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Low-temperature and highly efficient liquid-phase catalytic nitration of chlorobenzene with NO2: Remarkably improving the para-selectivity in O2-Ac2O-Hβ composite system
In this work, we developed a low-temperature and efficient approach for the highly selective preparation of valuable p-nitrochlorobenzene from the liquid-phase catalytic nitration of chlorobenzene with NO2 in O2-Ac2O-Hβ composite system. The results demonstrated that the introduction of molecular oxygen remarkably enhanced the chlorobenzene conversion and the cooperation catalysis of Hβ zeolite and Ac2O envidently improved the selectivity to para-nitro product. Under the optimized reaction conditions, 93.6 % of the selectivity to p-nitrochlorobenzene with 84.0 % of chlorobenzene conversion was obtained, and the ratio of p-nitrochlorobenzene to o-nitrochlorobenzene could reach up to 20.3. Furthermore, the selectivity distribution of nitration products was reasonably explained by the density functional theory (DFT) calculation. Finally, the possible nitration reaction pathway of chlorobenzene with NO2 was suggested in O2-Ac2O-Hβ composite catalytic system. The present work affords a new and mild nitration approach for highly selective preparation of valuable para-nitro products, and has potential industrial application prospects.
Deng, Renjie,Liu, Pingle,Luo, He'an,Ni, Wenjin,You, Kuiyi,Zhao, Fangfang
(2020/02/26)

N-Nitroheterocycles: Bench-Stable Organic Reagents for Catalytic Ipso-Nitration of Aryl- And Heteroarylboronic Acids
Photocatalytic and metal-free protocols to access various aromatic and heteroaromatic nitro compounds through ipso-nitration of readily available boronic acid derivatives were developed using non-metal-based, bench-stable, and recyclable nitrating reagents. These methods are operationally simple, mild, regioselective, and possess excellent functional group compatibility, delivering desired products in up to 99% yield.
Budinská, Alena,Katayev, Dmitry,Passera, Alessandro,Zhang, Kun
supporting information

(2020/03/30)

Catalyst and application thereof in synthesis of aromatic fluorine compounds
The invention belongs to the field of catalyst preparation and application, and particularly relates to a catalyst and application thereof in synthesis of aromatic fluorine compounds. The nickel catalyst is dichloro-bis-(tri-cyclohexylphosphine) nickel, and the molecular formula of the nickel catalyst is Ni (Py3) 2Cl2. The nickel catalyst is applied to catalyzing inorganic fluoride to replace aromatic chloride to synthesize fluoride. The catalyst has the advantages of easily available reagents, simple catalyst synthesis, simple operation conditions, low reaction temperature, high reaction yield and less time consumption.
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Paragraph 0036-0038

(2020/11/10)

Flow hydrodediazoniation of aromatic heterocycles
Continuous flow processing was applied for the rapid replacement of an aromatic amino group with a hydride. The approach was applied to a range of aromatic heterocycles, confirming the wide scope and substituent-tolerance of the processes. Flow equipment was utilized and the process optimised to overcome the problematically-unstable intermediates that have restricted yields in previous studies relying on batch procedures. Various common organic solvents were investigated as potential hydride sources. The approach has allowed key structures, such as amino-pyrazoles and aminopyridines, to be deaminated in good yield using a purely organic-soluble system.
R?der, Liesa,Nicholls, Alexander J.,Baxendale, Ian R.
(2019/06/05)

