- Nitration of aromatics with dinitrogen pentoxide in a liquefied 1,1,1,2-tetrafluoroethane medium
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Regardless of the sustainable development path, today, there are highly demanded chemical productions still operating that bear environmental and technological risks inherited from the previous century. The fabrication of nitro compounds, and nitroarenes in particular, is traditionally associated with acidic wastes formed in nitration reactions exploiting mixed acids. However, nitroarenes are indispensable for industrial and military applications. We faced the challenge and developed a greener, safer, and yet effective method for the production of nitroaromatics. The proposed approach comprises the application of an eco-friendly nitrating agent, namely dinitrogen pentoxide (DNP), in the medium of liquefied 1,1,1,2-tetrafluoroethane (TFE) - one of the most non-hazardous Freons. Importantly, the used TFE is not emitted into the atmosphere but is effortlessly recondensed and returned into the process. DNP is obtainedviathe oxidation of dinitrogen tetroxide with ozone. The elaborated method is characterized by high yields of the targeted nitro arenes, mild reaction conditions, and minimal amount of easy-to-utilize wastes.
- Fauziev, Ruslan V.,Kharchenko, Alexandr K.,Kuchurov, Ilya V.,Zharkov, Mikhail N.,Zlotin, Sergei G.
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p. 25841 - 25847
(2021/08/09)
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- 2,6-dimethylnitrobenzene synthesis method
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The invention relates to a method for continuously synthesizing 2,6-dimethylnitrobenzene in a microtubular reactor. The method comprises: (1) immersing a microtubular reactor in an oil bath, wherein an outlet pipe is connected to a liquid-liquid separator, and an inlet pipe is connected to a feeding pump; (2) preparing a mixed acid from 98% nitric acid and 98% sulfuric acid according to a molar ratio of sulfuric acid to nitric acid of 2-4; (3) beating the mixed acid and m-xylene into the microtubular reactor at a certain flow rate by using a two-feeding method, and adjusting the flow rate to achieve a molar ratio of nitric acid to m-xylene of 1.1-1.3; and (4) after completing the reaction, discharging the material to the liquid-liquid separator, carrying out alkali washing on the organic phase, carrying out water washing, and carrying out rectification to obtain the target product. According to the present invention, the reaction kettle is replaced with the microtubular reactor, such that the process is stable, the required space is small, the reaction time is shortened, and the yield of 2,6-dimethylnitrobenzene is improved.
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Paragraph 0015-0026
(2019/05/02)
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- Method and device for preparing methylnitro-benzene by channelization
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The invention discloses a method and a device for preparing methylnitro-benzene by channelization. The device comprises a storage tank, a nitrogen dioxide cylinder, an ozone generator, a flow pump, agas flowmeter, a reaction pipeline filled with a catalyst, a mixing pipeline, two T-shaped mixed joints, a cooling system, a heating system, a back pressure valve and a receiving tank. The method specifically comprises the following steps: opening the cooling system and the heating system; opening the ozone generator; arranging the flow pump and the gas flowmeter; and mixing raw materials liquid methyl benzene and nitrogen dioxide through the first T-shaped mixing joint and feeding the mixture into the mixing pipeline, then mixing the mixture with ozone in the second T-shaped mixing joint, feeding the mixture into the reaction pipeline filled with the catalyst for a nitrifying reaction, and post-treating a reaction liquid to obtain methylnitro-benzene. The method is controlled precisely and automatically, and is simple to operate, mild in reaction condition, simple in post treatment, quick to transfer mass and heat, high in safety and good in economical benefit.
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-
Paragraph 0050; 0051; 0052
(2019/02/04)
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- Hydrophobic WO3/SiO2 catalyst for the nitration of aromatics in liquid phase
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WO3/SiO2 solid acid catalyst synthesized using sol gel method has shown promising activity (up to 65% conversion) for aromatic nitration in liquid phase using commercial nitric acid (70%) as nitrating agent without using any sulfuric acid. The water formed during the reaction as well as water from dilute nitric acid (70%) was removed azeotropically, however due to the hydrophilic nature of the catalyst, some water gets strongly adsorbed on catalyst surface forming a barrier layer between catalyst and organics. This prevents effective adsorption of substrate on catalyst surface for its subsequent reaction. To improve the activity further, the hydrophilic/hydrophobic nature of the catalyst was altered by post modification by grafting with commercial short chain organosilane (Dynasylan 9896). The modified 20% WO3/SiO2 catalyst when used for o-xylene nitration in liquid phase, showed significant increase in the conversion from 65% to 80% under identical reaction conditions. Catalyst characterization revealed decrease in the surface area of 20% WO3/SiO2 from 356 m2/g to 302 m2/g after grafting with Dynasylan 9896. The fine dispersion of WO3 particles (2–5 nm) on silica support was not affected due to modification. NMR and FTIR study revealed the decrease in surface hydroxyl groups imparting hydrophobicity to the catalyst. Interestingly the total acidic sites of the catalyst remained almost unaltered (0.54 mmol NH3/g) even after modification. Even though, the acidity and other characteristics of the catalyst did not change appreciably, there was a considerable increase in the o-xylene conversion which can be ascribed to the hydrophobic nature of the catalyst.
