- Photoredox catalysis on unactivated substrates with strongly reducing iridium photosensitizers
-
Photoredox catalysis has emerged as a powerful strategy in synthetic organic chemistry, but substrates that are difficult to reduce either require complex reaction conditions or are not amenable at all to photoredox transformations. In this work, we show that strong bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands enable high-yielding photoredox transformations of challenging substrates with very simple reaction conditions that require only a single sacrificial reagent. Using blue or green visible-light activation we demonstrate a variety of reactions, which include hydrodehalogenation, cyclization, intramolecular radical addition, and prenylationviaradical-mediated pathways, with optimized conditions that only require the photocatalyst and a sacrificial reductant/hydrogen atom donor. Many of these reactions involve organobromide and organochloride substrates which in the past have had limited utility in photoredox catalysis. This work paves the way for the continued expansion of the substrate scope in photoredox catalysis.
- Shon, Jong-Hwa,Kim, Dooyoung,Rathnayake, Manjula D.,Sittel, Steven,Weaver, Jimmie,Teets, Thomas S.
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p. 4069 - 4078
(2021/04/06)
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- Continuous synthesis method of m-difluorobenzene based on micro-channel reactor
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The invention discloses a continuous synthesis method of m-difluorobenzene based on a micro-reactor. The continuous synthesis method comprises the following steps: adding m-phenylenediamine and a hydrochloric acid solution into a first micro-channel reactor, and conducting reacting to obtain an m-phenylenediamine hydrochloride solution; subjecting the m-phenylenediamine hydrochloride solution to reacting with nitrogen trioxide in a second micro-channel reactor to prepare a dichlorom-phenylenediamine diazonium salt solution; subjecting the dichlorom-phenylenediamine diazonium salt to reacting with fluoboric acid in a tubular reactor, conducting quick centrifuging after the reaction is finished, washing precipitates obtained by centrifuging, and drying the precipitates to obtain m-phenylenediamine diazonium difluoroborate; and mixing the m-phenylenediamine diazonium difluoroborate with a solvent, adding the obtained mixture into a reactor, carrying out heating for decomposition, carrying out atmospheric distillation on a product in the reactor after the decomposition is finished, and collecting a fraction with a temperature of 82-84 DEG C. According to the invention, nitrogen trioxide is used as a diazotization agent, so the reaction is green, and no by-product is produced; and centrifugal mother liquor in the reaction process is concentrated and then recycled, so cost is saved, and reaction efficiency is high.
- -
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Paragraph 0026-0063
(2021/04/10)
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- Protodeboronation of (Hetero)Arylboronic Esters: Direct versus Prehydrolytic Pathways and Self-/Auto-Catalysis
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The kinetics and mechanism of the base-catalyzed hydrolysis (ArB(OR)2→ ArB(OH)2) and protodeboronation (ArB(OR)2→ ArH) of a series of boronic esters, encompassing eight different polyols and 10 polyfluoroaryl and heteroaryl moieties, have been investigated by in situ and stopped-flow NMR spectroscopy (19F,1H, and11B), pH-rate dependence, isotope entrainment,2H KIEs, and KS-DFT computations. The study reveals the phenomenological stability of boronic esters under basic aqueous-organic conditions to be highly nuanced. In contrast to common assumption, esterification does not necessarily impart greater stability compared to the corresponding boronic acid. Moreover, hydrolysis of the ester to the boronic acid can be a dominant component of the overall protodeboronation process, augmented by self-, auto-, and oxidative (phenolic) catalysis when the pH is close to the pKaof the boronic acid/ester.
