Catalytic asymmetric epoxidation of α, β-unsaturated carbonyl compounds

This article summarizes recent progress in catalytic asymmetric epoxidation of α, β-unsaturated carbonyl compounds. Asymmetric epoxidation of α, β-unsaturated carbonyl compounds remains one of the most important functional group manipulations in organic synthesis, because of the usefulness of the corresponding enantiomerically enriched α, β-epoxy carbonyl compounds. Since the initial repog by Juliá and co-workers, catalytic asymmetric epoxidation of α, β-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 α, β-unsaturated carboxylic acid derivatives. Very recently we have reported the first example of a general catalytic asymmetric epoxidation of α,β-unsaturated carboxylic acid imidazolides to afford the corresponding α, β-epoxy peroxycarboxylic acid tert-butyl esters, which are transformed efficiently into α, β-epoxy esters, amides, aldehydes, and γ, δ-epoxy β-keto esters. The mechanism of the several reactions and applications to a catalytic asymmetric synthesis of biologically active compounds are also described briefly.