Direct Transition-Metal-Free Enantioselective Hydroxylation: Expeditious Access to 3-Functionalized 3-Hydroxy-2-oxindoles

Inspired by the ubiquitous prevalence of 3-hydroxyoxindoles in natural products and pharmaceuticals, we herein disclose a direct and practical transition-metal-free asymmetric hydroxylation using commercially available Davis enantiopure oxaziridines as efficient oxidants, expeditiously affording an array of medicinally active 3-functionalized 3-hydroxy-2-oxindoles bearing quaternary stereocenters. The protocol features cheap reactants, ease of operation, scalability, and good functional-group tolerance and efficient formal synthesis of natural products. A direct transition-metal-free asymmetric hydroxylation using commercially available enantiopure Davis oxaziridine as an efficient oxidant is disclosed. An array of medicinally and optically active 3-aryl/alkyl-3-hydroxy-2-oxindoles with a tetrasubstituted stereocenter were obtained in good yields and enantioselectivities. The protocol features ease of operation, scalability, and good functional-group tolerance.+ image