Studies on the chemistry of pharmacologically active heterocycles. Part I. Acid hydrolysis of hydrazino-1,2,4-triazine derivatives

The acid hydrolysis of 3-hydrazino-5,6-disubstituted-1,2,4-triazine, 3,5-dihydrazino-6-substituted-1,2,4-triazine, and 2-hydrazinopyrimidine derivatives was studied. It was found that the reaction proceeded through the formation of 3-keto and 3,5-diketo derivatives of the related 2,3-dihydro, 2,3,4,5-tetrahydro-1,2,4-triazines, and 2-keto derivatives of 1,2-dihydropyrimidines. It was concluded from these reactions that in 1,2,4-triazine derivatives the C-5 carbon is more reactive than the C-3 carbon toward nucleophiles. The reaction mechanism is discussed.