- Complexes of cis-dioxomolybdenum(VI) with a chiral tetradentate tripodal-like ligand system: Syntheses, structures and catalytic activities
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Racemic complexes with the general formula cis-[MoO2(bzacLn)] (1–4) (H2bzacLn?=?2-((4/5-R-2-hydroxyphenylamino)(pyridin-2-yl)methyl)-1-phenylbutane-1,3-dione, where n?=?1–4 for R?=?H, 5-Me, 5-Cl and 4-Me, respectively and 2Hs represent the dissociable phenolic proton and the active tertiary CH proton) have been synthesized in 75–82% yields by reacting [MoO2(bzac)2] (Hbzac?=?benzoylacetone) with the potentially N2O-donor 5,5-membered fused chelate rings forming Schiff bases 4/5-R-2-(2-pyridylaldimine)phenols (HLn; n?=?1–4 for R?=?H, 4-Me, 4-Cl and 5-Me, respectively) in hot methanol. The chiral ligand system (bzacLn)2?in 1–4 is formed via metal assisted Mannich-type addition of benzoylacetonate methine to the azomethine fragment of HLn. All four complexes have been characterized by elemental (CHN) analysis, solution conductivity, magnetic susceptibility, spectroscopic (IR, UV–Vis and NMR) and electrochemical measurements. The molecular structures of 1–3 have been established by single crystal X-ray crystallography. In each complex, the chiral (bzacLn)2?acts as a tetradentate, N2O2-donor, tripodal-like ligand system and along with the two mutually cis oxo groups forms a distorted octahedral N2O4coordination environment around the molybdenum(VI) center. All four complexes are diamagnetic and non-electrolytic. The infrared spectra are generally consistent with the structural formulas of 1–4. The electronic spectra of 1–4 in dimethylformamide display two strong absorption bands in the range 245–300?nm. The cyclic voltammograms of 1–4 in dimethylformamide exhibit a metal centered one-electron reduction response within ?0.64 to ?0.74?V. All these complexes (1–4) and the analogous cis-[MoO2(acacL1–4)] (5–8) synthesized from [MoO2(acac)2] (Hacac?=?acetylacetone) and HL1–4have been evaluated for their bromoperoxidase activities.
- Ghosh, Sabari,Kurapati, Sathish Kumar,Pal, Samudranil
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Read Online
- Pseudophase Model for Reactivity in Reverse Micelles. The Case of the Water-Promoted Reaction between Two Lipophilic Reagents, Bromine and 1-Octene, in AOT Microemulsions
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Kinetic investigations of 1-octene bromination in AOT-isooctane-water microemulsions (13 / / tr, transfer coeffcients from isooctane to water, are 1.5E-5 and 8.8E-3 for alkene and bromine, respectively), bromination occurs in an aqueous microenvironment, as ilustrated by the high sensitivity of the bromination rate to the water content of the microemulsion.A kinetic pseudophase model describes the rate constant dependence on microemulsion composition satisfactorily by assuming competition between reactions at the interface and in the aqueous phase.Reasonable values for the coefficients of reagent partition between the interface and the two microphases and for the local bromination rate constants are obtained from the kinetic equations derived from the model.In particular, spectroscopically observed AOT-bromine complexation is in agreement with the high bromine concentration at the interface (K2, bromine partition coefficient from isooctane to interface, = 6.8).The water-phase bromination rate constant, kw = 1E8 M-1 s-1, is in the sanme range as that measured in bulk water.The lower limit for the interfacial rate constant, ki, is 1E3 M-1 s-1, a value close to that observed in poorly aqueous methanol (MeOH/H2O = 95/5 v/v).These data are compared with those recently obtained in the same microemulsions for solvolysis, a reaction which, like bromination, is water-promoted but supposed to take place at the interface only.The results are discussed in terms of the chemical properties of the water molecules encased in the microemulsion droplets.
- Blagoeva, Iva B.,Gray, Peter,Ruasse, Marie-Francoise
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Read Online
- Bromination of alkenes using a mixture of sodium bromide and sodium perborate
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Bromination of alkenes with sodium bromide in the presence sodium perborate provides a simple, high yield route to dibromoalkanes.
