Asymmetric Michael/Cyclization Cascade Reaction of 3-Isothiocyanato Oxindoles and 3-Nitroindoles with Amino-Thiocarbamate Catalysts: Enantioselective Synthesis of Polycyclic Spirooxindoles

An unprecedented organocatalytic asymmetric Michael/cyclization cascade reaction of 3-isothiocyanato oxindoles and 3-nitroindoles has been disclosed. A wide range of enantioenriched polycyclic spirooxindoles, containing three contiguous chiral centers with two of them having quaternary stereocenters, could be smoothly obtained with satisfactory results (up to 99% yield, >99:1 dr, and 96% ee). This method is very promising because the reaction is scalable, and the versatile transformations of the products into other spirocyclic oxindoles are also feasible.