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Efficient synthesis of hybrid (hydroquinone-Schiff base)cobalt oxidation catalysts
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.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Show others and affiliations
2009 (English)In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 23, 3973-3976 p.Article in journal (Refereed) Published
Abstract [en]

Hybrid catalysts A and B have recently been found to efficiently transfer electrons from a metal catalyst to molecular oxygen in biomimetic oxidations. In the present work hybrid catalysts A and B were synthesized in high yield from inexpensive starting materials. The key step is an efficient Suzuki cross-coupling, which allows the use of unprotected aldehyde 5. The new synthesis of the title hybrid catalysts is easy to carry out and can be scaled up.

Place, publisher, year, edition, pages
2009. no 23, 3973-3976 p.
Keyword [en]
Hybrid catalyst, Oxidation, ­Biomimetic oxidation, Electron transfer, Catalyst synthesis, Cross coupling
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-30437DOI: 10.1002/ejoc.200900312ISI: 000269103600020OAI: oai:DiVA.org:su-30437DiVA: diva2:272113
Available from: 2009-10-14 Created: 2009-10-14 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Biomimetic Reactions: Water Oxidation and Aerobic Oxidation
Open this publication in new window or tab >>Biomimetic Reactions: Water Oxidation and Aerobic Oxidation
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals mainly with two oxidation reactions: water oxidation and aerobic oxidation, both of which have been applied in a biomimetic fashion. In the former reaction molecular oxygen is generated whereas in the latter it was used as terminal oxidant in oxidation reactions.

The first part of this thesis describes the synthesis of different ruthenium and manganese complexes that could potentially act as catalysts for water oxidation. This part includes a discussion of the stability and reactivity of a new manganese(III) amide-type complex, that has been used as a catalyst for both epoxidation of stilbene and alcohol oxidation.

The second part of this thesis discusses the synthesis of two new hybrid catalysts consisting of hydroquinone linked cobalt(II) salophen and cobalt(II) salmdpt, which have been used as oxygen-activating catalysts in aerobic oxidation reactions. The former catalyst was applied to the Pd-catalyzed reactions such as 1,4-diacetoxylation of cyclohexadiene whereas the latter was applied to the Ru-catalyzed oxidation of secondary alcohols to ketones. Moreover, these two hybrid catalysts could be used in the Pd-catalyzed carbocyclization of enallenes. In all cases molecular oxygen was used as the stoichiometric oxidant.

 

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2009. 57 p.
Keyword
Cobalt(II) salophen, oxygen-activating catalyst, hybrid, manganese complex, epoxidation, water oxidation.
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-26259 (URN)978-91-7155-844-2 (ISBN)
Public defence
2009-04-22, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2009-04-02 Created: 2009-03-16 Last updated: 2011-12-02Bibliographically approved
2. Catalysts for Oxygen Production and Utilization: Closing the Oxygen Cycle: From Biomimetic Oxidation to Artificial Photosynthesis
Open this publication in new window or tab >>Catalysts for Oxygen Production and Utilization: Closing the Oxygen Cycle: From Biomimetic Oxidation to Artificial Photosynthesis
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the development and study of catalysts for redox reactions, which either utilize oxygen or hydrogen peroxide for the purpose of selectively oxidizing organic substrates, or produce oxygen as the necessary byproduct in the production of hydrogen by artificial photosynthesis.

The first chapter gives a general introduction about the use of environmentally friendly oxidants in the field of organic synthesis, and about the field of artificial photosynthesis. The second chapter describes a computational study of the mechanism of palladium-catalyzed oxidative carbohydroxylation of allene-substituted conjugated dienes. The proposed mechanism, which was supported by DFT calculations, involves an unusual water attack on a (π-allyl)palladium complex. The third chapter describes a computational study of the oxidation of unfunctionalized hydrocarbons, ethers and alcohols with hydrogen peroxide, catalyzed by methyltrioxorhenium (MTO). The mechanism was found to proceed via rate-limiting hydride abstraction followed by hydroxide transfer in a single concerted, but highly asynchronous, step as shown by intrinsic reaction coordinate (IRC) scans. The fourth chapter describes the use of a new hybrid (hydroquinone-Schiff base)cobalt catalyst as electron transfer mediator (ETM) in the palladium-catalyzed aerobic carbocyclization of enallenes. Covalently linking the two ETMs gave a fivefold rate increase compared to the use of separate components. The fifth chapter describes an improved synthetic route to the (hydroquinone-Schiff base)cobalt catalysts. Preparation of the key intermediate 5-(2,5-hydroxyphenyl)salicylaldehyde was improved by optimization of the key Suzuki coupling and change of protecting groups from methyl ethers to easily cleaved THP groups. The catalysts could thus be prepared in good overall yield from inexpensive starting materials.

