Ozonolysis of Enol Ethers. Formation of 3-Alkoxy-1,2-dioxolanes by Concerted Addition of a Carbonyl Oxide to an Enol Ether

Article abstract of DOI:10.1021/jo00218a024

The ozonolyses of methyl vinyl ether, ethyl vinyl ether, and ethyl isopropenyl ether were studied in a variety of solvents.Alkoxy-1,2,4-trioxolanes and alkoxy-1,2-dioxolanes were the main products in pentane and ester solvents.These products arose from the carbonyl oxide (H2COO) produced upon ozonolysis undergoing 1,3-cycloaddition reactions with esters and activated olefins (enol ethers).From additional trapping experiments, the following relative dipolarophilicities toward the carbonyl oxide were inferred: aldehydes > enol ethers > esters - ca. ketones.Ozonolysis of stereolabeled ethyl vinyl-2-d1 ether gave ethoxy-1,2-dioxolane with retention of the alkene configuration at the -CHDCH(OEt)- linkage.This is the first example where stereospecificity, implying concertedness, has been directly observed for a reaction of a carbonyl oxide with a substrate.These results are consistent with the Criegee mechanism and extend it to the ozonolysis of enol ethers.