Synthesis and Some Reactions of 4-Benzoyl-5-Phenyl- 1-Pyridin-2-yl-1H-Pyrazole-3-Carboxylic Acid

The synthesis of novel pyrazole derivatives and investigations of their chemical and biological behavior have gained more importance in recent decades for biological, medicinal, and agricultural reasons. Concerning the attempt to synthesize some novel pyrazole and fused pyrazole derivatives from 4-benzoyl5-phenyl-2,3-furandione 1 and various hydrazines or hydrazones, the synthesis of 4-benzoyl-1,5-substituted1H-pyrazole-3-carboxylic acids and some of their derivatives has been reported recently. It is well known from a previous study that reactions of furandione 1 with hydrazines led to the formation of pyrazolecarboxylic acid and pyridazinone derivatives simultaneously. However, in that study, the reactions of 4-benzoyl-1,5-substituted-1H-pyrazole-3-carboxylic acids with 2-hydrazinopyridine, instead of phenyl hydrazine or hydrazine hydrate, to prepare new pyrazolo-pyridazine derivatives, did not produce the corresponding pyrazolo-pyridazine systems. The failure or the difficulty in forming the pyridazine nucleus from 2-hydrazinopyridine was explained by the low nucleophilicity of the nitrogen atom adjacent to the pyridine ring. In the present work, keeping the above reports in mind, we investigated the chemical behavior of furandione 1 against 2-hydrazinopyridine nucleophile.