Photoreductive Coupling of Unactivated Ketones and Alkenes via Kinetic Suppression of Ketyl Radical Overreduction.

A direct photoinduced electron transfer strategy that employs phenolate anions as photocatalysts for the efficient generation of ketyl radicals was developed. The photoexcited phenolate catalyst serves as the sole potent reductant in the reaction system, and its inherent transient nature kinetically suppresses overreduction of the transiently formed ketyl radical intermediates. This precise kinetic control preserves the high reactivity of ketyl radicals, enabling their efficient coupling with unactivated aliphatic alkenes and alkynes under strongly reducing conditions.