The role of cinchona alkaloids in enantioselective hydrogenation reactions: are they modifiers or hosts involved in supramolecular heterogeneous catalysis?

Margitfalvi, József L.; Tálas, Emı́lia; Tfirst, E.; Kumar, Chepuri V. Suneel; Gergely, András

doi:10.1016/s0926-860x(99)00318-x

Cited by 60 publications

(37 citation statements)

References 34 publications

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“…The addition of 1 · 10 )6 M Q has eliminated this decrease as it is reflected by the forms of conversion-ee diff and conversion-acc diff dependencies. In our earlier studies [20,21] the role of ATAs has been attributed to the suppression of the formation of CD dimer. The present results indicate also that the adsorption of ATAs at the Pt surface might prevent the hydrogenation of the quinoline ring of CD.…”

Section: Discussionmentioning

confidence: 97%

“…Recently it has been suggested by different authors that in the enantioselective hydrogenation of a-keto esters the rate acceleration effect does not exist [24,25], i.e., the rate enhancement cannot only be explained by the base catalysis induced by tertiary amines, such as CD [20,26]. It has also been suggested that CD suppresses both the decomposition of ethyl pyruvate to form chemisorbed CO at the Pt surface and formation of oligomers with general formula of C x H y O z [27].…”

Section: Discussionmentioning

confidence: 99%

“…The catalytic runs were carried out as described earlier [11,20]. Special care was done to use relatively low concentration of cinchonidine.…”

Section: Methodsmentioning

confidence: 99%

“…Both the injection and the premixing techniques were applied to introduce the alkaloid or the substrate into the reactor [20]. In the experiments presented in this study the following experimental variables were altered: (i) mode of introduction of the reaction components, (ii) concentration of modifiers, (iii) addition of achiral tertiary amines, and (v) addition of acetic acid to the reactions mixture.…”

Section: Methodsmentioning

confidence: 99%

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Enantioselective hydrogenation of ethyl pyruvate over cinchonidine-Pt/Al2O3 catalyst. A reaction kinetic approach

2006

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A new reaction kinetic approach was used to describe the enantioselective hydrogenation of ethyl pyruvate over cinchona-Pt catalyst. The above reaction was considered as the sum of two parallel reactions: (i) racemic hydrogenation resulting in R-and S-product in equal amount and (ii) enantioselective hydrogenation leading to the exclusive formation of one of the two optically isomers. New terms such as acc diff and k e /k r (where k e and k r are the rate constants of the enantioselective and racemic hydrogenation, respectively) were introduced to characterize the relationship between the enantioselective and the racemic hydrogenation reactions. Results obtained show that the formation of R-product is rate accelerated, while the formation of S-product is decelerated. The results indicate also that the overall rate increase is a kinetic phenomenon and cannot be attributed to the suppression of the poisoning effect of CO or oligomers formed from ethyl pyruvate. The strong rate acceleration effect of achiral tertiary amines (ATAs) added to the reaction mixture was attributed to the decrease of the loss of modifier during the hydrogenation experiments.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

“…The catalytic runs were carried out as described earlier [11,20]. Special care was done to use relatively low concentration of cinchonidine.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Enantioselective hydrogenation of ethyl pyruvate over cinchonidine-Pt/Al2O3 catalyst. A reaction kinetic approach

2006

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“…Its diastereomer, quinidine, is used as a cardiac anti-arrhythmic drug and in the treatment of atrial fibrillation [2,3]. Cinchona alkaloids and their modified derivates are important catalysts in stereoselective organic synthesis [4] and they are also used in the production of high-performance liquid chromatography stationary phases for chiral separations [5,6].…”

Section: Introductionmentioning

confidence: 99%

Capillary electrophoretic chiral separation of Cinchona alkaloids using a cyclodextrin selector

Tsimachidis

Česla

Hájek

et al. 2008

J of Separation Science

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A new capillary electrophoretic method for the chiral separation of four major Cinchona alkaloids (quinine/quinidine and cinchonine/cinchonidine) was developed using heptakis-(2,6-di-O-methyl)-beta-cyclodextrin as the chiral selector. The inner walls of the separation capillary were modified with a thin polyacrylamide layer, which substantially reduced the electroosmotic flow and improved the chiral resolution and the reproducibility of the migration time of the analytes. Various operation parameters were optimised, including the pH, the capillary temperature, the concentration of the background electrolyte, and the concentration of the chiral selector. Baseline separation of the two diastereomer pairs was achieved in 12 minutes in ammonium acetate background electrolyte pH 5.0 with addition of cyclodextrin in a concentration of 3 mM or higher.

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Hydrogenation – Heterogeneous

Gallezot

2002

Encyclopedia of Catalysis

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The development of heterogeneous hydrogenation catalysis started at the beginning of the twentieth century. It is still the most developed field of catalysis in terms of the varieties of catalysts and applications. This article gives a survey in two parts of all the aspects of heterogeneous catalysis dealing with the hydrogenation of organic molecules. The first deals with all the fundamental aspects including molecular mechanisms, kinetics of reactions, catalyst structure–activity/selectivity relationships, and all the physicochemical factors affecting the rate and selectivity of hydrogenation reactions. The second part deals with more practical aspects such as the description of the different types of hydrogenation catalysts, on their selection to achieve a specific hydrogenation reaction, and of their utilization in reactors.

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The role of cinchona alkaloids in enantioselective hydrogenation reactions: are they modifiers or hosts involved in supramolecular heterogeneous catalysis?

Cited by 60 publications

References 34 publications

Enantioselective hydrogenation of ethyl pyruvate over cinchonidine-Pt/Al2O3 catalyst. A reaction kinetic approach

Enantioselective hydrogenation of ethyl pyruvate over cinchonidine-Pt/Al2O3 catalyst. A reaction kinetic approach

Capillary electrophoretic chiral separation of Cinchona alkaloids using a cyclodextrin selector

Hydrogenation – Heterogeneous

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