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Palladium-Catalyzed Oxidative Allylic C-H Silylation
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
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.

Place, publisher, year, edition, pages
2011. Vol. 13, no 7, 1888-1891 p.
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-57796DOI: 10.1021/ol200445bISI: 000288691600081OAI: oai:DiVA.org:su-57796DiVA: diva2:418817
Funder
Swedish Research Council
Available from: 2011-05-24 Created: 2011-05-19 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Transition metal-catalyzed allylic and vinylic functionalization: Method development and mechanistic investigations
Open this publication in new window or tab >>Transition metal-catalyzed allylic and vinylic functionalization: Method development and mechanistic investigations
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
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:nbn:se:su:diva-89524 (URN)978-91-7447-668-2 (ISBN)
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
2. Synthesis of functionalized allylic, propargylic and allenylic compounds: Selective formation of C–B, C–C, C–CF3 and C-Si bonds
Open this publication in new window or tab >>Synthesis of functionalized allylic, propargylic and allenylic compounds: Selective formation of C–B, C–C, C–CF3 and C-Si bonds
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on the development of new palladium and copper- mediated reactions for functionalization of alkenes and propargylic alcohol derivatives. The synthetic utility of the 1,2-diborylated butadienes synthesized in one of these processes has also been demonstrated.

We have developed an efficient procedure for the synthesis of allenyl boronates from propargylic carbonates and acetates. This was achieved by using a bimetallic system of palladium and copper or silver as co-catalyst. The reactions were performed under mild conditions for the synthesis of a variety of allenyl boronates. Furthermore, the synthesis of 1,2-diborylated butadienes was achieved with high diastereoselectivity from propargylic epoxides. The reactivity of the 1,2-diborylated butadienes with aldehydes was studied. It was found that the initial allylboration reaction proceeds via an allenylboronate intermediate. The allenylboronate reacts readily with an additional aldehyde to construct 2-ethynylbutane-1,4-diols with moderate to high diastereoselectivity.

We have also studied the copper-mediated trifluoromethylation of propargylic halides and trifluoroacetates. It was also shown that a transfer of chirality occurred when an enantioenriched starting material was used.

In the last part of the thesis, we have described a method for palladium-catalyzed functionalization of allylic C-H bonds for the selective synthesis of allylic silanes. The protocol only works under highly oxidative conditions which suggest a mechanism involving high oxidation state palladium intermediates.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2015. 73 p.
Keyword
palladium catalysis, allylboration, allenylboration, trifluoromethylation, silylation, copper catalysis, borylation, bimetallic catalysis
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-116863 (URN)978-91-7649-189-8 (ISBN)
Public defence
2015-06-10, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 1: Accepted.

Available from: 2015-05-19 Created: 2015-04-30 Last updated: 2015-06-29Bibliographically approved

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