- Kabalka,Yang,Reddy,Narayana
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Read Online
- 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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- Crystal structure, characterization, Hirshfeld surface analysis and DFT studies of two [propane 3-bromo-1-(triphenyl phosphonium)] cations containing bromide (I) and tribromide (II) anions: The anion (II) as a new brominating agent for unsaturated compounds
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In this study, propane 3-bromo-1- (triphenyl phosphonium) bromide, I, and propane 3-bromo-1- (triphenyl phosphonium) tribromide, II, (II as a new brominating agent) were synthesized and characterized by 1H NMR, 13C NMR, 31P NMR, FT-IR, spectroscopy, Thermogravimetric Analysis, Differential thermal analysis, Differential scanning calorimetry and single crystal X-ray analysis. Density functional theory calculations (energy, structural optimization and frequencies, Natural Bond Orbital, absorption energy and binding energy) were performed by using B3LYP/6-311 G++ (d, p) level of theory. Hirshfeld surface analysis and fingerprint plots were utilized to investigate the role of bromide and tribromide anions on the crystal packing structures of title compounds. The results revealed that the change of accompanying anionic moiety can affect the directional interactions of C-H?Br hydrogen bonds between anionic and cationic units in which the H?Br with a proportion of 53.8% and 40.9% have the major contribution in the stabilization of crystal structures of I and II, respectively. Furthermore, the thermal stability of new brominating agent II with tribromide anion was compared with compound I with bromide anion. Nontoxicity, short reaction time, thermal stability, simple working up and high yield are some of the advantages of these salts.
- Nokhbeh, Seyed Reza,Gholizadeh, Mostafa,Salimi, Alireza,Sparkes, Hazel A.
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p. 542 - 554
(2019/06/18)
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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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- One-Pot Strategy for Thiazoline Synthesis from Alkenes and Thioamides
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A convenient synthesis of a privileged pharmaceutical motif, thiazoline is accomplished. This reaction utilizes simple and readily available alkene and thioamide substrates in an intermolecular fashion via a simple one-pot procedure. A wide range of functional groups is tolerated, and the thiazoline product has been further utilized for the synthesis of the corresponding β-aminothiol and thiazole from routine hydrolysis and oxidation protocols.
- Alom, Nur-E,Wu, Fan,Li, Wei
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supporting information
p. 930 - 933
(2017/02/26)
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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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- Trihaloisocyanuric Acid/Triphenylphosphine: An Efficient System for Regioselective Conversion of Epoxides into Vicinal Halohydrins and Vicinal Dihalides under Mild Conditions
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A new synthetic method has been developed for the regioselective conversion of epoxides to vicinal chloro-/bromohydrins and vicinal dihalides by reaction with the system trihaloisocyanuric acid/tri?phenylphosphine in acetonitrile under mild and neutral conditions. The reactions proceed smoothly in high yield at room temperature and at reflux, respectively, over a short time.
- De Andrade, Vitor S. C.,De Mattos, Marcio C. S.
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p. 1381 - 1388
(2016/05/19)
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- Cis-Dioxomolybdenum(VI) complexes with unsymmetric linear tetradentate ligands: Syntheses, structures and bromoperoxidase activities
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Reactions of [MoO2(acetylacetonate)2], 2-((2-(2-hydroxyethylamino)ethylamino)methyl)-4-R-phenols (H2Ln, n = 1-5 for R = H, Me, OMe, Cl and Br, respectively) and KOH in 1:1:2 mole ratio in methanol afford a series of complexes having the general formula cis-[MoO2(Ln)] (1, 2, 3, 4, 5) in 81-86% yields. The complexes have been characterized using elemental analysis, spectroscopy (infrared, UV-visible, and 1H NMR, 13C NMR and 13C-DEPT NMR) and electrochemical measurements. The molecular structures of 1, 2, 3, 4 have been determined using single-crystal X-ray crystallography. In each of 1, 2, 3, 4, the ONNO-donor 6,5,5-membered fused chelate rings forming (Ln)2- and the two mutually cis oxo groups assemble a distorted octahedral N2O4 coordination sphere around the metal centre. In the crystal lattice, each of 1, 2, 3, 4 forms a one-dimensional infinite chain structure via intermolecular N-H...O hydrogen bonding interactions. In cyclic voltammograms, the diamagnetic complexes display an irreversible metal-centred reduction in the potential range -0.73 to -0.88 V (vs Ag/AgCl). The physicochemical data are consistent with a very similar gross molecular structure for all of 1, 2, 3, 4, 5. All the complexes exhibit decent bromoperoxidase activities and are also able to effectively catalyse benzoin and methyl(phenyl)sulfide oxidation reactions.
