- Semiquinone-bridged bisdithiazolyl radicals as neutral radical conductors
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Semiquinone-bridged bisdithiazolyls 3 represent a new class of resonance-stabilized neutral radical for use in the design of single-component conductive materials. As such, they display electrochemical cell potentials lower than those of related pyridine-bridged bisdithiazolyls, a finding which heralds a reduced on-site Coulomb repulsion U. Crystallographic characterization of the chloro-substituted derivative 3a and its acetonitrile solvate 3a·MeCN, both of which crystallize in the polar orthorhombic space group Pna21, revealed the importance of intermolecular oxygen-to-sulfur (CO...SN) interactions in generating rigid, tightly packed radical π-stacks, including the structural motif found for 3a·MeCN in which radicals in neighboring π-stacks are locked into slipped-ribbon-like arrays. This architecture gives rise to strong intra- and interstack overlap and hence a large electronic bandwidth W. Variable-temperature conductivity measurements on 3a and 3a·MeCN indicated high values of θ(300 K) (>10 -3 S cm-1) with correspondingly low thermal activation energies Eact, reaching 0.11 eV in the case of 3a·MeCN. Overall, the strong performance of these materials as f = 1/ 2 conductors is attributed to a combination of low U and large W. Variable-temperature magnetic susceptibility measurements were performed on both 3a and 3a·MeCN. The unsolvated material 3a orders as a spin-canted antiferromagnet at 8 K, with a canting angle φ = 0.14° and a coercive field Hc = 80 Oe at 2 K.
- Yu, Xin,Mailman, Aaron,Lekin, Kristina,Assoud, Abdeljalil,Robertson, Craig M.,Noll, Bruce C.,Campana, Charles F.,Howard, Judith A. K.,Dube, Paul A.,Oakley, Richard T.
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Read Online
- PKa values of chiral Bronsted acid catalysts: Phosphoric acids/amides, sulfonyl/sulfuryl imides, and perfluorinated TADDOLs (TEFDDOLs)
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Measure what is measurable, and make measurable what is not so! This timeless quotation by Galileo forms the basis of all quantitative understanding, including asymmetric organocatalysis. We report pKa values for 15 chiral Bronsted acid catalysts in DMSO solutions (see scheme): the strongest acids were bis-sulfonyl/sulfuryl imides (pKa=1.7-1.9) followed by phosphoric acids/amides (pKa=2.4-4.2). A new class of chiral Bronsted acids, tetrakis-perfluoroalkyl analogues of TADDOLs (TEFDDOLs) have pKas from 2.4 to 5.7.
- Christ, Philipp,Lindsay, Anita G.,Vormittag, Sonja S.,Neudoerfl, Joerg-M.,Berkessel, Albrecht,O'Donoghue, Annmarie C.
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Read Online
- Visible-Light-Induced Radical Polynitration of Arylboronic Acids: Synthesis of Polynitrophenols
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We report a visible light-assisted one-pot method for the synthesis of polynitrophenols through radical tandem hydroxylation and nitration of arylboronic acids by utilizing copper(II) nitrate tri-nitydrate as the nitro source. This method features mild conditions, a simple procedure, and good functional group tolerance. Compared to conventional methods, this work provides a straightforward approach for the polynitration of aromatic compounds.
- Zhang, Qi,Raveendra Babu, Kaki,Huang, Zhouliang,Song, Jinna,Bi, Xihe
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supporting information
p. 2891 - 2896
(2018/06/20)
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- Nitrogen Oxides and Nitric Acid Enable the Sustainable Hydroxylation and Nitrohydroxylation of Benzenes under Visible Light Irradiation
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A new type of waste recycling strategy is described in which nitrogen oxides or nitric acid are directly employed in photocatalyzed hydroxylations and nitrohydroxylations of benzenes. Through these transformations, otherwise costly denitrification can be combined with the synthesis of valuable compounds for various applications.
- Hofmann, Laura Elena,Mach, Leonard,Heinrich, Markus R.
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supporting information
p. 431 - 436
(2017/12/15)
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- Nitration of phenolic compounds by antimony nitrate
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Antimony nitrate is new compound to be an efficient nitration reagent in the nitration of phenolic compounds with high yields. This producerworks efficiently onmost of the examples, as a grinding nitration reaction, proceed very fast (~1 min) and thermogenic. Copyright Taylor & Francis Group, LLC.
