- Halogenated method of aromatic compound
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The invention belongs to the field of organic synthesis, and particularly relates to synthesis of aromatic halogens, in particular to arylamine. The invention discloses a synthesis method of a corresponding ortho-halogenated product from aromatic compounds such as carbazole and phenol. The method comprises the following steps: adding a metal sulfonate salt catalyst, aromatic amine, carbazole, phenol and other hydrogen - heteroatom-containing aromatic compound reaction substrates, a halogenation reagent and a reaction solvent at a specific reaction temperature. After the drying agent is dried, the yield of the reaction product and the nuclear magnetic characterization determining structure are determined by column chromatography. The reaction product yield is determined by gas chromatography. By adopting the method, under the cheap metal salt catalyst, a plurality of ortho-substituted brominated and chloro products can be obtained with moderate to excellent yield.
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- Regioselective monobromination of phenols with KBr and ZnAl–BrO3?–layered double hydroxides
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The regioselective mono-bromination of phenols has been successfully developed with KBr and ZnAl–BrO3?–layered double hydroxides (abbreviated as ZnAl–BrO3?–LDHs) as brominating reagents. The para site is much favorable and the ortho site takes the priority if para site is occupied. This reaction featured with excellent regioselectivity, cheap brominating reagents, mild reaction condition, high atom economy, broad substrate scope, and provided an efficient method to synthesize bromophenols.
- Wang, Ligeng,Feng, Chun,Zhang, Yan,Hu, Jun
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supporting information
(2020/02/22)
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- A convenient and efficient H2SO4-promoted regioselective monobromination of phenol derivatives using N-bromosuccinimide
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A convenient, rapid H2SO4-promoted regioselective monobromination reaction with N-bromosuccinimide was developed. The desired para-monobrominated or ortho-monobrominated products of phenol derivatives were obtained in good to excellent yields with high selectivity. Regioselective chlorination and iodination were also achieved in the presence of H2SO4 using N-chlorosuccinimide and N-iodosuccinimide, respectively.
- Wu, Yong-Qi,Lu, Hai-Jia,Zhao, Wen-Ting,Zhao, Hong-Yi,Lin, Zi-Yun,Zhang, Dong-Feng,Huang, Hai-Hong
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supporting information
p. 813 - 822
(2020/02/15)
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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 0071-0074
(2020/11/23)
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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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- A phenol compound high regioselective bromination method
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The invention discloses a phenol compound high regioselective bromination of the method, the method to trimethyl silane as brominating agent, in order to aryl sulfoxide as activator, with the phenol compound in the 0 - 50 °C lower, in a solvent, the reaction is stirred under an atmosphere of nitrogen at 1 - 12 hours, to realize the phenol compound high regioselective bromination, filtered, extraction columns chromatography separation to obtain the bromo phenol compound. This invention adopts the aryl sulfoxide as activator, sulfoxide substituted Kiev, on the one hand so that the phenol compound bromo the higher selectivity of the reaction region, and when the phenol compound hydroxy alignment not substituted basetime, regional selective para - bromo product, when the phenol compound hydroxy position there is substituted basetime, selective ortho - bromo product obtained; on the other hand if it through the filter, the extraction can be realized at the same time the isolation and purification of the recycling of the by-product, compared with column chromatography, reduces the separation and purification cost.
- -
-
Paragraph 0031; 0032; 0033
(2019/06/05)
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- 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane: An efficient and high oxygen content oxidant in various oxidative reactions
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Several oxidative approaches namely thiocyanation of aromatic compounds, epoxidation of alkenes, amidation of aromatic aldehydes, epoxidation of α β-unsaturated ketones, oxidation of sulfides to sulfoxides and sulfones, bayer-villeger reaction, bromination and iodation of aniline and phenol derivatives oxidative esterification, oxidation of pyridines and oxidation of secondary, allylic and benzyllic alcohols were carried out using 1,1,2,2-Tetrahydroperoxy-1,2-Diphenylethane as the potential solid oxidant which can be stored for several months without any loss in its activity. All of the procedures were accomplished via mild reaction conditions and the products were afforded in high yields and short reaction times.
- Khosravi, Kaveh,Naserifar, Shirin
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supporting information
p. 6584 - 6592
(2018/10/05)
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- Synthesis, kinetics, and mechanism of bromophenols by N-bromophthalimide in aqueous acetic acid
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The kinetics and mechanism of bromination of phenol and its substituents, viz. 4-chlorophenol, 4-bromophenol, 4-methylphenol, and 4-methoxyphenol by N-bromophthalimide (NBP) in the presence of mercuric acetate in the temperature range of 303–318?K in aqueous acetic acid medium have been investigated. The reaction follows first-order dependence on [NBP] and fractional order dependence of rate on [Phenol]. The activation parameters have been evaluated, and based on the observed kinetic results the probable mechanism has been proposed. Observed kinetic features and Hammett's reaction constant (ρ) suggests that bromination occurs through electrophilic substitution of bromonium ion (Br+) into the aromatic ring in the transition state. Large negative entropy of activation values probably suggests the rigid nature of transition state.
