 252(M*+2, 18.2), 251(M++1, 19.1), 250(M", base), 221(5.6), l78(7.7), 177(10.5), 143(8.9), 142(7.3), 141(84.8), 129(11.6), 127(94.9), ll4(9.3), 109(23.4), 97(15.2), 96(11.6), 83(21.1), 82(11.5), 71(18.l), 70(13.5), 128 69(57.6), 58(14.3), 45(31.4), 39(19.7). UV-Vis(maximum absorption): 342nm (CHCl3). Synthesis of 2,5-di(2-furanyl)-1,3,4-thiadiazole(34): A mixture of 2-furan carboxaldehyde (3.0 g, 31.2 mmole), hydrazine monohydrate( 0.78 g, 15.6 mmole), elemental sulfur (1.1 g, 34.4 mmole), and tributylamine (0.3 g, 1.6 mmole) in 20ml of propylene glycol was heated at 110°C for 5 days. Then, the light brown colored reaction mixture was cooled to room temperature and the precipitate was filtered by suction filtration. The solid was washed with ice-cold methanol (3x20 ml) and carbon disulfide (3x15 ml); dried in vacuum. Column chromatographic purification of the crude product from silica gel with ethyl acetate/CH2Cl2/hexanes (20/10/70) as the eluent followed by crystallization from ethanol/ethyl acetate (50/50) gave the 2,5-di(2-furanyl)-l,3,4- thiadiazole(34) as yellow needles. Yield: 0.51 g (15%). m.p.=l48-151 °C. ‘H-NMR(DMSO-d6): 8.01(dd, 1:23, 0.6Hz, 2H), 7.38(dd, 14.0112, 0.6Hz, 2H), 6.79(dd, J=4.0Hz, 2.3112, 2H); 13C-NMR(DMSO-d5): 156.0, 145.9, 143.6, 112.4, 112.0; EI-MS, mlz(relative intensity): 218(M", base), 189(4.7), 125(70.4), 111(15.6), 93(17.4). Synthesis of 2,5 -di( 1 -phenylsulfonyl-2-pyrryl)- 1,3 ,4- thiadiazole(38): 129 A mixture of 1-pheny1sulfonyl-2-pyrrole carboxaldehyde(25) (3.1 g, 13.2 mmole), hydrazine monohydrate(0.33 g, 6.6 mmole), elemental sulfur (1.54 g, 48.1 mmole) and tributylamine (0.2 g, 1.1 mmole) in 50 ml propylene glycol was kept at 120 °C with magnetic stirring for two days. The dark colored reaction mixture was cooled and the precipitate was collected by suction filtration. The solid was washed with ice-cold methanol (3x20 ml) and carbon disulfide (3x15 ml); dried in vacuum. Column chromatographic purification of the crude product over silica gel with ethyl acetate/CH2Cl2/hexanes (40/10/50) as the eluent followed by crystallization from ethanol gave a light tan solid product. Yield: 2.0 g (61%). mp. 240-242 °C (decomp.). 1H-NMR(DMSO-d(s): 7.86(dd, J=7.3Hz, 2.0Hz, 4H), 7.72(dd, J=4.1Hz, 1.5Hz, 2H), 7.45-7.21(m, 6H), 7.01(dd, J=3.9Hz, 1.5Hz, 2H), 6.29(dd, J=4.1Hz, 3.9112, 211); 13C-NMR(DMSO-d5): 160.4, 142.3, 138.7, 132.9, 128.6, 128.0, 124.6, 118.1; high resolution mass spectra, calculated for C22H15N4O483, 496.568; Found: 496.497. Synthesis of 2,5-di(2-pyrryl)-1,3,4-thiadiazole(36a): A mixture of 2,5-di(l-phenylsulfonyl-Z-pyrryl)-l,3,4- thiadiazole(38) (2.0 g, 4.0 mmole), sodium hydroxide (0.6 g, 15.0 mmole) in 50 ml of ethanol was kept at reflux for 12 hours. Then the reaction mixture was cooled and the ethanol was removed by a rotary evaporator. The residue was extracted with chloroform 130 (4x25 ml) and the combined chloroform was washed with water (3x15 ml) and saturated NaCl, dried over sodium sulfate. The organic solvent was removed by a rotary evaporator to give a dark brown solid as the crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (25/75) as the eluent followed by crystallization from ethyl acetate/ethanol (50/50) gave the product as yellow needles. Yield: 0.77 g (89%). m.p.=168-169 °C (uncorrected). 1H-NMR(CDCL3): 12.0(s, br., 2H), 7.09(m, 2H), 6.98(m, 2H), 6.30(m, 211); 13C-NMR(CDCL3): 158.1, 137.8, 129.1, 124.0, 114.5; high resolution mass spectra, calculated. for C10H3N4S, 216.264, found, 216.304. UV-Vis maximum absorption: 351nm (CHCl3). Synthesis of 2,5 -di(4-pyridyl)-l ,3,4-thiadiazole(48): A mixture of 4-pyridine carboxaldehyde (3.4 g, 31.8 mmole), hydrazine monohydrate (0.79 g, 15.8 mmole), elemental sulfur (1.95 g, 61.0 mmole), and tributylamine (0.3 g, 1.6 mmole) in 40 ml of propylene glycol was heated at 130 °C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was filtered by suction filtration. The solid was washed with ice-cold methanol (3x20 ml) and carbon disulfide (3x15 ml); dried in vacuum to give a yellow solid as crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (40/60) as eluent followed by crystallization from ethanol/ethyl acetate (SO/50) gave the 2,5-di(4-pyridyl)-l,3,4-thiadiazole(48) as yellow plates. Yield: 2.88 g (76%). m.p.=229-230 °c (decomp.). ‘H-NMR(DMSO-d5): 131 8.82(d, J=7.7Hz, 211), 8.02(d, J=7.7Hz, 2H); 13C-NMR(DMSO-d5): 166.8, 150.4, 135.4, 120.9; EI-MS, mlz(relative intensity): 242(M*+2, 6.35), 241(M++1, 18.4), 240(M”, base), 138(4.66), 137(7.94), 136(92.3), 122.0(35.1), 109(13.1), 104(32.2), 78(58.0), 77(15.6), 63(11.6), 51(53.0), 50(16.3). UV-Vis(maximum absorption): 292nm (CHCl3). Synthesis of 2,5-di(6-methyl-2-pyridyl)-1,3,4-thiadiazole(50): A mixture of 6-methyl-2-pyridine carboxaldehyde (3.8 g, 31.4 mmole), hydrazine monohydrate (0.78 g, 15.6 mmole), elemental sulfur (2.0 g, 62.5 mmole), and tributylamine (0.31 g, 1.7 mmole) in 30ml of propylene glycol was heated at 130 °C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was filtered by suction filtration. The solid was washed with ice-cold methanol (3x20 ml) and carbon disulfide (3x15 ml); dried in vacuum to give a yellow solid as crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (30/70) as eluent followed by crystallization from ethanol/ethyl acetate (50/50) gave the 2,5-di(3-methy1-2-pyridyl)- l,3,4-thiadiazole(50) as yellow needles. Yield: 3.43 g (82%). m.p.=156-157 °c (uncorrected). 1H-NMR(DMSO-d6): 8.09(d, J=8.4Hz, 2H), 7.91(t, J=8.5Hz, 2H), 7.44(d, J=8.5Hz, 2H), 2.56(s, 6H); 13C- NMR(DMSO-d6): 170.6, 158.3, 146.9, 137.4, 125.0, 116.9, 23.2; EI-MS, mlz(relative intensity): 268(M”, 9.33), 258(26.8), 256(73.7), 194(8.76), 192(33.2), 162(12.9), 160(56.2), 130(12.8), 128(65.9), 96(30.4), 66(13.6), 64(base). UV-Vis(maximum absorption):264nm, 282nm(shoulder) (CHClg). 132 Synthesis of 2,5-diphenyl-1,3,4-thiadiazole(52a): A mixture of benzaldehyde (5.2 g, 49 mmole), hydrazine monohydrate (1.2 g, 24 mmole), elemental sulfur (3.0 g, 94 mmole), and tributylamine (0.5 g, 1.7 mmole) in 30ml of propylene glycol was heated at 130 °C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was filtered by suction filtration. The solid was washed with ice-cold methanol (3x20 m1) and carbon disulfide (3x15 ml); dried in vacuum to give a yellow solid as crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (35/65) as eluent followed by crystallization of the crude product from ethanol/ethyl acetate (50/50) gave the 2,5-diphenyl-1,3,4-thiadiazole(52a) as white plates. Yield: 4.74 g (83%). m.p.=138-139 °c (uncorreted). l11- NMR(DMSO-d6): 8.02(m, 411), 7.58(m, 6H); 13C-NMR(DMSO-d5): 167.3, 130.9, 128.9, 128.8, 127.0; EI-MS, mlz(relative intensity): 240(M"+2, 7.21), 239(M"+1, 20.8), 238(M”, 96.5), 165(8.66), l37(7.02), 136(12.9), 135(base), 121(50.0), 119(6.13), 108(10.2), 103(24.0), 91(10.8), 89(5.94), 78(7.92), 77(90.6), 76(14.4), 63(11.0), 51(28.0); UV-Vis(maximum absorption): 307nm (CHCl3). Synthesis of 2,5-di(4-methoxylphenyl)-1,3,4-thiadiazole(52b): A mixture of 4-methoxylbenzaldehyde (3.3 g, 24.3 mmole), hydrazine monohydrate(0.6 g, 12.0 mmole), elemental sulfur (1.63 g, 50.9 mmole), and tributylamine (0.4 g, 2.2 mmole) in 30 m1 of 133 propylene glycol was heated at 130 °C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was filtered by suction filtration. The solid was washed with ice-cold methanol (3x20 ml) and carbon disulfide (3x15 m1); dried in vacuum to give a yellow solid as crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (35/65) as eluent followed by crystallization from ethanol/ethyl acetate (50/50) gave the 2,5-di(4-methoxylphenyl)-1,3,4-thiadiazole(52b) as yellow solid. Yield: 3.0 g (84%). m.p.=159-160 °C (uncorrected). lH- NMR(DMSO-d5): 7.95(dd, J=7.6Hz, 2.2Hz, 4H), 7.12(dd, J=7.6Hz, 2.2Hz, 411), 3.86(s, 6H); l3C-NMR (DMSO-d6): 166.3, 160.9, 129.2, 121.7, 114.9; EI-MS, m/z (relative intensity): 300(M++2, 9.56), 299(M*+1, 26.4), 298(M+, base), l65(44.4), 152(10.8), 151(59.6), 150(69.3), 149(10.6), 136(13.0), 133(32.0), 122(28.2), 108(12.2), 90(13.4),. 76(9.11), 63(11.8); UV-Vis(maximum absorption): 329nm (CHC13). Synthesis of 2,5-di(4-hydroxylphenyl)-l ,3,4-thiadiazole(520): A mixture of 4-hydroxylbenzaldehyde (2.8 g, 23.0 mmole), hydrazine monohydrate (0.58 g, 11.6 mmole), elemental sulfur (1.6 g, 23.0 mmole), and tributylamine (0.4 g, 2.1 mmole) in 25 m1 of propylene glycol was heated at 130 °C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was filtered by suction filtration. The solid was washed with ice-cold methanol (3x20 ml) and carbon disulfide (3x15 ml); dried in vacuum to give a yellow solid as crude product. Column chromatographic 134 purification over silica gel with ethyl acetate/hexanes (35/65) as eluent followed by crystallization from ethanol/ethyl acetate (50/50) gave the 2,5-di(4-hydroxylphenyl)-1,3,4-thiadiazole(52c) as yellow solid. Yield:2.63 g (84%). m.p.=206-208 °C (uncorrected). lH- NMR(DMSO-d5): 10.2(s, 2H), 7.81(dd, J=7.5, 2.3Hz, 4H), 6.92(dd, J=7.5, 2.3Hz, 4H); l3C-NMR (DMSO-d6): 166.0, 160.2, 129.3, 120.7, 116.2; EI- MS, mlz(relative intensity): 272(M++2, 6.43), 271(M++1, 18.2), 270(M+, base), 153(5.67), 152(10.4), 151(95.7), 139(3.10), l40(4.50), l37(56.8), 122(5.80), 120(7.33), 119(43.2), 105(5.22), 93(6.43), 65(37.4), 64(11.9), 63(10.9), 51(12.l), 39(16.2); UV-Vis (maximum absorption): 349nm (CHCl3). Synthesis ' of 1-(2-thienyl)ethenyl-1-oxytrimethylsilane(67a): In a 250 ml round bottom flask was charged 5.1 g dry NaI (35.2 mmole) and 100 ml dry acetonitrile. The mixture was stirred at room temperature until all the sodium iodide dissolved. Then 3.8 g of trimethylchlorosilane (35.2 mmole) was added by a syringe and the mixture was stirred at room temperature for about 10 minutes. Then 3.56 g of dry triethyl amine (35.2 mmole) was added to the flask at one batch with vigorously stirring, followed by dropwise addition of 3.9 g of thienyl methyl ketone (31.0 mmole) in 5 ml dry acetonitrile. The brown-colored mixture was continually stirred at room temperature overnight. Then, 100 ml 5% sodium bicarbonate solution was added. The organic layer was separated and the aqueous layer was extracted with ether (3x20 ml). The combined 135 ether extracts were washed with 2% ice-cold HCI (2x20 ml), H2O (2x20 ml) and saturated NaCl (30 ml), dried with Na2SO4. Removal of the solvent with rotary evaporator gave a brown oil as a crude product. lH-NMR shows that it contains 97.3% silyl enol ether (67a) and 2.7% of the starting ketone. Yield: 5.83 g (96% based on the conversion of 2-thienyl methyl ketone). ‘H-NMR(CDC13): 7.15(d, J=4.9Hz, 2H), 6.97(t, J=4.9Hz, 1H), 4.83(d, J=2.1Hz, 1H), 4.33(d, J=2.1Hz, 