SmCpR2-mediated cross-coupling of allyl and propargyl ethers with ketoesters and a telescoped approach to complex cycloheptanols.

A highly regio- and diastereoselective cross-coupling of allyl/propargyl ethers and δ-ketoesters, mediated by SmCpR2 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.