- Novel site-specific one-step bromination of substituted benzenes
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Regiospecific bromination of benzene derivatives has been carried out with Me2SO-HBr; this method gives excellent yields of 2-bromobenzaldehyde and 2-bromonitrobenzene; strong ortho- and para-directing monosubstituted benzenes give para-bromo derivatives; a general discussion of the mechanism of these reactions is given.
- Srivastava, Sanjay K.,Chauhan, Prem Man Singh,Bhaduri, Amiya P.
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- A simple and improved procedure for selective ring bromination of alkyl-substituted aromatic hydrocarbons on the surface of alumina
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Highly selective ring bromination of alkyl-substituted aromatic hydrocarbons has been achieved using molecular bromine adsorbed on the surface of alumina without any solvent.
- Ranu,Sarkar,Chakraborty
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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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- 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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- Deoxygenation of carbonyl compounds using an alcohol as an efficient reducing agent catalyzed by oxo-rhenium complexes
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This work describes the first methodology for the deoxygenation of carbonyl compounds using an alcohol as a green solvent/reducing agent catalyzed by oxo-rhenium complexes. The system 3-pentanol/ReOCl3(SMe2)(OPPh3) was successfully employed in the deoxygenation of several aryl ketones to the corresponding alkenes and also in the deoxygenation of aryl aldehydes to alkanes with moderate to excellent yields. The catalyst ReOCl3(SMe2)(OPPh3) can also be used in several catalytic cycles with good activity.
- Bernardo, Joana R.,Fernandes, Ana C.
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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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- 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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- Reactivities of Several Nucleophiles toward 4-Methylbenzyne in Very Hot Water
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By means of competition experiments, the relative rates of reaction of several nucleophiles with 4-methylbenzyne in aqueous solution at temperatures up to 318 deg C have been determined.The relative nucleophilicities vs. chloride ion are as follows: PhS-, 46; I-, 6.2; piperidine, 3.0; Br-, 1.7; aniline, 1.3; Cl-, (1.0); PhO-, 1.0; ammonia, 0.55; F-, 0.20.For all but PhS-, piperidine, and iodide, the p/m product ratio is 0.83+/-0.02.In the cases of PhS- and piperidine a competing mechanism of ipso substitution, probably involving catalysis by copper ions, caused the observed p/m ratios to be high and variable.Our experimental design precluded determination of the p/m ratio for iodide ion.Because of chemical complications, only rough estimates could be made of the nucleophilicities of nitrite and benzenesulfinate ions.
- Zoratti, Mario,Bunnett, J. F
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- Halogenation of Aromatic Compounds by using Sodium Perborate as an Oxidant
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A facile method for the halogenation of benzene and its derivatives by aqueous haloacids (HCl and HBr) using sodium perborate as an oxidising agent in the presence of tertabutylammonium bromide as a phase transfer catalyst is described.
- Deshmukh, Anjali P.,Padiya, Kamlesh J.,Jadhav, Vidyadhar K.,Salunkhe, Manikrao M.
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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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- Dynamics of endoergic substitution reactions. I. Br+chlorinated aromatic compounds
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The endoergic substitution reactions Br + R-Cl -> Cl + R-Br (R = o-, m-, andp-CH3C6H4, C6H5, C6F5; ΔH0 ca. 15 kcal/mol) have been studied using the crossed molecular beams method in the collision energy (Ec ) range 2-35 kcal/mol.The CH3C6H4Br and C6F5Br products were found to be mostly forward scattered with respect to the incident Br beam indicating that the lifetimes of the Br-R-Cl collision complexes are short compared to their rotational periods.The product translational energy distributions and excitation functions for these reactions are well reproduced by statistical calculations that assume that only a few vibrational modes in the collision complexes participate in intramolecular energy redistribution prior to Cl elimination.Ring substituents are found to affect both the extent of energy redistribution in the complexes and the probability of Br addition.For example, no substitution product was observed with m-CH3C6H4Cl or C6H5Cl.The relative magnitudes of the cross sections are explained in terms of possible features of the potential energy surfaces along their reaction coordinates.
- Robinson, Gary N.,Continetti, Robert E.,Lee, Yuan T.
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- Selective para-Bromination of Toluene catalysed by Na-Y Zeolite in the Presence of an Epoxide
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Propylene oxide, serving as an HBr scavenger, dramatically improved the selectivity of zeolite-catalysed toluene bromination to yield almost pure p-bromotoluene.
