Highly Enantioselective Organocatalytic Michael Addition/Cyclization Cascade Reaction of Ylideneoxindoles with Isothiocyanato Oxindoles: A Formal [3+2] Cycloaddition Approach to Optically Active Bispirooxindole Derivatives

A formal [3+2] cycloaddition involving the organocatalytic asymmetric Michael addition/cyclization cascade reaction of ylideneoxindoles with isothiocyanato oxindoles was developed. This method allows efficient and rapid synthesis of highly functionalized bispirooxindole products bearing three contiguous stereogenic centers with two quaternary stereocenters in almost quantitative yields with extremely high enantio- and diastereoselectivities.