Copper-Catalyzed Three-Component Synthesis of 3‑Aminopyrazoles and 4‑Iminopyrimidines via β‑Alkynyl‑<i>N</i>‑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-<i>N</i>-sulfonyl ketenimine intermediate which represented a new and effective 1,3-dielectrophilic equivalent in organic synthesis