- Assante, Michele,Geogheghan, Katherine J.,Hayes, Hannah L. D.,Jin, Na,Leach, Andrew G.,Lloyd-Jones, Guy C.,Noonan, Gary,Tomasi, Simone,Wei, Ran
-
supporting information
p. 14814 - 14826
(2021/09/13)
-
- Efficient synthesis method of meta-fluoranisole (by machine translation)
-
The method is characterized by comprising the following steps: taking m-chloronitrobenzene as a raw material, carrying out high-temperature chlorination reaction, nitration reaction and fluorination reaction to obtain 2,4 - 2,4 -difluorobenzene and carrying out a methoxylation reaction with m-difluorobenzene as a raw material and carrying out methoxylation reaction to obtain m-fluorobenzyl ether; and the hydrogenation catalyst is a porous alumina loaded NiO-Co222O3-MoOO3 composite catalyst. The method disclosed by the invention is simple in process and high in product yield. (by machine translation)
- -
-
Paragraph 0026; 0034; 0036; 0044; 0046; 0054; 0056; 0064
(2020/06/05)
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- Gold Catalyzed Decarboxylative Cross-Coupling of Iodoarenes
-
This report details a decarboxylative cross-coupling of (hetero)aryl carboxylates with iodoarenes in the presence of a gold catalyst (>25 examples, up to 96% yield). This reaction is site specific, which overcomes prior limitations associated with gold catalyzed oxidative coupling reactions. The reactivity of the (hetero)aryl carboxylate correlates qualitatively to the field effect parameter (Fortho). Reactions with isolated gold complexes and DFT calculations support a mechanism proceeding through oxidative addition at a gold(I) cation with decarboxylation being viable at either a gold(I) or a silver(I) species.
- Daley, Ryan A.,Morrenzin, Aaron S.,Neufeldt, Sharon R.,Topczewski, Joseph J.
-
supporting information
p. 13210 - 13218
(2020/09/01)
-
- Aryl dechlorination and defluorination with an organic super-photoreductant
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Direct excitation of the commercially available super-electron donor tetrakis(dimethylamino)ethylene (TDAE) with light-emitting diodes at 440 or 390 nm provides a stoichiometric reductant that is able to reduce aryl chlorides and fluorides. The method is very simple and requires only TDAE, substrate, and solvent at room temperature. The photoactive excited state of TDAE has a lifetime of 17.3 ns in cyclohexane at room temperature and an oxidation potential of ca. -3.4 V vs. SCE. This makes TDAE one of the strongest photoreductants able to operate on the basis of single excitation with visible photons. Direct substrate activation occurs in benzene, but acetone is reduced by photoexcited TDAE and substrate reduction takes place by a previously unexplored solvent radical anion mechanism. Our work shows that solvent can have a leveling effect on the photochemically available redox power, reminiscent of the pH-leveling effect that solvent has in acid-base chemistry.
- Glaser, Felix,Kerzig, Christoph,Larsen, Christopher B.,Wenger, Oliver S.
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p. 1035 - 1041
(2020/08/28)
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- Novel manufacturing method of fluoro-aryl compounds and derivatives thereof
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The invention relates to a novel method of manufacturing fluoro-aryl compounds and derivatives thereof, in particular, fluorobenzene and derivatives thereof. The production environment of the manufacturing method is environmentally friendly. The shortages of a conventional method are overcome through a simple and beneficial mode. Compared with the prior art, the provided method is more effective,more environmentally friendly, and more energy saving. The method is used to produce core fluorinated aromatic compounds, preferably, core fluorinated fluorobenzene. On one aspect, the invention provides a method, which is advantages in industry and uses HF and a halogenated benzene precursor to prepare fluorobenzene and hydrogen halide. Moreover, the invention provides chlorobenzene as the primary raw material to prepare fluorobenzene, which is an important material in industry, and a beneficial, unexpected and simple application of chlorobenzene. In the prior art, the provided application ofchlorobenzene is unknown.