- Jirandehi, Hassan Fathinejad,Mirzaeian, Marjan
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experimental part
p. 284 - 286
(2011/07/08)
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- Synthesis of 6-aminobenzopentathiepines by reactions of 4-nitrobenzodithiol-2-ones with NaHS
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The reactions of benzodithiol-2-ones containing a 4-nitro group with NaHS led to mixtures of 6- aminobenzopentathiepines and 4-nitrobenzotrithiols. The product ratio and yields depend on the substituent in the aromatic ring. Based on the yields of benzopentathiepines, the following series of substituent efficiency can be inferred: CF3 ? F, Cl > CN. Aminobenzopentathiepines are probably formed via the intermediate benzotrithiols; the transformation apparently starts with the reduction of the nitro group.
- Khomenko, Tatyana M.,Korchagina, Dina V.,Komarova, Nina I.,Volcho, Konstantin P.,Salakhutdinov, Nariman F.
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scheme or table
p. 193 - 197
(2012/04/05)
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- PEG-N2O4: An efficient nitrating agent for the selective mono- and dinitration of phenols under mild conditions
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N2O4 was easily impregnated on polyethyleneglycol to give a stable reagent. The polyethyleneglycol-N2O4 (PEG-N2O4) system was used as an effective nitrating agent for the nitration of phenols. Mono- and dinitrophenols can be obtained via direct nitration of phenols in the presence of PEG-N2O4 at room temperature in moderate to high yields. Copyright Taylor & Francis Group, LLC.
- Zolfigol, Mohammad Ali,Madrakian, Elaheh,Ghaemi, Ezat,Niknam, Khodabakhsh
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p. 3366 - 3374
(2008/12/22)
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- Nitration of aromatic compounds by Zn(NO3)2· 2N2O4 and its charcoal-supported system
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Zn(NO3)2·N2O4 and its charcoal supported system were found to be efficient nitrating agents. Mononitration of aromatic compounds such as benzene, alkyl benzenes, halobenzenes, nitrobenzene, anisol, and the highly selective mono-, di-, and trinitration of phenol, and dinitraion of substituted phenols were also performed in the presence of these reagents.
- Iranpoor, Nasser,Firouzabadi, Habib,Heydari, Reza,Shiri, Morteza
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p. 263 - 270
(2007/10/03)
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- Silica-polyethyleneglycols/N2O4 complexes as heterogeneous nitrating and nitrosating agents
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Silica-chloride was reacted with different quantities of H(OCH2CH2)nOH (n = 2-4) to furnish silica-based linear polyethylene glycols and cyclic polyethylene glycolic ethers. The N2O4 complex of silica-tetraethylene glycolic ether (III) was selected and used as a stable, cheap, and heterogeneous silica-based reagent for the selective mono- and dinitration of phenols and nitrosation of thiols.
- Iranpoor,Firouzabadi,Heydari
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p. 1027 - 1035
(2007/10/03)
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- Silica-acetate complex of N2O4: A heterogeneous reagent for the selective nitration of phenols and nitrosation of thiols
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Complexation of gaseous N2O4 with acylated silica gel affords an addition compound, which is an efficient heterogeneous reagent for the selective mono- and dinitration of phenol, substituted phenols and nitrosation of thiols.
- Iranpoor,Firouzabadi,Heydari
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p. 703 - 710
(2007/10/03)
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- Trichloroisocyanuric Acid/NaNO2/wet SiO2 as an Efficient System for the Selective Dinitration of Phenols under Solvent-free Conditions
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Dinitrophenols can be obtained via direct nitration of phenols with trichloroisocyanuric acid, NaNO2 and wet SiO2 at room temperature under solvent-free conditions with moderate to high yields.
- Zolfigol, Mohammad Ali,Madrakian, Elaheh,Ghaemi, Ezat
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p. 2222 - 2224
(2007/10/03)
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- Selective nitration of aromatic compounds with bismuth subnitrate and thionyl chloride
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Bismuth subnitrate/thionyl chloride have been found to be an efficient combination of reagents for nitration of a wide range of aromatic compounds in dichloromethane. Phenols, in particular, were easily mononitrated and dinitrated with the reagents by controlling the stoichiometry.
- Muathen, Hussni A.
