- Using NBS as a mild bromination reagent for polyalkoxyaromatic systems
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N-Bromosuccinimide in Methylene Chloride is A Mild Mono- or Dibromination Reagent for Polyalkoxyaromatic Compounds Including Those Which are too Labile to be Brominated with Molecular Bromine.
- Bloomer, James L.,Zheng, Wei
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Read Online
- Direct bromodeboronation of arylboronic acids with CuBr2 in water
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An efficient and practical method has been developed for the preparation of aryl bromides via the direct bromodeboronation of arylboronic acids with CuBr2 in water. This strategy provides several advantages, such as being ligand-free, base-free, high yielding, and functional group tolerant.
- Tang, Yan-Ling,Xia, Xian-Song,Gao, Jin-Chun,Li, Min-Xin,Mao, Ze-Wei
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supporting information
(2021/01/05)
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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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- A silica-gel accelerated [4 + 2] cycloaddition-based biomimetic approach towards the first total synthesis of magterpenoid C
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The first total synthesis of magterpenoid C has been realized via a silica gel accelerated biomimetic Diels-Alder reaction between β-myrcene and randaiol derived quinone. However, application of similar strategy towards magterpenoid B via a protective Diels-Alder reaction failed to deliver the natural product.
- Kumar, Dileep,Kumar, Virendra,Salam, Abdus,Khan, Tabrez
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- Regioselective Oxybromination of Benzene and Its Derivatives by Bromide Anion with a Mononuclear Nonheme Mn(IV)-Oxo Complex
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Oxybromination of aromatic compounds by high-valent metal-oxo intermediates has yet to be explored despite extensive studies on the oxybromination of aliphatic C-H bonds of hydrocarbons. Herein, we report the regioselective oxybromination of methoxy-substituted benzenes by a nonheme MnIV-oxo complex binding scandium ions, [(Bn-TPEN)MnIV(O)]2+-(Sc(OTf)3)2 (1), in the presence of tetrabutylammonium bromide. The regioselective oxybromination occurs at the carbon atom with the highest positive charge via electron transfer (ET) from the methoxy-substituted benzenes to 1. ET driving force dependence of the rate constants of ET from methoxy-substituted benzenes to 1 is well fitted in light of the Marcus theory of ET. Under photoirradiation, the oxybromination of benzene by 1 can be achieved via ET from benzene to the photoexcited state of 1, although no reaction occurs between benzene and the ground state of 1 in the dark. To the best of our knowledge, this is the first example of reporting the stoichiometric regioselective oxybromination of the benzene ring by a synthetic high-valent Mn(IV)-oxo complex and the catalytic regioselective oxybromination reaction with a Mn(II) complex and a terminal oxidant.
- Sharma, Namita,Lee, Yong-Min,Li, Xiao-Xi,Nam, Wonwoo,Fukuzumi, Shunichi
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supporting information
p. 14299 - 14303
(2019/11/03)
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- Preparation of a novel bromine complex and its application in organic synthesis
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Although molecular bromine (Br2) is a useful brominating reagent, it is not easy to handle. Herein, we describe the preparation of a novel air-stable bromine complex prepared from 1,3-dimethyl-2-imidazolidinone (DMI) and Br2, which was identified to be (DMI)2HBr3 by spectral and X-ray techniques. This complex was then used to brominate olefins, carbonyl compounds, and aromatics, as well as in the Hofmann rearrangement. Yields of reaction products using this complex were almost the same or superior to those using other bromine alternatives.
- Nishio, Yuya,Yubata, Kotaro,Wakai, Yutaro,Notsu, Kotaro,Yamamoto, Katsumi,Fujiwara, Hideki,Matsubara, Hiroshi
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p. 1398 - 1405
(2019/02/07)
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- Atom-economical brominations with tribromide complexes in the presence of oxidants
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Bromination is an important transformation in organic synthesis, and novel efficient bromination techniques are still required. Herein, we demonstrate atom-economical brominations using (DMI)2HBr3, a novel tribromide complex, with oxidants such as DMSO and Oxone. Using this system, olefinic and aromatic brominations, as well as selective α-monobrominations of ketones proceeded well to afford the desired bromides in good yields. Importantly, in these reactions all of the bromine atoms in this complex are used to brominate.