- -
-
Paragraph 0225-0228
(2020/01/25)
-
- Synthesis and Characterization of Strong Cyclometalated Iridium Photoreductants for Application in Photocatalytic Aryl Bromide Hydrodebromination
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A series of potent bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands is described. Structure-property analysis reveals that substituent modification of the NacNac ligands has a large effect on the ground-state IrIV/IrIII potential, which shifts cathodically as the NacNac is made more electron-rich. In addition, the excited-state IrIV/?IrIII potentials are ca. 300-500 mV more negative than that of fac-Ir(ppy)3 (ppy = 2-phenylpyridine), indicating that these compounds have much more reducing excited states. Rate constants for excited-state electron transfer between these photosensitizers and benzophenone are -2-3 times faster than fac-Ir(ppy)3, demonstrating that these complexes are both kinetically and thermodynamically more potent for excited-state electron transfer. We use these photosensitizers to optimize a simple reaction procedure for photocatalytic debromination of aryl bromide substrates, which requires only the photosensitizer, blue light, and an amine base, without silanes or other additives that are used in previously reported methods.
- Shon, Jong-Hwa,Sittel, Steven,Teets, Thomas S.
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p. 8646 - 8658
(2019/09/12)
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- Ni: Vs. Pd in Suzuki-Miyaura sp2-sp2 cross-coupling: A head-to-head study in a comparable precatalyst/ligand system
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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.
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supporting information
p. 5055 - 5059
(2019/06/03)
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- Reactions of Arylsulfonate Electrophiles with NMe4F: Mechanistic Insight, Reactivity, and Scope
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This paper describes a detailed study of the deoxyfluorination of aryl fluorosulfonates with tetramethylammonium fluoride (NMe4F) and ultimately identifies other sulfonate electrophiles that participate in this transformation. 19F NMR spectroscopic monitoring of the deoxyfluorination of aryl fluorosulfonates revealed the rapid formation of diaryl sulfates under the reaction conditions. These intermediates can proceed to fluorinated products; however, diaryl sulfate derivatives bearing electron-donating substituents react very slowly with NMe4F. Based on these findings, aryl triflate and aryl nonaflate derivatives were explored, since these cannot react to form diaryl sulfates. Aryl triflates were found to be particularly effective electrophiles for deoxyfluorination with NMe4F, and certain derivatives (i.e., those bearing electron-neutral/donating substituents) afforded higher yields than their aryl fluorosulfonate counterparts. Computational studies implicate a similar mechanism for deoxyfluorination of all the sulfonate electrophiles.
- Schimler, Sydonie D.,Froese, Robert D. J.,Bland, Douglas C.,Sanford, Melanie S.
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p. 11178 - 11190
(2018/09/12)
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- A Predictive Model for the Decarboxylation of Silver Benzoate Complexes Relevant to Decarboxylative Coupling Reactions
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Decarboxylative coupling reactions offer an attractive route to generate functionalized arenes from simple and readily available carboxylic acid coupling partners, yet they are underutilized due to limitations in the scope of carboxylic acid coupling partner. Here we report that the field effect parameter (F) has a substantial influence on the rate of decarboxylation of well-defined silver benzoate complexes. This finding provides the opportunity to surpass current substrate limitations associated with decarboxylation and to enable widespread utilization of decarboxylative coupling reactions.
- Crovak, Robert A.,Hoover, Jessica M.
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p. 2434 - 2437
(2018/02/28)
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- METHOD FOR AROMATIC FLUORINATION
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Disclosed is a fluorination method comprising providing an aryl fluorosuifonate and a fluorinating reagent to a reaction mixture; and reacting the aryl fluorosuifonate and the fluorinating reagent to provide a fluorinated aryl species. Also disclosed is a fluorination method comprising providing, a salt comprising a cation and an aryloxyiate, and SO2F2 to a reaction mixture; reacting the SO2F2 and the ammonium salt to provide a fluorinated aryl species. Further disclosed a fluorination method comprising providing a compound having the structure Ar-OH to a reaction mixture; where A is an aryl or heteroaryl; providing SO2F2 to the reaction mixture; providing a fluorinating reagent to the reaction mixture; reacting the SO2F2, the fluorinating reagent and the compound having the structure Ar-OH to provide a fluorinated aryl species having the structure Ar-F.
