Metal-free visible-light-induced aerobic oxidation of α-diazoesters leading to α-ketoesters in air

A metal-free and visible-light-promoted strategy has been achieved for the construction of α-ketoesters via aerobic oxidation of α-diazoesters with dioxygen in air at room temperature. Using cheap, readily available Eosin Y as the photocatalyst and O2(air) as the green oxidant, the present protocol offers a mild and efficient approach to a wide range of α-ketoesters in moderate to good yields. Preliminary mechanistic studies suggested that photo-excited singlet oxygen was involved in the present reaction system.