Process for preparation of 2-oxocarboxylic acid esters

A process for the preparation of 2-oxocarboxylic acid esters represented by the following general formula (I), comprising by oxidizing a 2-hydroxycarboxylic acid ester represented by the following general formula (II) in the presence of a nitroxyl radical represented by the following general formula (III), a hypochlorite, a metal bromide and water with the pH of the reaction system being kept within the range of 5 to 7: (I) (II) (III) wherein R1 and R2 are each independently an alkyl group, an alkenyl group, an alkynyl group, an aryl group or an aralkyl group, which each may be substituted with substituents; and R3 is a hydrogen atom, an alkoxyl group, an aralkyloxy group, an acyloxy group or a hydroxyl group.