Transition-State Interactions in a Promiscuous Enzyme: Sulfate and Phosphate Monoester Hydrolysis by Pseudomonas aeruginosa Arylsulfatase
Pseudomonas aeruginosa arylsulfatase (PAS) hydrolyzes sulfate and, promiscuously, phosphate monoesters. Enzyme-catalyzed sulfate transfer is crucial to a wide variety of biological processes, but detailed studies of the mechanistic contributions to its catalysis are lacking. We present linear free energy relationships (LFERs) and kinetic isotope effects (KIEs) of PAS and analyses of active site mutants that suggest a key role for leaving group (LG) stabilization. In LFERs PASWT has a much less negative Br?nsted coefficient (βleaving groupobs-Enz = 0.33) than the uncatalyzed reaction (βleaving groupobs = 1.81). This situation is diminished when cationic active site groups are exchanged for alanine. The considerable degree of bond breaking during the transition state (TS) is evidenced by an 18Obridge KIE of 1.0088. LFER and KIE data for several active site mutants point to leaving group stabilization by active site K375, in cooperation with H211. 15N KIEs and the increased sensitivity to leaving group ability of the sulfatase activity in neat D2O (βleaving groupH-D = +0.06) suggest that the mechanism for S-Obridge bond fission shifts, with decreasing leaving group ability, from charge compensation via Lewis acid interactions toward direct proton donation. 18Ononbridge KIEs indicate that the TS for PAS-catalyzed sulfate monoester hydrolysis has a significantly more associative character compared to the uncatalyzed reaction, while PAS-catalyzed phosphate monoester hydrolysis does not show this shift. This difference in enzyme-catalyzed TSs appears to be the major factor favoring specificity toward sulfate over phosphate esters by this promiscuous hydrolase, since other features are either too similar (uncatalyzed TS) or inherently favor phosphate (charge).
Van Loo, Bert,Berry, Ryan,Boonyuen, Usa,Mohamed, Mark F.,Golicnik, Marko,Hengge, AlVan C.,Hollfelder, Florian
p. 1363 - 1378
(2019/03/11)

Synthesis of nitroolefins and nitroarenes under mild conditions
1,3-Disulfonic acid imidazolium nitrate {[Dsim]NO3} was prepared and characterized as a new ionic liquid and nitrating agent for the ipso-nitration of various arylboronic acids and nitro-Hunsdiecker reaction of different α,β-unsaturated acids and benzoic acid derivatives, by in situ generation of NO2 to give various nitroarenes and nitroolefins without using any cocatalysts and solvents under mild conditions.
Zarei, Mahmoud,Noroozizadeh, Ehsan,Moosavi-Zare, Ahmad R.,Zolfigol, Mohammad A.
p. 3645 - 3650
(2018/04/14)

A Predictive Model for the Decarboxylation of Silver Benzoate Complexes Relevant to Decarboxylative Coupling Reactions
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.
p. 2434 - 2437
(2018/02/28)

Synthetic method of aryl halide taking aryl carboxylic acid as raw material
A synthetic method of an aryl halide taking aryl carboxylic acid as a raw material is characterized in that a corresponding aryl halide is formed by carrying out substitution reaction on an aryl carboxylic acid compound and haloid salt MX in an organic solvent under the condition that oxygen, a silver catalyst, a copper additive and a bidentate nitrogen ligand exist, wherein M in MX represents alkali metal or alkaline earth metal, and X represents F, Cl, Br or I. Compared with a conventional aryl halide synthetic method, the synthetic method disclosed by the invention has the obvious advantages that reaction raw materials (comprising aryl carboxylic acid and MX) are cheap and easy to obtain, the using amount of a metal catalyst is small, pollution to the environment when the oxygen is used as an oxidant is the smallest, good tolerance to various functional groups on an aromatic ring is obtained, the yield is high, and the like. The synthetic method disclosed by the invention can be widely applied to synthesis in the fields of medicine, materials, natural products and the like in industry and academia.
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Paragraph 0067

(2018/01/03)

Reactions of aromatic compounds with xenon difluoride
Reactions of substituted benzenes C6H5R (R = Me, F, Cl, Br, CF3, NO2) with xenon difluoride in the presence of boron trifluoride–diethyl ether complex in weakly acidic (1,1,1,3,3-pentafluorobutane) and weakly basic media (acetonitrile) have been studied. These reactions lead to the formation of fluorobenzene derivatives FC6H4R (isomer mixture) together with isomeric difluorobenzenes and fluorinated and non-fluorinated biphenyls. The results have been compared with previously reported data obtained in other solvents using other catalysts.
Bardin,Adonin, N. Yu.
p. 1400 - 1407
(2016/11/29)

A simple protocol for Cu-catalyzed protodecarboxylation of (hetero)aromatic carboxylic acids
A simple and practical protodecarboxylation of o-nitrobenzoic acids as well as heteroaromatic carboxylic acids with various substituents via using CuI/Et3N has been established. This transformation provides a viable and low-cost approach to generating previously unavailable substituted arenes from readily accessible aryl carboxylic acids as the starting materials.
Li, Zhaojie,Fu, Zhengjiang,Zhang, Haixia,Long, Jiao,Song, Yuanyuan,Cai, Hu
supporting information
p. 3014 - 3018
(2016/05/09)

Fluorination of aromatic compounds with xenon difluoride in the presence of boron trifluoride etherate
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
p. 1049 - 1052
(2016/02/09)

