Palladium‐Catalyzed Photoinduced Regioselective C8 Arylation of 1‐(Pyridin‐2‐yl)quinolin‐4(1 <i>H</i> )‐Ones with Aryl Diazonium Salts

A visible‐light‐mediated regioselective C8 arylation of quinolinones has been developed by merging transition‐metal catalysis with photoredox catalysis. This approach offers broad substrate scope and mild reaction conditions, affording the desired products in up to 85% yield. Furthermore, to investigate the reaction mechanism, several control experiments were performed, including fluorescence quenching studies, quantum yield measurements, light‐on/off experiments, kinetic isotope effect (KIE) analysis, and H/D labeling experiments. This strategy exhibits excellent scalability and also enables subsequent C2 alkenylation.