- Copper-catalyzed regioselective chloroamination of alkenes with chlorotrimethylsilane and n-fluorobenzenesulfonimide under microwave-assisted conditions
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A copper-catalyzed chloroamination of alkenes with chlorotrimethylsilane and N-fluorobenzenesulfonimide has been developed. The reactions were complete within 1 h at 120 °C by means of microwave heating. The present chloroamination proceeds with a perfect regioselectivity and is compatible with various functional groups. The preliminary mechanistic investigation revealed that the reaction involves a radical process. The utility of the present method was demonstrated by scalable, operationally simple and safe system.
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- A Direct S0→Tn Transition in the Photoreaction of Heavy-Atom-Containing Molecules
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According to the Grotthuss–Draper law, light must be absorbed by a substrate to initiate a photoreaction. There have been several reports, however, on the promotion of photoreactions using hypervalent iodine during irradiation with light from a non-absorbing region. This contradiction gave rise to a mystery regarding photoreactions involving hypervalent iodine. We demonstrated that the photoactivation of hypervalent iodine with light from the apparently non-absorbing region proceeds via a direct S0→Tn transition, which has been considered a forbidden process. Spectroscopic, computational, and synthetic experimental results support this conclusion. Moreover, the photoactivation mode could be extended to monovalent iodine and bromine, as well as bismuth(III)-containing molecules, providing new possibilities for studying photoreactions that involve heavy-atom-containing molecules.
- Kuribara, Takahito,Matsumoto, Koki,Muranaka, Atsuya,Nagasawa, Sho,Nakajima, Masaya,Nemoto, Tetsuhiro,Uchiyama, Masanobu
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- STRUCTURE OF POLYMERS ON THE BASIS OF CHLORINATED STYRENE AND SODIUM DISULPHIDE
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A polycondensation of a mixture of halogen derivatives of styrene obtained at direct chlorination of styrene and containing ca. 80 percent α,β-dichloroethylbenzene and sodium disulphide was studied.Polysulphide liquid low molecular polymers were obtained.By means of molecular spectroscopy, fractionation and the elemental analysis the structure of the synthesized products was studied.It was proved, that the essential unit is the styrenedisulphide one.The role of monofunctional monomer and of nonchlorinated styrene in reaction conditions was indicated
- Todorova, D.,Mladenov, Iv.,Marcov, M.
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- Convenient in situ generation of various dichlorinating agents from oxone and chloride: Diastereoselective dichlorination of allylic and homoallylic alcohol derivatives
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A safe and convenient protocol was developed for in situ generation of various dichlorinating agents (cf. Cl2, NCl3, Et 4NCl3, ArICl2) from oxone and chloride. The synthetic utility of this protocol was demonstrated by diastereoselective dichlorination of a series of allylic and homoallylic alcohol derivatives with excellent yields and diastereoselectivity. The Royal Society of Chemistry 2013.
- Ren, Jingyun,Tong, Rongbiao
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- Quaternary ammonium polychlorides as efficient reagents for chlorination of unsaturated compounds
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Chlorination of unsaturated compounds by benzyltributylammonium polychlorides results in higher yields of addition products compared to those obtained with molecular chlorine.
- Zelikman,Tyurin,Smirnov,Zyk
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- Reaction of Styrene with Chlorine Dioxide
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Reaction of styrene with chlorine dioxide under various conditions selectively produces 1-phenyl- 2-chloroethanone, with 1-phenyl-2-chloroethanol, 2-hydroxy-1-phenylethanone, (1,2-dichloroethyl)benzene, (2-chloro-1-phenyl)ethene, and (1,2,2-trichloroethyl
- Loginova,Chukicheva, I. Yu.,Kuchin
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Read Online
- Dichlorination of olefins with diphenyl sulfoxide/oxalyl chloride
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The combination of diphenyl sulfoxide and oxalyl chloride was used to accomplish the dichlorination of olefins, in which chlorodiphenylsulfonium salt generated in situ was proposed to be the real active species as a chloronium ion source.
- Ding, Rui,Huang, Shuai,Wang, Qiyi,Liu, Yongguo,Sun, Baoguo,Tian, Hongyu
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Read Online
- The Electrochemical cis-Chlorination of Alkenes
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The first example for the electrochemical cis-dichlorination of alkenes is presented. The reaction can be performed with little experimental effort by using phenylselenyl chloride as catalyst and tetrabutylammoniumchloride as supporting electrolyte, which also acts as nucleophilic reagent for the SN2-type replacement of selenium versus chloride. Cyclic voltammetric measurements and control experiments revealed a dual role of phenylselenyl chloride in the reaction. Based on these results a reaction mechanism was postulated, where the key step of the process is the activation of a phenylselenyl chloride-alkene adduct by electrochemically generated phenylselenyl trichloride. Like this, different aliphatic and aromatic cyclic and acyclic alkenes were converted to the dichlorinated products. Thereby, throughout high diastereoselectivities were achieved for the cis-chlorinated compounds of >95 : 5 or higher.