- Vega, Fernando de la,Sasson, Yoel
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- Halogenation Using N-Halogenocompounds. II. Acid Catalyzed Bromination of Aromatic Compounds with 1,3-Dibromo-5,5-dimethylhydantoin
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Ring bromination of aromatic compounds using 1,3-dibromo-5,5-dimethylhydantoin in dichloromethane is promoted by the addition of strong acids.Both organic and inorganic acids whose pKa values are lower than -2 showed the promoting effect.This acid-catalyzed bromination is both practical and effective, even for aromatics having electron-withdrawing substituents.
- Eguchi, Hisao,Kawaguchi, Hideichiro,Yoshinaga, Sachiyo,Nishida, Akiko,Nishiguchi, Takeshi,Fujisaki, Shizuo
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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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- Synthesis of tin-containing cyclodextrins as potential enzyme models
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The synthesis and the characterization of two types of water-soluble β-cyclodextrin-supported organotin derivatives is described. These new tin-containing macromolecules were prepared through a free radical bishydrostannylation of the corresponding β-cyclodextrin propargylic ethers using Me2SnClH prepared in situ with AIBN as initiator. The tin moieties were attached both on the primary and on the secondary rim of β-cyclodextrin in excellent yield.
- Zhou, You,Marinescu, Lavinia,Pedersen, Christian Marcus,Bols, Mikael
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- Room-temperature catalytic hydrodefluorination of C(sp3)-F bonds
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Room-temperature catalytic hydrodefluorination of the strong C(sp3)-F bonds in benzotrifluorides and fluoropentane is catalyzed by Et3Si[B(C6F5)4] and uses Et3SiH as the source of H. Ar-CF
- Scott, Valerie J.,Celenligil-Cetin, Remle,Ozerov, Oleg V.
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- Molecular structures of the metastable charge-transfer complexes of benzene (and toluene) with bromine as the pre-reactive intermediates in electrophilic aromatic bromination
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Successful crystallization and X-ray crystallographic analyses of the highly metastable (1:1) complexes of bromine with benzene and toluene establish the unique (localized) structure B that di3ers in notable ways from the long-accepted (delocalized) structure A. Furthermore, we demonstrate the (highly structured) charge-transfer complexes [C6H6,Br2] and [CH3C6H5,Br2] to be the pre-reactive intermediates that are converted (via an overall Br+ transfer) to the Wheland intermediates in electrophilic aromatic bromination. The role of the dative ion pairs [C6H6·+ Br2·-] and [CH3C6H5·+ Br2·-] in the rate-limiting activation processes is underscored.
- Vasilyev, Alexandr V.,Lindeman, Sergey V.,Kochi, Jay K.
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- 1,3-dibromo-5,5-dimethylhydantoin, a useful reagent for aromatic bromination
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1,3-dibromo-5,5-dimethylhydantoin (DBDMH) is a useful and easy to handle reagent for bromination of various aromatic derivatives substituted with electron donating groups. In the presence of trimethylsilyltrifluoromethanesulfonate, DBDMH showed increased reactivity, and in one case, the reaction followed another pathway, suggesting an alternative mechanism.
- Chassaing, Christophe,Haudrechy, Arnaud,Langlois, Yves
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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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- An efficient copper-catalysed aerobic oxybromination of arenes in water
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An aerobic oxybromination of arenes catalysed by Cu(NO3) 2 was achieved using HBr as a bromine source, molecular oxygen as the oxidant and water as solvent with high selectivity. The catalyst shows not only high chemoselectivity for monobromination, but also a remarkable regioselectivity for para-isomers.
- Wang, Jian,Wang, Wei,Li, Jing-Hua
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- Reactions of benzyltriphenylphosphonium salts under photoredox catalysis
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The development of benzyltriphenylphosphonium salts as alkyl radical precursors using photoredox catalysis is described. Depending on substituents, the benzylic radicals may couple to form C-C bonds or abstract a hydrogen atom to form C-H bonds. A natural product, brittonin A, was also synthesized using this method.
- Boldt, Andrew M.,Dickinson, Sidney I.,Ramirez, Jonathan R.,Benz-Weeden, Anna M.,Wilson, David S.,Stevenson, Susan M.
