Transition-metal-free electrochemical-induced active C(sp³)-H functionalization

Direct C–H bond functionalization is the most effective technique to construct C–X (X = C, N, O, S, etc.), which could simplify the conventional synthesis methods. Transition-metal-catalyzed C–H bond functionalization needs metal catalysts such as palladium, rhodium, iridium, cobalt, copper, etc., which is not conducive to its sustainable development. In recent years, C(sp³)-H bond functionalization without transition metal catalyst has been studied increasingly. In the meantime, electrochemistry has become one of the most dynamic research fields in organic synthesis for the reason that it can substitute the traditional expensive and polluting metal salt oxidants (e.g. Cu²⁺, Ag⁺ salt) with current/electrons to act as a redox agent. So the applications of electrochemistry combined with transition-metal-free C(sp³)-H bond functionalization to solve some long-standing challenges have gradually gotten more and more attention in recent years. In this review, the researches on transition-metal-free electrochemical-induced C(sp³)-H bond functionalization from 2016 to now will be systematically presented and the future research hotspots and difficulties in this field will also be prospected.