Oxidation of homochiral ketals by rhenium(VII) oxide. V

Article abstract of DOI:10.1016/S0040-4039(00)74753-8

2-Hydroxyethyl enol ethers react with Re₂O₇ to produce 2-hydroxyketals. Where homochiral starting enol ethers are employed, greater than 99:1 diastereoselectivities are obtained. The stereocontrol is rationalized by invoking a transition state that approximates the geometry of a metallaoxetane. Finally, homochiral ketals are themselves oxidized to provide 2-hydroxyketals with high diastereoselectivity.