Organocatalytic Asymmetric Michael/Cyclization Cascade Reactions of 3‑Hydroxyoxindoles/3-Aminooxindoles with α,β-Unsaturated Acyl Phosphonates for the Construction of Spirocyclic Oxindole-γ-lactones/lactams

Enantioselective
Michael/cyclization cascade reactions of 3-hydroxyoxindoles/3-aminooxindoles
with α,β-unsaturated acyl phosphonates by using a cinchonine
derived squaramide as the catalyst were developed. A broad range of
spirocyclic oxindole-γ-lactones/lactams could be obtained in
moderate to excellent yields (up to 98%) with good to excellent diastereo-
and enantioselectivities (up to >99:1 dr and 97% ee) under mild
conditions.
This work represents the first example about the α,β-unsaturated
acyl phosphonates for the asymmetric construction of spirocyclic oxindoles.