Copper-Catalyzed (5+1) Annulation of Imidazolidines with Cyclopropenes: Synthesis of Functionalized 2-Vinylpiperazines

Herein, we report a copper-catalyzed (5+1) annulation between imidazolidines and cyclopropenes, providing a modular, atom-economical, and efficient strategy for the synthesis of diverse functionalized 2-vinylpiperazines in moderate to good yields. This method features good geometric and regioselectivity for unsymmetrical cyclopropene and imidazolidine substrates, mild reaction conditions, and a broad substrate scope. Notably, this work represents the first (5+1) annulation of cyclopropenes as vinylmetal carbene precursors.