Domino Annulation Reaction of Sulfur Ylides and Morita-Baylis-Hillman Carbonates of Isatins: Synthesis of Oxospiro[bicyclo[3.1.0]hexane-6,3'-indolin] Scaffolds.

A sequential [3 + 2]/[2 + 1] annulation domino reaction of crotonate-derived sulfur ylides and Morita-Baylis-Hillman carbonates of isatins for the construction of oxospiro[bicyclo[3.1.0]hexane-6,3'-indolin] scaffolds in moderate to good yields with almost 1:1 diastereoselectivity has been developed. Mild reaction conditions and readily accessible starting materials as well as excellent functional group compatibility render this transformation a powerful tool for the synthesis of spirocyclopropyloxindoles. A gram-scale synthetic procedure was also successfully carried out and a plausible reaction mechanism could be proposed.