Asymmetric hydrogenation catalysis via ion-pairing in chiral ionic liquids.

Beitrag in einer Fachzeitschrift
(Originalarbeit)


Details zur Publikation

Autor(en): Wagner V, Schulz P, Wasserscheid P
Zeitschrift: Journal of Molecular Liquids
Verlag: Elsevier
Jahr der Veröffentlichung: 2014
Band: 192
Seitenbereich: 177-184
ISSN: 0167-7322


Abstract


The relevant interactions between the org. ions of ionic liqs. (ILs) include van der Waals forces, hydrogen bonding and Coulombic interactions. In solns. these interactions lead to the formation of aggregates. Depending on the strength of the interactions and the concn. of the IL in the solvent, different aggregates are formed with ion-pairs being the dominant species at low concns. A probe for investigating these interactions is the enantioselectivity of a reaction carried out on a prochiral ion in presence of its chiral counter-ion. As asym. induction requires structurally well-defined interactions, the induced enantioselectivity can be correlated to ion aggregate formation. Depending on the substrate IL concn. an enantioselectivity of up to 94% was realized. The catalytic results were linked to the probability of the ion pair formation as evidenced by DOSY-NMR measurements and dielec. relaxation spectroscopy. The expansion of this principle to chiral ionic liqs. that can be easily decompd. to chiral building blocks of synthetic relevance led to the development of two approaches: (a) the application of an IL substrate consisting of a chiral cation and a keto-functionalized, prochiral carboxylate counter-ion allowing for the synthesis of chiral esters in the sequence of IL hydrogenation and esterification, and (b) reversible binding of a prochiral substrate to the cation of an IL with a chiral, enantiopure anion allowing the synthesis of neutral chiral building blocks in a sequence of binding, hydrogenation and splitting. The latter approach was tested for two ILs based on the hydroxyl-functionalized cation cholinium to which a prochiral keto functionalized carboxylic acids was reversibly attached via esterification. The hydrogenation of such prochiral ester cation in the presence of enantiopure anions resulted in ee of up to 63%. [on SciFinder(R)]



FAU-Autoren / FAU-Herausgeber

Schulz, Peter Dr.
Lehrstuhl für Chemische Reaktionstechnik
Wagner, Valentin
Lehrstuhl für Chemische Reaktionstechnik
Wasserscheid, Peter Prof. Dr.
Lehrstuhl für Chemische Reaktionstechnik


Zitierweisen

APA:
Wagner, V., Schulz, P., & Wasserscheid, P. (2014). Asymmetric hydrogenation catalysis via ion-pairing in chiral ionic liquids. Journal of Molecular Liquids, 192, 177-184.

MLA:
Wagner, Valentin, Peter Schulz, and Peter Wasserscheid. "Asymmetric hydrogenation catalysis via ion-pairing in chiral ionic liquids." Journal of Molecular Liquids 192 (2014): 177-184.

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Zuletzt aktualisiert 2018-10-08 um 02:10