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p. 7810 - 7815
(2021/09/28)
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- Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C-X Bonds
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We report the formation and full characterization of weak adducts between Li+ and Na+ cations and a neutral iron(0) complex, [Fe(CO)3(PMe3)2] (1), supported by weakly coordinating [BArF20] anions, [1·M][BArF20] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)3(PMe3)2][BArF20], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and cross-coupling reactions and the formation of new C-E bonds (E = C, H, O, N, S). Further, we utilize [1·M][BArF20] as a catalyst in a simple hydrodehalogenation reaction under mild conditions to showcase its potential use in catalytic reactions. Finally, the mechanism of activation is probed using DFT and kinetic experiments that reveal that the alkali metal and iron(0) center cooperate to cleave C-X via a mechanism closely related to intramolecular FLP activation.
- Tinnermann, Hendrik,Sung, Simon,Csókás, Dániel,Toh, Zhi Hao,Fraser, Craig,Young, Rowan D.
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supporting information
p. 10700 - 10708
(2021/07/31)
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- Mixed Micelles of Surface Active Ionic Liquid (SAIL)–Octylphenol Ethoxylate: A Novel Reaction Medium for Selective Oxidation of Toluene to Benzaldehyde
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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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- Direct Preparation of N-Substituted Pyrazoles from Primary Aliphatic or Aromatic Amines
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Despite a large number of synthesis procedures for pyrazoles known today, those directly employing primary amines as substrates are rare. Herein, we report an original method for the preparation of N-alkyl and N-aryl pyrazoles from primary aliphatic or aromatic amines as a limiting reagent of the reaction. The protocol utilizes no inorganic reagents and requires a short reaction time, mild conditions, and the use of structurally simple and commercially available starting reagents. During this study, pyrazoles containing a wide variety of N-substituents were obtained using the same procedure for both aliphatic and aromatic amines.
- Gulia, Nurbey,Ma?ecki, Marcin,Szafert, S?awomir
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supporting information
p. 9353 - 9359
(2021/07/26)
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- Hydrogen-Bond-Donor Solvents Enable Catalyst-Free (Radio)-Halogenation and Deuteration of Organoborons
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A hydrogen bond donor solvent assisted (radio)halogenation and deuteration of organoborons has been developed. The reactions exhibited high functional group tolerance and needed only an ambient atmosphere. Most importantly, compared to literature methods, our conditions are more consistent with the principals of green chemistry (e.g., metal-free, strong oxidant-free, more straightforward conditions).
- Yang, Yi,Gao, Xinyan,Zeng, Xiaojun,Han, Junbin,Xu, Bo
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supporting information
p. 1297 - 1300
(2020/12/23)
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- Direct bromodeboronation of arylboronic acids with CuBr2 in water
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An efficient and practical method has been developed for the preparation of aryl bromides via the direct bromodeboronation of arylboronic acids with CuBr2 in water. This strategy provides several advantages, such as being ligand-free, base-free, high yielding, and functional group tolerant.
- Tang, Yan-Ling,Xia, Xian-Song,Gao, Jin-Chun,Li, Min-Xin,Mao, Ze-Wei
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supporting information
(2021/01/05)
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- Poly-N-bromosulfonamide-melamine as a novel brominating reagent for regioselective ipso-bromination of arylboronic acids
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A practical synthetic method for the synthesis of aryl bromide was developed through regioselective bromination of boronic acid in the presence of poly-N-bromosulfonamide-melamine (PBBSM). In this regard, a novel heterogeneous support, cross-linked poly sulfonamide-melamine, has been successfully synthesized to stabilize bromine with high surface functional group density (6.6?mmol Br+/g). The prepared reagent is a novel brominating reagent that combines the effective functions of N-bromosulfonamide, N-bromosulfonamide-melamine, and melamine groups. The structure of PBBSM was characterized using XRD, FT–IR, 1H NMR, TGA, FE-SEM, EDX, and TGA analysis. Graphic abstract: [Figure not available: see fulltext.]
- Alavinia, Sedigheh,Ghorbani-Vaghei, Ramin
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p. 1269 - 1276
(2021/08/27)
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- The graphite-catalyzed: ipso -functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes
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An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.