1H), 0.29(s, 9H). Synthesis of 1-(2-thienyl)propenyl-l-oxytrimethylsilane(67b): In a 250 ml round bottom flask was charged 6.5 g dry NaI (44.8 mmole) and 150 ml dry acetonitrile. The mixture was stirred at room temperature until all the NaI dissolved. Then 4.86 g of t1‘in'lethylchlorosilane (44.8 mmole) was added by a syringe and the mixture stirred at room temperature for about 10 minutes. Then 4-53 g of dry Et3N (44.8 mmole) was added to the flask at one batch with vigorously stirred, followed by dropwise addition of 4.9 g of thivmlyl ethyl ketone (35 mmole) in 10 ml dry acetonitrile. The bl'Ovvn-colored mixture was continually stirred at room temperature °Vernight. Then, 50 ml of 5% NaHCO3 was added. The organic layer Was separated and the aqueous layer was extracted with ether (3x30 "11). The combined ether extracts were washed with 2% ice-cold HCl (2x25 ml), 1120 (2x25 ml) and saturated NaCl (30 ml), dried with Na2804. Removal of the solvent with a rotary evaporator gave a bl'Own oil as the crude product. lH--NMR shows that it contains 95.0% 136 silyl enol ether(67b) and 5.0% of the starting ketone. Yield: 6.92 g (94.7% based on the conversion of 2-thienyl ethyl ketone). lH- NMR(CDCL3): 7.09(dd, J=4.3Hz, 0.9Hz), 7.01(dd, J=3.7Hz, 0.9Hz, 1H), 6.92(dd, J=4.3Hz, 3.7Hz, 1H), 5.3l(q, J=7.7Hz, 1H), 1.70(d, J=7.8Hz, 3H) O.21(s, 9H). Synthesis of 1-(2-thienyl)butenyl-l~oxytrimethylsilane(67c): In a 500 ml round bottom flask was charged 9.0 g dry Nal (62.1 mmole) and 150 ml dry acetonitrile. The mixture was stirred at room temperature until all the Nal dissolved. Then 6.73 g of trimethylchlorosilane (62.1 mmole) was added by a syringe and the mixture was stirred at room temperature for about 10 minutes. Then 6.37 g of dry triethyl amine (63.0 mmole) was added to the flask at one time with vigorously stirring, followed by dropwise addition of 8.47 g of thienyl propyl ketone (55.0 mmole) in 10 ml dry acetonitrile. The brown-colored mixture was continually stirred at room temperature overnight. Then 100 ml of 5% NaHCO3 was added and the organic layer was separated. The aqueous layer was extracted with ether (3x30 ml) and the combined ether layers were washed with 2% ice-cold HCl (2x30 ml), H20 (2x30 ml) and saturated NaCl (35 ml), dried with Na2SO4. Removal of the solvent in rotary evaporator gave a brown oil as the crude product. 1H-NMR shows that it contains 94.9% silyl enol ether(67c) and 5.1% of the starting ketone. Yield: 11.38 g (92.8% based on the conversion of 2-thienyl 137 propyl ketone). 1H-NMR(CDC13): 7.10(dd, J=4.4Hz, 0.9Hz, 1H), 7.03(dd, J=3.6Hz, 0.9Hz, 111), 6.91(dd, J=4.4Hz, 3.6Hz, 1H), 5.32(t, J=7.7Hz, 111), 2.14(m, 2H), 1.37(t, J=7.8Hz, 311), 0.25(s, 911). Synthesis of 1-(2-thienyl)hexenyl-l-oxytrimethylsilane(67d): In a 500 ml round bottom flask was charged 10.7 g dry Nal (73.8 mmole) and 250 ml dry acetonitrile. The mixture was stirred at room temperature until all the Nal dissolved. Then 8.0 g of trimethylchlorosilane (73.8 mmole) was added by a syringe and the mixture was stirred at room temperature for about 10 minutes. Then 7.46 g of dry triethyl amine (73.8 mmole) was added to the flask at one time with vigorously stirring, followed by dropwise addition of 12 g of 2-thienyl pentyl ketone (66.0 mmole) in 20 ml dry acetonitrile. The brown-colored mixture was continually stirred at room temperature overnight. Then, 100ml of 5% NaHCO3 aqueous solution was added and the organic layer was separated. The aqueous layer was extracted with ether (3x30 ml), and the combined ether layers were washed with 2% ice-cold HCI (2x50 ml), H2O (2x50 ml) and saturated NaCl (50 ml); dried with Na2SO4. Removal of the solvent by a rotary evaporator gave a brown oil as the crude product. lH-NMR shows that it contains 95.7% silyl enol ether(67d) and 4.3% of the starting ketone. Yield: 15.7 g (95% based on the conversion of 2-thienyl pentyl ketone). 1H-NMR(CDC13): 7.l3(dd, J=4.2Hz, 1.1Hz, 1H), 7.05(dd, J=3.6Hz, 1.1Hz, 1H), 6.97(dd, J=4.0Hz, 138 3.6Hz, 1H), 5.26(t, J=8.0Hz, 1H), 2.18(m, 2H), l.49-1.34(m, 4H), 0.95(t, J=7.8Hz, 3H), 0.27(s, 9H). Synthesis of 1-(2-thienyl)octenyl- 1 -oxytrimethylsilane(67e): In a 500 ml round bottom flask was charged 8.7 g dry Nal (60.0 mmole) and 200 ml dry acetonitrile. The mixture was stirred at room temperature until all the Nal dissolved. Then 6.5 g of trimethylchlorosilane (60.0 mmole) was added by a syringe and the mixture was stirred at room temperature for about 10 minutes. Then 6.06 g of dry triethyl amine (60.0 mmole) was added to the flask at one time with vigorously stirring, followed by dropwise addition of 11.1 g of thienyl heptyl ketone (52.8 mmole) in 20ml dry acetonitrile. The brown-colored mixture was continually stirred at room temperature overnight. Then, 100 ml of 5% NaHCO3 aqueous solution was added and the organic layer 'was separated. The aqueous layer was extracted with ether (3x30 ml). The combined ether layers were washed with 2% ice-cold HCI (2x40 ml), H2O (2x40 ml) and saturated NaCl (50 ml); dried with Na2SO4. Removal of solvent with a rotary evaporator gave a brown oil as the crude product. lH-NMR shows that it contains 96.0% of the silyl enol ether(67e) and 4.0% of the starting ketone. Yield: 13.95 g (94.5% based on the conversion of 2-thienyl heptyl ketone). lH-NMR(CDC13): 7.06(dd, J=4.4Hz, 0.8Hz, 1H), 7.00(dd, J=3.7Hz, 0.8Hz, 1H), 6.95(dd, J=4.4Hz, 3.7Hz, 1H), 5.28(t, J=7.8Hz, 1H), 2.16(m, 2H), 1.79(m, 2H), 1.39(m, 6H), 0.94(t, J=7.7Hz, 3H), '0.24(s, 9H). 139 Synthesis of 1,4-di(2-thienyl)-1,4-butanedione(60a): a) Synthesis of 1,4-di(2-thienyl)-1,4-butanedione(60a) by the oxidation of 2-thienyl silyl ethenol ether(67b) with ceric ammonium nitrate. A silyl enol ether(67a) (4.3 g, 21.7 mmole) in 20 ml dry acetonitrile was added dropwise with vigorously stirring to a mixture of 12 g ceric ammonium nitrate (22.0 mmole), 3.77 g NaHCO3 (44.7 mmole) and 150 ml dry acetonitrile in a 500 ml round bottom flask under N2. After addition the reaction was continued at room temperature for four more hours and then quenched with water. The product was extracted with chloroform (4x30 ml) and the combined chloroform layers were washed with water (2x30 ml) and dried with N a2SO4. Removal of the solvent by rotary evaporator gave a light- brown residue as the crude 1,4-diketone. Column chromatographic purification over silica gel with ethyl acetate/hexanes (25/75) as the eluent followed by crystallization from hexanes/CH2C12 (90/10) gave the product as colorless needles. mp. 131-132 °C (uncorrected) (lit.73°> 130-131 °C). Yield: 1.50 g (55% based on the starting ketone). 1H-NMR(CDC13): 7.81(dd, J=4.3Hz, 1.2Hz, 2H), 7.64(dd, J=5.1Hz, 1.2Hz, 2H), 7.13(dd, J=5.1Hz, 4.3Hz), 3.38(s, 4H); 13C-NMR(CDC13): 190.0, 143.3, 133.2, 131.7, 127.7, 32.7; EI-MS, mlz(relative intensity): 250(M+, 11.7), 139(17.0), 113(5.99), 112(7.66), lll(base), 83(8.51), 55(4.22), 39(20.7). 140 b) Synthesis of 1,4-di(2-thienyl)-l,4-butanedione(60a) by the oxidation of 2-thienyl silyl ethenol ether(67a) with vanadium trichloride oxide Silyl enol ether(67a) 1.85 g (with 94.5% pure) (9.3 mmole) in 5 ml dry acetonitrile was added to a mixture of 1.62 g of VOCl3 (1.0 e.q) in 20 ml dry acetonitrile at room temperature under N2. After the addition, the reaction was continued for 15 more minutes. Then, the dark-red mixture was quenched with 10ml ice-cold 5% NaHCO3 aqueous solution. The organic layer was separated and the aqueous layer extracted with ether (2x10 ml). The combined organic layers were washed with H2O (2x10 ml), saturated NaCl (10 ml) and dried with Na2804. Removal of the solvent gave a light brown colored crude l,4-diketone. Column chromatographic purification over silica gel with ethyl acetate/hexanes (25/75) as the eluent followed by crystallization from hexanes gave the expected l,4-diketone(60a) as colorless needles. All the physical properties are the same as those from method(a). Yield: 0.57 g (49% based on the starting ketone). Synthesis of 2,3-dimethyl-1,4-di(2-thienyl)-l,4-butanedione(60b): a) Synthesis of 2,3-dimethyl-1,4-di(2-thienyl)-1,4- butanedione(60b) by the oxidation of thienyl silyl-l-propenol ether(67b) with ceric ammonium nitrate. 141 A silyl enol ether(67b) (6.15 g, 29.0 mmole) in 20 ml dry acetonitrile was added dropwise with vigorously stirring to a mixture of 16 g ceric ammonium nitrate (29.3 mmole), 5.02 g NaHCO3 (59.6 mmole) and 200 ml dry acetonitrile in a 500 ml round bottom flask under nitrogen. After the addition of the reagents, the reaction was continued at room temperature for four more hours. Then the reaction was quenched with water. The product was extracted with chloroform (4x30 ml). The combined organic layers were washed with water (3x30 ml) and dried with Na2SO4. Removal of the solvent by a rotary evaporator gave a light-brown residue as the crude product. lH-NMR shows that it is a mixture of diasteromers. Column chromatographic purification over silica gel with ethyl acetate/hexanes (20/80) as the eluent followed by crystallization from hexanes gave one of the diastereomers as colorless needdles. m.p.=124-126 °C (uncorrected) (lit.73°)123-125 °C). Continuing eluting with the same solvent gave the other isomers. Total yield of 1,4- diketones: 2.53 g (65% based on the starting ketone). lH-NMR(CDC13): 7.84(dd, J=4.3Hz, 1.2Hz, 2H), 7.69(dd, J=5.4Hz, 1.2Hz, 2H), 7.17(dd, J=5.4, 4.3112, 211), 3.76(m, 2H), 1.17(d, J=7.3Hz, 6H); 13C-NMR(CDC13): 196.4, 146.0, 134.6, 132.6, 128.3, 49.8, 30.1; EI-MS, mlz(relative intensity): 278(M+, 6.96), 263(1.36), 167(9.80), 153(9.02), 140(75.3), 128(11.5), 111(base), 83(38.0), 68(5.98), 56(34.l), 45(19.4), 39(69.0); 142 b) Synthesis of 2,3-dimethyl-l,4-di(2-thienyl)-1,4- butanedione(60b) by the oxidation of thienyl silyl-l-propenol ether(67b) with vanadium trichloride oxide A silyl enol ether(67b) 2.26 g (with 97.1% pure) (10.6 mmole) in 5 ml dry MeCN was added to a mixture of 1.84 g of VOC13 (1.0 e.q) in 20 ml dry acetonitrile at room temperature under N2. After the addition, the dark-red mixture was quenched with 20 ml ice-cold 5% N aHC03 aqueous solution. The organic layer was separated and the aqueous layer was extracted with ether (2x20 ml). The combined organic layers were washed with H2O (2x20 ml), saturated NaCl (20 ml) and dried with sodium sulfate. Removal of the solvent gave a light brown colored crude 1,4-diketone as a mixture of diasteromers; Column chromatographic purification over silica gel with ethyl acetate/hexanes (20/80) as the eluent followed by crystallization from hexanes gave the expected l,4-diketone. All the physical properties are the same as those from method(a). Total yield: 0.84 g 57% based on the starting ketone). Synthesis of 2,3-diethyl-1,4-di(2-thienyl)-1,4-butanedione(60c): a) Synthesis of 2,3-diethyl-1,4-di(2-thienyl)-1,4- butanedione(60c) by the oxidation of thienyl silyl-l-butenol ether(67c) with ceric ammonium nitrate. 