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.