The asymmetricepoxidation of 2‐oxoindoline‐3‐ylidene acetaldehydes, catalyzed by diarylprolinol silyl ether, has been developed. The reaction provides oxindole derivatives possessing chiral epoxides in good yield with good diastereoselectivity and excellent enantioselectivity.
A novel asymmetric nucleophilic epoxidation for alpha-ylideneoxindole esters has been successfully devised, resulting in enantioenriched spiro compounds with two new contiguous stereocenters. The employed (S)-alpha,alpha-diphenylprolinol functions as a bifunctional catalyst, creating a complex H-bond network in conjunction with a substrate and an oxidant.