- Synthesis of fluorinated halonitrobenzenes and halonitrophenols using tetrafluoroethylene and buta-1,3-dienes as starting building blocks
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The gas-phase copyrolysis of tetrafluoroethylene with buta-1,3-diene in a flow reactor at 495–505 °C produces 3,3,4,4-tetrafluorocyclohex-1-ene, which selectively converted to 1,2-difluorobenzene or 1-chloro-2,3-difluorobenzene. The latter can be converted to 2-chloro-3,4-difluoronitrobenzene, 2,3,4-trifluoronitrobenzene, 2,3-difluoro-6-nitrophenol, or 2-chloro-3-fluoro-4-nitrophenol via nitration, fluorodechlorination, and hydrolysis reactions.
- Lipkind, M. B.,Nefedov, O. M.,Volchkov, N. V.
-
p. 2156 - 2163
(2022/01/22)
-
- Three-step regioselective synthesis of 2,3-difluorohalobenzenes using tetrafluoroethylene and buta-1,3-diene as starting building blocks
-
The gas-phase copyrolysis of tetrafluoroethylene and buta-1,3-diene in a flow tube reactor at 490–510 °C gives 3,3,4,4-tetrafluorocyclohex-1-ene, which is selectively converted to 1-bromo- or 1-chloro-2,3-difluorobenzene via intermediate steps of halogenation and dehydrohalogenation.
- Egorov, M. P.,Lipkind, M. B.,Nefedov, O. M.,Volchkov, N. V.
-
p. 925 - 932
(2021/06/07)
-
- High-throughput Synthesis and Screening of Iridium(III) Photocatalysts for the Fast and Chemoselective Dehalogenation of Aryl Bromides
-
A high-throughput optical screening method for the photocatalytic activity of a structurally diverse library of 1152 cationic iridium(III) complexes ([Ir(C^N)2(N^N)]+), corresponding to all combinations of 48 cyclometalating (C^N) and 24 ancillary (N^N) ligands, was developed. This rapid assay utilizes the colorimetric changes of a high contrast indicator dye, coumarin 6, to monitor the photo-induced electron transfer from a sacrificial amine donor to the metal complex excited state. The resulting [Ir(C^N)2(N^N)]0 can then reduce an aryl bromide to form the highly reactive aryl radical intermediate. The rate of this reaction is dictated by the molecular structure of both coordinating ligands. Relative reaction rate constants determined via this method correlated closely with 19F NMR measurements obtained using a fluorinated substrate. A simple model that expresses the rate constant as a product of a single ″strength″ parameter assigned to each of the 72 ligands can well account for the 1152 measured rate constants. The best performing complexes exhibit much higher reactivity than the benchmark photocatalysts commonly used in photoredox transformations. The catalysts were also successfully tested for their chemoselectivity. The developed screening methodology can enable generation of the large data sets needed to use modern data science to extract structure-activity relationships.
- Bernhard, Stefan,Connell, Timothy U.,Diluzio, Stephen,Kowalewski, Jakub F.,Kowalewski, Tomasz,Lewis, Jacqueline,Mdluli, Velabo,Yaron, David
-
p. 6977 - 6987
(2020/07/20)
-
- Two-step regioselective synthesis of 1,2-difluorobenzenes from chlorotrifluoroethylene and buta-l,3-dienes
-
The gas-phase copyrolysis of chlorotrifluoroethylene with buta-1,3-diene, penta-1,3-diene, or isoprene in a flow reactor at 440–480°C gave 4-chloro-4,5,5-trifluorocyclohex-1-enes. The latter treated with aqueous KOH under condition of phase-transfer catalysis were selectively converted into 1,2-difluorobenzene, 2,3-difluorotoluene, or 3,4-difluorotoluene.
- Lipkind, M. B.,Nefedov, O. M.,Volchkov, N. V.
-
-
- Ni: Vs. Pd in Suzuki-Miyaura sp2-sp2 cross-coupling: A head-to-head study in a comparable precatalyst/ligand system
-
The Suzuki-Miyaura reaction is a cornerstone method for sp2-sp2 cross-coupling in industry. There has been a concerted effort to enable the use of Ni catalysis as an alternative to Pd in order to mitigate cost and improve sustainability. Despite significant advances, ligand development for Ni-catalyzed Suzuki-Miyaura cross-coupling remains underdeveloped when compared to Pd and, as a consequence, ligands for Ni-catalyzed processes are typically taken from the Pd arena. In this study we evaluate the effect of using a similar Ni and Pd precatalyst based on a common bidentate ligand (dppf) in a head-to-head format for the most common type of biaryl couplings, establishing the practical implications of direct replacement of Pd with Ni, and identifying the potential origins of these observations in a mechanistic context.
- West, Matthew J.,Watson, Allan J. B.
-
supporting information
p. 5055 - 5059
(2019/06/03)
-
- Method for synthesizing o-difluorobenzene
-
The invention discloses a method for synthesizing o-difluorobenzene. The method comprises that 2-(trimethylsilyl)phenyl trifluoromethanesulfonate as a raw material undergoes a reaction under the action of potassium fluoride to produce benzyne, and the benzyne and fed fluorine gas directly undergo a fluorination reaction to produce o-difluorobenzene. The fluorine gas is produced by fluoro-hydrocarbon compound pyrolysis. The novel preparation method utilizes cheap and easily available raw materials, realizes a low preparation cost, is easy to operate and after-treat, develops application of a fluorohydrocarbon compound, utilizes fluorohydrocarbon pyrolysis for a fluorination reaction, is an environmentally friendly synthesis method and is suitable for industrial production. The use of the fluorohydrocarbon compound as a fluorine gas source for synthesis of the product o-difluorobenzene has not been reported and thus the method has a good application prospect.
