Construction of Protoberberine Alkaloid Core through Palladium Carbene Bridging C–H Bond Functionalization and Pyridine Dearomatization

Compounds with a pyridoisoquinolinone core often appear as members of the protoberberine alkaloid family. Traditional methods to construct this framework normally rely on manipulation of sophisticated reactants. Herein, a palladium-catalyzed reaction of readily available pyridotriazoles and o-bromo/pseudohalo benzaldehydes is described, which provides a modular approach to pyridoisoquinolinone derivatives. This methodology provides a concise synthetic route to prepare protoberberine-type alkaloids. The role of pyridotriazole is 2-fold, acting as a relay reagent to promote C–H bond functionalization and undergoing pyridine dearomatization to construct the polycyclic system.