- Anjaiah, Birla,Prameela, Kethavath,Srinivas, Pabba,Rajanna, Kamatala Chinna
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p. 804 - 812
(2018/09/11)
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- 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
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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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- Practical, mild and efficient electrophilic bromination of phenols by a new I(iii)-based reagent: The PIDA-AlBr3 system
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A practical electrophilic bromination procedure for phenols and phenol-ethers was developed under efficient and very mild reaction conditions. A broad scope of arenes was investigated, including the benzimidazole and carbazole core as well as analgesics such as naproxen and paracetamol. The new I(iii)-based brominating reagent PhIOAcBr is operationally easy to prepare by mixing PIDA and AlBr3. Our DFT calculations suggest that this is likely the brominating active species, which is prepared in situ or isolated after centrifugation. Its stability at 4 °C after preparation was confirmed over a period of one month and no significant loss of its reactivity was observed. Additionally, the gram-scale bromination of 2-naphthol proceeds with excellent yields. Even for sterically hindered substrates, a moderately good reactivity is observed.
- Satkar, Yuvraj,Ramadoss, Velayudham,Nahide, Pradip D.,García-Medina, Ernesto,Juárez-Ornelas, Kevin A.,Alonso-Castro, Angel J.,Chávez-Rivera, Ruben,Jiménez-Halla, J. Oscar C.,Solorio-Alvarado, César R.
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p. 17806 - 17812
(2018/05/28)
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- Green halogenation reactions for (hetero)aromatic ring systems in alcohol, water, or no solvent
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A new method of brominating aromatic and heteroaromatic ring systems is investigated. The combination of hydrobromic acid as the halogen source, hydrogen peroxide as the oxidant, and ethanol, water, or no solvent are evaluated as greener conditions than those that have been previously published. The new conditions give high yields and good regioselectivity for a variety of substrates when the ring is activated by electron-donating groups or heteroatoms. Phenols, anisole, thiophenes, and pyrrole give comparable or superior results when compared to a traditional bromination by N-bromosuccinimide in tetrahydrofuran. Other nitrogen-containing heterocycles do not react under the conditions because they are protonated and hence deactivated; similarly, substrates with electron-withdrawing groups are not brominated. The reaction is very tolerant of a variety of functional groups.
- Kajorinne, Jessie K.,Steers, Jennifer C.M.,Merchant, Marnie E.,MacKinnon, Craig D.
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p. 1087 - 1091
(2018/11/25)
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- A bromo-capped diruthenium(i,i) N-heterocyclic carbene compound for in situ bromine generation with NBS: Catalytic olefin aziridination reactions
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A bromo-capped metal-metal bonded diruthenium(i,i) complex Ru2(CO)4(PIN)2Br2 (1) (PIN = 1-isopropyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazol-2-ylidene) generates bromine with N-bromosuccinimide (NBS) at room temperature. Cycloalkene and stilbene are readily brominated by stoichiometric reactions with 1 and NBS. An analysis of the dibrominated products suggests the formation of cyclic bromonium intermediates indicating in situ Br2 generation. Complex 2, an iodide analogue of 1, is also synthesized. The reaction of 2 with N-iodosuccinimide releases I2, which is confirmed by the starch-iodine test. The catalytic utility of 1 is examined for the bromination of phenol. Catalyst 1, in combination with NBS and base, exhibits regioselectivity towards monobrominated products. Furthermore, efficient olefin aziridination is demonstrated utilizing catalyst 1 in the presence of NBS, K2CO3 and TsNH2.
- Sengupta, Gargi,Pandey, Pragati,De, Subhabrata,Ramapanicker, Ramesh,Bera, Jitendra K.
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supporting information
p. 11917 - 11924
(2018/09/10)
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- Bromine formation in solid NaBr/KNO3 mixture and assay of this reaction via bromination of activated aromatics
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Bromine formation in the mixture of solid NaBr and KNO3 was observed and the process was studied in different acidified organic solvent–water mixtures by monitoring the bromination of acetanilide and other compounds, containing activated aromatic substituents. This assay is based on fast bromination reaction of these aromatic compounds, as differently from the assay of Br2, the brominated aromatics can be easily determined by conventional gas chromatography–mass spectrometry (GC–MS) methods. It was found that bromine was generated autocatalytically on the surface of salt crystals and the reaction was characterized by a lag period, the duration of which depended on reaction conditions, and importantly on the type of the organic solvent in the reaction mixture. As the bromine formation could be easily controlled by reaction conditions, it was suggested that the studied reaction might have practical applications as an environmentally friendly and economically feasible bromination method. It was also shown that the bromination of aromatics followed the mechanism of classical electrophilic aromatic substitution reaction.
