- A General Method for the Dibromination of Vicinal sp3C-H Bonds Exploiting Weak Solvent-Substrate Noncovalent Interactions
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A general procedure of 1,2-dibromination of vicinal sp3 C-H bonds of arylethanes using N-bromosuccinimide as the bromide reagent without an external initiator has been established. The modulation of the strength of the intermolecular noncovalent interactions between the solvent and arylethane ethanes, quantitatively evaluated via quantum chemical calculations, allows us to circumvent the fact that arylethane ethane cannot be dibrominated through traditional methods. The mechanism was explored by both experiments and quantum chemical calculations, revealing a radical chain with HAA process.
- Qi, Zaojuan,Li, Weihe,Niu, Yanning,Benassi, Enrico,Qian, Bo
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supporting information
p. 2399 - 2404
(2021/03/03)
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- Preparation method of 1-aryl-1,2-dibromoethane
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The invention relates to a preparation method of 1-aryl-1,2-dibromoethane. The preparation method of 1-aryl-1,2-dibromoethane includes the steps: under a nitrogen atmosphere, a solvent, an aryl alkaneand N-bromosuccinimide are added in to a reaction tube in sequence, a dibromination reaction is conducted at 80-120 DEG C for 12-48 hours, then, the dibromination reaction is finished, the solvent isremoved through evaporation, and through column chromatography separation, 1-aryl-1,2-dibromoethane compounds are obtained. According to the preparation method of 1-aryl-1,2-dibromoethane, a synthesis technology is simple, reaction conditions are mild, the yield of 1-aryl-1,2-dibromoethane is high, and thus the preparation method of 1-aryl-1,2-dibromoethane is easy to industrialize.
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Paragraph 0023-0024
(2020/03/16)
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- Dehalogenation of vicinal dihalo compounds by 1,1′-bis(trimethylsilyl)-1: H,1′ H-4,4′-bipyridinylidene for giving alkenes and alkynes in a salt-free manner
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We report a transition metal-free dehalogenation of vicinal dihalo compounds by 1,1′-bis(trimethylsilyl)-1H,1′H-4,4′-bipyridinylidene (1) under mild conditions, in which trimethylsilyl halide and 4,4′-bipyridine were generated as byproducts. The synthetic protocol for this dehalogenation reaction was effective for a wide scope of dibromo compounds as substrates while keeping the various functional groups intact. Furthermore, the reduction of vicinal dichloro alkanes and vicinal dibromo alkenes also proceeded in a salt-free manner to afford the corresponding alkenes and alkynes.
- Rej, Supriya,Pramanik, Suman,Tsurugi, Hayato,Mashima, Kazushi
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supporting information
p. 13157 - 13160
(2017/12/26)
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- PPh3O as an Activating Reagent for One-Pot Stereoselective Syntheses of Di- and Polybrominated Esters from Simple Aldehydes
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(Chemical Equation Presented) An efficient one-pot method for the syntheses of di- and polybrominated esters from readily available aldehydes is reported. The direct use of the in situ generated byproduct PPh3O in the following reactions greatly improves the efficiency of the cascade. Also, the substrate scope of the reaction is proved to be broad.
- Yu, Tian-Yang,Wei, Hao,Luo, Yong-Chun,Wang, Yao,Wang, Zhu-Yin,Xu, Peng-Fei
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p. 2730 - 2736
(2016/04/26)
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- Triphenylphosphine oxide-catalyzed stereoselective poly- and dibromination of unsaturated compounds
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A novel PPh3O catalyzed bromophosphonium salt-mediated dibromination of α,β-unsaturated esters and β,γ- unsaturated α-ketoesters has been developed. The products were obtained with good to excellent yields and excellent diastereoselectivities.
- Yu, Tian-Yang,Wang, Yao,Hu, Xiu-Qin,Xu, Peng-Fei
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supporting information
p. 7817 - 7820
(2014/07/08)
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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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- 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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- 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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- Visible-light photoredox catalysis: Dehalogenation of vicinal dibromo-, α-halo-, and α,α-dibromocarbonyl compounds
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vic-Dibromo-, α-halo-, or α,α-dibromocarbonyl compounds can be efficiently dehalogenated using catalytic tris(2,2′-bipyridyl) ruthenium dichloride (Ru(bpy)3Cl2) in combination with 1,5-dimethoxynaphthalene (DMN) and ascorbate as sacrificial electron donor. For this process, a visible light promoted photocatalytic cycle is proposed that involves the reduction of carbon halogen bonds via free radical intermediates.