- -
-
Paragraph 0028; 0030-0032; 0034
(2018/02/04)
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- Base-Catalyzed Aryl-B(OH)2 Protodeboronation Revisited: From Concerted Proton Transfer to Liberation of a Transient Aryl Anion
-
Pioneering studies by Kuivila, published more than 50 years ago, suggested ipso protonation of the boronate as the mechanism for base-catalyzed protodeboronation of arylboronic acids. However, the study was limited to UV spectrophotometric analysis under acidic conditions, and the aqueous association constants (Ka) were estimated. By means of NMR, stopped-flow IR, and quenched-flow techniques, the kinetics of base-catalyzed protodeboronation of 30 different arylboronic acids has now been determined at pH > 13 in aqueous dioxane at 70 °C. Included in the study are all 20 isomers of C6HnF(5-n)B(OH)2 with half-lives spanning 9 orders of magnitude: a and Sδ values, kinetic isotope effects (2H, 10B, 13C), linear free-energy relationships, and density functional theory calculations, we have identified a mechanistic regime involving unimolecular heterolysis of the boronate competing with concerted ipso protonation/C-B cleavage. The relative Lewis acidities of arylboronic acids do not correlate with their protodeboronation rates, especially when ortho substituents are present. Notably, 3,5-dinitrophenylboronic acid is orders of magnitude more stable than tetra-and pentafluorophenylboronic acids but has a similar pKa.
- Cox, Paul A.,Reid, Marc,Leach, Andrew G.,Campbell, Andrew D.,King, Edward J.,Lloyd-Jones, Guy C.
-
supporting information
p. 13156 - 13165
(2017/09/26)
-
- Catalytic Hydrodefluorination of Fluoroarenes Using Ru(IMe4)2L2H2 (IMe4 = 1,3,4,5-Tetramethylimidazol-2-ylidene; L2 = (PPh3)2, dppe, dppp, dppm) Complexes
-
The all-trans isomer of Ru(IMe4)2(PPh3)2H2 (ttt-4; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) reacts with C6F6 at 70 °C to afford the hydride fluoride complex Ru(IMe4)2(PPh3)2HF (ttt-6). At room temperature, ttt-6 reacts with Et3SiH to give a mixture of products, one of which is assigned as the silyl trihydride complex Ru(IMe4)2(PPh3)(SiEt3)H3 (8) by comparison to the isolated and structurally characterized analogue Ru(IMe4)2(PPh3)(SiPh3)H3 (9). As ttt-4 was re-formed cleanly upon heating ttt-6 with Et3SiH, it was tested in the catalytic hydrodefluorination (HDF) of C6F6 (10 mol %, 90 °C), along with 9, Ru(IMe4)2(P-P)HF (P-P = Ph2P(CH2)2PPh2 (dppe, cct-13), Ph2P(CH2)3PPh2 (dppp, cct-14), Ph2PCH2PPh2 (dppm, cct-15)), Ru(IEt2Me2)2(PPh3)2HF (cct-7; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)), and Ru(IEt2Me2)2(dppe)2HF (cct-16) for comparison. Both cct-13 and cct-14 brought about near-quantitative conversion to C6FH5 in 24 h, in comparison to ca. 50% conversion with ttt-4 in 144 h.
- Cybulski, Mateusz K.,Nicholls, Jessica E.,Lowe, John P.,Mahon, Mary F.,Whittlesey, Michael K.
-
p. 2308 - 2316
(2017/06/30)
-
- Synthesis and characterization of a novel N-F reagent derived from the ethano-Tr?ger's base: 1JFN coupling constants as a signature for the N-F bond
-
Methylation of 2,8-dimethyl-6H,12H-5,11-ethanodibenzo[b,f][1,5]-diazocine (ethano-Tr?ger's base) with methyl iodide followed by ion metathesis and fluorination with N-fluoro-2,3,4,5,6-pentachloropyridinium triflate affords a new electrophilic N-F reagent, that is more reactive than Selectfluor. 2D 19F-15N HMQC experiments provide 1JNF coupling constants which are diagnostic for the N-F functional group.
- Pereira, Raul,Wolstenhulme, Jamie,Sandford, Graham,Claridge, Timothy D. W.,Gouverneur, Véronique,Cvengro?, Ján
-
supporting information
p. 1606 - 1609
(2016/01/30)
-
- Method for preparing difluorobenzene by tubular diazotization reaction
-
A method for preparing difluorobenzene by a tubular diazotization reaction comprises the following steps: mixing a material phenylenediamine, a hydrochloric acid aqueous solution and a fluorboric acid aqueous solution and storing the mixture into a first storage tank, storing a material sodium nitrite aqueous solution into a second storage tank, respectively conveying the above materials into a mixer through a transfer pump and mixing and adding the mixture into a tubular reactor, carrying out a diazotization reaction at 0-100 DEG C for reaction residence time of 1-150 s, cooling the reaction mixture obtained after the reaction to minus 5-minus 10 DEG C, filtering to obtain wet diazonium salt and a filtrate, drying the wet diazonium salt, pyrolyzing by a pyrolysis kettle, collecting a target fraction, and distilling to obtain difluorobenzene. The method of the invention has advantages of high product yield, less ''three wastes (waste gas, waste water and industrial residue) '', simple operation and good safety, and is very suitable for industrial production.
- -
-
Paragraph 0032; 0033
(2017/05/27)
-
- Reactions of aromatic compounds with xenon difluoride
-
Reactions of substituted benzenes C6H5R (R = Me, F, Cl, Br, CF3, NO2) with xenon difluoride in the presence of boron trifluoride–diethyl ether complex in weakly acidic (1,1,1,3,3-pentafluorobutane) and weakly basic media (acetonitrile) have been studied. These reactions lead to the formation of fluorobenzene derivatives FC6H4R (isomer mixture) together with isomeric difluorobenzenes and fluorinated and non-fluorinated biphenyls. The results have been compared with previously reported data obtained in other solvents using other catalysts.
