Visible light-induced FeCl3-catalyzed chlorination of C–H bonds with MgCl2

Abstract

Chlorination has become a commonly used strategy in various chemical industries. Environmentally friendly chlorination of C–H bonds to directly generate C–Cl bonds is also in high demand in organic synthesis. Herein, we report a new and green highly selective method of chlorination of C(sp³)–H moieties with the inorganic salt MgCl₂, cocatalyzed by visible light/FeCl₃ under strong oxidant-free and ambient conditions. The reaction was applied to the chlorination of different methylarene α-hydrogen and cyclic hydrocarbon C–H moieties with high conversion and kinetic selectivity. The chlorination of toluene α-Hs proceeded in 91% yield, with 98% selectivity and 95% conversion. Electron–spin resonance studies of the DMPO-Cl (5,5-dimethyl-1-pyrroline-N-oxide) radical revealed that the reaction mechanism involved a free radical process.