Visible-Light Mediated Photooxidative Synthesis of α-Keto Amides

Photocatalytic amidation of alpha-keto aldehydes is herein investigated. This transformation was achieved using rose bengal as photocatalyst at room temperature under ambient air and under irradiation of a 20W white LED bulb. The method is mild, efficient and environmentally benign. This photocatalytic method is compatible with different unsubstituted and substituted alpha-keto aldehydes having electron-withdrawing or -donating groups, secondary amines, cyclic or acyclic, and primary aliphatic amines. Mechanistic studies reveal that the reaction proceeds via oxidative quenching of the photocatalyst.