- Graphene nanoribbons from tetraphenylethene-based polymeric precursor: Chemical synthesis and application in thin-film field-effect transistor
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Graphene nanoribbons (GNRs) with a non-zero bandgap are regarded as a promising candidate for the fabrication of electronic devices. In this study, large-scale solution synthesis of narrow GNRs was firstly achieved by the intramolecular cyclodehydrogenati
- Ma, Ji,Zhu, Haoyun,Huang, Wei,Lin, Tingting,Pan, Xiaoyong,Wang, Weizhi
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- Dehalogenation of vicinal dihalo compounds by 1,1′-bis(trimethylsilyl)-1: H,1′ H-4,4′-bipyridinylidene for giving alkenes and alkynes in a salt-free manner
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We report a transition metal-free dehalogenation of vicinal dihalo compounds by 1,1′-bis(trimethylsilyl)-1H,1′H-4,4′-bipyridinylidene (1) under mild conditions, in which trimethylsilyl halide and 4,4′-bipyridine were generated as byproducts. The synthetic protocol for this dehalogenation reaction was effective for a wide scope of dibromo compounds as substrates while keeping the various functional groups intact. Furthermore, the reduction of vicinal dichloro alkanes and vicinal dibromo alkenes also proceeded in a salt-free manner to afford the corresponding alkenes and alkynes.
- Rej, Supriya,Pramanik, Suman,Tsurugi, Hayato,Mashima, Kazushi
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supporting information
p. 13157 - 13160
(2017/12/26)
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- Ladder-type conjugated oligomers prepared by the Scholl oxidative cyclodehydrogenation reaction: Synthesis, characterization and application in field effect transistors
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Two novel well defined ladder-type conjugated oligomers have been successfully designed and synthesized through a solution processing method in an excellent yield. The field effect transistors (FETs) fabricated by these ladder-type oligomers with a nice planar structure exhibit excellent charge carrier mobilities, up to 0.10 cm2 V-1 s-1 and 0.33 cm2 V-1 s-1; furthermore, the devices can work well with a low gate voltage. The ladder-type oligomers are both converted from two precursor co-oligomers, poly(2,7-(1,2,-diphenylethene)-9,9-dioctylfluorene) (PDPF), via an anhydrous FeCl3 oxidative cyclodehydrogenation. The pronounced red shift shown in the preliminary photoluminescence spectra and the changes of band gaps measured by electrochemical analysis both testify that the better electronic transmission capacity in the FET performance is due to the expanded molecular chain planarization after the chemical cyclodehydrogenation. Interestingly, the precursor oligomers having a linear-type chain and a zigzag-type chain (L-PDPF and Z-PDPF, respectively) show many characteristic differences in their thermal, optical and electrochemical properties. The differences caused by the different types of main chains demonstrate that the macromolecular configurations have a tremendous impact on the functioning of the oligomers.
- Huang, Wei,Zhang, Hejian,Ma, Ji,Chen, Moyun,Zhu, Haoyun,Wang, Weizhi
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supporting information
p. 6200 - 6208
(2015/06/25)
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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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- Sequential bromination reactions from beads with methyltriphenylphosphonium tribromide groups
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A reusable bromination reagent based on polystyrene beads with covalently appended methyltriphenylphosphonium tribromide groups has been developed. The results from bromination reactions of several structurally diverse unsaturated substrates with the beads and with solutions of a non-polymeric model brominating reagent, methyltriphenylphosphonium tribromide, are described. It is shown that the reactions are highly regio- and stereo-selective and can be conducted easily. Copyright
- Cristiano, Rodrigo,Walls, Andrew D.,Weiss, Richard G.
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supporting information; experimental part
p. 904 - 909
(2011/09/14)
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- 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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- Selective aerobic oxidative dibromination of alkenes with aqueous HBr and sodium nitrite as a catalyst
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Various alkenes (internal, terminal, aryl and alkyl substituted) and 1,2-diphenylethyne were efficiently and selectively dibrominated using 2 equivalents of 48% aqueous hydrobromic acid, with air as an oxidant and sodium nitrite as a catalyst. Despite the presence of water, only trans dibromination occurred producing anti-1,2-dibromoalkanes and (E)-1,2-dibromo-1,2- diphenylethene. A comparison of resource demand, waste production and environmental, health and safety issues of the NaNO2 catalyzed aerobic bromination with molecular bromine and other oxidative bromination methods revealed that the proposed method is not only selective and effective but has a better environmental profile.
- Podgorsek, Ajda,Eissen, Marco,Fleckenstein, Jens,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
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experimental part
p. 120 - 126
(2010/04/22)
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- 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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- Mild oxidative bromination of alkenes and alkynes with zinc bromide and lead tetraacetate
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Zinc bromide and lead tetraacetate is a practical and safe source of bromine. The combined reagents are used to brominate a variety of alkenes to vicinal dibromoalkanes. Similarly, alkynes can be converted into dibromoalkenes in high yields. The reagents are also capable of tetrabromination of alkynes.