- Yubata, Kotaro,Matsubara, Hiroshi
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supporting information
p. 1001 - 1004
(2019/03/13)
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- Preparation method of 2,5-dihydroxybenzaldehyde
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The invention provides a method for synthesizing 2,5-dihydroxybenzaldehyde. The method comprises the following steps: with p-dimethoxybenzene as a raw material, carrying out bromination reaction, Grignard reaction and demethylation reaction to obtain the 2,5-dihydroxybenzaldehyde. The preparation conditions are mild, the process is simple, and the industrial application value is high.
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Paragraph 0013-0015; 0020-0022
(2019/10/29)
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- An efficient synthesis of 1-hydroxy-5,8-dimethoxy-2-naphthaldehyde
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An efficient method for the preparation of 1-hydroxy-5, 8-dimethoxy-2-naphthaldehyde (1) was developed with a high overall yield (73.8%). Compared with the previously reported method, the reaction conditions are milder and the work-up of each step is much simpler. Moreover, the starting material considerably reduces the cost and is suitable for large-scale preparations.
- Zhang, Qijing,Dong, Jinyun,Huang, Guang,Li, Shaoshun
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p. 334 - 338
(2018/02/22)
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- NOVEL CYCLIC UREA DERIVATIVE-HYDROTRIBROMIDE
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PROBLEM TO BE SOLVED: To provide a novel bromination agent easy to handle. SOLUTION: There are provided a compound represented by a general formula (1) where n is 1 or 2, R1 and R2 may be same or different and represent an alkyl group having 1 to 4 carbon atoms, preferably a methyl group, and a bromination agent using the same. EFFECT: A cyclic urea derivative-hydrotribromide, which can be used as the bromination agent, can be provided, and the compound can be applied to various bromination reactions because it is stable solid and is easy to handle. SELECTED DRAWING: None COPYRIGHT: (C)2019,JPOandINPIT
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Paragraph 0039; 0040; 0041
(2018/11/22)
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- Bromine formation in solid NaBr/KNO3 mixture and assay of this reaction via bromination of activated aromatics
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Bromine formation in the mixture of solid NaBr and KNO3 was observed and the process was studied in different acidified organic solvent–water mixtures by monitoring the bromination of acetanilide and other compounds, containing activated aromatic substituents. This assay is based on fast bromination reaction of these aromatic compounds, as differently from the assay of Br2, the brominated aromatics can be easily determined by conventional gas chromatography–mass spectrometry (GC–MS) methods. It was found that bromine was generated autocatalytically on the surface of salt crystals and the reaction was characterized by a lag period, the duration of which depended on reaction conditions, and importantly on the type of the organic solvent in the reaction mixture. As the bromine formation could be easily controlled by reaction conditions, it was suggested that the studied reaction might have practical applications as an environmentally friendly and economically feasible bromination method. It was also shown that the bromination of aromatics followed the mechanism of classical electrophilic aromatic substitution reaction.
- Rahu, Ida,Keki?ev, Ott,J?rv, Jaak,Burk, Peeter
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p. 2893 - 2898
(2018/08/23)
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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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- On the bromination of aromatics, alkenes and alkynes using alkylammonium bromide: Towards the mimic of bromoperoxidases reactivity
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This article describes an efficient method of bromination of organic substrates including aromatics, alkenes and alkynes with NH4VO3as a catalyst and H2O2as an oxidant agent using a non-toxic and easy-to-handle source of bromine, tetrabutylammonium bromide. The process was developed under mild reaction conditions and is an innovation from reported methods in aspects such as: i) short reaction times, ii) the ability to work at room temperature, iii) regioselectivity and good yields.
- Mendoza, Fabian,Ruíz-Guerrero, Rosario,Hernández-Fuentes, Carlos,Molina, Paulina,Norzagaray-Campos, Mariano,Reguera, Edilso
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supporting information
p. 5644 - 5648
(2016/11/28)
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- Synthetic Studies toward Actinorhodin and γ-Actinorhodin by using a Homo-coupling Strategy: Synthesis of Hemiactinorhodin and Hemi-γ-actinorhodin
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A homo-coupling strategy toward the synthesis of actinorhodin and γ-actinorhodin has been explored. The monomeric unit was synthesized by employing an efficient combination of D?tz benzannulation and oxa-Pictet-Spengler reactions. Attempts towards oxidative homo-coupling of the pyranonaphthalene monomer intermediate to give dimer were unsuccessful. Later, monomer pyranonaphthalene was carried forward to complete the synthesis of hemiactinorhodin and hemi-γ-actinorhodin.