143 A silyl enol ether(67c) (10.0 g, 44.2 mmole) in 30 ml dry acetonitrile was added dropwise with vigorously stirring to a mixture of 24 g ceric ammonium nitrate (44.0 mmole), 7.53 g NaHCO3(89.3 mmole) and 200 ml dry acetonitrile in a 500 ml round bottom flask under nitrogen. After the addition the reaction was continued at room temperature for four more hours and then quenched with water. The product was extracted with chloroform (4x30 ml) and the combined organic layers were washed with water (3x20 ml) and dried with sodium sulfate. Removal of the solvent by a rotary evaporator gave a light-brown residue as the crude 1,4-diketone. 1H- NMR shows it is a mixture of diastereomers. Column chromatographic purification over silica gel with ethyl acetate/hexanes (18/82) followed by crystallization from hexanes/CH2C12 (85/15) and recrystallization from hexanes gave one of the diastereomers as colorless needdles. Yield: 1.4 g. m.p.=147-149 °C (uncorrected). Continued eluting with the same solvent gave the other isomers. Total yield of l,4-diketones: 4.06 g (60% based on the starting ketone). lH-NMR(CDC13,): 7.84(dd, J=4.3, 1.2Hz), 7.70(dd, J=5.5, 1.2Hz, 2H), 7.16(dd, J=5.5, 4.3Hz), 3.75(m, 2H), 1.64(m, 2H), 1.35(m, 2H), 1.07(t, J=7.9Hz, 6H); ‘3C-NMR(CDC13): 196.5, 146.1, 134.6, 132.5, 128.4, 49.7, 31.2, 27.0; EI-MS, mlz(relative intensity): 306(M“, 1.96), 277(1.87), 195(8.90), 167(9.74), 154(47.3), 111(base), 83(17.4). IR: 144 b) Synthesis of 2,3-diethy1-1,4-di(2-thieny1)-1,4- butanedione(60c) by the oxidation of thienyl silyl-l-butenol ether(67c) with vanadium trichloride oxide A silyl enol ether(67c) 2.08 g (with 96.4% pure) (9.2 mmole) in 5 ml dry acetonitrile was added to a mixture of 1.60 g of VOC13 (1.0 e.q.) in 20 ml dry acetonitrile at room temperature under N2. After the addition, the dark-red mixture was quenched with 10 ml ice-cold 5% NaHCO3 aqueous solution. The organic layer was separated and the aqueous layer was extracted with ether (2x20 ml). The combined organic layers were washed with H20 (2x20 ml), saturated NaCl (20 m1) and dried with sodium sulfate; Removal of the solvent gave a light brown colored crude 1,4-diketone as a mixture of diastereomers; Column chromatographic purification over silica gel with ethyl acetate/hexanes (18/82) as the eluent followed by crystallization from hexanes/CH2C12 (85/15) and recryctallization from hexanes gave one of the diastereoisomers as colorless needle. All the physical properties are the same as those from method (a).Total yield of l,4-diketones: 0.73 g (52% based on the starting ketone). Synthesis of 2,-3-dibutyl-1,4-di(2-thienyl)-1,4-butanedione(60d): a) Synthesis of 2,-3-dibuty1-1,4-di(2-thienyl)-l,4- butanedione(60d) by the oxidation of thienyl silyl-l-hexenol ether(67d) with ceric ammonium nitrate. 145 A silyl enol ether(67d) (16.0 g, 62.5 mmole) in 30ml dry acetonitrile was added dropwise with vigorously stirring to a mixture of 36 g ceric ammonium nitrate (66.0 mmole), 11.3 g NaHCO3 (134 mmole) and 250 ml dry acetonitrile in an one litter round bottom flask under nitrogen. After the addition the reaction was continued at room temperature for four more hours and then quenched with water. The product was extracted with chloroform (4x30 ml) and the combined organic solvent was washed with water (3x20 ml) and dried with sodium sulfate. Removal of the solvent by a rotary evaporator gave a light-brown residue as the crude product. lH-NMR shows it is a mixture of diasteromers. Column chromatographic purification over silica gel with ethyl acetate/hexanes (10/90) as the eluent followed by crystallization from hexanes/CH2C12 (85/15) and recrystallization from hexanes gave one of the diastereomers as colorless needdle. mp. 161-162 °C (uncorrected). Further eluting with the same solvent gave the other diastereomers. Total yield of 1,4-diketones: 7.58 g (67% based on the starting ketone). 1H- NMR(CDCl3): 7.84(dd, J=4.3, 1.2Hz, 2H), 7.7l(dd, J=5.2, 1.2Hz, 2H), 7.16(dd, J=5.2, 4.3Hz, 2H), 3.72(d, 2H), 1.56-1.79(m, 2H), 1.29-1.44(m, 211), 1.04-1.19(m, 811), 0.68(t, 6H); 13C-NMR(CDC13): 196.6, 146.3, 134.7, 132.6, 128.4, 50.7, 32.2, 29.7, 22.7, 13.7; EI-MS m/z (relative intensity): 41(6.69), 43(2.59), 55(14.14), 69(3.44), 83(8.71), 85(2.05), 97(5.74), 111(100), 126(10.48), 139(37.37), 149(9.34), 154(5.8), 168(20.33), 181(12.12), 182(46.97), 195(26.52), 251(2.56), 306(1.25), 362(M+, 0.62). 146 b) Synthesis of 2,3-dibutyl-1,4-di(2-thienyl)-1,4- butanedione(60d) by the oxidation of thienyl silyl-l-hexenol ether(67d) with vanadium trichloride oxide A silyl enol ether(67d) 1.74 g (with 95.2% pure) (6.6 mmole) in 5 ml dry acetonitrile was added to a mixture of 1.15 g of VOCl3 (1.0 e.q) in 20 ml dry acetonitrile at room temperature under N2. After the addition, the dark-red mixture was quenched with 10ml ice-cold 5% NaHC03 aqueous solution. The organic layer was separated and the aqueous layer was extracted with ether (2x10 ml). The combined organic layers were washed with H2O (2x10 ml), saturated NaCl (10 ml) and dried with sodium sulfate; Removal of the solvent gave a light brown colored crude 1.4-diketone. lIrI-NMR shows it is a mixture of diastereomers. Column chromatographic purification over silica gel with ethyl acetate/hexanes (10/90) as the eluent followed by crystallization and recrystallization gave one of the diastereomers as colorless needles. m.p.=161-162 °C(uncorrected). All other physical properties are the same as those from method (a). Total yield of 1,4- diketones: 0.65 g (55% based on the starting ketone). Synthesis of 2,3-dihexyl-1,4-di(2-thienyl)-1,4-butanedione(60e): a) Synthesis of 2,3-dihexyl-1,4-di(2-thienyl)-1,4- butanedione(60e) by the oxidation of thienyl silyl-l-octenol ether(67c) with ceric ammonium nitrate. 147 A silyl enol ether(67c) (8.0 g, 28.4 mmole) in 30 ml dry acetonitrile was added dr0pwise with vigorously stirring to a mixture of 15.5 g ceric ammonium nitrate (28.4 mmole), 4.86 g NaHC03 (57.6 mmole) and 150 ml dry MeCN in a 500 ml round bottom flask under nitrogen. After the addition the reaction was continued at room temperature for four more hours and then quenched with water. The product was extracted with chloroform (4x30 ml) and the combined organic solvent was washed with water and dried over sodium sulfate. Removal of the solvent by a rotary evaporator gave a light- brown residue as the crude product. 1H-NMR shows it is a mixture of diastereomers. Column chromatographic purification over silica gel with ethyl acetate/hexanes (8/92) as the eluent followed by crystallization from hexanes/CH2C12 (90/10) and recrystallization from hexanes gave one of the diastereomers as colorless needles. m.p.=127-128 °C (uncorrected). Further eluting with the same solvent gave the other diastereomers. Total yield of 1,4-diketones: 3.70 g (63% based on the starting ketone). lH-NMR(CDC13): 7.82(2H, dd, J=4.3, 1.2Hz), 7.69(2H, dd, J=5.2, 1.2Hz), 7.16(2H, dd, J=5.2, 4.3Hz), 3.70(2H, m), 1.65-1.68(2H, m), 1.35-1.38(2H, m), 0.96-1.18(16H, m), 0.73(6H, t, J=7.9Hz); 13C-NMR(CDC13): 196.5, 146.3, 134.7, 132.6, 128.4, 50.7, 32.6, 31.4, 29.3, 27.6, 22.4, 13.9; EI-MS, mlz(relatively intensity): 418(M"’, 0.37), 334(1.45), 307(2.00), 223(16.71), 210(29.14), 196(12.15), 139(37.57), 126(19.20), 111(base), 55( 14.92). 148 b) Synthesis of 2,3-dihexyl-1,4-di(2-thienyl)-1,4- butanedione(60c) by the oxidation of thienyl silyl-l-octenol ether(67c) with vanadium trichloride oxide A silyl enol ether(67e) 2.35 g (with 96.0% pure) (8.3 mmole) in 5 ml dry acetonitrile was added to a mixture of 1.45 g of VOC13 (1.0 e.q) in 20 ml dry acetonitrile at room temperature under N2. After the addition, the dark-red mixture was quenched with 10 ml ice-cold 5% NaHCO3 aqueous solution. The organic layer was separated and the aqueous layer was extracted with ether (2x10 ml). The combined organic layers were washed with H2O (2x20 ml), saturated NaCl (20 ml) and dried with sodium sulfate. Removal of the solvent gave a light brown colored crude 1,4-diketones as a mixture of the diastereomers. Column chromatographic purification over silica gel with ethyl acetate/hexanes (8/92) as the eluent followed by crystallization from hexanes/CH2C12 (90/10) and recrystallization from hexanes gave one of the diastereomers as colorless needles. All the physical properties are the same as those from method (a). Total yield of 1,4-diketones: 0.93 g (54% based on the starting ketone). Synthesis of 3',4'-dimethyl-2,2',5',2”-terthiophene(57b) A mixture of 2,3-dimethyl-1,4-di(2-thienyl)-1,4-butanedione (2.0 g, 7.2 mmole), P2S5 (1.5 g, 6.7 mmole) (or Lawesson's reagent 1.8 g, 4.5 mmole), NaHCO3 (2.5 g, 29.8 mmole) and dry toluene (50 ml) was refluxed gently for two hours. The resulting dark mixture 149 was then cooled to room temperature; poured into water (100 ml) and extracted with CH2C12 (3x20 ml). The combined organic layers were washed with water (2x30 ml), saturated NaCl (30 ml) and dried with magnesium sulfate. Removal of the solvent in vacuo gave a dark-green residue as the crude product. Column chromatographic purification over silica gel with hexanes/ether (95/5) as the eluent and crystallization from hexanes gave the 3',4'-dimethyl-2,2',5',2”- terthiophene(57b) as a light yellow solid. Yield: 1.67 g (84%). m.p.=127-128 °C (uncorrected) (11:73“) 128 °C). 1H-NMR(CDC13): 7.32(dd, J=5.7, 1.3Hz, 2H), 7.17(dd, J=4.0, 1.3Hz, 2H), 7.09(dd, J=5.7, 4.0112, 211), 2.28(s, 6H); 13C-NMR(CDCI3): 135.9, 134.7, 132.8, 127.0, 125.5, 124.9, 13.7; EI-MS, mlz(relative intensity): 278(M++2, 15.3), 277(M*+1, 19.5), 276(M", base), 275(M+-1, 11.6), 261(13.l), 243(7.06), 227(7.1), 184(5.32), 139(4.11), 138(12.1), 127(14.2), 121(11.1), 109(5.65), 97(5.44), 69(10.5), 45(12.6); UV-Vis(maximum absorption): 335nm (CHCl3). Synthesis of 3',4'-diethyl-2,2',5',2"-terthiophene(57c) A mixture of 2,3-diethy1-1,4-di(2-thienyl)-l,4-butanedione (3.06 g, 10.0 mmole), P285 (2.2 g, 9.83 mmole) (or Lawesson's reagent 3.4 g, 8.5 mmole), NaHCO3 (3.5 g, 41.7 mmole) and dry toluene (60 ml) was refluxed gently for two hours. The dark reaction mixture was then cooled to room temperature; poured into water (100 ml) and extracted with CH2Cl2 (3x20 ml). The combined organic layers were washed with water (2x30 ml), saturated NaCl (30 ml) and dried 150 with magnesium sulfate. Removal of the solvent in vacuo gave a dark-green residue as the crude product. Column chromatographic purification over silica gel with hexanes as eluent followed by crystallization from hexanes gave the 3',4'-diethyl-2,2',5',2"- terthiophene(57c) as a light yellow solid. Yield: 2.67 g (88%). m.p.