- Mixed Micelles of Surface Active Ionic Liquid (SAIL)–Octylphenol Ethoxylate: A Novel Reaction Medium for Selective Oxidation of Toluene to Benzaldehyde
-
Ionic liquids have been found to be suitable alternatives to volatile organic solvents in chemical transformation. Through a proper choice of cations and anions, the properties of an ionic liquid can be tuned so that it resembles an amphiphile. Such specially designed molecules are known as surface-active ionic liquids (SAIL). Like conventional surfactants, SAIL also form aggregates in an aqueous medium. Studies show that the mixing of SAIL with conventional surfactants leads to synergistic micellization. However, very few reports are available on the application of such systems as reaction media. Present study focuses on the application of mixed micelles of 1-tetradecyl-3-methylimidazol-1-ium bromide, ([C14mim]Br) with nonionic surfactant, Octylphenol ethoxylate with 10 moles of ethylene oxide (OPE-10). Enhanced solubilization and selective catalytic oxidation of toluene using hydrogen peroxide as an oxidant and tungstic acid as a catalyst have been studied in detail using this system.
- Deore, Tushar S.,Sadgar, Amid L.,Jayaram, Radha V.
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p. 185 - 190
(2020/07/30)
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- Eco-Friendly Methodology for the Formation of Aromatic Carbon–Heteroatom Bonds by Using Green Ionic Liquids
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A new sustainable method is reported for the formation of aromatic carbon–heteroatom bonds under solvent-free and mild conditions (no co-oxidant, no strong acid and no toxic reagents) by using a new type of green ionic liquid. The bromination of methoxy arenes was chosen as a model reaction. The reaction methodology is based on only using natural sodium bromine, which is transformed into an electrophilic brominating reagent within an ionic liquid, easily prepared from the melted salt FeCl3 hexahydrate. Bromination reactions with this in-situ-generated reagent gave good yields and excellent regioselectivity under simple and environmentally friendly conditions. To understand the unusual bromine polarity reversal of sodium bromine without any strong oxidant, the molecular structure of the reaction medium was characterised by Raman and direct infusion electrospray ionisation mass spectroscopy (ESI-MS). An extensive computational investigation using density functional theory methods was performed to describe a mechanism that suggests indirect oxidation of Br? through new iron adducts. The versatility of the methodology was successively applied to nitration and thiocyanation of methoxy arenes using KNO3 and KSCN in melted hexahydrated FeCl3.
- Richards, Kenza,Petit, Eddy,Legrand, Yves-Marie,Grison, Claude
-
supporting information
p. 809 - 814
(2020/11/30)
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- Bipyridinium and Phenanthrolinium Dications for Metal-Free Hydrodefluorination: Distinctive Carbon-Based Reactivity
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The development of novel Lewis acids derived from bipyridinium and phenanthrolinium dications is reported. Calculations of Hydride Ion Affinity (HIA) values indicate high carbon-based Lewis acidity at the ortho and para positions. This arises in part from extensive LUMO delocalization across the aromatic backbones. Species [C10H6R2N2CH2CH2]2+ (R=H [1 a]2+, Me [1 f]2+, tBu [1 g]2+), and [C12H4R4N2CH2CH2]2+ (R=H [2 a]2+, Me [2 b]2+) were prepared and evaluated for use in the initiation of hydrodefluorination (HDF) catalysis. Compound [2 a]2+ proved highly effective towards generating catalytically active silylium cations via Lewis acid-mediated hydride abstraction from silane. This enabled the HDF of a range of aryl- and alkyl- substituted sp3(C?F) bonds under mild conditions. The protocol was also adapted to effect the deuterodefluorination of cis-2,4,6-(CF3)3C6H9. The dications are shown to act as hydride acceptors with the isolation of neutral species C16H14N2 (3 a) and C16H10Me4N2 (3 b) and monocationic species [C14H13N2]+ ([4 a]+) and [C18H21N2]+ ([4 b]+). Experimental and computational data provide further support that the dications are initiators in the generation of silylium cations.
- Burton, Katherine I.,Elser, Iris,Waked, Alexander E.,Wagener, Tobias,Andrews, Ryan J.,Glorius, Frank,Stephan, Douglas W.
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supporting information
p. 11730 - 11737
(2021/07/16)
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- Preparation method of monobrominated aromatic hydrocarbon compound
-
The invention discloses a preparation method of a monobrominated aromatic hydrocarbon compound, which comprises the following steps: by using an aromatic hydrocarbon compound as a raw material, wateras a solvent and liquid bromine as a bromine source, reacting at room temperature for 4.5 hours, and after the reaction is finished, carrying out aftertreatment on the obtained reaction mixed solutionto obtain the monobrominated target product. According to the method, a high-selectivity bromination method is realized on the aromatic hydrocarbon compound under the action of water, and the monobrominated aromatic hydrocarbon compound is prepared. The method is high in reaction applicability, mild in condition, high in yield, green and environment-friendly.