- Muathen, Hussni A.
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p. 3545 - 3552
(2007/10/03)
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- The effect of vicinyl olefinic halogens on cross-coupling reactions using Pd(0) catalysis
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(trans) 1-Chloro-2-iodoethylene (3), (trans) 1-bromo-2-iodoethylene (4), (trans) 1,2-diiodoethylene (5) and (cis and trans) 1,2-dibromoethylene (11) were reacted under Suzuki, Sonogashira and Negishi cross-coupling conditions using Pd catalysis to obtain mono coupled products. Only olefin template 3 provided the desired coupling products reliably under all reaction conditions. Compound 5 did not provide cross coupled products under any of the reaction conditions used. The Negishi reaction was the only one that worked for templates 4 and 11. Studies indicate that oxidative addition of the most reactive carbon-halogen bond to Pd(0) is followed by elimination of the second halide, when the second halide is a bromide or an iodide. This happens to a much lesser degree when the second halogen is a chloride. Graphical Abstract.
- Organ, Michael G.,Ghasemi, Haleh,Valente, Cory
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p. 9453 - 9461
(2007/10/03)
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- Spectroscopic and theoretical investigations of electrophilic bromination reactions of alkynes: The first evidence for π complexes as reaction intermediates
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A bromine-alkyne π complex (λmax = 294 nm) of 1:1 stoichiometry has been observed for the first time in the course of the bromination of 1-phenylpropyne by means of a diode-array stopped-flow technique. The formation enthalpy and entropy (ΔHsu
- Bianchini, Roberto,Chiappe, Cinzia,Moro, Giacomo Lo,Lenoir, Dieter,Lemmen, Peter,Goldberg, Norman
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p. 1570 - 1580
(2007/10/03)
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- Bromide ions and methyltrioxorhenium as cocatalysts for hydrogen peroxide oxidations and brominations
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Oxidation of alcohols by hydrogen peroxide is negligible; even when catalyzed by methyltrioxorhenium (MTO), the process requires a long reaction time. The addition of a catalytic quantity of bromide ions, as HBr or NaBr, greatly enhances the rate. Some of the reactions were carried out on a larger scale in glacial acetic acid, and others at kinetic concentrations. The data establish that Br2 is the active oxidizing agent in the system, because the catalytic rates under suitable circumstances match those for the independently measured Br2 reaction with alcohol (benzyl alcohol, in particular). At much lower levels of MTO, however, Br2 formation plays a role in the kinetics. Certain other reluctant transformations are conveniently carried out with the MTO/H2O2/Br- combination: aldehydes to methyl esters; 1,3-dioxolanes to glycol monoesters; and ethers (with cleavage) to ketones (mostly), but in fair yield only. When Br- was used in stoichiometric quantity, certain bromination reactions occur. Thus, phenyl acetylenes (PhC2R, R = H, Me, Ph) are converted to dibromoalkenes that are entirely or largely formed as the trans isomer, and phenols are brominated. The latter reaction shows the preference para > ortho > meta. Kinetic studies of benzyl alcohol oxidation with MTO/H2O2Br- were carried out in aqueous solution. With sufficient (normal) levels of MTO, the rate constant for the formation of benzaldehyde agreed with the independently determined value for Br2 + PhCH2OH, k = 4.3 x 10-3 L mol-1 s-1 at 25.0 °C; for sec- phenethyl alcohol, k = (9.8 ± 0.4) x 10-3 L mol-1 s-1. Bromine is formed from the known oxidation of Br- with H2O2, catalyzed by MTO. This reaction results in BrO-/HBOr, which is then rapidly converted to Br2. However, with substantially lower concentrations of MTO, the buildup of benzaldehyde is ca. 4-fold slower, reflecting the diminished rate of Br- oxidation.
- Espenson,Zhu,Zauche
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p. 1191 - 1196
(2007/10/03)
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- Solvent incorporation in bromination of alkynes with tetrabutylammonium tribromide in methanol
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The reaction of tetrabutylammonium tribromide (TBABr3) with mono and disubstituted alkynes in methanol at 20°C leads to the formation of mainly the corresponding α,α-dibromo, β,β-dimethoxyalkane and the E-(α,β)- dibromoalkene. The additions are faster using sonication.
- Berthelot, Jacques,Benammar, Yamina,Desmazieres, Bernard
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p. 2865 - 2876
(2007/10/03)
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- Reaction of Aromatic and Unsaturated Compounds with the Potassium Permanganate/HCI (HBr) Acetonitrile Reagent
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Addition of hydrochloric or hydrobromic acid to a solution of potassium permanganate in acetonitrile produced a homogeneous mixture, which is suitable for laboratory chlorination or bromination, respectively. Aromatic compounds more reactive than alkylbenzenes can be chlorinated or brominated without additional catalyst. Alkenes and alkynes give the corresponding vicinal dihaloalkanes and vinyl halides. All reactions complete within two hours under mild condition (25-60 °C) with excellent to moderate yields.