- Strehl, Julia,Fastie, Cornelius,Hilt, Gerhard
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supporting information
p. 17341 - 17345
(2021/10/23)
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- Flexible on-site halogenation paired with hydrogenation using halide electrolysis
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Direct electrochemical halogenation has appeared as an appealing approach in synthesizing organic halides in which inexpensive inorganic halide sources are employed and electrical power is the sole driving force. However, the intrinsic characteristics of direct electrochemical halogenation limit its reaction scope. Herein, we report an on-site halogenation strategy utilizing halogen gas produced from halide electrolysis while the halogenation reaction takes place in a reactor spatially isolated from the electrochemical cell. Such a flexible approach is able to successfully halogenate substrates bearing oxidatively labile functionalities, which are challenging for direct electrochemical halogenation. In addition, low-polar organic solvents, redox-active metal catalysts, and variable temperature conditions, inconvenient for direct electrochemical reactions, could be readily employed for our on-site halogenation. Hence, a wide range of substrates including arenes, heteroarenes, alkenes, alkynes, and ketones all exhibit excellent halogenation yields. Moreover, the simultaneously generated H2at the cathode during halide electrolysis can also be utilized for on-site hydrogenation. Such a strategy of paired halogenation/hydrogenation maximizes the atom economy and energy efficiency of halide electrolysis. Taking advantage of the on-site production of halogen and H2gases using portable halide electrolysis but not being suffered from electrolyte separation and restricted reaction conditions, our approach of flexible halogenation coupled with hydrogenation enables green and scalable synthesis of organic halides and value-added products.
- Shang, Xiao,Liu, Xuan,Sun, Yujie
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supporting information
p. 2037 - 2043
(2021/03/26)
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- TEMPO-Regulated Regio- and Stereoselective Cross-Dihalogenation with Dual Electrophilic X+ Reagents
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A TEMPO catalyzed cross-dihalogenation reaction was established via redox-regulation of the otherwise complex system of dual electrophilic X+ reagents. Formally, the ICl, BrCl, I2 and Br2 were generated in-situ, which enabled high regio- or stereoselective access to a myriad of iodochlorination, bromochlorination and homo-dihalogenation products with a wide spectrum of functionalities. With its mild conditions and operational simplicity, this method could enable wide applications in organic synthesis, which was exemplified by divergent synthesis of two pharmaceuticals. Detailed mechanistic investigations via radical clock reaction, pinacol ring expansion and Hammett experiments were conducted, which confirmed the intermediacy of halonium ion. In addition, a dynamic catalytic model based on the versatile catalytic role of TEMPO was proposed to explain the selective outcomes.
- Kong, Yi,Cao, Tongxiang,Zhu, Shifa
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supporting information
p. 3004 - 3010
(2021/08/23)
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- Visible-Light-Induced Vicinal Dichlorination of Alkenes through LMCT Excitation of CuCl2
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This work demonstrates photoredox vicinal dichlorination of alkenes, based on the homolysis of CuCl2 in response to irradiation with visible light. This catalysis proceeds via a ligand to metal charge transfer process and provides an exciting opportunity for the synthesis of 1,2-dichloride compounds using an inexpensive, low-molecular-weight chlorine source. This new process exhibits a wide substrate scope, excellent functional group tolerance, extraordinarily mild conditions and does not require external ligands. Mechanistic studies show that the ready formation of chlorine atom radicals is responsible for the facile formation of C?Cl bonds in this synthetic process.
- Li, Jingjing,Lian, Pengcheng,Long, Wenhao,Wan, Xiaobing,Zheng, Yonggao
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supporting information
p. 23603 - 23608
(2020/10/29)
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- Selective monochlorination of unsymmetrical vicinal diols with chlorinated iminium chlorides
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Chlorinated iminium chlorides have been identified to promote the highly efficient and selective mono-chlorination of unsymmetrical vicinal diols. Vilsmeier reagent, namely, (chloromethylene)dimethyliminium chloride, enables highly reactive and regioselective chlorination of 1,2- and 1,3-diols featured one secondary benzylic hydroxy group and one primary aliphatic hydroxy group to give the corresponding 1,2- and 1,3-chlorohydrins. Viehe's salts (α,α-dichloro iminium salts) exhibit excellent reactivity and good selectivity for vicinal diols to give the corresponding chlorohydrin carbamates via a cyclic intermediate in situ. The chlorination protocols tolerate diverse functional groups, including halogens, naphthalene rings, nitro, and cyano. Moreover, the optical purity of chiral diols could be retained during this chlorination reaction.
