Issue 7, 2004
From the journal:

Organic & Biomolecular Chemistry

Direct catalytic asymmetric aldol reactions of pyruvates: scope and mechanism

Nicholas Gathergood,*ab   Karsten Juhl,a   Thomas B. Poulsen,a   Karl Thordrupa  and  Karl Anker Jørgensen*a  

* Corresponding authors

a Danish National Research Foundation: Center for Catalysis, Department of Chemistry, Aarhus University, Aarhus C, Denmark
E-mail: kaj@chem.au.dk
Fax: 45 8619 6199
Tel: 45 8942 3910

b Department of Medicinal Chemistry, Victorian College of Pharmacy, Monash University, Parkville, Australia
E-mail: nicholas.gathergood@vcp.monash.edu.au
Fax: 61 3 99039582
Tel: 61 3 99039543

Abstract

The direct aldol reaction of 2-ketoesters catalyzed by chiral bisoxazoline copper(II) complexes has been investigated. First the direct homo-aldol reaction of ethyl pyruvate is reported which proceeds to give diethyl 2-hydroxy-2-methyl-4-oxoglutarate. This was isolated as the more stable optically active isotetronic acid in good yield and enantiomeric excess in the absence of bases such as amines. Detailed investigations of the use of different chiral Lewis acids as the catalyst, amines, ratios of chiral bisoxazoline copper(II) salts : amine, and solvents gave up to 96% ee of the isotetronic acid. Then the reaction was extended to a cross-aldol reaction of various 2-ketoesters with activated carbonyl compounds to give the cross-aldol adduct with excellent enantiomeric excess. Furthermore, the synthesis of the isotetronic acids was investigated from these cross-aldol adducts giving important information about the formation of the stereogenic centers during the aldol reaction. Based on the absolute configuration of the homo-aldol adduct the mechanism for the aldol reaction is discussed.

Graphical abstract: Direct catalytic asymmetric aldol reactions of pyruvates: scope and mechanism

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Article information

DOI
https://doi.org/10.1039/B316092K
Article type
Paper
Submitted
11 Dec 2003
Accepted
12 Feb 2004
First published
09 Mar 2004

Org. Biomol. Chem., 2004,2, 1077-1085

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Direct catalytic asymmetric aldol reactions of pyruvates: scope and mechanism

N. Gathergood, K. Juhl, T. B. Poulsen, K. Thordrup and K. A. Jørgensen, Org. Biomol. Chem., 2004, 2, 1077 DOI: 10.1039/B316092K

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