Addition reactions of heterocyclic compounds. Part XXXV. Methyl pyrimidines and methyl pyrazines with dimethyl acetylenedicarboxylate

Abstract

4,6-Dimethyl- and 2,4,6-trimethyl-pyrimidine, 4-methyl- and 2,4-dimethyl-quinazoline, and 2,5-dimethyl-pyrazine react with two molar proportions of dimethyl acetylenedicarboxylate to give azepines, with the shift of one ester group; in the last two cases further reaction with the ester occurs. 2,3,5,6-Tetramethylpyrazine reacts with the ester to give a dipyridopyrazine.