- Li, Chengyang,Li, Xiaotong,Wang, Yu,Wu, Xiaoyu,Xie, Xiaomin,Yang, Liqun,Zhang, Zhaoguo
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- Ph 3 P/I - -Promoted Dichlorination or Dibromination of Epoxides with XCH 2 CH 2 X (X = Cl or Br)
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Ph 3 P/I - -promoted dichlorination and dibromination of epoxides by using XCH 2 CH 2 X (X = Cl or Br) as the halogen source and reaction solvent is described. All reagents are widely available and easy to handle, and mild conditions and operational simplicity make this protocol attractive.
- Long, Jin,Chen, Jia,Li, Rong,Liu, Zhuo,Xiao, Xuan,Lin, Jin-Hong,Zheng, Xing,Xiao, Ji-Chang
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supporting information
p. 181 - 184
(2019/01/14)
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- CV-driven Optimization: Cobalt-Catalyzed Electrochemical Expedient Oxychlorination of Alkenes via ORR
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Instead of screening reaction conditions by yield-based chemical trial-and-error, potential-based cyclic voltammetry was alternatively employed for optimization of electrochemical oxychlorination of alkenes. With this unconventional screening method, the catalyst system including catalysts, molar ratio of chloride sources and solvents were identified in a rational, time- and energy-efficient manner. The optimal catalytic system in combination with oxygen reduction reaction enabled broad substrate scopes for the desired transformation by taking advantages of persistent radical effect. UV-vis and CV titration experiments confirmed the in-situ formed catalytic species [CoCl5]. Moreover, cyclic voltammetry was applied to obtain mechanistic insights in our reaction system. (Figure presented.).
- Tian, Siyu,Lv, Shide,Jia, Xiaofei,Ma, Li,Li, Baoying,Zhang, Guofeng,Gao, Wei,Wei, Yingqin,Chen, Jianbin
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supporting information
p. 5626 - 5633
(2019/11/22)
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- Organocatalytic Chlorination of Alcohols by P(III)/P(V) Redox Cycling
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A catalytic system for the chlorination of alcohols under Appel conditions was developed. Benzotrichloride is used as a cheap and readily available chlorinating agent in combination with trioctylphosphane as the catalyst and phenylsilane as the terminal reductant. The reaction has several advantages over other variants of the Appel reaction, e.g., no additional solvent is required and the phosphane reagent is used only in catalytic amounts. In total, 27 different primary, secondary, and tertiary alkyl chlorides were synthesized in yields up to 95%. Under optimized conditions, it was also possible to convert epoxides and an oxetane to the dichlorinated products.
- Longwitz, Lars,Jopp, Stefan,Werner, Thomas
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p. 7863 - 7870
(2019/06/27)
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- Visible Light-Induced Oxidative Chlorination of Alkyl sp3 C-H Bonds with NaCl/Oxone at Room Temperature
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A visible light-induced monochlorination of cyclohexane with sodium chloride (5:1) has been successfully accomplished to afford chlorocyclohexane in excellent yield by using Oxone as the oxidant in H2O/CF3CH2OH at room temperature. Other secondary and primary alkyl sp3 C-H bonds of cycloalkanes and functional branch/linear alkanes can also be chlorinated, respectively, under similar conditions. The selection of a suitable organic solvent is crucial in these efficient radical chlorinations of alkanes in two-phase solutions. It is studied further by the achievement of high chemoselectivity in the chlorination of the benzyl sp3 C-H bond or the aryl sp2 C-H bond of toluene.
- Zhao, Mengdi,Lu, Wenjun
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supporting information
p. 4560 - 4563
(2017/09/11)
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- Electrocatalytic Radical Dichlorination of Alkenes with Nucleophilic Chlorine Sources
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We report a Mn-catalyzed electrochemical dichlorination of alkenes with MgCl2 as the chlorine source. This method provides operationally simple, sustainable, and efficient access to a variety of vicinally dichlorinated compounds. In particular, alkenes with oxidatively labile functional groups, such as alcohols, aldehydes, sulfides, and amines, were transformed into the desired vicinal dichlorides with high chemoselectivity. Mechanistic data are consistent with metal-mediated Cl atom transfer as the predominant pathway enabling dual C-Cl bond formation and contradict an alternative pathway involving electrochemical evolution of chlorine gas followed by Cl2-mediated electrophilic dichlorination.
