Catalyst-Free C-H Methylation of Heteroarenes Enabled by Electron Donor-Acceptor Complex Photoactivation

An efficient, additive- and catalyst -free, visible-light-driven radical C-H methylation of heteroarenes (including quinoxalinones, pyra-zinones, quinolinones and coumarins) utilizing readily available methylamines as the methyl source has been developed. The trans-formation possesses the advantages of operational simplicity, mild reaction conditions and broad substrate scope. Mechanistic studies disclosed that a photoactive electron donor-acceptor (EDA) complex between methylamines and heteroarenes is crucial to this trans-formation.