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A Simple and Efficient Catalytic Method for the Reduction of Ketones
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.
2007 (English)In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 349, no 10, 1609-1613 p.Article in journal (Refereed) Published
Abstract [en]

A range of ketones was efficiently reduced in the presence of catalytic amounts of lithium isopropoxide in 2-propanol under microwave heating, with alcohol products being formed in yields up to 99 %.

Place, publisher, year, edition, pages
2007. Vol. 349, no 10, 1609-1613 p.
Keyword [en]
alkali metals, hydrogen transfer, ketones, microwave heating, reduction
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-25594DOI: 10.1002/adsc.200700091ISI: 000248365300009OAI: oai:DiVA.org:su-25594DiVA: diva2:200025
Available from: 2008-11-13 Created: 2008-11-13 Last updated: 2015-10-19Bibliographically approved
In thesis
1. Selective transfer hydrogenations: Catalyst development and mechanistic investigations
Open this publication in new window or tab >>Selective transfer hydrogenations: Catalyst development and mechanistic investigations
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

By generating a library of amino acid-based ligands, pseudo-dipeptides, and combining them with transition metals, we have created selective and efficient ruthenium and rhodium catalysts for the asymmetric transfer hydrogenation of ketones. The ruthenium-catalyzed reaction was studied in detail, and we found that alkali metals play a crucial role for the reactivity and selectivity of the reaction. Furthermore, we have performed kinetic studies on the catalytic system, and the experimental data does neither support the established inner-sphere nor the classical outer-sphere mechanism. Hence, a novel mechanism for the ruthenium-pseudo-dipeptide-catalyzed transfer hydrogenation is proposed. In this unprecedented outer-sphere mechanism, a hydride and an alkali metal ion are transferred from the donor to the ruthenium complex in the rate determining step.

In addition, the pseudo-dipeptide ligands were employed in the rhodium-catalyzed transfer hydrogenation of aryl alkyl ketones to yield the corresponding alcohols in high yields and excellent enantioselectivities (up to 98% ee). The study revealed that the alkali metals, so important in the ruthenium analogue of the reaction, do not improve the enantioselectivity of the reaction. Deuterium labeling experiments showed that the reaction follows the mono hydridic route.

Furthermore, a novel method for efficient catalyst screening has been developed. We have demonstrated that ligand synthesis, catalyst formation, and enantioselective catalysis can be performed using an in situ one-pot procedure. The efficacy of the concept was demonstrated in the enantioselective reduction of ketones. In addition to the simplification of the catalyst formation, this approach resulted in improvement of the product ee.

Finally, the development of a reduction protocol for the transfer hydrogenation of ketones to alcohols without the involvement of transition metal catalysts is described. Using microwave irradiation, a range of ketones was efficiently reduced in high yields using catalytic amounts of lithium 2-propoxide in 2-propanol.

Place, publisher, year, edition, pages
Stockholm: Institutionen för organisk kemi, 2008. 68 p.
Keyword
asymmetric catalysis, transfer hydrogenation, transition metal, amino acids, amino alcohols
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-8300 (URN)978-91-7155-768-1 (ISBN)
Public defence
2008-12-05, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Opponent
Supervisors
Available from: 2008-11-13 Created: 2008-11-13Bibliographically approved
2. Transition Metal Hydrides: Biomimetic Studies and Catalytic Applications
Open this publication in new window or tab >>Transition Metal Hydrides: Biomimetic Studies and Catalytic Applications
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, studies of the nature of different transition metal-hydride complexes are described. The first part deals with the enantioswitchable behaviour of rhodium complexes derived from amino acids, applied in asymmetric transfer hydrogenation of ketones. We found that the use of amino acid thio amide ligands resulted in the formation of the R-configured product, whereas the use of the corresponding hydroxamic acid- or hydrazide ligands selectively gave the S-alcohol.

Structure/activity investigations revealed that the stereochemical outcome of the catalytic reaction depends on the ligand mode of coordination.

In the second part, an Fe hydrogenase active site model complex with a labile amine ligand has been synthesized and studied. The aim of this study was to find a complex that efficiently catalyzes the reduction of protons to molecular hydrogen under mild conditions. We found that the amine ligand functions as a mimic of the loosely bound ligand which is part of the active site in the hydrogenase.

Further, an Fe hydrogenase active site model complex has been coupled to a photosensitizer with the aim of achieving light induced hydrogen production. The redox properties of the produced complex are such that no electron transfer from the photosensitizer part to the Fe moiety occurs.

In the last part of this thesis, the development of a protocol for the transfer hydrogenation of ketones to secondary alcohols without the involvement of transition metal catalysts is described. A variety of ketones were efficiently reduced in 2-propanol using catalytic amounts of alkali alkoxide under microwave irradiation.

Place, publisher, year, edition, pages
Stockholm: Institutionen för organisk kemi, 2007
Keyword
transition metals, catalysis, bioinorganic chemistry, hydrides
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-7187 (URN)978-91-7155-539-7 (ISBN)
Public defence
2007-12-14, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2007-11-22 Created: 2007-11-14 Last updated: 2015-10-18Bibliographically approved

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