- Mulay, Sandip V.,Bhowmik, Amit,Fernandes, Rodney A.
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p. 4931 - 4938
(2015/08/03)
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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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- 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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- Halodeboronation of organotrifluoroborates using tetrabutylammonium tribromide or cesium triiodide
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Halodeboronation of organotrifluoroborates using commercially available tetrabutylammonium tribromide (TBATB) or cesium triiodide in aqueous medium is reported. The mild, transition metal-free method has proven to be tolerant of a wide range of functional groups. High regio- and chemoselectivity are observed. Two synthetic routes to (Z)-dibromoalkenes from alkynes, through stereodefined (Z)-2-bromoalkenyltrifluoroborates and (Z)-1,2-bis(boryl) alkenyltrifluoroborates, have been developed using the TBATB mediated bromodeboronation as the key step.
- Yao, Min-Liang,Kabalka, George W.,Blevins, David W.,Reddy, Marepally Srinivasa,Yong, Li
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experimental part
p. 3738 - 3743
(2012/06/30)
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- In situ acidic carbon dioxide/water system for selective oxybromination of electron-rich aromatics catalyzed by copper bromide
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Carbon dioxide, being one of the major greenhouse gases responsible for global warming, its atmospheric level grows ever faster since the beginning of industrial era. Great efforts have been devoted to developing versatile technologies/processes to adjust and manipulate the rapid growth of CO 2 emission. Besides CO2 capture and storage/sequestration (CCS) to control its emission, chemical utilization of the captured CO 2 (CCU) emerges to be a rational technique for economical benefits as well as environmental concerns. As for the aim of CO2 utilization, an environmentally benign CO2/water reversible acidic system was developed for the copper (II)-catalyzed selective oxybromination of electron-rich aromatics without the need of any conventional acid additive and organic solvent. Notably, up to 95% yields of the bromination products were attained with good regio-selectivity when cupric bromide was used as the catalyst and lithium bromide as a cheap and easy handling bromine source under supercritical CO2. The catalytic system worked well for electron-rich aromatics including ethers, sulfides and mesitylene. Carbonic acid in situ formed from CO2 and water is supposed to act as the proton donator in the Bronsted acid-promoted reaction. Notably, CO2 in this study serves as a reaction medium and a promoter in conjunction with water and also provides safe environment for aerobic reactions. Given with excellent reaction efficiency as well as no need of neutralization disposal, this process thus represents an environmentally friendly approach for aerobic bromination of aromatics with essential reduction of CO2 emission as well as an economically beneficial way for application of captured CO2.
- Liu, An-Hua,Ma, Ran,Zhang, Meng,He, Liang-Nian
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- New nickel(ii) and iron(ii) helicates and tetrahedra derived from expanded quaterpyridines
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As an extension of prior studies involving the linear quaterpyridine ligand, 5,5″′-dimethyl-2,2′:5′,5″:2″, 2″′-quaterpyridine 1, the synthesis of the related expanded quaterpyridine derivatives 2 and 3 incorporating dimethoxy-substituted 1,4-phenylene and tetramethoxy-substituted 4,4′-biphenylene bridges between pairs of 2,2′-bipyridyl groups has been carried out via double-Suzuki coupling reactions between 5-bromo-5′-methyl-2′- bipyridine and the appropriate di-pinacol-diboronic esters using microwave heating. Reaction of 2 and 3 with selected Fe(ii) or Ni(ii) salts yields a mixture of both [M2L3]4+ triple helicates and [M4L6]8+ tetrahedra, in particular cases the ratio of the products formed was shown to be dependent on the reaction conditions; the respective products are all sufficiently inert to allow their chromatographic separation and isolation. Longer reaction times and higher concentrations were found to favour tetrahedron formation. The X-ray structures of solvated [Ni2(2)3](PF6)4, [(PF6) ? Fe4(2)6](PF6) 7, [Fe4(3)6](PF6)8 and [Ni4(3)6](PF6)8 have been determined, while the structure of the parent Fe(ii) cage in the series, [(PF6) ? Fe4(1)6](PF6) 7, was reported previously. The internal volumes of the Fe(ii) tetrahedral cages have been calculated and increase from 102 A3 for [Fe4(1)6]8+ to 227 A3 for [Fe4(2)6]8+ to 417 A3 for [Fe4(3)6]8+ and to an impressive 839 A3 for [Ni4(3)6]8+. The corresponding void volume in the triple helicate [Ni2(2) 3]4+ is 29 A3.