- Rahu, Ida,Keki?ev, Ott,J?rv, Jaak,Burk, Peeter
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p. 2893 - 2898
(2018/08/23)
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- Preparation method of tris(2, 4-dibromophenyl)phosphate
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The invention relates to a preparation method of tris(2, 4-dibromophenyl)phosphate. The preparation method is capable of solving technical problems in the prior art that tris(2, 4-dibromophenyl)phosphate (BPP) product yield is low, impurity content is high, technology operation is complex, and cost is high. According to the preparation method, a halogenated hydrocarbon and a low fatty alcohol aremixed so as to obtain a mixed solvent, strong acid catalysis is adopted to prepared high purity 2,4-dibromophenol, a weak base is adopted for neutralization of an obtained system to protect phenolic hydroxyl groups from reaction with alkaline substances, an anti-oxidant is adopted to avoid oxidation of the phenolic hydroxyl groups by the air, so that high yield high transparency 2,4-dibromophenolis obtained. In the synthesis process of tris(2, 4-dibromophenyl)phosphate, under solvent free conditions, temperature segment reaction is carried out under Lewis acid catalytic effect, so that product yield is increased greatly; the cooperation of water and an emulsifier is capable of realizing applications of products in the field of transparent material flame resistance. The preparation methodis widely used in the field of fire retardant synthesis.
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Paragraph 0027-0029; 0034-0037; 0040-0043; 0046-0049
(2018/10/11)
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- Synthesis of new oxido-vanadium complexes: Catalytic properties and cytotoxicity
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Reaction of 2,3-dihydroxy benzaldehyde with 2-({2-amino phenyl}diazenyl)phenol afforded the ligand 3-(2-(2-hydroxyphenyl)diazenyl)- 4-alkylphenyliminomethyl)benzene-1,2-diol. Reaction of H2L with VOSO4. 5H2O gave the oxido-vanadium(IV) complexes [(L)VO], which exhibited a quasi-reversible oxidative cyclic voltammetric response in a V(IV)/V(V) oxidative process. The complexes act as catalysts in the oxidation of organic thioethers and bromination of phenol. Their cytotoxic properties were examined for three cancer cell lines.
- Das, Uttam,Pattanayak, Poulami,Santra, Manas Kumar,Chattopadhyay, Surajit
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- Preparation method of flame retardant for inflammable hazardous chemical plastic products
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The invention discloses a preparation method of a flame retardant for inflammable hazardous chemical plastic products. The method includes the steps of: 1) in an aliphatic-series halogenated solvent, dissolving phenol, performing a dropwise-adding reaction under stirring with bromine, slowly increasing the temperature until the boiling range of the solvent, and performing reflux to prepare a dibromo (tribromo) phenol aliphatic-series halogenated solution; 2) slowly dropwise adding a newly distilled industrial product phosphorus oxychloride, and slowly dropwise adding diluted triethylamine into the reaction bottle, and then slowly increasing the temperature so as to perform a reaction to the solvent at boiling temperature; 3) maintaining stable reflux to prepare tri(2,4-dibromophenyl) phosphate or tri(2,4,6-tribromophenyl) phosphate; and 4) water-washing and re-crystallizing the product to obtain the flame retardant. The flame retardant is toxic-free, is low in melt point, has good thermostability and compatibility, is good in flame retarding effect, and can be widely used in engineering plastics and alloys, such as nitro-cotton, celluloid and the like.
- -
-
Paragraph 0008; 0027-0033
(2017/09/28)
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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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- Vanadium bromoperoxidase (VBrPO) mimics: Synthesis, structure and a comparative account of the catalytic activity of newly synthesized oxidovanadium and oxido-peroxidovanadium complexes
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The bioinspired catalytic activities of two newly synthesised vanadium(iv)dioxido (complex 1) and vanadium(v) oxido-peroxido (complex 2) complexes with the neutral tridentate benzimidazole ligand, 2,6-di-(1H-benzo[d]imidazol-2-yl)pyridine (Byim) have been established. The bromoperoxidase activities of these complexes have been established through the activation of C-H bonds of substrates like phenol, o-cresol and p-cresol. The products, characterized by GC analysis shows that good conversions have been achieved. Considering the catalytic efficiency of the complexes, complex 2, with one in-built peroxido group is found to be more potent than complex 1. The catalytic cycles of both the complexes have been established from experimental results.
- Palmajumder, Eshita,Patra, Swarup,Drew, Michael G. B.,Mukherjea, Kalyan K.
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p. 8696 - 8703
(2016/10/13)
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- Rapid, photocatalytic, and deep debromination of polybrominated diphenyl ethers on Pd-TiO2: Intermediates and pathways
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Titanium dioxide with surface-loaded palladium (Pd-TiO2) was able to easily remove all ten bromine atoms from decabromodiphenyl ether (BDE209) within 1 h under the irradiation of sunlight or an artificial light source. By contrast, fewer than three bromine atoms were eliminated on the pristine TiO2 even with prolonged irradiation (5 h). During the photocatalytic debromination, moreover, the formed BDE intermediates exhibited a significant difference between the Pd-TiO2 and pristine TiO 2 systems, and much less position selectivity for the debromination on Pd-TiO2 was observed than that on the pristine TiO2 surface. For another polybrominated diphenyl ether (BDE15), pristine TiO 2 was incapable of its photocatalytic reduction, whereas the loading of Pd enabled its debromination to diphenyl ether within 20 min. In addition, an evident induction period appeared in the photocatalytic debromination of BDE15 on Pd-TiO2. The experiments imply that the Pd-cocatalyzed effect changes significantly the photocatalytic reductive debromination pathways.
