Synlett 2010(18): 2765-2770  
DOI: 10.1055/s-0030-1259000
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Enantioselective Nitroaldol Reaction of α-Keto Esters Catalyzed by a Copper(II)-Bisoxazolidine Complex

Hanhui Xu, Christian Wolf*
Department of Chemistry, Georgetown University, Washington, DC 20057, USA
Fax: +1(202)6876209; e-Mail: cw27@georgetown.edu;
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Publikationsverlauf

Received 23 August 2010
Publikationsdatum:
12. Oktober 2010 (online)

Abstract

A wide range of aliphatic and aromatic α-keto esters has been transformed to α-hydroxy-β-nitro esters via the Cu(II)-bisoxa­zolidine-catalyzed Henry reaction. In the presence of 10 mol% of the chiral catalyst, nitroaldol products were obtained in up to 95% yield and 76% ee.

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A control experiment showed that the nitroaldol reaction proceeds very slowly in the presence of AgClO4 and only 12% of racemic 2 were obtained after 24 h. We therefore believe that the in situ formation of Cu(ClO4)2 from AgClO4 and CuCl2, which is visible by the precipitation of AgCl, is quantitative.