- HALOGENODETELLURATION OF ARYLTELLURIUM(IV) COMPOUNDS
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Some aryltellurium(IV) compounds react with iodine and bromine to give the corresponding aryl halides in good to moderate yields (iodo- and bromodetelluration).The addition of ammonium, cesium or potassium fluoride, antimony(V) chloride, and mercury(II) chloride accelerates the reaction in some cases.Compared to these halogenodetellurations, chlorodetelluration and cyanodetelluration of these compounds were very sluggish when various chlorinating agents and metal cyanides were used under several reaction conditions.
- Uemura, Sakae,Fukuzawa, Shin-Ichi,Wakasugi, Mikio,Okano, Masaya
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Read Online
- Characterization of Key Aroma Compounds in Raw and Thermally Processed Prawns and Thermally Processed Lobsters by Application of Aroma Extract Dilution Analysis
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Application of aroma extract dilution analysis (AEDA) to an aroma distillate of blanched prawn meat (Litopenaeus vannamei) (BPM) revealed 40 odorants in the flavor dilution (FD) factor range from 4 to 1024. The highest FD factors were assigned to 2-acetyl-1-pyrroline, 3-(methylthio)propanal, (Z)-1,5-octadien-3-one, trans-4,5-epoxy-(E)-2-decenal, (E)-3-heptenoic acid, and 2-aminoacetophenone. To understand the influence of different processing conditions on odorant formation, fried prawn meat was investigated by means of AEDA in the same way, revealing 31 odorants with FD factors between 4 and 2048. Also, the highest FD factors were determined for 2-acetyl-1-pyrroline, 3-(methylthio)propanal, and (Z)-1,5-octadien-3-one, followed by 4-hydroxy-2,5-dimethyl-3(2H)-furanone, (E)-3-heptenoic acid, and 2-aminoacetophenone. As a source of the typical marine, sea breeze-like odor attribute of the seafood, 2,4,6-tribromoanisole was identified in raw prawn meat as one of the contributors. Additionally, the aroma of blanched prawn meat was compared to that of blanched Norway and American lobster meat, respectively (Nephrops norvegicus and Homarus americanus). Identification experiments revealed the same set of odorants, however, with differing FD factors. In particular, 3-hydroxy-4,5-dimethyl-2(5H)-furanone was found as the key aroma compound in blanched Norway lobster, whereas American lobster contained 3-methylindole with a high FD factor.
- Mall, Veronika,Schieberle, Peter
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- Eco-Friendly Methodology for the Formation of Aromatic Carbon–Heteroatom Bonds by Using Green Ionic Liquids
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A new sustainable method is reported for the formation of aromatic carbon–heteroatom bonds under solvent-free and mild conditions (no co-oxidant, no strong acid and no toxic reagents) by using a new type of green ionic liquid. The bromination of methoxy arenes was chosen as a model reaction. The reaction methodology is based on only using natural sodium bromine, which is transformed into an electrophilic brominating reagent within an ionic liquid, easily prepared from the melted salt FeCl3 hexahydrate. Bromination reactions with this in-situ-generated reagent gave good yields and excellent regioselectivity under simple and environmentally friendly conditions. To understand the unusual bromine polarity reversal of sodium bromine without any strong oxidant, the molecular structure of the reaction medium was characterised by Raman and direct infusion electrospray ionisation mass spectroscopy (ESI-MS). An extensive computational investigation using density functional theory methods was performed to describe a mechanism that suggests indirect oxidation of Br? through new iron adducts. The versatility of the methodology was successively applied to nitration and thiocyanation of methoxy arenes using KNO3 and KSCN in melted hexahydrated FeCl3.
- Richards, Kenza,Petit, Eddy,Legrand, Yves-Marie,Grison, Claude
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supporting information
p. 809 - 814
(2020/11/30)
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- Stepwise mechanism for the bromination of arenes by a hypervalent iodine reagent
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A mild, metal-free bromination method of arenes has been developed using the combination of bis(trifluoroacetoxy)iodobencene and trimethylsilyl bromide. In situ-formed dibromo(phenyl)-λ3-iodane (PhIBr2) is proposed as the reactive intermediate. This methodology using PIFA/TMSBr has been applied with success to a great number of substrates (25 examples). The treatment of mono-substituted activated arenes led to para-brominated products (2u-z) in excellent 83-96% yields. Density functional theory calculations indicate a stepwise mechanism involving a double bromine addition followed by a type II dyotropic reaction with concomitant re-aromatization of the six-membered ring.
- Arrieta, Ana,Cossío, Fernando P.,Granados, Albert,Shafir, Alexandr,Vallribera, Adelina
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p. 2142 - 2150
(2020/03/11)
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- One-pot synthesis of 4-aryl-2-aminothiazoles from styrenes and thioureas promoted by tribromoisocyanuric acid
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A simple and efficient one-pot protocol has been developed for the conversion of styrenes into 4-aryl-2-aminothiazoles using readily available starting materials. Tribromoisocyanuric acid was successfully used for the co-bromination and oxidation of styrenes to give phenacyl bromides, which in the presence of thioureas produced the corresponding 4-aryl-2-aminothiazoles in 48–70% yield. The protocol involves three reactions in one process: a tandem (formation of phenacyl bromides from styrenes) followed by a telescoped (conversion to thiazole) reaction.
