Phototandem catalysis: efficient synthesis of 3-ester-3-hydroxy-2-oxindoles by a visible light-induced cyclization of diazoamides through an aerobic oxidation sequence.

An unprecedented phototandem catalysis based on a single iridium photocatalyst has been successfully developed. This powerful strategy consists of two mechanistically distinct catalytic cycles, namely, photocatalytic energy transfer (ET) and single electron transfer (SET). The novel protocol allows a rapid and efficient construction of biologically and synthetically important 3-ester-3-hydroxy-2-oxindole derivatives from readily available diazoamides through a cyclization/aerobic oxidation sequence under very mild conditions.