Transition Metal‐free C−H Sulfonylation and Pyrazole Annulation Cascade for the Synthesis of 4‐Sulfonyl Pyrazoles

Abstract A practical protocol for the synthesis of 4‐sulfonyl pyrazoles via the reactions of readily available N,N ‐dimethyl enaminones and sulfonyl hydrazines has been developed via the catalysis of molecular iodine in the presence of TBHP and NaHCO 3 at room temperature. The pyrazole products have been constructed via the tandem C(sp 2 )−H sulfonylation and a pyrazole annulation without employing any transition metal catalyst or reagent, thus providing a practical new method for the synthesis of the novel pyrazoles bearing a sulfonyl side chain in the heterocycle.