- de Andrade, Vitor S.C.,de Mattos, Marcio C.S.
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supporting information
(2020/07/03)
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- Aromatic Halogenation Using N-Halosuccinimide and PhSSiMe3 or PhSSPh
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We developed a mild aromatic halogenation reaction using a combination of N-halosuccinimide and PhSSiMe3 or PhSSPh. Less reactive aromatic compounds, such as methyl 4-methoxybenzoate, were brominated with PhSSiMe3 or PhSSPh and N-bromosuccinimide in high yields. No reaction was observed in the absence of PhSSiMe3 or PhSSPh. This method is also applicable to chlorination reactions using N-chlorosuccinimide and PhSSPh.
- Hirose, Yuuka,Yamazaki, Mirai,Nogata, Misa,Nakamura, Akira,Maegawa, Tomohiro
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p. 7405 - 7410
(2019/06/14)
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- Transition-metal-free decarboxylative bromination of aromatic carboxylic acids
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Methods for the conversion of aliphatic acids to alkyl halides have progressed significantly over the past century, however, the analogous decarboxylative bromination of aromatic acids has remained a longstanding challenge. The development of efficient methods for the synthesis of aryl bromides is of great importance as they are versatile reagents in synthesis and are present in many functional molecules. Herein we report a transition metal-free decarboxylative bromination of aromatic acids. The reaction is applicable to many electron-rich aromatic and heteroaromatic acids which have previously proved poor substrates for Hunsdiecker-type reactions. In addition, our preliminary mechanistic study suggests that radical intermediates are not involved in this reaction, which is in contrast to classical Hunsdiecker-type reactivity. Overall, the process demonstrates a useful method for producing valuable reagents from inexpensive and abundant starting materials.
- Quibell, Jacob M.,Perry, Gregory J. P.,Cannas, Diego M.,Larrosa, Igor
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p. 3860 - 3865
(2018/04/26)
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- Dehydroxymethyl Bromination of Alkoxybenzyl Alcohols by Using a Hypervalent Iodine Reagent and Lithium Bromide
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We describe the dehydroxymethylbromination of alkoxybenzyl alcohol by using a hypervalent iodine reagent and lithium bromide in F 3 CCH 2 OH at room temperature. Selective monobromination or dibromination was possible by adjusting the molar ratios of hypervalent iodine reagent and lithium bromide.
- Shibata, Ayako,Kitamoto, Sara,Fujimura, Kazuma,Hirose, Yuuka,Hamamoto, Hiromi,Nakamura, Akira,Miki, Yasuyoshi,Maegawa, Tomohiro
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supporting information
p. 2275 - 2278
(2018/10/20)
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- Zwitterionic-Salt-Catalyzed Site-Selective Monobromination of Arenes
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A zwitterionic-salt-catalyzed electrophilic monobromination of arenes with high regioselectivity has been developed. Under mild reaction conditions, a wide range of monobrominated aromatic compounds can be obtained in excellent yields. The reaction can be operated using an extremely low catalyst loading (0.05 mol %) with the inexpensive brominating agent N-bromosuccinimide. The versatility of this catalytic protocol has been demonstrated by the scale-up reaction with a 0.01 mol % catalyst loading to provide the selectively halogenated compound in quantitative yield.
- Xiong, Xiaodong,Tan, Fei,Yeung, Ying-Yeung
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p. 4243 - 4246
(2017/08/23)
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- Transition-Metal-Free Decarboxylative Iodination: New Routes for Decarboxylative Oxidative Cross-Couplings
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Constructing products of high synthetic value from inexpensive and abundant starting materials is of great importance. Aryl iodides are essential building blocks for the synthesis of functional molecules, and efficient methods for their synthesis from chemical feedstocks are highly sought after. Here we report a low-cost decarboxylative iodination that occurs simply from readily available benzoic acids and I2. The reaction is scalable and the scope and robustness of the reaction is thoroughly examined. Mechanistic studies suggest that this reaction does not proceed via a radical mechanism, which is in contrast to classical Hunsdiecker-type decarboxylative halogenations. In addition, DFT studies allow comparisons to be made between our procedure and current transition-metal-catalyzed decarboxylations. The utility of this procedure is demonstrated in its application to oxidative cross-couplings of aromatics via decarboxylative/C-H or double decarboxylative activations that use I2 as the terminal oxidant. This strategy allows the preparation of biaryls previously inaccessible via decarboxylative methods and holds other advantages over existing decarboxylative oxidative couplings, as stoichiometric transition metals are avoided.