- Kurapati, Sathish Kumar,Pal, Samudranil
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p. 116 - 124
(2016/02/18)
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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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- Synthesis and oxidation catalysis of a Ti-substituted phosphotungstate, and identification of the active oxygen species
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In this paper, we report the synthesis of a Ti-substituted phosphotungstate, TBA6[(γ-PW10O36)2Ti4(μ-O)2(μ-OH)4] (I, TBA = tetra-n-butylammonium), and its application to H2O2-based oxidation. Firstly, an organic solvent-soluble dilacunary phosphotungstate precursor, TBA3[γ-PW10O34(H2O)2] (PW10), has been synthesized. By the reaction of PW10 and TiO(acac)2 (acac = acetylacetonate) in an organic medium (acetonitrile), I can be obtained. Compound I possesses a tetranuclear Ti core which can effectively activate H2O2 and shows high catalytic performance for several oxidation reactions, such as epoxidation of alkenes, oxygenation of sulfides, oxidative bromination of unsaturated compounds, and hydroxylation of anisole, giving the corresponding oxidation products with high efficiencies and selectivities. The catalytic performance of I is much superior to those of previously reported Ti-substituted polyoxometalates. In addition, I is highly durable during catalysis and can be reused several times while keeping its high catalytic performance. Furthermore, we have successfully isolated the truly catalytically active species for the present I-catalyzed oxidation, TBA6[(γ-PW10O36)2Ti4(μ-η2:η2-O2)4] (II), and its anion structure has been determined by X-ray crystallographic analysis. All of the four Ti2-μ-η2:η2-peroxo species in II are active for stoichiometric oxidation (without H2O2), and II is included in the catalytic cycle for I-catalyzed oxidation.
- Takahashi, Eri,Kamata, Keigo,Kikukawa, Yuji,Sato, Sota,Suzuki, Kosuke,Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 4778 - 4789
(2015/10/05)
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- Halocarbocyclization versus dihalogenation: Substituent directed iodine(iii) catalyzed halogenations
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The nucleophilicity of the substituents in iodobenzene pre-catalysts have a huge impact on product selectivity in iodine(iii) triggered halogenations, steering the reactivity from solely carbocyclizations towards dihalogenations. Utilizing this catalyst-dependent reactivity a diastereo- and chemoselective dihalogenation method was established allowing the conversion of structurally and electronically diverse unsaturated compounds in excellent yields.
- Stodulski, Maciej,Goetzinger, Alissa,Kohlhepp, Stefanie V.,Gulder, Tanja
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supporting information
p. 3435 - 3438
(2014/03/21)
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- Oxidative bromination of alkenes mediated with nitrite in ionic liquids
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The oxidative bromination of C2-C8 alkenes with HBr-NaNO2-O2 in solutions of BMImBr, HMImBr or BMImBF 4 containing 16-28 wt% H2O was studied using volumetric method, GC-MS analysis, 14N NMR and UV-VIS spectroscopy. The optimal conditions to conduct the reaction at high selectivity for 1,2-dibromoalkanes in BMImBr were determined. The composition of ionic liquid affects the catalytic performance. Although in BMImBF4 the reaction runs with equal rate as in bromide ionic liquid, the fraction of bromohydrin in the reaction products increases to 20 %. Generated from NaNO2, NOx operated as a catalyst in the oxidation of Br- and was oxidized to catalytically inert NO3 - anions when complete conversion of HBr was attained. Graphical Abstract: Oxidative bromination of alkenes [Figure not available: see fulltext.]
- Kuznetsova, Lidia I.,Kuznetsova, Nina I.,Zudin, Vladimir N.,Utkin, Viktor A.,Trebushat, Dmitry V.,Fedotov, Martin A.,Larina, Tatyana V.
