- Linear Paired Electrolysis—Realising 200 % Current Efficiency for Stoichiometric Transformations—The Electrochemical Bromination of Alkenes
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The generation of bromine by oxidation of bromide anions at the anode and reduction of molecular oxygen at the cathode to hydrogen peroxide resulted in the overall formation of two molecules of Br2 (=four electron oxidation) by passing just two electrons through the solution. The bromine was used for the bromination of alkenes and thereby a linear paired electrolysis was attained which resulted in current efficencies of up to 200 %. Also, the diiodination of cyclohexene as well as the electrophilic aromatic bromination of an electron-rich arene were realised both in 168 % current efficiencies.
- Strehl, Julia,Abraham, Marvin L.,Hilt, Gerhard
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supporting information
p. 9996 - 10000
(2021/03/31)
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- Dibrominated addition and substitution of alkenes catalyzed by Mn2(CO)10
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A practical method for the dibromination of alkenes without using molecular bromine is consistently appealing in organic synthesis. Herein, we report Mn-catalyzed dibrominated addition and substitution of alkenes only with N-bromosuccinimide, producing a variety of synthetically valuable dibrominated compounds in moderate to high yields. This journal is
- Chan, Albert S. C.,Jiang, Yi,Meng, Shanshui,Song, Xianheng,Zhang, Hong,Zou, Yong
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supporting information
p. 13385 - 13388
(2021/12/17)
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- Green bromination method
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The invention discloses a green bromination method, and belongs to the field of green organic chemistry. Under the conditions of room temperature, opening and neutrality, reaction raw materials are aromatic hydrocarbon, olefin, alkyne, tryptamine, tryptophane and derivatives thereof with different functional groups, a bromine source is MBrx (M is Fe , Fe , Ce and the like, and x is 2-3), and the unique oxidant is H2O2. Brominated alkanes, alkenes, aromatic hydrocarbons, pyrrolo-indolines and furo-indolines and derivatives thereof can be produced. The bromination reaction is carried out by using easily available and cheap reagents (such as FeBr2, CeB3 and H2O2) in the market and the solvent, and the method has the characteristics of mild reaction conditions, wide substrate application range, simple steps, easiness in operation and no need of separation, is a green, environment-friendly and safe bromination reaction method, and has a good application prospect.
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Paragraph 0068-0070
(2021/06/13)
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- Tandem Deoxygenation/Halogenation of N-Oxides Under Acylation Conditions: Scope and In Situ IR Spectroscopic Study
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Acylation of cyclic nitronates with acyl bromides produces 3-bromomethyl-substituted 5,6-dihydro-2H-1,2-oxazines via an unusual multi-stage process involving deoxygenation of N-oxide and the formation of Br2. Low-temperature in situ ATR FT-IR monitoring and DFT calculations revealed α-halo-substituted N,N-bis(oxy)amines as key intermediates of the process. The developed method was successfully exploited in the stereoselective synthesis of pharmaceutically relevant molecules.
- Malykhin, Roman S.,Golovanov, Ivan S.,Ioffe, Sema L.,Sukhorukov, Alexey Yu.
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p. 4139 - 4148
(2019/04/03)
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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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p. 11917 - 11924
(2018/09/10)
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- A Highly Efficient Method for the Bromination of Alkenes, Alkynes and Ketones Using Dimethyl Sulfoxide and Oxalyl Bromide
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The pairing of DMSO and oxalyl bromide is reported as a highly efficient brominating reagent for various alkenes, alkynes and ketones. This bromination approach demonstrates remarkable advantages, such as mild conditions, low cost, short reaction times, provides excellent yields in most cases and represents a very attractive alternative for the preparation of dibromides and α-bromoketones.
- Ding, Rui,Li, Jiaqi,Jiao, Wenyi,Han, Mengru,Liu, Yongguo,Tian, Hongyu,Sun, Baoguo
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p. 4325 - 4335
(2018/11/21)
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- Dibromination of alkenes with LiBr and H2O2 under mild conditions
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Electron-rich and electron-poor alkenes, and alkenes bearing protecting groups can be efficiently and stereoselectively converted to trans-dibromides using LiBr/H2O2 and AcOH as a proton source in 1,4-dioxane. For most substrates addition of 0.1 mol% of PhTeTePh enhances the reaction rate and the yield of the products. Experimental data suggest that the brominating agent prepared in situ is molecular bromine and that LiBr assists the activation of H2O2 allowing bromination to occur using AcOH as a mild proton source in uncatalyzed experiments. Scale-up is feasible: 10.0 mmol of 1-octene was quantitatively converted to 1,2-dibromooctene in one hour of reaction at room temperature.