- Maji, Tapan,Karmakar, Ananta,Reiser, Oliver
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supporting information; experimental part
p. 736 - 739
(2011/03/20)
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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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- 79Br NMR spectroscopy as a practical tool for kinetic analysis
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79Br NMR spectroscopy has been used to monitor a series of reactions in which the bromide ion is produced, including the Menschutkin reaction of pyridine with a range of substituted benzyl bromides and a Heck coupling process. In cases where the process could also be monitored using 1H NMR spectroscopy, the kinetic analyses using heteronuclear magnetic resonance spectroscopy were shown to be completely consistent. Both the utility of the process in following reactions which may be difficult to analyse using other techniques and the practical limitations associated with solvent choice are discussed. Copyright
- Chan, Si Jia,Howe, Andrew G.,Hook, James M.,Harper, Jason B.
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experimental part
p. 342 - 347
(2010/02/27)
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- Microwave-assisted dehalogenation of α-haloketones by zinc and ammonium chloride in alcohol
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The treatment of α-haloketones with 1.5 equiv. of Zn and 1 equiv. of NH4Cl in ethanol for 0.5αmin gave the corresponding ketones with excellent yields under microwave irradiation. Vic-dibromides and 2,2-dibromoacetophenone can be efficiently debrominated to alkenes and acetophenones, respectively. Copyright Taylor & Francis Group, LLC.
- Li, Jian,Ye, Deju,Liu, Hong,Luo, Xiaoming,Jiang, Hualiang
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p. 567 - 575
(2008/04/12)
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- Dioxane dibromide-mediated solvent-free synthesis of vicinal dibromides
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Structurally varied vicinal dibromides have been synthesized in high yield and good purity through highly stereoselective anti-addition of bromine across the olefinic linkages using dioxane dibromide (DD) under solvent-free conditions. Copyright Taylor & Francis Group, LLC.
- Chaudhuri, Subrata Kumar,Roy, Sanchita,Saha, Manabendra,Bhar, Sanjay
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p. 271 - 274
(2007/10/03)
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- Quantitative structure-activity relationships of pine weevil antifeedants, a multivariate approach
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Antifeedant activity of mainly phenylpropanoic, cinnamic, and benzoic acids esters was tested on the pine weevil, Hylobius abietis (L.). Of 105 compounds screened for activity, 9 phenylpropanoates, 3 cinnamates, and 4 benzoates were found to be highly active antifeedants. To understand the structure-activity relationships of these compounds, a multivariate analysis study was performed. A number of molecular and substituent descriptors were calculated and correlated to results from two-choice feeding tests with H. abietis. Three local models were developed that had good internal predictive ability. External test sets showed moderate predictivity. In general, low polarity, small size, and high lipophilicity were characteristics for compounds having good antifeedant activity.
- Sunnerheim, Kerstin,Nordqvist, Anneli,Nordlander, Goeran,Borg-Karlson, Anna-Karin,Unelius, C. Rickard,Bohman, Bjoern,Nordenhem, Henrik,Hellqvist, Claes,Karlen, Anders
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p. 9365 - 9372
(2008/03/17)
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- Aziridines as templates: A general strategy for the stereospecific synthesis of 2-azetidinones
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Various routes to a variety of azridine-2-carboxylates have been described and the stereochemistry of these compounds has been determined by spectroscopic methods. Further, greater diversity of β-lactams via ring expansion of these azridines-2-carboxylates were obtained by a general, efficient and direct stereospecific approach.
- Sharma,Kanwar, Seema,Rajpoot, Shivani
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- A convenient halogenation of α,β-unsaturated carbonyl compounds with OXONE and hydrohalic acid (HBr,HCl)
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Mixtures of OXONE and hydrobromic acid or hydrochloric acid afford solutions of bromine or chlorine, respectively, α-Bromo- or α-chloro-α,β-unsaturated carbonyl compounds were prepared by addition of hydrobromic acid or hydrochloric acid to the mixture of
- Kim, Kyoung-Mahn,Park, In-Hwan
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p. 2641 - 2644
(2007/10/03)
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- Kinetic study of the addition of trihalides to unsaturated compounds in ionic liquids. Evidence of a remarkable solvent effect in the reaction of ICl2-
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The kinetic constants and activation parameters for the reactions of Br3- and ICl2- with some alkenes and alkynes have been determined in the ionic liquids [bmim][PF6], [emim][Tf2N], [bmim][Tf2N], [hmim][TF2N], [bm2im] [Tf2N], and [bpy][TF2N] (where emim = 1-ethyl-3-methyl-imidazolium, bmim = 1-butyl-3-methylimidazolium, hmim = 1-hexyl-3-methylimidazolium, bm2im = 1-butyl-2,3-dimethylimidazolium, bpy = butylpyridinium, PF6 = hexafluorophosphate, and Tf 2N = bis(trifluoromethylsulfonyl)imide) and in 1,2-dichloroethane. The rates of both reactions increase on going from 1,2-dichloroethane to ILs. Evidence suggests that, while the hydrogen bonding ability of the imidazolium cation is probably the main factor able to increase the rate of the addition of ICl2- to double and triple bonds, this property has no effect on the electrophilic addition of Br3- to alkenes and alkynes. Furthermore, in the case of the ICl2- reaction, the hydrogen bonding ability of ILs can be exploited to suppress the unwanted nucleophilic substitution reaction on the products by the Cl - anion.
