- A Common, Facile and Eco-Friendly Method for the Reduction of Nitroarenes, Selective Reduction of Poly-Nitroarenes and Deoxygenation of N-Oxide Containing Heteroarenes Using Elemental Sulfur
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A transition metal-free, environment-friendly and practical protocol was developed either for the reduction of nitroarenes or for the deoxygenation of N-oxide containing heteroarenes. The reaction proceeded with the use of a non-toxic and cheap feedstock as elemental sulfur in aqueous methanol under relatively mild conditions. Green chemistry credentials were widely favorable compared to traditional and industrial protocols with good E-factors and a low production of waste. The strategy allowed the efficient reduction of a large variety of substituted-nitroarenes including various o-nitroanilines as well as selective reduction of various poly-nitroarenes in excellent yields with a broad substrate scope. The protocol was successfully extended to the deoxygenation of some N-oxide containing heteroarenes, like benzofuroxans, phenazine N,N'-dioxides, pyridine N-oxides, 2H-indazole N1-oxides, quinoxaline N1,N4-dioxides and benzo[d]imidazole N1,N3-dioxides. A gram-scale example for the synthesis of luminol, in green conditions, was reported. A solid mechanism of reaction was proposed from experimental evidences.
- Cerecetto, Hugo,Romero, Angel H.
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supporting information
(2020/03/23)
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- Photocatalytic C-H Amination of Aromatics Overcoming Redox Potential Limitations
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We report the photocatalytic C-H amination of aromatics overcoming redox potential limitations. Radical cations of aromatic compounds are generated photocatalytically using Ru(phen)3(PF6)2, which has a reduction potential at a high oxidation state (Ered(RuIII/RuII) = +1.37 V vs SCE) lower than the oxidation potentials of aromatic substrates (Eox = +1.65 to +2.27 V vs SCE). The radical cations are trapped with pyridine to give N-arylpyridinium ions, which were converted to aromatic amines.
- Ikarashi, Gun,Kano, Naokazu,Morofuji, Tatsuya
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supporting information
p. 2822 - 2827
(2020/04/16)
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- Pyrroloquinoline quinone synthetic method
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The invention discloses a synthetic method of pyrroloquinoline quinone. The synthetic method comprises the following steps: carrying out alkali treatment on 2-methoxy-5-nitroaniline hydrochloride as a raw material, so as to obtain a compound 1; carrying out formylation on the compound 1 under a catalysis condition of an ionic liquid, so as to obtain a compound 2; adopting sodium borohydride to reduce the compound 2 to obtain a compound 3; carrying out diazotization on the compound 3, and then enabling action between the diazotized compound 3 and HBF4 to obtain a compound 4; enabling reaction of the compound 4 and 2-methylethyl acetoacetate to obtain a compound 5; treating the compound 5 with formic acid to obtain a compound 6; carrying out amid catalysis and exchange with the ionic liquid on the compound 6 to obtain a compound 7; enabling reaction of the compound 7 and 2-oxodimethyl glutaconate to obtain a compound 8; feeding hydrogen chloride to the compound 8 under the action of Cu(OAc)2*2H2O to obtain a compound 9; carrying out basic hydrolysis on the compound 9 to obtain a compound 10. The synthetic method disclosed by the invention is cheap and accessible in raw materials, stable, high in reaction yield, quick in reaction, and easy for product separation, and is environment-friendly as the catalyst can be recycled.
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Paragraph 0052-0053
(2018/05/07)
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- Altering the regioselectivity of a nitroreductase in the synthesis of arylhydroxylamines by structure-based engineering
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Nitroreductases have great potential for the highly efficient reduction of aryl nitro compounds to arylhydroxylamines. However, regioselective reduction of the desired nitro group in polynitroarenes is still a challenge. Here, we describe the structure-based engineering of Escherichia coli nitroreductase NfsB to alter its regioselectivity, in order to achieve reduction of a target nitro group. When 2,4-dinitrotoluene was used as the substrate, the wild-type enzyme regioselectively reduced the 4-NO2 group, but the T41L/N71S/F124W mutant primarily reduced the 2-NO2 group, without loss of activity. The crystal structure of T41L/N71S/F124W and docking experiments indicated that the regioselectivity change (from 4-NO2 to 2-NO2) might result from the increased hydrophobicity of residues 41 and 124 (proximal to FMN) and conformational changes in residues 70 and 124. The regioselectivity of nitroreductase NfsB from E. coli toward 2,4-dinitrotoluene was shifted from the 4-NO2 group to the 2-NO2 group without loss of activity, by introducing three mutations: T41L, N71S, and F124W. This study provides an example of a tailored enzyme for regioselective synthesis of the target arylhydroxylamines.
