Diastereoselective [3 + 1] Cyclization Reaction of Oxindolyl Azaoxyallyl Cations with Sulfur Ylides: Assembly of 3,3′-Spiro[β-lactam]-oxindoles

Oxindoles and β-lactams are
attractive structural motifs
because of their unique biological importance. However, the fusion
of the two moieties featuring 3,3′-spirocyclic scaffolds is
a challenging task in organic synthesis. Herein we designed a novel
type of oxindole-based azaoxyallyl cation synthons, which could readily
participate in the [3 + 1] cyclization with sulfur ylides. With this
protocol, a collection of 3,3-spiro­[β-lactam]-oxindoles were
facilely produced in up to 94% yield with perfect diastereoselectivity.