- 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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Read Online
- Deaminative fluorination of anilines using potassium hydrogen fluoride and silicon tetrafluoride
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It has been found that the combination of potassium hydrogen fluoride and silicon tetrafluoride works as an efficient fluorinating agent for the deaminative fluorination of anilines. A one-pot diazotization of anilines followed by fluoro-dediazoniation proceeds with this combination of the reagents and t-butyl nitrite to afford fluoroarenes.
- Tamura, Masanori,Shibakami, Motonari,Kurosawa, Shigeru,Arimura, Takashi,Sekiya, Akira
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Read Online
- 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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Read Online
- Lewis Acid Mediated Fluorinations of Aromatic Substrates
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Direct fluorination of aromatic substrates, PhZ (Z=Cl, CHO, CH(OCH2)2, NO2, CO2CH2CH3, OH, NHCH3, OCH3, CH3) in the presence and absence of BCl3 or AlCl3, has been investigated.For PhCl and PhOH, inclusion of boron trichloride increased the percent conversion and the amount of para product.However, AlCl3 caused an increase in the ortho regioselectivity in the reaction with chlorobenzene.For PhCHO, inclusion of a Lewis acid decreased the percent conversion.In the presence of BCl3, the ethylene glycol acetal of PhCHO gave only ortho and para fluorinated derivatives with improved conversion.PhCO2CH2CH3 was unaffected by the inclusion of Lewis acid while the percentage conversion of PhNO2 increased only slightly.Fluorination of PhNHCH3, PhOCH3, or PhCH3 gave complex reaction mixtures. p-Nitroanisole gave rise to only 2-fluoro-4-nitroanisole in the presence or absence of either Lewis acid.
- Purrington, Suzanne T.,Woodard, Daniel L.
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Read Online
- Radical Decarboxylative Carbometalation of Benzoic Acids: A Solution to Aromatic Decarboxylative Fluorination
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Abundant aromatic carboxylic acids exist in great structural diversity from nature and synthesis. To date, the synthetically valuable decarboxylative functionalization of benzoic acids is realized mainly by transition-metal-catalyzed decarboxylative cross couplings. However, the high activation barrier for thermal decarboxylative carbometalation that often requires 140 °C reaction temperature limits both the substrate scope as well as the scope of suitable reactions that can sustain such conditions. Numerous reactions, for example, decarboxylative fluorination that is well developed for aliphatic carboxylic acids, are out of reach for the aromatic counterparts with current reaction chemistry. Here, we report a conceptually different approach through a low-barrier photoinduced ligand to metal charge transfer (LMCT)-enabled radical decarboxylative carbometalation strategy, which generates a putative high-valent arylcopper(III) complex, from which versatile facile reductive eliminations can occur. We demonstrate the suitability of our new approach to address previously unrealized general decarboxylative fluorination of benzoic acids.
- Xu, Peng,López-Rojas, Priscila,Ritter, Tobias
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supporting information
p. 5349 - 5354
(2021/05/05)
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- Two-step regioselective synthesis of 1,2-difluorobenzenes from chlorotrifluoroethylene and buta-l,3-dienes
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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.
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- Palladium-catalysed electrophilic aromatic C-H fluorination
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Aryl fluorides are widely used in the pharmaceutical and agrochemical industries, and recent advances have enabled their synthesis through the conversion of various functional groups. However, there is a lack of general methods for direct aromatic carbon-hydrogen (C-H) fluorination. Conventional methods require the use of either strong fluorinating reagents, which are often unselective and difficult to handle, such as elemental fluorine, or less reactive reagents that attack only the most activated arenes, which reduces the substrate scope. A method for the direct fluorination of aromatic C-H bonds could facilitate access to fluorinated derivatives of functional molecules that would otherwise be difficult to produce. For example, drug candidates with improved properties, such as increased metabolic stability or better blood-brain-barrier penetration, may become available. Here we describe an approach to catalysis and the resulting development of an undirected, palladium-catalysed method for aromatic C-H fluorination using mild electrophilic fluorinating reagents. The reaction involves a mode of catalysis that is unusual in aromatic C-H functionalization because no organometallic intermediate is formed; instead, a reactive transition-metal-fluoride electrophile is generated catalytically for the fluorination of arenes that do not otherwise react with mild fluorinating reagents. The scope and functional-group tolerance of this reaction could provide access to functional fluorinated molecules in pharmaceutical and agrochemical development that would otherwise not be readily accessible.
