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Development of Palladium-Catalyzed Transformations Involving η1-Allypalladium Species
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on investigation of the structure, reactivity and isomerization reactions of η1-allylpalladium complexes, which are key intermediates in catalytic transformations. The first part of this thesis concerns the structure and reactivity of bis-allylpalladium complexes. We have studied the regioselective palladium-catalyzed coupling reaction of various dialkylsubstituted allyl chlorides with allylstannanes and benzylidenemalonitrile, affording functionalized 1,7-octadienes. We have also found that benzylidenemalonitrile can be replaced by isocyanates providing bis-allylated amides. The second part is a computational study on the η3-η1-η3 isomerization of allylpalladium complexes. The mechanism of the isomerization was studied by DFT. It was found that the isomerization involves tetra-coordinated η1-allylpalladium intermediates. Alkyl substitution of the metalated carbon leads to destabilization of the η1-allylpalladium intermediate, which increases the activation energy of the isomerization process. The last part describes our efforts to extend the synthetic scope of mono-allylpalladium chemistry to include catalytic allylation of imine and aldehyde substrates. We have found that this reactivity can be achieved by the use of strongly coordinating tridentate ligands on palladium. The η1-allylpalladium intermediate has been observed by NMR-spectroscopy, and DFT calculations have been performed to show the feasibility of an electrophilic attack occuring on the allyl moiety.

Place, publisher, year, edition, pages
Stockholm: Institutionen för organisk kemi , 2004. , 65 p.
Keyword [en]
Palladium, Homogenous catalysis, Allylation, Electrophilic substitution, Density functional calculations
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-105ISBN: 91-7265-868-1 (print)OAI: oai:DiVA.org:su-105DiVA: diva2:189309
Public defence
2004-05-14, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2004-04-22 Created: 2004-04-22 Last updated: 2010-02-11Bibliographically approved
List of papers
1. Control of the Regioselectivity in Catalytic Transformations Involving Amphiphilic Bis-allylpalladium Intermediates: Mechanism and Synthetic Applications
Open this publication in new window or tab >>Control of the Regioselectivity in Catalytic Transformations Involving Amphiphilic Bis-allylpalladium Intermediates: Mechanism and Synthetic Applications
2001 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 66, no 5, 1686-1693 p.Article in journal (Refereed) Published
Abstract [en]

Various dialkyl-substituted allyl chloride derivatives (2d−i) undergo regioselective palladium-catalyzed coupling reactions with allylstannanes (1a,b) and benzylidenemalonitrile (4), providing functionalized 1,7-octadienes in good yield. The catalytic reaction proceeds through an unsymmetrical amphiphilic bis-allylpalladium intermediate. An introductory electrophilic attack on the terminal position of the unsubstituted allyl moiety is followed by a nucleophilic attack on the alkyl-substituted allyl ligand. A theoretical analysis was performed by applying density functional theory at the B3PW91/DZ+P level to study the substituent effects on the electrophilic attack. According to the theoretical results, the high regioselectivity can be ascribed to the electronic effects of the alkyl substituents: The terminal alkyl groups destabilize the η13-bis-allylpalladium intermediate of the reaction; in addition, the alkyl substitution increases the activation barrier for the electrophilic attack.

Identifiers
urn:nbn:se:su:diva-22711 (URN)10.1021/jo001374d (DOI)
Note
Part of urn:nbn:se:su:diva-105Available from: 2004-04-22 Created: 2004-04-22 Last updated: 2010-07-27Bibliographically approved
2. Palladium-catalyzed Tandem Bis-allylation of Isocyanates
Open this publication in new window or tab >>Palladium-catalyzed Tandem Bis-allylation of Isocyanates
2001 (English)In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 3, no 6, 909-912 p.Article in journal (Refereed) Published
Abstract [en]

A tandem bis-allylation of p-toluenesulfonyl isocyanate can be achieved by palladium-catalyzed three-component coupling reaction with allylstannanes and allyl chlorides. A high level of regioselectivity can be obtained by the appropriate choice of the allylic substituents. The reaction mechanism and the regiochemistry of the reaction can be explained by formation of an amphoteric bis-allylpalladium intermediate. This bis-allylpalladium intermediate undergoes an initial electrophilic attack on one of the allyl moieties followed by a nucleophilic attack on the other.

Identifiers
urn:nbn:se:su:diva-22712 (URN)10.1021/ol015545s (DOI)
Note
Part of urn:nbn:se:su:diva-105Available from: 2004-04-22 Created: 2004-04-22 Last updated: 2010-08-02Bibliographically approved
3. Mechanism of the η3-η1-η3 Isomerization in Allylpalladium Complexes: Solvent Coordination, Ligand, and Substituent Effects
Open this publication in new window or tab >>Mechanism of the η3-η1-η3 Isomerization in Allylpalladium Complexes: Solvent Coordination, Ligand, and Substituent Effects
2001 (English)In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 20, 5464-5471 p.Article in journal (Refereed) Published
Abstract [en]

The mechanism of the η3 → η1 → η3 isomerization of (η3-allyl)palladium complexes occurring as catalytic intermediates in important synthetic transformations has been studied by applying density functional theory at the B3PW91(DZ+P) level. It was found that under catalytic conditions, in the condensed phase, the isomerization process involves tetracoordinated (η1-allyl)palladium intermediates. In these intermediates a solvent molecule or another ancillary ligand coordinates to palladium. The stability of the (η1-allyl)palladium intermediates critically depends on the electronic effects and on the coordination ability of the solvent molecules and the ancillary ligands. The theoretical calculations indicate a dσ → π* type hyperconjugative interaction occurring in the η1-allyl moiety of the intermediary complexes. These hyperconjugative interactions influence the structure of the complexes and the activation barrier to rotation through the C1−C2 bond. Alkyl substitution of the metalated carbon leads to destabilization of the (η1-allyl)palladium complexes, which increases the activation energy of the syn/anti isomerization process. This substituent effect arises from a dual steric and electronic destabilizing interaction between the methyl substituent and the metal atom.

Identifiers
urn:nbn:se:su:diva-22713 (URN)10.1021/om010793d (DOI)
Note
Part of urn:nbn:se:su:diva-105Available from: 2004-04-22 Created: 2004-04-22 Last updated: 2010-08-02Bibliographically approved
4. Palladium-Catalyzed Electrophilic Substitution via Monoallylpalladium Intermediates
Open this publication in new window or tab >>Palladium-Catalyzed Electrophilic Substitution via Monoallylpalladium Intermediates
2003 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 42, no 31, 3656-3658 p.Article in journal (Refereed) Published
Keyword
aldehydes, allylation, electrophilic substitution, homogenous catalysis, palladium
Identifiers
urn:nbn:se:su:diva-22714 (URN)10.1002/anie.200351477 (DOI)
Note
Part of urn:nbn:se:su:diva-105Available from: 2004-04-22 Created: 2004-04-22 Last updated: 2010-08-02Bibliographically approved
5. Pincer complex catalyzed allylation of aldehyde and imine substrates via nucleophilic η1-allyl palladium intermediates: A new concept for palladium catalyzed allylic substitution reactions
Open this publication in new window or tab >>Pincer complex catalyzed allylation of aldehyde and imine substrates via nucleophilic η1-allyl palladium intermediates: A new concept for palladium catalyzed allylic substitution reactions
2004 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, Vol. 126, no 22, 7026-7033 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-23634 (URN)10.1021/ja049357j (DOI)
Note
Part of urn:nbn:se:su:diva-416Available from: 2005-03-24 Created: 2005-03-24 Last updated: 2010-02-11Bibliographically approved

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