Copper-Catalyzed Ficini [2 + 2] Cycloaddition of Ynamides

The Ficini [2 + 2] cycloaddition using N-sulfonyl-substituted ynamides is described, featuring the utility of CuCl₂ and AgSbF₆ as catalysts. This work represents the first successful example of ynamides participating in a thermal [2 + 2] cycloaddition with enones.