- Perry, Gregory J. P.,Quibell, Jacob M.,Panigrahi, Adyasha,Larrosa, Igor
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supporting information
p. 11527 - 11536
(2017/08/30)
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- Mechanistic study on iodine-catalyzed aromatic bromination of aryl ethers by N-Bromosuccinimide
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Although iodine-catalyzed reaction has rapid advances in recent years, examples on iodine-catalyzed bromination are rare and the mechanism of these reactions remains unclear. Herein, we reported an I2-catalyzed aromatic bromination of aryl ethers by NBS and presented the details of the mechanistic study including kinetic study and the study of kinetic isotope effects. The study revealed that the reaction was actually catalyzed by IBr formed in the induction period, and the rate-determining step was the HBr-elimination of the Wheland intermediate assisted by IBr.
- Pramanick, Pranab Kumar,Hou, Zhen-Lin,Yao, Bo
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p. 7105 - 7114
(2017/11/27)
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- A new and versatile one-pot strategy to synthesize alpha-bromoketones from secondary alcohols using ammonium bromide and oxone
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A new, efficient and green protocol for the one-pot synthesis of α-bromoketones from secondary alcohols using cheap, air stable and non-toxic reagents such as NH4Br and oxone has been developed. This reaction proceeds via two consecutive steps such as oxidation of secondary alcohols and oxidative bromination of in situ generated ketones.
- Rammurthy, Banothu,Swamy, Peraka,Naresh, Mameda,Srujana, Kodumuri,Durgaiah, Chevella,Krishna Sai, Gajula,Narender, Nama
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p. 3710 - 3714
(2017/07/12)
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- Conversion of thiols into sulfonyl halogenides under aerobic and metal-free conditions
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An environmentally benign, metal-free synthesis of sulfonyl chlorides and bromides from thiols in the presence of ammonium nitrate, an aqueous solution of HCl and HBr and oxygen as a terminal oxidant was developed. The reactivity of various substituted thiophenols, benzylic-, aliphatic- and heteroaromatic thiols was examined. Ammonium nitrate served as a source of nitrogen oxides (NO/NO2), which are the crucial players in a redox-catalytic cycle. Sulfonyl chlorides and bromides were isolated without extraction and "filtered" over a short pad of silica gel; the use of solvents was greatly reduced in comparison with traditional isolation and purification. A "one-pot" protocol for the conversion of thiol into sulfonamide is also demonstrated. Scale-up experiments on the preparation of sulfonyl chloride and bromide are shown. A possible reaction pathway is discussed.
- Jereb, Marjan,Hribernik, Luka
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supporting information
p. 2286 - 2295
(2017/07/24)
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- Bromination of Anisoles Using N-Bromophthalimide: A Synthetic and Kinetic Approach
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N-Bromophthalimide (NBP)-triggered bromination of aromatic compounds has been studied in the presence of aqueous acetic acid. Reaction Kinetics indicated first order in [NBP] and zero order in [Anisole]. The reactions afforded very good yields of corresponding bromo derivatives under kinetic conditions. The mechanism of the reaction is explained through the formation of acetyl hypobromite due to the interaction of NBP and acetic acid, which in turn reacts with anisole to afford a bromo derivative of anisole.
- Anjaiah,Kumar, M. Satish,Srinivas,Rajanna
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- Electrophilic aryl-halogenation using N-halosuccinimides under ball-milling
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We report here a methodology of chemo- and regio-selective aryl bromination and iodination using respective N-halosuccinimides at room temperature in the absence of any solvents, catalyst/additives under ball-milling condition. However, for chlorination ceric ammonium nitrate was used as additive. The coupled product succinimide, produced from the reactions, was recycled via regeneration of NBS. This methodology works with the electron-donor substituted or unsubstituted arenes.
- Bose, Anima,Mal, Prasenjit
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supporting information
p. 2154 - 2156
(2015/03/18)
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- Sono-bromination of aromatic compounds based on the ultrasonic advanced oxidation processes
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A novel, mild "sono-halogenation" of various aromatic compounds with potassium halide was investigated under ultrasound in a biphasic carbon tetrachloride/water medium. The feasibility study was first undertaken with the potassium bromide and then extended to chloride and iodide analogues. This methodology could be considered as a new expansion of the ultrasonic advanced oxidation processes (UAOPs) into a synthetic aspect as the developed methodology is linked to the sonolytic disappearance of carbon tetrachloride. Advantages of the present method are not only that the manipulation of the bromination is simple and green, but also that the halogenating agents used are readily available, inexpensive, and easy-handling.
- Fujita, Mitsue,Lévêque, Jean-Marc,Komatsu, Naoki,Kimura, Takahide
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p. 247 - 251
(2015/06/08)
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- Electrophilic aryl-halogenation using N-halosuccinimides under ball-milling
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We report here a methodology of chemo- and regio-selective aryl bromination and iodination using respective N-halosuccinimides at room temperature in the absence of any solvents, catalyst/additives under ball-milling condition. However, for chlorination ceric ammonium nitrate was used as additive. The coupled product succinimide, produced from the reactions, was recycled via regeneration of NBS. This methodology works with the electron-donor substituted or unsubstituted arenes.
