Copper-catalyzed Pummerer type reaction of α-thio aryl/heteroarylacetates: Synthesis of aryl/heteroaryl α-keto esters

•Pummerer type reaction for the synthesis of the α-keto ester is described.•The reaction proceeds through the generation of a thionium ion in situ.•The source of oxygen in α-keto ester is confirmed by isotopic-labelling experiment.