Combining Ring-Closing Metathesis and Hydroformylation Strategies: A Novel Approach to Spirocyclic γ-Butyrolactones

Abstract
Di- or tetrahydropyrans with a vinyl side chain are obtained by diastereoselective ring-closing metathesis or by addition of vinylmagnesium chloride to an appropriately functionalized tetrahydropyranone. The resulting allylic alcohols are converted to spirocyclic hemiacetals under hydroformylation conditions. Oxidation yields the corresponding lactones.