Sulphur promoted C(sp3)–C(sp2) cross dehydrogenative cyclisation of acetophenone hydrazones with aldehydes: efficient synthesis of 3,4,5-trisubstituted 1H-pyrazoles

Abstract

A novel strategy for the cross dehydrogenative coupling (CDC) of acetophenone hydrazones and aldehydes has been developed for the synthesis of highly substituted pyrazoles. This work, for the first time, uses elemental sulfur as a promoter as well as a hydrogen acceptor in effecting the Csp³–Csp² bond formation via C–H activation.