Synthesis and some transformations of trans-1-methyl-2-[β-(2′-thienyl)vinylene]-1H-benzimidazole

The condensation of 1,2-dimethylbenzimidazole with thiophene-2-aldehyde in the presence of fused zinc chloride results in 1-methyl-2-[β-(2-thienyl)vinylene]-1H-benzimidazole. Its electrophilic substitution reactions (nitration, bromination, sulfonation, formylation, acylation) were studied. All the reactions occur in the 5-position of the thiophene ring. Only in the case of bromination in dichloroethane 5′,5(6)-dibromo-derivative was obtained. Data of the quantum-chemical calculations of the total positive charge on the carbon atoms of the protonated molecules of thienylbenzimidazoles including the vinylene group and without it are reported.