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Effects of B(2)pin(2) and PCy3 on copper-catalyzed trifluoromethylation of substituted alkenes and alkynes with the Togni reagent
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.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2015 (English)In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 71, no 6, 922-931 p.Article in journal (Refereed) Published
Abstract [en]

The copper-catalyzed oxytrifluoromethylation of phenylacetylenes and C-H trifluoromethylation of quinones were studied. It was found that both reactions are accelerated by B(2)pin(2) and PCy3 additives. The two reactions have different substituent effects. The oxytrifluoromethylation is faster in the presence of electron-donating groups, while the C-H trifluoromethylation is faster with electron-withdrawing substituents. The Hammett plot for oxytrifluoromethylation gave a rho value of 0.76 indicating electron demand in the rate determining step of the reaction. According to the absolute value of rho the reaction probably does not proceed through a rate determining formation of a carbocation intermediate. The kinetic isotope effect measurements indicate that in C-H trifluoromethylation of quinones the cleavage of the C-H bond is not the rate determining step of the reaction.

Place, publisher, year, edition, pages
2015. Vol. 71, no 6, 922-931 p.
Keyword [en]
Catalysis, Trifluoromethylation, Substituent effects, Hammett plot, Quinones
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-115277DOI: 10.1016/j.tet.2014.12.077ISI: 000348950300003OAI: oai:DiVA.org:su-115277DiVA: diva2:799821
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

AuthorCount:4;

Available from: 2015-03-31 Created: 2015-03-18 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Novel Applications of Benziodoxole Reagents in the Synthesis of Organofluorine Compounds
Open this publication in new window or tab >>Novel Applications of Benziodoxole Reagents in the Synthesis of Organofluorine Compounds
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns method development of new synthetic routes by applying electrophilic hypervalent iodine reagents, such as trifluoromethyl-benziodoxole (Togni reagent) and fluoro-benziodoxole. The first project involved the addition of an oxygen moiety and trifluoromethyl group across double and triple bonds (both groups derived from the hypervalent iodine reagent). We observed that electron donating substituents on the aromatic ring of the substrate accelerated the oxytrifluoromethylation reaction. This transformation was further expanded to halo-trifluoromethylation reaction of a vinyl silane substrate. We also developed a copper mediated cyanotrifluoromethylation reaction, which was accelerated by PCy3 additive. This transformation allowed for the creation of two new C-C bonds in a single addition reaction. The direct C-H trifluoromethylation reaction of quinones was achived using the Togni-reagent in the presence of B2pin2 additive. The intriguing additive effects of both B2pin2 and PCy3 inspired us to examine the mechanism of these transformations.

Fluoro-benziodoxole is the fluoroiodane analogue of the trifluoromethylating Togni reagent. We developed a AgBF4 mediated geminal difluorination of styrenes using this fluoroiodine reagent. In this process one fluorine atom came from the fluoroiodane, while the other fluorine was derived from the tetrafluoroborate ion. A similar approach was applied for the 1,3-oxyfluorination and difluorination of cyclopropanes. Similarly, this fluorinative ring opening of unactivated cyclopropanes involved the introduction of an electrophilic fluorine atom from the fluoroiodane reagent and a nucleophilic one from the tetrafluoroborate ion. This reaction was extended to synthesis of 1,3-oxyfluorinated products. When alkenes reacted with the fluoro-benziodoxole reagent in the presence of palladium catalyst the iodofluorination reaction occurred.  Both the iodine and fluorine atoms were derived from the fluoroiodane reagent. The iodofluorination reaction with disubstituted and cyclic alkenes proceeded with high regio- and stereoselectivity.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2017. 61 p.
Keyword
trifluoromethylation, hypervalent iodine, Togni reagent, difluorination, iodofluorination
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-136207 (URN)978-91-7649-618-3 (ISBN)978-91-7649-619-0 (ISBN)
Public defence
2017-02-10, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2017-01-18 Created: 2016-12-01 Last updated: 2016-12-08Bibliographically approved
2. Oxidative Trifluoromethylation and other Functionalization Reactions of Alkenes and Alkynes
Open this publication in new window or tab >>Oxidative Trifluoromethylation and other Functionalization Reactions of Alkenes and Alkynes
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the use of various potent oxidants in organic synthesis. The main focus is directed at selectively introducing trifluoromethyl groups into compounds containing double or triple bonds. All reactions proceed under mild conditions and can in most cases be performed on the bench-top.

We have developed three different procedures for transformations of activated alkenes and alkynes as well as quinones. In paper I the selective introduction of a trifluoromethyl group together with an oxygen functionality to double and triple bonds is demonstrated.

Paper II is focused on the related chemoselective cyanotrifluoromethylation in which a cyano group is added instead of the oxygen functionality.

Paper III describes a new procedure for C–H trifluoromethylation of quinones. Our studies on the mechanistic aspects of the above reactions are described in Paper IV. In these studies we investigated the ligand and substituent effects in Cu-catalyzed reactions.

Paper V is focused on a conceptually new palladium-catalyzed allylic C–H acyloxylation of olefins under oxidative conditions. The procedure uses an inexpensive, safe and environmentally benign oxidant, sodium perborate, which is activated with acetic anhydride.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2014. 63 p.
Keyword
palladium, copper, transition metal, trifluoromethylation, catalysis, acetoxylation, difunctionalization, oxidation, mechanistic study, alkenes, alkynes, quinones
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-103064 (URN)978-91-7447-930-0 (ISBN)
Public defence
2014-06-05, 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: Submitted.

Available from: 2014-05-14 Created: 2014-04-30 Last updated: 2017-01-02Bibliographically approved

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