Convenient and Clean Synthesis of Isatins by Metal-Free Oxidation of Oxindoles

A metal-free synthesis of isatins was achieved through the oxidative reactions of oxindoles with molecular oxygen in the presence of tert-butyl nitrite as an additive. This strategy provides a convenient and simple synthetic route to the construction of C=O bonds without the need for any catalyst or base. The attractive features of this reaction include its convenient procedure and mild reaction conditions.