Kinetics and mechanism of oxymercuriation of αβ-unsaturated carbonyl compounds

Abstract

The products and the kinetics of methoxymercuriation of a series of αβ-unsaturated ketones and esters have been studied. Whereas the methoxymercuriation of αβ-unsaturated esters is stereospecific, the methoxymercuriation of the ketones leads to mixtures of diastereoisomers. The configuration of the products has been deduced from their ¹H n.m.r. spectra on the basis of chemical shifts and proton coupling constants. The results are consistent with the formation of a bridged ‘mercurinium’ ion intermediate. It is suggested that the mixtures of diastereoisomers obtained from the αβ-unsaturated ketones are the result of equilibria established after the oxymercuriation reaction.