- Badgoti, Ranveer Singh,Dandia, Anshu,Parewa, Vijay,Rathore, Kuldeep S.,Saini, Pratibha,Sharma, Ruchi
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p. 18040 - 18049
(2021/05/29)
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- Induced Fitting and Polarization of a Bromine Molecule in an Electrophilic Inorganic Molecular Cavity and Its Bromination Reactivity
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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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- Methane Generation and Reductive Debromination of Benzylic Position by Reconstituted Myoglobin Containing Nickel Tetradehydrocorrin as a Model of Methyl-coenzyme M Reductase
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Methyl-coenzyme M reductase (MCR), which contains the nickel hydrocorphinoid cofactor F430, is responsible for biological methane generation under anaerobic conditions via a reaction mechanism which has not been completely elucidated. In this work, myoglobin reconstituted with an artificial cofactor, nickel(I) tetradehydrocorrin (NiI(TDHC)), is used as a protein-based functional model for MCR. The reconstituted protein, rMb(NiI(TDHC)), is found to react with methyl donors such as methyl p-toluenesulfonate and trimethylsulfonium iodide with methane evolution observed in aqueous media containing dithionite. Moreover, rMb(NiI(TDHC)) is found to convert benzyl bromide derivatives to reductively debrominated products without homocoupling products. The reactivity increases in the order of primary > secondary > tertiary benzylic carbons, indicating steric effects on the reaction of the nickel center with the benzylic carbon in the initial step. In addition, Hammett plots using a series of para-substituted benzyl bromides exhibit enhancement of the reactivity with introduction of electron-withdrawing substituents, as shown by the positive slope against polar substituent constants. These results suggest a nucleophilic SN2-type reaction of the Ni(I) species with the benzylic carbon to provide an organonickel species as an intermediate. The reaction in D2O buffer at pD 7.0 causes a complete isotope shift of the product by +1 mass unit, supporting our proposal that protonation of the organonickel intermediate occurs during product formation. Although the turnover numbers are limited due to inactivation of the cofactor by side reactions, the present findings will contribute to elucidating the reaction mechanism of MCR-catalyzed methane generation from activated methyl sources and dehalogenation.
- Hayashi, Takashi,Miyazaki, Yuta,Oohora, Koji
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supporting information
p. 11995 - 12004
(2020/09/15)
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- Preparation method of monobrominated aromatic hydrocarbon compound
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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.
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Paragraph 0055-0067
(2020/11/23)
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- Electrocatalytic Deuteration of Halides with D2O as the Deuterium Source over a Copper Nanowire Arrays Cathode
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Precise deuterium incorporation with controllable deuterated sites is extremely desirable. Here, a facile and efficient electrocatalytic deuterodehalogenation of halides using D2O as the deuteration reagent and copper nanowire arrays (Cu NWAs) electrochemically formed in situ as the cathode was demonstrated. A cross-coupling of carbon and deuterium free radicals might be involved for this ipso-selective deuteration. This method exhibited excellent chemoselectivity and high compatibility with the easily reducible functional groups (C=C, C≡C, C=O, C=N, C≡N). The C?H to C?D transformations were achieved with high yields and deuterium ratios through a one-pot halogenation–deuterodehalogenation process. Efficient deuteration of less-active bromide substrates, specific deuterium incorporation into top-selling pharmaceuticals, and oxidant-free paired anodic synthesis of high-value chemicals with low energy input highlighted the potential practicality.
- Chong, Xiaodan,Han, Shuyan,Li, Mengyang,Liu, Cuibo,Zhang, Bin
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supporting information
p. 18527 - 18531
(2020/08/21)
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- Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations
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While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive-free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.
- Deckers, Kristina,Fricke, Christoph,Schoenebeck, Franziska
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supporting information
p. 18717 - 18722
(2020/08/25)
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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)
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- Pd(OH)2/C, a Practical and Efficient Catalyst for the Carboxylation of Benzylic Bromides with Carbon Monoxide
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A simple, efficient, cheap, and broadly applicable system for the carboxylation of benzylic bromides with carbon monoxide and water is reported. Upon simple reaction with only 2.5 wt % of Pearlman's catalyst and 10 mol % of tetrabutylammonium bromide in tetrahydrofuran at 110 °C for 4 h, a range of benzylic bromides can be smoothly converted to the corresponding arylacetic acids in good to excellent yields after simple extraction and acid-base wash. The reaction was found to be broadly applicable, scalable, and could be successfully extended to the use of ex situ-generated carbon monoxide and applied to the synthesis of the nonsteroidal anti-inflammatory drug diclofenac.
