The reaction between 4-methoxy-2,6-dimethylpyrylium perchlorate and amines. Isolation of both 4-iminiopyran salts and pyridinium salts in the reaction with primary amines

Abstract

Both 4-aryliminio-2,6-dimethylpyran salts (5) and 1-aryl-4-methoxy-2,6-dimethylpyridinium salts (13) can be isolated from the reaction between 4-methoxy-2,6-dimethylpyrylium perchlorate (12) and aromatic primary amines, the ratio of products depending upon the basicity of the amine. Separation of the mixture by conversion of the iminiopyran salts into the hitherto unknown 4-arylimino-,6-dimethylpyrans (6) is described. Secondary aromatic amines studied gave only 2-(2,6-dimethylpyran-4-ylidenemethyl)-4-methoxy-6-methylpyrylium perchlorate (18), and the well-known reaction with methylamine was found to give an additional product not previously recorded, 2,6-dimethyl-4-methyliminiopyran perchlorate (21m) in 21% yield. I.r., ¹H n.m.r., and mass spectra of iminiopyran salts, iminopyrans, and pyridinium salts are discussed.