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Selective transfer hydrogenations: Catalyst development and mechanistic investigations
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
2008 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: Institutionen för organisk kemi , 2008. , s. 68
Nyckelord [en]
asymmetric catalysis, transfer hydrogenation, transition metal, amino acids, amino alcohols
Nationell ämneskategori
Organisk kemi
Forskningsämne
organisk kemi
Identifikatorer
URN: urn:nbn:se:su:diva-8300ISBN: 978-91-7155-768-1 (tryckt)OAI: oai:DiVA.org:su-8300DiVA, id: diva2:200026
Disputation
2008-12-05, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Opponent
Handledare
Tillgänglig från: 2008-11-13 Skapad: 2008-11-13Bibliografiskt granskad
Delarbeten
1. Ruthenium-Catalyzed Enantioselective Reduction of Electron-Rich Aryl Alkyl Ketones
Öppna denna publikation i ny flik eller fönster >>Ruthenium-Catalyzed Enantioselective Reduction of Electron-Rich Aryl Alkyl Ketones
2006 Ingår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, Vol. 348, nr 10-11, s. 1277-1282Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:su:diva-25589 (URN)
Anmärkning
Part of urn:nbn:se:su:diva-8300Tillgänglig från: 2008-11-13 Skapad: 2008-11-13Bibliografiskt granskad
2. The Importance of Alkali Cations in the [{RuCl2(p-cymene)}2]-Pseudo-dipeptide-Catalyzed Enantioselective Transfer Hydrogenation of Ketones
Öppna denna publikation i ny flik eller fönster >>The Importance of Alkali Cations in the [{RuCl2(p-cymene)}2]-Pseudo-dipeptide-Catalyzed Enantioselective Transfer Hydrogenation of Ketones
Visa övriga...
2006 Ingår i: Chemistry - A European Journal, ISSN 0947-6539, Vol. 12, nr 12, s. 3218-3225Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:su:diva-25590 (URN)
Anmärkning
Part of urn:nbn:se:su:diva-8300Tillgänglig från: 2008-11-13 Skapad: 2008-11-13Bibliografiskt granskad
3. Mechanistic Investigation on the Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Pseudo-Dipeptides Ruthenium complexes
Öppna denna publikation i ny flik eller fönster >>Mechanistic Investigation on the Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Pseudo-Dipeptides Ruthenium complexes
2009 (Engelska)Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, nr 23, s. 5709-5718Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Lithium-powered: A kinetic investigation into the asymmetric transfer hydrogenation of non-activated aryl alkyl ketones, catalyzed by N-Boc-protected -amino acid hydroxyamide ruthenium–arene complexes, has revealed that the reactions proceed through an unprecedented bimetallic outer-sphere mechanism. Under optimized conditions, these catalysts provide access to secondary alcohols in high yields and with excellent enantioselectivities (>99 % ee).

The combination of N-Boc-protected -amino acid hydroxyamides (pseudo-dipeptides) and [{Ru(p-cymene)Cl2}2] resulted in the formation of superior catalysts for the asymmetric transfer hydrogenation (ATH) of non-activated aryl alkyl ketones in propan-2-ol. The overall kinetics of the ATH of acetophenone to form 1-phenylethanol in the presence of ruthenium pseudo-dipeptide catalysts were studied, and the individual rate constants for the processes were determined. Addition of lithium chloride to the reaction mixtures had a strong influence on the rates and selectivities of the processes. Kinetic isotope effects (KIEs) for the reduction were determined and the results clearly show that the hydride transfer is rate-determining, whereas no KIEs were detected for the proton transfer. From these observations a novel bimetallic outer-sphere-type mechanism for these ATH process is proposed, in which the bifunctional catalysts mediate the transfer of a hydride and an alkali metal ion between the hydrogen donor and the substrate. Furthermore, the use of a mixture of propan-2-ol and THF (1:1) proved to enhance the rates of the ATH reactions. A series of aryl alkyl ketones were reduced under these conditions in the presence of 0.5 mol % of catalyst, and the corresponding secondary alcohols were formed in high yields and with excellent enantioselectivities (>99 % ee) in short reaction times.

Ort, förlag, år, upplaga, sidor
John Wiley & Sons, 2009
Nyckelord
amino acids;asymmetric catalysis;kinetics;reaction mechanisms;ruthenium;transfer hydrogenation
Nationell ämneskategori
Organisk kemi
Identifikatorer
urn:nbn:se:su:diva-25591 (URN)10.1002/chem.200802496 (DOI)000267037800013 ()
Anmärkning
Part of urn:nbn:se:su:diva-8300Tillgänglig från: 2008-11-13 Skapad: 2008-11-13 Senast uppdaterad: 2022-02-25Bibliografiskt granskad
4. Rhodium-Catalyzed Asymmetric Transfer Hydrogenation of Aryl Alkyl Ketones Employing Ligands Derived from Amino Acids
Öppna denna publikation i ny flik eller fönster >>Rhodium-Catalyzed Asymmetric Transfer Hydrogenation of Aryl Alkyl Ketones Employing Ligands Derived from Amino Acids
2007 Ingår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, Vol. 349, nr 17-18, s. 2556-2562Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:su:diva-25592 (URN)000251737500005 ()
Anmärkning
Part of urn:nbn:se:su:diva-8300Tillgänglig från: 2008-11-13 Skapad: 2008-11-13Bibliografiskt granskad
5. In situ formation of ligand and catalyst- application in ruthenium-catalyzed enantioselective reduction of ketones
Öppna denna publikation i ny flik eller fönster >>In situ formation of ligand and catalyst- application in ruthenium-catalyzed enantioselective reduction of ketones
2005 Ingår i: Chemical communications, ISSN 1359-7345, nr 32, s. 4039-4041Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:su:diva-25593 (URN)
Anmärkning
Part of urn:nbn:se:su:diva-8300Tillgänglig från: 2008-11-13 Skapad: 2008-11-13Bibliografiskt granskad
6. A Simple and Efficient Catalytic Method for the Reduction of Ketones
Öppna denna publikation i ny flik eller fönster >>A Simple and Efficient Catalytic Method for the Reduction of Ketones
2007 (Engelska)Ingår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 349, nr 10, s. 1609-1613Artikel i tidskrift (Refereegranskat) 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 %.

Nyckelord
alkali metals, hydrogen transfer, ketones, microwave heating, reduction
Nationell ämneskategori
Organisk kemi
Forskningsämne
organisk kemi
Identifikatorer
urn:nbn:se:su:diva-25594 (URN)10.1002/adsc.200700091 (DOI)000248365300009 ()
Tillgänglig från: 2008-11-13 Skapad: 2008-11-13 Senast uppdaterad: 2022-02-25Bibliografiskt granskad

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