Noncovalent organocatalysis: a powerful tool for the nucleophilic epoxidation of α-ylideneoxindoles.

A novel asymmetric nucleophilic epoxidation for α-ylideneoxindole esters has been successfully devised, resulting in enantioenriched spiro compounds with two new contiguous stereocenters. The employed (S)-α,α-diphenylprolinol functions as a bifunctional catalyst, creating a complex H-bond network in conjunction with a substrate and an oxidant.