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Transition metal-catalyzed allylic and vinylic functionalization: Method development and mechanistic investigations
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of small molecule building blocks in, for example, pharmaceutical research and new material development, creates a need for new and improved organic synthesis methods. The use of transition metals as mediators and catalysts opens up new reaction pathways that have made the synthesis of completely new compounds possible as well as greatly improved the synthetic routes to known compounds.

Herein, the development of new metal-mediated and catalyzed reactions for construction of vinylic and allylic carbon-carbon and carbon-heteroatom bonds is described.  The use of iodonium salts as coupling partners in Pd-catalyzed Heck type reactions with alkenes is shown to improve the current substrate scope. Results from a mechanistic study indicate that the reaction proceeds via high oxidation state palladium intermediates.

The use of IIII reagents is also believed to facilitate a PdII/PdIV catalytic cycle in allylic silylation of alkenes using (SiMe3)2, which, to the best of our knowledge, is the first method developed for metal-catalyzed allylic C-H silylation.

The same silyl-source, (SiMe3)2, has previously been used in a Pd-catalyzed allylic substitution reaction in which allylic silanes are formed from allylic alcohols. A detailed mechanistic investigation of this reaction is described in which by-products as well as intermediates, including the resting state of the catalyst, are identified using 1H, 11B, 19F and 29Si NMR spectroscopy. Kinetic experiments are performed that give information about the turn-over limiting step and the mechanism of the analogous borylation using B2pin2 is also investigated. Insights from this study further made it possible to improve the stereoselectivity of this reaction.

Additionally, a new method for Cu-mediated trifluoromethylation of allylic halides is presented in which linear products are formed exclusively from both linear and branched allylic substrates at room temperature.  Identification of allylic fluorides as by-products during the reaction also led to the development of a similar Cu-mediated reaction for the fluorination of allylic halides.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm Univeristy , 2013. , 70 p.
Keyword [en]
palladium, copper, catalysis, Heck reaction, C-H functionalization, allylic substitution, silylation, borylation, trifluoromethylation, fluorination, mechanistic study, transition metal, alkene, allylic silane, allylic boronate, allylic fluoride
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-89524ISBN: 978-91-7447-668-2 (print)OAI: oai:DiVA.org:su-89524DiVA: diva2:618703
Public defence
2013-06-14, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Available from: 2013-05-16 Created: 2013-04-29 Last updated: 2014-03-17Bibliographically approved
List of papers
1. Pincer complex-catalyzed redox coupling of alkenes with iodonium salts via presumed palladium(IV) intermediates
Open this publication in new window or tab >>Pincer complex-catalyzed redox coupling of alkenes with iodonium salts via presumed palladium(IV) intermediates
2009 (English)In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 11, no 13, 2852-2854 p.Article in journal (Refereed) Published
Abstract [en]

Palladium pincer complexes directly catalyze the redox coupling reactions of functionalized alkenes and iodonium salts. The catalytic process, which is suitable for mild catalytic functionalization of allylic acetates and electron-rich alkenes, probably occurs through Pd(IV) intermediates. Due to the strong metal−ligand interactions, the oxidation of phosphine and amine ligands of the pincer complexes can be avoided in the presented reactions.

Place, publisher, year, edition, pages
American Chemical Society, 2009
National Category
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-29393 (URN)10.1021/ol9010739 (DOI)000267400100035 ()
Available from: 2009-08-26 Created: 2009-08-26 Last updated: 2013-05-02Bibliographically approved
2. Palladium-Catalyzed Oxidative Allylic C-H Silylation
Open this publication in new window or tab >>Palladium-Catalyzed Oxidative Allylic C-H Silylation
2011 (English)In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 13, no 7, 1888-1891 p.Article in journal (Refereed) Published
Abstract [en]

Palladium-catalyzed allylic C−H silylation was performed with use of hexamethyldisilane as the silyl source. These C−H functionalization reactions occur only in the presence of hypervalent iodine reagents or other strong oxidants and proceed with excellent regioselectivity, providing the linear allylic isomer of the allylsilane products. In demonstrating the first oxidative allylic C−H silylation of alkenes, this study marks an important advance for the catalytic C−H functionalization method.

National Category
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-57796 (URN)10.1021/ol200445b (DOI)000288691600081 ()
Funder
Swedish Research Council
Available from: 2011-05-24 Created: 2011-05-19 Last updated: 2017-12-11Bibliographically approved
3. Mechanistic Investigation of the Palladium-Catalyzed Synthesis of Allylic Silanes and Boronates from Allylic Alcohols
Open this publication in new window or tab >>Mechanistic Investigation of the Palladium-Catalyzed Synthesis of Allylic Silanes and Boronates from Allylic Alcohols
2013 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 1, 443-455 p.Article in journal (Refereed) Published
Abstract [en]

The mechanism of the palladium-catalyzed synthesis of allylic silanes and boronates from allylic alcohols was investigated. H-1, Si-29, F-19, and B-11 NMR spectroscopy was used to reveal key intermediates and byproducts of the silylation reaction. The tetrafluoroborate counterion of the palladium catalyst is proposed to play an important role in both catalyst activation as well as the transmetalation step. We propose that BF3 is generated in both processes and is responsible for the activation of the substrate hydroxyl group. An (eta(3)-allyl)palladium complex has been identified as the catalyst resting state, and the formation of (eta(3)-allyl)palladium complexes directly from allylic alcohols has been studied. Kinetic analysis provides evidence that the turnover limiting step is the transmetalation, and insights into notable similarities between the borylation and the silylation reaction mechanisms enabled us to considerably improve the stereoselectivity of the borylation.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-87691 (URN)10.1021/ja309860h (DOI)000313143000067 ()
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council
Note

AuthorCount:2;

Available from: 2013-02-15 Created: 2013-02-14 Last updated: 2017-12-06Bibliographically approved
4. Regio- and Stereoselective Allylic Trifluoromethylation and Fluorination using CuCF3 and CuF Reagents
Open this publication in new window or tab >>Regio- and Stereoselective Allylic Trifluoromethylation and Fluorination using CuCF3 and CuF Reagents
2013 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 78, no 14, 7330-7336 p.Article in journal (Refereed) Published
Abstract [en]

Copper-mediated trifluoromethylation of allylic chlorides and trifluoroacetates was performed using a convenient Cu-CF3 reagent. The reaction is suitable for selective synthesis of allyl trifluoromethyl species. Mechanistic studies indicate that the reaction proceeds via a nucleophilic substitution mechanism involving allyl copper intermediates. The analogous Cu-F reagent was suitable for fluorination of allyl chlorides. Stereodefined cyclic substrates reacted regio- and stereoselectively.

National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-94192 (URN)10.1021/jo4010074 (DOI)000322210700055 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

AuthorCount:3;

Available from: 2013-09-30 Created: 2013-09-30 Last updated: 2017-12-06Bibliographically approved

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