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Iridium-Catalyzed Asymmetric Hydrogenation yielding Chiral Diarylmethines with Weakly Coordinating or Noncoordinating Substituents
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry. (PGA)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry. (PGA)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry. (PGA)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. (PGA)
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2009 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 25, 8855-8860 p.Article in journal (Refereed) Published
Abstract [en]

Diarylimethine-containing stereocenters are present in pharmaceuticals   and natural products, making the synthetic methods that form these   chiral centers are important in industry. We have applied iridium   complexes with novel N,P-chelating ligands to the asymmetric  hydrogenation of trisubstituted olefins, forming diarylmethine chiral   centers in high conversions and excellent enantioselectivities (up to   99% ee) for a broad range of substrates. Our results support the hypothesis that steric hindrance in one specific area of the catalyst   is playing a key role in stereoselection, as the hydrogenation of   substrates differing little at the prochiral carbon occurred with high enantioselectivity. As a result, excellent stereodiscrimination was obtained even when the prochiral carbon bore, for example, phenyl and p-tolyl groups.

Place, publisher, year, edition, pages
2009. Vol. 131, no 25, 8855-8860 p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-99807DOI: 10.1021/ja9013375ISI: 000267631000039PubMedID: 19552449OAI: oai:DiVA.org:uu-99807DiVA: diva2:208778
Available from: 2009-03-20 Created: 2009-03-20 Last updated: 2011-03-31Bibliographically approved
In thesis
1. Chemo- and Enantioselective Hydrogenations: The Struggle of Expanding the Substrate Scope of Iridium Catalyzed Asymmetric Hydrogenations of Olefins
Open this publication in new window or tab >>Chemo- and Enantioselective Hydrogenations: The Struggle of Expanding the Substrate Scope of Iridium Catalyzed Asymmetric Hydrogenations of Olefins
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The asymmetric hydrogenation of olefins is a facile and popular method of reaching chiral products. Whereas ruthenium- and rhodium-catalyzed asymmetric hydrogenations have a long history, the use of iridium in this area is new but fast-growing. Since the first chiral N,P-ligated iridium catalyst was created in the late 1990s, the growing pool of N,P ligands has filled up rapidly, but most have been tested with a limited range of standard olefins. To extract the full potential of these complexes, new methods using substrates having many possible applications must be developed. This thesis focuses on the iridium-catalyzed asymmetric hydrogenation of three different new substrate classes to yield very high conversions and enantiomeric excesses (ee's). As the use of fluorine has recently become common in many different fields of chemistry, the asymmetric reduction of fluoroolefins to reach chiral products having fluorine at the stereogenic centers is highly interesting. We studied this reaction and eventually obtained very high ee values and lower degree of defluorination (Paper I and Paper II). The hydrogenations of trifluoromethylated olefins to reach products useful in applications reaching from pharmaceuticals to additives in liquid crystal displays (LCDs) were also challenging, but fruitful (Paper III). As asymmetric hydrogenation usually demands differences in the substituents of the double bond, the highly selective reduction of 1,1-diaryl olefins having similar aryls give a new perspective on the broad scope of substrates that N,P-ligated iridium complexes can reduce selectively (paper IV).

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 624
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-99808 (URN)978-91-554-7471-3 (ISBN)
Public defence
2009-05-16, BMC, C2:301, Husargatan 3, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2009-04-24 Created: 2009-03-20 Last updated: 2010-03-04Bibliographically approved
2. Synthesis and Evaluation of N,P-Chelating Ligands in Asymmetric Transition-Metal-Catalyzed Reactions: Ir-Catalyzed Asymmetric Hydrogenation and Pd-Catalyzed Asymmetric Intermolecular Heck Reaction
Open this publication in new window or tab >>Synthesis and Evaluation of N,P-Chelating Ligands in Asymmetric Transition-Metal-Catalyzed Reactions: Ir-Catalyzed Asymmetric Hydrogenation and Pd-Catalyzed Asymmetric Intermolecular Heck Reaction
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes synthesis of new chiral N,P ligands and their evaluation in two types of asymmetric transition-metal catalyzed reactions.

The first part of the thesis describes studies in iridium-catalyzed asymmetric hydrogenation. A new class of chiral N,P ligands, imidazole-phosphines, was synthesized and evaluated in the Ir-catalyzed asymmetric hydrogenation of olefins (Paper I). The new ligands proved to be highly efficient and enantioselective in the reaction. Because the substrate scope of Ir-catalyzed asymmetric hydrogenation is still limited to certain types of test substrates, new substrate classes with importance in medicinal and materials chemistry were investigated. Vinyl fluorides were efficiently hydrogenated to fluorine-containing chiral centers by the iridium catalysts with imidazole-phosphine ligands (Paper I). To obtain CF3-bearing chiral centers, we hydrogenated CF3-substituted olefins (Paper II). Ir-catalyzed asymmetric  hydrogenation was highly enantioselective for the functionalized CF3-substituted olefins and the resulting chiral products can be valuable in design of materials such as LCD screens. Ir-catalyzed asymmetric hydrogenation was also evaluated as a route to diarylmethine chiral centers (Paper III). A wide range of new chiral compounds possessing a diarylmethine chiral center was obtained.

The second part of the thesis deals with asymmetric intermolecular Heck reaction utilizing N,P ligands. The N,P ligand class of thiazole-phosphines was evaluated in the Heck reaction (Paper IV) and gave high enantioselectivity. Further, the intermolecular Heck reaction was examined using computational and experimental studies (Paper V). This study led to a better understanding of the enantioselectivity in the reaction.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 74 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 681
Keyword
Asymmetric hydrogenation, Heck reaction, N, P ligand, Iridium, Palladium, Asymmetric catalysis, Alkenes, Fluorine, Diarylmethine stereocenters
National Category
Chemical Sciences
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-108940 (URN)978-91-554-7632-8 (ISBN)
Public defence
2009-11-26, sal B41, BMC, Husargatan 3, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2009-11-05 Created: 2009-10-05 Last updated: 2009-11-05Bibliographically approved

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Bergquist, JonasAndersson, Pher G

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