ChemInform Abstract: Enantioselective Hydrogenation. Part 1. Surface Conditions During Methyl Pyruvate Hydrogenation Catalyzed by Cinchonidine‐Modified Platinum/Silica (EUROPT‐1)

Sutherland, I. M.; Ibbotson, A.; Moyes, R.B.; Wells, Peter B.

doi:10.1002/chin.199050057

Cited by 34 publications

(48 citation statements)

References 1 publication

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“…Both H-D exchange and deuterium addition have been used for studies on the mechanism of hydrogenation over Pt catalyst modified with CD [21,22]. These studies give information on the adsorption of DHCD and its geometry on the surface.…”

Section: H-d Exchange Of Modifiersmentioning

confidence: 99%

Enantioselective hydrogenation of ethyl pyruvate catalysed by cinchonine-modified Pt/Al2O3: tilted adsorption geometry of cinchonine

et al. 2005

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The enantioselective hydrogenation of ethyl pyruvate (EtPy) was studied on Pt-alumina catalyst modified by cinchonine (CN) and for comparison by cinchonidine (CD) in toluene and in AcOH. The effects of the modifiers concentration on the reaction rate and the enantioselectivity were examined. Using the Engelhard 4759 catalyst under mild experimental conditions (room temperature, hydrogen pressure 1 bar) in the case of CN (S)-ethyl lactate (EtLt) formed in excess (ee) (in AcOH ee max $ 88%; in toluene ee max $ 72%). In the case of CD (R)-EtLt formed in excess (in AcOH ee max $93%; in toluene ee max $ 84%). The results of H-D exchange measurements and results of modifier mixtures suggest that the compounds responsible for chiral induction are different intermediates, which structure depends mostly on the acidic or non-acidic nature of the hydrogenation medium. The proposed structure of intermediate responsible for enantioselection is an 1:1 CN-or CD-EtPy surface complex in which the quinoline skeleton of CD approximately parallel on the Pt surface while the quinoline plane of CN being tilted relative to the Pt surface under identical experimental conditions.

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Section: H-d Exchange Of Modifiersmentioning

confidence: 99%

Enantioselective hydrogenation of ethyl pyruvate catalysed by cinchonine-modified Pt/Al2O3: tilted adsorption geometry of cinchonine

et al. 2005

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“…This behavior may be related to the ability of acidic solvents to protonate the cinchona, which, as already mentioned above, changes their properties. It is worth pointing out that multiple studies have indicated that cinchona adsorption actually requires preconditioning of the surface with hydrogen [46][47][48][49][50][51], and that such preconditioning may help cinchona protonation [43]. In general, good solvents, where the adsorption equilibria for cinchona are shifted toward the liquid phase, have proven to be better for the chiral promotion of hydrogenation catalytic reactions [52][53][54][55][56][57].…”

Section: Adsorption On Metal Surfacesmentioning

confidence: 99%

The Physico-chemical Properties of Cinchona Alkaloids Responsible for their Unique Performance in Chiral Catalysis

Mink

Olsen

et al. 2008

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The physico-chemical properties of cinchona alkaloids have been characterized in connection to their use for catalytic enantioselective conversions. Adding to the previous identification of their active site at the nitrogen atom in the quinuclidine ring and the chiral environment provided by the carbon centers of the neighboring alcohol linker, an argument is made here for the importance of the adoption of certain rotational conformations by those cinchona alkaloids in optimizing their chiral promotion. Because catalysis with cinchona alkaloids involves a liquid phase, there is a dynamic conformation isomerization process controlled by a number of factors having to do with the exact structure of the cinchona as well as with the nature of the solvent used and, in the case of heterogeneous catalysis, the presence of a solid surface. Solvents of intermediate polarity have been found to be the best for dissolving the cinchona, for establishing rapid adsorption equilibria with metal surfaces, and for promoting chiral catalysis. Protonation also leads to a dramatic change in performance, locking the cinchona molecule in a specific conformation held in place by the counter anion of the acid used, and modifying the chemical and biological activity of the system. Comparative studies with several cinchona indicate that molecular groups attached to peripheral positions also exert a great influence on the conformational and adsorption behavior of these molecules.

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“…It is interesting to note that the formation of chiral pores within an ordered modifier arrangement was proposed by Wells and co-workers to explain the enantioselective behaviour [31], with permission from Elsevier) and b (S)-glutamic and methylacetoacetate on Ni{111} (4.6 9 3.8 nm) (Adapted with permission from [32]. Ó 2010, American Chemical Society) of Pt/cinchonidine catalysts [40]. Though subsequent experiments [41] discounted this proposed mechanism; the ideas remain highly relevant and potentially exploitable.…”

Section: Formation Of Supramolecular Assemblies (H Mod ? 1)mentioning

confidence: 96%

Fundamental Investigations of Enantioselective Heterogeneous Catalysis

et al. 2011

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Enantioselective catalysis is an increasingly important method of providing enantiomeric compounds for the pharmaceutical and agrochemical industries. To date, heterogeneous catalysts have failed to match the industrial impact achieved by homogeneous systems. One successful approach to the creation of heterogeneous enantioselective catalysts has involved the modification of conventional metal particle catalysts by the adsorption of chiral molecules. This article examines the contribution of effects such as chiral recognition and amplification to these types of system and how insight provided by surface science model studies may be exploited in the design of more effective catalysts.

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ChemInform Abstract: Enantioselective Hydrogenation. Part 1. Surface Conditions During Methyl Pyruvate Hydrogenation Catalyzed by Cinchonidine‐Modified Platinum/Silica (EUROPT‐1)

Cited by 34 publications

References 1 publication

Enantioselective hydrogenation of ethyl pyruvate catalysed by cinchonine-modified Pt/Al2O3: tilted adsorption geometry of cinchonine

Enantioselective hydrogenation of ethyl pyruvate catalysed by cinchonine-modified Pt/Al2O3: tilted adsorption geometry of cinchonine

The Physico-chemical Properties of Cinchona Alkaloids Responsible for their Unique Performance in Chiral Catalysis

Fundamental Investigations of Enantioselective Heterogeneous Catalysis

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