4-Dimethylaminopyridine-Catalyzed Metal-Free Aerobic Oxidation of Aryl α-Halo Esters to Aryl α-Keto Esters

[Image: see text] A novel, metal-free aerobic oxidation method is described. 4-Dimethylaminopyridine (DMAP) successfully catalyzed the oxidation of aryl α-halo esters to corresponding aryl α-keto esters (up to 95% yield) under mild reaction conditions (Li(2)CO(3), dimethylacetamide, air, and room temperature). A mechanism has been proposed where the oxidation proceeds through a [3 + 2] cycloaddition between O(2) in an air atmosphere and pyridinium ylides. The ylides are supposedly generated from aryl α-halo esters and DMAP in the presence of carbonates. Based on the plausible mechanism, the potential of DMAP as a catalyst in oxidation reactions was extended.