SmCp^R₂-mediated cross-coupling of allyl and propargyl ethers with ketoesters and a telescoped approach to complex cycloheptanols

Abstract

A highly regio- and diastereoselective cross-coupling of allyl/propargyl ethers and δ-ketoesters, mediated by SmCp^R₂ reagents, delivers decorated δ-lactones. Screening of the Cp ligands on Sm(ii) was employed to achieve high regio and diastereocontrol in some cases. Crucially, SmI₂ gave unsatisfactory results in the transformation. The process has been exploited in a telescoped approach to complex cycloheptanols in which two Sm(ii) reagents act in turn on the simple starting materials.