- Chiappe, Cinzia,Pieraccini, Daniela
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p. 6059 - 6064
(2007/10/03)
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- 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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p. 925 - 929
(2007/10/03)
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- (Phenylalkylaminoalkyloxy)-heteroaryl-compounds, processes and intermediates for their production and pharmaceutical compositions containing them
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3-(Phenylalkylaminoalkylozy)-heteroaryl compounds having heart rate lowering and/or anti-ischemic effects, methods for their preparation and pharmaceutical compositions containing them are described. The compounds correspond to the general formula I STR1 or to the general formula XXXI STR2 in which the substituents have the meanings given the specification.
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- Perfluorohexane as a novel reaction medium for bromination reactions
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Perfluorohexane is shown to be a good alternative to carbon tetrachloride as a non-toxic, non-ozone-depleting, inert reaction medium for bromination reactions. Yields of brominated products were nearly quantitative and the reaction work-up was easier.
- Pereira,Savage,Simpson
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p. 1023 - 1026
(2007/10/02)
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- 1,2-asymmetric induction in radical reactions. Deuteration and allylation reactions of β-oxy-α-bromo esters
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Chiral radicals were generated by halogen abstraction reactions of β-oxy-α-bromo esters and their asymmetric deuteration and allylation reactions were studied.
- Curran,Ramamoorthy
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p. 4841 - 4858
(2007/10/02)
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- 2,3-Dihalo-2,3-(disubstituted) propanoate antimicrobial compounds
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Antimicrobial compounds of the formula: STR1 wherein Hal is bromine or chlorine; R is C1-4 alkyl, straight or branched chain; and one of R1 and R2 is hydrogen and the other is selected from the group consisting of C3-
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- Transmission of substituent effects through extended systems-III. p-Substituted ethyl trans cinnamates and phenylpropiolates
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Infrared data and 13C chemical shifts are reported for a series of ethyl p-substituted trans-cinnamates and ethyl phenylpropiolates.The i.r. values include intensities for the benzene, ethylene and carbonyl vibrations which allow an estimation of resonance effects.The relative importance of the various mechanisms of transmission of substituent effects are discussed and compared to those previously reported for p-substituted trans cinnamonitriles.It is shown that the carbon-carbon triple bond is less efficient in transmitting substituent effects than carbon-carbon double bonds.
- Butt, G.,Topsom, R. D.
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p. 649 - 654
(2007/10/02)
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- Substituent Dependence of the Selectivity in Alkene Bromination through Bromocarbenium Ions
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Substituent effects on the rates of bromination of alkenes GαRαC=CRβR'β, where G is a conjugatively electron-donating group, are consistent with a carbenium ion like transition state, whereas by the same criteria the transition state for nonconjugated alkenes is bromonium type.The reactivities of compounds with the same substituent G are analyzed in terms of the sensitivity to structural and solvent effects.The lowest sensitivity is attributed to the earliest transition state.The dependence of the reaction constant on G leads to a general equation including cross terms: log k = -7.7Σ(?p+)α - 13.7Σ(?m+)β - 7.0(?p+)Gα(?p+)Rα - 5.8Σ(?p+)αΣ(?m+)β + 1.64.The carbenium ion character, common to both bromination and hydration, results in highly dissymmetric α- and β-substituent effects.However, these two reactions respond differently to β-substituents: a β methyl increases the bromination rate but decreases the hydration rate.Similarities and differences in the transition state models are discussed; the kinetic data suggest that the transition state is earlier in bromination than in hydration.
- Bienvenue-Goetz, Elizabeth,Dubois, Jaques-Emile
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p. 5388 - 5392
(2007/10/02)
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