- Bardin,Adonin, N. Yu.
-
p. 1400 - 1407
(2016/11/29)
-
- Electrochemical hydrodefluorination of fluoroaromatic compounds
-
The BH4-- promoted electrochemical hydrodefluorination of fluoroaromatic compounds was reported. Using platinum as electrodes in an undivided cell, the electrolysis was carried out at constant current at room temperature under air without the need of pretreatment of the solvent. This reaction could proceed smoothly on both nonactivated monofluoroarenes and perfluoroarenes with high yields and good selectivities.
- Wu, Wen-Bin,Li, Mei-Li,Huang, Jing-Mei
-
p. 1520 - 1523
(2015/03/14)
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- Stoichiometric and catalytic C-F bond activation by the trans-dihydride NHC complex [Ru(IEt2Me2)2-(PPh3)2H2] (IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)
-
The room temperature reaction of C6F6 or C6F5H with [Ru(IEt2Me2)2(PPh3)2H2] (1; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) generated a mixture of the trans-hydride fluoride complex [Ru(IEt2Me2)2(PPh3)2HF] (2) and the bis-carbene pentafluorophenyl species [Ru(IEt2Me2)2(PPh3)(C6F5)H] (3). The formation of 3 resulted from C-H activation of C6F5H (formed from C6F6via stoichiometric hydrodefluorination), a process which could be reversed by working under 4 atm H2. Upon heating 1 with C6F5H, the bis-phosphine derivative [Ru(IEt2Me2)(PPh3)2(C6F5)H] (4) was isolated. A more efficient route to 2 involved treatment of 1 with 0.33 eq. of TREAT-HF (Et3N·3HF); excess reagent gave instead the [H2F3]- salt (5) of the known cation [Ru(IEt2Me2)2(PPh3)2H]+. Under catalytic conditions, 1 proved to be an active precursor for hydrodefluorination, converting C6F6 to a mixture of tri, di and monofluorobenzenes (TON = 37) at 363 K with 10 mol% 1 and Et3SiH as the reductant.
- Cybulski, Mateusz K.,Riddlestone, Ian M.,Mahon, Mary F.,Woodman, Timothy J.,Whittlesey, Michael K.
-
p. 19597 - 19605
(2015/11/27)
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- Rhodium catalyzed, carbon-hydrogen bond directed hydrodefluorination of fluoroarenes
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[CpRhCl(μ-Cl)]2 is reported as a highly efficient and selective precatalyst for the hydrodefluorination of perfluoroarenes using a hydrocarbon-soluble aluminum dihydride as the terminal reductant. Reactions are directed to cleave a C-F bond adjacent to an existing C-H bond with high regioselectivity (98.5-99%). A heterobimetallic complex containing an extremely rare Al-H-Rh functional group has been isolated and shown to be catalytically competent.
- Ekkert, Olga,Strudley, Sebastian D. A.,Rozenfeld, Alisa,White, Andrew J. P.,Crimmin, Mark R.
-
p. 7027 - 7030
(2015/05/19)
-
- Silver-mediated fluorination of potassium aryltrifluoroborates with Selectfluor Dedicated to Professor Andrea Vasella on the occasion of his 71st birthday
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A simple and practical procedure for the silver-mediated fluorination of aryl- and heteroaryltrifluoroborates with electrophilic fluorine from Selectfluor and LiOH·H2O is presented. The reaction procedure is simple and easy to set up, the process produces fluorinated arenes and heteroarenes in good to excellent yields and a wide range of electronically and structurally diverse substrates are tolerated.
- Dubbaka, Srinivas Reddy,Narreddula, Venkateswara Reddy,Gadde, Satyanarayana,Mathew, Thresen
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p. 9676 - 9681
(2015/01/08)
-
- Mild copper-mediated fluorination of aryl stannanes and aryl trifluoroborates
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This communication describes a mild copper-mediated fluorination of aryl stannanes and aryl trifluoroborates with N-fluoro-2,4,6-trimethylpyridinium triflate. This protocol demonstrates broad substrate scope and functional group tolerance, and does not require the use of any noble metal additives. The reaction is proposed to proceed via an arylcopper(III) fluoride intermediate.
- Ye, Yingda,Sanford, Melanie S.
-
supporting information
p. 4648 - 4651
(2013/05/09)
-
- Cobalt-xantphos-catalyzed, LiCl-mediated preparation of arylzinc reagents from aryl iodides, bromides, and chlorides
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A cobalt-Xantphos-catalyzed, LiCl-mediated system has been developed for the direct and expedient preparation of arylzinc reagents in THF from the corresponding aryl iodides, bromides, and chlorides. Owing to the use of THF as a versatile solvent, the thus-formed arylzinc reagents displayed a high degree of compatibility with a variety of conventional as well as newly emerging metal-catalyzed cross-coupling reactions.
- Jin, Meng-Yi,Yoshikai, Naohiko
-
experimental part
p. 1972 - 1978
(2011/05/19)
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- Microwave-accelerated fluorodenitrations and nitrodehalogenations: expeditious routes to labeled PET ligands and fluoropharmaceuticals
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Methods for the expeditious fluorination of arenes have been investigated, using readily available fluoride sources. An optimized procedure for microwave-accelerated fluorodenitration has been developed, giving good to excellent yields in less than 10 min, rendering it practical for use in the preparation of F18 labeled ligands for PET imaging. Application of the method in the synthesis of CNS agents is demonstrated, and a practical method for the preparation of substrates is also presented.