A Fluorinated Ligand Enables Room-Temperature and Regioselective Pd-Catalyzed Fluorination of Aryl Triflates and Bromides
A new biaryl monophosphine ligand (AlPhos, L1) allows for the room-temperature Pd-catalyzed fluorination of a variety of activated (hetero)aryl triflates. Furthermore, aryl triflates and bromides that are prone to give mixtures of regioisomeric aryl fluorides with Pd-catalysis can now be converted to the desired aryl fluorides with high regioselectivity. Analysis of the solid-state structures of several Pd(II) complexes, as well as density functional theory (DFT) calculations, shed light on the origin of the enhanced reactivity observed with L1.
Sather, Aaron C.,Lee, Hong Geun,De La Rosa, Valentina Y.,Yang, Yang,Müller, Peter,Buchwald, Stephen L.
supporting information
p. 13433 - 13438
(2015/11/09)

Studying regioisomer formation in the pd-catalyzed fluorination of aryl triflates by deuterium labeling
Isotopic labeling has been used to determine that a portion of the desired product in the Pd-catalyzed fluorination of electron-rich, non-ortho-substituted aryl triflates results from direct C-F cross-coupling. In some cases, formation of a Pd-aryne intermediate is responsible for producing undesired regioisomers. The generation of the Pd-aryne intermediate occurs primarily via ortho-deprotonation of a L·Pd(Ar)OTf (L = biaryl monophosphine) species by CsF and thus competes directly with the transmetalation step of the catalytic cycle. Deuterium labeling studies were conducted with a variety of aryl triflates.
Milner, Phillip J.,Kinzel, Tom,Zhang, Yong,Buchwald, Stephen L.
supporting information
p. 15757 - 15766
(2015/02/02)

Regioselective nitration of aromatics with nanomagnetic solid superacid SO42-/ZrO2-MxOy-Fe 3O4 and its theoretical studies
A series of micro- and nanosulfated zirconia loaded on Fe3O 4 or other metal oxides (SO42-/ZrO 2-MxOy-Fe3O4 (M=Ti 4+, V5+, and Zn2+)) was prepared, characterized, and used in nitration. The nitration conditions with these solid superacids were then optimized to achieve the best regioselectivity and improve the performances of the catalysts as well. In the experimental results, SZTF (SO42-/ZrO2-TiO2-Fe 3O4) showed excellent catalytic activity and it increased the surface area of SO42-/ZrO2 by up to 15 %. The increase not only facilitated the generation of NO2+, but also provided more opportunities for metal ions to interact with aromatic compounds. With chlorobenzene as substrate, theoretical research on its geometric parameters, electron clouds, and electron spin density was used to investigate the interaction between transition metals and chlorobenzene.
Wang, Peng Cheng,Zhu, Jie,Liu, Xiang,Lu, Ting Ting,Lu, Ming
p. 310 - 317
(2013/08/23)

Continuous flow reactor for Balz-Schiemann reaction: A new procedure for the preparation of aromatic fluorides
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
p. 1261 - 1263
(2013/03/14)

Fluorination of aryl boronic acids using acetyl hypofluorite made directly from diluted fluorine
Aryl boronic acids or pinacol esters containing EDG were converted in good yields and fast reactions to the corresponding aryl fluorides using the readily obtainable solutions of AcOF. In reactions with aryl boronic acids containing EWG at the para position, there are two competing forces: one directing the fluorination to take place ortho to the boronic acid and the other, toward an ipso substitution. With EWG meta to the boronic acid, substitution ipso to the boron moiety takes place in good yields.
Vints, Inna,Gatenyo, Julia,Rozen, Shlomo
p. 11794 - 11797
(2014/01/06)

Recyclable nanoscale copper(I) catalysts in ionic liquid media for selective decarboxylative C-C bond cleavage
Here we report the synthesis and application of finely divided Cu 2O nanoparticles (Cu2O-NPs) in the range from 5.5 nm to 8.0 nm in phosphonium ionic liquids as the first recyclable and effective catalytic system for smooth, ligand- and additive-free protodecarboxylation of 2-nitrobenzoic acid as a model substrate and further derivatives. The reactions run with low catalyst loadings and result in quantitative yield in ten consecutive recycling experiments. In addition this system is highly selective towards electron-poor 2-nitrobenzoic acids.
Kessler, Michael T.,Gedig, Christian,Sahler, Sebastian,Wand, Patricia,Robke, Silas,Prechtl, Martin H. G.
p. 992 - 1001
(2013/04/24)