- Glasson, Christopher R. K.,Meehan, George V.,Motti, Cherie A.,Clegg, Jack K.,Turner, Peter,Jensen, Paul,Lindoy, Leonard F.
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supporting information; experimental part
p. 10481 - 10490
(2011/11/13)
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- An efficient and regioselective monobromination of electron-rich aromatic compounds using catalytic hypervalent iodine(III) reagent
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An efficient and regioselective monobromination of electron-rich aromatic compounds is reported in which iodobenzene is used as the recyclable catalyst in combination with m-chloroperbenzoic acid as the terminal oxidant. The bromination of electron-rich aromatic compounds with lithium bromide was fast in tetrahydrofuran at room temperature, providing regioselective monobrominated products in good yields.
- Zhou, Zhongshi,He, Xuehan
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experimental part
p. 207 - 209
(2011/03/18)
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- In situ acidic carbon dioxide/ethanol system for selective oxybromination of aromatic ethers catalyzed by copper chloride
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An environmentally benign carbon dioxide/ethanol reversible acidic system was developed for the copper(II)-catalyzed regioselective oxybromination of aromatic ethers without the need of any conventional acid additive and organic solvent. Good to excellent yields together with very good regioselectivity were achieved when easily available cupric chloride dihydrate was used as catalyst and lithium bromide as the cheap and easy-to-handle bromine source under supercritical carbon dioxide conditions. Notably, the catalytic system worked well for a wide range of aromatic ethers including sulfides, resulting in the formation of the mono-brominated products in high yields and exclusive regioselectivity. The alkylcarbonic acid in situ formed from ethanol and carbon dioxide is assumed to play the crucial role in the Braonsted acid-promoted reaction, which could probably act as the proton donator, and was studied employing in situ FT-IR technique under carbon dioxide pressure by monitoring the vibration shift of the hydroxy group of ethanol. Given with excellent bromine atom efficiency as well as no need of neutralization in waste disposal, this approach thus represents a greener pathway for the aerobic bromination of aromatic ethers. A possible catalytic cycle for the in situ alkylcarbonic acid-assisted oxybomination and the effect of supercritical carbon dioxide, i.e., activation of alcohol and enhancement of mass transfer are also discussed. Copyright
- Liu, An-Hua,He, Liang-Nian,Hua, Fang,Yang, Zhen-Zhen,Huang, Cheng-Bin,Yu, Bing,Li, Bin
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experimental part
p. 3187 - 3195
(2012/01/06)
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- Chemoselective bromodeboronation of organotrifluoroborates using tetrabutylammonium tribromide: Application in (Z)-dibromoalkene syntheses
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(Chemical Equation Presented) Tetrabutylammonlum trlbromlde (TBATB) has been found to be a unique bromodeboronatlon reagent for organotrlf luoroborates. When compared to previously reported bromodeboronatlon methods, the mild and metal-free reaction conditions tolerate a wider range of functional groups. High reglo- and chemoselectlvlty are observed In the presence of both unsaturated carbon-carbon bonds and aldehyde functional groups. An efficient synthetic route to (Z)-dlbromoalkenes from terminal alkynes has been developed using the TBATB-medlated bromodeboronatlon as a key step.
- Yao, Min-Liang,Reddy, Marepally Srinivasa,Li, Yong,Walfish, Ingrid,Blevins, David W.,Kabalka, George W.
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supporting information; experimental part
p. 700 - 703
(2010/04/02)
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- Gold-catalyzed halogenation of aromatics by N-halosuccinimides
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(Chemical Equation Presented) Golden bromination: A highly efficient and mild AuCl3-catalyzed bromination of aromatic rings with Nbromosuccinimide (NBS) has been developed. This method works with a low catalyst loading (down to 0.01 mol %) and can be combined with transition metal catalyzed transformations to deliver various aryl products.
