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Fine-tuning catalytic activity and selectivity-[Rh(amino acid thioamide)] complexes for efficient ketone reduction
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.ORCID iD: 0000-0001-5887-4630
2009 (English)In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, no 46, p. 6321-6324Article in journal (Refereed) Published
Abstract [en]

Amino acid-derived thioamides are prepared and evaluated as ligands in the rhodium-catalyzed asymmetric transfer hydrogenation of ketones in 2-propanol. It is found that increasing the steric bulk at the C-terminus of the ligand had a positive impact on both activity and selectivity in the reduction reaction. In order to find the optimum catalyst, a study is performed on a series of thioamide ligands having substituents of varying size.

Place, publisher, year, edition, pages
2009. Vol. 50, no 46, p. 6321-6324
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-31031DOI: 10.1016/j.tetlet.2009.08.116ISI: 000271055100027OAI: oai:DiVA.org:su-31031DiVA, id: diva2:274809
Available from: 2009-11-02 Created: 2009-11-02 Last updated: 2022-02-25Bibliographically approved
In thesis
1. Asymmetric transfer hydrogenation of ketones: Catalyst development and mechanistic investigation
Open this publication in new window or tab >>Asymmetric transfer hydrogenation of ketones: Catalyst development and mechanistic investigation
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of ligands derived from natural amino acids for asymmetric transfer hydrogenation (ATH) of prochiral ketones is described herein. In the first part, reductions performed in alcoholic media are examined, where it is found that amino acid-derived hydroxamic acids and thioamides, respectively, are simple and versatile ligands that in combination with [RhCp*Cl2]2 efficiently catalyze this particular transformation. Selectivities up to 97% ee of the corresponding secondary alcohols are obtained, and it is furthermore observed that the two different ligand classes, albeit based on the same amino acid scaffold, give rise to products of opposite configuration.

The highly interesting enantioswitchable nature of the two abovementioned catalysts is studied in detail by mechanistic investigations. A structure/activity correlation analysis is performed, which reveals that the diverse behavior of the catalysts arise from different interactions between the ligands and the metal. Kinetic studies furthermore stress the catalyst divergence, since a difference in the rate determining step is established from initial rate measurements. In addition, rate constants are determined for each step of the overall reduction process.

In the last part, catalyst development for ATH executed in water is discussed. The applicability of hydroxamic acid ligands is further extended, and catalysts based on these compounds are found to be efficient and compatible with aqueous conditions. The structurally even simpler amino acid amide is also evaluated as a ligand, and selectivities up to 90% ee are obtained in the reduction of a number of aryl alkyl ketones. The very challenging reduction of dialkyl ketones is moreover examined in the Rh-catalyzed aqueous ATH, where a modified surfactant-resembling sulfonylated diamine is used as ligand, and the reaction is carried out in the presence of SDS-micelles. A positive effect is to some extent found on the catalyst performance upon addition of phase-transfer components, especially regarding the catalytic activity in the reduction of more hydrophobic substrates.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2011. p. 49
Keywords
Asymmetric catalysis, reduction, amino acid, rhodium, mechanistic investigation, kinetic study
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-55412 (URN)978-91-7447-234-9 (ISBN)
Public defence
2011-04-29, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: In press.Available from: 2011-04-07 Created: 2011-03-14 Last updated: 2022-02-24Bibliographically approved

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Ahlford, KatrinAdolfsson, Hans

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