Synthesis of aryl fluorides on a solid support and in solution by utilizing a fluorinated solvent
(Figure Presented) F for fast: The perfluorinated solvent C 6F14 is the key to a new variant of the BalzSchiemann reaction for the synthesis of fluorinated arenes. Triazenes are converted into fluoroarenes under mild con-ditions on a support and in solution (see scheme). The method is straightforward and inexpensive, and yields previously difficult-to-prepare fluoroarenes in high purity.
Doebele, Marion,Vanderheiden, Sylvia,Jung, Nicole,Braese, Stefan
supporting information; experimental part
p. 5986 - 5988
(2010/10/01)

A mild and efficient method for nucleophilic aromatic fluorination using tetrabutylammonium fluoride as fluorinating reagent
Anhydrous tetrabutylammonium fluoride (TBAFanh.) has been found to be a highly efficient fluorinating reagent for nucleophilic aromatic fluorinations such as fluorodenitration or halogen exchange (Halex) reaction. The products were formed in high to excellent yields under surprisingly mild reaction conditions and no phenol or ether side-products were detected in these reactions.
Hu, Yu Feng,Luo, Jun,Lü, Chun Xu
experimental part
p. 151 - 154
(2010/11/18)

N-(trifluoromethylsulfonyl)aryloxytrifluoromethylsulfoximines [ArO-SO(CF3)=NTf] and N-aryltriflimides Ar-N(Tf)2 by thermal and photolytic dediazoniation of [ArN2][BF4] in [BMIM][Tf2N] ionic liquid: Exploiting the ambident nucleophilic character of a "nonnucleophilic" anion
(Chemical Equation Presented) Arenediazonium tetrafluoroborate salts undergo metathesis on immobilization in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonato)amide [BMIM][Tf2N]. The "noncoordinating", "nonnucleophilic" [Tf2N] anion acts as an ambident nucleophile toward the aryl cations, formed via thermal dediazoniation, to give predominantly the oxy anion quenching products [ArO-SO(CF3)=NTf], with minimal formation of ArN(Tf)2, irrespective of the nature of the substituent(s) on the ArN2 +. Strong preference for the formation of oxygen trapping products did not change under photolytic conditions, where dediazoniation occurs at room temperature. A minimal amount of the Schiemann product ArF is also formed in both thermal and photolytic dediazoniation, depending on the substituent(s). Progress of dediazoniation in the IL (both thermal and photolytic) and the evolution of the products were directly monitored by 1H and 19F NMR. According to DFT (Density Functional Theory) calculations, PhN(Tf)2 is more stable than PhO-SO(CF3)=NTf by 15-17 kcal/mol, depending on the basis set. Inclusion of solvation effects (PCM, with acetone and with CH2ClCH2Cl as solvent) did not change this preference. The [ArN2][BF4] dediazoniation in [BMIM][Tf2N] resulted in synthesis and characterization of a series of hitherto unknown [ArO-SO(CF3)=NTf] compounds. The X-ray structure of MesO-SO(CF3)=NTf (Mes = mesityl) is reported. On the basis of extraction studies, suitable solvent systems have been identified that remove the products without dissolving [BMIM][NTf2], thus overcoming product recovery difficulties typically associated with the use of this IL.
Laali, Kenneth K.,Okazaki, Takao,Bunge, Scott D.
p. 6758 - 6762
(2008/02/10)

1-Fluoro-2,4,6-trichloro-1,3,5-triazinium tetrafluoroborate: Synthesis, characterization, and ability to effect electrophilic aromatic substitution
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.
p. 229 - 232
(2007/10/03)

A product analytical study of the thermal and photolytic decomposition of some arenediazonium salts in solution
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
p. 789 - 800
(2007/10/03)

Ring fluorination of non-activated aromatic compounds
Unsubstituted aromatic compounds and aromatic compounds having one or more electron-withdrawing substituents are fluorinated, preferably in a nitromethane solvent, by contact with tri(halo- or trifluoromethyl) substituted N-fluorotriazinium salts of the following Formula I: wherein three A moieties are independently CR, where each R is independently halogen or trifluoromethyl; two A moieties are independently Z, where each Z is independently nitrogen or a quaternary nitrogen atom and Y is a counterion or group of counterions which are inert to chemical attack by fluorine. Preferably the cation of the salt is 2,4,6-trichloro-1,3,5-triazinium.
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Page 7

