Cobalt-Catalyzed Azidation of Benzylic C–H Bonds

Abstract Direct methods for selective functionalization of C(sp3)–H bonds could greatly streamline the synthesis of complex molecules. However, such transformations remain challenging. Herein, we report a cobalt-catalyzed azidation of benzylic C–H bonds that enables efficient access to benzylic azides. The reaction employs the C–H substrate as the limiting reagent and features broad substrate scope, as well as good functional-group tolerance. The key to success lies in the utilization of a commercially available N,N-ligand and cobalt catalyst. Preliminary mechanistic study indicates that hydrogen-atom transfer (HAT) of benzylic C–H bonds affords a benzyl radical that is involved in the reaction process.