I2/TBHP/cyclohexanone a novel catalyst system for the oxidative dearomatization of indoles to indolin-3-ones at room temperature under solvent-free condition

Abstract

Here we report a novel metal-free catalyst system for the oxidative dearomatization of indoles to indolin-3-ones. I2, TBHP and cyclohexanone together forms the catalyst system. Indole undergoes oxidative trimerization, whereas 2-substituted indole gives oxidative dimerized product. No solvent is required for the reaction and is carried out at room temperature. Electron-deficient indoles give lower or no yields, while electron-rich indoles produce excellent yields. The mechanism of the reaction is studied.