- Yamamoto, Kumiko,Li, Jiakun,Garber, Jeffrey A. O.,Rolfes, Julian D.,Boursalian, Gregory B.,Borghs, Jannik C.,Genicot, Christophe,Jacq, Jér?me,Van Gastel, Maurice,Neese, Frank,Ritter, Tobias
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p. 511 - 514
(2018/03/02)
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- PROCESS FOR THE PREPARATION OF ORGANIC HALIDES
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The present invention provides a halo-de-carboxylation process for the preparation of organic chlorides, organic bromides and mixtures thereof, from their corresponding carboxylic acids, using a chlorinating agent selected from trichloroisocyanuric acid (TCCA), dichloroisocyanuric acid (DCCA), or combination thereof, and a brominating agent.
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Paragraph 00146
(2017/08/01)
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- DIRECT PALLADIUM-CATALYZED AROMATIC FLUORINATION
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Provided herein are palladium complexes comprising a ligand of Formula (Α') and a ligand of Formula (B), wherein R1-R18 are as defined herein. The palladium complexes are useful in methods of fluorinating aryl and heteroaryl substrates. Further provided are compositions and kits comprising the palladium complexes.
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Paragraph 00189-00191
(2017/09/27)
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- Reactions of aromatic compounds with xenon difluoride
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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.
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p. 1400 - 1407
(2016/11/29)
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- Fluorination of aromatic compounds with xenon difluoride in the presence of boron trifluoride etherate
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Fluorination of benzene with the XeF2 - BF3?Et2O system in acetonitrile at low temperatures affords fluorobenzene in 18% yield, the conversion of benzene being 92%. The rest products are di-, tri-, tetra-, and polyphenyls with different fluorination pattern. Toluene and chloro- and bromobenzenes are fluorinated predominantly at the ortho and para positions. Fluorination of 4-nitroanisole affords 2-fluoro-4-nitroanisole in 73% yield.
- Fedorov,Zubarev,Mortikov, V. Yu.,Rodinovskaya,Shestopalov
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p. 1049 - 1052
(2016/02/09)
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- Continuous flow reactor for Balz-Schiemann reaction: A new procedure for the preparation of aromatic fluorides
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A facile and highly efficient procedure for the preparation of aromatic fluorides by Balz-Schiemann reaction via two continuous flow reactors has been set up. The continuous diazotization reactor was run at about 25 °C with residence times of 10-20 s, and the continuous fluorodediazoniation reactor was performed with a residence time of 1 min in high yields. The reaction times can be greatly reduced by increasing temperature and thereby taking advantage of superior mass and heat transfer of a continuous flow system.
- Yu, Zhi-Qun,Lv, Yan-Wen,Yu, Chuan-Ming,Su, Wei-Ke
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p. 1261 - 1263
(2013/03/14)
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- Protodecarboxylation of benzoic acids under radical conditions
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A new approach to protodecarboxylation is described that enhances the substrate scope for benzoic acids. The reaction uses oxidative radical conditions to decarboxylate a variety of acids in acetonitrile.
- Seo, Sangwon,Taylor, John B.,Greaney, Michael F.
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supporting information; experimental part
p. 8270 - 8272
(2012/09/07)
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- Direct trifluoro-methoxylation of aromatics with perfluoro-methyl- hypofluorite
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The reactivity of CF3OF (FTM) has been widely studied especially in halogenated olefinic systems and its use in pharmaceutical synthesis as a mild radical and electrophilic fluorinating agent is well documented. On the other hand, the chemical behavior of the perfluoro-methyl-hypofluorite with aromatic substrates is much less studied. Up to now few and scattered data regarding its use as electrophilic fluorinating agent of variously substituted aromatic compounds are found in the literature. In this work the reactivity of CF3OF with simple electron rich and electron poor aromatics (α,α,α-trifluoro-toluene, toluene, benzene, chloro-benzene, methoxybenzene) has been investigated. The possibility of selectively bind the trifluoro-methoxy group (via radical mechanism) or the fluorine atom (via electrophilic addition) by varying the reaction conditions has been explored. In particular we have observed that the trifluoro-methoxy free radical substitution can be the main synthetic pathway if the reaction is promoted by an independent and steady source of CF3O radical.
