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Mild and Robust Redox-Neutral Pd/C-Catalyzed Lignol -O-4 Bond Cleavage Through a Low-Energy-Barrier Pathway
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.ORCID iD: 0000-0001-6543-7674
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
2015 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 8, no 13, 2187-2192 p.Article in journal (Refereed) Published
Abstract [en]

A Pd/C catalyzed redox neutral CO bond cleavage of 2-aryloxy-1-arylethanols has been developed. The reactions are carried out at 80 degrees C, in air, using a green solvent system to yield the aryl ketones in near quantitative yields. Addition of catalytic amounts of a hydrogen source to the reaction mixture activates the catalyst to proceed through a low energy barrier pathway. Initial studies support a transfer hydrogenolysis reaction mechanism that proceeds through an initial dehydrogenation followed by an enol adsorption to Pd/C and a reductive CO bond cleavage.

Place, publisher, year, edition, pages
2015. Vol. 8, no 13, 2187-2192 p.
Keyword [en]
heterogeneous catalysis, lignin, palladium, reaction mechanisms, transfer hydrogenolysis
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-259649DOI: 10.1002/cssc.201500117ISI: 000357619000004PubMedID: 25925736OAI: oai:DiVA.org:uu-259649DiVA: diva2:847584
Funder
Swedish Energy Agency
Available from: 2015-08-20 Created: 2015-08-10 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Palladium-catalyzed lignin valorization: Towards a lignin-based biorefinery
Open this publication in new window or tab >>Palladium-catalyzed lignin valorization: Towards a lignin-based biorefinery
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work described in this thesis focuses on the cleavage of the β-O-4′ bond, which is the most abundant interunit linkage in the lignin polymer.

In the first part, three methods based on palladium catalysis have been developed and their applicability has been verified using lignin model compounds. A transfer hydrogenolysis of the β-O-4′ bond using formic acid as a mild hydrogen donor together with a base. An aerobic oxidation of the benzylic alcohol motif in the β-O-4′ linkage to generate a key intermediate in the cleavage reaction was performed. A redox neutral cleavage of the β-O-4′ bond was accomplished in which no stoichiometric reducing or oxidizing agents were added.

In the second part of the thesis, a mechanistic study is presented. The corresponding ketone from a dehydrogenation reaction of the benzylic alcohol motif was identified to be the key intermediate. This ketone and its enol tautomer was found to be responsible for the β-O-4′ bond cleavage reaction under the employed reaction conditions.

In the final part of this thesis, the methodologies have been applied to native lignin. The depolymerization reaction was combined with organosolv pulping. This approach was successful, and together with cellulose and hemicellulose, propenyl aryls were generated in excellent yields directly from wood. In this transformation, the lignin derived molecules have been reduced by an endogenous hydrogen donor from the wood.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1310
Keyword
Lignin, Heterogeneous Catalysis, Palladium, Biomass, Depolymerization, Reduction, Oxidation, Biorefinery, Transfer Hydrogenolysis
National Category
Organic Chemistry Polymer Chemistry Wood Science
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-265315 (URN)978-91-554-9393-6 (ISBN)
Public defence
2015-12-14, B:22, Uppsala Biomedical Centre (BMC), Husargatan 3, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2015-11-23 Created: 2015-10-27 Last updated: 2016-01-13

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Galkin, Maxim V.Samec, Joseph S. M.

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