Benzazole derivatives, IV: Reaction of 1,2,3-trimethylbenzimidazolium salts with aromatic aldehydes

1,2,3-Trimethylbenzimidazolium iodide and its analogue salts with one or two substituents on benzene ring (X=NO2,Br,Cl,CH3) are, due to the reactivity of the 2-methyl group, able to react with para-substituted aromatic aldehydes (X=OH,OCH3,CH3,NMe2,NO2) using piperidine as a catalyst. 1-Methyl-2-styrylbenzimidazole iodomethylates were obtained and their structure elucidated by means of NMR and IR spectroscopy. The compounds are interesting as hemicyanine dyes. They lend themselves to studies based on electronic absorption spectroscopy and they have potential practical applications linked to their photosensitive properties.