- Venturini, Francesco,Navarrini, Walter,Famulari, Antonino,Sansotera, Maurizio,Dardani, Patrizia,Tortelli, Vito
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experimental part
p. 43 - 48
(2012/08/14)
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- Metal-Catalyzed Carbon-Fluorine Bond Formation
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One aspect of the invention relates to a metal-catalyzed conversion of aryl halides and sulfonates to the corresponding aryl fluorides. Another aspect of the invention relates to a metal-catalyzed conversion of heteroaryl halides and sulfonates to the corresponding heteroaryl fluorides. Another aspect of the invention relates to a metal-catalyzed conversion of vinyl halides and sulfonates to the corresponding vinyl fluorides. In certain embodiments, simple fluoride sources, such as AgF and CsF, are used. In certain embodiments, the transformations tolerate a wide range of functional groups, allowing for introduction of fluorine atoms into highly functionalized organic molecules.
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Page/Page column 18
(2011/02/18)
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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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- 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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- Method For Preparation Of A Fluoroaromatic Compound From An Aminoaromatic Compound
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The invention relates to a method for preparation of fluorinated aromatic compounds from the corresponding amines by replacement of the amino group with a fluorine atom. The method of preparation of a fluoroaromatic compound from an aromatic compound with at least one amino group on the aromatic ring is characterized by the reaction of said aromatic amine compound with a nitrosating agent in the presence of a source of boron trifluoride in an organic medium, and carrying out a thermal treatment of the reaction medium comprising the diazonium salt thus obtained to give the fluoroaromatic compound directly by decomposition of the diazonium salt without intermediate isolation thereof.
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Page/Page column 8
(2008/06/13)
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- One-pot fluoro-de-diazoniation of anilines in organic medium
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Treatment of anilines with tert-butyl nitrite in the presence of boron trifluoride in ortho-dichlorobenzene leads to in situ fluoro-de-diazoniation and affords the corresponding fluoroaromatics with fair yields. This process, conducted in organic medium without Broensted acids, does not require isolation of hazardous diazonium salts and reduces the amounts of wastes. The results of the first screening are given.
- Garel, Laurent,Saint-Jalmes, Laurent
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p. 5705 - 5708
(2007/10/03)
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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 5-6
(2008/06/13)
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- Facile Synthesis of 2-Bromo-3-fluorobenzonitrile: An Application and Study of the Halodeboronation of Aryl Boronic Acids
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A scaleable synthesis of 2-bromo-3-fluorobenzonitrile via the NaOMe-catalyzed bromodeboronation of 2-cyano-6-fluorophenylboronic acid was developed. The generality of this transformation was demonstrated through the halodeboronation of a series of aryl boronic acids. Both aryl bromides and aryl chlorides were formed in good to excellent yields when the corresponding aryl boronic acid was treated with 1,3-dihalo-5,5-dimethylhydantoin and 5 mol % NaOMe.
- Szumigala Jr., Ronald H.,Devine, Paul N.,Gauthier Jr., Donald R.,Volante
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p. 566 - 569
(2007/10/03)
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- Method for producing tetrakis ( fluoroaryl) borate-magnesium compound
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Fluoroaryl magnesium halide is reacted with a boron compound so that a molar ratio of the fluoroaryl magnesium halide to the boron compound is not less than 3.0 and not more than 3.7, so as to produce a tetrakis (fluoroaryl) borate·magnesium compound. With this method, there occurs no hydrogen fluoride which corrodes a producing apparatus and requires troublesome waste water treatment.
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- 1-Fluoro-2,4,6-trichloro-1,3,5-triazinium tetrafluoroborate: Synthesis, characterization, and ability to effect electrophilic aromatic substitution
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The synthesis of 1-fluoro-2,4,6-trichloro-1,3,5-triazinium tetrafluoroborate, [(ClCN)3F]+[BF4] - (1), from (ClCN)3, BF3 and F2 is reported. Compound 1 was shown to be a useful reagent for the quantitative fluorination of aromatic substrates such as benzene, chlorobenzene, nitrobenzene, and methoxybenzene.
- Banks, R. Eric,Besheesh, Mohamed K.,Fraenk, Wolfgang,Klap?tke, Thomas M.
