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Self-adaptable Catalysts: Substrate-Dependent Ligand Configuration
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Christina Moberg)
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Christina Moberg)
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Christina Moberg)
University of Geneva. (Jérôme Lacour)
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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. Vol. 130, no 6, 1845-1855 p.
Keyword [en]
adaptable, flexible, phosphepine, azepine, Pd complex, DFT calculations, ligand design, chiral shift reagent, symmetry, X-ray chrystallography
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-12851DOI: 10.1021/ja074044kISI: 000253100200022Scopus ID: 2-s2.0-39049140882OAI: oai:DiVA.org:kth-12851DiVA: diva2:319276
Note

QC20100524

Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Self-adaptable catalysts: Importance of flexibility and applications in asymmetric catalysis
Open this publication in new window or tab >>Self-adaptable catalysts: Importance of flexibility and applications in asymmetric catalysis
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
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:nbn:se:kth:diva-12852 (URN)978-91-7415-645-4 (ISBN)
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
2. Flexibility – a tool for chirality control in asymmetric catalysis
Open this publication in new window or tab >>Flexibility – a tool for chirality control in asymmetric catalysis
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis deals with the design and synthesis of ligands for asymmetric catalysis: palladium catalyzed allylic alkylations, and rho-dium and iridium catalyzed hydrogenations of olefins.

Chirally flexible phosphepine ligands based on biphenyl were synthesized and their properties were studied. The rotation barrier for configurationally flexible phosphepines was determined by NMR spectroscopy. The ratio of the atropisomers was shown to depend on the group bound to phosphorus. Only complexes with two homochiral ligands bound to the metal center were observed upon complexation with Rh(I). It was shown that one diastereomer of the flexible ligand exhibits higher activity but lower selectivity than its diastereomer in the rhodium catalyzed hydrogenation of methyl alfa-acetamidocinnamate. These ligands were also tested in nickel catalyzed silabora-tions.

Chiral P,N-ligands with pseudo-C2 and pseudo-CS symmetry based on pyrrolidines-phospholanes or azepines-phosphepines were synthesized and studied in palladium catalyzed allylic alkylations. Semi-flexible azepine-phosphepine based ligands were prepared and their ability to adopt pseudo-C2 or pseudo-CS symmetry depending on the substrate in allylic alkylations was studied. It was shown on model allyl systems with flexible N,N-ligands that the ligand prefers CS-symmetry in compexes with anti-anti as well as syn-syn allyl moieties, but that for the latter type of complexes, according to computations, the configuration of the ligand is R*,R* in the olefin complexes formed after addition of a nucleophile to the allylic group.

A preliminary investigation of the possibilities to use a su-pramolecular approach for the preparation of P,N-ligands with pseudo-C2 and pseudo-S symmetry was made. An N,N-ligand with C2 symmetry was prepared and its activity in palladium catalyzed ally-lic alkylation was studied.

Pyridine-based P,N-ligands were tested in iridium catalyzed hy-drogenations of unfunctionalized olefins with good activities and se-lectivities. In order to attempt to improve the selectivity, ligands with a chirally flexible phosphepine fragment were prepared and applied in catalysis with promising results.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 58 p.
Series
Trita-IOK, ISSN 1100-7974 ; 2006:104
Keyword
flexibility, symmetry, dissymmetry, asymmetric catalysis, chiral ligands, pseudo-C2, pseudo-CS, conformational study, rotation barrier, pyrrolidines, phospholanes, azepines, phosphepines, supramolecular, hydrogenation, allylic alkylation, silaboration, palladium, rhodium, nickel, platinum, iridium.
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-4166 (URN)91-7178-491-8 (ISBN)
Public defence
2006-11-27, F3, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100929Available from: 2006-11-10 Created: 2006-11-10 Last updated: 2010-09-29Bibliographically approved

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