- Martins, Nayara Silva,Alberto, Eduardo E.
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supporting information
p. 161 - 167
(2017/12/28)
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- Mild and Efficient Vicinal Dibromination of Olefins Mediated by Aqueous Ammonium Fluoride
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A mild and efficient vicinal dibromination of olefins has been developed by using saturated aqueous ammonium fluoride solution as the promoter. Inexpensive and commercially available N -bromosuccinimide (NBS) was used as the brominating reagent. The corresponding vicinal dibromoalkanes could be obtained in good to excellent yields.
- Ng, Wing Hin,Shing, Tony K. M.,Yeung, Ying-Yeung
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supporting information
p. 419 - 424
(2018/02/23)
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- Intermolecular Halogenation/Esterification of Alkenes with N-Halosuccinimide and Acetic Acid Catalyzed by 1,4-Diazabicyclo[2.2.2]octane
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1,4-Diazabicyclo[2.2.2]octane (DABCO) is a suitable Lewis base that acts as an organocatalyst in the activation of N-chlorosuccinimide (NCS) towards the chlorination of alkenes. The chloriranium ion formed from NCS and the alkene, can be intermolecularly opened by a nucleophile, such as acetic acid, to produce highly functionalized trans-chloro esters in high yields. The protocol is also applied to the synthesis of chlorohydrins and chloro ethers using water or methanol as nucleophiles instead of acetic acid. Brominated analogs can also be synthesized from alkenes and N-bromosuccinimide (NBS) in the presence of various basic catalysts. However, the reaction patterns seem to be remarkably different. The catalytic performance of bases in the bromoesterification of alkenes was found to be strongly affected by their Br?nsted basicity, suggesting that acetyl hypobromite, formed in situ from NBS and acetic acid, acts as a real brominating agent in these systems. (Figure presented.).
- Pimenta, Laura S.,Gusevskaya, Elena V.,Alberto, Eduardo E.
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supporting information
p. 2297 - 2303
(2017/07/07)
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- Preparation of manganese/Graphite oxide composite using permanganate and graphite: Application as catalyst in bromination of hydrocarbons
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A highly efficient one-pot preparation of manganese/graphite oxide (MnOX/GO) composite from graphite and KMnO4 is described. Hummers preparation method of GO requires a stoichiometric amount of KMnO4, as a result, the method produces a large amount of reduced Mn species. The Mn residue generally is a waste, therefore, we envisioned converting it to value-Added materials. A MnOX/GO composite was prepared in one-pot by treating the unpurified GO with aqueous KOH. The composite was characterized by XRD, XAFS, SEM and TEM. Among various applications of the MnOX/GO composite, we applied it as a recyclable catalyst for bromination of saturated hydrocarbons, one of the most basic but important chemical transformations. The MnOX/GO composite is expected to be an efficient catalyst because of the high surface area and high accessibility of substrates derived from the 2- dimensional sheet structure. When the reaction of a saturated hydrocarbon and Br2 in the presence of catalytic MnOX/GO was performed under fluorescent light irradiation, a brominated product was formed in high yield in a short reaction time. GO could strongly bind with Mn to prevent elution to the liquid phase, enabling the high recyclability.
- Suzuki, Hideyuki,Nishina, Yuta
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supporting information
p. 74 - 78
(2017/08/14)
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- Effective bromo and chloro peroxidation catalysed by tungsten(vi) amino triphenolate complexes
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Amino triphenolate tungsten(vi) complexes have been prepared and they proved to be efficient catalysts in haloperoxidation reactions using hydrogen peroxide as a terminal oxidant and inorganic sources of halides. In particular, interesting results have been obtained in the challenging chloroperoxidation reactivity (catalyst loading down to 0.05% with TONs up to 900). A comparison among three different metal complexes bearing the same ligand (vanadium(v), molybdenum(vi) and tungsten(vi)) showed much better performances of the last complex both on bromo and chloro peroxidations.
- Badetti, Elena,Romano, Francesco,Marchiò, Luciano,Ta?kesenlio?lu, Sara,Da?tan, Arif,Zonta, Cristiano,Licini, Giulia
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p. 14603 - 14608
(2016/09/28)
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- Efficient bromination of olefins, alkynes, and ketones with dimethyl sulfoxide and hydrobromic acid
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The oxidative bromination of olefins, alkynes, and ketones has been developed with HBr as the brominating reagent and DMSO as the mild oxidant. The simple conditions, high bromide-atom-economy, as well as easy accessibility and low cost of DMSO and HBr make the present strategy prospective for the synthesis of dibrominated alkanes, dibrominated alkenes and α-bromoketones.