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p. 229 - 232
(2007/10/03)
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- Process for preparation of substituted aromatic compound
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A substituted aromatic compound substituted with Q is obtained by reacting a phosphazenium compound represented by formula (1) (in the formula, Q?represents an anion in a form derived by elimination of a proton from an inorganic acid, or an active hydrogen compound having an active hydrogen on an oxygen atom, a nitrogen atom or a sulfur atom; a, b, c and d, each independently, is 0 or 1, but all of them are not 0 simultaneously; and R groups represent the same or different hydrocarbon groups having 1 to 10 carbon atoms, or two Rs on each common nitrogen atom may be bonded together to form a ring structure) with a halogenated aromatic compound having halogen atoms; whereby, at least one halogen atom in the halogenated aromatic compound is substituted with Q (where, Q represents an inorganic group or an organic group in a form derived by elimination of one electron from Q?in formula (1)).
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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
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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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- Preparation process of fluorine substituted aromatic compound
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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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- Electrophilic fluorination of aromatics with selectfluor and trifluoromethanesulfonic acid 1
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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)
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- Preparation of aromatic fluorides: Facile photo-induced fluorinative decomposition of arenediazonium salts and their related compounds using pyridine-nHF
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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
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p. 127 - 133
(2007/10/03)
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- Deaminative Fluorination of Anilines with Silicon Tetrafluoride: Utility of Silicon Tetrafluoride as a Fluorine Source
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Application of silicon tetrafluoride to deaminative fluorination of anilines as a fluorine source is investigated. A diazotization of anilines proceeds with silicon tetrafluoride and tbutyl nitrite under mild condition and the following fluorodediazoniation affords fluoroarenes in good yields.
- Tamura, Masanori,Shibakami, Motonari,Sekiya, Akira
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p. 725 - 727
(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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- An improved method for fluoro-dediazoniation of arylamines substituted with polar groups
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The addition of SnX2 (SnCl2 or SnF2), as a low redox potential reductant, at the fluoro-dediazoniation step in the deaminative fluorination of aryl amines substituted with polar groups gave high selectivities for the formation of fluoroaromatics under mild conditions. The selectivities were further increased by the addition of a nucleophilic fluoride anion source, i.e. tetrabutylammonium dihydrogen trifluoride nBu4N+ H2F3-, along with the reductants.
- Sasaki, Koshi,Oishi, Mari,Imaki, Naoshi
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- Facile Hydrodehalogenation with H2 and Pd/C Catalyst under Multiphase Conditions. 2. Selectivity and Kinetics
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Hydrodehalogenation of polyhalogenated aromatics with Pd/C catalyst carried out in the presence of a quaternary onium salt follows zero-order kinetics in the substrate and first-order kinetics in the Pd/C catalyst; the related rate constants were determined for o-, m- and p-bromotoluenes, o-, m- and p-chloroalkylbenzenes (methyl, ethyl, and propyl derivatives), and other aryl halides.Reaction rates, depending on the aromatic to be reduced, may be strongly enhanced by the presence of quaternary onium salts: the isomeric chloroethylbenzenes were reduced 50 times faster when operating in the presence of Aliquat 336 (1).Also the hindered 2-chloro-m-xylene easily yielded m-xylene.The cocatalyst onium salts operate by being adsorbed on the Pd/C surface, as shown when kinetic constants are reported by varying the onium salt amount: classical Langmuir adsorption isotherms are observed.The presence of the onium salt may also influence selectivity in the reduction of isomeric aryl halides: when 1 is present, p-dichlorobenzene reacts in diethyl ether at 20 deg C, 5-fold slower than the ortho isomer; whereas the reduction rates of the two compounds are almost the same in its absence.
- Marques, Carlos Alberto,Selva, Maurizio,Tundo, Pietro
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p. 3830 - 3837
(2007/10/02)
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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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- Exchange of halogens between aromatic compounds in the presence of Cu-HZSM-5 zeolite
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The reactions between various haloaromatics in binary mixtures which were approximately equimolar, were studied in gas-phase (673 K, atmospheric: pressure) in the presence of a 2 wt % Cu-HZSM-5 zeolite. The exchange of halogens (ipso substitution) between the two compounds was assumed to occur either through a radical mechanism involving an electron transfer between an atom of copper (I) and one aromatic molecule or through a nucleophilic substitution involving arylcopper complexes as intermediates.
- Imhaoulne,Imhaoulene,Vivier,Guisnet,Petot,Perot,Gubelmann
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p. 12913 - 12922
(2007/10/02)
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- Oxidative fluorination in amine-HF mixtures
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The selective electrochemical fluorination of alkenes, phenanthroline, naphthalene and chlorobenzene in neat amine-HF mixtures is described, together with the chemistry of 4,4-difluorocyclohexadienone.
