On triazoles XLII. A new convenient method for the N-alkylation of highly insoluble cyclic amides

A simple N-alkylation method of highly insoluble cyclic amides based on the high solubility of their easily isolable tetraalkylammonium and tetraalkyl phosphonium salts was elaborated. The method has a lather 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 o f the triazole substituents. It proceeds smoothly without any unwanted by-p roducts, 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 prev ious results concerning the formation of 3 type N-alkylated derivatives as main products of the N-alkylations as well as the tautomeric structure of t he non-alkylated isomers 1 and 2 is correct. However, it also showed that t he isolation of a single N-alkylated isomer 3 and its comparison with the c orresponding non-alkylated derivative to prove its tautomeric structure may lead to mistakes.