On triazoles XLII [1,2]. A new convenient method for the N-alkylation of highly insoluble cyclic amides

Abstract

A simple N-alkylation method of highly insoluble cyclic amides based on the high solubility of their easily isolable tetraalkylammonium and tetraalkylphosphonium salts was elaborated. The method has a rather wide scope, it is not influenced by the identity of the different rings attached to the 1,2,4-triazolo[1,5-a]-pyrimidinone moiety of isomers 1 and 2, nor the presence of the triazole substituents. It proceeds smoothly without any unwanted by-products, at relatively low temperatures, and is not sensitive to moisture. The method allows an easy isolation of all possible N-alkylated derivatives 3, 7, and 8. Spectral analysis of isomers 3, 7, and 8 showed that our previous results concerning the formation of 3 type N-alkylated derivatives as main products of the N-alkylations as well as the tautomeric structure of the non-alkylated isomers 1 and 2 is correct. However, it also showed that the isolation of a single N-alkylated isomer 3 and its comparison with the corresponding non-alkylated derivative to prove its tautomeric structure may lead to mistakes.