Photoinduced Site-Selective C-H Functionalization by Pyridine N-oxide Based HAT Catalysts

Readily available and facilely tunable pyridine N-oxides have been developed as effective photoinduced hydrogen-atom-transfer (HAT) catalyst for site-selective C-H functionalizations of a broad range of C-H substrates, including unactivated al-kanes. Pyridine N-oxide radicals, catalytically generated from N-oxides by photoredox catalyzed single-electron oxidation, are the key intermediate that enable effective HAT process for carbon radical generation to achieve alkylation, amination, azidation, and allylation. Additionally, the fine tuning of reactivity and selectivity of pyridine N-oxides through operationally simple structural modification was investigated and shown promising capability for selective functionalization of unactivat-ed secondary and primary C(sp3)–H bonds.