- Song, Song,Li, Xinwei,Sun, Xiang,Yuan, Yizhi,Jiao, Ning
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supporting information
p. 3285 - 3289
(2015/06/25)
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- Bromination of olefins with HBr and DMSO
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A simple and inexpensive methodology is reported for the conversion of alkenes to 1,2-dibromo alkanes via oxidative bromination using HBr paired with dimethyl sulfoxide, which serves as the oxidant as well as cosolvent. The substrate scope includes 21 olefins brominated in good to excellent yields. Three of six styrene derivatives yielded bromohydrins under the reaction conditions.
- Karki, Megha,Magolan, Jakob
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p. 3701 - 3707
(2015/04/22)
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- Bromine and iodine-cucurbit[6]uril complexes: Preparation and applications in synthetic organic chemistry
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Iodine and bromine inclusion compounds were easily prepared by gas diffusion of the halogens using finely powdered CB[6]. A brown powder consisting of I2-CB[6]·4H2O and an orange one of (Br 2)4-CB[6]·10H2O were employed in several different reactions. I2-CB[6] can be used in catalytic reactions giving yields comparable to those reported in the literature. Br 2-CB[6] was effectively applied in electrophilic bromination of benzene and formation of bromohydrin. However, the radical substitution at cyclohexene could not be performed. Overall, based on these results, several applications can be envisioned for these complexes. This journal is the Partner Organisations 2014.
- Reddy,Cavallini,Demets,Silva
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supporting information
p. 2262 - 2264
(2014/06/09)
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- Revisiting the bromination of c-h bonds with molecular bromine by using a photo-microflow system
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The photobromination of C-H bonds by using molecular bromine was reinvestigated under microfluidic conditions. The continuous-flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated products with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition. Go with the (micro)flow: Photobromination of C-H bonds by using molecular bromine under microfluidic conditions has been investigated (see scheme). The continuous-flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated compounds with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition.
- Manabe, Yoshiyuki,Kitawaki, Yuriko,Nagasaki, Masahiro,Fukase, Koichi,Matsubara, Hiroshi,Hino, Yoshiko,Fukuyama, Takahide,Ryu, Ilhyong
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supporting information
p. 12750 - 12753
(2015/03/30)
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- 1,3,2,4-diazadiphosphetidine-based phosphazane oligomers as source of P(III) atom economy reagents: Conversion of epoxides to vic -haloalcohols, vic -dihalides, and alkenes in the presence of halogen sources
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1,3,2,4-Diazadiphosphetidines (P1-P3), as easily prepared, stable, and heterogeneous P(III) compounds, were used for the efficient conversion of epoxides to vic-halohydrins, vic-dihalides, or alkenes in the presence of different halogen sources in CH3CN. Of these phosphazanes, P3 is most suitable and contains 4 phosphorous atoms with the advantage of having greater atom economy and its phosphorus oxide byproduct can be easily separated from the reaction mixture by simple filtration. The nitrogen atoms in this molecule can also act as acid scavengers in the reaction.
- Iranpoor, Nasser,Firouzabadi, Habib,Etemadidavan, Elham
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p. 1165 - 1173
(2014/10/16)
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- Magnetic-nanoparticle-supported 2,2′-bis[3-(triethoxysilyl)propyl] imidazolium-substituted diethyl ether bis(tribromide): A convenient recyclable reagent for bromination
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A new magnetic-nanoparticle-supported bromination reagent was synthesized by anchoring a 2,2′-bis[3-(triethoxysilyl)propyl]imidazolium-substituted diethyl ether bis(tribromide) onto the surface of γ-Fe2O 3 nanoparticles and subsequently treating this new ionic liquid with bromine. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient bromination of a wide range of alkenes, alkynes, ketones, and aromatic substrates. More importantly, the reagent could be easily recovered by an external magnet and reused six times without significant loss of activity. A new maghemite nanoparticle bromination reagent has been prepared. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient bromination of a wide range of alkenes, alkynes, ketones, and aromatic substrates. Copyright
- Wu, Liqiang,Yin, Zhikui
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p. 6156 - 6163
(2014/01/06)
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- Aqueous Et4NBrO3/KBr as a versatile and environmentally benign source of bromine for the selective trans-bromination of alkenes
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An aqueous solution of tetraethyl ammonium bromate and potassium bromide is found to be an environmentally benign source of bromine at ambient temperature. This reagent is used for selective trans-dibromination of several substituted alkenes. The reaction conditions are mild and the yield of the products are high and other possible by-products such as bromohydrin formation and aromatic substitution have not been observed.
