Condensed imidazo-1,2,4-azines. 15. Reaction of 1,2-diaminobenzimidazole with 5-phenyl-2,3-dihydrofuran-2,3-dione

The reaction of 1,2-diaminobenzimidazole with 5-phenyl-2,3-dihydrofuran-2,3-dione in acetic acid gave a mixture of 2-benzoylmethyl-1,2,4-triazino 2,3-a]-benzimidazol-4H-3-one and 3-benzoylmethyl-1,2,4-triazino2,3-a]benzimidazol-1H-2-one, the intramolecular cyclization of which gave isomeric 2-phenylfuro-5,4-e]- and 2-phenylfuro4,5-e]-1,2,4-triazino2,3-a]benzimidazoles. Only the corresponding furo4,5-e]-1,2,4-triazino2,3-a]benzimidazole was isolated when the reaction was carried out in sulfuric acid.See 1] for Communication 14.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 533–535, April, 1987.