Metal- and oxidant-free carbonylation of benzylic and allylic C–H bonds with H2O via dual oxidative radical-polar crossover†

The selective and controllable functionalization of unreactive C(sp³)–H bonds under mild conditions is a highly desirable yet challenging goal in both organic synthesis and pharmaceutical industry. Herein, we report an unprecedented visible-light mediated metal- and oxidant-free carbonylation of both benzylic and allylic C–H bonds with H₂O. The synergistic combination of an organophotocatalyst 4CzIPN and a thiol enables the transformation of diverse arrays of benzylic and allylic C–H bonds into carbonyls in moderate to excellent yields with good functional group compatibility. Moreover, the oxidation of amines to aldehydes has also been realized by this protocol. Mechanistically, an oxidative radical-polar crossover (ORPC) process affords an alcohol intermediate, which then undergoes another ORPC process to furnish the carbonyl product.