- Das, Pranab Jyoti,Sarkar, Sudeshna
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p. 802 - 806
(2013/07/26)
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- Direct sustainable bromination of alkenes in aqueous media and basic ionic liquids
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Electron-rich and electron-poor alkenes have been dibrominated using a rapid and sustainable procedure. The reactions were conducted in aqueous medium and basic ionic liquids which catalyzed the direct addition of bromine. The protocol leads to remarkable results, high yields under mild conditions, complete chemo- and stereo-selectivity and allows the recycling of ionic liquids, reducing costs, and environmental impact.
- Primerano, Patrizia,Cordaro, Massimiliano,Scala, Angela
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p. 4061 - 4063
(2013/07/25)
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- Alkoxybromination of olefins using ammonium bromide and oxone
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A mild, efficient, and highly regio- and stereoselective method for the methoxy and ethoxy bromination of olefins has been developed using NH 4Br as a bromine source and Oxone as an oxidant. Various kinds of olefins (aromatic, linear, and cyclic olefins) afforded the corresponding alkoxy brominated products in moderate to excellent yields. Taylor & Francis Group, LLC.
- Kumar, Macharla Arun,Naresh, Mameda,Rohitha, Chozhiyath Nappunni,Narender, Nama
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supporting information
p. 3121 - 3129
(2014/01/06)
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- Direct bromination of hydrocarbons catalyzed by Li2MnO 3 under oxygen and photo-irradiation conditions
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A method for the direct bromination of hydrocarbons with Br2 using a ubiquitous and inexpensive catalyst is highly desirable. Herein, we report the selective mono-bromination of hydrocarbons in good yield using Li2MnO3 as a catalyst under irradiation with a fluorescent room light. This new catalyst can be recycled. The effect of light was investigated using action spectra, which revealed that the reaction occurred on the surface of the catalyst.
- Nishina, Yuta,Morita, Junya,Ohtani, Bunsho
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p. 2158 - 2162
(2013/03/13)
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- Regio-and stereoselective hydroxybromination and dibromination of olefins using ammonium bromide and oxone
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An efficient protocol for the synthesis of vicinal bromohydrins and dibromides from olefins is presented. Various olefins are regio-and stereoselectively hydroxybrominated and dibrominated with anti fashion, following Markonikov's rule, using eco-friendly, non-toxic, and stable reagents such as NH4Br and oxone in CH3CN/H2O (1:1) and CH3CN without employing catalyst in moderate to excellent yields. Bromohydrins are formed instantaneously.
- MacHarla, Arun Kumar,Chozhiyath Nappunni, Rohitha,Nama, Narender
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supporting information; experimental part
p. 1401 - 1405
(2012/04/04)
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- Organocatalysis as a safe practical method for the stereospecific dibromination of unsaturated compounds
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Organocatalytic stereospecific dibromination of a wide variety of functionalized alkenes was achieved using a stable, inexpensive halogen source, 1,3-dibromo 5,5-dimethylhydantoin, and a simple thiourea catalyst at room temperature. The presence of a tertiary amine enhanced the rate of the dibromination reaction, and yields were good in various solvents, including aqueous solvents. The procedure was extended to alkynes and aromatic rings and to dichlorination reactions by using the 1,3-dichloro hydantoin derivative.
- Hernandez-Torres, Gloria,Tan, Bin,Barbas, Carlos F.
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supporting information; experimental part
p. 1858 - 1861
(2012/06/18)
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- Oxidative functional group transformations with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
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A divanadium-substituted phosphotungstate TBA4[γ-PW 10O38V2(μ-OH)(μ-O)] (I, TBA = tetra-n-butylammonium) reacts with one equivalent H+ to form a bis-μ-hydroxo species [γ-PW10O38V 2(μ-OH)2]3- (I′) in organic media. The strong electrophilic oxidants such as [γ-PW10O 38V2(μ-OH)(μ-OOH)]3- (II) and [γ-PW10O38V2(μ-η2: η2-O2)]3- (III) are formed by the reaction of the bis-μ-hydroxo species with H2O2. In the presence of I and H+, H2O2-based oxidations such as (i) epoxidation of alkenes (17 examples including electron-deficient ones), (ii) hydroxylation of alkanes (11 examples), and (iii) oxidative bromination of alkenes, alkynes, and aromatics with Br- as a bromo source (12 examples including chlorination) chemo-, diastereo-, and regioselectively proceed to give the corresponding oxidized products in moderate to high yields with high efficiencies of H2O2 utilization.
