Regioselective one-pot synthesis of 3,5-diarylpyrazoles

Abstract

The 3,5-diarylpyrazolines and pyrazoles have been easily synthesized in excellent yields by the reaction of 2'-hydroxy­chalcones with hydrazine hydrate. The 2'-hydroxychalcones are converted into flavanones and flavones by simple cyclisation methods and then into pyrazolines and pyrazoles, respectively. Alternatively, one-pot synthesis of pyrazoles has also been achieved by converting 2'-hydroxychalcones into pyrazolines and thereafter their dehydrogenation using I₂-DMSO reagent. The regiochemistry of pyrazoles obtained via pyrazolines and from flavones has been compared.