Studies on the Syntheses of N-Heterocyclic Compounds. VIII. Hydrolysis of 2-Phenylpyrimido[4, 5-d]pyridazine Derivatives

Abstract

Hydrolysis of 2-phenyl-5, 8-dichloropyrimido[4, 5-d]pyridazine (1) and its mono- or di-substituted derivatives was carried out. Among the hydrolyzed products, 2-phenyl-5-substituted-7, 8-dihydropyrimido[4, 5-d]pyridazine-8-one (7) was found to be unstable, undergoing further cleavage of the pyrimidine ring to afford pyridazine derivatives (16, 17).