Photoredox-Catalyzed Redox-Neutral Decarboxylative C-H Acylations of Coumarins with α-Keto Acid.

A novel and green photocatalytic strategy for the synthesis of C-4-acylated coumarins with α-keto acids and 3-nitrocoumarin has been developed. This operationally simple protocol works under mild reaction conditions, providing convenient access to 4-acyl coumarin derivatives. The control experimental results showed that the nitro radical produced by the cleavage of the C-N bond acts as an electron acceptor to complete the photocatalytic cycle, achieving a redox-neutral reaction.