- Bose, Anima,Mal, Prasenjit
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supporting information
p. 2154 - 2156
(2014/04/03)
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- Bromination of arenes using I2O5-KBr in water
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An efficient and environmentally benign bromination of various aromatic compounds using aN aqueous I2O5-KBr system at room temperature has been developed in this work. A series of aromatic compounds such as acetophenones, benzaldehydes, benzoic acids, anilines, amides, and aminopyridine have been successfully brominated in excellent regioselectivities and good yields under the typical reaction conditions. The features of KBr as brominating reagent, water as solvent, and mild conditions make this system an attractive synthetic procedure. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.]
- Hou, Jieping,Li, Zejiang,Jia, Xiao-Dong,Liu, Zhong-Quan
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supporting information
p. 181 - 187
(2013/12/04)
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- Practical and metal-free electrophilic aromatic halogenation by interhalogen compounds generated in situ from N-halosuccinimide and catalytic TMSCL
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Halomonochloride compounds (ClCl, BrCl, ICl) generated in situ from N-halosuccinimide and catalytic chlorotrimethylsilane (TMSCl, 0.1 equiv) can efficiently halogenate aromatic compounds to give halogenated products in good to excellent yields and selectivities. The reaction can be carried out at room temperature or at lower temperatures, requires only one hour, is practical to apply to a wide range of substrates, and provides a simple access to a variety of haloarene compounds. Georg Thieme Verlag Stuttgart New York.
- Maibunkaew, Tapanee,Thongsornkleeb, Charnsak,Tummatorn, Jumreang,Bunrit, Anon,Ruchirawat, Somsak
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supporting information
p. 1769 - 1775
(2014/08/05)
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- Base-promoted protodeboronation of 2,6-disubstituted arylboronic acids
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Facile based promoted deboronation of electron-deficient arylboronate esters was observed for arylboronates containing two ortho electron-withdrawing group (EWG) substituents. Among 30 representative boronates, only the diortho-substituted species underwe
- Lozada, Jerome,Liu, Zhibo,Perrin, David M.
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supporting information
p. 5365 - 5368
(2014/06/23)
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- Bronsted acidic ionic liquid accelerated halogenation of organic compounds with N-halosuccinimides (NXS)
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The Bronsted-Acidic ionic liquid 1-methyl-3-(4-sulfobutyl) imidazolium triflate [BMIM(SO3H)][OTf] was demonstrated to act efficiently as solvent and catalyst for the halogenation of activated organic compounds with N-halosuccinimides (NXS) under mild conditions with short reaction times. Methyl aryl ketones were converted into a-halo and a,a-dihaloketones, depending on the quantity of NXS used. Ketones with activated aromatic rings were selectively halogenated, however in some cases mixtures of a-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO3H)][OTf] ionic liquid (IL-A) was successfully reused eight times in a representative monohalogenation reaction with no noticeable decrease in efficiency. An effective halogenation scale-up in this IL is also presented. The reactivity trend and the observed chemo- and regioselectiivities point to an ET process in these IL-promoted halofunctionalization reactions.
- Vrazic, Dejan,Jereb, Marjan,Laali, Kenneth K.,Stavber, Stojan
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- Metal and H2O2 free aerobic oxidative aromatic halogenation with [RNH3+] [NO3-]/HX and [BMIM(SO3H)][NO3)x(X)y] (X = Br, Cl) as multifunctional ionic liquids
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Novel multifunctional ionic liquids (ILs) are generated by addition of HBr or HCl to alkylammonium nitrates ([RNH3+] [NO 3-]) and to 3-methyl-1-(butyl-4-sulfonyl)imidazolium nitrate ([BMIM(SO3H)][NO3]). The resulting [RNH 3+] [NO3-]/HX and mono (3-methyl-1-(butyl-4-sulfonyl)imidazolium) monohalogenide mononitrate ([BMIM(SO3H)][NO3)x(X)y] (X = Br, Cl)) systems act as solvent and promoter for aerobic oxidative halogenation of arenes under mild conditions in high yields that can be repeated over several cycles.
