Electrochemical oxidative C(sp³)-H cross-coupling with hydrogen evolution

Oxidative C(sp(3))-H bond functionalization is a powerful tool in organic synthesis, but the stoichiometric oxidants required for bond formation raise environmental concerns. Electrochemical synthesis is typically carried out under environmentally benign conditions and hence is increasingly used in organic reactions. Recent advances revealed that electrochemical oxidative cross-coupling reactions employing either free radicals or carbocations can be conducted in the absence of external oxidants. In this Review, we outline the electrochemical oxidative C(sp(3))-H cross-coupling to C(sp(3))-C(X) (X = N, O, S, P, F, I and Br) bonds with hydrogen evolution under external oxidant-free conditions. Two commonly used electrochemical methods, namely direct and indirect oxidation electrolysis, are discussed for C(sp(3))-H activation. The outline of electrochemical oxidative C(sp(3))-H cross-coupling is organized based on the reactive intermediates (C(sp(3))-M, a C(sp(3)) radical or a C(sp(3)) cation). Electrochemical asymmetric C(sp(3))-H cross-coupling and late-stage functionalization of C(sp(3))-H bonds in complex molecules are included to demonstrate the utility. Future perspectives for the development of electrochemical C(sp(3))-H bond functionalization are proposed.