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p. 1499 - 1506,8
(2014/11/08)
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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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- 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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- 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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- Synthesis of phenacyl bromides via K2S2O 8-mediated tandem hydroxybromination and oxidation of styrenes in water
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Non-transition metal-catalyzed synthesis of phenacyl bromides was achieved through K2S2O8-mediated tandem hydroxybromination and oxidation of styrenes. The advantages of this reaction are its excellent functional group compatibility, mild reaction conditions (60 °C) and use of pure water as reaction medium. Based upon experimental observations, a plausible reaction mechanism is proposed.
- Jiang, Qing,Sheng, Wenbing,Guo, Cancheng
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p. 2175 - 2179
(2013/09/24)
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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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- Synthesis of acetylenes via dehydrobromination using solid anhydrous potassium phosphate as the base under phase-transfer conditions
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Phase-transfer catalyzed preparation of acetylenes from the corresponding vicinal dibromo compounds via double dehydrobromination using the mild solid base, anhydrous potassium phosphate, under very mild conditions is reported.
- Shenawi-Khalil, Sanaa,Sonavane, Sachin U.,Sasson, Yoel
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experimental part
p. 2295 - 2297
(2012/07/27)
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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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- Aerobic oxidative carboxylation of olefins with metalloporphyrin catalysts
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Dioxo(tetraphenylporphyrinato)ruthenium(vi) and quaternary onium salt were successfully developed as catalysts to initiate a three component reaction of olefin, O2, and CO2 at ambient temperature under low pressure. The reaction can be carried out under solvent-free or solvent conditions. Styrene carbonate was obtained in 76% yield with 100% selectivity using 4 mol% of catalyst under optimized conditions.
- Bai, Dongsheng,Jing, Huanwang
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supporting information; scheme or table
p. 39 - 41
(2010/05/17)
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- Comparative study of the vicinal functionalization of olefins with 2:1 bromide/bromate and iodide/iodate reagents
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A comparative evaluation was made on the syntheses of vicinal halohydrins, halo methyl ethers, and halo acetates from olefins using 2:1 Br-/BrO3- and I-/IO3- reagents. In many cases both reagents afforded products selectively in high yields. The highest halogen atom efficiencies attained were 97% and 93% for Br-/BrO3- and I-/IO3-, respectively. Of the two reagents, I-/IO3- was established to be the preferred reagent for vicinal functionalization of linear alkenes and also for halo acetate preparation. However, only Br-/BrO3- was effective for vicinal functionalization of trans-stilbene and chalcones.
- Agrawal, Manoj K.,Adimurthy, Subbarayappa,Ganguly, Bishwajit,Ghosh, Pushpito K.
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experimental part
p. 2791 - 2797
(2009/08/08)
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- Tetraalkylphosphonium trihalides. Room temperature ionic liquids as halogenation reagents
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(Chemical Equation Presented) Six room temperature ionic liquids (RTILs) comprised of a tetraalkylphosphonium cation (tridecylmethyphosphonium or trihexyltetradecylphosphonium) and a trihalide anion (Br3 -, BrCl2-, or ClBr2-) have been prepared and characterized. Their ability to effect halogenation reactions with a variety of substrates has been explored. In general, halogenation reactions of alkenes proceed with high yields and stereo- and regioselectivities, whether performed in the absence or presence of a solvent (chloroform). Reactions of an alkyne and electrophilic substitution on an aromatic ring have been investigated as well. The facile preparation of the salts, their ease of handling, and the simplicity of product isolation should make these RTILs useful additions to the repertoire of halogenation reagents and the reagents of choice for specific transformations.
- Cristiano, Rodrigo,Ma, Kefeng,Pottanat, George,Weiss, Richard G.
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supporting information; scheme or table
p. 9027 - 9033
(2010/03/30)
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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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- Efficient bromination of alkenes and alkynes using potassium bromide and diacetoxy iodobenzene
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Bromination of alkenes and alkynes has efficiently been carried out at room temperature in short reaction times using KBr and diacetoxy iodobenzene in CH2Cl2-H2O (1:1) to prepare the corresponding trans-dibromo compounds in excellent yields. Copyright Taylor & Francis Group, LLC.
