Carbene-Catalyzed Alkylation of Carboxylic Esters via Direct Photoexcitation of Acyl Azolium Intermediates

A carbene-catalyzed reductive coupling reaction of carboxylic esters and substituted Hantzsch is disclosed. Key steps this include one-electron reduction a carbene catalyst-bound acyl azolium intermediate to generate the corresponding radical for subsequent alkylation reactions. The promoted by irradiation with visible light without involvement transition-metal photocatalysts. Mechanistic studies suggest that direct photoexcitation in situ formed likely responsible light-induced one-electron-reduction process. Photoexcitation converts single-electron oxidant, enabling oxidation intermediates. Our reactions work well broad range aryl ester substrates. Sophisticated structures, including those present medicines, can be incorporated into ketone molecules using our approach via very mild conditions tolerate various functional groups.