- Prebil, Rok,Laali, Kenneth K.,Stavber, Stojan
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supporting information
p. 2108 - 2111
(2013/06/05)
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- Brominated methanes as photoresponsive molecular storage of elemental Br2
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The photochemical generation of elemental Br2 from brominated methanes is reported. Br2 was generated by the vaporization of carbon oxides and HBr through oxidative photodecomposition of brominated methanes under a 20 W low-pressure mercury lamp, wherein the amount and situations of Br2 generation were photochemically controllable. Liquid CH 2Br2 can be used not only as an organic solvent but also for the photoresponsive molecular storage of Br2, which is of great technical benefit in a variety of organic syntheses and in materials science. By taking advantage of the in situ generation of Br2 from the organic solvent itself, many organobromine compounds were synthesized in high practical yields with or without the addition of a catalyst. Herein, Br2 that was generated by the photodecomposition of CH2Br2 retained its reactivity in solution to undergo essentially the same reactions as those that were carried out with solutions of Br2 dissolved in CH 2Br2 that were prepared without photoirradiation. Furthermore, HBr, which was generated during the course of the photodecomposition of CH2Br2, was also available for the substitution of the OH group for the Br group and for the preparation of the HBr salts of amines. Furthermore, the photochemical generation of Br2 from CH2Br2 was available for the area-selective photochemical bleaching of natural colored plants, such as red rose petals, wherein Br2 that was generated photochemically from CH 2Br2 was painted onto the petal to cause radical oxidations of the chromophoric anthocyanin molecules. The generation of Br 2 from brominated methanes occurred upon photoirradiation under O2. The solutions that contained elemental Br2 were useful for the synthesis of organobromine compounds and the macroscopic photochemical bleaching of colored plants. Copyright
- Kawakami, Kazumitsu,Tsuda, Akihiko
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p. 2240 - 2252
(2012/11/06)
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- Hypervalent iodine(III)-LiX combination in fluoroalcohol solvent for aromatic halogenation of electron-rich arenecarboxylic acids
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The novel reagent system, PhI(OAc)2-LiX combination in fluoroalcohol solvents, was found to be effective for halodecarboxylation of electron-rich arenecarboxylic acids. The method provided an efficient route to halogenated phenol ether derivatives. Georg Thieme Verlag Stuttgart ? New York.
- Hamamoto, Hiromi,Hattori, Sho,Takemaru, Kaori,Miki, Yasuyoshi
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scheme or table
p. 1563 - 1566
(2011/08/03)
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- PROCESS FOR THE PREPARATION OF 4-BROMOPHENYL DERIVATIVES
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Disclosed is a process for the preparation of a mixture of 4-bromophenyl derivatives (compound of formula (2)) and 2,4-dibromophenyl derivatives (compound of formula (3)) comprising the steps of [1] reacting in a two-phase (liquid-liquid) system a bromide containing source with a phenyl derivative (formula (1)) in the presence of an excess of an oxidizing agent, an acid, and optionally a catalyst selected from vanadium pentoxide and ammonium heptamolybdate forming 4-bromo- (compound of formula (2)) and 2,4-dibromo derivatives (compound of formula (3)) and as intermediate product the 2-bromo derivative (compound of formula (4)) which reacts in step [2] to the 2,4-dibromo derivative (formula (3)) according to the following reaction scheme 2 wherein R1 is hydroxy; C1-C5alkoxy; or -NR2R3; and R2 and R3 independently from each other are hydrogen; or C1-C5alkyl.
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Page/Page column 9
(2010/04/03)
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- Regioselective synthesis of phenols and halophenols from arylboronie acids using solid poly(N-vinylpyrrolidone)/hydrogen peroxide and poly(4-vinylpyridine) /hydrogen peroxide complexes
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Solid hydrogen peroxide complexes based on poly(N-vinylpyrrolidone) and poly(4-vinylpyridine) were prepared and used as solid hydroxylating reagents. These solid hydrogen peroxide equivalents are found to be much safer, convenient and efficient reagent systems for the ipso-hydroxylation of arylboronie acids to the corresponding phenols in high yields at a faster rate. The versatility of the reagents has been further expanded for the one-pot synthesis of halophenols. Density functional theory calculations were carried out on hydrogen peroxide complexes of N-ethylpyrrolidone and 4-ethylpyridine as models to get a better understanding of structure and behavior of hydrogen peroxide complexes of the polymers poly(N-vinylpyrrolidone) and poly(4-vinylpyridine) compared to aqueous hydrogen peroxide.
- Prakash, G. K. Surya,Chacko, Sujith,Panja, Chiradeep,Thomas, Tisa Elizabeth,Gurung, Laxman,Rasul, Golam,Mathew, Thomas,Olah, George A.
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body text
p. 1567 - 1574
(2011/02/25)
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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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- Stereoselective bromination reactions using tridecylmethylphosphonium tribromide in a "stacked" reactor
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(Chemical Equation Presented) A new reagent, tridecylmethylphosphonium tribromide, and new procedures for bromination reactions of unsaturated substrates (including one that allows several substrates to be reacted in sequence) are described. The procedures exploit the diffusion of components and the densities and immiscibilities of layers, including a fluorous "spacer" layer, within a reaction vessel. The stereoselectivities achieved in the reactions are superior in some cases to those found with other brominating reagents.
- Ma, Kefeng,Li, Shaw,Weiss, Richard G.
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supporting information; experimental part
p. 4155 - 4158
(2009/06/06)
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- Regioselective aromatic electrophilic bromination with dioxane dibromide under solvent-free conditions
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Highly regioselective ring bromination of aromatic compounds has been accomplished with high yields and good purity using dioxane dibromide (DD) under solvent-free conditions. Notable features of this methodology include operational simplicity, rapid reactions, excellent control over the degree of bromination, and tolerance of various functional groups during the reaction. Copyright Taylor & Francis Group, LLC.
