Visible-light-driven site-selective alkylation of the benzo core of coumarins

An unprecedented, straightforward photochemical platform for efficient site-selective C-H alkylation of the C7 position of the benzocore via the cross coupling between coumarins and NHPI esters, employing Ru(ii) as a photocatalyst in visible light, has been reported. Remarkably, this transformation demonstrated broad substrate scope and good functional group compatibility. Controlled experiments and DFT calculations shed some insight into the mechanistic details of the reaction and allowed us to propose a plausible mechanism for the regioselectivity.