- Das, Biswanath,Srinivas, Yallamalla,Sudhakar, Chittaluri,Damodar, Kongara,Narender, Ravirala
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experimental part
p. 220 - 227
(2009/04/07)
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- Selective aerobic oxidative dibromination of alkenes with aqueous HBr and sodium nitrite as a catalyst
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Various alkenes (internal, terminal, aryl and alkyl substituted) and 1,2-diphenylethyne were efficiently and selectively dibrominated using 2 equivalents of 48% aqueous hydrobromic acid, with air as an oxidant and sodium nitrite as a catalyst. Despite the presence of water, only trans dibromination occurred producing anti-1,2-dibromoalkanes and (E)-1,2-dibromo-1,2- diphenylethene. A comparison of resource demand, waste production and environmental, health and safety issues of the NaNO2 catalyzed aerobic bromination with molecular bromine and other oxidative bromination methods revealed that the proposed method is not only selective and effective but has a better environmental profile.
- Podgorsek, Ajda,Eissen, Marco,Fleckenstein, Jens,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
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experimental part
p. 120 - 126
(2010/04/22)
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- Facile one-pot synthesis of α-bromoketones from olefins using bromide/bromate couple as a nonhazardous brominating agent
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A new method for the preparation of α-bromoketones from olefins using bromide/bromate couple as a nonhazardous brominating agent has been developed. Several α-bromoketones were successfully prepared from a variety of olefins by this method. This procedure is an alternative to conventional molecular bromine.
- Patil, Rajendra D.,Joshi, Girdhar,Adimurthy, Subbarayappa,Ranu, Brindaban C.
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experimental part
p. 2529 - 2532
(2009/09/06)
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- Bromination of alkenes and alkynes with (bromodimethyl)sulfonium bromide
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Alkenes and alkynes were brominated efficiently in high yields with (bromodimethyl)sulfonium bromide in acetonitrile at room temperature. Alkenes produced the corresponding trans-dibromo compounds while alkynes (except phenylacetylene) afforded both the trans-dibromo products (major) and the tetrabromo derivatives (minor). However, phenylacetylene furnished solely the tetrabromo compound.
- Das, Biswanath,Srinivas, Yallamalla,Sudhakar, Chittaluri,Ravikanth, Bommena
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experimental part
p. 188 - 190
(2009/07/18)
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- Poly(vinylpyrrolidone)-bromine complex; a mild and efficient reagent for selective bromination of alkenes and oxidation of alcohols
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Poly(vinylpyrrolidone)-bromine complex (PVP-Br2) is easily prepared and used as a mild and convenient reagent for selective bromination of alkenes and at the position α-hydrogen of active carbonyl compounds. Selective oxidation of benzylic alcohols in the presence of aliphatic alcohols were also achieved at room temperature.
- Lakouraj, Moslem Mansour,Tajbakhsh, Mahmood,Mokhtary, Masoud
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p. 481 - 483
(2007/10/03)
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- PS-COD and PS-9-BBN: Polymer-supported reagents for solution-phase parallel synthesis
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(Chemical Equation Presented) 1,5-Cyclooctadiene was deprotonated under LICKOR conditions and reacted with Merrifield resin to afford an immobilized cyclooctadiene in high yield. This polymer is effective as a halogen scavenger, while hydroboration leads to a supported 9-BBN analogue. The latter exhibits similar regioselectivity to 9-BBN in olefin hydroboration.
- Revell, Jefferson D.,Doerner, Barbara,White, Peter D.,Ganesan
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p. 831 - 833
(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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- NaIO4-Mediated Selective Oxidative Halogenation of Alkenes and Aromatics Using Alkali Metal Halides
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(Equation presented) NaIO4 oxidizes alkali metal halides efficiently in aqueous medium to halogenate alkenes and aromatics and produce the corresponding halo derivatives in excellent regio and stereoselectivity. The system also demonstrates the asymmetric version of bromo hydroxylation using β-cyclodextrin complexes, resulting in moderate ee.