- Mo, Fanyang,Yan, Jerry Mingtao,Qiu, Di,Li, Fei,Zhang, Yan,Wang, Jianbo
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scheme or table
p. 2028 - 2032
(2010/06/17)
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- CAN-mediated oxidations for the synthesis of xanthones and related products
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Reaction of (2,4,5-trimethoxyphenyl)(2-hydroxyphenyl)methanone with ceric ammonium nitrate furnished the xanthone, 2,3-dimethoxy-9H-xanthen-9-one. Under the same conditions the related (1,4-dimethoxynaphthalen-2-yl)(2-hydroxyphenyl) methanone resulted in the formation of 12a-methoxy-5H-benzo[c]xanthenes 5,7(12aH)-dione. Other examples of this novel transformation are also outlined.
- Johnson, Myron M.,Naidoo, Jeremy M.,Fernandes, Manuel A.,Mmutlane, Edwin M.,Van Otterlo, Willem A. L.,De Koning, Charles B.
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supporting information; experimental part
p. 8701 - 8704
(2011/02/26)
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- Synthesis of arylbromides from arenes and Nbromosuccinimide bromosuccinimide (NBS) in acetonitrile - A convenient method for aromatic bromination
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Regioselective and chemoselective electrophilic bromination of a wide series of activated arenes using N-bromosuccinimide (NBS) in acetonitrile occurs readily. Environmentally friendly conditions, large substrate scope, and ease of synthesis enhance the utility of this method over other electrophilic bromination conditions.
- Zysman-Colman, Eli,Arias, Karla,Siegel, Jay S.
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experimental part
p. 440 - 447
(2009/12/01)
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- Preparation and characterisation of a quinone-functionalised polythiophene film on a modified electrode. Application to the potentiometric determination of glutathione and cysteine concentrations
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The new compound 3-((2,5-dimethoxyphenyl)ethynyl)thiophene has been synthesised by Sonogashira coupling. A modified electrode coated with a polythiophene film bearing a quinone moiety was obtained by electropolymerisation of the thienyl group followed by anodic oxidation of para-dimethoxyphenyl group. The cyclovoltammetric response resulting from the reaction of glutathione with the benzoquinone moiety was investigated. The responses of the modified electrode as a new potentiometric sensor of reduced thiols are proposed.
- étienne, Stéphanie,Matt, Muriel,Oster, Thierry,Samadi, Mohammad,Beley, Marc
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p. 9619 - 9624
(2008/12/22)
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- Study on the electronic effect on coordinating donors in heptacoordinate trichlorogermanes
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Trichloro[tris(2,5-dimethoxyphenyl)methyl]germane (1a), trichloro[tris(3-fluoro-6-methoxyphenyl)methyl]germane (1b), and trichloro[tris(2-methoxy-5-trifluoromethylphenyl)methyl]germane (1c) were synthesized. X-ray crystallographic analyses of 1a-c revealed their heptacoordinate geometries around the germanium atoms. The interatomic distances between the oxygen atoms and the central germanium atoms in the crystalline state were not significantly affected by change of functional groups on the benzene rings, while the optimized structures by theoretical calculations and Atoms in Molecules (AIM) analysis indicated linear relationship between the donating ability of functional groups and the O?Ge interatomic interactions.
- Iwanaga, Kohei,Kobayashi, Junji,Kawashima, Takayuki
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p. 10127 - 10132
(2008/02/13)
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- {[K.18-Crown-6]Br3}n: a unique tribromide-type and columnar nanotube-like structure for the oxidative coupling of thiols and bromination of some aromatic compounds
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Reaction of 18-crown-6 with KBr and then with bromine (Br2) afforded a unique tribromide salt with a nanotube-like structure ({[K.18-crown-6]Br3}n). Oxidative coupling of thiols and bromination of some aromatic compounds is the first report on the chemistry of this reagent.
- Zolfigol, Mohammad Ali,Chehardoli, Gholamabbas,Salehzadeh, Sadegh,Adams, Harry,Ward, Michael D.
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p. 7969 - 7973
(2008/03/14)
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- Copper(II) bromide: A simple and selective monobromination reagent for electron-rich aromatic compounds
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Copper(II) bromide was found to be a simple and efficient reagent for monobromination of electron-rich aromatic compounds at room temperature. The reaction proceeded smoothly with phenols, aryl alkyl ethers, and aromatic amines to afford the corresponding monobrominated product selectively in moderate to good yields. Copyright Taylor & Francis Group, LLC.