- -
-
Paragraph 0047-0049
(2017/12/18)
-
- 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.
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p. 2308 - 2316
(2017/06/30)
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- N-Sulfonylcarboxamide as an Oxidizing Directing Group for Ruthenium-Catalyzed C–H Activation/Annulation
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N-Sulfonylcarboxamides can act as both a directing group for C–H activation and an internal oxidant in the Ru-catalyzed annulation reaction with alkynes to give isoquinolones. Of all of the N-sulfonylcarboxamides that were studied, the N-(2,6-difluorophenyl)sulfonamide derivatives were found to be the most efficient and led to the formation of an unstable sulfinate byproduct that decomposed into 1,3-difluorobenzene under the reaction conditions. The described isoquinolone synthesis provides an alternative to the currently known traceless annulations of hydroxamic acid and sulfoximine derivatives.
- Petrova, Elina,Rasina, Dace,Jirgensons, Aigars
-
supporting information
p. 1773 - 1779
(2017/04/13)
-
- Nucleophilic deoxyfluorination of phenols via aryl fluorosulfonate intermediates
-
This report describes a method for the deoxyfluorination of phenols with sulfuryl fluoride (SO2F2) and tetramethylammonium fluoride (NMe4F) via aryl fluorosulfonate (ArOFs) intermediates. We first demonstrate that the reaction of ArOFs with NMe4F proceeds under mild conditions (often at room temperature) to afford a broad range of electronically diverse and functional group-rich aryl fluoride products. This transformation was then translated to a one-pot conversion of phenols to aryl fluorides using the combination of SO2F2 and NMe4F. Ab initio calculations suggest that carbon-fluorine bond formation proceeds via a concerted transition state rather than a discrete Meisenheimer intermediate.
- Schimler, Sydonie D.,Cismesia, Megan A.,Hanley, Patrick S.,Froese, Robert D.J.,Jansma, Matthew J.,Bland, Douglas C.,Sanford, Melanie S.
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p. 1452 - 1455
(2017/02/10)
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- Method for preparing difluorobenzene by tubular diazotization reaction
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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 0030; 0031
(2017/05/27)
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- Hydrodefluorination of fluoroaromatics by isopropyl alcohol catalyzed by a ruthenium NHC complex. An unusual role of the carbene ligand
-
The NHC (NHC = N-heterocyclic carbene) complex Cp*(IPr)RuH3 catalyzes hydrodefluorination of aromatic fluorides at 70 °C with isopropyl alcohol as the reducing reagent. The reaction is selective for aromatic fluorides, as almost negligible C(sp3)?F bond reduction takes place. The activity decreases from more to less fluorinated substrates, but polyaromatic monofluorides, such as 1-fluoronaphthalene and 6-fluoro-2-methylquinoline, can also be reduced in moderate to good yields. Kinetic studies are consistent with a mechanism based on elimination of NHC and reversible substrate coordination, followed by coordination of the alcohol.
- Mai, Van Hung,Nikonov, Georgii I.
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p. 7956 - 7961
(2018/05/23)
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- Synthetic method of m-difluorobenzene as diflunisal drug intermediate
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A synthetic method of m-difluorobenzene as a diflunisal drug intermediate comprises the following steps: (i) 100 ml of a fluoaluminic acid solution with the mass fraction of 60%-70% is added to a reaction vessel equipped with a stirrer and two dropping funnels, after the solution temperature is reduced to 30 DEG C, 0.2-0.25 mol of potassium bisulfite is added dropwise and dissolved in 50-70 ml of an aqueous solution, and 0.1 mol of m-phenylenediamine hydrochloride is dissolved in 50 ml of an aqueous solution; (ii) the prepared potassium bisulfite solution and m-phenylenediamine hydrochloride solution are added to the reaction vessel, the stirring speed is kept at 200-300 rpm, the reaction continues for 20-25 min, a product is subjected to pumping filtration, washing with a solution, drying by a drying agent, and diazonium difluoroaluminate is obtained; (3) solids are obtained and heated to 85-95 DEG C to be resolved and distilled, a crude product m-difluorobenzene is obtained, washed with a neutralizing solution and a salt solution and subjected to distillation again, fraction at 85-90 DEG C is collected, and a pure product m-difluorobenzene is obtained.
