Copper-Catalyzed Umpolung of <i>N</i>-2,2,2-Trifluoroethylisatin Ketimines for the Enantioselective 1,3-Dipolar Cycloaddition with Benzo[<i>b</i>]thiophene Sulfones

Abstract

A copper-catalyzed umpolung of <i>N</i>-2,2,2-trifluoroethylisatin ketimines for the enantioselective 1,3-dipolar cycloaddition with benzo[<i>b</i>]thiophene sulfones was developed. Using a catalyst system consisting of an (<i>S</i>,<i>S_p</i>)-^<i>t</i>Bu-Phosferrox ligand, Cu(OTf)₂, and Cs₂CO₃, a range of pentacyclic spirooxindoles containing pyrrolidine and benzo[<i>b</i>]sulfolane subunits were obtained in high efficiency with excellent regio-, diastereo-, and enantioselectivites under mild conditions. The practicality and versatility of the reaction were also demonstrated.