- -
-
Paragraph 0055-0067
(2020/11/23)
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- Induced Fitting and Polarization of a Bromine Molecule in an Electrophilic Inorganic Molecular Cavity and Its Bromination Reactivity
-
Dodecavanadate, [V12O32]4? (V12), possesses a 4.4 ? cavity entrance, and the cavity shows unique electrophilicity. Owing to the high polarizability, Br2 was inserted into V12, inducing the inversion of one of the VO5 square pyramids to form [V12O32(Br2)]4? (V12(Br2)). The inserted Br2 molecule was polarized and showed a peak at 185 cm?1 in the IR spectrum. The reaction of V12(Br2) and toluene yielded bromination of toluene at the ring, showing the electrophilicity of the inserted Br2 molecule. Compound V12(Br2) also reacted with propane, n-butane, and n-pentane to give brominated alkanes. Bromination with V12(Br2) showed high selectivity for 3-bromopentane (64 %) among the monobromopentane products and preferred threo isomer among 2-,3-dibromobutane and 2,3-dibromopenane. The unique inorganic cavity traps Br2 leading the polarization of the diatomic molecule. Owing to its new reaction field, the trapped Br2 shows selective functionalization of alkanes.
- Hayashi, Yoshihito,Inada, Yasuhiro,Katayama, Misaki,Kikukawa, Yuji,Kitajima, Hiromasa,Seto, Kensuke,Watanabe, Daiki,Yamashita, Shohei
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supporting information
p. 14399 - 14403
(2020/07/13)
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- Metal- and base-free synthesis of aryl bromides from arylhydrazines
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An efficient method was developed to synthesize brominated aromatic compounds from arylhydrazine hydrochlorides by using BBr3 in DMSO/CPME (cyclopentyl methyl ether) under air at 80 °C for 1 h without the use of bases or metal catalysts. In particular, this method could be carried out satisfactorily using electron-withdrawing groups to afford aryl bromides in a moderate to excellent yields.
- Phuc Tran, Dat,Nomoto, Akihiro,Mita, Soichiro,Dong, Chun-ping,Kodama, Shintaro,Mizuno, Takumi,Ogawa, Akiya
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supporting information
(2020/05/08)
-
- Mild and Regioselective Bromination of Phenols with TMSBr
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In this work, an unexpected promoting effect of by-product thioether was observed, leading to a mild and regioselective bromination of phenols with TMSBr. This method can tolerate a series of functional groups such as the reactive methoxyl, amide, fluoro, chloro, bromo, aldehyde, ketone and ester groups, and has the potential to recycle the by-product thioether and isolate the desired product under column chromatography-free conditions. Mechanism studies revealed that O–H···S hydrogen bond may be formed between phenol and by-product thioether. Possibly owing to the steric hindrance effect from by-product thioether, the electrophilic bromination at para-position of phenols is much favorable.
- Ma, Xiantao,Yu, Jing,Jiang, Mengyuan,Wang, Mengyu,Tang, Lin,Wei, Mengmeng,Zhou, Qiuju
-
supporting information
p. 4593 - 4596
(2019/07/05)
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- Ni-Catalyzed Reductive Cyanation of Aryl Halides and Phenol Derivatives via Transnitrilation
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Herein, we report a Ni-catalyzed reductive coupling for the synthesis of benzonitriles from aryl (pseudo)halides and an electrophilic cyanating reagent, 2-methyl-2-phenyl malononitrile (MPMN). MPMN is a bench-stable, carbon-bound electrophilic CN reagent that does not release cyanide under the reaction conditions. A variety of medicinally relevant benzonitriles can be made in good yields. Addition of NaBr to the reaction mixture allows for the use of more challenging aryl electrophiles such as aryl chlorides, tosylates, and triflates. Mechanistic investigations suggest that NaBr plays a role in facilitating oxidative addition with these substrates.
- Mills, L. Reginald,Graham, Joshua M.,Patel, Purvish,Rousseaux, Sophie A. L.
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p. 19257 - 19262
(2019/12/02)
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- Preparation methods of 3,6-dichloro-2-bromotoluene and dicamba
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The invention provides a preparation method of dicamba. The preparation method comprises the following steps: S1) in the presence of a catalyst, 2-bromotoluene is subjected to a chlorination reactionin chlorosulfonic acid or concentrated sulfuric acid, and 3,6-dichloro-2-bromotoluene is obtained; S2), 3,6-dichloro-2-bromotoluene is subjected to an oxidation reaction and a methoxylation reaction in sequence, and dicamba is obtained. Compared with the prior art, 3,6-dichloro-2-bromotoluene is obtained from 2-bromotoluene after the directional chlorination reaction, and dicamba can be obtained by the oxidation reaction and the methoxylation reaction. The methods have the advantages of easily available raw materials, low comprehensive cost, high methoxylation reaction selectivity, high totalyield, stable product quality and simple process, and facilitate industrial implementation.
- -
-
Paragraph 0033; 0041; 0042; 0046; 0047; 0054; 0055
(2019/06/05)
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- Regioselective Halogenation of Arenes and Heterocycles in Hexafluoroisopropanol
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Regioselective halogenation of arenes and heterocycles with N-halosuccinimides in fluorinated alcohols is disclosed. Under mild condition reactions, a wide diversity of halogenated arenes are obtained in good yields with high regioselectivity. Additionally, the versatility of the method is demonstrated by the development of one-pot sequential halogenation and halogenation-Suzuki cross-coupling reactions.