- LaBeaume, Paul,Placzek, Michael,Daniels, Mathew,Kendrick, Ian,Ng, Patrick,McNeel, Melissa,Afroze, Roushan,Alexander, Abigail,Thomas, Rhiannon,Kallmerten, Amy E.,Jones, Graham B.
-
experimental part
p. 1906 - 1909
(2010/09/07)
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- Palladium- or nickel-catalyzed coupling reaction of dialkoxyboranes with chloroarenes: arylation of 1,3,2-dioxaborolanes or l,3,2-dioxaborinanes
-
The borylation of electron-deficient aryl chlorides with pinacolborane proceeded in the presence of BU4NI and a catalytic amount of Pd(dba)2 / bis(2-di-tert-butylphosphinophenyl) ether. The combination of NiCl2(dppp) catalyst and Bu4NBr was also efficient for the borylation of aryl chlorides.
- Murata, Miki,Sambommatsu, Tomoko,Oda, Takeshi,Watanabe, Shinji,Masuda, Yuzuru
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experimental part
p. 213 - 218
(2010/05/03)
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- Process for the Synthesis of Highly Active Binary Metal Fluoride as a Fluorinating Agent for Aromatics
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The subject invention relates to a process for the synthesis of highly active binary metal fluoride system for the fluorination of aromatic compounds. Fluorinated aromatic compounds are valuable synthons for the chemical synthesis of pharmaceutical drugs and novel polymers. Fluorobenzene is used to control carbon content in steel manufacturing, is an intermediate for pharmaceuticals, pesticides and other organic compounds. Fluorobenzene is typically produced by the reaction of aniline and sodium nitrite in the presence of hydrogen fluoride. The present invention relates to a process for the synthesis of highly active binary metal fluoride system consists of copper (II) fluoride and aluminum (III) fluoride for the fluorination of aromatic compounds in gas phase and recycling of the reagent, in situ, using O2 and HF.
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Page/Page column 6-7
(2010/02/17)
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- The first example of the ortho-directing effect of the weakly coordinating substituent [-BF3]- in the catalytic hydrodefluorination of the pentafluorophenyltrifluoroborate anion
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The pentafluorophenyltrifluoroborate anion undergoes hydrodefluorination under the action of zinc in the presence of nickel complexes turning into the 2,3,4,5-tetrafluoroborate anion.
- Adonin, Nicolay Yu.,Prikhod'ko, Sergey A.,Bardin, Vadim V.,Parmon, Valentin N.
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experimental part
p. 260 - 262
(2010/01/18)
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- Highly reactive and regenerable fluorinating agent for oxidative fluorination of aromatics
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A newly synthesized copper aluminum fluoride of nominal composition CuAl2F8 exhibits excellent reactivity towards direct oxidative fluorination of aromatic compounds, as well as fluorodechlorination of chloroaromatics. The spent CuAl2F8 reagent can be regenerated by treatment with O2 and HF, and the fluorination process has been demonstrated to retain high conversions through 20 reaction cycles. The main advantages of this new process are safety, minimal waste, and potentially low cost.
- Janmanchi, Krishna Murthy,Dolbier Jr., William R.
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p. 349 - 354
(2013/01/03)
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- Synthesis of aryltriethoxysilanes via rhodium(I)-catalyzed cross-coupling of aryl electrophiles with triethoxysilane
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The general and efficient silylation of aryl halides has been developed utilizing triethoxysilane and a rhodium catalyst. The substrate scope is broad and includes ortho-, meta-, and para-substituted electron-rich and -deficient aryl iodides. In addition, the silylation of aryl bromides and fluoroalkanesulfonates proceeded in the presence of tetra-n-butylammonium iodide.
- Murata, Miki,Yamasaki, Hiyoruki,Ueta, Tsukasa,Nagata, Masayuki,Ishikura, Masanori,Watanabe, Shinji,Masuda, Yuzuru
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p. 4087 - 4094
(2008/01/03)
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- Oxidative fluorination of aromatic derivatives by copper (II) fluoride and silver (I) fluoride
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The subject invention provides methods of fluorinating an aromatic or chloroaromatic compound comprising combining an aromatic compound, a chloroaromatic compound, a mixture of aromatic compounds, a mixture of chloroaromatic compounds, or a mixture of chloroaromatic and aromatic compounds and a fluorinating composition comprising at least one active fluorinating agent selected from the group consisting of CuF2, AgF, HgF2, TeF4, MnF4, FeF3, and CoF2-4 and at least one support selected from the group consisting of activated carbon, ZnF2, CaF2, MgF2, AIF3, and combinations of activated carbon, ZnF2, CaF2, MgF2, or AlF3.
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-
Page/Page column 4-5
(2008/06/13)
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- Ring fluorination of non-activated aromatic compounds
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Unsubstituted aromatic compounds and aromatic compounds having one or more electron-withdrawing substituents are fluorinated, preferably in a nitromethane solvent, by contact with tri(halo- or trifluoromethyl) substituted N-fluorotriazinium salts of the following Formula I: wherein three A moieties are independently CR, where each R is independently halogen or trifluoromethyl; two A moieties are independently Z, where each Z is independently nitrogen or a quaternary nitrogen atom and Y is a counterion or group of counterions which are inert to chemical attack by fluorine. Preferably the cation of the salt is 2,4,6-trichloro-1,3,5-triazinium.
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- Electrophilic fluorination
-
N-fluorotriazinium salts, especially those of the following Formula I, are electrophilic fluorinating agents useful in fluorinating, preferably in a nitromethane solvent, carbanionic species and/or activated aromatic compounds:wherein three A moieties are independently CR, where each R is, independently, hydrogen, halogen, (primary, secondary or tertiary) amino, hydroxyl, amino, cyano, perfluorothio hydroxysulphonyl, halosulphonyl, hydrocarbyloxysulphonyl,, or a carbon-containing substituent selected from optionally substituted hydrocarbyl, hydrocarbyloxy, hydrocarbyloxycarbonyl, and hydrocarbylthio groups; two A moieties are independently Z, where each Z is independently nitrogen or a quaternary nitrogen atom and Y is a counterion or group of counterions which are inert to chemical attack by fluorine, and oligomers or polymers thereof in which adjacent triazinium moieties are linked by a common R substituent. Preferably the cation of the salt is 2,4,6-trichloro-1,3,5-triazinium.