- Mizuno, Noritaka,Kamata, Keigo,Yamaguchi, Kazuya
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scheme or table
p. 157 - 161
(2012/06/18)
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- Using the chemical tunability of ionic liquids to increase sustainability in the electrophilic bromination of unsaturated compounds
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Tribromide-based ionic liquids have been synthesized and investigated as efficient bromination agents. The different physicochemical properties of the reaction media, which depend on the cation structure, have been used to improve the efficiency of the bromination process. Georg Thieme Verlag Stuttgart New York.
- Chiappe, Cinzia,Sanzone, Angelo
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experimental part
p. 2392 - 2396
(2011/09/20)
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- An efficient H2O2-based oxidative bromination of alkenes, alkynes, and aromatics by a divanadium-substituted phosphotungstate
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A divanadium-substituted phosphotungstate TBA4[γ-HPV 2W10O40] (TBA = tetra-n-butylammonium) could act as an effective homogeneous catalyst for the H2O 2-based oxidative bromination.
- Yonehara, Kazuhiro,Kamata, Keigo,Yamaguchi, Kazuya,Mizuno, Noritaka
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supporting information; scheme or table
p. 1692 - 1694
(2011/03/22)
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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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- Organocatalytic diastereoselective dibromination of alkenes
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A highly diastereoselective pyrrolidine-promoted dibromination of alkenes by combination of NBS and succinimide is presented. The pyrrolidine-mediated dibromination of alkenes is higly anti-selective and gives the corresponding products in moderate to high yields and up to >25:1 dr.
- Zhu, Mingzhao,Lin, Shuangzheng,Zhao, Gui-Ling,Sun, Junliang,Córdova, Armando
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experimental part
p. 2708 - 2712
(2010/07/04)
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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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- 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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- The role of neat substrates in phase-vanishing and tandem phase-vanishing reactions
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Phase-vanishing reactions are triphasic reactions, which involve a reagent, a liquid perfluoroalkane as a phase screen and a substrate. Aromatization, isomerization and halogenation of neat substrates under phase-vanishing conditions gave the expected products in good to excellent yields. In tandem single-phase-phase-vanishing reaction, two reactants, placed in the top phase, afforded the intermediate, which in a subsequent phase-vanishing reaction reacted with the reagent from the bottom phase to give the final product. The reaction worked well under solvent-free conditions on liquid substrates and intermediates. With solids, results were better if an additional solvent was employed.
- Windmon, Nicole,Dragojlovic, Veljko
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scheme or table
p. 6543 - 6546
(2009/04/06)
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- 4-hydroxy-2-quinolones 125. Ethyl 3-bromo-2,4-dioxo-1,2,3,4- tetrahydroquinoline-3-carboxylates as potential brominating agents
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The spatial structural features of 3-bromo-3-ethoxycarbonyl-2,4-dioxo-1,2, 3,4-tetrahydroquinolines have been studied by X-ray analysis. It has been experimentally confirmed that these compounds can be regarded as potential brominating agents.
- Ukrainets,Sidorenko,Golovchenko
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p. 1008 - 1013
(2008/09/19)
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- A bimetallic palladium(II) catalyzed synthesis of 1,2-dibromo compounds
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A bimetallic palladium(II) catalyst containing a triketone ligand and a bridging dinitrogen ligand oxidizes aromatic and cyclic aliphatic olefins in bromide-containing aqueous-THF to 1,2-dibromo compounds and bromohydrins. With aromatic olefins, the 1,2-dibromo products were obtained in a 70-80% yield and the bromohydrins in a 10-15% yield; this observation is opposition to that obtained in chloride containing medium where the chlorohydrin product predominates. The oxidation of 2,3-dihydrofuran gave trans-2,3- dibromotetrahydrofuran, 3-oxotetrahydrofuran, and 3-bromo-2- hydroxytetrahydrofuran in relative yields of 75%, 15%, and 10%, respectively. On the other hand, the oxidation of cyclopentene and cyclohexene affords only trans-1,2-dibromo products in about 90% yield. The stereochemistry is consistent with an anti-at-tack of bromide followed by decomposition involving attack of bromide from the coordination sphere of the Pd(II). The procedure outlined here is a convenient method for the one step synthesis of 1,2-dibromides.