- -
-
Paragraph 0008; 0018-0020
(2017/03/14)
-
- 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)
-
- 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.
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p. 19597 - 19605
(2015/11/27)
-
- Rhodium catalyzed, carbon-hydrogen bond directed hydrodefluorination of fluoroarenes
-
[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.
-
supporting information
p. 7027 - 7030
(2015/05/19)
-
- Bimetallic Cu/Pd Catalysts with Bridging Aminopyrimidinyl Phosphines for Decarboxylative Cross-Coupling Reactions at Moderate Temperature
-
A bimetallic catalyst system is presented that enables the decarboxylative cross-coupling of triflates with carboxylate salts at only 100 °C, which is 70 °C lower than with previous Cu/Pd-based systems. The new protocol allows the coupling of a broad range of aryl triflates with various substituted 2-nitrobenzoates in good to excellent yields. The key feature of the catalyst system is a bidentate P,N-ligand designed to bridge the Pd and Cu centres and thereby facilitating the rate-determining transmetalation step. Mass spectrometry (ESI-MS) studies support the ability of the aminopyrimidinyl phosphine to simultaneously coordinate copper and palladium.
- Hackenberger, Dagmar,Song, Bingrui,Grünberg, Matthias F.,Farsadpour, Saeid,Menges, Fabian,Kelm, Harald,Gro?, Cedric,Wolff, Timm,Niedner-Schatteburg, Gereon,Thiel, Werner R.,Goo?en, Lukas J.
-
p. 3579 - 3588
(2015/11/10)
-
- Trifluoromethylation of arenediazonium salts with fluoroform-derived CuCF3 in aqueous media
-
A new protocol has been developed for trifluoromethylation of arenediazonium salts with moisture-sensitive CuCF3 (from fluoroform) in aqueous media. The reaction is governed by a radical mechanism, tolerates a broad variety of functional groups, and is applicable to the synthesis of complex, polyfunctionalized molecules. This journal is the Partner Organisations 2014.
- Lishchynskyi, Anton,Berthon, Guillaume,Grushin, Vladimir V.
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supporting information
p. 10237 - 10240
(2014/08/18)
-
- Gold(I)-catalyzed protodecarboxylation of (Hetero)aromatic carboxylic acids
-
Readily available, inexpensive and easy to handle, carboxylic acids have been shown to be very effective, greener coupling partners compared to costly organometallic reagents for the formation of C-C bonds. The use of well-defined gold complexes furnished 3 in slightly better yield with butyric acid, and in quantitative yield with adamantane-1-carboxylic acid. All reactions reached completion within 16 h. As with silver systems, this reactivity trend highlights, as previously observed, the benefits of potential coordinating groups in the ortho position to the gold binding site, which possibly facilitate the decarboxylation step. Additional reaction time and increased temperatures were necessary to afford the gold aryl products in satisfactory yields. Yet, some substrates such as 2-nitrobenzoic acids reacted poorly and could only be transformed in 50% yield.
- Dupuy, Stéphanie,Nolan, Steven P.
-
supporting information
p. 14034 - 14038
(2013/11/19)
-
- Fluoroform-derived CuCF3 for low-cost, simple, efficient, and safe trifluoromethylation of aryl boronic acids in air
-
Easy does it: Aryl boronic acids undergo smooth and selective trifluoromethylation with low-cost fluoroform-derived CuCF3 in DMF in non-dried air. The reaction occurs under mild conditions (1 atm, room temperature), exhibits unprecedented funct
- Novak, Petr,Lishchynskyi, Anton,Grushin, Vladimir V.