- Fu, Niankai,Sauer, Gregory S.,Lin, Song
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supporting information
p. 15548 - 15553
(2017/11/06)
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- Reactions of selenium dihalides with vinylbenzenes
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Alkoxyselenation of vinylbenzenes with selenium dihalides was accomplished for the first time. The reaction with selenium dibromide was the most efficient. Selenium dibromide reacted with vinylbenzene and 1-chloro-4-(prop-1-en-2-yl)benzene in chloroform or methylene chloride in the presence of methanol or ethanol to give the corresponding Markovnikov adducts, bis(2-alkoxy-2-phenylethyl) selenides and bis[2-alkoxy-2-(4-chlorophenyl)propyl] selenides in 82–95% yield with high regioselectivity. Bis(2-halo-2-phenylethyl) selenides can be obtained at low temperature (–60°C).
- Potapov,Khabibulina,Musalov,Albanov,Amosova
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p. 322 - 325
(2017/05/09)
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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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- Cross-Linked Artificial Enzyme Crystals as Heterogeneous Catalysts for Oxidation Reactions
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Designing systems that merge the advantages of heterogeneous catalysis, enzymology, and molecular catalysis represents the next major goal for sustainable chemistry. Cross-linked enzyme crystals display most of these essential assets (well-designed mesoporous support, protein selectivity, and molecular recognition of substrates). Nevertheless, a lack of reaction diversity, particularly in the field of oxidation, remains a constraint for their increased use in the field. Here, thanks to the design of cross-linked artificial nonheme iron oxygenase crystals, we filled this gap by developing biobased heterogeneous catalysts capable of oxidizing carbon-carbon double bonds. First, reductive O2 activation induces selective oxidative cleavage, revealing the indestructible character of the solid catalyst (at least 30 000 turnover numbers without any loss of activity). Second, the use of 2-electron oxidants allows selective and high-efficiency hydroxychlorination with thousands of turnover numbers. This new technology by far outperforms catalysis using the inorganic complexes alone, or even the artificial enzymes in solution. The combination of easy catalyst synthesis, the improvement of "omic" technologies, and automation of protein crystallization makes this strategy a real opportunity for the future of (bio)catalysis.
- Lopez, Sarah,Rondot, Laurianne,Leprêtre, Chloé,Marchi-Delapierre, Caroline,Ménage, Stéphane,Cavazza, Christine
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supporting information
p. 17994 - 18002
(2017/12/26)
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- Synthesis of bis(2-haloalkyl) selanes and selenides based on selenium dioxide and terminal alkenes
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Selenium tetrahalides generated from selenium dioxide and hydrogen halides (HCl, HBr) reacted with hex-1-ene, hept-1-ene, and oct-1-ene at a SeO2?alkene molar ratio of 1: 2 to give mixtures of dihalobis-(2-haloalkyl)-λ4-selanes (yield 80?90%) and bis(2-haloalkyl) selenides (yield 5?12%). Halogenation of the resulting mixtures afforded 85?93% (calculated on the initial SeO2) of the corresponding dihalobis(2-haloalkyl)-λ4-selanes, and the reduction of the same mixtures with Na2S2O5 gave bis(2-haloalkyl) selenides in 80?86% yield. In the reaction with a SeO2?alkene ratio of 5: 8, pure dihalobis(2-haloalkyl)-λ4-selanes were formed in 84?93% yield. Dichlorobis(2-chloro-2-phenylethyl)-λ4-selane was obtained in 72% yield in the reaction of SeO2?HCl with styrene.
- Musalov,Kurkutov,Potapov,Khabibulina,Albanov,Amosova
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p. 1809 - 1814
(2018/02/06)
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- Ketone-catalyzed photochemical C(sp3)–H chlorination
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Photoexcited arylketones catalyze the direct chlorination of C(sp3)–H groups by N- chlorosuccinimide. Acetophenone is the most effective catalyst for functionalization of unactivated C–H groups while benzophenone provides better yields for benzylic C–H functionalization. Activation of both acetophenone and benzophenone can be achieved by irradiation with a household compact fluorescent lamp. This light-dependent reaction provides a better control of the reaction as compared to the traditional chlorination methods that proceed through a free radical chain propagation mechanism.
- Han, Lei,Xia, Ji-Bao,You, Lin,Chen, Chuo
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p. 3696 - 3701
(2017/06/13)
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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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- Vicinal dichlorination of olefins using NH4Cl and oxone
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A mild and efficient protocol for the preparation of 1,2-dichloroalkane derivatives from olefins using NH4Cl and Oxone at room temperature is described. A variety of terminal, internal, and cyclic alkenes reacted smoothly to give the corresponding dichlorinated products in good to excellent yields. Moreover, 1,2-disubstituted symmetrical and unsymmetrical olefins dichlorinated with moderate to excellent diastereoselectivity. This method precludes the use of acidic additives and transition metals in the synthesis of vicinal dichlorides.