(2008/06/13)

Electrophilic fluorination
N-fluorotriazinium salts, especially those of the following Formula I, are electrophilic fluorinating agents useful in fluorinating, preferably in a nitromethane solvent, carbanionic species and/or activated aromatic compounds:wherein three A moieties are independently CR, where each R is, independently, hydrogen, halogen, (primary, secondary or tertiary) amino, hydroxyl, amino, cyano, perfluorothio hydroxysulphonyl, halosulphonyl, hydrocarbyloxysulphonyl,, or a carbon-containing substituent selected from optionally substituted hydrocarbyl, hydrocarbyloxy, hydrocarbyloxycarbonyl, and hydrocarbylthio groups; two A moieties are independently Z, where each Z is independently nitrogen or a quaternary nitrogen atom and Y is a counterion or group of counterions which are inert to chemical attack by fluorine, and oligomers or polymers thereof in which adjacent triazinium moieties are linked by a common R substituent. Preferably the cation of the salt is 2,4,6-trichloro-1,3,5-triazinium.
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Page 7

(2008/06/13)

Electrophilic nitration of aromatics in ionic liquid solvents
Potential utility of a series of 1-ethyl-3-methylimidazolium salts [emim][X] with X = OTf-, CF3COO-, and NO3- as well as [HNEtPri2][CF3COO] (protonated Huenig's base) ionic liquids were explored as solvent for electrophilic nitration of aromatics using a variety of nitrating systems, namely NH4NO3/TFAA, isoamyl nitrate/BF3·Et2O, isoamyl nitrate/TfOH, Cu(NO3)/TFAA, and AgNO3/Tf2O. Among these, NH4NO3/TFAA (with [emim][CF3COO], [emim][NO3]) and isoamyl nitrate/BF3·Et2O, isoamyl nitrate/TfOH (with [emim][OTf]) provided the best overall systems both in terms of nitration efficiency and recycling/reuse of the ionic liquids. For [NO2][BF4] nitration, the commonly used ionic liquids [emim][AlCl4] and [emim][Al2Cl7] are unsuitable, as counterion exchange and arene nitration compete. [Emim][BF4] is ring nitrated with [NO2][BF4] producing [NO2-emim][BF4] salt, which is of limited utility due to its increased viscosity. Nitration in ionic liquids is surveyed using a host of aromatic substrates with varied reactivities. The preparative scope of the ionic liquids was also extended. Counterion dependency of the NMR spectra of the [emim][X] liquids can be used to gauge counterion exchange (metathesis) during nitration. Ionic liquid nitration is a useful alternative to classical nitration routes due to easier product isolation and recovery of the ionic liquid solvent, and because it avoids problems associated with neutralization of large quantities of strong acid.
Laali,Gettwert
p. 35 - 40
(2007/10/03)

Fluorodediazoniation in ionic liquid solvents: New life for the Balz-Schiemann reaction
Drawbacks associated with the classic Balz-Schiemann reaction are eliminated in a series of examples by conducting fluorodediazoniation in ionic liquid solvents, thus opening up a new horizon for a much in demand process.
Laali, Kenneth K.,Gettwert, Volker J.
p. 31 - 34
(2007/10/03)

Preparation process of fluorine substituted aromatic compound
A preparation process of a fluorine substituted aromatic compound comprising reacting an alkali metal or alkali earth metal salt of an aromatic compound having a hydroxy group with an organic fluorinating agent is disclosed. As a representative fluorinating agent, a bis-dialkylamino-difluoromethane compound, for example, 2,2′-difluoro-1,3-dimethylimidazolidine, is exemplified. According to the process, an industrially useful fluorinated aromatic compound, for example, a fluorobenzene, a fluorine substituted benzophenone, a fluorine substituted diarylsulfone can be prepared with ease in economy without specific equipment.
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(2008/06/13)

Regioselective nitration of arylboronic acids
A convenient and simple regioselective ipso-nitration of arylboronic acids to nitroarenes has been developed. Under certain conditions even dinitro products were isolated.
Salzbrunn,Simon,Prakash,Petasis,Olah
p. 1485 - 1487
(2007/10/03)