- Dewkar, Gajanan K.,Narina, Srinivasarao V.,Sudalai, Arumugam
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p. 4501 - 4504
(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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- Novel High Energy Intermediate Analogues with Triazasterol-Related Structures as Inhibitors of Ergosterol Biosynthesis. Part I: Synthesis and Antifungal Activity of N-alkyl-N'-(phenethyl- and cyclohexenylethyl)guanidines and N2-Substituted 2-Imidazolinamines
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A series of N-alkyl-N'-(phenethyl- and cyclohexenylethyl)guanidines and N2- and N2,4-substituted imidazolin-2-amine hydrochlorides with triazasterol-related structures was designed and synthesized as stable analogues to mimic high energy intermediates of ergosterol biosynthesis. The in vivo antifungal susceptibility tests with a standard panel of pathogenic fungi revealed moderate to strong antimycotic effects of the sixteen prepared compounds, in some cases comparable with the activity observed for itraconazole.
- Goessnitzer, Edith,Malli, Roland,Schuster, Silvia,Favre, Bertrand,Ryder, Neil S.
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p. 535 - 546
(2007/10/03)
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- An efficient bromination of alkenes using cerium(IV) ammonium nitrate (CAN) and potassium bromide
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Bromination of alkenes using a combination of potassium bromide and cerium(iv) ammonium nitrate (CAN) in a two phase system consisting of water and dichloromethane affords the corresponding dibromides in excellent yield. The reaction most likely involves the addition of the bromine radical generated from bromide ion by CAN and subsequent formation of the dibromide.
- Nair, Vijay,Panicker, Sreeletha B,Augustine, Anu,George, Tesmol G,Thomas, Siji,Vairamani
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p. 7417 - 7422
(2007/10/03)
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- Conversion of alkyl halides into the corresponding alcohols under mild reaction conditions
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Reaction of primary, cyclopentyl, allyl and arylmethyl halides, but not an acyclic secondary halide or a tertiary halide, in acetone or tetrahydrofuran with the formate form of a commercial anion exchange resin gave formate esters in good yields. The formates were hydrolysed efficiently to the corresponding alcohols by a brief treatment with hydrochloric acid. Reaction of primary alkyl bromides or iodides, secondary alkyl bromides, cinnamyl and arylmethyl halides in tetrahydropyran or 1,4-dioxane with the bicarbonate form of the same anion-exchange resin gave the corresponding alcohols directly in good yields. This latter reaction can be carried out successfully in the presence of ester or amide groups.
- Ruddick, Clare L.,Hodge, Philip,Houghton, Mark P.
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p. 1359 - 1362
(2007/10/03)
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- Mimicking the vanadium bromoperoxidases reactions: Mild and selective bromination of arenes and alkenes in a two-phase system
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Vanadium bromoperoxidases catalyze the oxidation of bromide ion by hydrogen peroxide to a bromine-equivalent intermediate. This, in turn, brominates organic molecules. The hypothesis is made that the former reaction takes place in the hydrophilic portion of the enzyme whereas the latter proceeds in a hydrophobic one in which the brominating intermediate is rapidly transferred. We have reproduced such situation by employing a two-phase (H2O/CHCl3) system. In the aqueous acid phase H2O2 and catalytic amounts of NH4VO3 are present, together with KBr. The substrates, i.e. aromatic hydrocarbons and alkenes are dissolved in CHCl3. The bromination proceeds smoothly with stirring, at 25°C, providing high yields of the corresponding brominated products.
