Highly Enantio‐ and Diastereoselective Synthesis of Tetrahydrofuran Frameworks via Chiral Lewis Acid‐Catalyzed Formal [3+2] Cycloaddition of Allylsilanes

A formal [3+2] cycloaddition via cyclization/1,2-hydride shift initiated by nucleophilic attack of allylsilanes has been developed for the enantioselective synthesis of cis-2,5-disubstituted tetrahydrofuran-3-ones. In the presence of chiral oxazaborolidinium ion (COBI) catalyst, the reaction proceeded in high yields (up to 88%) with excellent stereoselectivity (up to 99% ee, > 20:1 dr). Key advantages of this approach are its unprecedented ability to forge THF scaffolds asymmetrically without inherent chirality, its high stereoselectivity including cis-selectivity, and its capability to control four stereocenters in a single transformation.