- Introduction of an arylethynyl group onto an anthracene bisimide core for molecular design of new ?-conjugated compounds
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Novel ethynylated anthracene bisimide (ABI) derivatives were synthesized by Sonogashira and Stille couplings, and the electronic spectra of the new compounds were compared with those of molecules with related structures. The absorption spectrum and the electrochemical data of the ABI with a 9- anthrylethynyl group suggested weak electronic interactions between the donor anthracene unit and the acceptor ABI unit.
- Iwanaga, Tetsuo,Tanaka, Ryo,Toyota, Shinji
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p. 105 - 107
(2014/01/23)
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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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- Influence of (2,3,4,5,6-pentamethyl/phenyl)phenyl scaffold: Stereoelectronic control of the persistence of o-quinonoid reactive intermediates of photochromic chromenes
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Regioisomeric photochromic chromenes 1Ch-6Ch substituted with the (2,3,4,5,6-pentamethyl/phenyl)phenyl scaffold were designed to delve into stereoelectronic effects on the spectrokinetic properties of photogenerated o-quinonoid reactive intermediates. While the latter derived from 1Ch, 2Ch, 4Ch, and 5Ch were found to exhibit notable persistence, those from 3Ch and 6Ch were found to revert rapidly at room temperature to preclude visible coloration. The intermediates of 1Ch and 2Ch were found to be marginally more stable than those of 4Ch and 5Ch, respectively, attesting to the possibility of toroidal conjugation via Cipso-π orbitals in the former. The rapid reversion of the intermediates of 3Ch and 6Ch is attributed to unfavorable electronic repulsion between the phenyl ring of the (pentamethyl/phenyl)phenyl scaffold and one of the lone-pairs of the o-quinonoid oxygen. Thus, the regioisomerically substituted photochromic chromenes are shown to permit control of the reversion, very rapidly as well as slowly, of the colored o-quinonoid intermediates through operation of stereoelectronic effects differently.
- Mandal, Susovan,Parida, Keshaba Nanda,Samanta, Subhas,Moorthy, Jarugu Narasimha
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scheme or table
p. 7406 - 7414
(2011/11/06)
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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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- Environmentally benign electrophilic and radical bromination 'on water': H2O2-HBr system versus N-bromosuccinimide
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A H2O2-HBr system and N-bromosuccinimide in an aqueous medium were used as a 'green' approach to electrophilic and radical bromination. Several activated and less activated aromatic molecules, phenylsubstituted ketones and styrene were efficiently brominated 'on water' using both systems at ambient temperature and without an added metal or acid catalyst, whereas various non-activated toluenes were functionalized at the benzyl position in the presence of visible light as a radical activator. A comparison of reactivity and selectivity of both brominating systems reveals the H2O2-HBr system to be more reactive than NBS for benzyl bromination and for the bromination of ketones, while for electrophilic aromatic substitution of methoxy-substituted tetralone it was higher for NBS. Also, higher yields of brominated aromatics were observed when using H2O2-HBr 'on water'. Bromination of styrene reveals that not just the structure of the brominating reagent but the reaction conditions: amount of water, organic solvent, stirring rate and interface structure, play a key role in defining the outcome of bromination (dibromination vs bromohydroxylation). In addition, mild reaction conditions, a straightforward isolation procedure, inexpensive reagents and a lower environment impact make aqueous brominating methods a possible alternative to other reported brominating protocols.
- Podgor?ek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
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experimental part
p. 4429 - 4439
(2009/10/09)
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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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- Oxidative halogenation of aromatic compounds with metal halides and sodium bismuthate
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A new mild and efficient method for aromatic halogenation with a wide variety of halides in the presence of sodium bismuthate NaBO3 in AcOH is reported. Metal halides of groups Ia, IIa, IIIa, IVa, Va, and the first row of transition elements are suitable for this method.
- Muathen, Hussni A.
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p. 164 - 168
(2007/10/03)
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- Pyridinium dichlorobromate: A new stable brominating agent for aromatic compounds
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Pyridinium dichlorobromate (PyHBrCl2, 1) is a new example of iminium-trihalide complexes. The compound is prepared from pyridine and chlorine in the presence of aqueous hydrogen bromide. The crystalline trihalide is quite stable and acts as a safe source of positive bromine. It shows a remarkable reactivity towards aromatic compounds compared with other bromine complexes. It is also considered as a potential source for bromine chloride BrCl.
- Muathen, Hussni A.
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p. 169 - 171
(2007/10/03)
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- Ring halogenations of polyalkylbenzenes with N-halosuccinimide and acidic catalysts
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1-Bromo-2,5-pyrrolidinedione (NBS) and 1-chloro-2,5-pyrrolidinedione (NCS) with catalytic quantities of p-toluenesulfonic acid have been used for ring halogenations of polyalkylbenzenes. [Hydroxy(tosyloxy)iodo]benzene was effective as a catalyst with NBS but not NCS. Competition experiments with 1-iodo-2,5-pyrrolidinedione (NIS) were run to indicate selectivities in substrates, halogen sources and catalysts. With this information a mixed halogenated compound, 2-bromo-4-iodo-1,3,5-trimethylbenzene was prepared in high yield.
- Bovonsombat,McNelis
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p. 237 - 241
(2007/10/02)
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- ETUDE CINETIQUE DE LA REACTION DE BROMINATION DANS LE SO2 LIQUIDE. REACTIVITES DU BENZENE, DES POLYMETHYLBENZENES ET D'ANISOLES SUBSTITUES. DETERMINATION DES REACTIVITES RELATIVES ET CALCUL DES FACTEURS DE VITESSE PARTIELLE
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Absolute rate constants for the bromination of a series of anisoles and polymethylbenzenes, have been measured in liquid sulfur dioxide at -23 +/- 2 deg C.Rate constants for benzene and toluene were determined by extrapolation as: 9.6E-7 and 4.2E-4 l mol-1 mn-1 respectively.Under these conditions, the bromination of anisole provides 0.56percent ortho- and 98.99percent para-bromoanisole, and the rate relative to benzene is 6.98E8/1.00.These date lead to the partial rate factors for the methoxy group: οOMef = 1.1E7 and pOMef = 4.12E9.The value mOMef = 1.4 is calculated from the rate constant for p-dimethoxy benzene, 10 l mol-1 mn-1.Similarly, in the case of bromination of toluene, a relative rate of 443/1.00, and an isomer distribution of 16percent ortho- and 84percent para, permit the calculation of partial rate for the methyl group:οMef = 212 mMef = 6.4 pMef = 2232 > correlations log k = f(Σ?+), established for the bromination of anisoles and polymethylbenzenes, exhibit large values for their slopes (ρAnisoles+ = -10.51; ρ+polymethylbenzenes = -9.5), and indicate satisfactory additivity of substituent effects.It appears that the + M effect of the methoxy group is less strong in this solvent than it is in water or acetic acid.Despite its low dielectric constant, (D = 17.5 at -20 deg C), liquid sulfur dioxide appearars to be quite a favourable medium for electrophilic aromatic substitution.Thus, for identical experimental conditions, the rate constants for bromination are 1E2 to 1E4 lower than those observed in water, but 1E3 to 1E5 larger than those in acetic acid.
- Castellonese, Paul,Villa, Pierre
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