Synthesis of novel benzimidazolyl-substituted acrylonitriles and amidino-substituted benzimidazo[1,2-a]quinolines

A series of novel benzimidazole derivatives 3-10 were synthesized. Benzimidazolyl-substituted acrylonitriles 3 and 4 underwent a photochemical dehydrocyclization reaction to give the corresponding mono- and dicyano-substituted benzimidazo1,2-a] quinolines 5 and 6. Pinner reaction of these compounds did not give the expected mono- and diamidines, but rather only compounds 7-10, with amido groups at 6-position were isolated. A mechanism for the reaction is proposed. Acyclic compounds 3 and 4, as well as cyclic benzimidazo1,2-a]quinolines 5-8, exhibit interesting spectroscopic properties and are potential biologically active compounds.