Electro-oxidative amination of benzylic C(sp³)–C(sp³) bonds in aromatic hydrocarbons

Abstract

C(sp³)-C(sp³) amination represents a promising approach for synthesizing various amines, facilitating applications from late-stage scaffold hopping to the degradation of polymers and biomass. However, it remains challenging due to the inertness of the C-C bond and difficulties in controlling regio- and chemo-selectivity. Herein, we report an electro-oxidative benzylic C(sp³)-C(sp³) amination reaction of aromatic hydrocarbons using nitriles, amides, and sulfonamides as nucleophiles. This process occurs under mild conditions with hydrogen evolution, eliminating the need for external oxidants or transition metal catalysts. Mechanism involves successive anodic oxidative cleavage of the benzylic C(sp³)-C(sp³) bond to generate two carbocation fragments, which are subsequently captured by nucleophiles to form two C-N bonds. Mechanistic studies suggest that HFIP is critical as additive in adjusting the oxidation potentials of alkylbenzene substrates and amine products, effectively preventing overoxidation of products.