A Pyridine-Based Donor–Acceptor Molecule: A Highly Reactive Organophotocatalyst That Enables the Reductive Cleavage of C–Br Bonds through Halogen Bonding

We report a pyridine-based donor–acceptor molecule that exhibits high reactivity as a visible-light photoredox catalyst. This photoredox catalyst enables the formation of radicals from alkyl bromides, which are useful radical precursors that unfortunately do not perform well under reductive conditions, by a direct, photocatalytic reductive cleavage of the C–Br bond. A wide variety of alkyl bromides including unactivated ones can be used under ambient conditions without any additional activating agents to give the C–C coupling products in good yield. Mechanistic studies indicated that the photocatalyst interacts with alkyl bromides through halogen bonding and that the pyridine moiety is important for the progress of the reaction.