- Swamy, Peraka,Reddy, Marri Mahender,Kumar, Macharla Arun,Naresh, Mameda,Narender, Nama
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p. 251 - 257
(2014/03/21)
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- Rasta resin-triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions
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Heterogeneous polymer-supported triphenylphosphine oxides based on the rasta resin architecture have been synthesized, and applied as reagent precursors in a wide range of halogenation reactions. The rasta resin-triphenylphosphine oxides were reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn were reacted with alcohols, aldehydes, aziridines and epoxides to form halogenated products in high yields after simple purification. The polymersupported triphenylphosphine oxides formed as a byproduct during these reactions could be recovered and reused numerous times with no appreciable decrease in reactivity.
- Xia, Xuanshu,Toy, Patrick H.
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p. 1397 - 1405
(2014/07/22)
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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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- Kinetics and mechanism of styrene epoxidation by chlorite: Role of chlorine dioxide
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An investigation of the kinetics and mechanism for epoxidation of styrene and para-substituted styrenes by chlorite at 25 °C in the pH range of 5-6 is described. The proposed mechanism in water and water/acetonitrile includes seven oxidation states of chlorine (-I, 0, I, II, III, IV, and V) to account for the observed kinetics and product distributions. The model provides an unusually detailed quantitative mechanism for the complex reactions that occur in mixtures of chlorine species and organic substrates, particularly when the strong oxidant chlorite is employed. Kinetic control of the reaction is achieved by the addition of chlorine dioxide to the reaction mixture, thereby eliminating a substantial induction period observed when chlorite is used alone. The epoxidation agent is identified as chlorine dioxide, which is continually formed by the reaction of chlorite with hypochlorous acid that results from ClO produced by the epoxidation reaction. The overall stoichiometry is the result of two competing chain reactions in which the reactive intermediate ClO reacts with either chlorine dioxide or chlorite ion to produce hypochlorous acid and chlorate or chloride, respectively. At high chlorite ion concentrations, HOCl is rapidly eliminated by reaction with chlorite, minimizing side reactions between HOCl and Cl2 with the starting material. Epoxide selectivity (>90% under optimal conditions) is accurately predicted by the kinetic model. The model rate constant for direct reaction of styrene with ClO2(aq) to produce epoxide is (1.16 ± 0.07) × 10-2 M -1 s-1 for 60:40 water/acetonitrile with 0.20 M acetate buffer. Rate constants for para substituted styrenes (R = -SO3 -, -OMe, -Me, -Cl, -H, and -NO2) with ClO2 were determined. The results support the radical addition/elimination mechanism originally proposed by Kolar and Lindgren to account for the formation of styrene oxide in the reaction of styrene with chlorine dioxide.
- Leigh, Jessica K.,Rajput, Jonathan,Richardson, David E.
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supporting information
p. 6715 - 6727
(2014/07/22)
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- Convenient chlorination with concentrated hydrochloric acid in the presence of iodosylbenzene
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An efficient chlorination of -keto esters, 1,3-diketones, and alkenes was performed conveniently with concentrated HCl in the presence of PhIO, selectively giving -chloro - keto esters, 2-chloro-1,3-diketones, and 1,2-dichloroalkanes, respectively. It was suggested that the chlorination took place with (dichloroiodo)benzene generated in situ. A selective anti-addition was observed in the chlorination of indene. Georg Thieme Verlag Stuttgart New York.
- Kitamura, Tsugio,Tazawa, Yui,Morshed, Mohammad Hasan,Kobayashi, Soichi
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experimental part
p. 1159 - 1162
(2012/05/20)
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- Aromatic substitution in ball mills: Formation of aryl chlorides and bromides using potassium peroxomonosulfate and NaX
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Aryl chlorides and bromides are formed from arenes in a ball mill using KHSO5 and NaX (X = Cl, Br) as oxidant and halogen source, respectively. Investigation of the reaction parameters identified operating frequency, milling time, and the number of milling balls as the main influencing variables, as these determine the amount of energy provided to the reaction system. Assessment of liquid-assisted grinding conditions revealed, that the addition of solvents has no advantageous effect in this special case. Preferably activated arenes are halogenated, whereby bromination afforded higher product yields than chlorination. Most often reactions are regio- and chemoselective, since p-substitution was preferred and concurring side-chain oxidation of alkylated arenes by KHSO5 was not observed. The Royal Society of Chemistry.
