Carbonyl oxides, formed by ozonolysis of enol ethers [e.g., 1-methoxy-4,8-dimethylnona-1,7-diene (4)], undergo stereoselective intramolecular cycloadditions to unactivated alkenes to give bicyclic dioxolanes. The dioxolanes were easily transformed by catalytic hydrogenation into beta-hydroxycarbonyl compounds and 1,3-diols, thus providing a novel route to 1,3-dioxygenated products.