- Stereodivergent Alkyne Hydrofluorination Using Protic Tetrafluoroborates as Tunable Reagents
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The discovery of safe, general, and practical procedures to prepare vinyl fluorides from readily available precursors remains a synthetic challenge. The metal-free hydrofluorination of alkynes constitutes an attractive though elusive strategy for their preparation. Introduced here is an inexpensive and easily handled reagent that enables the development of simple and scalable protocols for the regioselective hydrofluorination of alkynes to access both the E and Z isomers of vinyl fluorides. These reaction conditions were suitable for a diverse collection of alkynes, including several highly functionalized pharmaceutical derivatives. Computational and experimental mechanistic studies support C?F bond formation through vinyl cation intermediates, with the E- and Z-hydrofluorination products forming under kinetic and thermodynamic control, respectively.
- Geaneotes, Paul,Guo, Rui,Liu, Peng,Qi, Xiaotian,Wang, Ruihan,Wang, Yi-Ming,Xiang, Hengye
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supporting information
p. 16651 - 16660
(2020/07/16)
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- Selective Monodefluorination and Wittig Functionalization of gem-Difluoromethyl Groups to Generate Monofluoroalkenes
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Monodefluorination of gem-difluoromethyl groups is achieved using a frustrated Lewis pair (FLP) approach. Triarylphosphines and group 13 Lewis acids were surveyed as FLP components, with the combination of P(o-Tol)3 and B(C6F5)3 found to provide the best results, although the reaction is feasible with more economical components (PPh3 and BF3·OEt2). The α-fluoroalkylphosphonium products arising from the reaction were of lower activity, in regard to further fluoride abstraction, as compared to difluoride starting materials, leading to highly selective monodefluorination. The activated substrates were subject to Wittig reaction protocols to generate a variety of monofluoroalkenes in moderate to high yields.
- Mandal, Dipendu,Gupta, Richa,Young, Rowan D.
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supporting information
p. 10682 - 10686
(2018/09/10)
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- Geminal difunctionalization of α-diazo arylmethylphosphonates: Synthesis of fluorinated phosphonates
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A general approach towards diverse fluorinated phosphonates via geminal difunctionalization reactions of α-diazo arylmethylphosphonates is described. The diazo functionality (RR′CN2) is successfully converted to RR′CF2, RR′CHF, RR′CFBr or RR′CFNR′′2 groups by employing different fluorination reagents. A variety of fluorinated organophosphorus compounds were readily accessed in good to excellent yields from a common type of precursor.
- Zhou, Yujing,Zhang, Yan,Wang, Jianbo
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p. 10444 - 10453
(2016/11/18)
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- Regioselective Synthesis of Vinyl Halides, Vinyl Sulfones, and Alkynes: A Tandem Intermolecular Nucleophilic and Electrophilic Vinylation of Tosylhydrazones
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A diazo species is trapped in an intermolecular fashion by two independent ion species in tandem at the carbene center to install an electrophile and a nucleophile on the same carbon. This metal-free concept, which is unprecedented, has been illustrated by regioselective synthesis of a variety of vinyl halides, vinyl sulfones, and alkyne derivatives. (Chemical Equation Presented).
- Ojha, Devi Prasan,Prabhu, Kandikere Ramaiah
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- Acceleration of alkenyltrimethylsilane fluorination under mild conditions using ultrasound
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Alkenyltrimethylsilanes are selectively fluorodesilated to alkenyl fluoride very readily by reaction with 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2,2,2]octane bis-tetrafluoroborate (Selectfluor) and N-fluorobenzensulfonimids at room temperature under
- Ranjbar-Karimi, Reza
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experimental part
p. 768 - 769
(2011/10/08)
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- Asymmetric epoxidation of fluoroolefins by chiral dioxirane. Fluorine effect on enantioselectivity
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(Chemical Equation Presented) The asymmetric epoxidation of various fluoroolefins has been studied using chiral ketone catalyst, and up to 93% ee was achieved with fructose-derived ketone 1.
- Wong, O. Andrea,Shi, Yian
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supporting information; experimental part
p. 8377 - 8380
(2010/03/25)
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- New methods for the synthesis of fluoroolefins via the palladium catalyzed cross-coupling reaction of 1-fluorovinyl halides with organoboranes and organostannanes
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The palladium catalyzed cross-coupling reaction of 1-fluorovinyl halides with organoboranes and organostannanes provide two new facile methods to 1-substituted 1-fluoroolefins. The reactions proceed with retention of configuration in good to excellent yields.
- Chen, Chen,Wilcoxen, Keith,Huang, Charles Q.,Strack, Nathalie,McCarthy, James R.