=97-98 °C (uncorrected). lH-NMR(CDC13): 7.32(dd, J=5.7, 1.3Hz, 2H), 7.16(dd, J=4.1, 1.3Hz, 2H), 7.10(dd, J=5.7, 4.1Hz, 2H), 2.61(q, J=8.0Hz, 411), 1.59(t, J=8.0Hz, 611). 13C-NMR(CDC13): 138.2, 135.7, 131.6, 127.2, 125.6, 124.5, 30.1, 13.8; EI-MS, mlz(relative intensity): 306(M++2, 14.7), 305(M*+1, 20.9), 304(M“, base), 277(12.8), 271(5.1), 241(5.71), 139(4.56), 138(11.8), 127(15.1). UV-Vis(maximum absorption): 335nm (CHCl3). Synthesis of 3',4'-dibutyl-2,2',5',2"-terthiophene(57d) A mixture of 2,3-dibutyl-1,4-di(2-thienyl)-1.4-butanedione (2.5 g, 6.9 mmole), P285 (1.4 g, 6.25 mmole) (or Lawesson's reagent 1.65 g, 4.1 mmole), NaHCOg (3.6 g, 42.9 mmole) and dry toluene (50 ml) was refluxed gently for two hours. The reaction mixture was then cooled to room temperature and poured into water (100 ml). The product was extracted with CH2C12 (3x30 ml) and the combined organic layers were washed with water (2x30 ml), saturated NaCl (30 ml) and dried with magnesium sulfate. Removal of the solvent in vacuo gave a dark-green residue as the crude product. Column chromatographic purification over silica gel with hexanes as 151 eluent followed by crystallization from hexanes gave the 3',4'- dibutyl-2,2',5',2"-terthi0phene(57d) as a light yellow solid. Yield: 2.01 g (81%). m.p.= 36-37 °c (uncorrected) (lit.5336-36.5 °C). 111— NMR(CDCl3): 7.32(dd, J=5.7, 1.4Hz, 2H), 7.16(dd, J=4.0, l.4Hz, 2H), 7.07(dd, J=5.7, 4.0Hz, 2H), 2.72(t, J=8.8Hz, 4H), 1.57(m, 4H), l.46(m, 4H), 0.97(t, J=8.8Hz, 6H); l3C-NMR(CDC13): 140.0, 135.7, 129.7, 127.4, 125.8, 125.3, 32.9, 27.8, 23.0, 13.9; EI-MS, mlz(relative intensity): 362(M++2, 18.1), 361(M*+1, 24.7), 360(M“, base), 319(7.09), 318(12.2), 317(39.6), 303(13.7), 277(8.88), 276(13.9), 275(56.1), 273(8.65), 260(9.76), 242(11.4), 24l(10.9), 227(10.8), 138(5.18), 127(19.2); UV-Vis(maximum absorption): 335nm (CHCl3). Synthesis of 3',4'-dihexyl-2,2',5',2"-terthiophene(57e) A mixture of 2,3-dihexyl-1,4-di(2-thienyl)-1,4-butanedione (2.18 g, 5.2 mmole), P285 (1.2 g, 5.36 mmole) (or Lawesson's reagent 1.5 g, 3.75 mmole), NaHCO3 (3.5 g, 41.7 mmole) and dry toluene (50 ml) was refluxed gently for two hours. The dark reaction mixture was then cooled to room temperature and poured into water (100 ml). The product was extracted with CH2C12 (3x30 ml) and the combined organic layers were washed with water (2x30 ml), saturated NaCl (30 ml) and dried with magnesium sulfate. Removal of the solvent in vacuo gave a dark-green residue as the crude product. Column chromatographic purification over silica gel with hexanes as the eluent followed by crystallization from hexanes gave the 3',4'-dihexyl-2,2',5',2"-terthiophene(57e) as a light yellow oil. 152 Yield: 1.92 g (89%). lH-NMR(CDC13): 7.33(dd, J=5.8, l.4Hz, 2H), 7.17 (dd, J=4.0, 1.4Hz, 2H), 7.09(dd, J=5.8, 4.0Hz, 2H), 2.73(t, J=8.1Hz, 4H), 1.61(m, 411), 1.45(m, 411), 1.36(m, 8H), 0.94(t, J=7.8Hz, 6H). 13c- NMR(CDC13): 140.1, 135.7, 129.6, 127.3, 125.8, 125.2, 31.5, 30.7, 29.6, 28.1, 22.6, 14.1; EI-MS, mlz(relative intensity): 416(M“, base), 401(12.7), 400(56.1), 346(8.63), 345(33.7), 331(8.92), 289(5.90), 277(14.3), 276(18.7), 275(97.3), 261(9.12), 242(8.04), 227(6.57), 127(5.02), 43(10.3); UV-Vis(maximum absorption): 335nm (CHCl3). Synthesis of 3,4-dimethyl-2,5-di(2-thienyl)pyrrole(6lb) A mixture of 2,3-dimethyl-l,4-di(2-thienyl)-1,4- butanedione(60b) (1.57 g, 5.6 mmole), anhydrous NH40Ac (1.54 g, 20.0 mmole), acetic anhydride (2.0 ml) in 50ml acetic acid was refluxed gently for 48 hours. Then the dark-red reaction mixture was cooled and the acetic acid/acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x30 ml) and the combined ether layers were washed with 5% sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml), and dried with sodium sulfate. The solvent was removed by a rotary evaporator. Column chromatographic purification over silica gel with hexanes/ether (95/5) as the eluent followed by crystallization from hexanes/CH2C12 (85/15) gave the 3,4-dimethyl- 2,5-di(2-thienyl)pyrrole(6lb) as a pale yellow solid. Yield: 1.01 g (75%). m.p.=l32-133 °C (uncorrected). 1H-NMR(CDC13): 7.98 (s, br., 1H), 7.23 (m, 2H), 7.08-7.01 (m, 4H), 2.29 (s, 6H). 13C-NMR(CDC13): 153 135.4, 127.3, 123.4, 123.0, 122.7, 122.1, 14.4; EI-MS, m/z (relative intensity): 261 (MN-2, 10.1), 260 (M*+1, 17.1), 259 (M+, base), 258 (M+-1, 17.2), 244 (10.2), 147(5.76), 110 (7.15).-UV-Vis (maxmum absorption): 345nm (CHCl3). Synthesis of 3,4-diethyl-2,5-di(2-thienyl)pyrrole(61c) A mixture of 2,3-diethyl-1,4-di(2-thienyl)-1,4- butanedione(60c) (1.72 g, 5.6 mmole), anhydrous NH40Ac (1.50 g, 19.5 mmole), acetic anhydride (2.0 ml) in 50 ml acetic acid was kept at gentle reflux for 48 hours. Then the dark-red reaction mixture was cooled and the acetic acid/acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x30 ml) and the combined ether layers were washed with 5% sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator. Column chromatographic purifucation over silica gel with hexanes/ether (97/3) as eluent followed by crystallization from hexanes/CH2C12 (90/10) gave the 3,4-diethyl- 2,5-bis(2-thienyl)pyrrole(6lc) as a pale yellow solid. Yield: 1.20 g (74%). m.p.=103-104 °c (uncorrected). ‘H-NMR(CDC13): 8.00(s, br., 1H), 7.22(d, J=5.3Hz, 2H), 7.10-7.02(m, 4H), 2.61(q, J=8.2Hz, 4H), 14.8(t, J=8.1Hz, 6H); 13C-NMR(CDC13): 135.6, 127.3, 123.2, 123.0, 122.7, 122.3, 31.0, 13.8; EI-MS, mlz(relative intensity): 289(M*+2, 10.6), 288(M++1, 18,0), 287(M”, base), 27204.2), 258(9.3), 154 244(6.97), 147(6.81), 110(7.09); UV-Vis(maximum absorption): 345nm (CHCl3). Synthesis of 3,4-dibutyl-2,5-di(2-thienyl)pyrrole(61d) A mixture of 2,3-dibutyl-1,4-di(2-thienyl)-1,4- butanedione(60d) (2.1 g, 5.8 mmole), anhydrous NH40Ac (1.60 g, 20.8 mmole), acetic anhydride (2.0 ml) in 50 ml acetic acid was refluxed gently for 48 hours. Then, the dark-red reaction mixture was cooled and the acetic acid/acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x30 ml) and the combined ether layers were washed with 5% sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator. Column chromatography purification over silica gel with hexanes as the eluent gave the 3,4-dibutyl-2,5-di(2- thienyl)pyrrole(61d) as a pale yellow solid. Yield: 1.60 g (80%). m.p.=47-48 °C (uncorrected). lH-NMR(CDC13): 7.97(s, br., 111), 7.21(d, J=5.4Hz, 2H), 7.08-7.02(m, 4H), 2.63(t, J=8.6Hz, 4H), 1.56(m, 4H), 1.45(m, 4H), 0.96(t, J=7.8Hz, 6H); l3C-NMR(CDCI3): 135.5, 127.4, 123.3, 123.1, 122.8, 122.2, 33.5, 24.7, 23.0, 13.9; EI-MS, e/z(relative intensity): 345(M”+2, 10.4), 344(M*+1, 20.8), 343(M*, base), 301(11.6), 300(50.3), 260(7.6), 259(15.5), 258(76.4), 256(13.2), 244(6.13), 17(5.05), 147(6.33), 129(13.0), 110(6.02), 43(5.05), 41(9.12); ,UV-Vis(maximum absorption): 345nm (CHCl3). 155 Synthesis of 3,4-dihexyl-2,5-di(2-thienyl)pyrrole(6 1e) A mixture of 2,3-dihexyl-1,4-di(2-thienyl)-1,4-butanedione (606) (1.65 g, 3.9 mmole), anhydrous NH40Ac (1.20 g, 15.6 mmole), acetic anhydride (2.0 ml) in 50 ml acetic acid was refluxed gently for 48 hours. Then the dark-red reaction mixture was cooled and the acetic acid/acetic anhydride were removed by vacuum distillation. The residue was extracted with ether (4x30 ml) and the combined ether layers were washed with 5% sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator. Column chromatographic purification over silica gel with hexanes as the eluent gave the 3,4-dihexyl-2,5-di(2-thienyl)pyrrole(61e) as a pale yellow solid. Yield: 1.26 g (81%). m.p.=31-32 °C(uncorrected). lH- NMR(CDC13): 7.98(s, br., 1H), 7.22(d, J=5.4, 2H), 7.09-7.02(m, 4H), 2.67(t, J=8.2Hz, 4H), 1.59(m, 4H), 1.42(m, 4H), 1.34(m, 8H), 0.95(t, J=7.7Hz, 6H); 13C-NMR(CDC13): 135.7, 129.6, 124.0, 123.1, 122.8, 122.0, 31.8, 29.7, 29.0, 27.3, 22.1, 13.8; EI-MS, mlz(relative intensity): 401(M++2, 10.9), 400(M++1, 26.8), 399(M“, base), 384(10.9), 329(28.7), 314(7.45), 258(67.8), 244(5.18), 147(6.51), 110(5.91); UV-Vis(maximum absorption): 345nm (CHCl3). Synthesis of 3,4-dimethyl-2,5-di(2-thienyl)furan(62b) 156 A solution of 2,3-dimethyl-1,4-di(2-thienyl)-l,4- butanedione(60b) (2.51 g, 9.03 mmole) in 30 ml acetic anhydride was kept in an acetone-dry-ice bath(-15 to -20°C) with magnetic stirring. Gaseous HCl was bubbled through this cold solution for 15 min and then the acetone-bath was removed and the reaction mixture was allowed to warm up to room temperature. The mixture was stirred at 85°C for 8 hours. Then the dark reaction mixture was cooled and acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x30 ml) and the combined ether layers were washed with 5% sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator. Column chromatographic purification over silica gel with hexanes/ether (95/5) as the eluent gave the 3,4-dimethyl-2,5-di(2- thienyl)furan(62b) as a pale yellow solid. Yield: 1.52 g (65%). m.p.=108-109 °C(uncorrected). lH-NMR(CDC13): 7.31(d, J=4.1Hz, 211), 7.26(d, J=5.5Hz, 211), 7.08(dd, J=5.5Hz, 4.1Hz, 2H), 2.23(s, 6H); 13c- NMR(CDC13): 142.1, 133.6, 128.0, 123.8, 123.5, 122.4, 13.7; EI-MS, mlz(relative intensity): 262(M++2, 3.17), 261(M++l, 8.26), 260(M", 67.4), 259(17.5), 245(4.1), 231(5.60), 176(3.91), 162(4.76), 134(5.14), 111(base), 83(10.9); UV-Vis (maximum absorption) 337nm (CHC13). Synthesis of 3,4-diethyl-2,5-di(2-thienyl)furan(62c) 157 A solution of 2,3-diethyl-l,4-di(2-thienyl)-1,4-butanedione (60c) (2.08 g, 6.8 mmole) in 30 ml acetic anhydride was kept in an acetone-dry-ice bath(-15 to -20 °C) with magnetic stirring. Gaseous HCI was bubbled through this cold solution for 15 min. Then the acetone-bath was removed and the reaction was allowed to warm up to room temperature. Then the reaction mixture was stirred at 85°C for 8 hours. The dark mixture was cooled and the acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x30 ml) and the combined ether layers were washed with 5% aqueous sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator. Column chromatographic purification over silica gel with hexanes/ether (97/3) as eluent gave the 3,4-diethyl-2,5-di(2-thienyl)furan(62c) as a pale yellow solid. Yield: 1.25 g (64%). m.p.