Pd-Catalyzed C-H Carbonylation of (Hetero)arenes with Formates and Intramolecular Dehydrogenative Coupling: A Shortcut to Indolo[3,2-c]coumarins

An efficient protocol for the synthesis of (hetero)aryl carboxylic esters has been achieved by Pd-catalyzed CH carbonylation of (hetero)arenes with aryl formates. A relatively wide range of functional groups can be tolerated in this transformation, and the corresponding esters are obtained in good yields. On this basis, an intramolecular oxidative CH/CH coupling has been developed to prepare indolo[3,2-c]coumarins.