Equatorial preference in the GaCl3-promoted ethenylation of cyclic ketones

Article abstract of DOI:10.1055/s-2002-19298

Silyl enol ethers derived from substituted cyclohexanones are ethenylated with trimethylsilylethyne in the presence of GaCl₃. Carbon-carbon bond formation was completed in less than 5 min at room temperature and protodegallation of the organogallium intermediate formed with 6 M sulfuric acid gave β-enones. The reactions exhibit a bias for the equatorial C-C bond formation, which contrasts the axial stereochemistry of enolate alkylation. The origin of this stereoselectivity is discussed.