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Self-adaptable catalysts: Importance of flexibility and applications in asymmetric catalysis
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Christina Moberg)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The topic of this thesis is the design and synthesis of biaryl-based self adaptableligands for asymmetric metal catalysis. The results discussed in papers I-III are covered, together with some unpublished results concerning substrate-adaptable catalysts. A general survey of self-adaptable catalysts is presented first.

The second chapter of this thesis starts with a survey of inversion barriers in biphenyl-based ligands and catalysts. Thereafter, the determination of barriers to conformational adaptation in dibenzoazepines and dibenzophosphepines is described. Palladium complexes with a diphosphine ligand or a diamine ligand, as well as the free diamine ligand, were studied. Entropies and enthalpies of activation were determined with variable temperature NMR spectroscopy. The mechanism of conformational change in the metal complexes was elucidated.

The third chapter describes the synthesis of semiflexible and rigid phosphinite ligands, as well as their application in rhodium-catalysed asymmetric hydrogenation. Modest enantioselectivities (up to 63% ee) were obtained. The semiflexible ligand was found to behave like the most active rigid diastereomer. The fourth chapter describes the behaviour of amine and phosphoramidite ligands in model complexes relevant to the palladium-catalysed asymmetricallylic alkylation of benchmark substrates. Diphosphoramidite and aminephosphoramiditeligands were designed and synthesised. Pd(olefin) complexesof diamine and diphosphoramidite ligands were studied, and their symmetry determined. It was found that both types of ligands are able to adapt their conformation to the substrate.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , 58 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:19
Keyword [en]
adaptable, flexible, semi-flexible, symmetry, conformational study, mechanistic study, rotation barrier, VT NMR, asymmetric catalysis, ligand design, allylic alkylation, hydrogenation, azepines, dioxaphosphepines, phosphepines, amines, phosphines, phosphoramidites, phosphinites, palladium, rhodium
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-12852ISBN: 978-91-7415-645-4 (print)OAI: oai:DiVA.org:kth-12852DiVA: diva2:319277
Public defence
2010-06-09, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100630Available from: 2010-05-21 Created: 2010-05-17 Last updated: 2010-06-30Bibliographically approved
List of papers
1. Atropoisomerism in Phosphepines and Azepines
Open this publication in new window or tab >>Atropoisomerism in Phosphepines and Azepines
2009 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 74, no 23, 9120-9125 p.Article in journal (Refereed) Published
Abstract [en]

Free energy barriers to biaryl tropoinversion in metal complexes with tropos phosphepine and azepine ligands were determined by temperature-dependent P-31 NMR inversion-transfer experiments and line shape analysis of the temperature-dependent H-1 NMR spectra, respectively. The barrier in the PdCl2 complex of the azepine ligand was found to be slightly higher than that of the corresponding free ligand. Studies of a tridentate azepine ligand Suggested that Configurational change takes place without prior decoordination from the metal.

Place, publisher, year, edition, pages
Washington DC: American Chemical Society, 2009
Keyword
atropoisomerism, phosphepines, azepines, palladium, rotation barrier, VT NMR, inversion transfer, line shape analysis
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-12847 (URN)10.1021/jo902047k (DOI)000272083700023 ()2-s2.0-72249106390 (Scopus ID)
Note
QC20100630Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved
2. Stereochemical Control of Chirally Flexible Phosphepines
Open this publication in new window or tab >>Stereochemical Control of Chirally Flexible Phosphepines
2007 (English)In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, Vol. 2007, no 1, 108-115 p.Article in journal (Refereed) Published
Abstract [en]

The barriers to interconversion of the two enantiomeric atropisomers of 6-methoxy-6,7-dihydro-5H-dibenzo[c,e]phosphepine and that of the diastereomeric forms of 6-(-)menthoxy-6,7-dihydro-3H-dibenzo[c,e]phosphepine were determined by NMR spectroscopical methods to be 19.3 and 18.5 kcalmol(-1), respectively, at 298 K. The ratio of the atropisomers was shown to depend on the group bound to phosphorus. Only complexes with two homochiral ligands bound to the each metal center were obtained upon reaction with [Rh(COD)(2)](+) BF4-. The Rh complexes catalyzed the hydrogenation of alpha-acetamidocinnamate. The major isomer of 6-(-)-menthoxy-6,7-dihydro-5H-dibenzo[c,e]phosphepine was found to exhibit higher activity but to afford a product with lower ee than its diastereomer.

Place, publisher, year, edition, pages
Weinheim: Wiley-VCH Verlag, 2007
Keyword
atropoisomerism, phosphepine, rotational barrier, Rh complex, hydrogenation
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-12850 (URN)10.1002/ejoc.200600717 (DOI)000243303000012 ()2-s2.0-33846083767 (Scopus ID)
Note
QC20100630Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved
3. Self-adaptable Catalysts: Substrate-Dependent Ligand Configuration
Open this publication in new window or tab >>Self-adaptable Catalysts: Substrate-Dependent Ligand Configuration
Show others...
2008 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 6, 1845-1855 p.Article in journal (Refereed) Published
Abstract [en]

Pd(II) allyl and Pd(0) olefin complexes containing the configurationally labile ligand 1,2-bis-[4,5dihydro-3H-dibenzo[c-e]azepino]ethane were studied as models for intermediates in Pd-catalyzed allylic alkylations. According to NMR and DFT studies, the ligand prefers C-s conformation in both eta(3)-1,3-diphenylpropenyl and eta(3)-cyclohexenyl Pd(II) complexes, whereas in Pd(0) olefin complexes it adopts different conformations in complexes derived from the two types of allyl systems in both solution and, as verified by X-ray crystallography, in the solid state. These results demonstrate that the Pd complex is capable of adapting its structure to the reacting substrate. The different structural preferences also provide an explanation for the behavior of 1,3-diphenyl-2-propenyl acetate and 2-cyclohexenyl acetate in Pd-catalyzed allylic alkylations using pseudo-C-2 and pseudo-C-s symmetric ligands.

Place, publisher, year, edition, pages
Washington DC: American Chemical Society, 2008
Keyword
adaptable, flexible, phosphepine, azepine, Pd complex, DFT calculations, ligand design, chiral shift reagent, symmetry, X-ray chrystallography
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-12851 (URN)10.1021/ja074044k (DOI)000253100200022 ()2-s2.0-39049140882 (Scopus ID)
Note

QC20100524

Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved

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