α-Lithioalkoxysilanes: applications to alkene synthesis

α-Lithioalkoxysilanes [RO(Me2)Si]CH(Li)(X), where R=Me or Et and X=H or SiMe3, react with carbonyl compounds in hydrocarbon solution to produce alkenes in moderate to high yield via Peterson-type reactions. For X=SiMe3, the corresponding vinylsilanes are isolated directly following work-up. The reaction is regiospecific and shows fair stereoselectivity. When the carbonyl substrates are cyclic ketones in six- or seven-membered rings, the products are exocyclic alkenes. For X=H, the initial product is a β-hydroxysilane, which is then efficiently converted to the corresponding terminal alkene by heating with sodium acetate in acetic acid. Both types of α-lithioalkoxysilane reagents are amenable to reaction with enolizable carbonyl compounds.