- Bai, Jing,Zhou, Yong,Chen, Qi,Yang, Qing,Yang, Jun
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p. 1219 - 1225
(2015/05/27)
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- Selective partial hydrogenation of dinitrobenzenes to nitroanilines catalyzed by Ru/C
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Ru/C was found to be a highly effective catalyst for the selective partial hydrogenation of a range of dinitrobenzenes to their corresponding nitroanilines with excellent selectivity under mild conditions. Furthermore, the effect from other substitute groups of dinitrobenzenes on partial hydrogenation was also explored in this study. Copyright
- Hou, Jie,Ma, Yonghuan,Li, Yuhan,Guo, Fang,Lu, Lianhai
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scheme or table
p. 974 - 975
(2009/04/06)
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- Effect of the electronic structure of the radical anions of 4-substituted 1,2-and 1,3-dinitrobenzenes on the regioselectivity of reduction of the nitro groups
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Theoretical and experimental regularities of the regioselectivity of the reduction of one of the two nitro groups in unsymmetrical dinitrobenzenes were studied. It was found that the regioselectivity of the formation of isomeric nitroanilines depends on the structure of the substrate and the nature of the reducing agent. The reduction regioselectivity model was verified, according to which radical anion protonation is the major reaction direction. Pleiades Publishing, Inc. 2006.
- Orlov,Begunov,Demidova,Rusakov
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- New nitronate σ complexes and the mechanism of nucleophilic aromatic photosubstitution para to a nitro group
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Photolysis of 4-nitroanisole with aliphatic amines gives mainly N-substituted 4-nitroanilines. Reactions of this type have been widely attributed to a geminate radical mechanism. We questioned this interpretation and have searched for and found by NMR spectroscopy a new class of stable nitronate adducts generated under the reaction conditions. The adducts imply that photosubstitution by amines para to the nitro group occurs by meta σ complex formation followed by an unprecedented sigmatropic rearrangement.
- Wubbels, Gene G.,Johnson, Kandra M.
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p. 1451 - 1454
(2007/10/03)
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- Guanidinium nitrate: A novel reagent for aryl nitrations
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Nitration of various aromatic compounds utilising guanidinium nitrate in 85% sulfuric acid as a nitrating agent has been studied.
- Ramana,Malik,Parihar
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p. 8681 - 8683
(2007/10/03)
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- Nitration of o-Aminophenol, o-Anisidine, and o-Benzenediazonium Oxide in Sulfuric Acid
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Entering into a reaction in the protonated form, o-aminophenol is nitrated in 80% sulfuric acid at the para and ortho positions to the hydroxy group to afford a mixture of 4-nitro- and 6-nitro-2-aminophenol and is nitrated and sulfonated in concentrated sulfuric acid, whereas o-anisidine is nitrated at the para positions in both cases, converting into 4-nitro-2-aminoanisole. After diazotization of o-aminophenol and subsequent nitration of o-benzenediazonium oxide, a mixture of the same derivatives as in diazotization of the nitration products of o-aminophenol is formed, but the 6-nitro isomer prevails.
- Gorelik,Shteiman,Shner,Romanskii,Kuznetsova
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p. 348 - 352
(2007/10/03)
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- Concerning the baker's yeast (Saccharomyces cerevisiae) mediated reduction of nitroarenes and other N-O containing functional groups
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Nitro- and nitrosoarenes can be reduced using baker's yeast (Saccharomyces cerevisiae) under two distinct sets of conditions, one of which is in fact a well established non-enzymic process. In order to clarify reports in the literature a comparison of the two methods has been made.
- Blackie, Josie A.,Turner, Nicholas J.,Wells, Andrew S.
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p. 3043 - 3046
(2007/10/03)
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- Factors controlling regioselectivity in the reduction of polynitroaromatics in aqueous solution
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Regioselectivities in the bisulfide reduction of 10 polynitroaromatics (PNAs) to monoamine products have been determined; four of these compounds have also been reduced by anoxic sediments in heterogeneous aqueous solution, and the same regioselectivities are observed. Analyses of Austin Model 1- Solvation Model 2 electrostatic potential surfaces for the radical anions of these polynitroaromatic compounds provides a reliable method of predicting the regioselectivity of their reduction. In particular, at their minimum- energy geometries in aqueous solution, it is the more negative nitro group that is selectively reduced. This is consistent with a mechanism where regioselection occurs upon kinetic protonation at the site of maximum negative charge in the radical anion formed after the first electron transfer to the neutral PNA. Inclusion of solvation effects is critical in order to confidently predict the electrostatic preference for the reduction of one nitro group over the others. Sterically uncongested nitroaromatic radical anions have gas-phase geometries in which the nitro group is coplanar with the aromatic ring. However, ortho substituents and solvation effects both oppose this tendency and can lead to nitro groups that are rotated out of the ring plane and pyramidalized.
- Barrows, Susan E.,Cramer, Christopher J.,Truhlar, Donald G.,Elovitz, Michael S.,Weber, Eric J.
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p. 3028 - 3038
(2007/10/03)
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- Regioselective Reduction of Substituted Dinitroarenes Using Baker's Yeast
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A range of substituted dinitroaromatic compounds have been reduced using baker's yeast (Saccharamyces cerevisiae), in some cases with very high selectivity.A model is presented to account for the origin of the selectivity together with a possible mechanism for the reduction.