- Tang, Ren-Jin,Milcent, Thierry,Crousse, Benoit
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p. 930 - 938
(2018/01/28)
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- Visible-Light-Driven Oxidative Mono- and Dibromination of Benzylic sp 3 C-H Bonds with Potassium Bromide/Oxone at Room Temperature
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Benzylic sp 3 C-H bonds have been successfully brominated with potassium bromide by using Oxone as an oxidant in water/dichloromethane under visible light at room temperature. Toluene, ethylbenzene and other alkylbenzenes bearing an electron-withdrawing group, such as Br, Cl, COMe, CO 2 Et, CO 2 H, CN or NO 2, provide the corresponding benzylic monobromides in good to excellent yields in this reaction. Dibromides can also be produced in the presence of excess potassium bromide in a prolonged reaction time. Control of the illuminance of visible light (~500 lux) is crucial to achieving both high yield and high selectivity in these brominations. Mono- and difluorides can be conveniently prepared through nucleophilic substitutions of the benzylic bromides with potassium fluoride.
- Zhao, Mengdi,Li, Meiqi,Lu, Wenjun
-
supporting information
p. 4933 - 4939
(2018/12/14)
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- Catalytic Bromination of Alkyl sp3C-H Bonds with KBr/Air under Visible Light
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Alkyl sp3C-H bonds of cycloalkanes and functional branch/linear alkanes have been successfully brominated with KBr using air or O2 as an oxidant at room temperature to 40 °C. The reactions are carried out in the presence of catalytic NaNO2 in 37% HCl (aq)/solvent under visible light, combining aerobic oxidations and photochemical radical processes. For various alkane substrates, CF3CH2OH, CHCl3, or CH2Cl2 is employed as an organic solvent, respectively, to enhance the efficiency of bromination.
- Zhao, Mengdi,Lu, Wenjun
-
supporting information
p. 5264 - 5267
(2018/09/12)
-
- Ultrasonically assisted halogenation of aromatic compounds using isoquinolinium bound hypervalent chromium and tetrabutylammonium halides in PEG-600 solutions under acid free and solvent-free conditions
-
Isoquinolinium bound Cr(VI) reagents like isoquinolinium dichromate (IQDC) and isoquinolinium chlorochromate (IQCC) have been successfully accomplished as efficient reagents for oxidative halogenation of aromatic compounds using tetrabutylammonium halide (TBAX) as halogenating agents in aqueous polyethylene glycol (PEG-600) under acid free conditions. Tetrabutylammonium bromide (TBAB) has been used for bromination and tetrabutylammonium iodide (TBAI) for iodination. The halogenation reactions that occurred smoothly in 2 to 7 h under conventional conditions are accelerated magnificently under sonication with few minutes (25 to 70 min) of reaction time and fairly good yields. The reactions occurred at moderate temperature under mild and environmentally safe conditions with simple work up.
- Sambashiva Rao,Ramesh, Kola,Rajanna,Chakrvarthi
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p. 1892 - 1896
(2018/07/10)
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- Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage-Independent Activation of Strong C-O Bonds
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Despite the prevalence of alcohols and carboxylic acids as functional groups in organic molecules and the potential to serve as radical precursors, C-O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen-centered nucleophile. We show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H atom trapping to afford the deoxygenated products. Using the same method, we demonstrate access to synthetically versatile acyl radicals, which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge C-O, C-N, and C-C bonds in a single step.
- Stache, Erin E.,Ertel, Alyssa B.,Rovis, Tomislav,Doyle, Abigail G.
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p. 11134 - 11139
(2018/11/21)
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- Transition-metal-free decarboxylative bromination of aromatic carboxylic acids
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Methods for the conversion of aliphatic acids to alkyl halides have progressed significantly over the past century, however, the analogous decarboxylative bromination of aromatic acids has remained a longstanding challenge. The development of efficient methods for the synthesis of aryl bromides is of great importance as they are versatile reagents in synthesis and are present in many functional molecules. Herein we report a transition metal-free decarboxylative bromination of aromatic acids. The reaction is applicable to many electron-rich aromatic and heteroaromatic acids which have previously proved poor substrates for Hunsdiecker-type reactions. In addition, our preliminary mechanistic study suggests that radical intermediates are not involved in this reaction, which is in contrast to classical Hunsdiecker-type reactivity. Overall, the process demonstrates a useful method for producing valuable reagents from inexpensive and abundant starting materials.
- Quibell, Jacob M.,Perry, Gregory J. P.,Cannas, Diego M.,Larrosa, Igor
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p. 3860 - 3865
(2018/04/26)
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- Reactivity of alkali and alkaline earth metal tetrafluorobromates towards aromatic compounds and pyridine
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The bromination activity of tetrafluorobromates of alkali and alkali-earth metals increases in the order KBrF4, CsBrF4, RbBrF4and Ba(BrF4)2. The most active tetrafluorobromate—Ba(BrF4)2is able to selectively brominate the deactivated aromatic compounds nitrobenzene and 4-nitrotoluene, but not the activated compounds benzene and toluene. In all cases bromination of methyl groups of methylbenzenes does not occur. Ba(BrF4)2forms the known complex C6H5N·BrF3when reacted with pyridine. Due to dilution by inert BaF2, this pyridine-based complex is air stable and can be considered as safer and more convenient reagent in comparison with the original fluorobromates; it can selectively brominate benzene and toluene in contrast with tetrafluorobromates.
