Visible-Light S_NAr Pyridination of ArylHalides and Triflates with Acridine-Lewis Acid Photocatalysts

This report describes the development of a visible light (440 nm) photocatalytic method for the cation radical-accelerated (CRA) S_NAr pyridination of aryl (pseudo)­halides using modular acridine-Lewis acid photocatalysts. A first-generation catalyst composed of acridine and Sc­(OTf)₃ is effective for the reaction of electronically diverse pyridines with electron-rich (primarily alkoxy- and alkyl-substituted) aryl chlorides and triflates. With select substrate pairs, an alternative electron donor–acceptor pathway can also be operative. Modifying the acridine backbone of the <i>in situ</i> photocatalyst broadens the scope of aryl chloride coupling partners, enabling visible light CRA-S_NAr with unactivated chlorobenzene derivatives as the limiting reagent.