Preparation of all-trans-(1,4-phenylenehexa-1,3,5-trienylene) oligomers

Abstract

All-trans-(1,4-phenylenehexa-1,3,5-trienylene) oligomers, all-trans-1,4-bis(6-phenylhexa-1,3,5-trienyl)benzene (PHT2) and all-trans- 1,6-bis[4-(6-phenylhexa-1,3,5-trienyl)phenyl] hexa-1,3,5-triene (PHT3), were prepared respectively by the Wittig reaction from 1,4-phenylenediacrylaldehyde or 1,6-bis[4-(2-formylvinyl)phenyl]hexa-1,3,5-triene. The ¹H NMR, IR and UV–VIS spectra of the crude oligomers indicated the presence of cis double bonds in the trienes. The cis–trans isomerization of these double bonds was carried out by heating the cis-containing crude product in an appropriate solvent with iodine catalysis. The structures of PHT2 and PHT3 were confirmed by comparison of their IR spectra with that of all -trans- 1,6-diphenyihexa-1,3,5-triene.