Highly Enantioselective Construction of Polycyclic Spirooxindoles by Organocatalytic 1,3-Dipolar Cycloaddition of 2-Cyclohexenone Catalyzed by Proline-Sulfonamide

The enantioselective 1,3-dipolar cycloaddition of 2-cyclohexene-1-one and azomethine ylides generated in situ from isatins and amino esters was developed by employing prolinosulfonamides as the catalyst. Consequently, novel polycyclic spirooxindole scaffolds with three contiguous stereocenters were prepared in high yield (up to 95%) with excellent diastereo-(>20:1dr) and enantioselectivity (up to 99% ee).