- Kulal,Kasabe,Jadhav,Dongare,Umbarkar
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p. 105 - 113
(2019/02/15)
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- Regioselective nitration of m-xylene catalyzed by zeolite catalyst
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Nitration with nitric acid and acetic anhydride via acetyl nitrate as nitrating species is efficient with the substrate m-xylene as solvent. Zeolite Hβ with an SiO2/Al2O3 ratio of 500 was found to be the most active of the catalysts tried both in yield and regioselectivity in the nitration of m-xylene. The molecular volume of the reactants was calculated with the Gaussian 09 program at the B3LYP/6-311+G(2d, p) level and compared with the size of the zeolite Hβ channels. A range of other substrates were subjected to the nitrating system under the same conditions as those optimized for m-xylene and excellent selectivity was obtained.
- Dong, Xiongzi,Peng, Xinhua
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p. 1122 - 1128
(2016/01/15)
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- Regioselective preparation of 4-nitro-o-xylene using nitrogen dioxide/molecular oxygen over zeolite catalysts. remarkable enhancement of para-selectivity
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In the presence of molecular oxygen and zeolite H-β with Si/Al 2 = 500, o-xylene reacted regioselectively with liquid nitrogen dioxide at 35 °C to yield mononitro-o-xylenes as the main product, where the 4-nitro-o-xylene isomer predominated up to 89% and the 4-nitro-/3-nitro-o- xylene isomer ratio improved to 7.8. The process is eco-friendly, less expensive, and the zeolite could be easily regenerated by a simple workup to afford results similar to those obtained with the fresh catalyst.
- Liu, Hongtao,Ji, Cheng,Dong, Xiongzi,Peng, Xinhua,Shi, Chunjie
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supporting information
p. 817 - 819
(2014/06/23)
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- Regioselective nitration of aromatics with nanomagnetic solid superacid SO42-/ZrO2-MxOy-Fe 3O4 and its theoretical studies
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A series of micro- and nanosulfated zirconia loaded on Fe3O 4 or other metal oxides (SO42-/ZrO 2-MxOy-Fe3O4 (M=Ti 4+, V5+, and Zn2+)) was prepared, characterized, and used in nitration. The nitration conditions with these solid superacids were then optimized to achieve the best regioselectivity and improve the performances of the catalysts as well. In the experimental results, SZTF (SO42-/ZrO2-TiO2-Fe 3O4) showed excellent catalytic activity and it increased the surface area of SO42-/ZrO2 by up to 15 %. The increase not only facilitated the generation of NO2+, but also provided more opportunities for metal ions to interact with aromatic compounds. With chlorobenzene as substrate, theoretical research on its geometric parameters, electron clouds, and electron spin density was used to investigate the interaction between transition metals and chlorobenzene.
- Wang, Peng Cheng,Zhu, Jie,Liu, Xiang,Lu, Ting Ting,Lu, Ming
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p. 310 - 317
(2013/08/23)
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- Preparation, catalytic performance and theoretical study of porous sulfated binary metal oxides shell (SO42 -/M1xO y-M2xOy) using pollen grain templates
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Porous micro-sized particles of binary metal oxide (SO4 2 -/M1xOy-M2xOy) shell were prepared by template-directed synthesis method employing HCl-treated pollen grains. With 150 m2/g high surface area, these solid acids could provide more acid sites and thus obtain better catalytic activity. Using aromatic nitration as the typical reaction, their catalytic performances were evaluated and showed a significant improvement in both conversion and regioselectivity. Then, with chlorobenzene as substrate, theoretical studies were performed to investigate the interaction between transition metals and chlorobenzene. The results showed that the excellent para-selectivity was closely relative to the metal ion in these solid acids.