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p. 285 - 290
(2007/10/03)
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- Photolysis of bromo- and chloro-substituted benzyl derivatives. Competition between ionic and radical pathways
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Photolysis of 1-fluoro-2-halo-1,2-diphenylethanes was studied in solutions of tetrahydrofuran, acetonitrile, and cyclohexane. The effect of free radical inhibitor and metal hydrides on products formation as well as their ratio was analyzed to elucidate the reaction pathway. In the first step homolytic C-X bond cleavage occurs from a single excited state, resulting in a biradical pair. Further reaction path depends on the type of the halogen bonded and on the solvent polarity. Electron transfer within the radical pair cage is apparently more rapid for bromides than for chlorides and is opposite as expected on the basis of the relative electronegativities of chlorine and bromine. As radicals approach each other, they fall into ionic or radical product channels. This is influenced by solvent polarity, resulting in the larger yield of ionic products in the case of acetonitrile as in the case of less polar cyclohexane.
- Kosmrlj,Sket
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p. 6890 - 6896
(2007/10/03)
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- A general and efficient route for the preparation of phenyl-substituted vinyl fluorides
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α-fluorobenzyl phosphonate (EtO)2P(O)CFHPh (2) prepared from diethyl α-hydroxyphosphonate (EtO)2P(O)CH(OH)Ph (1) and diethylaminosulfur trifluoride (DAST), reacts with bases such as butyllithium, tert- butyllithium, lithium bis(trime
- Tsai, Hou-Jen,Lin, Keh-Wen,Ting, Tzu-Hao,Burton, Donald J.
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p. 2231 - 2239
(2007/10/03)
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- Synthesis of fluorinated olefins via the palladium catalyzed cross- coupling reaction of 1-fluorovinyl halides with organoboranes
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The palladium catalyzed cross-coupling reaction of 1-fluorovinyl halides 1-4 with organoboranes proceeds under Suzuki conditions with retention on configuration to give 1-substituted 1-fluoroolefins 6-8 in good to excellent yields.
- Chen, Chen,Wilcoxen, Keith,Strack, Nathalie,McCarthy, James R.
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p. 827 - 830
(2007/10/03)
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- Fluorination of olefins with PhSeF3, PhSeF5 and PhTeF5
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Phenyselenium trifluoride, PhSeF3 (PSTF) either oxidatively difluorinates or selenofluorinates olefins, depending on their structures. The pentafluorides PhSeF5 and PhTeF5 appear to be effective difluorinating reagents, af
- Lermontov, Sergei A.,Zavorin, Sergei I.,Bakhtin, Ilya V.,Pushin, Alexei N.,Zefirov, Nikolai S.,Stang, Peter J.
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- Synthesis of phenyl substituted fluoro-olefins
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The anion derived from diethyl α-fluorobenzyl phosphonate (EtO)2P(O)-CFHPh (2) and lithium diisopropylamide in THF underwent the reaction with aldehydes and ketones to afford a moderate to good yields of phenyl substituted fluoro-olefins RR'C =
- Tsai, Hou-Jen
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p. 629 - 632
(2007/10/02)
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- CHEMISTRY OF ORGANO HALOGENIC MOLECULES. PART XCIV. THE EFFECT OF FLUORINE ON PHOTOCHEMICAL CARBON-HALOGEN BOND CLEAVAGE IN Z AND E-1-FLUORO-2-HALO-1,2-DIPHENYLETHYLENES
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Irradiation of Z and E-1-fluoro-2-halo-1,2-diphenylethylenes at λ=253.7 nm gave Z and E-2-fluoro-1,2-diphenylethylene and 1,2-diphenylacetylene.The phototransformation depended on the geometry of the molecule, the halogen atom present, and the solvent used.Introduction of fluorine on the olefinic carbon atom in the β-position to a carbon-halogen bond increased the photocleavage compared to the unsubstituted substrate, and reduced the electron transfer from the caged radical-pair to cationic intermediates.Increased solvent polarity resulted in enhanced photocleavage of the carbon-halogen bond.
- Gregorcic, A.,Zupan, M.
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p. 163 - 172
(2007/10/02)
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- PHOTOCHEMISTRY OF ORGANOHALOGENO-COMPOUNDS. PART XIX THE EFFECT OF FLUORINE ON PHOTOCHEMICAL CARBON-HALOGEN BOND CLEAVAGE
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Irradiation of 1,1-diphenyl-2-fluoro-2-haloethenes at λ = 253.7 nm gave 1,1-diphenyl-2-fluoroethene and the rearranged product trans-fluorostilbene.The phototransformation depended on the halogen present and the solvent used.Introduction of fluorine on th
- Gregorcic, A.,Zupan, M.
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p. 313 - 322
(2007/10/02)
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