Palladium-catalyzed carbonylative coupling of α-chloroketones with hydrazines: a simple route to pyrazolone derivatives

A range of pyrazol-5-one and pyrazol-3-one derivatives has been synthesized in a single step via a palladium- catalyzed carbonylation of aromatic or aliphatic a-chloroketones, in the presence of aromatic or aliphatic hydrazines. A reaction mechanism, explaining the observed regioselectivity, has been also discussed