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-
- Ring fluorination of non-activated aromatic compounds
-
Unsubstituted aromatic compounds and aromatic compounds having one or more electron-withdrawing substituents are fluorinated, preferably in a nitromethane solvent, by contact with tri(halo- or trifluoromethyl) substituted N-fluorotriazinium salts of the following Formula I: wherein three A moieties are independently CR, where each R is independently halogen or trifluoromethyl; two A moieties are independently Z, where each Z is independently nitrogen or a quaternary nitrogen atom and Y is a counterion or group of counterions which are inert to chemical attack by fluorine. Preferably the cation of the salt is 2,4,6-trichloro-1,3,5-triazinium.
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-
-
- Electrophilic fluorination
-
N-fluorotriazinium salts, especially those of the following Formula I, are electrophilic fluorinating agents useful in fluorinating, preferably in a nitromethane solvent, carbanionic species and/or activated aromatic compounds: wherein three A moieties are independently CR, where each R is, independently, hydrogen, halogen, (primary, secondary or tertiary) amino, hydroxyl, amino, cyano, perfluorothio hydroxysulfonyl, halosulfonyl, hydrocarbyloxysulfonyl, or a carbon-containing substituent selected from the group consisting of optionally substituted hydrocarbyl, hydrocarbyloxy, hydrocarbyloxycarbonyl, and hydrocarbylthio groups; two A moieties are independently Z, where each Z is independently nitrogen or a quaternary nitrogen atom and Y is a counterion or group of counterions which are inert to chemical attack by fluorine, and oligomers or polymers thereof in which adjacent triazinium moieties are linked by a common R substituent. Preferably the cation of the salt is 2,4,6-trichloro-1,3,5-triazinium.
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-
- Method of preparing fluoroaromatic compounds
-
The present invention provides a method of preparing ortho-difluorobenzene derivatives, which comprises (a) providing a mixture of cyclohexenes by reacting chlorotrifluoroethylene (CTFE) and 1,3-diene in a flow reactor and distilling the resultant, and (b) dehydrohalogenating the mixture of cyclohexenes with a phase transition catalyst in the presence of alkali metal hydroxide at temperature range of 40 to 150 °C without using any organic solvent. The distillate having low boiling point, which is obtained during distillation of the resultant, is recycled into the flow reactor. The present invention also provides a method of preparing 2-chloro-4,5-difluorobenzoic acid, which comprises (a) providing a mixture of 4-chloro-1-methyl-4,5,5-trifluorocyclohexene and 5-chloro-1-methyl-4,4,5-trifluorocyclohexene by reacting chlorotrifluoroethylene (CTFE) and isoprene and distilling the resultant, (b) dehydrohalogenating said mixture in the presence of alkali metal hydroxide and a phase transition catalyst to form 3,4-difluorotoluene, (c) reacting said 3,4-difluorotoluene with chlorine gas without using any organic solvent to form 2-chloro-4,5-difluorotoluene, (d) photo-reacting said 2-chloro-4,5-difluorotoluene with chlorine gas under a lighting mercury lamp without using any organic solvent to form 2-chloro-4,5-difluorobenzotrichloride, and (e) reacting said 2-chloro-4,5-difluorobenzotrichloride with aqueous acid solution without using any organic solvent. The present invention also provides a method of preparing 2-chloro-4,5-difluorobenzoyl chloride by reacting the 2-chloro-4,5-difluorobenzotrichloride of step (e) above with zinc oxide.
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-
-
- Preparation process of fluorine substituted aromatic compound
-
A preparation process of a fluorine substituted aromatic compound comprising reacting an alkali metal or alkali earth metal salt of an aromatic compound having a hydroxy group with an organic fluorinating agent is disclosed. As a representative fluorinating agent, a bis-dialkylamino-difluoromethane compound, for example, 2,2′-difluoro-1,3-dimethylimidazolidine, is exemplified. According to the process, an industrially useful fluorinated aromatic compound, for example, a fluorobenzene, a fluorine substituted benzophenone, a fluorine substituted diarylsulfone can be prepared with ease in economy without specific equipment.
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-
-
- Process for the preparation of fluoro compounds from the corresponding amines
-
Compounds containing a primary amino group are converted into compounds containing a fluorine atom in place of the amino group by reaction of the amino compound with hydrogen fluoride and a nitrosating reagent under the influence of ultrasound or microwaves.
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-
- Preparation of aromatic fluorides: Facile photo-induced fluorinative decomposition of arenediazonium salts and their related compounds using pyridine-nHF
-
By employing pyridine-nHF solution, the photo-induced fluorinative decomposition of arenediazonium salts (ArN2BF4) (fluoro-dediazoniation) and the related compounds, such as quinonediazides and triazenes, has been successfully carried out to produce the corresponding aromatic fluorides (ArF) in good yields. The rate in the fluoro-dediazoniation of para-substituted ArN2BF4 in pyridine-nHF solution did not obey the classical Hammett equation but conformed well to Taft's treatment [dual substituent parameter relationships (DSP)]. In the thermal fluoro-dediazoniation of ArN2BF4 the rate of reaction was significantly influenced by the substituents in the substrates. On the contrary, only a slight effect by the substituents was observed on the rate of the photo-induced fluoro-dediazoniation of ArN2BF4.
