Stereo- and regioselectivity of cyclization reactions in conformationally restricted epoxy ketones: evaluation of C- versus O-alkylation process

The intramolecular addition reaction of metal enolates of ketones to oxiranes has been applied to a series of epoxy ketones derived from cyclohexene oxide. γ-Hydroxy ketones (γ-HKs, C-alkylation products) or hydroxy enol ethers (HEEs, O-alkylation products) are obtained, depending on the nature of the cyclic transition state in each case involved and the application of the Fürst–Plattner rule. The formation of HEEs by reaction of the same epoxy ketones under acid conditions is also described. In some cases, regioconvergent or chemoselective processes are conveniently obtained.