Finally, the sixth chapter describes the preparation and study of two catalysts for water oxidation, both based on ligands containing imidazole groups, analogous to the histidine residues present in the oxygen evolving complex (OEC) and in many other metalloenzymes. The first, ruthenium-based, catalyst was found to catalyze highly efficient water oxidation induced by visible light. The second catalyst is, to the best of our knowledge, the first homogeneous manganese complex to catalyze light-driven water oxidation.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2011. 65 p.
Keyword
oxygen, catalytic oxidation, biomimetic oxidation, artificial photosynthesis, water oxidation, DFT calculations
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-56917 (URN)978-91-7447-289-9 (ISBN)
Public defence
2011-06-01, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Accepted. Paper 6: Submitted.

Available from: 2011-05-10 Created: 2011-04-29 Last updated: 2012-09-27Bibliographically approved
3. New Tools for Green Catalysis: Studies on a Biomimetic Hybrid Catalyst and a Novel Nanopalladium Catalyst
Open this publication in new window or tab >>New Tools for Green Catalysis: Studies on a Biomimetic Hybrid Catalyst and a Novel Nanopalladium Catalyst
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The first part of this thesis describes an improved synthetic route to hybrid (hydroquinone-Schiff base)cobalt catalysts. Preparation of the 5-(2,5-hydroxyphenyl)salicylaldehyde building block was improved by altering the protective groups of the hydroquinone (HQ) starting material. Both protection and deprotection could be carried out under mild conditions, resulting in high yields. By optimizing the reaction conditions of the Suzuki cross-coupling, an efficient and inexpensive synthetic route with a good overall yield was developed.

The second part describes the use of the hybrid catalyst as an electron transfer mediator (ETM) in the palladium-catalyzed aerobic carbocyclization of enallenes. By covalently linking the HQ to the cobalt Schiff-base complex the reaction proceeded at lower temperatures with a five-fold increase of the reaction rate compared to the previously reported system.

The third part describes the application of the hybrid catalyst in the biomimetic aerobic oxidation of secondary alcohols. Due to the effi­ciency of the intramolecular electron transfer, the hybrid catalyst allowed for a lower catalytic loading and milder reaction conditions compared to the previous separate-component system. Benzylic alcohols as well as aliphatic alcohols were oxidized to the corresponding ketones in excellent yield and selectivity using this methodology.

The fourth part describes the synthesis and characterization of highly dispersed palladium nanoparticles supported on aminopropyl-modified siliceous mesocellular foam. The Pd nanocatalyst showed excellent activity for the aerobic oxidation of a wide variety of alcohols under air atmosphere. Moreover, the catalyst can be recycled several times without any decrease in activity or leaching of the metal into solution.

Finally, the fifth part describes the application of the Pd nanocatalyst in transfer hydrogenations and Suzuki coupling reactions. The catalyst was found to be highly efficient for both transformations, resulting in chemoselective reduction of various alkenes as well as coupling of a variety of aryl halides with various boronic acids in excellent yields. Performing the latter reaction under microwave irradiation significantly increased the reaction rate, compared to conventional heating. However, no significant increase in reaction rate was observed for the transfer hydrogenations, under microwave heating.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2011. 74 p.
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-65079 (URN)978-91-7447-418-3 (ISBN)
Public defence
2012-01-20, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrheniusväg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Manuscript.

Available from: 2011-12-14 Created: 2011-12-01 Last updated: 2015-10-27Bibliographically approved

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