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p. 593 - 598
(2007/10/03)
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- BENZOXAZOLE DERIVATIVES AND DRUGS CONTAINING THE SAME AS THE ACTIVE INGREDIENT
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A compound represented by the following general formula (1) : wherein R1 represents a halogen atom, R2 represents hydrogen atom or a lower alkyl group, and R3 represents hydrogen atom, a lower alkyl group, a lower alkoxyl group, a hydroxy lower alkyl group, a halogen atom, or a substituted or unsubstituted amino group, wherein a substituent on the amino group is selected from the group consisting of a lower alkyl group, a lower alkenyl group, a lower alkylcarbonyl group, and an amino protective group, or a salt thereof. The compound of the present invention or a salt thereof is useful as an active ingredient of medicaments for preventive and/or therapeutic treatment of conditions of irritable bowel syndrome and digestive tract functional disorder, or condition of diarrhea.
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- Ionic complex of N2O4 with 18-crown-6: A highly efficient and selective reagent for nitration of phenols
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Interaction of gaseous N2O4 with 18-crown-6 affords the stable crystalline complex of NO+ · 18-crown-6 · H(NO3)2· This ionic complex is an efficient nitrating agent for the selective mono-, di-, and trinitration of phenol and also for the selective mono-, and dinitration of substituted phenols.
- Iranpoor,Firouzabadi,Heydari
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p. 3295 - 3302
(2007/10/03)
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- Efficient and selective mono and dinitration of phenols with Cr(No3)3. 2N2O4 as a new nitrating agent
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Cr(NO3)3.2N2O4 is easily prepared reagent for the efficient and selective mono or dinitration of phenolic compounds. High selectivity ratio of p-nitrophenol formation vs o-nitrophenol is also observed.
- Iranpoor, Nasser,Firouzabadi, Habib,Zolfigol, Mohammad Ali
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p. 2773 - 2781
(2007/10/03)
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- Dinitrogen tetroxide complexes of iron and coppernitrates as new reagents for selective mono- and dinitration of phenolic compounds
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Fe(NO3)3.1.5 N2O4 and Cu(NO3)2.N2O4 are easily prepared reagents for the efficient and selective mono- or dinitration of phenolic compounds. In comparison with metal nitrates, these complexes resemble a synergetic effect on the rates and the yields of the reactions. High ratio of p-nitrophenol formation vs o-nitrophenol is also observed in the mononitration reactions.
- Firouzabadi,Iranpoor,Zolfigol
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p. 3301 - 3311
(2007/10/03)
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- Iron(III)-catalysed nitration of non-activated and moderately activated arenes with nitrogen dioxide-molecular oxygen under neutral conditions
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In the presence of molecular oxygen and a catalytic amount of tris(pentane-2,4-dionato)iron(III), non-activated and moderately activated arenes, which include alkylbenzenes, halogenobenzenes, phenolic ethers, naphthalene and derivatives, can be nitrated with nitrogen dioxide at ice-bath temperature or below to give the corresponding nitro derivatives in fair to good yields. An electron-transfer mechanism has been proposed, where an activated NO2-FeIII complex plays a key role in the cyclic process for converting arenes into nitroarenes.
- Suzuki, Hitomi,Yonezawa, Shuji,Nonoyama, Nobuaki,Mori, Tadashi
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p. 2385 - 2389
(2007/10/03)
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- Photochemical Nitration by Tetranitromethane. X. A Possible Addition/Elimination Pathway to Trinitromethylaromatic Compounds
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The photolysis of tetranitromethane and 4-chloroanisole in dichloromethane at +20, -20 and -50 deg C led to the formation of mainly 4-chloro-2-trinitromethylanisole (40-50percent yield) and a pair of adducts (ca. 30percent yield) in which nitrito/trinitromethyl addition had taken place across the 2,5-positions of 4-chloroanisole.Small amounts of a pair of labile adducts (2-3percent yield), assigned the structure of the analogous hydroxy/trinitromethyl adducts were formed in the beginning of the runs.In acetonitrile, the major product from the same reaction was 4-chloro-2-nitroanisole at all three temperatures.Only at -50 deg C were the nitrito/trinitromethyl adducts detectable in low yield (1-2percent).The pair of nitrito/trinitromethyl adducts spontaneously decomposed in acetonitrile to give 4-chloro-2-trinitromethylanisole with rate constants of 7*10-4 min-1 at 0 deg C and 0.020 min-1 at 20 deg C, implying that they should be stable in this solvent at -20 and -50 deg C, if formed.The adducts also decomposed to 4-chloro-2-trinitromethylanisole under photochemical conditions accounting for the formation of this compound in low yield also in acetonitrile.The nitration process predominantly observed in acetonitrile presumably occurs via coupling of 4-chloroanisole radical cation and NO2, both formed in the initial photochemical step.The nitrito/trinitromethyl adducts were thermally and photochemically stable in dichloromethane under the reaction periods employed for photolysis.The conversion into labile hydroxy/trinitromethyl adducts was assumed to occur via acid-catalysed hydrolysis, eventually leading to 4-chloro-2-trinitromethylanisole via acid-promoted elimination of water from the latter adducts.However, only a minor part of this compound can be accounted for in this way.
