Studies on Pyrimidine Derivatives. III

Abstract

Reaction of 2-hydrazino-4, 6-dimethylpyrimidine (IV) and orthoformic acid ester afforded 5, 7-dimethyl-1, 2, 4-triazolo [4, 3-a] pyrimidine (III) while boiling of (IV) with formic acid first gives the formylhydrazino compound (V) which undergoes cyclization to (III). (III) is isomerized during the reaction to 5, 7-dimethyl-1, 2, 4-triazolo [2, 3-a] pyrimidine (II), which agrees with the product obtained from condensation of 5-amino-1, 2, 4-triazole (I) and acetylacetone. Similar reaction of 2-hydrazinopyrimidine (X) afforded 1, 2, 4-triazolo [4, 3-a] pyrimidine (XIII) and 1, 2, 4-triazolo [2, 3-a] pyrimidine (XII). (XIII) was found to undergo isomerization to (XII).