- Meurs,Eilenberg
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p. 705 - 714
(2007/10/02)
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- Magnetic susceptibilities of organic compounds: Part V - Influence of substituents on diamagnetic susceptibilities of disubstituted and trisubstituted benzenes
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The magnetic susceptibilities of a number of triads of isomeric disubstituted benzenes have been determined, choosing the compounds in such a way that the substituents are present in the following combinations: (i) two electron-releasing substituents, (ii) a halogeno and an electron-releasing substituent, (iii) a halogeno and an electron-attracting substituent, and (iv) two halogeno substituents.The data show that for types (i), (ii) and (iv), the ortho isomers have the highest magnetic susceptibilities, the susceptibilities decreasing in the order: ortho > meta > para; for type (iii), the meta-isomers have the highest susceptibilities, the susceptibilities decreasing in the order: meta > para > ortho.The diamagnetic susceptibilities of some isomeric trisubstituted benzenes have also been determined and the data reveal that the susceptibility is the highest where the crowding of substituents is the highest (1,2,3-isomer) and lowest where the substituents are staggered and least crowded (1,3,5-isomer).Another observation made in the case of trisubstituted benzene is the applicability of a principle of additivity of their diamagnetic susceptibilities.
- Baliah, V.,Jeyanthy, J. Judith Diana
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p. 472 - 476
(2007/10/02)
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- Preparation of substituted fluorobenzenes
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Substituted fluorobenzenes are produced by pyrolyzing vinylfluorocyclobutanes at a temperature of 250°-450° C. in the presence of activated carbon or certain metal oxides or mixtures of metal oxides.
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- OXIDATIVE CHLORINATION OF AROMATIC COMPOUNDS IN THE PRESENCE OF NITROGEN-CONTAINING OXIDIZING AGENTS
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Mixture of the chlorides and nitrates of alkali metals in aqueous trifluoroacetic acid can be used for the selective oxidative chlorination of benzene, halogenobenzenes, toluene, and p-toluic acid with preparative yields.By variation of the water content of the solvent and the nitrate-chloride ratio it is possible to suppress the nitration side reaction.In the presence of oxygen or air alkali-metal nitrites can also be used as oxidizing agents in this process.The chlorinating agent in these systems is molecular chlorine, as confirmed by a comparative study of the reactions of two groups of potential chlorinating agents (nitrosyl chloride and nitryl chloride) under these conditions.The reactions of naphthalene and polymethylbenzenes with nitrosyl chloride in trifluoroacetic acid, leading to the products from chlorination and dehydrooligomerization of the aromatic substrates, were also studied.
- Makhon'kov, D. I.,Cheprakov, A. V.,Rodkin, M. A.,Beletskaya, I. P.
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p. 211 - 217
(2007/10/02)
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- OXIDATION BY METAL SALTS. OXIDATIVE HALOGENATION OF BENZENE AND HALOBENZENES PROMOTED BY Co(III) AND Mn(III) ACETATES IN TRIFLUOROACETIC ACID AND ITS AQUEOUS SOLUTIONS
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A study was carried out on the oxidation of benzene and halobenzenes by Co(III) and Mn(III) acetates in the presence of alkali metal chlorides and bromides in CF3CO2H and its aqueous solutions (10-33 vol. percent H2O).The optimal water content in the solution is a function both of the nature of the metal oxidizing agent and the aromatic substrate.The reaction presumably proceeds through the formation of an aromatic radical-cation which then reacts with the halide anion.The oxidative chlorination of bromobenzene is complicated by ipso substitution and bromine redistribution.Phenyl iodosodichloride may be isolated in preparative yield in the chlorination of iodobenzene.In other cases, variation of the reaction conditions may give high yields of the corresponding chlorine and bromine derivatives.The feasibility of polychlorination was studied.Possible reaction mechanisms were considered.
- Makhon'kov, D. I.,Cheprakov, A. V.,Beletskaya, I. P.
