Catalytic, asymmetric synthesis and diastereoselective aldol reactions of dipropionate equivalents |
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Authors: | Calter Michael A Song Wei Zhou Jianguang |
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Affiliation: | Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, USA. calter@chem.rochester.edu |
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Abstract: | The dimer of methylketene can be conveniently prepared in one step and high enantiomeric excess from propionyl chloride, using a catalytic amount of a silylated cinchona alkaloid as a source of chirality. Opening of the dimer with a lithiated sulfonamide affords a beta-ketosulfonimide, which undergoes Sn(II)-mediated aldol reactions to diastereoselectively afford the anti,syn-aldol adduct. Alternatively, reduction of the dimer to the beta-hydroxy ketone, followed by acylation, affords a beta-acyloxyl ketone that undergoes diastereoselective, dialkylboron chloride-mediated aldol reactions to produce the anti,anti-aldol adduct. |
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