- Bhatt, Suchitra,Nayak, Sandip K.
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p. 1381 - 1388
(2008/02/01)
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- Grindstone chemistry: (Diacetoxyiodo)benzene-mediated oxidative nuclear halogenation of arenes using NaCl, NaBr or I2
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A technique of "Grindstone chemistry" is applied to the solvent-free halogenation of arenes with NaCl, NaBr or I2 using (diacetoxyiodo)benzene as the oxidant. Improved yields and higher purities of the products are observed compared with those from established methods.
- Karade,Tiwari,Huple,Siddiqui
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p. 366 - 368
(2007/10/03)
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- Quinol fatty alcohols as promoters of axonal growth
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The synthesis of three series of quinol fatty alcohols (QFAs) and their biological activities on the promotion of axonal growth are described. Interestingly, the 15-(2,5-dimethoxyphenyl)pentadecan-1-ol, the QFA bearing 15 carbon atoms on the side chain (n = 15), shows the most potent promotion of axonal growth in the presence of both permissive and non-permissive naturally occurring substrates such as Sema3A and myelin proteins.
- Hanbali, Mazen,Vela-Ruiz, Marta,Bagnard, Dominique,Luu, Bang
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p. 2637 - 2640
(2007/10/03)
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- CONJUGATED ORGANIC MOLECULES FOR MOLECULAR ELECTRONIC DEVICES
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There is provided a conjugated molecule that is useful as a conductive path in an electronic device. The conjugated molecule includes at least one p/n junction so as to provide a direction to electron flow and one end alligator clip group which allows for self-orientation of the molecule during assembly in a device, resulting in an asymmetric structure of the molecule. The conjugated molecule may be used in diodes, molecular switches, transistors, and in the manufacture of memory devices.
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Page/Page column 25-26
(2010/11/23)
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- Practical and regioselective halogenations of aromatic compounds using tetrabutylammonium peroxydisulfate
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The halogenated aromatic compounds have been important intermediates for various synthetic methods. Electron-rich aromatic compounds were easily iodinated using tetrabutylammonium peroxydisulfate (1) and iodine in mild conditions with excellent yields. Bromination was achieved using 1 and bromine, and regioselective bromination of highly activated aromatic compounds was also achieved using 1 and lithium bromide in mild conditions with excellent yields. Copyright Taylor & Francis Inc.
- Min, Young Park,Seung, Gak Yang,Kim, Yong Hae
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p. 1235 - 1240
(2007/10/03)
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- Formal total synthesis of shikonin via D?tz benzannulation
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The D?tz benzannulation reaction provides mild conditions for the construction of highly functionalized aromatic compounds. We have utilized this method for the formal total synthesis of shikonin. The key step in our approach is the application of the D?tz benzannulation reaction between Fischer a chromium carbene complex and an optically active alkyne for the construction of the aromatic skeleton. This is followed by protecting group manipulation and formation of the epoxide moiety using the Sharpless procedure.
- Pulley, Shon R.,Czakó, Barbara
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p. 5511 - 5514
(2007/10/03)
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- Practical and regioselective brominations of aromatic compounds using tetrabutylammonium peroxydisulfate
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Direct bromination of wide range of aromatic compounds substituted with electron donating groups such as methoxy, hydroxy, or amino groups have been achieved with high regioselectivity by the reaction with Br2 in the presence of tetrabutylammonium peroxydisulfate 1 under mild conditions in acetonitrile in excellent yields. The use of lithium bromide as a bromination reagent afforded high yields of monobromo compounds with complete regioselectivity under neutral and mild reaction conditions in acetonitrile.
- Park, Min Young,Yang, Seung Gak,Jadhav, Vidyadhar,Kim, Yong Hae
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p. 4887 - 4890
(2007/10/03)
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- Ionic liquid promoted regioselective monobromination of aromatic substrates with N-bromosuccinimide
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Aromatic substrates were monobrominated regioselectively with NBS in the ionic liquid 1,3-di-n-butylimidazolium tetrafluoroborate [bbim]BF4 in 5 min at 28°C in excellent isolated yields (80-98%) in the absence of a catalyst.
