Asymmetric Three-Component Cyclizations toward Structurally Spiro Pyrrolidines via Bifunctional Phosphonium Salt Catalysis.

Asymmetric multicomponent reactions toward optically pure compounds are highly attractive but extremely challenging. Presented herein is a highly diastereo- and enantioselective three-component cyclization of exocyclic alkenes with aldehydes and amino esters, which was enabled by bifunctional phosphonium salt catalysts. A wide range of multiply substituted spiro pyrrolidine derivatives were prepared in high yields with excellent stereoselectivities. Of note, this is the first example of a catalytic asymmetric three-component reaction with a phase-transfer catalysis system.