Exo-Selective and Enantioselective Photoenolization/Diels–Alder Reaction

An unusual exo-selective photoenolization/Diels–Alder reaction of electron-rich 2-methylbenzaldehydes and dienophiles containing a benzoyl group at its α position was reported herein. The chiral TADDOL-type ligand plays a key role in this process: (1) accelerating the reaction; (2) controlling the enantioselectivity; and (3) improving and tuning the diastereoselectivity of the reaction.