Oxidative Cleavage of Indoles Mediated by Urea Hydrogen Peroxide or H ₂ O ₂ in Polar Solvents

The oxidative cleavage of indoles (Witkop oxidation) involving the use H2O2 or urea hydrogen peroxide in combination with a polar solvent has been described. Among these solvents, 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) stands out as one affording corresponding 2-ketoacetanilides generally higher yields protocol described also enabled oxidation different pyrroles and furans derivatives. Furthermore, procedure was implemented larger-scale HFIP distilled from reaction mixture reused (up to 4 cycles) without significant detriment outcome, which remarks its sustainability applicability.