The effect of basicity on fluorodenitration reactions using tetramethylammonium salts
The fluorodenitration of several nitroaromatics with tetramethylammonium salts has been found to be dependent on the basicity of the fluorinating species. Tetramethylammonium fluoride is highly basic and is capable of inducing H-D exchange in 1,3-dinitrobenzene, as well as deprotonating N,N- dimethylacetamide. Reaction of the fluoride with phthalic anhydride forms the bifluoride in situ. Tetramethylammonium bifluoride gives higher yields of the required fluoroaromatic, but slower reaction rates than the corresponding fluoride.
Adams, Dave J.,Clark, James H.,Nightingale, David J.
p. 7725 - 7738
(2007/10/03)

Dediazoniation reactions of arenediazonium ions under solvolytic conditions: Fluoride anion abstraction from trifluoroethanol and α-hydrogen atom abstraction from ethanol
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
p. 1971 - 1972
(2007/10/03)

The thermodynamics of m-fluoroaniline and of the proton ionization of m-fluoroanilinium ion: A solvent extraction study
The distribution coefficients of m-fluoroaniline between a petroleum ether fraction and aqueous sodium chloride solutions were determined at different temperatures. The activity coefficients of the amine in aqueous sodium chloride solutions, and the salting coefficients were determined at different temperatures. The results agree with the Debye theory of salt effects. The effect of sodium chloride on the proton ionization of m-fluoroanilinium was studied at different temperatures, by a modified distribution method. Attention was directed to the choice of the extracting solvent, the purity of the amine, and the analytical method. Km, Ko, (Kb)m, (Kb)o, ΔGo, ΔHo and ΔSo were evaluated for the proton ionization of the m-fluoroanilinium ion.
Aboul-Seoud,Salama
p. 19 - 24
(2007/10/03)

Tetramethylammonium hydrogendifluoride: A convenient source of nucleophilic fluoride
Tetramethylammonium hydrogendifluoride (TMAHF2) acts as an effective fluoride source for the selective fluorination in high yields of various chloro and nitroaromatics via halogen exchange (halex) and fluorodenitration.
Adams, David J.,Clark, James H.,Nightingale, David J.
p. 4295 - 4301
(2007/10/03)

Facile preparation of aromatic fluorides by deaminative fluorination of aminoarenes using hydrogen fluoride combined with bases
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
p. 23 - 36
(2007/10/02)

SELECTIVITY OF NITRATION REACTIONS OF AROMATIC COMPOUNDS ON ZEOLITES H-Y AND H-ZSM-11
Substrate and positional selectivity in the nitration reaction of benzene and its derivatives (halobenzenes, toluene and o-xylene) by nitric acid and acyl nitrates supported on zeolites H-Y and H-ZSM-11 were studied.The reaction mechanism and effects governing selectivity of the process are discussed.
Nagy, Sandor M.,Yarovoy, Konstantin A.,Shubin, Vyacheslav G.,Vostrikova, Lidiya A.
p. 385 - 393
(2007/10/02)

Resonance Electron Capture Rate Constants for Substituted Nitrobenzenes
We report here a new method for the determination of electron capture (EC) rate constants that utilizes a pulsed electron beam mass spectrometer.The method is first tested by measurements of the known dissociative electron capture rate constants for several halogenated methanes that have been extensively studied by other techniques.The resonance electron capture (REC) rate constants of nitrobenzene (NB) and 23 substituted nitrobenzenes (SNB's) are then determined for the first time at 125 deg C in 10 Torr of methane buffer gas.The SNB's studied here include several sets of closely related structural isomers whose electron affinities (EA's) have been previously determined.It is shown that the REC rate constants of these compounds bear little systematic relationship with the EA's of these compounds.The REC rate constants of the SNB's are also compared with other previously reported characteristics associated with the negative ionization of these compounds, including their entropies of negative ionization, the lifetimes against autodetachment of their initially formed molecular anions, and the rates of autodetachment from electronically excited states of their molecular anions.
Knighton, W. B.,Mock, R. S.,McGrew, D. S.,Grimsrud, E. P.
p. 3770 - 3776
(2007/10/02)

Process for the synthesis of fluorinated derivatives
A process for the synthesis of fluorinated organic compounds and a reagent suitable for use in the process. The process is carried out by exchange with fluorides, while preferably agitating the reaction medium with ultrasonic sound.
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(2008/06/13)

