Oxidative Cleavage of Indoles Mediated by Urea Hydrogen Peroxide or H2O2 in Polar Solvents

Article abstract of DOI:10.1002/adsc.202100214

The oxidative cleavage of indoles (Witkop oxidation) involving the use of 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 the one affording the corresponding 2-ketoacetanilides generally in higher yields The protocol described has also enabled the oxidation of different pyrroles and furans derivatives. Furthermore, the procedure was implemented in a larger-scale and HFIP was distilled from the reaction mixture and reused (up to 4 cycles) without a significant detriment in the reaction outcome, which remarks its sustainability and applicability. (Figure presented.).