- Sawaguchi, Masanori,Fukuhara, Tsuyoshi,Yoneda, Norihiko
-
p. 127 - 133
(2007/10/03)
-
- Electrophilic fluorination of aromatics with selectfluor and trifluoromethanesulfonic acid 1
-
1-(chloromethyl)-4-fluoro-1,4-diazabicyclo[2.2.2]octane bis (tetrafluoroborate) [Selectfluor F-TEDA-BF4 (TEDA = triethylenediamine)] in the presence of trifluoromethanesulfonic acid has been found to be a very effective reagent system for the direct electrophilic fluorination of a wide variety of aromatic compounds under mild reaction conditions to the corresponding fluoroaromatics in good to excellent yields.
- Shamma, Tatyana,Buchholz, Herwig,Prakash, G. K. Surya,Olah, George A.
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p. 207 - 210
(2007/10/03)
-
- Method of preparing fluoroaromatic compounds
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The present invention provides a method of preparing ortho-difluorobenzene derivatives, which comprises (a) providing a mixture of cyclohexenes by reacting chlorotrifluoroethylene (CTFE) and 1.3-diene in a flow reactor and distilling the resultant, and (b) dehydrohalogenating the mixture of cyclohexenes with a phase transition catalyst in :he presence of alkali metal hydroxide at temperature range of 40 to 150° C. without using any organic solvent. The distillate having low boiling point, which is obtained during distillation of the resultant, is recycled into the flow reactor. The present invention also provides a method of preparing 2-chloro-4,5-difluorobenzoic acid, which comprises (a) providing a mixture of 4-chloro-1-methyl-4,5,5-trifluorocyclohexene and 5-chloro-1-methyl-4,4,5-trifluorocyclohexene by reacting chlorotrifluoroethylene (CTFE) and isoprene and distilling the resultant. (b) dehydrohalogenating said mixture in the presence of alkali metal hydroxide and a phase transition catalyst to form 3,4-difluorotoluene, to reacting said 3,4-difluorotoluene with chlorine gas without using any organic solvent to form 2-chloro-4,5-difluorotoluene, (d) photo-reacting said 2-chloro-4,5-difluorotoluene with chlorine gas under a lighting mercury lamp without using any organic solvent to form 2-chloro-4,5-difluorobenzotrichloride, and (e) reacting said 2-chloro-4,5-difluorobenzotrichloride with aqueous acid solution without using any organic solvent. The present invention also provides a method of preparing 2-chloro-4,5-difluorobenzoyl chloride by reacting the 2-chloro-4,5-difluorobenzotrichloride of step (e) above with zinc oxide.
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- Trifluoromethanesulfonic acid: A novel solvent for the electrophilic fluorination of fluoroaromatics
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Trifluoromethanesulfonic acid has been discovered to be an excellent new solvent for promoting the direct elemental fluorination of aromatics. Fluorobenzene has been successfully fluorinated to a mixture of 1,4-difluorobenzene (31%) and 1,2-difluorobenzene (7%) in CFCl3-CF3SO3H (5%), but no further improvement is observed by the addition of boron trifluoride. When the reaction is carried out in only CFCl3, the main reaction pathway is the 1,2- and 1,4-addition of fluorine to fluorobenzene forming cyclohexenes of molecular formula C6H5F5, and only a small amount of 1,4-difluorobenzene is produced. Although both 1,2- and 1,3-difluorobenzene are fluorinated to 1,2,4-trifluorobenzene in CFCl3-CF3SO3H (10%), 1,4-difluorobenzene does not undergo the same electrophilic substitution reaction.
- Coe, Paul L.,Stuart, Alison M.,Moody, David J.
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p. 1807 - 1811
(2007/10/03)
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- Fluorodesilylations of fluorophenyltrimethylsilanes with elemental fluorine: Discovery of a novel 1,2-migration of the trimethylsilyl group
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The main product in the direct elemental fluorination of 4-fluorophenyltrimethylsilane was 1,4-difluorobenzene, produced by the ipso electrophilic substitution of the trimethylsilyl group. An unexpected product, 2,5-difluorophenyltrimethylsilane, was also formed as the result of a novel 1,2-migration of the trimethylsilyl group. The same trimethylsilyl 1,2-shifts were observed in the elemental fluorinations of 2-fluoro-and 2,4-difluoro-phenyltrimethylsilanes. We propose that the carbocations formed in the rearrangements were stabilised by the mescineric effect of the α-fluorine and the greater stability of these intermediates provided the driving force for the trimethylsilyl group migrations. Although the main products in all of the fluorinations were the fluorodesilylated product, the reactions were not totally regioselective and some competing fluorodeprotonation also occurred in the reactions of 2-fluoro-and 2,4-difluoro-phenyltrimethylsilanes. The role of protic acids and Lewis acids in particular triflic acid, trifluoroacetic acid and boron trifluoride in a variety of co-solvents, respectively, was crucial in all the fluorinations we studied, experiments done in their absence gave very poor yields. Optimal conditions for fluorination of silylated substrates are described.
- Stuart, Alison M.,Coe, Paul L.,Moody, David J.
