Enantioselective Synthesis of Quaternary 3‑Aminooxindoles via Organocatalytic Asymmetric Michael Addition of 3‑Monosubstituted 3‑Aminooxindoles to Nitroolefins

An
enantioselective synthesis of quaternary 3-aminooxindoles with
3-monosubstituted 3-aminooxindoles as nucleophiles is first presented.
A Michael addition reaction of 3-monosubstituted 3-aminooxindoles
to nitroolefins has been developed with a bifunctional thiourea-tertiary
amine as a catalyst to afford a range of 3,3-disubstituted oxindoles
bearing adjacent quaternary-tertiary centers in good results (up to
98% yield, >99:1 dr, and 92% ee). We also demonstrate the potential
synthetic utility of this methodology by a transformation of the product
into a spirocyclic oxindole compound.