Reaction of methyl-substituted pyrylium salts with tertiary amines

2,4,6-Trimethylpyrylium perchlorate reacts with heterocyclic compounds containing apyridine nitrogen atom and having basicities higher than 9 pK_a units (in acetonitrile) through a step involving the formation of a methylenepyran. 4-Methyl-2,6-diphenyl- and 2-methyl-4,6-diphenylpyrylium perchlorates react with benzimidazole to give 1,2-ethanediylidenebispyrans. Methyl-substituted pyrylium salts react with 2,6-diphenylpyrylium and flavylium perchlorates in the presence of benzimidazole to give methylidynecyanines and with acetic anhydride to give trimethylidynecyanines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1484–1489, November, 1976.