- Conte,Di Furia,Moro
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p. 7429 - 7432
(2007/10/02)
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- Solvation and Steric Effects on Electrophilic Reactivity of Ethylenic Compounds. Part 4. Bromination of Oct-1-ene in Anionic Microemulsions
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The kinetics and product distribution of the bromination of oct-1-ene in anionic sodium dodecylsulfate (SDS)-butanol-hexane-water and sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-isooctane-water microemulsions are reported.Dibromide and solvent-incorporated products are formed.In both kinds of microemulsion, the dibromide yield decreases smoothly from 100percent to 10percent as the water content of the reaction medium increases from 0percent to 65percent, whereas in pure water or butanol it is greater than 80percent.The regioselectivity of the water- or butanol-incorporated products is 70:30 Markownikoff: anti-Markovnikoff, a ratio identical with that found in pure methanol, butanol or water.Kinetic bromide-ion effects on the reaction in a water-rich (75percent) SDS microemulsion, show that bromination occurs in the interfacial oil-water region, and not in one of the two microphases, the only brominating agent being molecular bromine and not the tribromide ion.The overall bromination rate constant in this SDS microemulsion (k = 1.6 * 104 dm3 mol-1 s-1) is smaller than that in pure water (2.3 * 107 dm3 mol-1 s-1) and in SDS micelles (2 * 105 dm3 mol-1 s-1), in the same range as that in a 80-20 methanol-water mixture, and greater than that in butanol (2 * 102 dm3 mol-1 s-1).These results are discussed in terms of the particular characteristics (ionization and dissociating abilities, aquation and water properties) of the microemulsion interfaces.
- Ruasse, Marie-Francoise,Blagoeva, Iva B.,Krys, Sophie,Sebastian-Gambaro, Maria-Angela
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p. 1283 - 1289
(2007/10/02)
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- Micellar Effects upon Alkene Bromination. 2. The Role of Alkene Hydrophobicity
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Surface polarity of cettyltrimethylammonium bromide (CTAB) aqueous micelles was checked by use of as a probe the bromination reaction of a series of 1-alkenes and a water-soluble alkene, cis-4-cyclohexene-1,2-dicarboxylic acid dimethyl ester (I).There was
- Cerichelli, Giorgio,Grande, Celeste,Luchetti, Luciana,Mancini, Giovanna
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p. 3025 - 3030
(2007/10/02)
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- TETRABUTYLAMMONIUM DIHYDROGENTRIFLUORIDE: AN EFFECTIVE SOURCE OF FLUORIDE ION FOR HALOFLUORINATION OF ALKENES
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Vicinal halofluorides have been prepared from the corresponding alkenes by reaction with a stoichiometric amount of Bu4N+H2F3- as a source of fluoride anion and an excess of an N-halosuccinimide (NXS).The reaction products are obtained in good yields, with a prevalent Markownikoff regiochemistry.Olefins containing hydroxy, epoxy, acetoxy and alkoxy groups do not undergo side reactions under these reaction conditions.
- Albanese, Domenico,Landini, Dario,Penso, Michele,Pratelli, Marco
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p. 537 - 541
(2007/10/02)
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- A Mild and Efficient Sonochemical Bromination of Alkenes Using Tetrabutylammonium Tribromide
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The bromination of substituted alkenes using tetrabutylammonium tribromide can be effectued under mild conditions with ultrasonic irradiation.This process gives quantitatively the corresponding vicinal dibromide in high yield. Key words: bromination, tribromide, sonication, alkenes, vicinal dibromoalkanes
- Berthelot, Jacques,Benammar, Yamina,Lange, Catherine
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p. 4135 - 4136
(2007/10/02)
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- Outer-sphere and inner-sphere processes in reductive elimination. Direct and indirect electrochemical reduction of vicinal dibromoalkanes
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The reduction of vicinal dibromoalkanes is investigated as an example of the dichotomy between outer-sphere and inner-sphere processes in reductive elimination. As a result from the analysis of the kinetic data, outer- sphere reagents such as carbon electrodes and aromatic anion radicals react with vicinal dibromoalkanes according to an "ET" mechanism in which the rate-determining step is a concerted electron- transfer bond-breaking reaction leading to the β-bromoalkyl radical. The latter is then reduced very rapidly, in a second step, most probably along another concerted electro- transfer bond-breaking pathway leading directly to the olefin in the heterogeneous case and through halogen atom expulsion in the homogeneous case. In the absence of steric constraints, the reduction