- Li, Lina,Chang, Wei,Wang, Ying,Ji, Hongwei,Chen, Chuncheng,Ma, Wanhong,Zhao, Jincai
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p. 11163 - 11170,8
(2015/02/02)
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- Visible-light photoredox catalysis enabled bromination of phenols and alkenes
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A mild and efficient methodology for the bromination of phenols and alkenes has been developed utilizing visible light-induced photoredox catalysis. The bromine was generated in situ from the oxidation of Br- by Ru(bpy)33+, both of which resulted from the oxidative quenching process.
- Zhao, Yating,Li, Zhe,Yang, Chao,Lin, Run,Xia, Wujiong
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p. 622 - 627
(2014/04/17)
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- Vanadate-dependent bromoperoxidases from Ascophyllum nodosum in the synthesis of brominated phenols and pyrroles
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Bromoperoxidases from the brown alga Ascophyllum nodosum, abbreviated as VBrPO(AnI) and VBrPO(AnII), show 41% sequence homology and differ by a factor of two in the percentage of α-helical secondary structures. Protein monomers organize into homodimers for VBrPO(AnI) and hexamers for VBrPO(AnII). Bromoperoxidase II binds hydrogen peroxide and bromide by approximately one order of magnitude stronger than VBrPO(AnI). In oxidation catalysis, bromoperoxidases I and II turn over hydrogen peroxide and bromide similarly fast, yielding in morpholine-4-ethanesulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) molecular bromine as reagent for electrophilic hydrocarbon bromination. Alternative compounds, such as tribromide and hypobromous acid are not sufficiently electrophilic for being directly involved in carbon-bromine bond formation. A decrease in electrophilicity from bromine via hypobromous acid to tribromide correlates in a frontier molecular orbital (FMO) analysis with larger energy gaps between the π-type HOMO of, for example, an alkene and the σ*Br,X-type LUMO of the bromination reagent. By using this approach, the reactivity of substrates and selectivity for carbon-bromine bond formation in reactions mediated by vanadate-dependent bromoperoxidases become predictable, as exemplified by the synthesis of bromopyrroles occurring naturally in marine sponges of the genera Agelas, Acanthella, and Axinella. The Royal Society of Chemistry.
- Wischang, Diana,Radlow, Madlen,Hartung, Jens
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p. 11926 - 11940
(2013/09/02)
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- Green halogenation of aromatic heterocycles using ammonium halide and hydrogen peroxide in acetic acid solvent
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The green generation of X+ (X = Br, I) using hydrogen peroxide in aqueous acetic acid allows access to aromatic heterocyclic halides in yields and purities comparable to syntheses employing N-bromosuccinimide. In activated and unsubstituted thiophene rings, regioselectivity is quantitative for positions α to the sulfur; pyrroles also give quantitative reactions, at least initially. Deactivated rings, including furans and thiazoles, as well as thiophenes with strongly electron-withdrawing groups showed little to no reactivity under the conditions investigated. The reaction shows remarkable functional group tolerance (to alcohol, nitro, alkyl, halo, and carbonyl groups), as shown through reaction with substituted phenols. In all bromination reactions, reaction yields and regiochemistry were very similar to reactions involving N-bromosuccinimide in tetrahydrofuran solvent.
- D'Aleo, Danielle N.,Allard, Sheena R.,Foglia, Cassandra C.,Parent, Shawna L.M.,Rohr, David J.,Gottardo, Christine,MacKinnon, Craig D.
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p. 679 - 683
(2013/08/23)
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- Debromination of 2,4,6-tribromophenol coupled with biodegradation
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The application effect of aluminium and their alloys and mixtures with nickel was studied for the complete hydrodebromination of 2,4,6-tribromophenol (TBP) to phenol in aqueous NaOH solution at room temperature. It was found that the Raney Al-Ni alloy can
- Weidlich, Tomas,Prokes, Lubomir,Pospisilova, Dagmar
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p. 979 - 987
(2014/03/21)
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- Hydrodebromination of 2,4,6-tribromophenol in aqueous solution using Devarda's alloy
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The effectiveness of application of aluminium and its alloys and mixtures with copper was studied for complete hydrodebromination of 2,4,6-tribromophenol to phenol in aqueous NaOH solution at room temperature. Dissolved metals were removed using precipita
- Weidlich, Tomá?,Krej?ová, Anna,Proke?, Lubomír
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p. 155 - 162
(2013/07/27)
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- Synthesis, structural characterization, VHPO mimicking peroxidative bromination and DNA nuclease activity of oxovanadium(v) complexes
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The two novel oxovanadium(v) complexes [VO(PyDC)(BHA)] (1) [PyDC = pyridine-2,6-dicarboxylate, BHA = benzohydroxamate] and [VO(PyDC)(BPHA)] (2) [BPHA = benzophenyl hydroxamate] were synthesized by successive addition of a methanolic solution of H2PyDC and the corresponding hydroxamic acid ligand to the aqueous solution of ammonium metavanadate (NH4VO 3). The hydroxamic acid ligands were characterized by elemental analysis, IR, UV-vis and NMR studies whereas the complexes were characterized by IR, UV-vis, CHN, molar conductance, magnetic moment, mass and NMR spectroscopic methods. The structures of the complexes were determined by single crystal X-ray crystallography. The structures of both complexes reveal that vanadium(v) has distorted octahedral geometry. The bromoperoxidase activities of these complexes have been demonstrated through the activation of C-H bonds of phenol, o-cresol and p-cresol. The catalytic products have been characterized by GC-MS analysis which shows that good conversions have been achieved. So far as the catalytic efficiency of the complexes are concerned complex 2 is found to be superior to complex 1. Both the complexes were tested for DNA nuclease activity with pUC19 plasmid DNA. The results show that both of them exhibited nuclease activity against pUC19 circular plasmid DNA. The complexes produced both nicked coils and linear forms. In this case also it is observed that complex 2 shows better nuclease activity than complex 1.