- Sobolev, Vasily I.,Filimonov, Victor D.,Ostvald, Roman V.,Radchenko, Vyacheslav B.,Zherin, Ivan I.
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p. 120 - 123
(2016/11/17)
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- Isoquinolinium Dichromate and Chlorochromate as Efficient Catalysts for Oxidative Halogenation of Aromatic Compounds under Acid-Free Conditions
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Isoquinolinium dichromate and isoquinolinium chlorochromate were found as efficient catalysts to trigger oxidative bromination and iodination of aromatic hydrocarbons with KBr/KI and KHSO4 under acid-free conditions. Reaction times reduced highly significantly under sonication, followed by corresponding mono bromo derivatives in very good yield with high regioselectivity.
- Rao, A. Sambashiva,Rajanna,Reddy, K. Rajendar,Kulkarni, Subhash
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p. 832 - 837
(2016/02/12)
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- Sono-bromination of aromatic compounds based on the ultrasonic advanced oxidation processes
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A novel, mild "sono-halogenation" of various aromatic compounds with potassium halide was investigated under ultrasound in a biphasic carbon tetrachloride/water medium. The feasibility study was first undertaken with the potassium bromide and then extended to chloride and iodide analogues. This methodology could be considered as a new expansion of the ultrasonic advanced oxidation processes (UAOPs) into a synthetic aspect as the developed methodology is linked to the sonolytic disappearance of carbon tetrachloride. Advantages of the present method are not only that the manipulation of the bromination is simple and green, but also that the halogenating agents used are readily available, inexpensive, and easy-handling.
- Fujita, Mitsue,Lévêque, Jean-Marc,Komatsu, Naoki,Kimura, Takahide
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p. 247 - 251
(2015/06/08)
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- Preparation of an Arenylmethylzinc Reagent with Functional Groups by Chemoselective Cross-Coupling Reaction of Bis(iodoazincio)methane with Iodoarenes
-
Palladium-catalyzed cross-coupling reaction of bis(iodozincio)methane with iodoarenes carrying various functionalities such as ester, boryl, cyano, and halo groups proceeded chemoselectively to give the corresponding arenylmethylzinc species efficiently. The moderate reactivity of the gem-dizinc reagent imparted functional group tolerance to the process. The transformations from iodoheteroarenes were also performed; in the case of iodopyridine derivatives, the nickel-catalyzed reaction gave the corresponding organozinc species efficiently. The obtained arenylmethylzinc species underwent the copper-mediated coupling reaction with a range of organic halides.
- Shimada, Yukako,Haraguchi, Ryosuke,Matsubara, Seijiro
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p. 2395 - 2398
(2015/10/19)
-
- On the ionizing properties of supercritical carbon dioxide: Uncatalyzed electrophilic bromination of aromatics
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Supercritical carbon dioxide (scCO2), a solvent with a zero dipole moment, low dielectric constant, and no hydrogen bonding behavior, is a suitable medium to perform the uncatalyzed electrophilic bromination of weakly activated aromatics with no interference of radical pathways. The ability of scCO2 to promote these reactions matches those of strongly ionizing solvents such as aqueous acetic and trifluoroacetic acids. Conversely, carbon tetrachloride, with similar polarity parameters to scCO2, leads exclusively to side chain functionalization. The strong quadrupole moment, and the acidic, but non basic, Lewis character of carbon dioxide, are proposed as key factors for the singular performance of scCO2 in reactions involving highly polar and ionic intermediates.
- Delgado-Abad, Thais,Martnez-Ferrer, Jaime,Reig-Lpez, Javier,Mello, Rossella,Acerete, Rafael,Asensio, Gregorio,Gonzlez-Nez, Mara Elena
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p. 51016 - 51021
(2015/01/16)
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- Practical and metal-free electrophilic aromatic halogenation by interhalogen compounds generated in situ from N-halosuccinimide and catalytic TMSCL
-
Halomonochloride compounds (ClCl, BrCl, ICl) generated in situ from N-halosuccinimide and catalytic chlorotrimethylsilane (TMSCl, 0.1 equiv) can efficiently halogenate aromatic compounds to give halogenated products in good to excellent yields and selectivities. The reaction can be carried out at room temperature or at lower temperatures, requires only one hour, is practical to apply to a wide range of substrates, and provides a simple access to a variety of haloarene compounds. Georg Thieme Verlag Stuttgart New York.
