Visible-Light SNAr Pyridination of Aryl Halides and Triflates with Acridine-Lewis Acid Photocatalysts.

Abstract

This report describes the development of a visible light (440 nm) photocatalytic method for the cation radical-accelerated (CRA) SNAr 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 in situ photocatalyst broadens the scope of aryl chloride coupling partners, enabling visible light CRA-SNAr with unactivated chlorobenzene derivatives as the limiting reagent.