=69-70 °C(uncorrected). lH-NMR(CDC13): 7.31(d, J=4.1Hz, 2H), 7.25(d, J=5.6Hz, 2H), 7.07(dd, J=5.6, 4.1Hz, 2H), 2.61(q, J=8.1Hz, 411), 1.04(t, J=8.1Hz, 6H); 13C-NMR(CDC13): 142.8, 133.7, 128.4, 123.9, 123.5, 122.4, 29.7, 13.6; EI-MS, mlz(relative intensity): 290(M*+2, 4.96), 289(M*+1, 11.8), 288(M*, 72.1), 27300.9), 259(5.7), 245(20.7), 162(4.08), 134(5.16), 111(base), 83(14.7); UV-Vis(maximum absorption): 337nm (CHC13). Synthesis of 3,4-dibutyl-2,5-di(2-thienyl)furan(62d) A solution of 2,3-dibutyl-1,4-di(2-thienyl)-1,4-butanedione (60d) ( 2.41 g, 6.6 mmole) in 30 ml acetic anhydride was kept in 158 an acetone-dry-ice bath (-15 to -20 °C) with magnetic stirring. Gas HCI was bubbled through this cold solution for 15 min. Then the cold- bath was removed and the solution was allowed to warm up to room temperature. The reaction mixture was stirred at 85 °C for 8 hours. The dark reaction mixture was cooled and the acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x30 ml) and the combined ether extracts were washed with 5% sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator. Column chromatographic purification over silica gel with hexanes as the eluent gave the 3,4- dibuty1-2,5-di(2-thienyl)furan(62d) as a pale yellow oil. Yield: 1.58 g (69%). 1H-NMR(CDC13): 7.30(d, J=4.0Hz, 2H), 7.26(d, J=5.6Hz, 2H), 7.09(dd, J=5.6, 4.0Hz, 2H), 2.64(t, J=8.2Hz, 4H), 1.61(m, 4H), 1.50(m, 411), mm, J=7.8Hz, 6H); l3C-NMR(CDC13): 143.2, 133.5, 127.4, 123.7, 123.5, 122.6, 32.1, 23.9, 23.0, 13.9; EI-MS, mlz(relative intensity): 346(M*+2, 8.6), 345(M*+1, 17.0), 344(M“, 73.3), 301(10.9), 273(6.0), 259(14.6), 231(8.7), 191(4.6), 184(5.6), 147(8.9), 129(8.6), 115(5.1), 113(8.4), 112(9.9), 111(base), 97(21.5), 85(15.5), 83(15.4), 77(5.2), 57(11.5), 43(12.6), 41(22.2), 39(20.6); UV-Vis(maximum absorption): 337nm (CHCl3). Synthesis of 3,4-dihexy1-2,5-di(2-thienyl)furan(62e) A solution of 2,3-dihexyl-l,4-di(2-thieny1)-1,4- butanedione(60c) (1.94 g, 4.6 mmole) in 30 ml acetic anhydride was 159 kept in an acetone-dry-ice bath (-15 to -20 °C) with magnetic stirring. Gaseous HCl was bubbled through this cold solution for 15 min. Then the acetone-bath was removed and the reaction was allowed to warm up to room temperature. The reaction mixture was stirred at 85°C for 8 hours. Then, the mixture was cooled and the acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x30 ml) and the combined ether layers were washed with 5% sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator. Column chromatographic purification over silica gel with hexanes as the eluent gave the 3,4-dihexyl-2,5-di(2-thienyl)furan(62e) as a pale yellow oil.Yield: 1.13 g (61%). 1H-NMR(CDC13): 7.30(d, J=4.0Hz, 2H), 7.25(d, J=5.6Hz, 2H), 7.09(dd, J=5.6, 4.0Hz, 2H), 2.63(t, J=8.1Hz, 4H), 1.61(m, 411), 1.43(m, 411), 1.30(m, 8H), 0.94(t, J=7.8Hz, 611); 13C- NMR(CDC13): 143.0, 133.8, 128.6, 124.0, 123.7, 122.5, 31.2, 29.8, 29.3, 27.5, 22.4, 13.5; EI-MS, mlz(relative intensity): 402(M++2, 7.9), 401(M"’+1, 20.9), 400(M+, 78.1), 385(8.24), 329(9.7), 315(2.87), 245(18.6), 111(base), 83(12.8). UV-Vis(maximum absorption): 337nm (CHClg). Synthesis of 2-(1-trimethylsilyl pyrryl) trimethylsilyl ethenol ether(7 7 ): To a mixture of Nal (3.75 g, 25 mmole), ClSiMe3 (2.70 g, 24.9 mmole) and Et3N (2.52 g, 25 mmole) in acetonitrile (30 ml) was 160 added dropwise the 2-acetyl pyrrole (1.09 g, 10.0 mmoles) in 5 m1 dry acetonitrile. The resulted opaque mixture was stirred at room temperature under N2 for two hours and then the reaction was quenched with saturated NaHCO3 solution. The mixture was extracted with petroleum ether (bp=35 - 60 °C) (3x30 ml) and the combined organic layers were washed with water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator to give an orange oil residue as the crude product. Vacuum distillation gave the product as a colorless oil. Yield: 2.30 g (91%). 1H-NMR(CDC13): 6.75(dd, J=3.0, 1.7Hz, 1H), 6.32(dd, =3.5, 1.7Hz, 1H), 6.13(dd, J=3.5, 3.0Hz, 1H), 4.55(d, J=1.1Hz, 1H), 4.30(d, J=1.1Hz, 1H), 0.29(s, 9H); Synthesis of 1,4-di(2-pyrryl)-1 ,4-butanedione(7 8): A solution of 2-(1-trimethylsilyl pyrryl) trimethylsilyl ethenol ether(77) (2.30 g, 9.09 mmole) in 2m1 dried acetonitrile was added dropwise to a mixture of VOC13 (10.0 mmoles) and pyridine (10.0 mmoles) in dry acetonitrile (20 ml) at 0 °C under N2. After the addition the reaction mixture was stirred at 0 °C for 15 min. The reaction was quenched with saturated aqueous sodium bicarbonate solution. Then, the mixture was extracted with ether (3x20 ml) and the combined ether layers were washed with 5% NaHC03 (2x20 ml), H20 (30 ml), saturated NaCl (20 ml) and dried with Na2SO4. The solvent was removed by a rotary evaporator to give a light brown colored residue as the crude product. Column chromatographic 161 purification over silica gel with ether/ethyl acetatezlhexanes (5/3/92) as the eluent, followed by crystallization from ethanol gave the expected l,4-di(2-pyrryl)-1,4-butanedione(78) as colorless needles. Yield: 8%. mp=154 -156 °C(uncorrected). 1H-NMR(CDC13): 10.2(2H, s, broad), 7.14(2H, m), 6.98(2H, m), 6.29(2H, m), 3.41(4H, s); EI-MS, mlz(relatively intensity): 216(M”, 21.4), 122(52.3), 94(base), 66(31.4). Synthesis of 2,5-di(5-(2,2'-bithienyl))-1,3,4-thiadiazole(79): A mixture of 5-(2,2'-bithienyl) carboxaldehyde (2.50 g, 12.9 mmole), hydrazine monohydrate (320 mg, 6.4 mmole), elemental sulfur (500 mg, 15.6 mmole), and tributylamine (150 mg, 0.8 mmole) in 20 ml of propylene glycol was heated at 120 °C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was collected by suction filtration. The solid was washed with ice-cold methanol (3x20 ml), carbon disulfide (3x15 ml) and dried in vacuum to give a light tan solid as crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (40/60) as eluent followed by crystallization from ethanol/ethyl acetate (50/50) gave the 2,5-di(5-(2,2'-bithienyl))- 1,3,4-thiadiazole(79) as orange needles. Yield: 390 mg (28%). m.p.=259-261 °C(uncorrected). lH-NMR(DMSO-d5): 7.63(d, J=4.4Hz, 211), 7.35(m, 4H), 7.23(d, J=4.4Hz, 211), 7.08(m, 211); l3C-NMR(DMSO- d5): 164.1, 146.6, 141.5, 137.2, 135.7, 128.3, 127.1, 126.1, 124.2; E1- M8, mlz(relative intensity): 414(M“, 10.7), 223(base), 191(4.6); High 162 resolution mass spectra, calculated. for C13H10N285: 414.580, found: 414.495; UV-Vis(maximum absorption): 379nm (CHCl3). Synthesis of 2,5-di(5 -(2,2',5',2"-terthienyl))-1,3,4-thiadiazole(8 l): A mixture of 5-(2,2',5',2"-terthienyl) carboxaldehyde (500 mg, 1.8 mmole), hydrazine monohydrate (45 mg, 0.9 mmole), elemental sulfur (150 mg, 4.69 mmole), and tributylamine (50 mg, 0.27 mmole) in 20 ml of propylene glycol was heated at 120 °C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was collected by suction filtration. The solid was washed with ice-cold methanol (3x20 m1), carbon disulfide (3x15 m1) and dried in vacuum to give a tan solid as crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (SO/50) as eluent followed by crystallization from ethanol/ethyl acetate (50/50) gave the 2,5-di(5-(2,2',5',2"- terthienyl))-1,3,4-thiadiazole(81) as orange needles. Yield: 57 mg (11%). m.p.=309-310 °c (uncorrected). 1H-NMR(DMSO-d5): 7.61(d, =4.1, 2H), 7.22(m, 8H), 7.11(d, J=4.1Hz, 2H), 7.05(dd, J=4.4, 3.9Hz, 2H); 13C-NMR(DM80-d5): 162.4, 145.1, 142.3, 140.8, 139.8, 136.5, 135.8, 132.5, 129.4, 128.0, 126.3, 125.7, 125.2. EI-MS, mlz(relative intensity): 578(M“, base), 305(49.6), 289(6.74), 273(8.76). High resolution mass spectra, calculated for C25H14N2S7: 578.812, found 578.719. UV-Vis(maximum absorption): 432nm (CHC13). 163 Synthesis of 2,5-di(5-(2,2'-bithienyl))thiazolo[5,4-d]thiazole(80): A mixture of 5-(2,2'-bithienyl) carboxaldehyde (1.50 g, 7.7 mmole) and dithiooximide (0.46 g, 3.8 mmole) in 20 ml DMF was heated at gentle reflux under N2 for 30 min. The dark red reaction mixture was cooled and the precipitate was collected by suction filtration. The solid was washed with water (2x20 ml), ice-cold methanol (3x10 ml) and then dried in vacuum. Column chromatographic purification over silica gel with ethyl acetate/hexanes (50/50) as eluent followed by crystallization from ethyl acetate/ethanol (50/50) gave the 2,5-di(5-(2,2'- bithienyl))thiazolo[5,4-d]thiazole(80) as orange needles. Yield:370 mg (22%). m.p.=276-277 °c (uncorrected). lH-NMR(DMSO-d6): 7.54(d, J=4.2Hz, 2H), 7.31(m, 4H), 7.19(d, J=4.2Hz, 2H), 7.02(m, 2H); EI-MS, mlz(relative intensity): 470(M“, base), 279(2.71), 19l(10.8), 88(78.6), 83(6.90). High resolution mass spectra, calculated for C2oH10N285: 470.660, found: 470.459. UV-Vis(maximum absorption): 407nm (CHClg). Synthesis of 2,5-di(5-(2,2',5',2"-terthienyl))thiazolo[5,4- d]thiazole(82): A mixture of 5-(2,2',5',2"-terthienyl) carboxaldehyde (400 mg, 1.45 mmole) and dithiooximide (87 mg, 0.72 mmole) in 20 ml DMF was heated at gentle reflux under N2 for 30 minutes. The dark red reaction mixture was cooled and the precipitate was collected by 164 suction filtration. The solid was washed with water (2x20 ml), ice- cold methanol (3x10 ml) and then dried in vacuo to give a tan solid as the crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (60/40) as eluent followed by crystallization from ethyl acetate/ethanol (50/50) gave the 2,5-di(5- (2,2',5',2"-terthienyl))thiazolo[5,4-d]thiazole(82) as orange needles. Yield: 65 mg (15%). m.p.=326-328 °C (uncorrected). lH-NMR(DMSO- d5): 7.60(d, J=4.0, 2H), 7.23(m, 8H), 7.10(d, J=4.0Hz, 2H), 7.04(dd, J=4.5, 3.9Hz, 211). 13C-NMR(DMSO-d5): 158.6, 148.0, 146.5, 145.4, 142.6, 141.0, 140.1, 136.9, 135.7, 132.8, 130.0, 128.5, 127.1, 126.4, 126.0. EI-MS, mlz(relative intensity): 634(M”, base), 361(5.16), 273(11.29), 88(57.6); High resolution mass spectra, calculated for C23H14N283: 634,892, found 634.816. UV-Vis(maximum absorption): 478nm (CHCl3). Synthesis of 5-formyl-3',4'-dibutyl-2,2',5',2"-terthiophene(89): a), Synthesis of 5-formyl-3',4'-dibutyl-2,2',5',2"-terthiophene(89) by the lithiation of the 2,2',5',2"-terthiophene followed by the reaction of the lithiated compound with DMF: BuLi (0.7 ml of 1.6M in hexanes solution,1.1 eq.) was added to a cooled (-50 °C) mixture of 3',4'-dibutyl-2,2',5',2"-terthiophene (360 mg, 1.0 mmole), tetramethylethenediamine (TMEDA, 100 mg) and 15 ml hexanes by a syringe under N2. After the addition, the reaction mixture was stirred at -50 °C for 30 minutes and then stirred at 165 room temperature for another 30 minutes. The reaction mixture was then recooled to -78 °C and 1.2 eq. of dimethyformamide(DMF) in 5 ml ether was added slowly by a syringe. After the addition the reaction was slowly raised to room temperature and the mixture was stirred for one more hour. Then, the mixture was poured into 50 ml 2% ice cold aqueous HCl solution with vigorously stirring. Then the mixture was extracted with ether (3x15 ml). The combined organic extracts were washed with water (2x20 ml), saturated NaHCO3 (2x20 ml), saturated NaCl (20 ml) and dried with MgSO4. Removal of the solvent gave a dark-oil which solidify when cooled. Column chromatographic purification over silica gel