Palladium-catalyzed cascade reactions of 3-iodochromones with aryl iodides and norbornadiene leading to annulated xanthones

Abstract

An efficient, palladium-catalyzed cascade reaction, which leads to formation of annulated xanthones, was devised. The process, which uses readily available 3-iodochromones, aryl iodides and norbornadiene as starting materials, takes place via a tandem Heck reaction/double C–H activation/retro-Diels–Alder pathway. The high chemoselectivity of the process is mechanistically unique and it serves as a new approach to achieve regioselective control of C–H activation in Pd/norbornene or norbornadiene systems. Its broad substrate scope, including heteroaryl coupling partners, enables access to diverse annulated xanthones.