Cu-Catalyzed C–H Phenothiazination toward the Assembly of Cyclopeptides

A modular copper-catalyzed radical macrocyclization for a variety of Tyr-containing compounds bearing phenothiazines has been developed. This approach utilizes cost-efficient Cu­(OAc)2 as a catalyst along with air as the terminal oxidant, thereby enabling the predictable C–N coupling at the ortho C–H bond of phenols in a late-stage fashion. This oxidative and operationally simple coupling technique can proceed intramolecularly to deliver unconventional cyclopeptides featuring a biaryl linkage.