- Maibunkaew, Tapanee,Thongsornkleeb, Charnsak,Tummatorn, Jumreang,Bunrit, Anon,Ruchirawat, Somsak
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supporting information
p. 1769 - 1775
(2014/08/05)
-
- A sustainable process for catalytic oxidative bromination with molecular oxygen
-
Workin′ in a bromine: A palladium-polyoxometalate amphiphilic hybrid material serves as catalyst for oxidative brominations. The emulsion-based process avoids the use of toxic and corrosive bromination agents such as Br 2 or HBr, and uses molecular oxygen as oxidant. The only side product is water, which is also the reaction medium. The catalyst offers good recoverability and recyclability. Copyright
- Huang, Zhijun,Li, Fengbo,Chen, Bingfeng,Lu, Tao,Yuan, Yin,Yuan, Guoqing
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p. 1337 - 1340
(2013/09/12)
-
- Bronsted acidic ionic liquid accelerated halogenation of organic compounds with N-halosuccinimides (NXS)
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The Bronsted-Acidic ionic liquid 1-methyl-3-(4-sulfobutyl) imidazolium triflate [BMIM(SO3H)][OTf] was demonstrated to act efficiently as solvent and catalyst for the halogenation of activated organic compounds with N-halosuccinimides (NXS) under mild conditions with short reaction times. Methyl aryl ketones were converted into a-halo and a,a-dihaloketones, depending on the quantity of NXS used. Ketones with activated aromatic rings were selectively halogenated, however in some cases mixtures of a-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO3H)][OTf] ionic liquid (IL-A) was successfully reused eight times in a representative monohalogenation reaction with no noticeable decrease in efficiency. An effective halogenation scale-up in this IL is also presented. The reactivity trend and the observed chemo- and regioselectiivities point to an ET process in these IL-promoted halofunctionalization reactions.
- Vrazic, Dejan,Jereb, Marjan,Laali, Kenneth K.,Stavber, Stojan
-
-
- A new recoverable Au(III) catalyst supported on magnetic polymer nanocomposite for aromatic bromination
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This Letter presents a facile alternative synthesis of a recoverable Au(III) catalyst supported on Fe3O4@SiO 2~MPS grafted by poly(N-vinyl-2-pyrrolidone) (PVP). The solid magnetic support was prepared by anchoring 3-methacryloxypropyltrimethoxysilane (MPS) onto the Fe3O4@SiO2 surfaces followed by free radical polymerization with N-vinyl-2-pyrrolidone. Au(III) was immobilized onto the magnetic support in aqueous media to afford Au(III)/Fe 3O4@SiO2~PVP (catalyst 1). Catalyst 1 was characterized by FT-IR, TEM, VSM, TGA, XRD, and ICP-AES. The amount of Au in catalyst 1 was measured to be 0.64 wt % by ICP-AES. This newly prepared catalyst can catalyze the aromatic bromination reaction with comparable activity as homogeneous AuCl3. Moreover, the supported catalyst is easy to recover and can be used in four cycles without apparent loss of activity.
- Li, Bai,Gao, Linfeng,Bian, Fengling,Yu, Wei
-
supporting information
p. 1063 - 1066
(2013/04/10)
-
- Metal and H2O2 free aerobic oxidative aromatic halogenation with [RNH3+] [NO3-]/HX and [BMIM(SO3H)][NO3)x(X)y] (X = Br, Cl) as multifunctional ionic liquids
-
Novel multifunctional ionic liquids (ILs) are generated by addition of HBr or HCl to alkylammonium nitrates ([RNH3+] [NO 3-]) and to 3-methyl-1-(butyl-4-sulfonyl)imidazolium nitrate ([BMIM(SO3H)][NO3]). The resulting [RNH 3+] [NO3-]/HX and mono (3-methyl-1-(butyl-4-sulfonyl)imidazolium) monohalogenide mononitrate ([BMIM(SO3H)][NO3)x(X)y] (X = Br, Cl)) systems act as solvent and promoter for aerobic oxidative halogenation of arenes under mild conditions in high yields that can be repeated over several cycles.
- Prebil, Rok,Laali, Kenneth K.,Stavber, Stojan
-
supporting information
p. 2108 - 2111
(2013/06/05)
-
- A sustainable two-phase procedure for V-catalyzed toluene oxidative bromination with H2O2-KBr
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A sustainable V(v) and Mo(vi) catalysed two-phase procedure for bromination of toluene under quite mild conditions is proposed; H2O2 is the primary oxidant and KBr is the bromine source; metal precursors are commercially available salts. The reaction is efficient without any additional solvent. By using PhCH3 as a solvent/substrate good yields, together with interesting selectivity toward the formation of PhCH2Br, are obtained with both metal ions. Recycling of the catalytic phase is also possible. Useful information on the V-peroxido chemistry was obtained. The Royal Society of Chemistry.
- Galloni, Pierluca,Mancini, Marco,Floris, Barbara,Conte, Valeria
-
supporting information
p. 11963 - 11970
(2013/09/02)
-
- Silver catalyzed bromination of aromatics with N-bromosuccinimide
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A heterogeneous silver catalyst was prepared and applied efficiently for the selective bromination of aromatics with NBS. The silver nanoparticles combined with the acidic support HMB can activate both the aromatic ring and NBS, and the synergistic effects between the silver nanoparticles and the HMB highly enhanced the efficiency of the bromination reaction.
- Zhang, Rui,Huang, Lei,Zhang, Yanfang,Chen, Xiaorong,Xing, Weihong,Huang, Jun
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experimental part
p. 378 - 383
(2012/06/18)
-
- Bromination of aromatic compounds using an Fe2O 3/zeolite catalyst
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The catalytic bromination of non-activated aromatic compounds has been achieved using an Fe2O3/zeolite catalyst system. FeBr 3 was identified as the catalytic species, formed in situ from HBr and Fe2O3. The catalyst was easy-to-handle and cost effective and could also be recycled. The reaction system was also amenable to the one-pot sequential bromination/C-C bond formation of benzene.
