Aqueous and Visible-Light-Promoted C-H (Hetero)arylation of Uracil Derivatives with Diazoniums.

Direct C5 (hetero)arylation of uracil and uridine substrates with (hetero)aryl diazonium salts under photoredox catalysis with blue light was reported. The coupling proceeds efficiently with diazonium salts and heterocycles in good functional group tolerance at room temperature in aqueous solution without transition-metal components. A plausible radical mechanism has been proposed.