Copper-catalyzed tandem cyclization/arylation of α,β-alkynic hydrazones with diaryliodonium salts: synthesis of N -arylpyrazoles.

A copper-catalyzed efficient method for the synthesis of a diverse variety of substituted N -aryl pyrazoles from readily available α,β-alkynic N -tosyl hydrazones and diaryliodonium triflates is realized. This one-pot multi-step methodology features a broad scope with good yields, scalability, and appreciable functional group tolerance. Detailed control experiments reveal that the reaction proceeds through tandem cyclization/deprotection/arylation events where the copper catalyst plays a distinct role.