- Liu, Lilian Kao,Lin, Ching-Shan
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- Effect of substituents on the competition between several mechanisms of nucleophilic vinylic substitution
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In an attempt to encourage vinylic substrates to undertake an SRN1-like nucleophilic substitution route, a process that requires acquisition of one electron, a series of stilbene halides bearing one electron-withdrawing substituent on the doubl
- Amatore, Christian,Galli, Carlo,Gentili, Patrizia,Guarnieri, Alessandra,Schottland, Ettie,Rappoport, Zvi
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p. 2341 - 2350
(2007/10/03)
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- Photothermal Side-Chain Bromination of Methyl-, Dimethyl-, and Trimethylbenzenes with N-Bromosuccinimide
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Tri- and dibromination of methyl-, dimethyl-, and trimethylbenzenes with N-bromosuccinimide were accomplished by photothermal reaction with a tungsten lamp in carbon tetrachloride or benzene. (Dibromomethyl)arenes and (tribromomethyl) derivatives were produced depending upon a solvent used and a substituent on the benzene ring.In the bromination of methylbenzenes without a substituent on the ortho-position, (tribromomethyl)benzenes were formed.On the other hand, ortho-substituted methylbenzenes gave (dibromomethyl)benzenes. α,β-Dibromo-1,2-diarylstilbenes were formed via the debrominative carbon-carbon coupling reaction of ...
- Mataka, Shuntaro,Liu, Guo-Bin,Sawada, Tsuyoshi,Kurisu, Masayoshi,Tashiro, Masashi
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p. 1113 - 1119
(2007/10/02)
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- Side-Chain Bromination of Diphenylmethanes, 1,2-Diphenylethanes, and 10,11-Dihydro-5H-dibenzocycloheptenes with N-Bromosuccinimide under Irradiation of a Tungsten Lamp
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The photothermal bromination of diphenylmethane and methyl derivatives with N-bromosuccinimide afforded benzophenone and (polybromomethyl)benzophenones via the hydrolysis of dibromodiphenylmethanes. 1,2-Diphenylethane and p-t-butyl derivative gave dibromostilbenes, while the o-methyl derivative afforded bis(dibromomethyl)dibromodiphenylethane. 10,11-Dihydro-5H-dibenzocycloheptene gave 9-bromodibenzocycloheptenone, which was also obtained in the bromination of 10,11-dihydro-5H-dibenzocyclohepten-5-one.
- Mataka, Shuntaro,Liu, Guo-Bin,Tori-I, Akiyoshi,Tashiro, Masashi
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p. 2336 - 2338
(2007/10/02)
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- The reaction of benzotrihalides and benzal halides with magnesium. Synthetic and mechanistic studies
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The benzotrihalides (PhCX3) where X = Cl, Br, and F were allowed to react with magnesium in THF at room temperature.When the halide was chloride or bromide, the trihalide gave diphenylacetylene in high yield in addition to several minor products which were identified.No reaction was observed when the halide was fluoride.When the corresponding dichloride was allowed to react with magnesium in THF, stilbene was formed as the major product.The possible mechanisms for these reactions are discussed.
- Ashby, E. C.,Al-Fekri, Dheya M.
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p. 275 - 292
(2007/10/02)
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- Bromation stereoselective d'alcynes par le tribromure de tetrabutylammonium
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The reaction of tetrabutylammonium tribromide (TBABr3) with alkynes (R-CC-R', with R and (or) R'=H, alkyl, phenyl, carboxyl, carbonyl) in chloroform at 20 deg C gives only the corresponding E 1,2-dibromo alkene in high yields.A mechanism involving a cy
- Berthelot, Jacques,Fournier, Michel
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p. 603 - 607
(2007/10/02)
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- THE BROMINATION OF METHYLARENES WITH NBS BY IRRADIATION USING A TUNGSTEN LAMP. PREPARATION OF BENZOTRIBROMIDES
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Bromination of toluene and its meta- and para-substituted derivatives with NBS by irradiation using a tungsten lamp gave benzotribromides and cis- and trans-1,2-dibromo-1,2-diaryl-ethylenes, while ortho-substituted toluenes gave benzal bromides. o-Xylene gave tetra- and pentabromides and m-xylene afforded a mixture of dibromodiarylethylenes.
- Mataka, Shuntaro,Kurisu, Masayoshi,Takahashi, Kazufumi,Tashiro, Masashi
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p. 1969 - 1972
(2007/10/02)
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