Oxidative cyclization of 2-amino-1-arylideneaminobenzimidazoles into 1,2,4-triazolo[1,5-a]benzimidazoles

When heated in nitrobenzene, 1-arylideneamino-2-methylaminobenzimidazoles convert in a 20...30% yield into 2-aryl-3-methyl-1,2,4-triazolo[1,5-a]benzimidazoles. In addition, 2-methylaminobenzimidazole and the corresponding benzonitrile are formed as a result of a thermal splitting of the N-N bond. Under the same conditions, 2-amino-1-arylideneaminobenzimidazoles and 1-arylideneamino-3-methylbenzimidazoline-2-imines give only products of splitting off of the nitrile. In several cases, the subsequent reaction of the nitrile with 2-amino-1-methylbenzimidazole leads to the formation of benzamidines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1226–1231, September, 1988.