Dual roles of sulfonyl hydrazides: a three-component reaction to construct fully substituted pyrazoles using TBAI/TBHP.

A mild and rapid approach has been developed for the construction of fully substituted pyrazoles using TBAI as a catalyst and TBHP as an oxidant, in which tosylhydrazide functions as the ring component and sulfonyl precursor. This protocol features a wide substrate scope with a broad range of functional group tolerance, utilizes easily available starting materials, can be scaled-up, and is operationally simple.