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

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.

Automated summary

The use of HFIP solvent in the oxidative cleavage of indoles results in higher yields of 2-ketoacetanilides, and it is also suitable for oxidation of various pyrroles and furans derivatives. The sustainable and practical nature of HFIP is demonstrated by its successful recycling up to 4 cycles in larger-scale reactions.