β‑Functionalization of Indolin-2-one-Derived Aliphatic Acids for the Divergent Synthesis of Spirooxindole γ‑Butyrolactones

β-Functionalization
of indolin-2-one-derived aliphatic acids
has been applied in formal [3 + 2] annualtions for catalyst-free and
divergent synthesis of two series of structurally interesting 3,3′-spirooxindole
γ-butyrolactones that may be attractive for potential drug discovery.
These findings also pave the way for further diversity-oriented synthesis
of spirooxindoles starting from indolin-2-one-derived aliphatic acids
or their derivatives.