-
supporting information; experimental part
p. 7767 - 7770
(2012/08/29)
-
- Process for the Synthesis of Highly Active Binary Metal Fluoride as a Fluorinating Agent for Aromatics
-
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.
- -
-
Page/Page column 6-7
(2010/02/17)
-
- A catalytic C-C bond-forming reaction between aliphatic fluorohydrocarbons and arylsilanes
-
C-C coupling reactions between arylsilanes and alkylfluorides are efficiently catalyzed by disilyl cation 1. Primary as well as secondary alkylfluorides were quantitatively coupled with arylsilanes; however, in the case of tertiary fluorides, the hydrodef
- Luehmann, Nicole,Panisch, Robin,Mueller, Thomas
-
supporting information; experimental part
p. 533 - 537
(2010/10/19)
-
- Rh(I)-catalyzed decarboxylative transformations of arenecarboxylic acids: Ligand- and reagent-controlled selectivity toward hydrodecarboxylation or heck-mizoroki products
-
(Chemical Equetion Presentation) A Rh(I)-based catalyst system has been developed to promote three types of decarboxylative transformations of arenecarboxylic acids: (1) hydrodecarboxylation, (2) Heck-Mizoroki olefination, and (3) conjugate addition. Scopes of reactions (1) and (2) were studied, and the ligand and reagent dependence of selectivity was explored.
- Sun, Zhong-Ming,Zhang, Jing,Zhao, Pinjing
-
supporting information; experimental part
p. 992 - 995
(2010/06/16)
-
- Silver-catalysed protodecarboxylation of ortho-substituted benzoic acids
-
Catalytic amounts of Ag(i) salts in DMSO have been found to promote the protodecarboxylation of a wide variety of ortho-substituted benzoic acids under mild conditions and in excellent yields, highlighting a possible role for silver in decarboxylative cross-couplings. The Royal Society of Chemistry 2009.
- Cornella, Josep,Sanchez, Carolina,Banawa, David,Larrosa, Igor
-
supporting information; experimental part
p. 7176 - 7178
(2010/03/25)
-
- Kinetics of bromine-magnesium exchange reactions in substituted bromobenzenes
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Competition experiments have been performed to determine the relative reactivities of substituted bromobenzenes, bromonaphthalenes, and 9-bromoanthracene toward i-PrMgCl·;LiCl in THF at 0 °C. The rates of the bromine-magnesium exchange reactions are accelerated by electron-acceptor substituents, the activating efficiency of which increases in the order para 2 = 0.83) with the proton affinities of analogously substituted aryllithiums (slope 0.8). The kinetics of two representative bromoarenes with i-PrMgCl·LiCl were found to be first-order in both bromoarene and i-PrMgCl·LiCl. Combination of the resulting second-order rate constants with the krel values from competition experiments allowed us to calculate reaction times for the bromine-magnesium exchange reactions of a large variety of bromoarenes.
- Shi, Lei,Chu, Yuanyuan,Knoechel, Paul,Mayr, Herbert
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supporting information; experimental part
p. 2760 - 2764
(2009/08/15)
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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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- A practical palladium catalyzed dehalogenation of aryl halides and α-haloketones
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A practical and high-yielding protocol for the dehalogenation of aromatic halides is presented. In the presence of palladium acetate, triphenylphosphine, and potassium carbonate, a number of highly functionalized aromatic halides as well as α-haloketones were dehalogenated with alcohols as hydrogen donors.
