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.