- Rajagopal,Jarikote,Lahoti,Daniel, Thomas,Srinivasan
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p. 1815 - 1817
(2007/10/03)
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- Halogenation of Aromatic Compounds by N-chloro-, N-bromo-, and N-iodosuccinimide
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An efficient and mild method for the halogenation of aromatic compounds using N-chloro-, N-bromo-, and N-iodosuccinimide in the presence of NH 4NO3 or FeCl3 in acetonitrile was developed.
- Tanemura, Kiyoshi,Suzuki, Tsuneo,Nishida, Yoko,Satsumabayashi, Koko,Horaguchi, Takaaki
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p. 932 - 933
(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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- Friedel-Crafts Benzylation of 1,4-Dialkoxybenzenes - Cleavage and Rearrangement of Esters and Methoxymethyl Ethers in ZnCl2 Montmorillonite K10 Clay
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Benzylation of p-dialkoxybenzenes can be achieved through the use of modified montmorillonite K10 clay. For the first time, synthese of nitro-diarylmethanes were obtained by Friedel-Crafts alkylation with good yields. In the case of p-methoxymethyl phenyl ether and phenyl ester, selectivity favoring Fries rearrangement over benzylation is reported.
- Waterlot, C.,Couturier, D.,Hasiak, B.
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p. 417 - 429
(2007/10/03)
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- Pigments of Fungi. LIX - Synthesis of (1S,3S)- and (1R,3R)-austrocortilutein and (1S,3S)-austrocortirubin from citramalic acid
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The naturally occurring tetrahydroanthraquinone (1S,3S)-austrocortilutein (1) is synthesized for the first time in enantiomerically pure form by Diels-Alder cycloaddition between the functionalized butadiene derivative (8) and the chiral 1,3-dihydroxy-1,2,3,4-tetrahydro-5,8-naphthoquinone (9), the latter being derived from (R)-citramalic acid (3). The natural products (1S,3S)-austrocortirubin (2) and (1R,3R)-austrocortilutein (5) were also prepared for the first time by using the same strategy. CSIRO 2000.
- Gill, Melvyn,Harte, Michael F.,Ten, Abilio
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p. 245 - 256
(2007/10/03)
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- An application of the stille coupling for the preparation of arylated phthalonitriles and phthalocyanines
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The substituted phthalonitriles 4-phenylphthalonitrile (2a), 4-(2,5-dimethoxyphenyl)phthalonitrile (2b) and 2-(3,4-dicyanophenyl)-4-methylpyridine (2c) have been prepared in good yields from 4-iodophthalonitrile 3, the synthesis of which is also discussed, using the Stille coupling method. Such phthalonitriles are precursors for phthalocyanines with the possibility of biphenyl-like orientation of a peripheral substituent with respect to the macrocycle ring plane. As an example, 2b was used in the preparation of tetra(dimethoxyphenyl)phthalocyanine 1a. Both 1a and the corresponding zinc(II) complex show good solubility in non-polar solvents such as dichloromethane.
- Aranyos, Viviane,Castano, Ana M.,Grennberg, Helena
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p. 714 - 720
(2007/10/03)
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- Simple and practical halogenation of arenes, alkenes and alkynes with hydrohalic acid/H2O2 or TBHP)
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A simple protocol for the halogenation of arenes utilizing a combination of aqueous hydrogen peroxide (34 %) or tert-butylhydroperoxide (70 %) and hydrohalic acid is presented. A similar procure of oxyhalogenation involving the in situ generation of positive halogen reagents is applied for the preparation of vicinal trans-dibromoalkanes and dichloroalkanes from alkenes. The reaction of alkenes with a combination of hydrochloric acid and hydrobromic acid with hydrogen peroxide gave a mixture of 1-bromo 2-chloro alkanes and 1,2-dibromoalkanes: Oxidative bromination of alkynes is also reported under similar conditions.
- Barhate, Nivrutti B.,Gajare, Anil S.,Wakharkar, Radhika D.,Bedekar, Ashutosh V.
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p. 11127 - 11142
(2007/10/03)
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- Heck reaction: Stereo selective synthesis of trisubstituted olefins: Useful intermediates for anthraquinone carboxylic acid derivatives
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Palladium catalyzed arylation of dialkyl itaconate in presence of Pd(OAc)2/PPh3 as a catalyst, afforded trisubstituted olefins stereo selectively. These alkenes are useful intermediates for the synthesis of anthraquinone carboxylic acid derivatives. A new coumarin is also synthesized using this protocol.