- Chaudhuri, Subrata Kumar,Roy, Sanchita,Saha,Bhar, Sanjay
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p. 581 - 585
(2007/10/03)
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- An efficient vanadium-catalyzed bromination reaction
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An efficient catalytic oxidative bromination of arenes, alkenes, and alkynes in aqueous media was achieved under relatively mild conditions by using NH4VO3 catalyst combined with H2O2, HBr, and KBr. Dodecyltrimethylammonium bromide was found to serve as an efficient surfactant to facilitate the NH4VO3-catalyzed bromination in aqueous media.
- Moriuchi, Toshiyuki,Yamaguchi, Mitsuaki,Kikushima, Kotaro,Hirao, Toshikazu
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p. 2667 - 2670
(2008/02/03)
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- New oxabispidine compounds for the treatment of cardiac arrhythmias
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There is provided compounds of formula I, wherein R1, R2, R3, R41 to R46, X, Y and Z have meanings given in the description, which compounds are useful in the prophylaxis and in the treatment of arrhythmias, in particular atrial and ventricular arrhythmias.
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Page/Page column 61-62
(2008/06/13)
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- Facile Synthesis of 2-Bromo-3-fluorobenzonitrile: An Application and Study of the Halodeboronation of Aryl Boronic Acids
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A scaleable synthesis of 2-bromo-3-fluorobenzonitrile via the NaOMe-catalyzed bromodeboronation of 2-cyano-6-fluorophenylboronic acid was developed. The generality of this transformation was demonstrated through the halodeboronation of a series of aryl boronic acids. Both aryl bromides and aryl chlorides were formed in good to excellent yields when the corresponding aryl boronic acid was treated with 1,3-dihalo-5,5-dimethylhydantoin and 5 mol % NaOMe.
- Szumigala Jr., Ronald H.,Devine, Paul N.,Gauthier Jr., Donald R.,Volante
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p. 566 - 569
(2007/10/03)
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- Novel bromination method for anilines and anisoles using NH 4Br/H2O2 in CH3COOH
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A simple, efficient, regioselective, environmentally safe, and economical method for the oxybromination of anilines and anisoles without catalyst is reported. The electrophilic substitution of bromine generated in situ from ammonium bromide as a bromine source and hydrogen peroxide as an oxidant for the first time.
- Krishna Mohan,Narender,Srinivasu,Kulkarni,Raghavan
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p. 2143 - 2152
(2007/10/03)
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- Effect of cyclodextrins on electrophilic aromatic bromination in aqueous solution
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Cyclodextrins act as molecular reactors to change the ratios of the products of reactions of anisole, acetanilide, 3-methylanisole, and 3-methylacetanilide with pyridinium dichlorobromate. With anisole and acetanilide, bromination at the para position is favoured over ortho substitution, and the effect is greatest with α-cyclodextrin. In the reactions of the methylanisole and methylacetanilide, the cyclodextrins afford higher yields of monobrominated products and less of the di- and tribromides, and β-cyclodextrin has the greatest effect. These outcomes can be attributed to inclusion of the substrates within the cyclodextrins restricting access of the reagent adjacent to the methoxy and acetamido groups. The yields of 4-bromoanisole, 4-bromoacetanilide, 4-bromo-3-methylanisole, and 4-bromo-3-methylacetanilide are thus increased from 73 to 94, 55 to 98, 37 to 86, and 39 to 72%, respectively. Perhaps more significantly, the quantities of the corresponding by-products are substantially reduced, from 27 to 6, 45 to 2, 63 to 14, and 61 to 28%. Since the reactions occur readily in water at ambient temperature, the cyclodextrins make them very efficient.
- Dumanski, Paul G.,Easton, Christopher J.,Lincoln, Stephen F.,Simpson, Jamie S.
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p. 1107 - 1111
(2007/10/03)
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- Bromodecarbonylation and bromodecarboxylation of electron-rich benzaldehydes and benzoic acids with oxone and sodium bromide
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Benzaldehydes and benzoic acids bearing ortho- and paraelectron donating substituents having unshared electron-pair have undergone bromodecarbonylation or bromodecarboxylation on treatment with sodium bromide in the presence of Oxone in aqueous methanol.
- Koo, Bon-Suk,Kim, Eun-Hoo,Lee, Kee-Jung
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p. 2275 - 2286
(2007/10/03)
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- Oxidation of benzyl alcohols with Oxone and sodium bromide
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Reaction of benzyl alcohols with Oxone and sodium bromide in aqueous acetonitrile gave the corresponding benzaldehydes in excellent yields. However, electron-rich benzyl alcohols afforded ring bromination products via bromodecarbonylation of the resulting benzaldehydes.
- Koo, Bon-Suk,Lee, Chang Keun,Lee, Kee-Jung
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p. 2115 - 2123
(2007/10/03)
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- Novel process for generating useful electrophiles from common anions using Selectfluor fluorination agent
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In the present work, the electrophile equivalents C1+, Br+, SCN+, and NO2+ are generated from their respective sodium, potassium, and in some cases ammonium salts (M+X-) by reaction with Selectfluor electrophilic fluorination agent in acetonitrile solution at room temperature. These generated electrophilic species subsequently react in situ with a variety of aromatic substrates containing one or more substituent groups including H, F, C1, CH3, COOH, C(O)CH3, NO2, and OR′ and NR′R″ where R′ and R″ are H or CH3. The resulting substitution products are, in most cases, isolable as pure compounds in high yield. Variations in the process include the use of other anions, electrophilic fluorination agents, and solvents.
