Photocatalytic C-H Amination of Arenes with Saccharin.

Abstract

We report an unprecedented, highly general organic photocatalytic strategy for direct C(sp2)-H amination of arenes using easily accessible saccharin as a nitrogen source. In sharp contrast to conventional radical amination protocols requiring transient arene radical cation intermediates, our system operates via an initial preferential single-electron transfer (SET) oxidation of the in situ-generated saccharinate anion. This mechanistic pivot successfully bypasses longstanding electronic limitations, enabling an exceptionally broad substrate scope. The protocol tolerates a full spectrum of aromatic systems, including unactivated benzene (using only 2.0 equiv), haloarenes, polycyclic networks, highly electron-deficient arenes bearing strong electron-withdrawing groups (ester, nitrile, or trifluoromethyl substituents), and complex pharmaceutical frameworks, delivering the corresponding N-aryl saccharins in up to 99% yield (98% for benzene) with predictable regioselectivity. Density functional theory (DFT) calculations quantitatively corroborate the electrophilic radical kinetics (ΔG‡ = 2.3-14.4 kcal/mol for arene addition) and TEMPO-mediated rearomatization cascade. Furthermore, the N-aryl saccharin adducts function as robust, programmable modified Gabriel reagents, smoothly delivering diverse primary and secondary aryl amine hydrochloride salts in up to 99% yield under remarkably mild conditions.