- Davey, Claire L.,Powell, Lawson W.,Turner, Nicholas J.,Wells, Andrew
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p. 7867 - 7870
(2007/10/02)
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- Pigment compositions for solvent and water-based ink systems and the methods for producing them
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This invention is an azo pigment composition containing a water insoluble metal salt of a water soluble polymer; a method of preparing said composition and ink compositions prepared from said azo pigment compositions.
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- Azo pigment compositions and process for their preparation
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This invention is that of an azo pigment composition containing about 1 to 10 percent by weight of a nonionic alkyl polyglycoside dispersing agent. The polyglycosides useful in the invention have the general formulae: wherein: M is an oxygen, sulfur, nitrogen phosphorous or silicon atom; n is an integer from 8 to 18, preferably 8 to 11 and X represents the number average degree of polymerization having a numerical value from about 1 to about 2. These azo pigment compositions are prepared by conducting the azo pigment coupling reaction in the presence of said alkyl polyglycoside. The resulting pigment exhibit superior application properties in water based ink systems.
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- The search for biochemical photoprobes. III. The photoreactions of 4-nitroveratrole and 2-fluoro-4-nitroanisole with bovine pancreatic ribonuclease A and with model nucleophiles
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The photoreactions of 4-nitroveratrole (NVT) and 2-fluoro-4-nitroanisole (FNA) with bovine pancreatic ribonuclease A (RNAase A) and with model nucleophiles are described. From them it is concluded that 2-fluoro-4-nitrophenyl ethers constitute improved alternative biochemical photoprobes, specially for proteins where a number of good nucleophiles are present.
- Marquet,Rafecas,Cantos,Moreno-Manas,Cervera,Casado,Nogues,Cuchillo
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p. 1297 - 1306
(2007/10/02)
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- RADICAL-ANIONS OF AROMATIC COMPOUNDS. XVI. ELECTRONIC STRUCTURE OF RADICAL-ANIONS AND THE DIRECTION OF PARTIAL REDUCTION OF DISUBSTITUTED DERIVATIVES OF m-DINITROBENZENE: THE RELATIVE EFFECTS OF THE SUBSTITUENTS
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It was shown by means of compounds labeled with the 15N isotope that the radical-anions of a wide range of 1,5-disubstituted 2,4-dinitrobenzenes are in most cases characterized by localization of the density of the unpaired electron at one of the nitro groups.It was concluded that the substituents can be arranged in the following order according to their ability to stabilize the form with the negatively charged nitro group at the para position: CO2- > CH3 Br > Cl N(C2H5)2 > CN > OCH3; CO2- > I.The relative effectiveness of the substituents which stabilize the form of the radical-anions with the negatively charged nitro group at the ortho position was determined theoretically as follows: OCH3 +C5H5 +H(C2H5)2.The position of the substituents in the series given above are determined by the combined effect of such factors as the effective volume, the electronic effect transmitted through the skeleton, the field effect, and the ability to form intramolecular hydrogen bonds.It was shown that the direction of partial reduction of the derivatives of m-dinitrobenzene can be predicted on the basis of data on the electronic structure of their radical-anions, which are probable key intermediates of the processes.
- Uskov, S. I.,Bilkis, I. I.,Shteingarts, V. D.
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- THE NUCLEOPHILIC AROMATIC PHOTOSUBSTITUTIONS OF 4,5-DINITROVERATROLE WITH AMINES. PHOTOREDUCTIONS OF AROMATIC DINITROCOMPOUNDS
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4,5-Dinitroveratrole is effectively photosubstituted by amines with relatively high ionization potential such as methylamine, n-butylamine and ethyl glycinate, but is mainly photoreduced when amines with relatively low ionization potential, such as dimethyl or trimethylamine are used.The photoreduction of several aromatic dinitrocompounds by triethylamine gives nitroanilines.A mechanistic scheme is proposed embracing our photosubstitutions and photoreductions, based on our experimental results and on MINDO/3 calculations of the ground states and the more likely intermediates.
- Marquet, Jorge,Moreno-Manas, Marcial,Vallribera, Adelina,Virgili, Albert,Bertran, Joan,et al.
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p. 351 - 360
(2007/10/02)
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- PARTIAL REDUCTION OF DINITROARENES TO NITROANILINES WITH HYDRAZINE HYDRATE.
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Dinitroarenes containing substituents such as hydroxyl and amine groups could be conveniently reduced with 3 molar equivalents of hydrazine hydrate in presence of Raney nickel catalyst in ethanol/1,2-dichloro-ethane solvent mixture to give a product wherein one of the two nitro groups was reduced to the amino group. The yields of the partial reduction products are good. Under similar conditions alkoxyl substitutes in the o,p-position to the nitro groups were displaced by the hydrazine to give 2,4-dinitrophenyl-hydrazine as the main product. The details of the reduction reaction are described.
- Avyyangar,Kalkote,Lugade,Nikrad,Sharma
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p. 3159 - 3164
(2007/10/02)
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