- Schmidt, Robert,Stolle, Achim,Ondruschka, Bernd
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p. 1673 - 1679
(2013/02/22)
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- Pyridine-assisted chlorinations and oxidations by palladium(IV)
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The reactivity of the bis-NHC complex LPdIVCl4 (L = κ2-[R-NHCCH2NHC-R] with R = C14H 29) in chlorinations and oxidations of organic substrates was considerably increased in the presence of pyridine. For alkene chlorinations, this effect was due to the in situ formation of highly reactive LPd IVCl3(py)+, which was able to transfer Cl + to the C=C bond in a ligand-mediated process (devoid of π complexation), which did not require py dissociation. The enhanced reactivity in the presence of pyridine also extended to the oxidation of secondary and benzylic alcohols under mild conditions in a reaction where py served as a base, broadening the known scope of reactivity for PdIV complexes. LPdIVCl3(py)+ could be formed from Cl -/py exchange or from the oxidation of LPdIICl(py) + by Cl2. Taking advantage of the enhanced reactivities that pyridine coordination imparted on both PdII and PdIV complexes allowed for the catalytic chlorination of styrene with LPd IVCl4 as a sacrificial oxidant, thereby establishing the principal feasibility of PdII/PdIV catalyses that obviates PdII activations of the substrate.
- McCall, A. Scott,Kraft, Stefan
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scheme or table
p. 3527 - 3538
(2012/06/16)
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- Reactions of selenium dichloride and dibromide with unsaturated ethers. Annulation of 2,3-dihydro-1,4-oxaselenine to the benzene ring
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Highly chemo-, regio-, and stereoselective syntheses of novel organoselenium compounds from selenium dichloride or dibromide and unsaturated ethers are described. The reactions of selenium dichloride with allyl and propargyl phenyl ethers afford either annulated products or bis-adducts depending on the conditions. The first examples of annulation of 3-chloromethyl- and 3-chloromethylene-2,3-dihydro-1,4-oxaselenine to the benzene ring are reported.
- Potapov, Vladimir A.,Musalov, Maxim V.,Amosova, Svetlana V.
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body text
p. 4606 - 4610
(2011/09/30)
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- Solvent-free, efficient, and high regioselective conversion of epoxides to symmetrical and unsymmetrical vic-dihalides using chlorodiphenylphosphine and n-halosuccinimides
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A new method is described for the efficient and high regioselective conversion of epoxides to symmetrical and unsymmetrical vic-dihalides in high yields using chlorodiphenylphosphine and N-halosuccinimides under solvent-free and neutral conditions and at room temperature. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor & Francis Group, LLC.
- Aghapour, Ghasem,Afzali, Asieh
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p. 598 - 605
(2011/05/15)
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- Bis- N -heterocyclic carbene palladium(IV) tetrachloride complexes: Synthesis, reactivity, and mechanisms of direct chlorinations and oxidations of organic substrates
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This Article describes the preparation and isolation of novel octahedral CH2-bridged bis-(N-heterocyclic carbene)palladium(IV) tetrachlorides of the general formula LPdIVCl4 [L = (NHC)CH 2(NHC)] from LPdIICl2 and Cl2. In intermolecular, nonchelation-controlled transformations LPdIVCl 4 reacted with alkenes and alkynes to 1,2-dichlorination adducts. Aromatic, benzylic, and aliphatic C-H bonds were converted into C-Cl bonds. Detailed mechanistic investigations in the dichlorinations of alkenes were conducted on the 18VE PdIV complex. Positive solvent effects as well as kinetic measurements probing the impact of cyclohexene and chloride concentrations on the rate of alkene chlorination support a PdIV-Cl ionization in the first step. Product stereochemistry and product distributions from various alkenes also support Cl+-transfer from the pentacoordinated PdIV-intermediate LPdIVCl 3+ to olefins. 1-Hexene/3-hexene competition experiments rule out both the formation of π-complexes along the reaction coordinate as well as in situ generated Cl2 from a reductive elimination process. Instead, a ligand-mediated direct Cl+-transfer from LPd IVCl3+ to the π-system is likely to occur. Similarly, C-H bond chlorinations proceed via an electrophilic process with in situ formed LPdIVCl3+. The presence of a large excess of added Cl- slows cyclohexene chlorination while the presence of stoichiometric amounts of chloride accelerates both PdIV-Cl ionization and Cl+-transfer from LPdIVCl3 +. 1H NMR titrations, T1 relaxation time measurements, binding isotherms, and Job plot analysis point to the formation of a trifurcated Cl-...H-C bond in the NHC-ligand periphery as a supramolecular cause for the accelerated chemical events involving the metal center.
