Aryl Ketone-Catalyzed Light-Driven Radical Oxy-Functionalization of Non-Acidic C(sp³)-H Bonds Enabled by Triple Role of TEMPO

A light-driven radical oxy-functionalization of non-acidic aliphatic and benzylic C(sp(3))-H bonds was achieved with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) in a single-step by employing an aryl ketone as a sole catalyst. The transformation was initiated by homolysis of a C(sp(3))-H bond in the starting substance by the photo-excited aryl ketone. The derived carbon radical was then promptly trapped by TEMPO leading to the formation of the TEMPO-adduct. The derived TEMPO-adduct is synthetically versatile as an alcohol equivalent since it can be readily converted to the corresponding ketone by oxidation and to the corresponding alcohol by reduction. The key to realizing the present catalytic reaction relies on the distinctive triple role of TEMPO, which acts as the precursor of the oxygen functionality, the oxidant to regenerate the aryl ketone, and the protective group for the derived TEMPO-adduct from over-oxidation.