Diastereo- and Enantioselective Construction of 3,3'-Pyrrolidinyldispirooxindole Framework via Catalytic Asymmetric 1,3-Dipolar Cycloadditions.

The first catalytic enantioselective construction of a 3,3'-pyrrolidinyldispirooxindole scaffold has been established via organocatalytic asymmetric 1,3-dipolar cycloadditions of isatin-derived azomethine ylides with methyleneindolinones, which afforded structurally complex bis-spirooxindoles containing three contiguous and two quaternary stereogenic centers in generally high yields (up to 99%) and excellent diastereo- and enantioselectivities (up to >95:5 dr, 98% ee). This reaction also provides a good example for the application of catalytic asymmetric 1,3-dipolar cycloadditions in constructing enantioenriched bis-spirooxindole frameworks with structural complexity and rigidity.