Base-Promoted Formal (3 + 2) Cycloaddition of α‑Halohydroxamates with Electron-Deficient Alkenyl-iminoindolines To Synthesize Spiro-indolinepyrrolidinones

Construction
of pyrrolidinyl-spiroindoles with easily available
starting materials has attracted considerable attention from the synthesis
community and is in great demand. Here, we describe a base-promoted
formal (3 + 2) cycloaddition of α-halohydroxamates with alkenyl-iminoindolines.
The present methodology features mild reaction conditions and a broad
substrate scope with up to 99% yield and excellent diastereoselectivity.
The versatility of this approach is demonstrated through valuable
synthetic transformations. Preliminary mechanistic studies shed light
on the mechanism of this cycloaddition process.