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p. 609 - 615
(2007/10/02)
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- OXIDATION BY THE SALTS OF METALS. VII. PLUMBATION AND OXIDATIVE SUBSTITUTION OF AROMATIC COMPOUNDS IN THE LEAD TETRAACETATE-LITHIUM CHLORIDE SYSTEM IN THE PRESENCE OF PERFLUORINATED CARBOXYLIC ACIDS
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The oxidation of benzene and substituted benzenes PhX with electron-donating (X = CH3, OCH3) and electron-withdrawing (X = Hlg, CF3, NO2) substituents in the Pb(OAc)4-LiCl system was investigated in the presence of perfluorinated carboxylic acids RfCOOH (Rf = CF3, C6F13).The reaction leads to the plumbation, chlorination, and acyloxylation products.It was shown that the reactions take place through the formation of aryl derivatives of lead(IV) with the participation of mixed-ligand complexes of lead.The products from the plumbation of toluene (in C6F13COOH in the absence of lithium chloride) and benzotrifluoro were isolated.In trifluoroacetic acid these intermediates undergo intramolecular redox decomposition with ligand transfer.The halogenobenzenes and benzotrifluoride are oxidized selectively in the CF3COOH-Pb(IV)-LiCl system, giving the corresponding aryl chlorides with yields close to quantitative (80-90percent).
- Serguchev, Yu. A.,Davydova, V. G.,Makhon'kov, D. I.,Beletskaya, I. P.
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p. 1006 - 1011
(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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- Substrate Selectivity and Orientation in Aromatic Substitution by Molecular Fluorine
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Direct elemental fluorination of representative aromatic substrates, including PhH, PhCH3, PhF, PhCl, PhBr, PhNO2, PhCN, and PhOCH3, has been investigated in inert solvents, e.g., CCl3F and other fluorocarbons, over the temperature range -154 to 40 deg C.In order to achieve the necessary control of the extremely reactivve electrophile, and to minimize unwanted modifications of the reaction environment, the fluorination has been carried out at extremely low rate and correspondingly low conversions, generally below 0.01percent, using as a reagent gaseous mixtures of F2 highly diluted (+ constants for all the substituents investigated, giving a ρ+ value of -2.45 for aromatic substitution by elemental fluorine with a correlation coefficient of 0.993.These results characterize F2 as a highly reactive, and correspondently unselective, reagent, and support a polar electrophilic substitution mechanism that is discussed and compared with other plausible fluorination pathways.
- Cacace, F.,Giacomello, P.,Wolf, A. P.
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p. 3511 - 3515
(2007/10/02)
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- New Method for Selective Monofluorination of Aromatics Using Silver Difluoride
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Fluorobenzene is obtained in 61percent yield from reaction of a solution of benzene in n-hexane with solid argentic fluoride (AgF2).The AgF2 acts as both a strong oxidant and the fluoride source.Cobaltic fluoride provides only low (8percent) yields of fluorobenzene under similar conditions.The predominant reaction of benzene solutions with AgF2 appears to proceed by a process involving initial electrophilic oxidative cis addition of two fluorine atoms from the solid AgF2 lattice to the para aromatic positions, leading to cis-3,6-difluoro-1,4-cyclohexadiene (F2CHD).The reductive elimination leaves solid argentous fluoride (AgF) which is easily recoverable by filtration.Elimination of HF from the F2CHD yields fluorobenzene.Reactions of haloaromatics with AgF2 generally proceed in a similar manner.Thus, further reaction of AgF2 with benzene or monohalo- or p-dihalobenzenes leads in steps to 3,3,6,6-tetrafluoro-1,4-cyclohexadiene (F4CHD) in up to 82percent yield.The modest to high yields of mono- and specific polyfluorinated aromatics contrast sharply with reported nonselective perfluorination in vapor-phase reactions of aromatics over AgF2 or CoF3.Reactions of AgF2 or CoF3 with solutions of nitrobenzene, acetophenone, benzoic acid, and benzonitrile give mixtures of o-, m-, and p-monofluoro derivatives.
- Zweig, Arnold,Fischer, Robert G.,Lancaster, John E.
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p. 3597 - 3603
(2007/10/02)
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- Process for preparing ortho substituted aryl fluorides
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A process is provided for preparing ortho substituted aryl fluorides from corresponding diazonium fluorides. More particularly, the invention relates to a method for thermally decomposing diazonium fluorides substituted in the ortho position with halogen or trihalomethyl to a corresponding aryl fluoride. The method involves heating the diazonium fluoride to a temperature above its decomposition temperature and above the temperature at which the resulting product distills by contacting the same with a heat exchange medium at a temperature in the range of 100°-350°C.
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