- Chen, Jingbo,Zhang, Yushun,Yang, Liquan,Zhang, Xiang,Liu, Jianping,Li, Liang,Zhang, Hongbin
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p. 4266 - 4270
(2007/10/03)
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- Synthesis, NMR spectroscopic characterisation and reactions of 2,6-difluorophenylxenon fluoride, 2,6-F2C6H3XeF
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[2,6-F2C6H3Xe][BF4] is quantitatively transferred into 2,6-F2C6H3XeF in reactions with [NMe4]F. The latter has been isolated as a colourless solid which is stable in dichloromethane solution at room temperature for approximately 1 h. 2,6-F2C6H3XeF readily reacts with Me3SiX (X = Cl, Br, CN, NCO, OCOCF3, OSO2CF3, C6F5, 2,6-F2C6H3) to give compounds of general compositions 2,6-F2C6H3XeX which were identified by multinuclear NMR experiments. Evidence was found for C6H5Xe(2,6-F2C6H3) as a product of the reaction with C6H5SiF3.
- Bock, Harald,Scherer, Harald,Tyrra, Wieland,Naumann, Dieter
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p. 1440 - 1445
(2008/09/19)
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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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- Process for the preparation of 1,3-dihalo substituted benzene derivatives
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Production of 1,3-dihalobenzene derivatives (II) comprises gradually adding a 2,6-dihalobenzaldehyde derivative (I) to alkaline medium or gradually adding the alkaline medium to (I). Production of 1,3-dihalobenzene derivatives of formula (II) comprises gradually adding a 2,6-dihalobenzaldehyde derivative (I) to alkaline medium or gradually adding the alkaline medium to (I). X1, X2 = F, Cl or Br, and R1-R3 = H, halo, OH, 1-12C alkyl, CF3, CHO, 6-14C aryl, alkoxy, aryloxy or NO2.
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- A product analytical study of the thermal and photolytic decomposition of some arenediazonium salts in solution
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Products of thermal and photochemical reactions of eleven arenediazonium tetrafluoroborates in various solvents have been analyzed. All compounds in most solvents undergo unimolecular heterolysis to give singlet aryl cations which are captured by solvent. This mechanism is dominant for arenediazonium ions without electron-withdrawing substituents in all solvents, and the only reaction observed in water. Additionally, appreciable yields of fluoroarenes are obtained by fluoride abstraction by the aryl cation from fluorinated solvents and from tetrafluoroborate in fluorinated solvents. Yields from photochemical processes are very similar to those from thermal reactions indicating that the main reactions proceed through common or very similar intermediates. Aryl cations formed from ion-paired diazonium ions may react with the counterion, but fragmentation of dissociated diazonium ions leads only to solvent-derived product. Some arenediazonium ions in some solvents undergo an alternative radical reaction leading principally to hydrodediazoniation. It is proposed that this reaction involves initial rate-limiting electron transfer from ethanol to the arenediazonium ion followed rapidly by homolysis of the resultant aryldiazenyl radical. Within the same solvent cage, the aryl radical then either abstracts an α-hydrogen from the ethanol radical cation generated in the first step to give the reduction product and protonated acetaldehyde, or combines with it at the oxygen to give a protonated aryl ethyl ether.
- Canning, Peter S. J.,Maskill, Howard,McCrudden, Katharine,Sexton, Brian
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p. 789 - 800
(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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- Polyfluoroorganoboron-oxygen compounds. 2 [1]: Base-catalysed hydrodeboration of polyfluorophenyl(dihydroxy)boranes
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Polyfluorinated phenyl(dihydroxy)boranes C6H5-nFnB(OH)2 (n = 3 - 5) underwent hydrodeboration (formal replacement of the (dihydroxy)boryl group by hydrogen) in the presence of bases (MeOH, 33% H2O-MeO
- Frohn,Adonin,Bardin,Starichenko
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p. 2834 - 2838
(2008/10/08)
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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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- Sulfonyl chloride as a disposable electron withdrawing substituent in halex fluorinations
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Syntheses of 1,3-difluorobenzene and 2,6-difluorotoluene are described via chlorosulfonation, catalytic Halex-fluorination, and desulfination of 1,3-dichlorobenzene and 2,6-dichlorotoluene.
