Biomimetic Iron-Catalyzed Oxidation of 3-Substituted Indoles to 2-Oxindoles.

A biomimetic iron-catalyzed system has been developed for the selective oxidation of 3-substituted indoles to 3-monosubstituted 2-oxindoles using H2O2 as a green oxidant under mild conditions. This catalytic approach addresses the drawbacks of stoichiometric biomimetic models and exhibits broad substrate scope and excellent functional group tolerance. Mechanistic studies suggest the reaction proceeds via an epoxide intermediate followed by a 2,3-hydride shift, with the epoxidation step being rate-determining. The method provides a sustainable route to biologically relevant 2-oxindole scaffolds.