- McCall, A. Scott,Wang, Hongwang,Desper, John M.,Kraft, Stefan
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supporting information; experimental part
p. 1832 - 1848
(2011/04/15)
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- Catalysis of phosphorus(V)-mediated transformations: Dichlorination reactions of epoxides under appel conditions
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A stereospecific triphenylphosphine oxide-catalyzed 1,2-dichlorination reaction of epoxides has been developed. The reaction is effective for a range of terminal and internal epoxides. In contrast to the classical Appel-type dichlorination of epoxides, oxalyl chloride is used as a stoichiometric reagent to generate the chlorophosphonium salt responsible for dichlorination from catalytic triphenylphosphine oxide.
- Denton, Ross M.,Tang, Xiaoping,Przeslak, Adam
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supporting information; experimental part
p. 4678 - 4681
(2010/12/24)
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- Regiospecific oxyhalogenation of aromatics over SBA-15-supported nanoparticle group IV-VI metal oxides
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TiOx, VOx, MoOx and WOx supported on SBA-15 exhibit efficient catalytic activity for oxyhalogenation of aromatics with the H2O2-halide ion system. Unlike the hitherto known solid catalysts, these reusable catalysts yield the para-halogenated product with 100% selectivity at 298 K and moderate acidic pH (3-5). The catalytic activity was enhanced by five orders of magnitude when supported on SBA-15. Springer Science+Business Media, LLC 2010.
- Saikia,Rajesh,Srinivas,Ratnasamy
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scheme or table
p. 190 - 201
(2010/11/05)
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- Effective Au(III)-CuCl2-catalyzed addition of alcohols to alkenes
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Alkenes can be activated by Au(III) catalysts, and the effective addition of alcohols to alkenes can be carried out under mild conditions with Au(III), provided that catalytic amounts of CuCl2 are added, which significantly stabilize the cationic Au(III). The Royal Society of Chemistry.
- Zhang, Xin,Corma, Avelino
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p. 3080 - 3082
(2008/02/10)
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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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- 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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- 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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- Formation of 8-Membered Ring Compounds by the Reaction of Styrene Oxide with MoCl5
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Styrene oxide reacted with group 5 and 6 metal halides in 1,2-dichloroethane to afford an 8-membered ring compound, 2,3,6,7-dibenzo-9- oxabicyclo[3,3,1]nona-2,6-diene. When the reaction was carried out in benzene instead of 1,2-dichloroethane as a solvent, unexpected new 8-membered ring product, tribenzobicyclo[3.3.2]decatriene, and 1,1,2-triphenylethane were obtained. The structures of the 8-membered ring compounds were confirmed by X-ray analysis.
- Guo, Qiaoxia,Nakajima, Kiyohiko,Takahashi, Tamotsu
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p. 1044 - 1045
(2007/10/03)
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- Use of a fluorous bridge for diffusion controlled uptake of molecular chlorine in chlorine addition to alkenes
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Fluorous solvent was used for passive transport of molecular chlorine from one side of the U-tube to the other, where addition of chlorine to alkenes was quantitative and diffusion controlled.
- Iskra, Jernej,Stavber, Stojan,Zupan, Marko
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p. 2496 - 2497
(2007/10/03)
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- vic-Dichlorination of olefins with sodium chlorite, Mn(acac)3, and moist alumina in dichloromethane
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Aliphatic, alicyclic, and aromatic alkenes underwent smooth vicdichlorination upon treatment with a reagent combination of NaClO2, Mn(acac)3 catalyst, and chromatographic neutral alumina preloaded with a small amount of water in dichloromethane under mild conditions.
- Yakabe, Shigetaka,Hirano, Masao,Morimoto, Takashi
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p. 1871 - 1878
(2007/10/03)
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- Reaction of Aromatic and Unsaturated Compounds with the Potassium Permanganate/HCI (HBr) Acetonitrile Reagent
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Addition of hydrochloric or hydrobromic acid to a solution of potassium permanganate in acetonitrile produced a homogeneous mixture, which is suitable for laboratory chlorination or bromination, respectively. Aromatic compounds more reactive than alkylbenzenes can be chlorinated or brominated without additional catalyst. Alkenes and alkynes give the corresponding vicinal dihaloalkanes and vinyl halides. All reactions complete within two hours under mild condition (25-60 °C) with excellent to moderate yields.
- Liu, Lilian Kao,Lin, Ching-Shan
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- New applications of tungsten hexachloride (WCl6) in organic synthesis. Halo-de-hydroxylation and dihalo-de-oxo-bisubstitution reactions
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Tungsten hexachloride (WCl6) has been used for the halo-de-hydroxylation and dihalo-de-oxo-bisubstitution reactions of benzylic alcohols, benzaldehydes, acyloins, and epoxides to their chlorides, gem-dichlorides, vic-trichlorides, and vic-dichlorides respectively.
