Cross-Coupling of Benzylic and Aldehydic C-H Bonds via Photocatalytic Tandem Radical-Radical Coupling and Acceptorless Alcohol Dehydrogenation.

The construction of a C-C bond by cross-coupling of two different C-H bonds with the release of hydrogen gas represents an ideal yet challenging bond formation strategy. Herein, we report a photocatalytic metal-free cross-coupling of benzylic and aldehydic C-H bonds by synergistic catalysis of organophotocatalyst 4CzIPN and a thiol, which affords the corresponding α-aryl ketones in acceptable yields along with hydrogen evolution. The mechanistic investigation indicates a radical-radical coupling to give an intermediary alcohol, followed by an acceptorless alcohol dehydrogenation.