SYNTHESIS OF CONJUGATED F-POLYENES CONTAINING THIENYL RING-SYSTEMS

Novel 1-substituted F-1,3-butadienes ThioAr-CF=CFCF=CF2, ThioAr = 2-th ienyl and 2-benzo[b]thienyl, and symmetrically 1,4-disubstituted F-1,3 -butadienes ThioAr-CF=CFCF=CF-ThioAr, ThioAr = 5-R'-2-thienyl (R' = Me , SiMe3, CF=CFCl), 3-thienyl, and 4-dibenzo[b,d]thienyl, inclusive of the above-named substituents, were prepared by the reaction of organol ithium derivatives with F-1,3-butadiene (PFBD). Monothioaryl-substitut ed F-1,3-butadienes were used as intermediates in subsequent reactions with other (thioaryl)organolithium derivatives for the synthesis of a new series of unsymmetrically substituted alpha,omega-bis(thioaryl)-F -polyenes ThioAr-(CF=CF)(n)-ThioAr', where n = 2, ThioAr, ThioAr' = 4- RC2H4 (R = H, Me, OC6H11, NMe2), 2-thienyl, 5-methyl-2-thienyl, 2-benz o[b]thienyl, 4-dibenzo[b,d]thienyl, and for n = 3, ThioAr = 2-thienyl, ThioAr' = 5-methyl-2-thienyl. The reaction of 2,5-dilithiothiophene w ith 1-(2-thienyl)-F-1,3-butadiene affords enyl)-1,2,3,4-tetrafluoro-1, 3-butadienyl]thiophene (5). 2,5-Thienylene-F-polyenylene polymers were prepared by the reaction of 2,5-dilithio- and 2,5-bis(bromomagnesio)t hiophene derivatives with PFBD and F-ethylene. The oligomers 5 and 2,5 -bis[2-(2-thienyl)-1,2-difluoroethylenyl]- thiophene (16) were found t o possess liquid crystalline properties. The reaction of 1,4-bis(2-thi enyl)-F-1,3-butadiene with nitric acid led to substitution in one or i n both thienyl rings at position 5. NMR, electronic spectra, and struc tural aspects of the title compounds are discussed.