Synthesis of Pyrazole Derivatives Using 1-Benzoyl-1-phenylhydrazine

Abstract Condensation of 1-benzoyl-1-phenylhydrazine (I) with β-ketoesters and β-diketones was investigated. Reaction of I with ethyl acetoacetate, ethyl benzoylacetate and diethyl acetonedicarboxylate in the presence of phosphorus pentoxide afforded the corresponding hydrazones which were easily cyclized by sodium hydroxide to give pyrazole derivatives. Reaction of I with acetylacetone proceeded to give hydrazone without condensing agent. 4-Carboxy-1,5-diphenylpyrazol-3-ylacetic acid and its mono- and diester were also prepared.