Catalytic Asymmetric Darzens Reactions
Peter Bako, Zsolt Rapi and Gyorgy Keglevich
Affiliation: Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, PO Box 91, 1521 Budapest, Hungary.
Optically active α,β-epoxy derivatives can be converted into many types of useful chiral compounds, such as chiral building
blocks and synthetic intermediates for biologically active compounds. The most up-to-date and most economical method for the preparation
of enantiomeric pure epoxides is the catalytic asymmetric Darzens condensation. The homogeneous phase and heterogeneus phase
(phase-transfer [PT]) catalytic methods for the synthesis of chiral α,β-epoxycarbonyl, epoxysulfonyl and epoxy-amide compounds are reviewed.
The effect of chiral catalysts on the yields and enantioselectivities of the epoxides was studied in homogeneous phase and under
PT conditions. The use of the most important chiral PT catalysts (ephedrinium salts, cinchona-derived salts and chiral crown ethers) in
Darzens condensation is also summarized. In some cases, the relationship between the structure of catalyst and its activity is also studied.
Keywords: Asymmeric reactions, Darzens condensation, phase-transfer catalysis.
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