- Wakuluk-Machado, Anne-Marie,Dewez, Damien F.,Baguia, Hajar,Imbratta, Miguel,Echeverria, Pierre-Georges,Evano, Gwilherm
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p. 713 - 723
(2020/02/04)
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- A Free-Radical Reduction and Cyclization of Alkyl Halides Mediated by FeCl2
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Iron mediated catalytic reactions are of great interest in the field of organic synthesis because they are economic and naturally abundant. However, the use of iron catalyst in the field of free radical cyclization or reduction of alkyl halides remains limited. Here we describe the use of an unprecedented combination of iron and zinc in the reduction and 5-exo-trig radical cyclization of alkyl halides under mild condition in the absence of added ligands or additives. The method is distinguished by its wide scope, functional group tolerance and the use of 1,4-cyclohexadiene as the source of hydrogen, which aids easy purification.
- Pulikottil, Feba Thomas,Pilli, Ramadevi,Murugesan, Vetrivelan,Krishnan, Chandu G.,Rasappan, Ramesh
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p. 2438 - 2442
(2019/04/30)
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- Phosphonic acid mediated practical dehalogenation and benzylation with benzyl halides
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For the first time, by using H3PO3/I2 system, various benzyl chlorides, bromides and iodides were dehalogenated successfully. In the presence of H3PO3, benzyl halides underwent electrophilic substitution reactions with electron-rich arenes, leading to a broad range of diarylmethanes in good yields. These transformations feature green, cheap reducing reagents and metal-free conditions. A possible mechanism was proposed.
- Gao, Jing,Han, Li-Biao,Ma, Yonghao,Tang, Zilong,Wu, Xiaofang,Xiao, Jing
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p. 22343 - 22347
(2019/07/31)
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- 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
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supporting information
p. 4593 - 4596
(2019/07/05)
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- Tetradentate amido azo Schiff base Cu(II), Ni(II) and Pd(II) complexes: Synthesis, characterization, spectral properties, and applications to catalysis in C–C coupling and oxidation reaction
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New Schiff base ligands (H2L1 & H2L2) were synthesized by the reaction of salicylaldehyde with (2-((2-aminophenyl)diazenyl)-N-alkylaniline), and were used for the preparation of complexes with Cu(II), Ni(II) and Pd(II) metal ions. The structural features of the synthesized compounds were examined by UV–Vis, IR and 1H NMR spectroscopy. The crystal structures of Schiff base (H2L1) and two metal complexes Cu(L1) and Ni(L2) were determined by single crystal X-ray diffraction. The studies revealed that the synthesized Schiff bases existed as tetradentate (N,N,N,O) ligands and bonded to the metal ions through the donor atoms of the amido nitrogen, azo nitrogen, azomethine nitrogen and phenolic oxygen atoms. The redox property of Cu(L1) and Ni(L1) and emission behavior of ligand H2L1 and complexes Cu(L1) and Ni(L1) were examined. The complex Cu(L1) shows excellent catalytic activity towards oxidation of benzyl alcohol to benzyldehyde (under solvent-free condition) using H2O2 as the oxidant. Complex Pd(L1) acts as highly efficient catalyst in the Suzuki–Miyaura cross-coupling reaction of various aryl halides with phenyl boronic acid to produce the corresponding biaryls with high yields under mild reaction conditions. Both the catalysts Cu(L1) and Pd(L1) were easily recovered by simple chromatographic separation and reused for next catalytic cycle.
- Pratihar, Jahar Lal,Mandal, Paritosh,Lai, Chung Kung,Chattopadhyay, Surajit
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p. 317 - 324
(2019/02/06)
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- ipso-Bromination/iodination of arylboronic acids: Poly(4-vinylpyridine)-Br2/I2 complexes as safe and efficient reagents
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Poly(4-vinyl pyridine) supported bromine/iodine complexes were prepared and probed for ipso-bromination/iodination of arylboronic acids. These solid complexes with catalytic amount of additive are found to be safe and efficient reagent system for the ipso-bromination/iodination. The reaction occurs under mild conditions and tolerates various functional groups resulting in products with high selectivity and yields.
- Fu, Fang,Gurung, Laxman,Czaun, Miklos,Mathew, Thomas,Prakash, G.K. Surya
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supporting information
(2019/08/26)
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- Catalytic Hydrodefluorination of C?F Bonds by an Air-Stable PIII Lewis Acid
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Catalytic hydrodefluorination (HDF) of unactivated fluoroalkanes or CF3-substituted aryl species is performed using the PIII Lewis acids, [(bipy)PPh]2+ (12+) and [(terpy)PPh]2+ (22+) under
- Chitnis, Saurabh S.,Krischer, Felix,Stephan, Douglas W.
