1-Phenylpyridazino[4,5-d]pyridazine

Abstract

Treatment of pyridazine-4,5-dicarboxylic anhydride (5) with benzene and aluminium chloride gave 4-benzoylpyridazine-5-carboxylic acid (7) which was converted into its methyl ester (8) by methylation with diazomethane. When the latter was allowed to react with sodium bis-(2-methoxyethoxy)aluminium hydride and hydrazine, the phenyl derivative (3) was not obtained but a hydrazone (10) and a methyl ester (11), whose structures were deducted from spectroscopic data, were isolated. 1-Hydroxy-4-phenylpyridazino[4,5-d]pyridazine (12), prepared both from (7) and (8), afforded a chloro-derivative (13) and a thione (17) by reaction with POCl₃ and P₂S₅, respectively. Compound (17) reacted smoothly with hydrazine to yield a hydrazine-derivative (18) which was easily transformed into 1-phenylpyridazino[4,5-d]pyridazine (3) by treatment with yellow mercuric oxide.