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p. 179 - 184
(2007/10/03)
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- Combined experimental and theoretical study of the protonation of polyfluorobenzenes [C6H(6-n)F(n)] (n = 0-6)
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In a recent high-pressure mass spectrometric revision to the gas-phase basicity scale (J. E. Szulejko and T. B. McMahon, J. Am. Chem. Sec. 115, 7839 (1993)), it was observed that the proton affinity for hexafluorobenzene was 24 kcal mol-1 (1 kcal = 4.184 kJ) lower than the accepted National Institute of Science and Technology (NIST) database value of 177.7 kcal mol-1 (S. G. Lias et al., J. Phys. Chem. Ref. Data 17, Suppl. 1 (1988)). Furthermore, the proton affinities for most other polyfluorobenzenes were also found to differ substantially from the NIST values. For many of the polyfluorobenzenes large protonation entropy changes were noted, which were substantially greater than then those expected from rotational symmetry number changes alone. In view of these observations, MP2/6-31G**/HF/6-31G** ab initio calculations were undertaken to investigate further the proton affinity and entropy changes with respect to the degree of fluorine substitution. The present proton affinity variations found for the polyfluorobenzenes (hexaflorobenzene excepted) can be interpreted with the aid of the ab initio results in terms of a simple additivity scheme. Each fluorine substituent para, meta, ortho or ipso to the ring protonation site will induce an incremental proton affinity change with respect to benzene of 1.5, -7.0, -1.5 and -19.0 kcal mol-1, respectively. This additivity scheme can also be used to rationalize the re-evaluated proton affinities for the polymethylbenzenes and m- and o-fluorotoluenes. The corresponding methyl increments are 7.5, 5.5, 2.5 and 1.0 kcal mol-l for para, meta, ortho and ipso protonation respectively. From the present ab initio statistical thermodynamic analysis of the various protonation entropy components, it was concluded that the low frequency vibrations are almost exclusively responsible for the large excess entropy changes observed experimentally. Ab initio calculated barriers for 1,2 proton shifts in arenium species available in the literature are concluded to be too large to allow the existence of a so-called dynamic proton. Large excess protonation entropies are noted from the literature for polymethylbenzenes, naphthalene and 1-methylnaphthalene.
- Szulejko,Hrusak,McMahon
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p. 494 - 506
(2007/10/03)
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- Facile preparation of aromatic fluorides by deaminative fluorination of aminoarenes using hydrogen fluoride combined with bases
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One-pot deaminative fluorination of aminoarenes including heteroaromatics, namely, diazotization of aminoarenes followed by in situ fluoro-dediazoniation of the corresponding diazonium ions, was successfully accomplished to produce fluoroarenes in high yields by using hydrogen fluoride combined with base solutions. The diazotization stage has been found to play the most important part in yielding fluoroarenes effectively. It was greatly influenced by the composition of the HF solution and enhanced by employing appropriate amounts of bases such as pyridine under carefully controlled conditions. The fluoro-dediazoniation stage was effectively accelerated photochemically to afford fluoroarenes having polar substituents such as hydroxyl, nitro and so on in high yields.
- Yoneda,Fukuhara
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- Catalytic isomerization of dihalobenzenes C6H3X2R in the presence of high-silica zeolites
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Catalytic isomerization of dichloro- and difluorobenzenes was carried out under conditions of a gas-phase reaction occuring in the presence of metallosilicates with the pentasiltype zeolite structure, in which several silicon atoms are isomorphically replaced by Al, Ga, or Fe atoms.A correlation between the acid properties of these zeolites and their ability to induce dihalobenzene isomerization was found. - Key words: isomerization, difluorobenzene, dichlorobenzene, zeolites.
- Lishchiner, I. I.,Plakhotnik, V. A.,Kuzmicheva, A. N.,Mortikov, E. R.
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p. 1809 - 1811
(2007/10/02)
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- KINETICS AND MECHANISM OF THE SYNTHESIS OF DIFLUOROBENZENES BY THERMAL REACTION OF DIFLUOROCARBENE WITH BUTADIENE
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Reaction of butadiene with difluorocarbene, resulting in the formation of difluorobenzenes, and its main steps have been systematically studied.The kinetics of thermal conversions of intermediately formed 2,2-difluorovinylcyclopropane and 2,2,3,3-tetrafluorovinylcyclobutane has been examined.The synthesis of difluorobenzenes has been optimized.The results obtained are used as a basis for domestic technology of production of difluorobenzenes.
- Shipilov, A. I.,Zabolot-skikh, V. F.,Nefedov, O. M.
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- Facile Preparation of Aromatic Fluorides by the Fluoro-Dediazoniation of Aromatic Diazonium Tetrafluoroborates Using HF-Pyridine Solution
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The fluoro-dediazoniation of ArN2BF4 using HF-pyridine solution has been successfully carried out either thermaly or photochemically to afford the corresponding ArF in good yields.Particularly, the photochemically induced reaction in HF-pyridine was a useful tool for the preparation of ArF having polar substituents such as halogens, OH, OMe, CF3, etc.
- Fukuhara, Tsuyoshi,Sekiguchi, Manabu,Yoneda, Norihiko
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p. 1011 - 1012
(2007/10/02)
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- Aromatization of 2+2 cycloadducts of butadienes and fluoroolefins other than tetrafluoroethylene
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The 2+2 cycloadducts of fluorinated olefins other than tetrafluoroethylene and hydrocarbon dienes also ring-expand and eliminate two moles hydrogen halide to form aromatic products.The hydrogen halide eliminated from chlorofluoroolefin adducts depends on the solid present during the aromatization.Alumina and other accelerators favor elimination of HF, while HCl evolves in the presence of inert solids such as SiC.The aromatics derived from hexafluoropropane adducts generally have the more sterically hindered regiochemistry.Alumina promotes extrusion of difluorocarbene from trifluoromethylcyclobutanes leading to fluorobenzenes rather than benzotrifluorides.Carbon accelerates these aromatizations without difluorocarbene extrusion.
- Weigert, F. J.,Davis, R. F.
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- Synthesis and aromatization of 2+2 cycloadducts of butadienes and tetrafluoroethylene
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Passing tetrafluoroethylene (TFE) and hydrocarbon dienes down a hot tube at 600 deg C with a contact time of a few seconds produces substituted fluorobenzenes.Specifically, tetrafluoroethylene and butadiene form 1,2-difluorobenzene.The aromatics produced bythe pyrolysis of TFE and methyl-substituted butadienes do not necessarily result from eliminating HF from 2+4 adducts of the starting materials.Solid-acids such as alumina or silica/alumina accelerate the ring-expansion elimination of the 2+2 cycloadducts.Aromatic products result from the preformed 2+2 cycloadducts at temperatures 200 deg C lower than the corresponding thermal reaction.The solid-acids can also influence product regiochemistry.
