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.