Ring-opening of lactones with enolate nucleophiles: a simple access to functionalised β-ketoesters, β,δ-diketoesters and β-ketosulfoxides

γ-, δ- and ε-Lactones are readily opened by stabilised carbanions to the corresponding bis- or tris-silyl ethers, which can be selectively cleaved to 5- 6- or 7- silyloxy-3-ketoesters, 3,5-diketoesters, or 2-ketosulfoxides.