- Patra, Swarup,Chatterjee, Suparna,Si, Tapan Kr.,Mukherjea, Kalyan K.
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p. 13425 - 13435
(2013/09/23)
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- Green, mild and efficient bromination of aromatic compounds by HBr promoted by trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane in water as a solvent
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A combination of HBr and trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane as a new and powerful oxidant was found effective for facile bromination of different aromatic compounds at room temperature in water as a green solvent. Mild reaction conditions, high selectivity and yield, high reaction rate and non-toxicity are some of the major advantages of this synthetic protocol.
- Khosravi, Kaveh,Kazemi, Samira
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experimental part
p. 387 - 390
(2012/05/20)
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- Regioselective bromination and iodination of aromatic substrates promoted by trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane
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Selective and efficient bromination and iodination of aromatic compounds by ammonium bromide and ammonium iodide, respectively, under promotion of trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane have been explored. Mild reaction conditions, high selectivity and yield, and high reaction rate are some of the major advantages of this synthetic method.
- Azarifar, Davood,Khosravi, Kaveh,Najminejad, Zohreh,Soleimani, Khadijeh
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experimental part
p. 321 - 326
(2012/08/14)
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- Cu-Mn spinel oxide catalyzed regioselective halogenation of phenols and N-heteroarenes
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A novel simple, mild chemo- and regioselective method has been developed for the halogenation of phenols using Cu-Mn spinel oxide as a catalyst and N-halosuccinimide as halogenating agent. In the presence of Cu-Mn spinel oxide B, both electron-withdrawing and electron-donating groups bearing phenols gave monohalogenated products in good to excellent yields with highest para-selectivity. The para-substituted phenol gave monohalogenated product with good yield and ortho-selectivity. N-Heteroarenes such as indoles and imidazoles also gave monohalogenated products with high selectivity. Unlike the copper-catalyzed halogenation, the present method works well with electron-withdrawing group bearing phenols and gives comparatively better yields and selectivity. The Cu-Mn spinel catalyst is robust and reused three times under optimized conditions without any loss in catalytic activity. Nonphenolics did not undergo this transformation.
- Singh, Parvinder Pal,Thatikonda, Thanusha,Kumar, K. A. Aravinda,Sawant, Sanghapal D.,Singh, Baldev,Sharma, Amit Kumar,Sharma,Singh, Deepika,Vishwakarma, Ram A.
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scheme or table
p. 5823 - 5828
(2012/09/05)
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- Bromination of phenols in bromoperoxidase-catalyzed oxidations
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Phenol and ortho-substituted derivatives furnish products of selective para-bromination, if treated with sodium bromide, hydrogen peroxide, and the vanadate(V)-dependent bromoperoxidase I from the brown alga Ascophyllum nodosum. Relative rates of bromination in morpholine-4-ethane sulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) increase by a factor 32, as the ortho-substituent in a phenol changes from F via Cl, OCH3, C(CH 3)3, and H to CH3. The polar effect in phenol bromination by the enzymatic method, according to a Hammett-correlation (ρ=-3), compares to reactivity of molecular bromine under identical conditions (ρ=-2). Hypobromous acid is not able to electrophilically substitute bromine for hydrogen at pH 6.2 in aqueous tert-butanol. The tribromide anion behaves in MES-buffered aqueous tert-butanol as electrophile (ρ~-3), showing a similar polar effect in phenol bromination as molecular bromine.
