Cobalt-Catalyzed Azidation of Benzylic C-H Bonds.

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.