Noncovalent Organocatalysis: A Powerful Tool for the Nucleophilic Epoxidation of α-Ylideneoxindoles

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.