- Wischang, Diana,Hartung, Jens
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p. 9456 - 9463
(2012/11/07)
-
- Brominated methanes as photoresponsive molecular storage of elemental Br2
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The photochemical generation of elemental Br2 from brominated methanes is reported. Br2 was generated by the vaporization of carbon oxides and HBr through oxidative photodecomposition of brominated methanes under a 20 W low-pressure mercury lamp, wherein the amount and situations of Br2 generation were photochemically controllable. Liquid CH 2Br2 can be used not only as an organic solvent but also for the photoresponsive molecular storage of Br2, which is of great technical benefit in a variety of organic syntheses and in materials science. By taking advantage of the in situ generation of Br2 from the organic solvent itself, many organobromine compounds were synthesized in high practical yields with or without the addition of a catalyst. Herein, Br2 that was generated by the photodecomposition of CH2Br2 retained its reactivity in solution to undergo essentially the same reactions as those that were carried out with solutions of Br2 dissolved in CH 2Br2 that were prepared without photoirradiation. Furthermore, HBr, which was generated during the course of the photodecomposition of CH2Br2, was also available for the substitution of the OH group for the Br group and for the preparation of the HBr salts of amines. Furthermore, the photochemical generation of Br2 from CH2Br2 was available for the area-selective photochemical bleaching of natural colored plants, such as red rose petals, wherein Br2 that was generated photochemically from CH 2Br2 was painted onto the petal to cause radical oxidations of the chromophoric anthocyanin molecules. The generation of Br 2 from brominated methanes occurred upon photoirradiation under O2. The solutions that contained elemental Br2 were useful for the synthesis of organobromine compounds and the macroscopic photochemical bleaching of colored plants. Copyright
- Kawakami, Kazumitsu,Tsuda, Akihiko
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p. 2240 - 2252
(2012/11/06)
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- Regioselective and high-yielding bromination of phenols and anilins using N-bromosaccharin and amberlyst-15
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A regioselective and facile conversion method for bromination of anilines and phenols using N-bromosaccharine in the presence of a catalytic amount of Amberlyst-15 lead to enhancement of the reaction rate and yielded brominated products in good to excellent yields and short reaction times.
- Baharfar,Alinezhad,Azimi,Salehian
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experimental part
p. 863 - 865
(2012/04/23)
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- Efficient, rapid, and regioselective bromination of phenols and anilines with N-bromosaccharin using tungstophosphoric acid as a heterogeneous recyclable catalyst
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A simple, efficient, and rapid method for high-yielding regioselective mono bromination of phenols and anilines has been achieved by treatment with N-bromasaccharin in the presence of a catalytic amount of tungstophosphoric acid. Copyright Taylor & Francis Group, LLC.
- Alinezhad, Heshmatollah,Tavakkoli, Sahar Mohseni,Salehian, Fatemeh
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experimental part
p. 3226 - 3232
(2010/12/24)
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- Efficient and regioselective bromination of aromatic compounds with ethylenebis(N-methylimidazolium) ditribromide (EBMIDTB)
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A regioselective and highly efficient method for bromination of phenol and aniline derivatives using ethylenebis(N-methylimidazolium) ditribromide (EBMIDTB) as an efficient reagent in dichloromethane at ambient temperature is reported. The reagent can be recovered and reused several times.
- Hosseinzadeh, Rahman,Tajbakhsh, Mahmood,Mohadjerani, Maryam,Lasemi, Zahra
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experimental part
p. 868 - 876
(2010/05/18)
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- Facile p-toluenesulfonic acid-promoted para-selective monobromination and chlorination of phenol and analogues
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para-Regioselective bromination of phenol and analogues, promoted by p-toluenesulfonic acid, is achieved in high to excellent yields at room temperature with N-bromosuccinimide. Chlorination with N-chlorosuccinimide and catalysed by p-toluenesulfonic acid also gives para-chlorinated phenol analogues in good yields at room temperature. para-Bromination of phenol, promoted by p-toluenesulfonic acid, is achieved in excellent yields at room temperature with N-bromosuccinimide. p-Toluenesulfonic acid is also effective as a promoter of para-chlorination with N-chlorosuccinimide.
- Bovonsombat, Pakorn,Ali, Rameez,Khan, Chiraphorn,Leykajarakul, Juthamard,Pla-On, Kawin,Aphimanchindakul, Suraj,Pungcharoenpong, Natchapon,Timsuea, Nisit,Arunrat, Anchalee,Punpongjareorn, Napat
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experimental part
p. 6928 - 6935
(2010/10/01)
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- Sequential bromination reactions from beads with methyltriphenylphosphonium tribromide groups
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A reusable bromination reagent based on polystyrene beads with covalently appended methyltriphenylphosphonium tribromide groups has been developed. The results from bromination reactions of several structurally diverse unsaturated substrates with the beads and with solutions of a non-polymeric model brominating reagent, methyltriphenylphosphonium tribromide, are described. It is shown that the reactions are highly regio- and stereo-selective and can be conducted easily. Copyright
- Cristiano, Rodrigo,Walls, Andrew D.,Weiss, Richard G.
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supporting information; experimental part
p. 904 - 909
(2011/09/14)
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- Regioselective bromination of organic substrates by LDH-CO3 2--Br- promoted by V2O5-H 2O2
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An efficient, fast, simple, mild, and selective monobromination of aromatic compounds, with high para-selectivity, is reported. The catalytic system is readily prepared from a Mg-Al-layered double hydroxide-CO3 2--Br- (LDH-CO32--Br-) as the source of bromide, V2O5 as a promoter and hydrogen peroxide as the oxidant. The use of hydrogen peroxide as a synthetically useful oxidizing agent is reported for generating electrophilic bromine in situ from easily available KBr as a bromine source, to brominate electron rich aromatic compounds, employing LDH-CO32--Br3- as the phase-transfer catalyst. The phase-transfer catalyst leads to nearly complete bromination in 3 h at room temperature with high selectivity. The reaction rate of p-bromoanisole and p-bromotoluene formation by LDH-CO 32--Br3- in a triphasic system was studied. The heterogeneity of the reaction system facilitates the recovery and recycling of the catalyst, and the reagent components are environmentally acceptable. The catalyst, LDH-CO32--Br3 -, and its precursors, LDH-CO32--Br- and LDH-CO32-, were characterized by powder XRD, FT-IR and UV-vis spectroscopy.