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p. 6543 - 6546
(2018/04/26)
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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
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supporting information
p. 5264 - 5267
(2018/09/12)
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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
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supporting information
p. 4933 - 4939
(2018/12/14)
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- Ultra-Stable and High-Cobalt-Loaded Cobalt@Ordered Mesoporous Carbon Catalysts: All-in-One Deoxygenation of Ketone into Alkylbenzene
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Catalytic deoxygenation represents a straightforward and core methodology for fine-chemical production and biomass upgrading. Generally, the application of homogeneous metal complexes or heterogeneous noble-metal catalysts prevails in academia and the chemical industry. Herein, we introduce cobalt@ordered mesoporous carbon (Co@OMC) catalysts, which are constructed conveniently by a mechanochemical coordination self-assembly based on a renewable tannin precursor. Importantly, the Co@OMC catalysts with a high loading of in situ confined Co species promote the selective deoxygenation of various ketones, aldehydes, and alcohols efficiently into the corresponding alkanes under mild conditions. Therefore, a simple, inexpensive, and heterogeneous catalyst for selective deoxygenation can be expected, meanwhile the solid-state synthesis affords a green, rapid, and scalable pathway to Co@OMC catalysts.
- Zhang, Pengfei,Chen, Nanqing,Chen, Dong,Yang, Shize,Liu, Xiaofei,Wang, Li,Wu, Peiwen,Phillip, Nathan,Yang, Guang,Dai, Sheng
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p. 3299 - 3304
(2018/06/04)
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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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- 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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- Silver/NBS-Catalyzed Synthesis of α-Alkylated Aryl Ketones from Internal Alkynes and Benzyl Alcohols via Ether Intermediates
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The silver hexafluoroantimonate/N-bromosuccinimide (NBS)-catalyzed synthesis of α-alkylated aryl ketones with a tertiary carbon center from internal alkynes and benzyl alcohols is reported. This reaction proceeds via the etherification of benzyl alcohols with an in situ generated benzyl bromide, formed by the reaction of benzyl alcohol with a catalytic amount of NBS and AgSbF6. Ag-catalyzed C-O cleavage of the ether leads to a tolyl radical, which undergoes addition to the alkyne, ultimately leading to the α-alkylated aryl ketone products.
- Chun, Supill,Chung, Young Keun
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supporting information
p. 5583 - 5586
(2018/09/21)
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- Ni-Catalyzed cross-coupling of aryl thioethers with alkyl Grignard reagents via C-S bond cleavage
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A Ni-catalyzed cross-coupling of aryl thioethers with alkyl Grignard reagents, accompanied by the cleavage of the C(aryl)-SMe bond, has been presented. This method is distinguished by its mild conditions and moderate functional group tolerance, such as hydroxyl, halogen, and heterocycles, which should provide a straightforward access to the modification of sulfur-containing molecules.
- Zhu, Dan,Shi, Lei
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supporting information
p. 9313 - 9316
(2018/08/29)
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- A general electrochemical strategy for the Sandmeyer reaction
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Herein we report a general electrochemical strategy for the Sandmeyer reaction. Using electricity as the driving force, this protocol employs a simple and inexpensive halogen source, such as NBS, CBrCl3, CH2I2, CCl4, LiCl and NaBr for the halogenation of aryl diazonium salts. In addition, we found that these electrochemical reactions could be performed using anilines as the starting material in a one-pot fashion. Furthermore, the practicality of this process was demonstrated in the multigram scale synthesis of aryl halides using highly inexpensive graphite as the electrode. A series of detailed mechanism studies have been performed, including radical clock and radical scavenger study, cyclic voltammetry analysis and in situ electron paramagnetic resonance (EPR) analysis.
- Liu, Qianyi,Sun, Beiqi,Liu, Zheng,Kao, Yi,Dong, Bo-Wei,Jiang, Shang-Da,Li, Feng,Liu, Guoquan,Yang, Yang,Mo, Fanyang
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p. 8731 - 8737
(2018/12/10)
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- Polymethylhydrosiloxane reduction of carbonyl function catalysed by titanium tetrachloride
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Reduction of aromatic aldehydes and ketones into the corresponding methylene derivatives by polymethylhydrosiloxane in the presence of titanium tetrachloride as catalyst was achieved in good to excellent yields ranging from 55-90%. The reaction took place under relatively mild conditions and smoothly led to the desired target molecules in the presence of other functional groups such as halogens, hydroxyl, nitro and methoxy groups. However, in the reduction of the substrate with two methoxy groups in close proximity (1,2-positions), the reaction necessitated a larger amount of the titanium catalyst and a longer reaction time to complete the reduction of the carbonyl function due to a likely complex formation of titanium tetrachloride with the methoxy groups.
