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 C-H 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 C-H/C-H coupling has been developed to prepare indolo[3,2-c]coumarins.