- Weigert, F. J.,Davis, R. F.
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- Process for the preparation of 2,6-difluoroaniline
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2,6-Difluoroaniline is prepared from 1,2,3-trichlorobenzene by partial fluorine exchange to a mixture of 2,6-difluorochlorobenzene and 2,3-difluorochlorobenzene, amination of the chloro substituents, and separation of the desired product from the isomeric 2,3-difluoroaniline. By incorporating a selective reduction into the process immediately after the partial fluorine exchange, the undesirable 2,3-difluorochlorobenzene is converted into valuable ortho-difluorobenzene and the 2,3-difluoroaniline isomer is avoided.
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- AROMATIC FLUORINE CHEMISTRY. PART 5. PREPARATION OF 2,6-DIFLUOROANILINE AND 1,2-DIFLUOROBENZENE
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The preparation of 2,6-difluoroaniline and 1,2-difluorobenzene from 1,2,3-trichlorobenzene is described.An isomeric mixture of 1-chloro-2,3-difluorobenzene and 2-chloro-1,3-difluorobenzene is obtained from KF exchange on 1,2,3-trichlorobenzene.Selective dechlorination of 1-chloro-2,3-difluorobenzene with H2 and Pd/C catalyst gives 1,2-difluorobenzene. 2,6-difluoroaniline is obtained via ammonolysis of 2-chloro-1,3-difluorobenzene.
- Pews, R. Garth,Gall, James A.
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p. 379 - 386
(2007/10/02)
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- AROMATIC FLUORINE CHEMISTRY. PART 2. PREPARATION OF CHLOROFLUOROBENZENES VIA FLUORINATION OF DICHLOROBENZENES WITH KF
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The 1,2-, 1,3-, and 1,4-chlorofluorobenzenes have been prepared via KF exchange on the corresponding dichlorobenzenes.
- Pews, R. G.,Gall, J. A.
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p. 371 - 375
(2007/10/02)
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- PREPARATION OF AROMATIC FLUORIDES VIA DIAZOTIZATION AND PHOTOCHEMICALLY INDUCED FLUORO-DEDIAZONIATION OF AROMATIC AMINES IN ANHYDROUS HYDROGEN FLUORIDE - ORGANIC BASE SOLUTIONS
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Fluoro-dediazoniation of aromatic diazonium ions, produced by the diazotization of the corresponding aromatic amines with NaNO2 in anhydrous hydrogen fluorides (AHF) - organic base solutions, was accelerated photochemically to afford Ar-F efficiently in AHF - organic base solutions in situ.
- Yoneda, Norihiko,Fukuhara, Tsuyoshi,Kikuchi, Tetsuo,Suzuki, Akira
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p. 865 - 872
(2007/10/02)
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- SUBSTITUTIVE AROMATIC FLUORINATION WITH CHLORINE PENTAFLUORIDE
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In contrast to limited substitutive fluorination of aromatics with halogen fluorides such as ClF, ClF3, BrF3 and IF5, fluorination is the predominant reaction path with ClF5.Under non-catalytic liquid phase conditions, benzene was converted to fluorobenzene (54percent yield) and chlorobenzene (37percent yield), respectively.For a heterocyclic substrate, i.e. 2,4,6-trifluoropyrimidine, sunstitutive fluorination predominated over chlorination.Three possible fluorination mechanisms are discussed.A transition complex of ClF5 with benzene is favored.Enhanced exchange fluorination of CCl4 was effected with ClF5 (CF2Cl2 >> CFCl3 > CF3Cl) as compared with ClF3 (CFCl3 >> CF2Cl2)
- Boudakian, Max M.,Hyde, Gene A.
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p. 435 - 446
(2007/10/02)
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- Ionization Energies and Entropies of Cycloalkanes. Kinetics of Free Energy Controlled Charge-Transfer Reactions.
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Enthalpies and entropies of ionization (ΔH0ion and ΔS0ion) of alkylcyclohexanes, as well as cycloheptane, cyclooctane, and trans-Decalin, have been determined by charge-transfer equilibrium measurements.Values of ΔHion, in units of kcal mol-1 (or eV), range from 229.6 (9.96) for cycloheptane to 210.7 (9.14) for trans-Decalin.A major effect of alkyl substitution is observed following substitution at a site α to a tertiary hydrogen atom (as from methylcyclohexane to 1,2-dimethylcyclohexane), or following replacement of a tertiary hydrogen atom (as from methylcyclohexane to 1,1-dimethylcyclohexane).In both cases, ΔH0 ion decreases by ca. 5 kcal mol-1.Entropies of ionization are near zero for alkylcyclohexanes but range up to 5 cal deg-1 mol-1 for nonsubstituted cycloalkanes (cyclooctane).The charge-transfer reactions involving the cycloalkanes are shown to be fast processes; i.e., the sum of the reaction efficiencies (r=k/kcollision) of the forward and reverse processes is near unity.The efficiencies of these processes appear to be determined uniquely by the overall free energy change (or equilibrium constant K).Specifically, the reaction efficiencies are defined, within a factor of 2 by the relation r=K/(1+K), which can be justified by using transition-state theory applied to the decomposition of a collision complex over surfaces lacking energy barriers.These reactions are defined as intrinsically fast processes in that they are slowed only by the overall reaction thermochemistry and not by any properties or reactions of the intermediate complex.
- Sieck, L. Wayne,Mautner, Michael
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p. 3646 - 3650
(2007/10/02)
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