- Qaseer
-
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- N-bromosuccinimide and lithium bromide: An efficient combination for the dibromination of carbon-carbon unsaturated bonds
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Compounds possessing unsaturated bonds such as alkenes, alkynes, allenes, and methylenecyclopropanes (MCPs) can be dibrominated within minutes by NBS and lithium bromide in THF at room temperature in good to excellent yields under mild conditions. Georg Thieme Verlag Stuttgart.
- Shao, Li-Xiong,Shi, Min
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p. 1269 - 1271
(2007/10/03)
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- Regioselective synthesis of vic-halo alcohols and symmetrical or unsymmetrical vic-dihalides from epoxides using triphenylphosphine -N-halo imides
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A simple, novel, and highly regioselective cleavage of epoxides into vicinal halo alcohols and symmetrical or unsymmetrical dihalides is described using different stoichiometries of triphenylphosphine (PPh3) and N-halo succinimide (NXS) or N-halo saccharine (NXSac).
- Iranpoor, Nasser,Firouzabadi, Habib,Azadi, Roya,Ebrahimzadeh, Farzaneh
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- Rapid debromination of vic-dibromoalkanes with zinc powder in acetic acid under microwave irradiation
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Microwave irradiation of vic-dibromoalkanes in acetic acid containing zinc powder for 1-2 min gave the corresponding alkenes in high yields.
- Kuang, Chunxiang,Yang, Qing,Senboku, Hisanori,Tokuda, Masao
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p. 282 - 284
(2007/10/03)
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- Chemoselective monobromination of alkanes promoted by unactivated MnO 2
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Reaction of alkanes with bromine promoted by unactivated MnO2 gave the corresponding alkylbromides in excellent yield with good chemoselectivity. The MnO2 could be easily recovered and reused.
- Jiang, Xuefeng,Shen, Meihua,Tang, Yu,Li, Chaozhong
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p. 487 - 489
(2007/10/03)
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- NaIO4-mediated C-H activation of alkylbenzenes and alkanes with LiBr
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NaIO4 oxidizes lithium bromide efficiently under acidic conditions to functionalize alkylbenzenes and alkanes and produce the corresponding bromo and acetoxy derivatives in excellent yields. The protocol also demonstrates the direct conversion of cyclohexane into trans-1,2- dibromocyclohexane in moderate yield.
- Shaikh, Tanveer M.,Sudalai, Arumugam
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p. 5589 - 5592
(2007/10/03)
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- Mild oxidative bromination of alkenes and alkynes with zinc bromide and lead tetraacetate
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Zinc bromide and lead tetraacetate is a practical and safe source of bromine. The combined reagents are used to brominate a variety of alkenes to vicinal dibromoalkanes. Similarly, alkynes can be converted into dibromoalkenes in high yields. The reagents are also capable of tetrabromination of alkynes.
- Muathen, Hussni A.
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p. 3545 - 3552
(2007/10/03)
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- Pentylpyridinium tribromide: A vapor pressure free room temperature ionic liquid analogue of bromine
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The synthesis and characterization of the room temperature ionic liquid pentylpyridinium tribromide (2) is described. Tribromide 2 was used as a vapor pressure free bromine analogue for the bromination of ketones, aromatics, alkenes, and alkynes. The brominations were carried out in the absence of organic solvents and in most cases the only extraction solvent needed was water. Selectivities and reactivities were shown to be superior to current protocols. The spent reagent pentylpyridinium bromide (1) was easily recycled.
