Catalytic asymmetric epoxidation of α,β-unsaturated carbonyl compounds

This article summarizes recent progress in catalytic asymmetric epoxidation of alpha, beta-unsaturated carbonyl compounds. Asymmetric epoxidation of alpha, beta-unsaturated carbonyl compounds remains one of the most important functional group manipulations in organic synthesis, because of the usefulness of the corresponding enantiomerically enriched alpha, beta-epoxy carbonyl compounds. Since the initial report by Julia and co-workers, catalytic asymmetric epoxidation of alpha, beta-epoxy ketones (enones) has been studied using several methodologies. In recent years, we and others have achieved efficient catalytic asymmetric epoxidation of enones using a variety of catalysts, including phase-transfer catalysts, polyamino acid catalysts, chiral ligand-metal peroxide complexes, and so on. On the other hand, there are only a few reports of catalytic asymmetric epoxidation of alpha, beta-unsaturated carboxylic acid derivatives. Very recently we have reported the first example of a general catalytic asymmetric epoxidation of alpha, beta-unsaturated carboxylic acid imidazolides to afford the corresponding alpha, beta-epoxy peroxycarboxylic acid tert-butyl esters, which are transformed efficiently into alpha, beta-epoxy esters, am ides, aldehydes, and gamma, delta-epoxy beta-keto esters, The mechanism of the several reactions and applications to a catalytic asymmetric synthesis of biologically active compounds are also described briefly.