- Jumbam, Ndze D.,Makaluza, Siyavuya,Masamba, Wayiza
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p. 179 - 184
(2018/04/20)
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- One-Pot, Metal-Free Conversion of Anilines to Aryl Bromides and Iodides
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A metal-free synthesis of aryl bromides and iodides from anilines via halogen abstraction from bromotrichloromethane and diiodomethane is described. This one-pot reaction affords aryl halides from the corresponding anilines in moderate to excellent yields without isolation of diazonium salts. The transformation has short reaction times, a simple workup, and insensitivity to moisture and air and avoids excess halogenation. DFT calculations support a SRN1 mechanism. This method represents a convenient alternative to the classic Sandmeyer reaction.
- Leas, Derek A.,Dong, Yuxiang,Vennerstrom, Jonathan L.,Stack, Douglas E.
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supporting information
p. 2518 - 2521
(2017/05/24)
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- Structure-based optimization leads to the discovery of NSC765844, a highly potent, less toxic and orally efficacious dual PI3K/mTOR inhibitor
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The phosphoinositide 3-kinase (PI3K) family is one of the most frequently activated enzymes in a wide range of human cancers; thus, inhibition of PI3K represents a promising strategy for cancer therapy. Herein, a series of benzylamine substituted arylsulfonamides were designed and synthesized as dual PI3K/mTOR inhibitors using a strategy integrating focused library design and virtual screening, resulting in the discovery of 13b (NSC765844). The compound 13b exhibits highly potent enzyme inhibition with IC50s of 1.3, 1.8, 1.5, 3.8 and 3.8?nM for PI3Kα, β, γ, δ, and mTOR, respectively. 13b was further evaluated in NCI by an in?vitro cytotoxic screening program. Broad-spectrum antitumor activities with mean GI50value of 18.6?nM against approximately 60 human tumor cell lines were found. 13b displayed favorable physicochemical properties and superior pharmacokinetic profiles for animal studies. It significantly inhibited tumor growth when administered orally in an A549 non-small-cell lung carcinoma xenograft and BEL7404 human hepatocellular carcinoma xenograft models. On the basis of its excellent in?vivo efficacy and superior pharmacokinetic profiles, 13b has been selected for further preclinical investigation as a promising anticancer drug candidate.
- Han, Jinsong,Chen, Ying,Yang, Chao,Liu, Ting,Wang, Mingping,Xu, Haojie,Zhang, Ling,Zheng, Canhui,Song, Yunlong,Zhu, Ju
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p. 684 - 701
(2016/07/21)
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- Method for synthesizing bromotoluene
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The invention relates to a method for synthesizing bromotoluene and belongs to the technical field of green bromination chemical engineering. According to the method for synthesizing bromotoluene, high-activity bromine chloride generated by hydrobromic acid and sodium hypochlorite serves as a bromine source, ferric chloride serves as a catalyst, high-activity bromine chloride and ferric chloride react with toluene in an aqueous solution, and high-selectivity preparation of parabromotoluene is achieved. According to the method for synthesizing parabromotoluene, green chemical engineering requirements serve as guidance, parabromotoluene is synthesized by means of raw materials easy to obtain, safe and low in cost in an aqueous phase in a high selectivity and high atom utilization rate mode, and convenience is brought to further preparation of high-purity parabromotoluene.
- -
-
Paragraph 0036-0044
(2017/03/22)
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- Nucleophile promoted gold redox catalysis with diazonium salts: C-Br, C-S and C-P bond formation through catalytic Sandmeyer coupling
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Gold-catalyzed C-heteroatom (C-X) coupling reactions are evaluated without using sacrificial oxidants. Vital to the success of this methodology is the nucleophile-assisted activation of aryldiazonium salts, which could be an effective oxidant for converting Au(i) to Au(iii) even without the addition of an assisting ligand or photocatalyst. By accelerating the reaction kinetics to outcompete C-C homo-coupling or diazonium dediazoniation, gold-catalyzed Sandmeyer reactions were achieved with different nucleophiles, forming C-Br, C-S and C-P bonds in high yields and selectivities.