Electron Affinities of Naphthalene, Anthracene and Substituted Naphthalenes and Anthracenes
The determination of electron transfer equilibria A(1-) + B = A + B(1-) in the gas phase, with a pulsed-electron high-pressure mass spectrometer, leads to ΔG10, ΔH10, and ΔS10 values.These can be converted into the free energy, enthalpy and entropy changes, ΔGa0(B), ΔHa0(B) and ΔSa0(B), for the reaction e + B = B(1-), since the corresponding values for the reference compounds A are known.Results were obtained for 18 substituted naphthalenes, anthracene and substituted anthracenes.The results are compared with some theoretical predictions and the corresponding reduction potentials in solution.Rate constants for 13 exoergic electron-transfer reactions were also measured.These were found to be close to the ADO collision rates.
Heinis, Thomas,Chowdhury, Swapan,Kebarle, Paul
p. 358 - 365
(2007/10/02)

Facile conversion of arenediazonium salts to the corresponding fluoroarenes using boron trifluoride diethyl ether complex
The conversion of various arenediazonium salts 1 to the corresponding fluoroarenes 2 has been achieved in good yields under mild conditions in boron trifluoride diethyl ether complex.
Shinhama,Aki,Furuta,Minamikawa
p. 1577 - 1582
(2007/10/02)

Fluorodenitrations using Tetramethylammonium Fluoride
Tetramethylammonium fluoride activated by azeotropic drying in situ is an efficient reagent for the fluorodenitration of nitroaromatics.
Boechat, Nubia,Clark, James H.
p. 921 - 922
(2007/10/02)

A new synthesis of aryl fluorides: The reaction of caesium fluoroxysulfate with arylboronic acids and derivatives
The ipso fluorination of arylboronic acids and some derivatives with caesium fluoroxysulfate has been developed. The reaction proceeds with the wide range of functionalised aromatics and is strongly solvent dependent.
Diorazio,Widdowson,Clough
p. 8073 - 8088
(2007/10/02)

Kinetic models for gas-phase electron-transfer reactions between nitrobenzenes
Rate constants for gas-phase electron-transfer reactions between substituted nitrobenzenes have been measured using ion cyclotron resonance spectroscopy. On the basis of the assumption that these reactions occur through the formation of an intermediate complex, a statistical model is used to interpret the reaction kinetics. The intersecting parabolas quantum mechanical model provides an alternative description of the energy surface. Energy barriers are found to be consistent for the two methods. The results for exothermic reactions are consistent with a Marcus theory analysis, but suggest that a zero-order potential energy surface may not be completely adequate for quantitative prediction of reaction rates.
Han, Chau-Chung,Wilbur, James L.,Brauman, John I.
p. 887 - 893
(2007/10/02)

Lewis Acid Mediated Fluorinations of Aromatic Substrates
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.
p. 142 - 145
(2007/10/02)

Synthesis of Aromatic Fluoro Compounds by Nucleophilic Exchange of Nitro Groups by Fluoride
The synthesis of aromatic fluoro compounds from the respective nitro compounds by nucleophilic substitution of nitrite by fluoride is described.Reasonable yields in case of nonactivated nitro compounds are only obtained if the nitrite formed in the reaction is eliminated by acylation. 1-Fluoro-3-nitrobenzene (2) was obtained from 1,3-dinitrobenzene (1), and 1-fluoro-3,5-dinitrobenzene (9) as well as 1,3-difluoro-5-nitrobenzene (10) from 1,3,5-trinitrobenzene (8) in yields up to 92percent by reaction of nitro compounds with potassium fluoride in sulfolane at 180-200 deg C in the presence of phthaloyl dichloride (6); 1,2-difluoro-4-nitrobenzene (12) was formed in 58percent yield from 2,4-dinitro-1-fluorobenzene (11) in the presence of pyromellitoyl tetrachloride (13).
Effenberger, Franz,Streicher, Willi
p. 157 - 162
(2007/10/02)

A General Procedure for the Fluorodenitration of Aromatic Substrates
The synthesis of several fluoroaromatic compounds by a new procedure of fluorodenitration of nitroarenes is reported.The methodology is based on the principle that the nitrite ion, generated during the fluorodenitration processes and responsible for most of the undesired side reactions, can be trapped with a suitable reagent, e.g., phthaloyl difluoride or tetrafluorophthaloyl difluoride.The yields of fluoro compounds thus obtained are good to excellent, and the procedure is of general application.
Maggini, Michele,Passudetti, Margherita,Gonzales-Trueba, Guadalupe,Prato, Maurizio,Quintily, Ugo,Scorrano, Gianfranco
p. 6406 - 6411
(2007/10/02)