- Nishina, Yuta,Takami, Keishi
-
supporting information
p. 2380 - 2383
(2013/02/21)
-
- Aromatic substitution in ball mills: Formation of aryl chlorides and bromides using potassium peroxomonosulfate and NaX
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Aryl chlorides and bromides are formed from arenes in a ball mill using KHSO5 and NaX (X = Cl, Br) as oxidant and halogen source, respectively. Investigation of the reaction parameters identified operating frequency, milling time, and the number of milling balls as the main influencing variables, as these determine the amount of energy provided to the reaction system. Assessment of liquid-assisted grinding conditions revealed, that the addition of solvents has no advantageous effect in this special case. Preferably activated arenes are halogenated, whereby bromination afforded higher product yields than chlorination. Most often reactions are regio- and chemoselective, since p-substitution was preferred and concurring side-chain oxidation of alkylated arenes by KHSO5 was not observed. The Royal Society of Chemistry.
- Schmidt, Robert,Stolle, Achim,Ondruschka, Bernd
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p. 1673 - 1679
(2013/02/22)
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- Simple and efficient system for the α-bromination of a β-ketoester by using N-bromosuccinimide in the presence of silicasupported NaHCo3 as the heterogeneous catalyst: An environmentally benevolent approach
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Selective and efficient α-bromination of β-ketoesters and cyclic and acyclic ketones is achieved by reaction with N-bromosuccinimide (NBS) catalyzed by silica-supported sodium bicarbonate (NaHCO3 · SiO2) under mild reaction conditions and with short reaction times. With 100% selectivity with all substrates, after 45 min at room temperature (20±2 °C), conversions for ethylacetoacetate were 67% and for acetophenone, cyclohexanone, and cycloheptanone were 58, 50, and 55%, respectively. Acetyl acetone recorded 65% conversion with 100% selectivity. Although cyclopentanone and toluene had only 20% conversion, both reactions showed 100% selectivity toward α-bromination. The catalysts exhibit activity and reusability. Copyright Taylor & Francis Group, LLC.
- Rahman, Ateeq,Jonnalagadda
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experimental part
p. 1091 - 1100
(2012/05/05)
-
- Copper-catalyzed cross-coupling reaction of organoboron compounds with primary alkyl halides and pseudohalides
-
Non-activated alkyl electrophiles, including alkyl iodides, bromides, tosylates, mesylates, and even chlorides, underwent copper-catalyzed cross-coupling with aryl boron compounds and alkyl 9-BBN reagents (see scheme; 9-BBN=9-borabicyclo[3.3.1]nonane). The reactions proceed with practically useful reactivities and thus complement palladium- and nickel-catalyzed Suzuki-Miyaura coupling reactions of alkyl halides.
- Yang, Chu-Ting,Zhang, Zhen-Qi,Liu, Yu-Chen,Liu, Lei
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p. 3904 - 3907
(2011/05/15)
-
- Gold-catalyzed halogenation of aromatics by N-halosuccinimides
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(Chemical Equation Presented) Golden bromination: A highly efficient and mild AuCl3-catalyzed bromination of aromatic rings with Nbromosuccinimide (NBS) has been developed. This method works with a low catalyst loading (down to 0.01 mol %) and can be combined with transition metal catalyzed transformations to deliver various aryl products.
- Mo, Fanyang,Yan, Jerry Mingtao,Qiu, Di,Li, Fei,Zhang, Yan,Wang, Jianbo
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scheme or table
p. 2028 - 2032
(2010/06/17)
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- Bromination of alkylbenzenes in 1-butyl-3-methylimidazolium bromide and its dibromide complex
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Alkylbenzenes were subjected to bromination with molecular bromine using 1-butyl-3-methylimidazolium bromide as solvent. A complex of 1-butyl-3-methylimidazolium bromide with bromine was synthesized. It ensured bromination of alkylbenzenes with no bromine and solvent. The results of bromination in binary solvents and ionic liquids, 1-butyl-3-methylimidazolium bromide and tribromide were compared. The bromination of ethylbenzene with 1-butyl-3-methylimidazolium tribromide was accompanied by formation of a considerable amount of α-bromoethylbenzene, which is not typical of electrophilic aromatic substitution process.
- Gruzdev,Virzum,Krylov
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scheme or table
p. 263 - 267
(2010/08/06)
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- Thallium(III) oxide as an oxidative reagent in organic chemistry
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Oxidative properties of thallium(III) oxide in various organic reactions were studied. Oxidative bromination of organic compounds in Tl2O 3-KBr-trifluoroacetic acid system was carried out. New synthetic method for preparation of diphenylthallium salts from phenylhydrazine and thallium(III) oxide was developed.
- Gun'kin
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scheme or table
p. 451 - 454
(2010/08/04)
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- PROCESS FOR THE PREPARATION OF 4-BROMOPHENYL DERIVATIVES
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Disclosed is a process for the preparation of a mixture of 4-bromophenyl derivatives (compound of formula (2)) and 2,4-dibromophenyl derivatives (compound of formula (3)) comprising the steps of [1] reacting in a two-phase (liquid-liquid) system a bromide containing source with a phenyl derivative (formula (1)) in the presence of an excess of an oxidizing agent, an acid, and optionally a catalyst selected from vanadium pentoxide and ammonium heptamolybdate forming 4-bromo- (compound of formula (2)) and 2,4-dibromo derivatives (compound of formula (3)) and as intermediate product the 2-bromo derivative (compound of formula (4)) which reacts in step [2] to the 2,4-dibromo derivative (formula (3)) according to the following reaction scheme 2 wherein R1 is hydroxy; C1-C5alkoxy; or -NR2R3; and R2 and R3 independently from each other are hydrogen; or C1-C5alkyl.
