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New Efficient Ruthenium Catalysts for Racemization of Alcohols at Room Temperature
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.
2004 (English)In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1873-3581, Vol. 45, no 36, 6799-6802 p.Article in journal (Refereed) Published
Abstract [en]

5-Pentaphenylcyclopentadienyl)RuCl(CO)2 was found to catalyze efficiently the racemization of chiral alcohols such as (S)-1-phenylethanol, (S)-1-phenylpropan-2-ol, (S)-4-phenylbutan-2-ol and (S)-4-methoxy-1-phenylethanol at room temperature in the presence of a base. The catalytic activity of three other Ru(II) complexes was also investigated. The effects of halide and solvent were studied as well.

Place, publisher, year, edition, pages
2004. Vol. 45, no 36, 6799-6802 p.
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-24330DOI: 10.1016/j.tetlet.2004.07.013OAI: oai:DiVA.org:su-24330DiVA: diva2:197245
Available from: 2007-05-30 Created: 2007-05-23 Last updated: 2013-08-15Bibliographically approved
In thesis
1. Synthetic Transformations via Metal- and Enzyme-Catalyzed Dynamic Kinetic Resolution
Open this publication in new window or tab >>Synthetic Transformations via Metal- and Enzyme-Catalyzed Dynamic Kinetic Resolution
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the preparation of a new half-sandwich type ruthenium(II)- catalyst for racemization of optically active secondary alcohols and the development of a highly efficient method in combination with lipases such as Candida antarctica lipase B and Pseudomonas cepacia lipase for dynamic kinetic resolution of various functionalized alcohols under mild reaction conditions.

It was shown that the RuCl(CO)25-C5Ph5) complex can racemize optically active aliphatic and aromatic secondary alcohols at room temperature in rather short times. Different parameters, such as the nature of the catalyst, catalyst loading and solvent effect were studied. After the optimization steps, the Ru-catalyzed racemization of (S)-1-phenylethanol in the presence of Candida antarctica lipase B was also investigated. The compatibility of the metal- and enzyme-catalyzed reactions led to a highly efficient coupled catalytic system for transformation of racemic alcohols to their enantiomerically pure acetates. This protocol was applied for a wide range of secondary alcohols. It was shown that in the case of allylic alcohols the obtained enantiopure allylic acetates are useful compounds for synthesis of α-methyl carboxylic acids such as (R)-Flurbiprofen and acyloin acetates. Highly selective dynamic kinetic asymmetric transformation of 3,5-piperidine diol to deliver various 3,5-dioxygenated piperidines is also described.

Place, publisher, year, edition, pages
Stockholm: Institutionen för organisk kemi, 2007. 66 p.
Keyword
ruthenium, racemization, lipase, dynamic kinetic resolution, secondary alcohol, Candida antarctica lipase B
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-6876 (URN)978-91-7155-463-5 (ISBN)
Public defence
2007-06-20, Magnélisalen, Arrheniuslaboratoriet, Svante Arrhenius väg 12, Stockholm, 10:00
Opponent
Supervisors
Available from: 2007-05-30 Created: 2007-05-23 Last updated: 2017-10-16Bibliographically approved
2. Studies of Biomimtic Oxidations and Racemizations
Open this publication in new window or tab >>Studies of Biomimtic Oxidations and Racemizations
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with studies of ruthenium-catalyzed hydrogen transfer reactions for oxidations and racemization.

Through optimisation of the substrate-selective redox catalyst, the electron and proton transfer mediator (a benzoquinone derivative), and the oxygen-activating metal macrocycle a highly efficient biomimetic oxidation of secondary alcohols was obtained. Several alcohols were subjected to the new oxidation protocol and the corresponding ketones were isolated in high yield.

The deactivation of the oxygen-activating metal macrocycle retarded the aerobic oxidation of primary alcohols. Encapsulation of the metal macrocycle into zeolite, described in chapter 3, proved to be an efficient method to solve this problem and comparable conversion of alcohols was achieved. The immobilization of the oxygen-activating porphyrin to a surface can be an alternative approach to solve the deactivation problem. Therefore as the first step towards studies of immobilized porphyrins on a metal surface (of gold or silver), S-thioacetyl derivatized porphyrins were synthesized; two alternative syntheses are described in chapter 4.

A new and effecient ruthenium-catalyzed racemization protocol was established by proper ligand tuning. The racemization of the enantiomerically pure alcohols was increased significantly; this work is reported in chapter 5.

Place, publisher, year, edition, pages
Stockholm: Institutionen för organisk kemi, 2004. 52 p.
Keyword
oxidation of alcohols, ruthenium, porphyrin, racemization
National Category
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-71 (URN)91-7265-819-3 (ISBN)
Public defence
2004-04-01, Magnélisalen, Arrheniuslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 14:00
Opponent
Supervisors
Available from: 2004-03-11 Created: 2004-03-11 Last updated: 2013-08-15Bibliographically approved

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