Design of New Modifiers for the Enantioselective Hydrogenation of Ethyl Pyruvate

Schürch, M.; Heinz, Thomas; Aeschimann, Roland; Mallát, Tamás; Pfaltz, Andreas; Baiker, Alfons

doi:10.1006/jcat.1997.1919

Cited by 90 publications

(35 citation statements)

References 36 publications

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“…[31] Recently, we have found a considerable non-linearity in the hydrogenation of 1 using mixtures of CN and a synthetic modifier (R)-NPE (1-{1-naphthyl}-2-{pyrrolidin-1-yl}ethanol). [32] Deviation from the expected linear correlation was rationalized by rapid saturation of the naphthyl rings of NPE in the early stage of the reaction, resulting in a weak adsorption and replacement of saturated NPE by the more stable and strongly adsorbing cinchona alkaloid.…”

Section: Resultsmentioning

confidence: 96%

Non‐Linear Effect of Modifier Composition on Enantioselectivity in Asymmetric Hydrogenation over Platinum Metals

2003

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Prominent non-linear behavior was observed when mixtures of cinchona alkaloids were applied as chiral modifiers in enantioselective hydrogenations over Pt/Al 2 O 3 and Pd/TiO 2 . The phenomenon is traced to differences in the strength and geometry of alkaloid adsorption on the metal surface. In ethyl pyruvate hydrogenation under close to ambient conditions the weaker adsorbing quinidine (QD) outperformed the generally preferred modifier cinchonidine (CD) and afforded the highest ee (96 ± 98%) at 1 ± 5 bar. In the partial hydrogenation of 4-methoxy-6-methyl-2-pyrone to the dihydro derivative 4 CD gave 73% ee to (S)-4 and QD provided 72% ee to (R)-4, and still the alkaloid mixture containing less than 5 mol % CD afforded 15% ee to (S)-4. This nonlinear behavior may be advantageous in asymmetric synthesis as low purity chiral compounds can be applied as efficient modifiers for Pt or Pd.

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Section: Resultsmentioning

confidence: 96%

Non‐Linear Effect of Modifier Composition on Enantioselectivity in Asymmetric Hydrogenation over Platinum Metals

2003

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“…1) catalysts has been widely studied by Baiker and co-workers [1][2][3][4][5] in the case of alumina supported metals. Such catalysts were found to promote reduction and induce stereoselec-tivity in the ␣-carbonyl hydrogenation of pyruvates [6,7], ketopentolactone [8,9], other ␣-dicarbonyls [10], and, in general, on activated ketones (e.g. trifluoromethylketones) [11].…”

Section: Introductionmentioning

confidence: 99%

Multiphase heterogeneous catalytic enantioselective hydrogenation of acetophenone over cinchona-modified Pt/C

Perosa

Tundo

Selva

2002

Journal of Molecular Catalysis A: Chemical

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The multiphase heterogeneous enantioselective hydrogenation of acetophenone in the presence of cinchona-modified Pt/C was investigated. The system demonstrated the feasibility of this reaction on non-activated ketones. The reaction proceeded selectively, at room temperature and atmospheric pressure, towards the formation of 1-phenylethanol, with up to 20% ee (enantiomeric excess) of either enantiomer depending on the modifier used. A mode of action of the modifier is proposed to account for the mechanism. A comparison with other systems indicates that the investigated system likely acts by a different mechanism, and that it is quite specific for acetophenone.

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“…5). Based on this model for the origin of the enantioselectivity of catalysts templated with cinchonidine, new modifiers based on the cinchona alkaloid, such as dihydroapovincaminic acid ethyl ester, [24] strychnine, [25] and others, [26,27] have been identified and have been shown to work with varying degrees of success.…”

Section: Other Chiral Templatesmentioning

confidence: 99%

Enantioselectivity on Surfaces

Rampulla¹,

Gellman²

2008

Dekker Encyclopedia of Nanoscience and Nanotechnology, Second Edition - Six Volume Set (Print Version)

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Design of New Modifiers for the Enantioselective Hydrogenation of Ethyl Pyruvate

Cited by 90 publications

References 36 publications

Non‐Linear Effect of Modifier Composition on Enantioselectivity in Asymmetric Hydrogenation over Platinum Metals

Non‐Linear Effect of Modifier Composition on Enantioselectivity in Asymmetric Hydrogenation over Platinum Metals

Multiphase heterogeneous catalytic enantioselective hydrogenation of acetophenone over cinchona-modified Pt/C

Enantioselectivity on Surfaces

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