In Situ Electrophilic Activation of Hydrogen Peroxide for Catalytic Asymmetric α-Hydroxylation of 3-Substituted Oxindoles

Peroxy trichloroacetimidic acid, in situ generated from aqueous hydrogen peroxide and trichloroacetonitrile, was found to act as a competent electrophilic oxygenating agent for the direct alpha-hydroxylation of oxindoles. The use of chiral 1,2,3-triazolium salt as a phase-transfer catalyst enabled rigorous absolute stereocontrol in the carbon-oxygen bond-forming reaction. The present study provides a new, yet practical method for straightforward access to optically active alpha-hydroxycarbonyl compounds.