Copper-Catalyzed Three-Component Synthesis of 3-Aminopyrazoles and 4-Iminopyrimidines via β-Alkynyl-N-sulfonyl Ketenimine Intermediates

3-Aminopyrazoles and 4-iminopyrimidines were efficiently prepared via copper-catalyzed three-component reactions of butadiynes, sulfonylazides, and hydrazides or imidamides. The reactions were regioselectively approached via the formation of a β-alkynyl-N-sulfonyl ketenimine intermediate which represented a new and effective 1,3-dielectrophilic equivalent in organic synthesis.