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Page/Page column 10-11
(2010/04/03)
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- Environmentally benign electrophilic and radical bromination 'on water': H2O2-HBr system versus N-bromosuccinimide
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A H2O2-HBr system and N-bromosuccinimide in an aqueous medium were used as a 'green' approach to electrophilic and radical bromination. Several activated and less activated aromatic molecules, phenylsubstituted ketones and styrene were efficiently brominated 'on water' using both systems at ambient temperature and without an added metal or acid catalyst, whereas various non-activated toluenes were functionalized at the benzyl position in the presence of visible light as a radical activator. A comparison of reactivity and selectivity of both brominating systems reveals the H2O2-HBr system to be more reactive than NBS for benzyl bromination and for the bromination of ketones, while for electrophilic aromatic substitution of methoxy-substituted tetralone it was higher for NBS. Also, higher yields of brominated aromatics were observed when using H2O2-HBr 'on water'. Bromination of styrene reveals that not just the structure of the brominating reagent but the reaction conditions: amount of water, organic solvent, stirring rate and interface structure, play a key role in defining the outcome of bromination (dibromination vs bromohydroxylation). In addition, mild reaction conditions, a straightforward isolation procedure, inexpensive reagents and a lower environment impact make aqueous brominating methods a possible alternative to other reported brominating protocols.
- Podgor?ek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
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experimental part
p. 4429 - 4439
(2009/10/09)
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- A new method of bromination of aromatic rings by an iso-amyl nitrite/HBr system
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A mixture of iso-amyl nitrite/HBr is shown to be a mild and efficient reagent for electrophilic aromatic bromination. The reaction succeeds with slightly activated arenes and heterocyclic compounds. By using HCl instead of HBr, chlorination can also be performed in few cases. The i-amONO2/HBr mixture can also be utilized for bromination in the α-position of electron withdrawing groups. A possible mechanism is briefly discussed.
- Gavara, Laurent,Boisse, Thomas,Rigo, Beno?t,Hénichart, Jean-Pierre
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p. 4999 - 5004
(2008/09/21)
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- Method of producing an o-disubstituted aromatic compound, and method of producing a monosubstituted-monohaloaromatic compound
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A method of producing an o-disubstituted aromatic compound, containing: continuously conducting at least the following steps (a) to (d): (a) a step of mono-lithiating one halogen atom of an o-dihaloaromatic compound, using a first microreactor; (b) a step of making the thus-obtained monolithiated product to react with an electrophilic compound, using a second microreactor, to obtain a monosubstituted-monohaloaromatic compound; (c) a step of lithiating the other halogen atom of the o-dihaloaromatic compound, using a third microreactor; and (d) a step of making the thus-obtained lithiated product successively to react with an electrophilic compound, using a forth microreactor.
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Page/Page column 13; 15; 17
(2008/12/07)
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- Catalytic Sandmeyer bromination
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An efficient catalyst system for Sandmeyer bromination is proposed. Aryl bromides and dibromides can be obtained with excellent yield by this synthetic protocol. Georg Thieme Verlag Stuttgart.
- Beletskaya, Irina P.,Sigeev, Alexander S.,Peregudov, Alexander S.,Petrovskii, Pavel V.
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p. 2534 - 2538
(2008/03/13)
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- Halogen-metal exchange in 1,2-dibromobenzene and the possible intermediacy of 1,2-dilithiobenzene
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(Chemical Equation Presented) The one-step high-yield synthesis of 1,2-bis(trimethylsilyl)-benzene from 1,2-dibromobenzene using tert-butyllithium and trimethylsilyltriflate is reported. A mechanistic investigation shows that 1,2-dilithiobenzene is not an intermediate in this reaction; the coexistence of trimethylsilyltriflate and tert-butyllithium at very low temperatures allows a sequence of bromine-lithium exchange and subsequent derivatization reactions to operate.
- Bettinger, Holger F.,Filthaus, Matthias
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p. 9750 - 9752
(2008/03/17)
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- A novel synthesis of bromobenzenes using molecular bromine
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Certain substituted bromobenzenes have been synthesized in acceptable yields using a novel Sandmeyer type reaction. The reactions are relatively quick and possibly proceed via a radical mechanism.
- Oezkan, Hamdi,Disli, Ali,Yildirir, Yilmaz,Tuerker, Lemi
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p. 2478 - 2483
(2008/03/13)
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- Sodium nitrite-catalyzed oxybromination of aromatic compounds and aryl ketones with a combination of hydrobromic acid and molecular oxygen under mild conditions
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A novel and efficient catalytic system for the oxybromination of aromatic compounds and aryl ketones utilizing a combination of aqueous hydrobromic acid and molecular oxygen in the presence of sodium nitrite under mild conditions has been developed. The newly developed catalytic system utilizes cheap and readily available reactants, exhibits high bromine atom economy and releases only innocuous water as the by-product.