- Salazar, José,Dorta, Romano
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p. 1318 - 1320
(2007/10/03)
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- The (Schiff base)vanadium(v) complex catalyzed oxidation of bromide - A new method for the in situ generation of bromine and its application in the synthesis of functionalized cyclic ethers
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(Schiff base)vanadium(v) complexes 5 with tridentate imine auxiliaries served as catalysts for the oxidation of Br with tert-butyl hydroperoxide (TBHP) in nonaqueous solvents. This reaction has been applied for the conversion of substituted 4-penten-1-ols into 5-exo-bromo-cyclized products, including a diastereomerically pure heterocyclic precursor used in a synthesis of the all-trans-configured 2,3,4,5-substituted tetrahydrofuran 2-epi-magnosalicin. Treatment of co-substituted bis(homoallylic) alcohols with the reagent combination of pyHBr, TBHP, and a vanadium(v) catalyst 5 afforded 6-endo-cyclized products, i.e. brominated tetrahydropyrans, as major compounds. The results from 51V NMR, ESI-MS, and supporting reactivity- selectivity studies indicated that the mechanism of the new bromination reaction consists of vanadium-dependent and vanadium-independent steps. A (Schiff base)vanadium(v) compound 5 is required for activation of TBHP via in situ formation of the corresponding tert-butylperoxy complex. This reagent oxidizes Br-, which under the reaction conditions provides Br2 as the active brominating reagent. The molecular bromine generated thus is released into the solution at a steady rate and serves as a reagent for the synthesis of β-brominated cyclic ethers from bis(homoallylic) alcohols in a second, vanadium-independent step. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Greb, Marco,Hartung, Jens,Koehler, Franz,Spehar, Kristina,Kluge, Ralph,Csuk, Rene
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p. 3799 - 3812
(2007/10/03)
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- Bromination of carbon-carbon double bonds involving oxidation of NaBr in an ionic liquid
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Bromination of alkenes has been conducted in a room temperature ionic liquid {[bmim]+ CCl3COO- (1-butyl-3- methylimidazolium trichloroacetate)} involving the oxidation of NaBr by hydrogen peroxide with no catalyst. Comparatively fast reactions, good yields and the atom economic nature make this environmentally benign reaction an appealing procedure for alkene and alkyne bromination.
- Ying, Taokei,Bao, Weiliang,Zhang, Yoegmin
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p. 806 - 807
(2007/10/03)
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- Selective conversion of epoxides to vic-halo alcohols and symmetrical or unsymmetrical dihalides by triphenylphosphine/2,3-dichloro-5,6-dicyano-1,4- benzoquinone (DDQ) in the presence of quaternary ammonium halides
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A new method is described for the efficient and selective conversion of epoxides to vic-halo alcohols or symmetrical and unsymmetrical dihalides using PPh3/DDQ/R4NX (X = Cl, Br, I) as a mixed-reagent system.
- Iranpoor, Nasser,Firouzabadi, Habib,Aghapour, Ghasem,Nahid, Azarmidokht
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p. 1885 - 1891
(2007/10/03)
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- Dendrimeric organochalcogen catalysts for the activation of hydrogen peroxide: Origins of the "dendrimer effect" with catalysts terminating in phenylseleno groups
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Several scenarios were evaluated to explain the large "dendrimer effect" observed in the bromination of cyclohexene with H2O 2 and NaBr catalyzed by the addition of Frechet-type dendrimers terminating in -O(CH2)3SePh groups. Although phenylseleninic acid was an efficient catalyst for the oxidation of NaBr with H2O2, first-order rate constants for the selenoxide elimination were too small to produce PhSeO2H at a rate sufficient to explain the rates of catalysis and no dendrimer effect was observed in the rates of selenoxide elimination. An induction period was observed using 1-SePh as a catalyst for the oxidation of Br- with H2O2. The addition of preformed selenoxide 1-Se(=O)Ph gave immediate catalysis with no induction period. However, rates of oxidation of the selenides with H 2O2 under homogeneous or biphasic conditions or with t-BuOOH under homogeneous conditions were too slow to account for the rates of catalysis, and no dendrimer effect was observed in the rates of oxidation. The primary oxidant for converting selenides to selenoxides was "Br+" produced initially by the uncatalyzed background reaction of H2O 2 with NaBr and then produced catalytically following formation of selenoxide groups. Autocatalysis is observed, and the rate of oxidation increases with the number of SePh groups. Autocatalysis is the source of the large dendrimer effect observed with the SePh series of catalysts.
- Drake, Michael D.,Bright, Frank V.,Detty, Michael R.
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p. 12558 - 12566
(2007/10/03)
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- Phase-vanishing reactions that use fluorous media as a phase screen. Facile, controlled bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide
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In fluorous triphasic reactions, such as bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide, the middle fluorous phase acts as a liquid membrane permitting passive transport of the reagents at the bottom to the top layer involving the substrates, thereby regulating the reactions. Copyright
- Ryu, Ilhyong,Matsubara, Hiroshi,Yasuda, Shinji,Nakamura, Hiroyuki,Curran, Dennis P.