with hexanes/ether] CH2C12 (85/10/5) as eluent followed by crystallization from hexanes gave the 5-formyl-3',4'-dibutyl-2,2'5',2"-terthiophene(89) as a light green yellow solid product. Yield:279 mg(72%). mp=41-42 °C (uncorrected). lH-NMR (CDC13): 9.86(1H, s), 7.67(1H, d, J=4.5Hz), 7.33(1H, dd, J=5.7 and 1.3Hz), 7.21(1H, d, J=4.5Hz), 7.16(1H, dd, J=4.0 and 1.3Hz), 7.07(1H, dd, J=5.7 and 4.0Hz), 2.74(4H, m), 1.35-1.60(8H, m), 0.93(6H, m); l3C-NMR(CDC13): 182.6, 146.5, 142.5, 142.1, 140.7, 136.8, 135.5, 132.3, 128.8, 127.5, 126.4, 126.1, 32.8, 32.6, 28.1, 27.7, 23.0, 22.9, 13.8(2). EI-MS mlz(relative intensity): 388(M”, base), 345(17.5), 331(9.9), 317(10.9), 303(28.6), 275(28.4), 274(14.7), 273(7.6), 240(11.0), 227(11.1), 126(18.8), 111(21.4). UV-Vis(CHC13): 393nm. b), Synthesis of 5-formyl-3',4'-dibutyl-2,2'5',2"-terthiophene(89) by a Vilsmier reaction: 166 To a stirred solution of 3',4'-dibutyl-2,2',5',2"-terthiophene (1.48 g, 4.1 mmole) in dry N,N-dimethylformamide (314 mg, 4.3 mmole, 1.05 eq.) at 60 °C, POC13 (0.7 g, 4.5 mmole) was added dropwise by a syringe over 10 minutes under nitrogen. After the addition, the reaction mixture was stirred at this temperature for 2 hours and then at 80 °C for 2 more hours. Then an excess of aqueous sodium acetate solution (20 ml, 10%) was added and the mixture was stirred at room temperature for 5 hours and heated on a steam-bath for 30 minutes. The mixture was cooled to room temperature and extracted with ether (3x15 ml). The combined organic layers were washed with water (2x20 ml), saturated NaHC03 (2x20 ml), brine (30 ml) and dried with MgSO4. Removal of the solvent gave a dark-oil which solidified when cooled. Column chromatographic purification over silica gel with hexanes/ether/CH2C12 (85/10/5) as eluent followed by crystallization from hexanes gave the expectd 5-formyl- 3',4'-dibutyl-2,2',5',2"-terthiophene(89) as a light green yellow solid. Yield:1.21 g (76%). All the spectroscopic characterizations are the same as those from Method (a). Synthesis of 1,4-di(5-(3',4'-dibutyl-2,2',5',2"-terthienyl))-1,4- butanedione(88): a), Synthesis of 1,4-di(5-(3',4'-dibuty1-2,2',5',2"-terthienyl))-1,4- butanedione(88) by a Friedel-Crafts acylation reaction: 167 A solution of 3',4'-dibutyl-2,2',5',2"-terthiophene (3.60 g, 10 mmole), succinyl chloride (0.77 g, 5.0 mmole) in 10 ml of CH2C12 was added dropwise over 60 minutes to a vigorously stirred mixture of SnCl4 (2.60 g, 10 mmoles) in 20 ml CH2C12 at 0 °C under N2. After the addition the reaction mixture was stirred continuously at the same temperature for one more hour. The dark-red reaction mixture was quenched with ice cold 3% HCI aqueous solution. The organic layer was separated and the aqueous layer was extrated with CH2C12 (2x20 ml). The combined organic layers were washed with water (2x20 m1), saturated NaHC03 (20 ml), brine (20 ml) and then dried with sodium sulfate. The solvent was removed by a rotary evaporator to give a dark color solid crude product. Column chromatographic purification over silica gel with ethyl acetate/CH2Cl2/hexanes (20/15/65) as eluent followed by crystallization from CH2C12/hexanes (20/80) gave the product as yellow needles. Yield: 880 mg (22%). m.p.=175-176 °C (uncorrected). lH-NMR (c0013): 7.73(2H, d, J=4.4Hz); 7.32(2H, dd, J=4.4 and 1.3Hz); 7.17(2H, d, J=4.4Hz); 7.14(2H, dd, J=5.3 and 1.3Hz); 7.05(2H, dd, J=5.3 and 4.4Hz); 3.37(4H, s); 2.75(4H, t); 2.69(4H, t); 1.53(8H, m); 1.43(8H, m); 0.95(6H, t); 0.93(6H,t). l3C-NMR(CDC13): 190.6, 144.9, 142.1, 141.9, 140.5, 135.7, 132.5, 131.7, 129.0, 127.4, 126.3, 126.1, 125.8, 32.9, 32.8, 32.6, 28.0, 27.7, 23.0, 22.9, 13.9, 13.8; EI-MS, mlz(relative intensity): 802(M”, 55.7), 415(base), 402(13.8), 401(M2+,12.1), 387(43.75), 317(10.3), 274(14.8), 147(70.74), 75(10.9), 55(14.2). UV-Vis(CHCl3): 390nm. 168 b). Synthesis of 1,4-di(5-(3',4'-dibutyl-2,2',5',2"-terthienyl))-1,4- butanedione(88) by a Stetter's reaction: A mixture of 5-formyl-3',4'-dibutyl-2,2',5',2"-terthiophene(89) (388 mg, 1.0 mmole), 3,4-dimethyl-5-(2-hydroxyethyl)-thiazolium iodide 28.5 mg, 0.1 mmole)(cat.), NaOAc (16.4 mg, 0.2 mmoles) in 5 ml absolute ethanol was refluxed gently under N2 for 6 hours. The reaction mixture was then cooled to room temperature and poured into 50 ml of water. The mixture was extracted with CHCl3 (3x15 ml) and the combined organic layers were washed with water (2x20 ml) and saturated NaCl (30 ml). The solvent was removed by a rotary evaporator to give an orange solid as the crude product. Column chromatographic purification over silica gel with ethyl acetate/CH2C12/Hexanes(20:15:65) as eluent gave the 1,4-di(5-(3',4'- dibutyl-2,2'5',2"-terthienyl))-1,4-butanedione(88) as light yellow needles. Yield:268 mg (67%). m.p.=175-176 °C (uncorrected). lH-NMR (CDC13): 7.73(2H, d, J=4.4Hz); 7.32(2H, dd, J=4.4 and 1.3Hz); 7.17(2H, d, J=4.4Hz); 7.14(2H, dd, J=5.3 and 1.3Hz); 7.05(2H, dd, J=5.3 and 4.4Hz); 3.37(4H, s); 2.75(4H, t); 2.69(4H, t); 1.53(8H, m); 1.43(8H, m); 0.95(6H, t): 0.93(6H,t). 13C-NMR(CDC13): 190.6, 144.9, 142.1, 141.9, 140.5, 135.7, 132.5, 131.7, 129.0, 127.4, 126.3, 126.1, 125.8, 32.9, 32.8, 32.6, 28.0, 27.7, 23.0, 22.9, 13.9, 13.8; EI-MS, mlz(relative intensity): 802(M+, 55.7), 415(base), 402(13.8), 401(M2+,12.1), 387(43.75), 317(10.3), 274(14.8), 147(70.74), 75(10.9), 55(14.2). UV-Vis(maximum absorption): 390nm (CHClg). 169 Synthesis of 3',3'"",4',4""'-tetrabutyl- 2,29,51,201’511,2101,5111’211 "’5" "’2" "1’5""1’2" ”n'hcptathiophcne(83): A mixture of 1,4-di(5-(3’,4'-dibutyl-2,2',5',2"-terthiophene))- 1,4-butanedione (80 mg, 0.1 mmoles), Lawesson's reagent (50 mg, 0.124 mmoles) and 5 ml toluene was refluxed gently for two hours under N2. The dark reaction mixture was cooled to room temperature and poured into 20 ml of water. The mixture was then extracted with CH2C12 (3x10 ml) and the combined organic layers were washed with water (2x15 ml), dried with MgSO4. Removal of the solvent by a rotary evaporator gave a tan color solid as the crude product. Column chromatographic purification over silica gel with hexanes/ether (95/5) as the eluent followed by crystallization from hexanes gave the 3',3""',4',4""'-tetrabutyl-2,2',5',2",5",2"',5"',2"",5"",2""',5""',2"""- heptathiophene(83) as orange needles. Yield 65 mg (82%). m.p.=129- 130 °C (uncorrected). 1H-NMR(CDC13): 7.30(2H, dd, J=5.4 and 1.2Hz), 7.02-7.14(10H, m), 2.64-2.77(8H, m), l.48-1.60(8H, m), l.38-1.48(8H, m), 0.88-0.95(12H, m); 13C-NMR(CDC13): 140.24(2), 136.6, 136.1, 136.0, 135.4, 130.1 129.6, 127.4, 126.4, 125.9, 125.4, 124.3, 124.0, 32.9, 32.8, 27.9, 27.8, 23.04, 23.00, 13.87(2); EI-MS, mlz(relative intensity): 800(M+, base), 400(M2+, 25.15), 315(24.24), 308(11.06), 97(13.48), 84(22.58), 69(17.42), 55(22.88). UV-Vis(CHCl3): 429nm. 170 Synthesis of 2,5 -di(5-(3',4'-dibuty1-2,2',5',2"-terthieny1))furan(84): A solution of l,4-di(5-(3',4'-dibutyl-2,2',5',2"-terthienyl))-1,4- butanedione (60 mg, 0.075 mmole) in 10 ml acetic anhydride was kept in an acetone-dry-ice bath(-15 to -20 °C) with magnetic stirring. Gaseous HCl was bubbled through this cold solution for 15 minutes. Then the cold-bath was removed and the solution was allowed to warm up to room temperature. Then, the reaction mixture was stirred at 95 °C for 10 hours. The dark reaction mixture was cooled and the acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x30 m1) and the combined ether layers were washed with 5% sodium bicarbonate solution (3x20 ml), water (2x20 ml), saturated NaCl (2x15 ml) and dried with sodium sulfate. Removal of the solvent by a rotary evaporator gave a dark colored residue as the crude product. Column chromatographic purification over silica gel with hexanes/ether (97/3) as the eluent gave the 2,5-di(5-(3‘,4'-dibutyl-2,2',5',2"-terthienyl))furan(84) as orange solid. Yield: 58 mg (19%). m.p.=112-114 °C (uncorrected). lH- NMR(CDC13): 7.31(dd, J=5.2, 1.2Hz, 2H), 7.15-7.02(m, 10H), 2.59- 2.70(m, 8H), 1.46-1.6l(m, 8H), 1.37-1.45(m, 8H), 0.90-0.95(m, 12H); 13C-NMR(CDC13): 140.1, 139.8, 136.4, 136.0, 135.7, 135.2, 130.0, 129.2, 127.0, 126.1, 125.4, 125.1, 124.0, 123.6, 32.7, 32.6, 27.7, 27.6, 23.0(2), 13.5(2); EI-MS, mlz(relative intensity): 784(M+, base), 741(30.4), 713(5.1), 699(14.1), 392(2.10), 344(18.4), 302(4.79). High resolution mass spectra, calculated for C44H43085: 785.184, found: 785.149. UV-Vis(maximum absorption): 431nm (CHCl3). 171 Synthesis of 2,5-di(5-(3',4'-dibutyl-2,2',5',2"-terthienyl))pyrrole(85): A mixture of 1,4-di(5-(3',4'-dibutyl-2,2',5',2"-terthienyl))-1,4- butanedione (56 mg, 0.07 mmole), anhydrous NH4OAc (60 mg, 0.78 mmole), acetic anhydride (1.0 ml) in 5 ml acetic acid was kept at 100 °C for 24 hours. The dark-red reaction mixture was cooled and the acetic acid/acetic anhydride was removed by vacuum distillation. The residue was extracted with ether (4x10 ml) and the combined ether was washed with 5% sodium bicarbonate solution (3x15 ml), water (2x15 ml), saturated NaCl (2x10 m1) and dried with sodium sulfate. Removal of the solvent by a rotary evaporator gave a tan colored residue as the crude product. Column chromatographic purification over silica gel with hexanes/ether (97/3) as eluent gave the 2,5-di(5-(3',4'-dibuty1-2,2',5',2"-terthieny1))pyrrole(85) as an orange solid. Yield: 14 mg (25%). m.p.= 141-142 °C (uncorrected). 1H- NMR(CDC13):7.28-6.94(m, 12H), 2.69-2.57(m, 8H), 1.60-1.44(m, 8H), 1.40-1.35(m, 811), 0.95-0.90(m, 12H); 13C-NMR(CDC13): 140.9, 140.2, 138.7, 136.9, 136.2, 135.8, 135.0, 130.1, 129.0, 127.1, 126.4, 125.5, 125.1, 123.0; EI-MS, mlz(relative intensity): 783(M", base), 740(12.6), 712(9.7), 698(21.8), 343(9.6), 301(4.09). High resolution mass spectra, calculated for C44H49N85: 784.202, found: 784.147. UV- Vis(maximum absorption): 437nm (CHC13). 172 Synthesis of 2,5-di(5-(3’,4'-dibutyl-2,2',5',2"-terthienyl))-1,3,4- thiadiazole(86): A mixture of 5-formyl-3',4'-dibutyl-2,2',5',2"-terthiophene (120 mg, 0.31 mmole), hydrazine monohydrate (7.7 mg, 0.15 mmole), elemental sulfur (60 mg, 1.87 mmole), and tributyl amine (20 mg, 0.11 mole) in 10 ml of propylene glycol was heated at 120 °C for 48 hours. Then, the reaction mixture was cooled to room temperature and the precipitate was collected by suction filtration. The solid was washed with ice-cold methanol (3x10 ml), carbon disulfide (3x10 ml) and then dried in vacuum to give a dark-red solid as crude product. Column chromatographic purification over silica gel with hexanes/ether/ethyl acetate (85/5/10) as the eluent followed by crystallization from hexanes/ethyl acetate (90/10) gave the expected 2,5-di(5-(3',4'-dibutyl-2,2',5',2"-terthienyl))-1,3,4-thiadiazole(86) as orange needles. Yield: 14 mg (12%). m.p.