goes entirely through the antiperiplanar conformer because the resulting β-bromoalkyl radical is then stabilized by delocalization of the unpaired electron over the C-C-X framework due to a favorable interaction between the pz orbital of the radical carbon and the σ* orbital of the C-Br bond. This interaction is enhanced by alkyl substitution at the reacting carbons, resulting in an approximately linear correlation between the reduction potential and the C-X bond energy of OlX2 on one hand and the vertical ionization potential of the olefin on the other. The stabilization energy is of the order of 0.2-0.3 eV for the anti conformers. It can also be taken as a measure of the rotation barrier around the C-C bond responsible for the loss of stereospecificity in the reduction. This competes with the reduction of the two stable conformers of the OlX* radicals and for the expulsion of the halogen atom. There is a remarkably good agreement between the ensuing prediction of the E:Z olefin ratio that should be found upon reduction of threo and erythro OlX2 isomers by outer-sphere reagents such as aromatic anion radicals and the experimental data. Although members of perfectly reversible redox couples, iron(I), iron("0"), and cobalt(I) porphyrins offer typical examples of inner-sphere reagents in their reaction with vicinal dibromoalkanes. They indeed react much more rapidly than outer-sphere electron donors (aromatic anion radicals) of the same standard potential. On the basis of steric hindrance experiments, it was shown that they do not react according to an SN2 rate-determining step involving the transient formation of an organometallic species. Complete stereospecificity is obtained, showing that they react along a halonium transfer E2 elimination mechanism rather than by an E1 elimination or a halogen atom transfer mechanism. As shown on a quantitative basis, this is related to the large driving force offered to halonium abstraction by the strong affinity of the iron(III) and cobalt (III) complexes toward halide ions. In regards to catalysis, the investigated systems provide typical examples showing the superiority of inner-sphere (chemical) catalysis over outer-sphere (redox) catalysis of electrochemical reactions. Not only is the catalytic efficiency much better since the rate constants of the key steps are larger, given the standard potential of the catalyst, but also selectivity is dramatically improved.
- Lexa, Doris,Savéant, Jean-Michel,Sch?fer, Hans J.,Su, Khac-Binh,Vering, Birgit,Wang, Dan Li
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p. 6162 - 6177
(2007/10/02)
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- Fatty Tetrazoles from Long Chain Olefinic Substrates
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Methyl undec-10-enoate (I), oct-1-ene (II) and methyl octadec-9(Z)-enoate (VII) have been converted into α-bromoalkyltetrazole derivatives (V, IX) using bromine, nitriles and sodium azide as reagents.Dehydrobromination of the α-bromoalkyltetrazoles with sodium ethoxide furnishes the alkenyltetrazoles (VI, X).
- Agarwal, Rajiv,Rauf, Abdul,Ahmad, M.,Osman, S. M.
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p. 175 - 177
(2007/10/02)
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- Oxybromination Catalysed by the Heteropolyanion Compound H5PMo10V2O40 in an Organic Medium: Selective para-Bromination of Phenol
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Selective bromination of phenol and its derivatives and the bromination of ketones and alkenes have been achieved by oxybromination at ambient conditions catalysed by the mixed addenda heteropolyanion compound H5PMo10V2O40, which is dissolved in a nonpolar chlorohydrocarbon solvent by complexation with tetraglyme.
- Neumann, Ronny,Assael, Igal
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p. 1285 - 1287
(2007/10/02)
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- HOMOLYTIC DISPLACEMENT AT CARBON CENTRES. XII. REGIOSPECIFIC FORMATION OF N-ALLYL AND N-CYCLOPROPYLCARBINYL SULPHONAMIDES AND OF ALLYL AND CYCLOPROPYL HALIDES IN THE REACTION OF N-HALOGENO COMPOUNDS WITH ORGANOCOBALOXIMES
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Several but-3-enyl and allylcobaloximes react regiospecifically with N-chloro-N-methyl sulphonamides to give N-cyclopropylcarbinyl- or rearranged N-allyl-N-methyl sulphonamides, by a process which is believed to take place by the attack of an N-centred radical at the terminal unsaturated carbon of the organic ligand, with displacement of cobaloxime(II).In contrast, N-bromoacetamide and several other N-halogenoimides react regiospecifically to the cyclopropylcarbinyl halide or the rearranged allyl halide by a process in which a halogen-containing free radical species attacks the terminal unsaturated carbon of the organocobaloxime.
- Johnson, Michael D.,Lampman, Gary M.,Koops, Roger W.,Gupta, B. Das
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p. 281 - 288
(2007/10/02)
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