Asymmetric [3 + 2] Cycloaddition Reaction of Isatin-Derived MBH Carbonates with 3‑Methyleneoxindoles: Enantioselective Synthesis of 3,3′-Cyclopentenyldispirooxindoles Incorporating Two Adjacent Quaternary Spirostereocenters

A highly
regio- and stereoselective [3 + 2] cycloaddition reaction
for constructing novel 3,3′-cyclopentenyldispirooxindoles incorporating
two adjacent quaternary spirostereocenters is reported. Under the
mild conditions, the asymmetric annulation of isatin-derived MBH carbonates
with 3-methyleneoxindoles involving a chiral tertiary amine catalyst
provides the corresponding dispirooxindole frameworks with an extraordinary
level of enantioselective control. Further synthetic utility of this
method was demonstrated by the gram-scale experiment and simple transformation
of the obtained product. Moreover, a plausible mechanism for this
annulation reaction was also proposed on the basis of the control
experiments.