The effect of water on the enantioselective hydrogenation of ethyl pyruvate and butane-2,3-dione using cinchona-modified Pt/Al2O3

Richard Peter Kerwin Wells, N R McGuire, Xiaobao Li, Robert L. Jenkins, P J Collier, R Whyman, G J Hutchings

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

A detailed study of Pt/alumina modified with cinchona alkaloids for the catalytic enantioselective hydrogenation of ethyl pyruvate to ethyl lactate and of butane-2,3-dione to 3-hydroxybutan-2-one is reported. Catalytic and H-1 NMR spectroscopic studies have been carried out on both systems to investigate the influence of water on modi er conformation and enantioselectivity. Interestingly, the presence of small amounts of water has been shown to result in an increase the proportion of the open 3 conformer of cinchonidine when it is present in dilute solutions. Increased enantioselectivity, coupled with an increase in the proportion of the open 3 conformation of cinchonidine, is observed after pretreatment of the pyruvate ester with the modi er prior to admission to the reaction vessel. In contrast, no analogous effects are observed with butane-2,3-dione. It is proposed that the enhancements in enantioselectivity are a consequence of hydrolysis of ethyl pyruvate by a process that is catalysed by the basic cinchona modi er. The pyruvic acid formed during the hydrolysis interacts with the modi er and this leads to a further enhancement in the concentration of open 3 conformer present. The results contribute to an understanding of the widely variable enantioselectivities reported in the literature for this reaction.

Original languageEnglish
Pages (from-to)2839-2845
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume4
Issue number12
DOIs
Publication statusPublished - 2002

Fingerprint

Cinchona
pyruvates
Enantioselectivity
Dione
butanes
Hydrogenation
hydrogenation
hydrolysis
Water
proportion
Pyruvic Acid
water
Conformations
Hydrolysis
lactates
alkaloids
Cinchona Alkaloids
augmentation
pretreatment
vessels

Keywords

  • modified platinum catalysts
  • Alpha-ketoesters
  • heterogeneous catalysis
  • asymmetric hydrogenation
  • molecular mechanics
  • combined NMR
  • alkaloids
  • solvents

Cite this

The effect of water on the enantioselective hydrogenation of ethyl pyruvate and butane-2,3-dione using cinchona-modified Pt/Al2O3. / Wells, Richard Peter Kerwin; McGuire, N R ; Li, Xiaobao; Jenkins, Robert L. ; Collier, P J ; Whyman, R ; Hutchings, G J .

In: Physical Chemistry Chemical Physics, Vol. 4, No. 12, 2002, p. 2839-2845.

Research output: Contribution to journalArticle

Wells, Richard Peter Kerwin ; McGuire, N R ; Li, Xiaobao ; Jenkins, Robert L. ; Collier, P J ; Whyman, R ; Hutchings, G J . / The effect of water on the enantioselective hydrogenation of ethyl pyruvate and butane-2,3-dione using cinchona-modified Pt/Al2O3. In: Physical Chemistry Chemical Physics. 2002 ; Vol. 4, No. 12. pp. 2839-2845.
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abstract = "A detailed study of Pt/alumina modified with cinchona alkaloids for the catalytic enantioselective hydrogenation of ethyl pyruvate to ethyl lactate and of butane-2,3-dione to 3-hydroxybutan-2-one is reported. Catalytic and H-1 NMR spectroscopic studies have been carried out on both systems to investigate the influence of water on modi er conformation and enantioselectivity. Interestingly, the presence of small amounts of water has been shown to result in an increase the proportion of the open 3 conformer of cinchonidine when it is present in dilute solutions. Increased enantioselectivity, coupled with an increase in the proportion of the open 3 conformation of cinchonidine, is observed after pretreatment of the pyruvate ester with the modi er prior to admission to the reaction vessel. In contrast, no analogous effects are observed with butane-2,3-dione. It is proposed that the enhancements in enantioselectivity are a consequence of hydrolysis of ethyl pyruvate by a process that is catalysed by the basic cinchona modi er. The pyruvic acid formed during the hydrolysis interacts with the modi er and this leads to a further enhancement in the concentration of open 3 conformer present. The results contribute to an understanding of the widely variable enantioselectivities reported in the literature for this reaction.",
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AB - A detailed study of Pt/alumina modified with cinchona alkaloids for the catalytic enantioselective hydrogenation of ethyl pyruvate to ethyl lactate and of butane-2,3-dione to 3-hydroxybutan-2-one is reported. Catalytic and H-1 NMR spectroscopic studies have been carried out on both systems to investigate the influence of water on modi er conformation and enantioselectivity. Interestingly, the presence of small amounts of water has been shown to result in an increase the proportion of the open 3 conformer of cinchonidine when it is present in dilute solutions. Increased enantioselectivity, coupled with an increase in the proportion of the open 3 conformation of cinchonidine, is observed after pretreatment of the pyruvate ester with the modi er prior to admission to the reaction vessel. In contrast, no analogous effects are observed with butane-2,3-dione. It is proposed that the enhancements in enantioselectivity are a consequence of hydrolysis of ethyl pyruvate by a process that is catalysed by the basic cinchona modi er. The pyruvic acid formed during the hydrolysis interacts with the modi er and this leads to a further enhancement in the concentration of open 3 conformer present. The results contribute to an understanding of the widely variable enantioselectivities reported in the literature for this reaction.

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