Electrochemical Rhodium-Catalyzed Enantioselective C-H Annulation with Alkynes

Abstract

The synergistic use of transition metal catalysis and electrochemistry is an attractive strategy for oxidative site-selective C-H functionalization since the use of stoichiometric chemical oxidants can be avoided and novel reactivity can be achieved. However, metalcatalyzed electrochemical C-H functionalization is mainly limited to arene C(sp2)-Hfunctionalization, and enantioselective C-H functionalization is uncommon and remains challenging. Herein,we report an electrochemically tuned rhodium-catalyzed enantioselective C-H annulation with alkynes, affording various spiropyrazolones in good yields and enantioselectivity in an undivided cell at room temperature. Notably, unsymmetrical alkylarylacetylenes are also efficiently converted to their corresponding spiroannulation products with excellent regioselectivity and good enantioselectivity. Thus, the protocol provides a practical and environmentally benign tool for forging chiralspiropyrazolones,whichareimportant structural motifs found in pharmaceuticals and biologically active molecules.