| 1. |
- Ilchenko, Nadia O., et al.
(författare)
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Mild Silver-Mediated Geminal Difluorination of Styrenes Using an Air- and Moisture-Stable Fluoroiodane Reagent
- 2014
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 53:47, s. 12897-12901
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Tidskriftsartikel (refereegranskat)abstract
- An air-and moisture-stable fluoroiodane in the presence of AgBF4 is suitable for selective geminal difluorination of styrenes under mild reaction conditions. One of the C-F bonds is formed by transfer of electrophilic fluorine from the hypervalent iodine reagent, while the other one arises from the tetrafluoroborate counterion of silver. Deuterium-isotope-labelling experiments and rearrangement of methyl styrene substrates suggest that the reaction proceeds through a phenonium ion intermediate.
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| 2. |
- Ilchenko, Nadia O., et al.
(författare)
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Copper-mediated C-H trifluoromethylation of quinones
- 2013
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 49:59, s. 6614-6616
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Tidskriftsartikel (refereegranskat)abstract
- Quinones undergo copper-mediated C-H trifluoromethylation reactions using a hypervalent iodine reagent. The reactions have a broad synthetic scope involving naphtho, alkyl, chloro and methoxy quinones.
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| 3. |
- Ilchenko, Nadia O., et al.
(författare)
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Copper-Mediated Cyanotrifluoromethylation of Styrenes Using the Togni Reagent
- 2013
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 78:21, s. 11087-11091
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Tidskriftsartikel (refereegranskat)abstract
- Styrenes with an electron-deficient double bond undergo cyanotrifluoromethylation with a trifluoromethylated hypervalent iodine reagent in the presence of CuCN. The reaction proceeds under mild conditions in the presence of bulky phosphines or B(2)pin(2) additives. The process is highly regioselective and involves the consecutive formation of two C-C bonds in a single addition reaction. In the presence of a p-methoxy substituent in the styrene, oxytrifluoromethylation occurs instead of the cyanotrifluoromethylation.
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| 4. |
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| 5. |
- Ilchenko, Nadia O., et al.
(författare)
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Geminal difluorination of alpha,alpha '-disubstituted styrenes using fluoro-benziodoxole reagent. Migration aptitude of the alpha-substituents
- 2017
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Ingår i: Journal of fluorine chemistry. - : Elsevier BV. - 0022-1139 .- 1873-3328. ; 203, s. 104-109
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Tidskriftsartikel (refereegranskat)abstract
- alpha,alpha'-Disubstituted styrenes undergo a difluorination-rearrangement reaction with fluoro-benzoiodoxole reagent 1. The reaction is catalyzed by Pd(MeCN)(4)(BF4)(2) and Cu(MeCN)(4)PF6. We have studied the rearrangement of alpha,alpha'-diaryl substituted styrenes, in which the aryl groups have different electronic character. In the case of a aryl, alpha'-alkyl substituted styrenes, the aryl substituent has a higher migratory aptitude than the alkyl group. We have also extended the reactions to cycloalkyl styrenes, which underwent interesting ring contraction/expansion reactions. The regioselectivity of the migration can be explained on the basis of the formation of a phenonium intermediate.
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| 6. |
- Ilchenko, Nadia O., 1989-
(författare)
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Novel Applications of Benziodoxole Reagents in the Synthesis of Organofluorine Compounds
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 7. |
- Ilchenko, Nadia O., et al.
(författare)
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Palladium-Catalyzed lodofluorination of Alkenes Using Fluorolodoxole Reagent
- 2016
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 6:1, s. 447-450
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Tidskriftsartikel (refereegranskat)abstract
- The application of an air- and moisture-stable fluoroiodane reagent was investigated in the palladium-catalyzed iodofluorination reaction of alkenes. Both the iodo and fluoro substituents arise from the fluoroiodane reagent. In the case of certain palladium catalysts, the alkene substrates undergo allylic rearrangement prior to the iodofluorination process. The reaction is faster for electron-rich alkenes than for electron-deficient ones.
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| 8. |
- Janson, Pär G., et al.
(författare)
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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
- 2015
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Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020 .- 1464-5416. ; 71:6, s. 922-931
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Janson, Pär G., et al.
(författare)
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Electrophilic Trifluoromethylation by Copper-Catalyzed Addition of CF3-Transfer Reagents to Alkenes and Alkynes
- 2012
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 14:11, s. 2882-2885
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Tidskriftsartikel (refereegranskat)abstract
- Regio- and stereoselective Cu-catalyzed addition of the above hypervalent iodine reagent to alkynes and alkenes was achieved. In the presence of Cul, the reaction is suitable to perform trifluoromethyl-benzoyloxylation and trifluoromethyl-halogenation of alkenes and alkynes. Electron-donating substituents accelerate the process, and alkenes react faster than alkynes emphasizing the electrophilic character of the addition reaction.
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| 10. |
- Szijjarto, Csongor, et al.
(författare)
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A Versatile Long-Wavelength-Absorbing Scaffold for Eu-Based Responsive Probes
- 2013
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 19:9, s. 3099-3109
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Forskningsöversikt (refereegranskat)abstract
- Coumarin-sensitized, long-wavelength-absorbing luminescent EuIII-complexes have been synthesized and characterized. The lanthanide binding site consists of a cyclen-based chelating framework that is attached through a short linker to a 7-hydroxycoumarin, a 7-B(OH)2-coumarin, a 7-O-(4-pinacolatoboronbenzyl)-coumarin or a 7-O-(4-methoxybenzyl)-coumarin. The syntheses are straightforward, use readily available building blocks, and proceed through a small number of high-yielding steps. The sensitivity of coumarin photophysics to the 7-substituent enables modulation of the antenna-absorption properties, and thus the lanthanide excitation spectrum. Reactions of the boronate-based functionalities (cages) with H2O2 yielded the corresponding 7-hydroxycoumarin species. The same species was produced with peroxynitrite in a x106107-fold faster reaction. Both reactions resulted in the emergence of a strong approximate to 407nm excitation band, with concomitant decrease of the 366nm band of the caged probe. In aqueous solution the methoxybenzyl caged Eu-complex was quenched by ONOO. We have shown that preliminary screening of simple coumarin-based antennae through UV/Vis absorption spectroscopy is possible as the changes in absorption profile translate with good fidelity to changes in EuIII-excitation profile in the fully elaborated complex. Taken together, our results show that the 7-hydroxycoumarin antenna is a viable scaffold for the construction of turn-on and ratiometric luminescent probes.
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