- Kageyama, Hiroyuki,Suzuki, Hiroshi,Kimura, Yoshikazu
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- Electrophilic ipso substitution of trimethylsilyl groups in fluorobenzenes
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Using variants of literature methods 2,4- and 2,6- difluorophenyltrimethylsilanes have been bromodesilylated to the corresponding bromodifluorobenzenes in moderate to good yields, 3-bromo-2,6-difluorophenyltrimethylsilane afforded 1,3-dibromo-2,4-difluorobenzene whilst 1,3-difluoro-2,4-bis(trimethylsilyl)benzene yielded 3-bromo-2,6-difluorophenyltrimethylsilane. Application of either the Eaborn or Chvalovsky methods of nitrodesilylation to 4-fluorophenyltrimethylsilane, 2,4-difluorophenyltrimethylsilane and 2,6-difluorophenyltrimethylsilane afforded largely the corresponding desilylated products together with products associated with initial protodesilylation, followed by nitration of the resulting fluorobenzenes. The results obtained show that ipso desilylation in the fluoroaromatic series does follow the expected pattern previously obtained in the hydrocarbon analogues. They also show that in some cases the formation of unusually substituted fluoroarenes can be achieved more readily than by the methods previously used.
- Coe, Paul L.,Stuart, Alison M.,Moody, David J.
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- Dediazoniation reactions of arenediazonium ions under solvolytic conditions: Fluoride anion abstraction from trifluoroethanol and α-hydrogen atom abstraction from ethanol
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Arenediazonium salts decompose thermally and photochemically in trifluoroethanol to yield trifluoroethyl ethers and (in part by fluoride abstraction from the solvent) fluoroarenes; the less reactive compounds in trifluoroethanol decompose readily in ethanol to give arenes in a radical reaction involving abstraction of the α-hydrogen from the ethanol.
- Canning, Peter S. J.,McCrudden, Katharine,Maskill, Howard,Sexton, Brian
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p. 1971 - 1972
(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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- The Photolyses of 2,6- and 2,4-Difluorohalobenzenes
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Photolyses of 2,6- and 2,4-difluorobromobenzenes in acetonitrile gave isomerized and brominated products in addition to 1,3-difluorobenzene produced by the dehalogenation.The reactions were compared with similar reactions of the corresponding chloro- and iodoarenes.In general, photolytic cleavage of the C-X bond of 2,6-difluorohalo(X)benzene was shown to proceed more easily than the corresponding 2,4-difluorohalo compound.
- Song, Yong-Qi,Yuzuri, Tomoaki,Suezawa, Hiroko,Sakakibara, Kazuhisa,Hirota, Minoru,Nakada, Masahiro
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p. 1875 - 1878
(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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- Process for the preparation of aromatic fluoro compounds
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The invention relates to a process for the preparation of aromatic fluoro compounds of the formula I in which Ar is phenyl, naphthyl or pyridyl, R1, R2 and R3 independently of one another are hydrogen, halide, (C1 -C4)-alkyl, phenyl, NR2, OR, CN, COH or COR, where R is hydrogen or (C1 -C6)-alkyl, and n=1, 2, 3, 4 or 5, which comprises reacting aromatic fluoro compounds of the formula II in which Ar, R1, R2, R3 and n have the abovementioned meaning, each X is a chlorine or bromine atom and m=1, 2, 3, 4 or 5, with hydrogen in the presence of a palladium catalyst, a water-insoluble amine which also does not form water-soluble hydrohalides, and if desired an inert solvent.
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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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- Synthesis of 2,4-difluoroaniline and 1,3-difluorobenzene from 1,2,4- trichlorbenzene
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Nitration of inexpensive 1,2,4-trichlorobenzene gave 2,4,5- trichloronitrobenzene (90%) which was treated with KF to form 2,4-difluoro- 5-chloronitrobenzene (70%). This was selectively hydrogenated over Pd / C to give 2,4-difluoroaniline (80%). Deamination afforded 1,3-difluorobenzene. The sequence avoids the need for costly 1,3-dichlorobenzene.
- Mason,Milner
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p. 529 - 532
(2007/10/02)
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