Electrochemical-/Photoredox Aspects of Transition Metal-Catalyzed Directed C-H Bond Activation

C-H activation and functionalization have caused a paradigm shift in molecular design as a result of its selective and atom-economical nature. Despite significant major advances, C-H functionalization regime had the disadvantage of employing (super) stoichiometric amounts of expensive and toxic metal oxidants for oxidative functionalization. Hence, various protocols were introduced to improve the sustainability of C-H bond functionalization, such as employing molecular oxygen, metal oxidants or tethered oxidants that get cleaved during the reaction, in addition to the use of suitable solvents or additives. The most recent and proficient advance is the use of electro- or photo-redox catalysis. In this Review, we highlight the recent advances towards a green catalytic approach for oxidative C-H bond functionalization using light and photosensitizers or electricity as sources of oxidant to regenerate the active species.