Interception of Radicals by Molecular Oxygen and Diazo Compounds: Direct Synthesis of Oxalate Esters Using Visible-Light Catalysis.

The synthesis of oxalate esters through a radical process, rather than the traditional ionic reaction, has been well developed in which the radicals induced by visible light are trapped by molecular oxygen and diazo compounds under room temperature. This reaction is operationally simple, mild, and shows broad substrate scopes in α-bromo ketones and diazo compounds.