- Syvret, Robert G.,Butt, Kathleen M.,Nguyen, Tung P.,Bulleck, Victoria L.,Rieth, Ryan D.
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p. 4487 - 4493
(2007/10/03)
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- A simple and practical halogenation of activated arenes using potassium halide and oxone in water-acetonitrile medium
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A simple and practical halogenation of activated arenes using a reagent combination of potassium halide and oxone in water-acetonitrile medium is presented. The halogenated products were obtained with good yields and in high purity.
- Tamhankar,Desai,Mane,Wadgaonkar,Bedekar
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p. 2021 - 2027
(2007/10/03)
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- Vanadium-catalysed oxidative bromination using dilute mineral acids and hydrogen peroxide: An option for recycling waste acid streams
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Vanadium pentoxide, V2O5, catalyses the two-electron oxidation of Br- to Br+, using aqueous hydrogen peroxide under dilute acidic conditions. In this system, kinetic studies show that HBr can be replaced with a combination of an alkali bromide salt (NaBr, KBr) and a dilute mineral acid (e.g., HCl, H2SO4, HNO3, H3PO4). The salt/acid/peroxide system may be used for in situ or ex situ oxidative bromination, e.g. of various aromatic compounds. The application of the above concept towards the recycling of industrial acid waste is discussed. The cost effectiveness, E factors, and hazard factors for several bromination and oxidative bromination reagent systems are compared.
- Rothenberg, Gadi,Clark, James H.
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p. 270 - 274
(2013/09/07)
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- Environment friendly regiospecific bromination of aromatic ethers by N- bromosuccinimide in presence of montmorillonite
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Reaction of methoxybenzenes and naphthalenes with N-bromosuccinimide in presence of montmorillonite clay (K10) affords excellent yields of regiospecifically brominated products under mild conditions in the absence of solvent.
- Perumal,Vijayabaskar,Gomathi,Selvaraj
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p. 603 - 604
(2007/10/03)
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- Generation of interhalogen fluorides under mild conditions: A comparison of sluggish and reactive interhalogen fluorides
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Interhalogen fluorides (XF; X = I, Br, or Cl) generated from xenon difluoride (XeF2) or triethylamine trihydrofluoride (TREAT HF) with iodine (I2), N-halosuccinimides (NXS; X = I, Br, or Cl), or alkylhypohalites (ROX; R = CH3 or t-Bu, X = Br or Cl) with alkenes and aromatics are reported. A comparison of the above reactions with other methods reported in the literature to generate interhalogen fluorides is made. Interhalogens generated from direct action of elemental fluorine (F2) or XF3 (X = I, Br, or Cl) with chlorine (Cl2), bromine (Br2), or iodine (I2) give a species that can react with electron-deficient alkenes or aromatics. These reagents are too reactive for electron-rich substrates. Interhalogen fluorides from reagents like NXS or ROX with XeF2 or amine HF are much less reactive and give good yields with electron-rich akenes or aromatics.
- Shellhamer, Dale F.,Horney, Mark J.,Pettus, Benjamin J.,Pettus, Tobiah L.,Stringer, Joy Merry,Heasley, Victor L.,Syvret, Robert G.,Dobrolsky Jr., John M.
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p. 1094 - 1098
(2007/10/03)
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- Reactivity and synthetic utility of 1-(arenesulfonyloxy) benziodoxolones
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The reactivity and synthetic use of 1-(arenesulfonyloxy)benziodoxolones were studied. In the presence of iodine, 1-(arenesulfonyloxy)benziodoxolones iodinated various aromatics to give iodoarenes in moderate to good yields. In particular, 1-(p-chlorobenzenesulfonyloxy)benziodoxolone showed the best reactivity. Using a halide salt such as lithium bromide or lithium chloride instead of iodine, the corresponding aryl bromides and chlorides were also obtained in good yields. In the absence of aromatics, 1- (arenesulfonyloxy)benziodoxolones gave rise to desulfonyloxyiodination reactions to give the corresponding aryl iodides via electrophilic ipso substitution on the aromatic rings. Furthermore, the l-(p- toluenesulfonyloxy)benziodoxolone/iodine system iodotosyloxylated alkynes in good yields. These reactions proceeded via the formation of arenesulfonyl hypoiodites.
- Muraki, Takahito,Togo, Hideo,Yokoyama, Masataka
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p. 2883 - 2889
(2007/10/03)
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- The Bromination of Phenolic Methyl Ethers with Hydrogen Bromide using Sodium Tungstate and Hydrogen Peroxide as Oxidant
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Sodium tungstate has been found to be an effective catalyst for the nuclear bromination of some aromatic methyl ethers using hydrogen bromide in glacial acetic acid and hydrogen peroxide as the oxidant.
