Bi-Catalyzed [3 + 2] Cycloaddition of C2-Spirocyclopropyl-indolin-3-ones with Carbonyls: Access to Spiro[furan-3,2'-indolin]-3'-ones.

Herein, the first Bi-catalyzed [3 + 2] cycloaddition of C2-spirocyclopropyl-indolin-3-ones and carbonyl compounds has been developed under mild conditions, enabling efficient and diastereoselective access to multisubstituted spiro[furan-3,2'-indolin]-3'-ones (73 examples, up to 91% yield, >20:1 dr). This transformation employs C2-spirocyclopropyl-indolin-3-ones as C3 synthons and exhibits broad substrate tolerance, accommodating various aromatic aldehydes, α,β-unsaturated aldehydes, aliphatic aldehydes, and even challenging ketones.