Cyclization and oxidation of o-bromophenylacetamides for the synthesis of oxindoles and isoindigoes

N-substituted oxindoles were obtained through a facile KOH/DMSO promoted intramolecular cyclization of o-bromophenylacetamides in good yields. Furthermore, isoindigo derivatives were readily synthesized through sequential intramolecular cyclization, oxidation and condensation of o-bromophenylacetamide in the presence of copper (II) acetate monohydrate, iodobenzene diacetate and KOH/DMSO. This method provides a convenient synthesis of a range of oxindoles and symmetrical biologically important (E)-bisindole-2-ones using o-bromophenylacetamide as sole starting material. The reaction mechanism is elucidated in light of the control experiment results.