Using a nitrogen-centered radical as a selective mediator in electrochemical C(sp3)-H amination

Nitrogen-centered radicals are versatile intermediates, and they have been widely explored in organic synthesis. However, the catalytic role of these species has received far less attention due to a dearth of mild access to them. Herein, we discovered an array of nitrogen-centered radicals that were readily generated from benzimidazoles under direct electrolysis. These active species were unambiguously identified with tools of electron paramagnetic resonance (EPR), UV-visible (UV-vis) spectroscopy, and high-resolution mass spectrometry (HRMS). More importantly, we employed these in-situ-generated radicals in the electrochemical C(sp3)–H aminations as selective hydrogen atom transfer (HAT) mediators. With the mediation of nitrogen-centered radicals, unconventional site selectivity and reactivity were achieved that would otherwise be inaccessible for existing approaches. The catalytic mode enabled by the radicals was also extended to the amination of allylic C(sp3)–H and β-C(sp3)–H of alcohols, anodic oxidation of Si–H, and Minisci-type reactions. [Display omitted] •Nitrogen-centered radicals used as hydrogen atom transfer mediators•A general solution for electrochemical amination of benzylic C(sp3)–H•Excellent tolerance for strongly electron-deficient substrates•Unconventional site selectivity compared with existing approaches Radical species as highly reactive intermediates have been extensively explored in organic synthesis, whereas the catalytic role of radicals receives far less attention due to their inconvenient access. Here, we used an electrochemical approach to rapidly generate nitrogen-centered radicals from benzimidazoles and investigated their catalytic properties in the electrochemical C(sp3)–H amination. Remarkably, the nitrogen-centered radical exhibited unconventional site selectivity and reactivity, thus providing a supplementary route to the challenging transformation. We believe that the catalytic mode relying on nitrogen-centered radicals will provide a general tool for a broad range of radical transformations. With further structure optimization and modification, highly efficient and stereoselective radical catalysts would be accessible in the near future. Nitrogen-centered radicals were used as selective mediators in electrochemical amination! Structurally well-defined nitrogen-centered radicals were readily accessed via direct electrolysis of benzimidazoles. More importantly, a promising and general catalytic activity of the radicals