- Peng, Haihui,Cai, Rong,Xu, Chang,Chen, Hao,Shi, Xiaodong
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p. 6190 - 6196
(2016/09/03)
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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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- A Metal-Free and Ionic Liquid-Catalyzed Aerobic Oxidative Bromination in Water
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A metal-free aerobic oxidative bromination of aromatic compounds in water has been developed. Hydrobromic acid is used as a bromine source and 2-methylpyridinium nitrate ionic liquid is used as a recyclable catalyst. Water is used as the reaction mediate. This is the first report of aerobic oxidative bromination using only catalytic amount of metal-free catalyst. This system shows not only high bromine atom economy, but also high bromination selectivity. The possible mechanism and the role of the catalyst in this system have also been discussed.
- Wang, Jian,Chen, Shu-Bin,Wang, Shu-Guang,Li, Jing-Hua
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p. 513 - 517
(2015/03/30)
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- Preparation of an Arenylmethylzinc Reagent with Functional Groups by Chemoselective Cross-Coupling Reaction of Bis(iodoazincio)methane with Iodoarenes
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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)
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- 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
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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)
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- Organometallic nickel(III) complexes relevant to cross-coupling and carbon-heteroatom bond formation reactions
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Nickel complexes have been widely employed as catalysts in C-C and C-heteroatom bond formation reactions. In addition to Ni(0) and Ni(II) intermediates, several Ni-catalyzed reactions are proposed to also involve odd-electron Ni(I) and Ni(III) oxidation states. We report herein the isolation, structural and spectroscopic characterization, and organometallic reactivity of Ni(III) complexes containing aryl and alkyl ligands. These Ni(III) species undergo transmetalation and/or reductive elimination reactions to form new C-C or C-heteroatom bonds and are also competent catalysts for Kumada and Negishi cross-coupling reactions. Overall, these results provide strong evidence for the direct involvement of organometallic Ni(III) species in cross-coupling reactions and oxidatively induced C-heteroatom bond formation reactions.
- Zheng, Bo,Tang, Fengzhi,Luo, Jia,Schultz, Jason W.,Rath, Nigam P.,Mirica, Liviu M.
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supporting information
p. 6499 - 6504
(2014/05/20)
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- A sustainable process for catalytic oxidative bromination with molecular oxygen
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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)
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- 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
-
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- 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
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supporting information
p. 1063 - 1066
(2013/04/10)
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- 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
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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
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supporting information
p. 2108 - 2111
(2013/06/05)
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- The oxidative halogenations of arenes in water using hydrogen peroxide and halide salts over an ionic catalyst containing sulfo group and hexafluorotitanate
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An ionic compound, bis[1-methyl-3-(3′-sulfopropyl)imidazolium] hexafluorotitanate (1), was proved to be the efficient and recyclable catalyst for the oxidative halogenations of arenes in water using H2O 2 as the oxidant and halide salts as the halogenation sources. The mono-halogenated products were obtained selectively by this method. The synergetic catalytic effect coming from the two incorporated functionalities of SO3H and [TiF6]2- was manifested in 1. The halogenation rate catalyzed by 1 was in the ranking of NaBr NaCl > KI. The UV-vis and FT-IR analyses indicated that the successful formation and regeneration of the active peroxo-Ti species (1A) with the aid of proton acid guaranteed the recycling uses of 1.
- Wang, Ling,Wang, Sa-Sa,Vo-Thanh, Giang,Liu, Ye
-
-
- 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
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supporting information
p. 11963 - 11970
(2013/09/02)
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- Ruthenium-catalyzed transformation of aryl and alkenyl triflates to halides
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Aryl triflates were transformed to aryl bromides/iodides simply by treating them with LiBr/NaI and [Cp*Ru(MeCN)3]OTf. The ruthenium complex also catalyzed the transformation of alkenyl sulfonates and phosphates to alkenyl halides under mild conditions. Aryl and alkenyl triflates undergo oxidative addition to a ruthenium(II) complex to form η'1- arylruthenium and 1-ruthenacyclopropene intermediates, respectively, which are transformed to the corresponding halides.
- Imazaki, Yusuke,Shirakawa, Eiji,Ueno, Ryota,Hayashi, Tamio
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supporting information
p. 14760 - 14763
(2012/11/07)
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