Photoinduced Nickel-Catalyzed Selective N -Demethylation of Trialkylamines Using C(sp 2 )-Bromides as HAT Reagents.

N -Demethylation of trialkylamines is a useful transformation, but typically requires harsh reaction conditions and stepwise procedures, as well as judicious protection of labile functional groups. Herein we report a mild, catalytic approach for the demethylation of trialkylamines by utilizing photoinduced nickel catalysis wherein C(sp 2 )-bromides serve as hydrogen-atom transfer (HAT) reagents. This method achieves direct demethylation of trialkylamines with wide functional group compatibility, making it highly suitable for late-stage derivatization of complex molecules. Mechanistic investigations provide evidence that C(sp 2 ) radicals generated via photoinduced Ni-C(sp 2 ) bond homolysis are involved in hydrogen atom abstraction from trialkylamines. Utilizing steric control of the C(sp 2 )-bromides, our HAT approach achieves demethylation with excellent site selectivity in the presence of benzyl-substituted amines, which is complementary to the selectivity of classical approaches that afford debenzylation product instead.