- Rama Devi,Rajaram
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p. 591 - 597
(2007/10/03)
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- Simple and efficient chlorination and bromination of aromatic compounds with aqueous TBHP (or H2O2) and a hydrohalic acid
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A combination of aqueous tert-butylhydroperoxide (70%) or hydrogen peroxide (34%) and a hydrohalic acid was found effective in chlorination and bromination of aromatic compounds.
- Barhate, Nivrutti B.,Gajare, Anil S.,Wakharkar, Radhika D.,Bedekar, Ashutosh V.
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p. 6349 - 6350
(2007/10/03)
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- RADIKALIONEN 89. EINELEKTRONEN-OXIDATIONEN VON DIARYLDISULFIDEN MIT AlCl3/H2CCl2
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The single electron oxidation of 14 alkyl and alkoxy substituted diaryldisulfides by AlCl3/H2CCl2 has been investigated by ESR/ENDOR spectroscopy.The radical cations observed prove the following skeletal rearrangements: Those with ring hydrogens in ortho positions to the disulfide bridge preferentially form thianthrene derivatives.The isomeric dinaphthyl disulfides react differently, the 2,2'-isomer yielding the dibenzothianthrene radical cation and the 1,1'-isomer the well-known naphthalene-1,8-disulfide radical cation.For all diaryl disulfides with completely alkyl- or methoxy-blocked ortho positions, oxidative desulfuration is observed.As substantiated by additional (2)D and (33)S isotope marking, the bis(2,5-dimethoxyphenyl)disulfide reacts both to the corresponding thianthrene derivative as well as via desulfuration to the radical cation of the monosulfide.Accompanying cyclovoltammetric and photoelectron spectroscopic measurements prove that all ESR spectroscopically detected radical cations result from compounds Ar-S-Ar, Ar-SS-Ar and Ar(S)2Ar with rather low oxidation or ionisation potentials and thus suggest that each the most easily oxidized paramagnetic species is observed in the rather complex product mixtures, which form on AlCl3/H2CCl2 oxidation of diaryldisulfides. Key words: Diaryl disulfides; one-electron oxidation; radical cations; ESR/ENDOR spectra.
- Bock, Hans,Rittmeyer, Peter
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p. 261 - 292
(2007/10/02)
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- Selective bromination of aromatic compounds using potassium tribromide
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Electron-rich aromatic compounds are selectively brominated in good yield in the presence of water using potassium tribromide as the brominating agent. In this way monobromination is favored and dibromination is suppressed as compared to the use of elemental bromine as the brominating agent.
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- A Mild Selective Monobromination Reagent System for Alkoxybenzenes; N-Bromosuccinimide-Silica Gel
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The monobromination of alkoxybenzenes with N-bromosuccinimide catalyzed by silica gel in carbon tetrachloride occurred preferentially at the para-position. m-t-Butylmethoxybenzene yielded 4-bromo-3-t-butyl-1-methoxybenzene with a selectivity of 74percent even in the presence of a bulky substituent at the meta-position.
- Konishi, Hisatoshi,Aritomi, Katsutomo,Okano, Tamon,Kiji, Jitsuo
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p. 591 - 593
(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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- THE DECOMPOSITION OF SUBSTITUTED BENZOYL PEROXIDES IN THE PRESENCE OF DIMETHOXYBENZENES
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Benzoyl peroxides, particularly those containing electron withdrawing substituents, undergo rapid decomposition in the presence of m-dimethoxybenzene, p-dimethoxybenzene, 2,5-di-t-butyl-1,4-dimethoxybenzene, and 2,5-dimethyl-1,4-dimethoxybenzene.Reactions are first oder in peroxide and dimethoxy benzene, increasing in the order given.Identified products are the acids corresponding to the peroxide and esters involving ring substitution, ring substitution with elimination of a t-Bu group, and benzylic substitution.It is proposed that reaction involves a rate-determining charge transfer transition state leading to radical ion pairs which collapse to products.No free radicals have been detected.
- Walling, Cheves,Chengxue, Zhao
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p. 1105 - 1112
(2007/10/02)
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