General and Highly Efficient Syntheses of m-Fluoro Arenes Using Potassium Fluoride-Exchange Method
Tetraphenylphosphonium bromide was found to be a suitable catalyst for the reaction of m-nitroaryl derivatives carrying cyano, nitro, chlorocarbonyl, trifluoromethyl, and chlorosulfonyl groups with potassium fluoride in the presence of a stoichiometric amount of phthaloyl dichloride, giving the corresponding m-fluoro aromatic derivatives in good yields.The catalyst was also found to be efficient for the fluorodesulfonylation of m-(fluorosulfonyl)aryl derivatives to afford m-fluoro arenes by the use of a reaction-distillation technique.
Suzuki, Hiroshi,Yazawa, Naoto,Yoshida, Yasuo,Furusawa, Osamu,Kimura, Yoshikazu
p. 2010 - 2017
(2007/10/02)

PREPARATION OF AROMATIC FLUORIDES VIA DIAZOTIZATION AND PHOTOCHEMICALLY INDUCED FLUORO-DEDIAZONIATION OF AROMATIC AMINES IN ANHYDROUS HYDROGEN FLUORIDE - ORGANIC BASE SOLUTIONS
Fluoro-dediazoniation of aromatic diazonium ions, produced by the diazotization of the corresponding aromatic amines with NaNO2 in anhydrous hydrogen fluorides (AHF) - organic base solutions, was accelerated photochemically to afford Ar-F efficiently in AHF - organic base solutions in situ.
Yoneda, Norihiko,Fukuhara, Tsuyoshi,Kikuchi, Tetsuo,Suzuki, Akira
p. 865 - 872
(2007/10/02)

Tetraphenylphosphonium Bromide Catalyzed Fluorodenitrations and Fluorodesulfonylations. Efficient Syntheses of m-Fluoroaromatic Compounds
Meta-fluoroaromatic compounds were effectively synthesized from m-nitroaromatic or m-fluorosulfonylaromatic compounds by replacement reaction with potassium fluoride in the presence of a catalytic amount of tetraphenylphosphonium bromide.
Yazawa, Naoto,Suzuki, Hiroshi,Yoshida, Yasuo,Furusawa, Osamu,Kimura, Yoshikazu
p. 2213 - 2216
(2007/10/02)

Vastly Improved Para Preference in the Nitration of Halobenzenes
The halobenzenes are monitrated with cupric nitrate supported on the K10 montmorillonite in the presence of acetic anhydride, in hexane, or in the methylene chloride, at room temperature or below.Good isolated yields (50-75percent) are accompanied by much improved para selectivities, up to a para-to-ortho ratio of 35 (a selectivity factor of 70) for fluorobenzene.The observed selectivity factors are determined uniquely by the polarizability of the halogen substituent.
Laszlo, Pierre,Pennetreau, Pascal
p. 2407 - 2410
(2007/10/02)

Electrophilic Aromatic Nitration in the Gas Phase
Aromatic nitration by MeO+(H)NO2, in essence nitronium ion solvated by one methanol molecule, has been studied in the gas phase by using an integrated approach, based on the coordinate application of ICR, Cl, and CID mass spetrometric methods with a highly complementary radiolytic technique.The latter can be used in gases at atmospheric pressure and allows direct evaluation of key mechanistic features, in particular of substrate and positional selectivity.The results resolve early discrepancies between gas-phase and liquid-phase studies, characterizing the reaction as a typical, well-behaved electrophilic substitution of moderate selectivity.The date from the gas-phase nitration of ten monosubstituted benzenes fit a Hammett's type linear plot, characterized by a ρ value of -3.87.The correlation does not extend to highly activated substrates, such as anisole and mesitylene, since the nitration rate tends to a limiting value that cannot be increased by further enhancing the activation of the substrate, exactly as in "encounter-rate" nitrations occurring in solution.The mechanism and the energetics of the gas-phase nitration have been investigated, and the relative stability of the charged intermediates involved, in particular of the isomeric protonated nitrobenzenes, has been estimated by theoretical approaches at two different levels, using STO-3G minimal basis and 4-31G split-valence basis sets.
Attina, Marina,Cacace, Fulvio,Yanez, Manuel
p. 5092 - 5097
(2007/10/02)

AN IMPROVED PROCEDURE FOR DIAZOTIZATION FLUORODEDIAZONIATION OF ANILINES USING ORGANIC BASE-HF AGENTS
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Fukuhara, Tsuyoshi,Yoneda, Norihiko,Sawada, Teiken,Suzuki, Akira
p. 685 - 692
(2007/10/02)