- Firouzabadi, Habib,Shiriny, Farhad
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p. 14929 - 14936
(2007/10/03)
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- A convenient synthesis of triaryl and trialkyl phosphine dichlorides by oxidation of tertiary phosphines with bis(trichloromethyl) carbonate(triphosgene)
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Tertiary phosphines are quantitatively oxidised by 1/3 of an equivalent of triphosgene to the corresponding P(V)dihalides. This reaction provides an excellent preparation of Ph3PCl2.
- Wells
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p. 1715 - 1719
(2007/10/02)
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- Controlling the reactivity of permanganate anion. Novel, stereospecific, dichlorination of olefins
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Potassium permanganate reacts with oxalyl chloride to form a chlorine-containing manganese catalyst, of yet unknown structure, that stereospecifically trans-dichlorinates olefins.
- Marko,Richardson
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p. 1831 - 1834
(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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- OXIDATIVE ADDITION OF ANIONS TO ALKENES BY THE ACTION OF COMPOUNDS OF TETRAVALENT LEAD IN THE PRESENCE OF CHLORIDE ION IN AN ACIDIC MEDIUM
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In the reaction of alkenes (cyclohexene, 1-hexene, styrene) with compounds of tetravalent lead in various acids (trifluoroacetic, acetic, methanesulfonic, perchloric) in the presence of metal chlorides the joint addition of the chloride anion and the anion of the respective acids to the alkenes takes place with a high degree of selectivity, leading to the formation of vicinal bifunctional derivatives of alkanes.The effectiveness of the addition of the anions of the acids to the alkenes under the given conditions varies directly with the strength of the acid and inversely with the nucleophilicity and the basicity of its anion.A new convenient method is proposed for the oxidative chlorofluorination of cyclohexene in aqueous hydrofluoric acid.
- Serguchev, Yu. A.,Gutsulyak, R. B.
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p. 1784 - 1790
(2007/10/02)
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- METHOXYCHLORINATION AND DIMETHOXYLATION OF ALKENES. THE REACTIONS OF SUBSTITUTED STYRENES WITH PHENYLSELENENYL CHLORIDE IN METHANOL
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The addition of PhSeCl to α- and β-substituted styrenes in methanol is regio- and stereospecific and affords the products of methoxyselenenylation.These compounds further react with PhSeCl to give the deselenenylation products.In the case of α-substituted styrenes, 1-methoxy, 2-chloroalkanes are produced, whereas with β-substituted styrenes the major reaction products are the 1,2-dimethoxyalkanes and the 2,2-dimethoxyalkanes in which phenyl migration has occured.It is shown that these reactions proceed through the intermediate formation of the alkyl phenylselenium dichlorides, PhCR(OMe)CHR1SeCl2Ph, which evolve with different mechanisms depending on the structure of the starting alkenes.
- Tiecco, Marcello,Testaferri, Lorenzo,Tingoli, Marco,Chianelli, Donatella,Bartoli, Donatella
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p. 2261 - 2272
(2007/10/02)
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- Reaction of Benzeneseleninyl Chloride with Olefins in the Presence of a Lewis Acid. A Novel One Step Vinylic Chlorination
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In the presence of aluminum chloride benzeneseleninyl chloride was found to be an exellent vinylic chlorinating reagent of olefins under mild conditions.However, such olefins as styrene, trans-stilbene, and trans-1-phenylpropene afforded dichloro adducts under similar conditions.A plausible reaction mechanism involving positive chlorine intermediate is proposed.
- Kamigata, Nobumasa,Satoh, Takeshi,Yoshida, Masato
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p. 449 - 454
(2007/10/02)
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- AN EFFECTIVE CHLORINATING AGENT BENZYLTRIMETHYLAMMONIUM TETRACHLOROIODATE, BENZYLIC CHLORINATION OF ALKYLAROMATIC COMPOUNDS
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The reaction of alkylaromatic compounds with benzyltrimethylammonium tetrachloroiodate in carbon tetrachloride in the presence of AIBN under reflux for several hours gave α-chloro-substituted compounds in fairly good yields.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Moriwaki, Masayuki,Tanaka, Toshio,Fujisaki, Shizuo
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p. 5783 - 5786
(2007/10/02)
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- THE CIS CHLORINATION OF ALKENES USING SELENIUM REAGENTS
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The phenylselenenyl chloride adduct from alkenes can be oxidised and the seleno moiety can be displaced by chloride to give high yields of dichlorides with cis geometry.
- Morella, Angelo M.,Ward, A. David
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p. 1197 - 1200
(2007/10/02)
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