Quinine as an organocatalytic dual activator for the diastereoselective synthesis of spiro-epoxyoxindoles

A highly efficient organocatalytic approach has been developed for the diastereoselective epoxidation of (E)-3-ylidene-indolin-2-one derivatives using readily available natural product quinine and urea-hydrogen peroxide (UHP) in DCM at 10 °C to afford trans spiro-epoxyoxindoles which were further utilized to obtain β-hydroxy-α-amino esters by water mediated regioselective ring opening from the less hindered end with aniline derivatives, under sonication.