- Bezodis, Paul,Hanson, James R.,Petit, Philippe
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p. 334 - 335
(2007/10/03)
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- Aromatic iodination of activated arenes and heterocycles with lead tetraacetate as the oxidant
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An easy, cheap and fairly quick laboratory method is presented for aromatic iodination of some highly activated arenes and heterocycles with molecular iodine in the presence of either pure lead tetraacetate dissolved in glacial acetic acid, or with the same oxidant but prepared in situ from Pb3O4 dissolved in hot AcOH/Ac2O prior to the iodination. 4-Bromo- and 2,4-dibromoanisoles are obtained from anisole by the respective oxidative bromination.
- Krassowska-Swiebocka,Lulinski,Skulski
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p. 926 - 928
(2007/10/02)
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- Halogenation using Quaternary Ammonium Polyhalides. Part 22. Selective Bromination of Aromatic Ethers with Benzyltrimethylammonium Tribromide
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The reaction of aromatic ethers with a stoicheiometric amount of benzyltrimethylammonium tribromide in dichloromethane-methanol or acetic acid-ZnCl2 under mild conditions gave, selectively, mono-, di-, or tri-bromo-substituted aromatic ethers in quantitative yields.
- Kajigaeshi, Shoji,Moriwaki, Masayuki,Tanaka, Toshio,Fujisaki, Shizuo,Kakinami, Takaaki,Okamoto, Tsuyoshi
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p. 897 - 899
(2007/10/02)
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- ipso Nitration in p-halophenyl ethers
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Addition of nitronium ion ipso to halogen occurs on nitration of the p-haloanisoles in acetic anhydride at -60 deg C.In the cases of p-fluoro- and p-chloro-anisole, addition of the nitronium ion is reversible and only small amounts of ipso products are obtained.With p-bromoanisole nitrodebromination occurs.When p-halophenyl ethers containing a trapping substituent, e.g., 2-(4-chlorophenoxy)-2-methylpropanoic acid, are used as substrates, substantial amounts of the spiro diene with nitro ipso to halogen, e.g., 3,3-dimethyl-8-chloro-8-nitro-1,4-dioxaspirodeca-6,9-dien-2-one, can be isolated.The results demonstrate that extensive ipso attack at the halogen-substituted position is general in the nitration of p-halophenyl ethers.Key words: ipso nitration, ether, diene, p-haloanisole.
- Clewley, Robin G.,Fischer, Alfred,Henderson, George N.
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p. 1472 - 1479
(2007/10/02)
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- POLYBROMINATED AROMATIC COMPOUNDS. IV. METHOXYDEBROMINATION REACTIONS OF POLYBROMOBENZENES IN PYRIDINE
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The rates were measured and the orientation was studied for the methoxydebromination of all polybromobenzenes C6HnBr6-n (n = 0-3) in pyridine at 115 deg C.From comparison of the partial rates of substitution of the bromine atom at various positions of the benzene ring it was found that the activating effect of the bromine atom in relation to the point of nucleophilic attack changes in the order o-Br > m-Br > p-Br, and the directing selectivity of the bromine is low (compared with fluorine in the methoxydefluorination of polyfluorobenzenes) and increases with decrease in the number of bromine atoms in the aromatic ring of the substrate.
- Shishkin, V. N.,Lapin, K. K.,Tanaseichuk, B. S.,Butin, K. P.
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p. 516 - 522
(2007/10/02)
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- POLYBROMINATED AROMATIC COMPOUNDS. III. SYNTHESIS OF BROMINE-SUBSTITUTED ANISOLES
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Reliable methods were developed for the synthesis of di-, tri-, and tetrabromoanisoles, and all the possible individual isomers were synthesized.The structures of the isomers were proved by alternative synthesis and spectral methods (PMR, IR).It was shown that the published data are incorrect in a number of cases; either the final product was assigned the incorrect structure, or the published methods led to mixture of the various isomers.
- Shishkin, V. N.,Tanaseichuk, B. S.,Lapin, K. K.,Ivkina, A. A.,Butin, K. P.
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p. 2357 - 2366
(2007/10/02)
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- 107. Substitution electrophile aromatique dans l'anhydride sulfureux liquide. Etude cinetique de la reaction de bromination d'anisoles monosubstitues. Transmission des effets electroniques et caracteristiques de l'etat de transition
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Reactivity-structure correlations for anisole and eleven of its substituted derivatives established from bromination rate constants in liquid SO2, unlike observations in water, show the reaction to be highly sensitive to substituent effects, (ρ+H2O = -7.1; ρ+SO2 = -10.51).This result is ascribed to the solvation of the methoxy group which decreases the conjugation of para-substituted (ρ+O = -9.70) compared to that of ortho-substituted derivatives (ρ+p = -8.86).The highly solvated transition state lies far from reactants on the reaction coordinate and the positive charge developed in this state is nearly unity.
- Castellonese, Paul,Villa, Pierre
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p. 1068 - 1077
(2007/10/02)
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