Use of Pyridinium Chlorochromateand Reusable Polyaniline Salt Catalyst Combination for the Oxidationof Indoles

Abstract

A novel method is described herein for the simple, convenient and efficient oxidation of indoles to isatins using pyridinium chlorochromate with the aid of polyaniline salt catalyst at room temperature or at reflux in dichloroethane. Interestingly, oxidation of 3-alkyl indoles by this procedure gave 3-hydroxy 3-alkyl oxindoles. On the other hand, indol-3-alkanols gave mixtures of isatins and 3-formyl indoles. This is the first example of use of polyaniline as a catalyst in oxidation reaction.