Synthesis of Highly Fused Pyrano[2,3-b]pyridines via Rh(III)-Catalyzed C-H Activation and Intramolecular Cascade Annulation under Room Temperature.

A facile access to the polycyclic-fused pyrano[2,3-b]pyridines has been established under room temperature via Rh(III)-catalyzed C-H bond activation and intramolecular cascade annulation. This strategy features high efficiency, unique versatility, and generality and it can occur under mild conditions in good to excellent yields. More importantly, this strategy can be extended to the late-stage functionalization of drugs possessing the CN group.