Indium(III) Chloride/2-Iodoxybenzoic Acid: A Novel Reagent System for the Conversion of Indoles into Isatins

Indoles and azaindoles undergo smooth oxidation with 2-iodoxybenzoic acid (IBX) in the presence of indium(III) chloride at 80 °C to afford the corresponding isatins in excellent yields. This method is very useful for the direct preparation of isatins from indoles. The reaction proceeds smoothly in aqueous media and the products are obtained in excellent yields.