- Ghiaci,Sedaghat,Ranjbari,Gil
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experimental part
p. 18 - 26
(2011/01/05)
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- Solvent-free phase-vanishing reactions with PTFE (Teflon) as a phase screen
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In a solvent-free phase-vanishing reaction with PTFE (polytetrafluoroethylene, Teflon) tape as the phase screen, a thermometer adapter is utilized to insert a PTFE-sealed tube into the vapor phase above the substrate. Besides avoiding use of solvents, the experimental design is not dependent upon the densities of the reactants and the procedure generates little or no waste while providing the reaction products in high yield and in high purity.
- Pels, Kevin,Dragojlovic, Veljko
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scheme or table
(2010/04/22)
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- Phase-vanishing reactions with ptfe (teflon) as a phase screen
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Phase-vanishing reactions are triphasic reactions, which involve a reagent, a liquid perfluoroalkane, and a substrate. In a phase-vanishing reaction with PTFE tape as the phase screen instead of a liquid perfluoroalkane, there is no limitation related to the density of a phase and the denser phase can be in the top layer. The reactions were faster compared to traditional PV reactions, and it was possible to carry out sequential and tandem reactions and reactions under a reflux.
- Van Zee, Nathan J.,Dragojlovic, Veljko
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supporting information; experimental part
p. 3190 - 3193
(2009/11/30)
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- Regioselective, photochemical bromination of aromatic compounds using N-bromosuccinimide
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Regioselective nuclear bromination of aromatic compounds is investigated with N-bromosuccinimide as the brominating agent under UV irradiation to afford the corresponding brominated compounds. The reaction proceeds at ambient temperature (30 ± 2 °C) without any catalyst. In most of the reactions, regioselectively mono-brominated products are obtained in good to high yields. The conversion and selectivity for bromination depend on the nature of the substituent on the aromatic ring.
- Chhattise, Prakash K.,Ramaswamy,Waghmode, Suresh B.
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p. 189 - 194
(2008/03/30)
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- Stereoselective bromination reactions using tridecylmethylphosphonium tribromide in a "stacked" reactor
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(Chemical Equation Presented) A new reagent, tridecylmethylphosphonium tribromide, and new procedures for bromination reactions of unsaturated substrates (including one that allows several substrates to be reacted in sequence) are described. The procedures exploit the diffusion of components and the densities and immiscibilities of layers, including a fluorous "spacer" layer, within a reaction vessel. The stereoselectivities achieved in the reactions are superior in some cases to those found with other brominating reagents.
- Ma, Kefeng,Li, Shaw,Weiss, Richard G.
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supporting information; experimental part
p. 4155 - 4158
(2009/06/06)
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- Regioselective bromination of activated aromatic substrates with a ZrBr4/diazene mixture
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A regioselective method for the bromination of phenols, ethers and anilines using a ZrBr4/diazene mixture is described. The reaction takes place under mild reaction conditions and the bromine atom adds first at the para unsubstituted position with respect to the OH, OR or NR2 group of the activated aromatic substrate. Less reactive compounds such as toluene, phenyl acetate, benzonitrile and trifluoromethylbenzene remain intact under the same conditions.
- Stropnik, Tadej,Bombek, Sergeja,Ko?evar, Marijan,Polanc, Slovenko
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p. 1729 - 1733
(2008/09/18)
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- {[K.18-Crown-6]Br3}n: a unique tribromide-type and columnar nanotube-like structure for the oxidative coupling of thiols and bromination of some aromatic compounds
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Reaction of 18-crown-6 with KBr and then with bromine (Br2) afforded a unique tribromide salt with a nanotube-like structure ({[K.18-crown-6]Br3}n). Oxidative coupling of thiols and bromination of some aromatic compounds is the first report on the chemistry of this reagent.
- Zolfigol, Mohammad Ali,Chehardoli, Gholamabbas,Salehzadeh, Sadegh,Adams, Harry,Ward, Michael D.
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p. 7969 - 7973
(2008/03/14)
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- Regioselective aromatic electrophilic bromination with dioxane dibromide under solvent-free conditions
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Highly regioselective ring bromination of aromatic compounds has been accomplished with high yields and good purity using dioxane dibromide (DD) under solvent-free conditions. Notable features of this methodology include operational simplicity, rapid reactions, excellent control over the degree of bromination, and tolerance of various functional groups during the reaction. Copyright Taylor & Francis Group, LLC.
