Condensed imidazo-1,2,4-azines. 21. Synthesis of 2-arylfuro(pyrrolo-, thieno-)[2,3-e]-1,2,4-triazino[2,3-a]benzimidazoles by cyclization of 2-aroyl-1,2,4-triazino[2,3-a]benzimidazol-4H-3-ones

2-(-Ethyl-, arylimino)phenethyl]-1,2,4-triazino2,3-a]benzimidazoles were obtained by reaction of 2-aroylmethyl-1,2,4-triazino2,3-a]benzimidazol-4H-3-ones with ethyl(aryl)amines or urea. By the action of phosphorus oxychloride, these benzimidazoles cyclize into substituted pyrrolo2,3-e]-1,2,4-triazino2,3-a]benzimidazoles, heating of which in polyphosphoric acid leads to the formation of furo2,3-e]-1,2,4-triazino2,3-a]benzimidazoles, while by the action of P₄S₁₀, they are transformed into thieno2,3-e]-1,2,4-triazino2,3-a]benzimidazoles.For Communication 20, see 1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1109–1113, August, 1989.