- Zhang, Guofu,Liu, Renhua,Xu, Qing,Ma, Lixin,Liang, Xinmiao
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p. 862 - 866
(2007/10/03)
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- Induced bromination of aromatic hydrocarbons with alkali metal bromides in the presence of oxidants
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The features of induced bromination of aromatic hydrocarbons in the NaBr(KBr)-HX-H2O2(NaOCl) system were studied. Pleiades Publishing, Inc., 2006.
- Sadygov,Alimardanov,Chalabiev
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p. 949 - 956
(2008/02/05)
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- Regioselective halogen-metal exchange reaction of 3-substituted 1,2-dibromo arenes: The synthesis of 2-substituted 5-bromobenzoic acids
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Regioselective halogen-metal exchange reactions using isopropylmagnesium chloride were carried out on 3-substituted 1,2-dibromo arenes. Eleven examples are given. Georg Thieme Verlag Stuttgart.
- Menzel, Karsten,Dimichele, Lisa,Mills, Paul,Frantz, Doug E.,Nelson, Todd D.,Kress, Michael H.
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p. 1948 - 1952
(2008/02/08)
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- Method for separating substances
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An objective of the present invention is to provide electrophoretic separation methods and devices that enable the various features of a substrate surface that comes in contact with an electrophoresis medium to be controlled. The present invention provides methods for electrophoresing substances, which comprises the steps of: (a) adding a substance to be analyzed to an electrophoresis medium retained in a substrate, whose surface that has come in contact with the electrophoresis medium has been coated with a polymer membrane; and (b) adding electrophoretic pressure to the electrophoresis medium. For example, the use of a plasma-polymerized membrane allows the formation of a membrane with homogeneous quality and thickness on the surface of an arbitrary shape. In addition, desired characteristics can be conferred on the surface through selection of monomeric substances. Protein adsorption onto micro-chips can be effectively prevented as well.
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- Regioselective bromination of aromatic compounds with Br 2/SO2Cl2 over microporous catalysts
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A new selective brominating system Br2/SO2Cl 2/zeolite, has been discovered. Partially cation-exchanged Ca 2+-Y zeolite efficiently catalyzes the selective para-bromination of neat chlorobenzene (CB) by Br2/SO2Cl2 affording a CB conversion of ~89% and a para-selectivity of ~97%. During the bromination reaction, SO2Cl2 oxidizes HBr, prevents its accumulation within the zeolite pores and yields a more active brominating species. The Ca2+-Y catalyst was found to be stable under the bromination conditions, and can easily be regenerated by calcination. The Br2/SO2Cl2/Ca2+-Y brominating system could be applicable to other activated aromatic compounds such as o-xylene, toluene and fluorobenzene.
- Gnaim, Jallal M.,Sheldon, Roger A.
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p. 4465 - 4468
(2007/10/03)
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- Induced bromination of aromatic hydrocarbons by alkali metals bromides and sodium hypochlorite
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Induced bromination of aromatic compounds in a system MBr-acid-NaOCl was studied. Optimum conditions of the process were developed, kinetics of the reactions were investigated, and the process mechanism was suggested. The bromination occurs both with the bromine in statu nascendi and with the hypobromous acid by hydrogen substitution exclusively in the aromatic ring. 2005 Pleiades Publishing, Inc.
- Sadygov,Alimardanov,Chalabiev
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p. 1631 - 1636
(2007/10/03)
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- A simple and regioselective α-bromination of alkyl aromatic compounds by two-phase electrolysis
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Electrochemical bromination of toluene and substituted toluenes by two-phase electrolysis yields the corresponding α-brominated products. The reaction has been carried out in a single compartment cell with platinum electrodes at 0°C in chloroform using an aqueous sodium bromide solution (60%) containing a catalytic amount of HBr. Two-phase electrolysis results in high yields (60-95%) of monobromo compounds with very high regioselectivity (>95%).
- Raju,Kulangiappar,Anbu Kulandainathan,Muthukumaran
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p. 7047 - 7050
(2007/10/03)
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- Paradigm confirmed: The first use of ionic liquids to dramatically influence the outcome of chemical reactions
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It has been an unproven paradigm that the choice of which ionic liquid to use in a chemical reaction can have a dramatic effect on the outcome of that chemical reaction. We demonstrate, for the first time, that the reaction of toluene and nitric acid in three different ionic liquids gives rise to three completely different products in high yield. Furthermore, ionic liquids can catalyze these reactions with the only byproduct being water.
- Earle, Martyn J.,Katdare, Suhas P.,Seddon, Kenneth R.
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p. 707 - 710
(2007/10/03)
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- OOxidative bromination of activated aromatic compounds using aqueous nitric acid as an oxidant
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Oxidative bromination of activated aromatic compounds using alkali metal bromide salts and aqueous nitric acid to the corresponding bromo-derivatives is achieved in a liquid-liquid, two-phase system under ambient conditions. Nitric acid offers a dual function of an oxidant as well as a proton donor, which is essential for oxidative bromination using metal bromide salts. Bromination as well as chlorination could be accomplished with this simple system.
- Joshi, Ashutosh V.,Baidossi, Mubeen,Mukhopadhyay, Sudip,Sasson, Yoel
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p. 568 - 570
(2013/09/02)
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