Benzazole derivatives, VI: Synthesis of some 2-styrylbenzimidazoles and their quaternization

In this paper an alternative method for obtaining styrylbenzimidazolium iodides was described. Thus, some 1-methyl-2-styrylbenzimidazoles were synthesized by the condensation of 1,2-dimethylbenzimidazoles containing a mono- or di-substituted benzene ring (X = NO2, Br), at their reactive 2-methyl group with aromatic aldehydes by heating at high temperature. Some of the 2-styrylbenzimidazoles were proved to be able to convert into benzimidazolium quaternary iodides by treating them with methyl iodide in an autoclave. The structures of the 2-styrylbenzimidazoles and corresponding iodomethyl derivatives were investigated by IR and 1H-NMR spectral measurements. The obtained compounds are valuable due to their structures of polyenic dyes, with a photoexcitable ethylene bond.