- Eberson, Lennart,Hartshorn, Michael P.,Svensson, Jan Olof
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p. 925 - 934
(2007/10/02)
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- Proton transfers among oxygen and nitrogen acids and bases in DMSO solution
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Rate constants for the proton-transfer reactions between conjugate acids and bases of several amines, phenols, carboxylic acids, and the solvated proton in DMSO-d6 at 20 °C have been determined by the use of NMR line-shape analysis. Equilibrium constants for the same reactions are obtained from the pKa's of the acids in dimethyl sulfoxide, some of which have been reported in earlier work and the rest obtained in the present work by use of Bordwell's indicator techniques. All of the reactions have rale constants considerably below expected diffusion-controlled limits for the proton transfers in the thermodynamically favorable direction, and several of the reactions, including the identity reactions of carboxylic acids, have kinetic deuterium isotope effects, kH/kD, between 0.8 and 1.3. For reactions of N,N-dimethylbenzylammonium ion with several phenoxides, carboxylates, and solvent, the rate constants for transfers in the unfavorable directions show a reasonable Bronsted correlation with β ≈ 1 and a reasonably constant reverse rate constant of ≈3 × 106 M-1 s-1. The data clearly indicate that the proton-transfer step is not rate-limiting in these reactions. Most likely, desolvation is involved in the rate-limiting steps, but the rate constants are not simple functions of acidities as might have been expected if hydrogen bonding of acid to solvent were the major factor involved in the solvation Other factors, particularly dispersion interactions of solvent with solutes, are discussed. We suggest that the formation of an acid-base complex with proper orientation to allow contact between the proton and the basic site is rate-determining and involves desolvation along with detailed steric interactions of the acid-base pair.
- Ritchie, Calvin D.,Lu, Shanzheng
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p. 7748 - 7756
(2007/10/02)
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- Formation of 4-Halo-4-nitrocyclohexa-2,5-dienones on Nitration of p-Halophenols and p-Halophenyl Acetates.
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Nitration of p-chloro-, p-fluoro-, and p-bromo-phenol or the corresponding p-halophenyl acetates at -40 deg C and below gives the 4-halo-4-nitrocyclohexa-2,5-dienones in addition to the 4-halo-2-nitrophenols.The dienones isomerize to the nitrophenols at temperatures between -40 deg C and 0 deg C.Nitration of 4-chloro-2-methylphenol or its acetate gives both 4-chloro-2-methyl-4-nitrocyclohexa-2,5-dienone and 4-chloro-6-methyl-6-nitrocyclohexa-2,4-dienone. 4-Chloro-3-methylphenol and its acetate give 4-chloro-3-methyl-4-nitrocyclohexa-2,5-dienone.
- Clewley, Robin G.,Cross, Gordon G.,Fischer, Alfred,Henderson, George N.
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p. 1299 - 1310
(2007/10/02)
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- INTRAMOLECULAR ELECTROPHILIC DISPLACEMENT OF ACYL BY NITRO GROUP DURING ATTEMPTED SYNTHESIS OF 3-NITROCOUMARINS
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2-Hydroxyacetophenones undergo upon nitration in acetic acid a substitution of the acyl by nitro group followed by an intramolecular 1,3-acyl shift reminescent of a retro-Fries rearrangement to yield phenyl esters.
- Benedikt, George M.,Traynor, Lee
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p. 763 - 766
(2007/10/02)
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