=206-208 °C (decomp.). 1H-NMR(CDC13): 7.50(d, J=4.3Hz, 211), 7.30(dd, 1:6.8. 1.1112, 2H), 7.16(dd, J=3.9, 1.1Hz, 2H), 7.10(d, J=4.3Hz, 2H), 7.05(dd, J=6.8, 3.9Hz, 2H), 2.75(t, J=8.1Hz, 4H), 2.70(t, J=8.1Hz, 4H), 1.60-1.52(m, 8H), 1.49- 1.43(m, 8H), 0.96-0.93(m, 1211); ‘3C-NMR(CDCI3): 161.3, 142.7, 141.0, 140.2, 135.1, 134.6, 131.9, 129.4, 127.0, 125.8, 125.4, 124.6, 124.0, 32.4, 32.1, 28.3, 28.0, 22.7(2), 13.6(2). EI-MS, mlz(relative intensity): 802(M", 7.4), 759(5.1), 417(base), 385(20.7), 359(4.7), 344(8.1). High resolution mass spectra, calculated for C42H46N2S7: 803.228, found: 803.169. UV—Vis(maximum absorption): 417nm (CHClg). 173 Synthesis of 2,2'-di(5-(3',4'-2,2':5',2"-terthienyl))-thiazolo[5,4- d]thiazole(87): A mixture of 5-formyl-3',4'-dibutyl-2,2',5‘,2"-terthiophene(89) (388 mg, 1.0 mmoles), dithiooxamide (60 mg, 0.5 mmoles) and DMF (5 ml) was refluxed gently under N2 for 30 minutes. Then the dark- red reaction mixture was cooled to room temperature and poured into water (20 ml), and extracted with CHC13(3x15 ml). The combined organic layers was washed with water (2x15 ml) and dried with sodium sulfate. Removal of the solvent by a rotary evaporator gave a dark-red solid as the crude product. Column chromatographic purification over silica gel with hexanes/ethyl acetate (92/8) as the eluent followed by crystallization from hexanes/CH2CL2 (90/10) gave the 2,2'-di(5-(3',4'-2,2':5',2"-terthienyl))thiazolo[4,5-b]thiazole(87) as orange-red solid. Yield: 146 mg (34%). m.p.=178 °C (decomp.). 111- NMR(CDCI3): 7.47(2H, d, J=4.3Hz), 7.31(2H, dd, J=5.6, 1.1Hz); 7.14(2H, dd, J=4.0, 1.1112), 7.11(2H, d, J=4.3Hz), 7.06(2H, dd, J=5.6, 4.0Hz), 2.77(4H, t), 2.70(4H, t), 1.55(8H, m), 145(8H, m), 0.94(12H, m). EI-MS, m/z (relatively intensity): 858(M+, 30.06), 42900“, 9.01), 374(23.47), 344(13.96), 331(10.74), 300(11.20), 289(11.66), 127(17.79), 121(11.35), 111(10.43), 97(19.33), 69(41.72), 64(43.56), 55(33.74), 44(base). UV-Vis(CHC13): 466nm. 174 Synthesis of 2,2'-dipyrrylthione(l46): A solution of pyrrole (5.0 g, 74.5 mmole) in dry ether (40 ml) was added dropwise to a vigorously stirred solution of thiophosgene (4.2 g, 36.5 mmole) in benzene (80 ml) at 0 °C. The addition took about 20 minutes. After the addition, the red reaction mixture was continuously stirred at 0 °C for 30 more minutes. Then 100 ml of aqueous methanol (80%) was added and the mixture was stirred at room temperature for one hour. The solvent was removed by a rotary evaporator and the dark-red residue was dissolved in CH2C12 (20 ml). Chromatographic purification on neutral alumina with hexanes/ether(80/20) as the eluent followed by crystallization from aqueous ethanol gave the 2,2‘-dipyrrylthione as lustrous red needles. Yield, 3.78g(59%). m.p=97-98 °C(lit."3 96 - 98 °C). lH-NMR (CDCl3): 9.76(s., br., 211), 7.18(m, 211), 7.03(m, 211), 6.40(m, 2H); 13C-NMR (CDCl3): 193.1, 138.3, 127.7, 114.8, 112.5; EI-MS(e/z, relative intensity): 178(M*+2, 5.58), 177(M*+1, 13.7), 176(M", base), 175(M+- 1, 34.4), 143(18.4), 109(58.2), 89(7.3), 83(8.7), 67(20.3), 39(14.3). Synthesis of 2,2'-dipyrrylketone(l47): 20 ml 5% aqueous hydrogen peroxide was added portion-wise to a vigorously stirred solution of 2,2'-dipyrrylthione (1.0 g, 5.7 175 mmole) in ethanol (95%; 120 ml) containing 2.0 g (35.7 mmole) potassium hydroxide. After the addition, the mixture was continuously stirred at room temperature for 30 minutes and then heated on a steam bath for 30 more minutes. The reaction mixture was then poured into 300 ml of water. The white precipitate was collected by suction filtration and dried in vacuum. Further purification by sublimation (200 °C/1 mm) gave the 2,2'- dipyrrylketone as white powder. Yield 0.69 g (76%). m.p.=159-160 °C. 1H-NMR(CDC13): 9.92(s, br., 2H), 7.14(m, 2H), 7.07(m, 2H), 6.34(m, 2H); 13C-NMR(CDCL3): 110.5, 115.6, 123.6, 130.1, 171.8; EI-MS(e/z, relative intensity): 161(M*+1, 9.75), 160(M“, base), 104(10.9), 94(72.4), 67(81.3), 66(42.2), 51(6.1), 39(31.3). Synthesis of 2,2'-dipyrrylmethane(l48): Sodium borohydride (1 g each, 6 g total) was added portionwise over 3 hours to a solution of 2,2'-dipyrrylketone (2.0 g, 12.5 mmole) in refluxing ethanol (95%, 50 ml) containing 2.0 ml of morpholine under nitrogen. Every time after the addition of a portion of borohydride 3.0 ml of water was added. After the addition of all the sodium borohydride the reaction mixture was refluxed for two hours, then cooled to room temperature and poured into 100 ml of water. The solvent was removed by vacuum distillation and the residue was extracted with petroleum ether. The combined petroleum extracts were concentracted and cooled in -10 °C to give 176 2,2'-dipyrrylmethane as colorless needles (yield, 1.68 g, 92%). m.p.=72-73 °C(lit.113 73 °C). ‘H-NMR(CDC13): 7.82(s, br., 2H), 6.65(m, 2H), 6.16(m, 2H), 6.05(m, 2H), 3.97(s, 2H); l3C-NMR(CDCL3): 128.8, 117.3, 108.3, 106.4, 26.3; EI-MS(e/z, relative intensity): 147(M"+1, 10.4), 146(M+, base), 145(M+-1), 73.6), 118(17.5), 117(17.5), 80(40.2), 67(28.4), 53(11.6), 39(10.5). Synthesis 5,5'-diformyl-2,2'-dipyrrylmethane(149): To a stirred solution of 2,2'-dipyrrylmethane (1.2 g, 8.2 mmole) in dry N,N-dimethylformamide (10 ml) at 0°C, 6.0 ml of benzoyl chloride was added dropwise over 10 minutes under nitrogen. After the addition, the reaction mixture was stirred at this temperature for 2 hours and then at room temperature for 5 hours. Then an excess of 10% aqueous sodium acetate solution (20 ml) was added and the mixture was stirred at room temperature for five hours and heated on a steam-bath for 20 minutes. The mixture was diluted with water (30 ml) and the precipitate was collected by filtration. Recrystallization from ethanol gave the 5,5'-diformyl-2,2'- dipyrrylmethane as colorless needles. Yield, 1.39 g (84%). m.p.=231- 232 °C(dec.) (lit.113 229-231 °C). lH-NMR(Acetone-d5): 11.2(s, br., 2H), 9.41(s, 2H), 6.90(d, J=4.0Hz, 2H), 6.13(d, J=4.0Hz, 2H), 4.16(s, 2H); l3C-NMR(DMSO-d6): 178.4, 138.2, 132.3, 121.3, 109.6, 25.6; E1- MS(e/z, relative intensity): 203(M++1, 11.5), 202(M“, base), 173(23.9), 145(41.7), 117(11.3), 108(17.4), 94(10.2), 80(12.6), 67(6.4), 53(9.62), 51(8.5), 39(8.4). 177 Synthesis of ethyl 5-acetoxymethyl-3,4-dimethylpyrrole-2- carboxylate(152): Lead tetra-acetate (12.0 g, 27.1 mmole) was added to a solution of ethyl 2,3,4-trimethylpyrrole-5-carboxylate (4.9 g, 27.1 mmole) in 120 ml glacial acetic acid at room temperature over 10 minutes with vigorously stirring. After the addition, stirring was continued for two more hours. Then, the acetic acid was removed by vacuum distillation. The residue was poured into water (200 ml) and the precipitate was collected by filtration, washed with water and dried in vacuum. Crystallization from aqueous acetone gave the ethyl 5- acetoxymethyl-3,4-dimethylpyrrole-2-carboxylate(152) as colorless needles. Yield: 5.47 g (85%). m.p.=132-133 °c (lit.116 132 °C). lH-NMR (CDCl3): 11.8(s, br., 2H), 4.97(s, 2H), 4.30(q, 1: Hz, 2H), 2.31(s, 3H), 2.02(s, 3H), 1.97(s. 3H), 1.36(t, 1: Hz, 3H). Synthesis of diethyl 3,3',4,4'-tetramethyldipyrrylmethane-5,5'- dicarboxylate(153): A solution of ethyl 5-acetoxymethyl-3,4-dimethylpyrrole-2- carboxylate (4.2 g, 17.6 mmole) in ethanol (120 ml) containing 3 ml concentrated hydrochloric acid was kept at reflux for two hours. Then the reaction mixture was cooled in ice-bath and the precipitate was collected by suction filtration. The solid crude product was washed with ethanol and dried in vaccum. Recrystallization from 178 ethanol gave the diethyl 3,3',4,4'-tetramethyldipyrrylmethane-S,5'- dicarboxylate(153) as white solid. Yield: 2.40 g (79%). m.p.=l96-l98 °C(lit.116 198 °C). 1H-NMR(CDC13): 12.1(s, br., 2H), 4.34(q, 4H), 4.06(s, 2H), 2.07(s. 6H), 1.98(s, 6H); Synthesis of 3,3',4,4'-tetramethyldipyrrylmethane(154): A mixture of diethyl 3,3',4,4'-tetramethyldipyrromethane-5,5'- dicarboxylate (1.5 g, 4.3 mmole) and sodium hydroxide (0.69 g, 17.2 mmole) in 20 ml ethanol (95%) was heated at reflux under nitrogen for 24 hours. Then, the reaction mixture was cooled in ice water and acidified with acetic acid. The ethanol/acetic acid was removed by vacuum distillation. Then 5 ml of ethylene glycol was added to the residue and the mixture was stirred at 170°C under N2 for 5 hours, cooled to room temperature and poured into 100 ml of water. The mixture was extracted with ether (3x30 ml) and the combined ether extracts was washed with water (2x20 ml), 5% aqueous sodium bicarbonate solution (2x20 ml) and dried with sodium sulfate. Column chromatographic purification over nutral alumina with hexanes/CH2C12 (80/20) as the eluent gave the expected 3,3',4,4'- tetramethyldipyrrylmethane(154) as white solid. Yield: 396 mg (92%). m.p.=88-89 °c (lit.“° 87-88 °C). lH-NMR(CDCI3): 8.27(s. br. 211), 6.38(s, 211), 4.10(s, 2H), 1.96(s, 6H), 1.84(s, 611). 13C-NMR(CDC13): 130.2, 127.4, 119.7, 108.5, 27.0, 14.1, 13.9. 179 Synthesis of 5,5'-diformyl-3,3',4,4'-tetramethyl-2,2'- dipyrrylmethane(l49): Benzoyl chloride(6ml) was added to a stirred solution of 3,3',4,4'-tetramethyl-2,2'-dipyrrylmethane (3.0 g) in N,N- dimethylformamide(DMF) (20 ml) at 0 °C. The reaction mixture rapidly turned to a thick paste. After the addition the mixture was kept at 0 °C with magnetically stirred for one hour. Then, the reaction mixture was diluted with ether (50 ml) and poured into water (10 ml). An excess sodium acetate in ethanol/water (70/30) was added and the mixture was warmed on a water-bath at 30 °C for two hours. The precipitate 5,5'-diformyl-3,3',4,4'-tetramethyl-2,2'- dipyrrylmethane was collected by suction filtration. Recrystallization from ethyl acetate/CHC13(20/80) gave the 5,5'-diformyl-3,3',4,4'- tetramethyl-2,2'-dipyrrylmethane as cream needles. Yield (84%). m.p.=296-298 °C(1it.116 293 °C). lH-NMR(CDC13): 12.3(s, br., 2H), 9.46(s, 2H), 4.27(s, 2H), 2.05(s, 611), 1.97(s. 6H); 13C-NMR(CDC13): 176.9, 139.7, 134.2, 129.1, 121.8, 25.9, 13.8, 13.5. Synthesis of 5,5"-bisformyl-3',4'-dibutyl-2,2',5',2"- terthiophene(155): (a), Synthesis of 5,5"-diformyl-3',4'-dibutyl-2,2',5',2"- terthiophene(155) by the lithiation of the 2,2',5',2"- terthiophene followed by the reaction of the lithiated compound with N,N-dimethylformide(DMF): 180 BuLi (2.8 ml of 1.6M in hexanes solution,2.2 eq.) was added to a cooled (-50 °C) mixture of 3',4'-dibutyl-2,2',5',2"-terthiophene (720 mg, 2.0 mmole), tetramethylethenediamine (TMEDA, 400 mg) and 40 ml haxanes by a syringe under N2. After the addition, the reaction mixture was stirred at -50 °C for 30 minutes and then stirred at room temperature for another 30 minutes. The reaction mixture was recooled to -78 °C and 2.2 eq. of dimethyformamide (DMF) in 5 ml of ether was added slowly by a syringe. After the addition the reaction mixture was warmed slowly to room temperature, and stirred for one hour and then poured into 200 ml of 2% ice cold aqueous HCl solution with vigorously stirring. The mixture was extracted with CH2C12 (4x30 ml) and the combined organic extracts were washed with water, saturated sodium bicarbonate and brine. Dried with M gSO4. Removal of the solvent by a rotary evaporator gave a dark- colored residue as the crude product. Column chromatographic purification over silica gel with hexanes/ether/CH2C12 (65/20/15) as the eluent gave the expected 5,5"-diformyl-3',4'-dibutyl-2,2',5',2"- terthiophene(155) as orange needles. Yield, 674 mg (81%). m.p.