Synthesis of azolo[5,4-c]isoquinolines

Two pathways are presented for the synthesis of pyrazolo[5,4-c]isoquinoline derivatives: recyclization of 1-methyl-3-phenyl-4-cyano-6,7-dimethoxybenzo[c]pyrylium perchlorate upon treatment with hydrazine, and Bischler-Napieralski cyclization of substituted 5-amino-4-(3,4-dimethoxyphenyl)pyrazoles. A derivative of a new heterocyclic system, isoxazolo[5,4-c]isoquinoline, has also been obtained upon heating 5-amino-3-phenyl-4-(3,4-dimethoxyphenyl)isoxazole in a mixture of acetic anhydride and perchloric acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1092–1095, August, 1990.