New silicon-mediated ring expansion of n-sized conjugated cycloalkenones into homoallylic n+3 lactones

Silicon nucleophilic β-addition to various 2-cycloalkenones, followed ultimately by mild and rapid α-alkylation of the corresponding cycloalkanone enolates using diverse epoxides and BF3·OEt2, produces useful γ-lactols and γ-hydroxyketones. Hypervalent iodine-promoted oxidative fragmentation then yields regiospecifically unsaturated, 3-atom ring expanded, 8–10 membered homoallylic lactones with good control of alkene geometry.