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New Tools for Green Catalysis: Studies on a Biomimetic Hybrid Catalyst and a Novel Nanopalladium Catalyst
Stockholm University, Faculty of Science, Department of Organic Chemistry. (Jan Erling Bäckvall)
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: urn:nbn:se:su:diva-65079ISBN: 978-91-7447-418-3 (print)OAI: oai:DiVA.org:su-65079DiVA: diva2:460786
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
List of papers
1. Efficient synthesis of hybrid (hydroquinone-Schiff base)cobalt oxidation catalysts
Open this publication in new window or tab >>Efficient synthesis of hybrid (hydroquinone-Schiff base)cobalt oxidation catalysts
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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.

Keyword
Hybrid catalyst, Oxidation, ­Biomimetic oxidation, Electron transfer, Catalyst synthesis, Cross coupling
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-30437 (URN)10.1002/ejoc.200900312 (DOI)000269103600020 ()
Available from: 2009-10-14 Created: 2009-10-14 Last updated: 2017-12-12Bibliographically approved
2. Efficient reoxidation of palladium by a hybrid catalyst in aerobic palladium-catalyzed carbocyclization of enallenes
Open this publication in new window or tab >>Efficient reoxidation of palladium by a hybrid catalyst in aerobic palladium-catalyzed carbocyclization of enallenes
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2009 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 28, 6799-6801 p.Article in journal (Refereed) Published
Keyword
carbocyclization, electron transfer, hybrid catalysts, oxidation, palladium
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-28977 (URN)10.1002/chem.200900980 (DOI)000268286200004 ()
Available from: 2009-07-29 Created: 2009-07-29 Last updated: 2017-12-13Bibliographically approved
3. Efficient aerobic ruthenium-catalyzed oxidation of secondary alcohols by the use of a hybrid electron transfer catalyst
Open this publication in new window or tab >>Efficient aerobic ruthenium-catalyzed oxidation of secondary alcohols by the use of a hybrid electron transfer catalyst
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2010 (English)In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 10, 1971-1976 p.Article in journal (Refereed) Published
Abstract [en]

Biomimetic aerobic oxidation of secondary alcohols has been performed using hybrid catalyst 1 and Shvo's catalyst 2. This combination allows mild reaction conditions and low catalytic loading, due to the efficiency of intramolecular electron transfer. By this method a wide range of different alcohols have been converted into their corresponding ketones. Oxidation of benzylic as well as aliphatic, electron-rich, electron-deficient and sterically hindered alcohols could be oxidized in excellent yield and selectivity. Oxidation of (S)-1-phenyl-ethanol showed that no racemization occurred during the course of the reaction, indicating that the hydride 2b adds to the quinone much faster than it re-adds to the ketone product. The kinetic deuterium isotope effect of the oxidation was determined by the use of 1-phenylethanol (3a) and 1-deuterio-1-phenylethanol (3a-d1) in parallel and competitive manner, which gave the same isotope effect within experimental error (k(H)/k(D) approximate to 2.8). This indicates that there is no strong coordination of the substrate to the catalyst.

Keyword
Oxidation, Alcohols, Electron transfer, Hybrid catalysts, Ruthenium
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-45863 (URN)10.1002/ejoc.201000033 (DOI)000276742400017 ()
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Note
authorCount :5Available from: 2010-11-15 Created: 2010-11-15 Last updated: 2017-12-12Bibliographically approved
4. Highly dispersed palladium nanoparticles on mesocellular foam: an efficient and recyclable heterogeneous catalyst for alcohol oxidation
Open this publication in new window or tab >>Highly dispersed palladium nanoparticles on mesocellular foam: an efficient and recyclable heterogeneous catalyst for alcohol oxidation
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2012 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 39, 12202-12206 p.Article in journal (Refereed) Published
Keyword
green chemistry, heterogeneous catalysis, O–O activation, oxidation, palladium nanoparticles
National Category
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-81837 (URN)10.1002/chem.201202157 (DOI)000308879000005 ()
Funder
Knut and Alice Wallenberg Foundation
Note

AuthorCount:9;

Available from: 2012-11-01 Created: 2012-11-01 Last updated: 2017-12-07Bibliographically approved
5. Nanopalladium on Amino-Functionalized Mesocellular Foam: An Efficient Catalyst for Suzuki Reactions and Transfer Hydrogenations
Open this publication in new window or tab >>Nanopalladium on Amino-Functionalized Mesocellular Foam: An Efficient Catalyst for Suzuki Reactions and Transfer Hydrogenations
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2013 (English)In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 5, no 2, 612-618 p.Article in journal (Refereed) Published
Abstract [en]

The applications of a heterogeneous Pd0-AmP-MCF nanoparticle catalyst in Suzuki cross-coupling reactions and transfer hydrogenations of alkenes are described. The catalyst was highly efficient for both transformations, resulting in 1)coupling of a wide range of aryl halides with various boronic acids in high yields and 2)chemoselective reduction of a variety of alkenes with the use of 1-methyl-1,4-cyclohexadiene as hydrogen donor. Moreover, the catalyst can be recycled several times without any significant decrease in activity or leaching of metal into solution, making the protocol economical and environmentally friendly. In the case of the Suzuki cross-coupling, a 15-fold increase in reaction rate was observed if the reaction was performed under microwave irradiation compared to conventional heating in an oil bath.

Keyword
cross-coupling, heterogeneous catalysis, hydrogenation, nanoparticles, palladium
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-88678 (URN)10.1002/cctc.201200247 (DOI)000314239000029 ()
Funder
EU, European Research Council, 247014Knut and Alice Wallenberg Foundation
Note

AuthorCount:5;

Available from: 2013-03-26 Created: 2013-03-25 Last updated: 2017-12-06Bibliographically approved

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