Electroredox N-Heterocyclic Carbene-Catalyzed Enantioselective (3 + 3) Annulation of Enals with 2-Naphthols

Developing asymmetric transformations using electroredox and N-heterocyclic carbene (NHC)-catalyzed radical pathways is still desirable and challenging. Herein, we report an iodide-promoted β-carbon activation (LUMO-lowering process) of enals via electroredox carbene catalysis coupled with a hydrogen evolution reaction (HER). This strategy offers an environmentally friendly and sustainable route for rapidly assembling synthetically useful chiral naphthopyran-3-one in good to excellent yield and enantioselectivity using traceless electrons as inexpensive and greener oxidants. The mechanistic studies and cyclic voltammetry suggest that the reaction proceeds via direct single electron transfer (SET) of the in situ-generated Breslow intermediate.