=92- 93 °C (uncorrected). lH-NMR(CDCl3): 9.91(s, 2H), 7.73(d, J=4.5Hz, 211), 7.27(d, J=4.5Hz, 2H), 2.78(t, J=8.9Hz, 4H), l.54(m, 4H), 1.48(m, 4H), 0.97(t, J=7.9Hz, 6H); l3C-NMR(CDC13): 13.8, 22.9, 28.0, 32.5, 126.7, 130.5, 136.7, 142.8, 142.9, 145.6, 182.6; EI-MS(e/z, relative intensity): 418(M*+2, 16.4, 417(M++1, 25.2), 416(M", base), 345(23.9), 331(7.3), 303(42.0), 288(6.1), 275(5.6), 270(5.5), 240(6.6), 227(5.6), 127(6.6), 41(7.l). UV-Vis(maximum absorption): 404nm (CHC13). 181 (b), Synthesis of 5,5"-diformyl-3',4'-dibutyl-2,2',5',2"- terthiophene(155) by Vilsmeier reaction: To a stirred solution of 3',4'-dibutyl-2,2',5',2"-terthiophene(1.8 g, 5.0 mmole) in dry N,N-dimethylformamide (10 ml) at 60 °C, an excess of POC13 (2.50 g, 16.3 mmole) was added dropwise over 10 minutes under nitrogen. After the addition, the reaction mixture was stirred at this temperature for two hours and at 80 °C for two more hours. Then an excess aqueous sodium acetate solution (20 ml, 10%) was added. The mixture was stirred at room temperature for five hours and heated on a steam-bath for 30 minutes. Then the mixture was diluted with 30 ml of water and the precipitate was collected by filtration. Coluum chromatographic purification over silica gel with hexanes/CH2C12 (50/50) as the eluent followed by crystallization from ethanol gave the 5,5"-diformyl-3',4'-dibutyl-2,2',5',2"- terthiophene(155) as orange needles. Yield, 1.60 g (77%). All the physical properties are the same as those from the lithiation procedure( a). Synthesis of 5,5"-bisacetyl-3',4'-dibutyl-2,2',5',2"-terthiophene(l60): To a mixture of 3',4'-dibutyl-2,2',5',2"-terthiophene (360 mg, 1.0 mmole) and acetyl chloride (173 mg, 2.2 mmole) in 20 ml dry dichloromethane was added SnCl4 (570 mg, 2.2 mmole, in 2 ml of dichloromethane). The resulting red mixture was stirred at room temperature for two hours. Then, the reaction was quenched with 182 10ml 3% HCl aqueous solution. The organic layer was separated and the aqueous layer was extracted with CH2C12 (2x10 ml). The combined organic layers were washed with H2O (2x20 ml), 5% NaHC03 (2x20 ml) and saturated NaCl (20 ml), dried with magnesium sulfate. Removal of the solvent gave an orange solid residue as the crude product. Column chromatographic purification over silica gel with hexanes/ethyl acetate (85/15) as the eluent followed by crystallization from hexanes/CH2C12 (90/10) gave the expected 2,5"- bisacetyl-3',4'-dibutyl-2,2',5',2"-terthiophene(l60) as orange needles. Yield:373 mg (84%). m.p.=96.0-96.5 °c (uncorrected). 111- NMR (CDCl3): 7.61(d, J=4.5Hz, 2H), 7.15(d, J=4.5Hz, 2H), 2.77(t, J=8.2Hz, 4H), 2.55(s, 6H), l.54(m, 4H), 1.50(m, 4H), 0.94(t, J=8.1Hz, 6H); l3C-NMR (CDCL3): 190.5, 144.2, 143.4, 142.2, 132.8, 130.5, 126.5, 32.6, 27.9, 26.6, 22.9, 13.8; EI-MS, e/z(relative intensity): 446(M*+2, 14.5), 445(M++1, 24.6), 444(M+, base), 401(5.6), 361(8.5), 360(12.9), 359(57.9), 318(7.1), 317(30.0), 316(13.5), 301(5.2), 274(6.1), 259(2.7), 227(3.3), 207(6.0), 169(3.6), 127(8.6), 97(2.2), 43(88.6). UV-Vis(maximum absorption): 395nm (CHCl3). Synthesis of 5,5"-bisformyloxime-3‘,4'-dibutyl-2,2',5',2"- terthiophene(167): A mixture of 5,5"-bisformyl-3',4'-dibutyl-2,2',5',2"- terthiophene (300 mg, 0.72 mmole), hydroxyamine hydrochloride (200 mg, 2.88 mmole), sodium acetate (200 mg, 2.44 mmole) and 100 ml absolute ethanol was kept at 65 °C for two hours. Then the 183 ethanol was removed by a rotary evaporator to give a yellow colored residue which was subsequently extracted with CH2C12 (4x20 ml). The combined CH2C12 extracts were washed with water (2x20 ml) and dried with sodium sulfate. Removal of the solvent gave a yellow solid as the crude product which was determined by lH-NMR to be >96% pure. 1H-NMR results show that it is a mixture of three isomers. Yield is quantitative. Column chromatographic purification over silica gel with ethyl acetate/hexanes (50/50) as the eluent followed by crystallization from ethanol gave one of the isomers as yellow needles. m.p.=169-170 °C (decomp.). lH-NMR(DMSO-d5): 7.86(s, 2H), 7.46(d, J=4.5Hz, 2H), 7.24(d, J=4.5Hz, 2H), 2.70(m, 4H), l.54(m. 4H), 1.48(m, 411), 0.91(t, J=7.9Hz, 6H). 13C-NMR(DMSO-d6): 142.6, 139.8, 139.1, 134.7, 131.0, 129.1, 124.3, 31.6, 26.6, 21.7, 12.9; EI-MS(e/z, relative intensity): 446(M*, 15.5), 428(M+-18, 62.7), 410(M+-36, base), 385(6.25), 367(12.8), 353(10.4), 343(19.5), 325(82.6), 310(14.8), 300(20.1), 292(14.5), 266(11.l), 252(10.1), 152(30.0), 146(10.6), 134(10.1), 69(12.8), 55(17.1), 43(21.3), 41(31.0); Synthesis of 5,5"-biscyanol-3',4'-dibutyl-2,2',5',2"- terthiophene(l68): The 5,5"-bisformyloxime-3',4'-dibutyl-2,2',5',2"-terthiophene (167) (305 mg, 0.68 mmole) in 50 m1 acetic anhydride was stirred at 100 °C under N2 for ten hours. Then, the acetic anhydride was removed by vacuum distillation. 50 ml of water was added to the residue and the mixture was stirred at room temperature for 30 184 minutes. The product was extracted with CH2C12 (2x30 ml) and the combined organic layers were washed with water (2x15 ml), 5% sodium bicarbonate solution (2x15 ml), saturated NaCl solution (20 ml) and dried with sodium sulfate. Removal of the solvent by a rotary evaporator gave a dark-orange solid as the crude product. Column chromatographic purification over silica gel with ethyl acetate/hexanes (15/85) as the eluent gave the first orange band as the expected 5,5"-biscyanol-3',4'-dibutyl-2,2',5',2"-terthiophene (168). Yield: 187 mg (67%). m.p.=77-78 °C (uncorrected). lH-NMR (CDCl3): 7.56(d, J=4.4Hz, 2H), 7.12(d, J=4.4Hz, 2H), 2.70(t, J=7.7Hz, 4H), l.38-1.56(m, 8H), 0.95(t, J=7.8Hz, 6H); ’3C-NMR(CDCL3): 182.0, 142.1, 137.3, 128.9, 125.6, 113.5, 108.6, 32.2, 27.5, 22.5, 13.4; EI-MS(e/z, relative intensity): 412(M++2, 14.8), 411(M"+1, 23.9), 410(M“, base), 353(8.32), 327(10.9), 326(17.4), 35206.2), 312(5.46), 311(7.73), 310(11.2), 292(11.2), 291(7.32), 151(28.3), 122(12.3), 57(7.53), 55(14.0), 43(14.4). UV-Vis(maximum absorption): 371nm (CHCl3). Further elution with the same solvent gave 5,5"-bisformyl- 3',4'-dibutyl-2,2',5',2"-terthiophene (5.7 mg, 2%) as by-product with a recovery of starting material 5,5"-bisformyloxime-3',4'-dibutyl- 2,2',5',2"-terthiophene (9.0 mg, 3%). Synthesis of 5,5"-bisaminomethyl-3',4'-dibuty1-2,2',5',2"- terthiophene(l64): 185 A mixture of the 2,5"-biscyanol-3',4'-dibutyl-2,2',5',2"- terthiophene(l68) (200 mg. 0.49 mmole), LiAlH4 (100 mg, 2.63 mmole) in 10 ml tetrahydrofuran was stirred at room temperature under N2 for two hours. Then, the reaction was quenched with water (50 ml) and the product was extracted with ether (4x20 ml). The combined ether extracts were washed with 5% sodium bicarbonate solution (2x20 m1), saturated NaCl solution (20 ml) and dried with sodium sulfate. Removal of the solvent by a rotary evaporator gave a wax-like residue as the crude product. Column chromatographic purification over neutral alumina with hexanes/ether (60/40) as the eluent followed by crystallization from hexanes gave the 5,5"- bisaminomethyl-3',4'-dibutyl-2,2',5',2"-terthiophene(164) as orange solid. Yield: 187 mg (92%). m.p.=37-38 °c (uncorrected). lH-NMR (CDC13): 6.92(d, J=4.0Hz, 2H), 6.80(d, J=4.0Hz, 2H), 4.0(s, 4H), 2.66(t, J=8.5Hz, 4H), 1.71(s, br., 4H), 1.50(m, 4H), 1.41(m, 4H), 0.92(t, J=7.9Hz, 611); 13C-NMR(CDCL3): 147.1, 139.6, 134.2, 129.6, 125.3, 123.8, 41.4, 32.8, 27.6, 22.8, 13.7; EI-MS, e/z(relative intensity): 420(M++2, 13.7), 419(M++1, 22.2), 418(M“, base), 404(4.07), 403(6.07), 402(23.8), 385(4.16), 375(3.27), 358(4.27), 346(5.72), 331(5.37), 330(6.93), 329(28.9), 285(7.16), 112(6.46), 97(4.87), 68(4.75), 56(6.54), 41(5.90); Synthesis of macrocycle tetrabutylhexathiophenecine(l66): 186 The 5,5"-bisaminomethyl-3',4'-dibutyl-2,2',5',2"- terthiophene(164) (150 mg, 0.36 mmole) in 200 ml methanol was kept at reflux under N2 for 24 hours. Then the methanol was removed by a rotary evaporator, and 30 ml of CH2C12 and 20 ml of water was added to the brown colored residue. The insoluble dark colored resin-like product was separated by filtration, washed with water and cold methanol, and dried in vacuum. Yield: 67 mg (45% by weight). This compound was identified as a polymeric material by 1H-NMR and mass spectra. The CH2C12 layer was separated from the filtrate and the aqueous layer was extracted with CH2C12 (3x10 ml). The combined CH2C12 extracts were washed with water (2x20 ml), 5% NaHCO3 aqueous solution (2x20 ml), saturated NaCl aqueous solution (20 ml) and dried with sodium sulfate. The solvent was removed by a rotary evaporator until about 5 ml left. Then, about 20 ml of ethanol was added and the mixture was kept in dark with air bubbling through it for five days. Then the solvent was removed by a rotary evaporator to give a dark-colored residue. Column chromatography over neutral alumina with hexanes/ethyl acetate/CH2C12 (65/20/15) as the eluent gave the first dark-orange band which was collected. The solvent was removed and the residue was further purified by column chromatography over silica gel with hexanes/ethyl acetate/CH2C12 (60/15/25) as the eluent. Recrystallization from ethanol/ethyl acetate(85/15) gave the expected macrocycle (166) as purple lustre needles. m.p.=254-255 °C (uncorrected). Yield: 2.15 mg(1.5% based on the starting 5,5"-bisaminomethyl-3',4'-dibutyl-2,2',5',2"- terthiophene(164)). lH-NMR(CDC13): 8.21(s, 411), 7.54(d, J=4.4Hz, 4H), 187 7.38(d, 4.4Hz, 4H), 2.63(t, J=6.9Hz, 8H), l.31-1.68(m, 16H), 0.91(t, =7.8112, 1211). 13C-NMR(CDC13): 158.4, 143.5, 140.2, 135.8, 131.9, 127.2, 124.0. High resolution mass spectra, calculated for C44H43N286, 797.204, found: 797.158. UV-Vis(maximum absorption): 483nm (CHCl3)- MAWNF‘ 10. 11. 12. 13. 14. 15. List of References Reynolds, J. R., Chemtech. 1988, 440; Kanatzidis, M. G., C&EN, 1990, Dec. 3, 36-54; Heinze, J., Synthetic Metals, 1991, 43, 2805; Garnier, F., Angew. Chem. Int. Ed. 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