- Chaudhuri, Subrata Kumar,Roy, Sanchita,Saha,Bhar, Sanjay
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p. 581 - 585
(2007/10/03)
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- Photocyclization of 2-chloro-substituted 1,3-diarylpropan-1,3-diones to flavones
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The photochemical behavior of 2-halo-substituted 1,3-diarylpropan-1,3-dione strongly depends on the nature of the halogen atom bonded and the presence of electron-donor groups on the phenyl ring. In the case of 2-chloro-1,3- diphenylpropan-1,3-dione and 1-(3,5-dimethoxyphenyl)-3-phenylpropan-1,3-dione, cyclization to flavones was the sole reaction pathway, whereas in the case of 2-chloro-1,3-di(4-methoxyphenyl)-propan-1,3-dione, only products derived from α-cleavage were observed. 2-Fluoro derivatives of 1,3-diarylpropan-1,3- diones were photostable; on the other hand, 2-chloro-2-fluoro derivates resulted in 3-fluoroflavones.
- Kosmrlj, Berta,Sket, Boris
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p. 3993 - 3996
(2008/02/11)
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- Sol-gel entrapped pyridinium hydrobromide perbromide as a recyclable bromination agent: Its application to a one-pot bromination and dehydrobromination process
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Silica sol-gel encaged pyridinium hydrobromide perbromide can be used for clean, odorless bromination of a variety of substrates, including alkenes, ketones, and arenes. The used heterogenized bromination reagent can be recharged with bromine and recycled. In the presence of sol-gel entrapped 1,5,7-triazabicyclo[4.4.0]dec-5-ene, dibromides are dehydrobrominated to give vinyl monobromides and/or alkynes. Encapsulation of the pyridinium derivative and the guanidine base within separate sol-gel matrices enables the use of both opposing reagents in one-pot reactions without their mutual destroying each other. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Levin, Yevgenia,Hamza, Khalil,Abu-Reziq, Raed,Blum, Jochanan
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p. 1396 - 1399
(2007/10/03)
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- Simple bromination of activated arenes by IBX amide resin and tetraethyl-ammonium bromide
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A mild and operationally simple method of brominating activated aromatic compounds using a polymer supported IBX reagent (IBX amide resin) and tetraethylammonium bromide (TEAB) was developed. The activated aromatics, when reacted with IBX amide resin in the presence of TEAB, were easily converted into the brominated aromatics in high yields (>80%) at room temperature.
- Kim, Duk-Ki,Chung, Woo-Jae,Lee, Yoon-Sik
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p. 279 - 282
(2007/10/03)
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- Bromination of hydroxyaromatic compounds
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A method for brominating hydroxyaromatic compounds to form products, such as p-bromophenol, is disclosed. The method uses elemental bromine as the brominating agent and comprises contacting a hydroxyaromatic compound with bromine and oxygen in the presence of metal catalyst. Suitable catalysts include elemental copper, copper compounds, and compounds of Group IV-VIII transition metals.
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Page/Page column 3-4
(2008/06/13)
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- An intriguing effect of lithium perchlorate dispersed on silica gel in the bromination of aromatic compounds by N-bromosuccinimide
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A convenient and efficient procedure for electrophilic aromatic bromination has been developed by mixing of N-bromosuccinimide and an aromatic compound at room temperature on the surface of silica gel mixed with solid anhydrous LiClO4. All of the substrates examined underwent clean electrophilic aromatic bromination in reaction times of a few minutes to afford the corresponding bromoarenes under neutral conditions in excellent yield. In the case of thiophenol, no substitution reaction occurred, and the corresponding disulfide was obtained in excellent yield.
- Bagheri, Mojtaba,Azizi, Najmedin,Saidi, Mohammad R.
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p. 146 - 149
(2007/10/03)
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- Bromination of hydroxyaromatic compounds and further conversion to dihydroxyaromatic compounds
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Brominated hydroxyaromatic compounds such as p-bromophenol are prepared by contacting a hydroxyaromatic compound with oxygen and a bromine source such as hydrogen bromide or an alkali metal or alkaline earth metal bromide in an acidic medium, in the presence of elemental copper or a copper compound as catalyst. The brominated product of this reaction may be converted alternately to a dihydroxyaromatic compound such as hydroquinone by hydrolyses, or a dihydroxybiphenyl compound such as 4,4′-dihydroxybiphenyl by reductive coupling.
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- Method of preparing mixtures of bromophenols and benzoquinones
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A method is described for the simultaneous preparation of 4-bromophenols and p-benzoquinones, intermediates useful in the preparation of hydroquinones and 4,4′-dihydroxybiphenyls respectively. Hydroquinones and 4,4′-dihydroxybiphenyls are useful monomers for the preparation of a variety of polymers. In one example phenol is reacted with in the presence of HBr, a catalytic amount of cupric bromide and a stoichiometric excess of oxygen under relatively mild conditions to provide a mixture of the phenol, 4-bromophenol, and 1,4-benzoquinone. Phenol conversion was 54 percent and selectivities for bromophenol and benzoquinone were 23% and 37% respectively. Limiting the amount of HBr present in the reaction mixture was shown to control the amount of benzoquinone produced.
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Page column 8
(2008/06/13)
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