Access to Indole-Fused Polyheterocycles via Pd-Catalyzed Base-Free Intramolecular Cross Dehydrogenative Coupling

A base-free process to access indole-fused polyheterocycles via a highly efficient and atom-economic palladium-catalyzed intramolecular cross dehydrogenetive coupling (CDC) reaction of 4-aniline substituted coumarins, quinolinones, and pyrones has been developed. A wide range of indolo[3,2-c]coumarins, indolo[3,2-c]quinolinones, and indolo[3,2-c]pyrones can be facilely afforded in good to excellent yields (up to 99%).