Intramolecular cross dehydrogenative coupling of 4-substituted coumarins: rapid and efficient access to coumestans and indole[3,2-c]coumarins

A palladium-catalyzed highly efficient and atom-economical intramolecular cross dehydrogenative coupling (CDC) reaction to access fused polyheterocycles containing a coumarin nucleus has been developed. A wide range of coumestans and indole[3,2-c]coumarins can be afforded in good to excellent yields (up to 99%). By taking advantage of this methodology, some biologically active molecules such as coumestrol and flemichapparin C can be facilely constructed in great yields.