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.