Mn-Mediated Direct Regioselective C-H Trifluoromethylation of Imidazopyridines and Quinoxalines

A simple and highly efficient strategy has been developedfor directC-H trifluoromethylation at C-3 of imidazopyridines and C-8of quinoxalines with readily available Langlois reagent through KMnO4/AcOH system. This protocol showed broad substrate scope andafforded moderate-to-excellent yields of both products. It is thefirst report that the functionalization of quinoxalines occurred regioselectivelyat the C-8 position of quinoxalines. Mechanistic studies revealedthat reaction proceeded via radical pathway.

Automated summary

A simple and highly efficient strategy has been developed for direct C-H trifluoromethylation at C-3 of imidazopyridines and C-8 of quinoxalines using the readily available Langlois reagent through the KMnO4/AcOH system. This protocol exhibited a wide range of substrate compatibility and provided moderate-to-excellent yields of both products. It represents the first report of regioselective functionalization of quinoxalines at the C-8 position and mechanistic studies demonstrated a radical pathway.