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p. 12946 - 12947
(2007/10/03)
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- A simple method for the precise and simultaneous determination of primary and multiple secondary kinetic deuterium isotope effects in organic reactions at natural abundance
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A method for the determination of kinetic isotope effects (KIEs) in organic reactions using natural abundance deuterium NMR is proposed. The method consists of the determination of the site-specific H/D isotopic ratios of the starting reactant and the product in a reaction run under pseudo-first-order kinetic conditions. Using simple and easy experimental procedures, primary and/or multiple secondary KIEs can be measured simultaneously with high precision. The application of this approach to different types of reaction is described. The primary and α-secondary KIEs for C-H(D) bond breaking of -CDH- can be measured separately. The uncertainty in the determination of small secondary KIEs can reach less than 1%. The results show that some remote secondary KIEs are not negligible. The advantages and limitations of the method are discussed. One of its merits is that the method can even be used in complex situations when there are branch reactions and when the reaction is reversible. The performance depends essentially on the signal separation in the NMR spectra. Copyright
- Zhang, Ben-Li,Pionnier, Sebastien
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p. 239 - 246
(2007/10/03)
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- Dendrimeric organochalcogen catalysts for the activation of hydrogen peroxide: Improved catalytic activity through statistical effects and cooperativity in successive generations
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Dendrimeric polyphenylsulfides, -selenides, and -tellurides are prepared in high yield using propyloxy spacers to connect the phenylchalcogeno groups to the dendrimeric core. The selenides and tellurides catalyze the oxidation of bromide with hydrogen peroxide to give positive bromine species that can be captured by cyclohexene in two-phase systems. The corresponding sulfides show no catalytic activity. The increase in the rate of catalysis followed statistical effects for 1, 6, and 12 phenyltelluro groups. However, the increase in the rate of catalysis exceeds statistical contributions for the first few generations with 1, 3, 6, and 12 phenylseleno groups and suggested cooperativity among phenylseleno groups. The increase in catalytic rate was lost upon replacing all but one phenylseleno group with phenoxy groups. On the basis of H2O2 consumed, the dendrimer with 12 phenylseleno groups has a turnover number of >60 000 mol of H2O2 consumed per mole of catalyst.
- Francavilla,Drake,Bright,Detty
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- Preparative procedure of dihalosulfenylation: Thiobisamines addition to unsaturated compounds in the presence of phosphorus oxyhalides and halides
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A new synthetic method was developed for β,β′-dihaloalkyl sulfides (halogen chlorine or bromine) by reaction of thiobisamines with olefins and alkynes in the presence of the appropriate phosphorus halides. The reaction proceeds along electrophilic mechanism affording trans-addition products. The highest yields of the target products were obtained at POBr3 or POCl3 application.
- Zyk,Beloglazkina,Vatsadze,Titanyuk,Dubinskaya
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p. 794 - 800
(2007/10/03)
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- Reactions of nucleophiles with 5-(alkoxy)thianthrenium ions
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Reactions of 5-(alkoxy)thianthrenium perchlorates (1) with weakly basic nucleophiles Br-, I- and PhS- (X-) in MeCN and DMSO led to SN2 substitution, E2C elimination, and reaction at sulfornium sulfur to extents depending on the structure of the alkoxy group (RO) in 1 and the nucleophile. Three types of reaction occurred with R = cyclopentyl (1a), cyclohexyl (1b), cis- (1c) and trans- 4-methylcyclohexyl (1d) and cycloheptyl (1e), and X- = Br and I-. That is, SN2 reaction gave RX and thianithrene 5-oxide (ThO), E2C reaction gave cycloalkene and ThO and reaction at sulfonium sulfur gave X2, thianthrene (Th) and cycloalkanol (ROH). Earlier work with R = Me (1f) and Et (1g) and X- = I-. Br- had shown that only SN2 reaction occurred. In contrast with reactions of halide ions, reactions of PhS- with 1b-g occurred only at sulfonium sulfur, giving Th, ROH and PhSSPh (DPDS). For comparison with 1, reactions of Ph2S+OMe (2) with I- and PhS- were carried out. Reaction with I- gave only Ph2S=O and Mel (SN2), Reaction with PhS- gave very little PhSMe (SN2) but mainly Ph2S, MeOH, and DPDS from reaction at sulfonium sulfur. The differences in nucleophilic pathways (PhS- vs Br- and I-) in reactions with 1 and 2 are attributed to differences in thiophilicities of the nucleophiles. The thiophilicity of PhS- dominates its reactions with 1 and 2. The direction toward products (Th, ROH and DPDS) in these reactions is compounded by the ease of displacement of alkoxide from 1 and 2 by PhS-, and the ease with which, subsequently, thiophilic PhS- attacks sulfenyl sulfur in the resulting phenylthiosulfonium ion. Copyright
- Liu, Bo,Shine, Henry J.,Zhao, Wenyi
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p. 827 - 836
(2007/10/03)
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