- Wang, Peng Cheng,Yao, Kai,Zhu, Jie,Liu, Xiang,Lu, Ting Ting,Lu, Ming
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- Preparation of heteropoly acid based amphiphilic salts supported by nano oxides and their catalytic performance in the nitration of aromatics
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A series of Keggin heteropoly acid anion based amphiphilic salts supported by nano oxides were synthesized and used as catalysts in the nitration of aromatic compounds with HNO3. The reaction conditions in the nitration of toluene were optimized and both 92.6% conversion and good para selectivity (ortho:para = 1.09) were obtained.
- Wang, Peng-Cheng,Yao, Kai,Lu, Ming
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p. 2197 - 2202
(2013/03/14)
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- METHOD FOR PREPARATION OF MONONITRATED AROMATIC COMPOUNDS
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The invention discloses a method for preparation of mononitrated aromatic compounds in a liquid-liquid biphasic solvent system with aqueous nitric acid as one phase and ionic liquids (ILs) as the second phase, wherein the nitric acid is continuously exchanged during the reaction, or the water, that is generated during the reaction, is removed by addition of NO2 and an oxidizing agent during the reaction.
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Page/Page column 23-24
(2012/12/13)
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- Ethylammonium nitrate (EAN)/Tf2O and EAN/TFAA: Ionic liquid based systems for aromatic nitration
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Acting as in situ sources of triflyl nitrate (TfONO2) and trifluoroacetyl nitrate (CF3COONO2), the EAN/Tf 2O and EAN/TFAA systems, generated via metathesis in the readily available ethylammonium nitrate (EAN) ionic liquid as solvent, are powerful electrophilic nitrating reagents for a wide variety of aromatic and heteroaromatic compounds. Comparative nitration experiments indicate that EAN/Tf2O is superior to EAN/TFAA for nitration of strongly deactivated systems. Both systems exhibit low substrate selectivity (K T/KB = 5-10) in (Figure presented) between values reported for covalent nitrates and preformed nitronium salts.
- Aridoss, Gopalakrishnan,Laali, Kenneth K.
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experimental part
p. 8088 - 8094
(2011/11/13)
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- Regioselective nitration of aromatics under phase-transfer catalysis conditions
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Mononitration of aromatics was performed in a two-phase system using phase-transfer catalyst. The most advantageous conditions for the nitration were determined (temperature, reaction time, the type and amount of phase transfer catalyst, nitrification strength of the nitro-sulfuric acid). From the results, a significant improvement in the selectivity and conversion of the nitration of xylene was observed: the ratio of 4-nitro-m-xylene to 2-nitro-m-xylene was unprecedented increased up to 91.3%:7.7%, the ratio of 4-nitro-o-xylene to 3-nitro-o-xylene was also increased to 71.1%:27.2%; both the conversions were over 96%.
- Wang, Peng-Cheng,Lu, Ming,Zhu, Jie,Song, Yan-Ming,Xiong, Xian-Feng
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experimental part
p. 42 - 47
(2012/01/15)
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- Selective oxidation of aromatic amines to nitro derivatives using potassium iodide-tert-butyl hydroperoxide catalytic system
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The direct oxidation of aromatic primary amines to the corresponding nitro compounds selectively in 47-98% yields has been achieved by using potassium iodide as catalyst and tert-butyl hydroperoxide as the external oxidant. The present catalytic system works well for both electron-rich and electron-poor substrates.
- Reddy, K. Rajender,Maheswari, C. Uma,Venkateshwar,Kantam, M. Lakshmi
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supporting information; experimental part
p. 93 - 96
(2009/08/07)
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- Supported bismuth(III) nitrate on silica sulfuric acid as useful reagent for nitration of aromatic compounds under solvent-free conditions
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A number of aromatic compounds were nitrated to the corresponding nitroaromatic derivatives with the use of supported bismuth(III) nitrate on silica sulfuric acid under solvent-free conditions.
- Hajipour,Zarei,Ruoho
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p. 1493 - 1495
(2007/10/03)
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- Lanthanide(III) nosylates as new nitration catalysts
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Lanthanide(III) nosylates are novel, recyclable catalysts prepared from the noncorrosive and inexpensive p-nitrotoluenesulfonic acid and the corresponding lanthanide(III) oxide. With 5-10% catalyst loading, atom economic nitration of simple aromatic compounds was achieved in good to high yields.
- Parac-Vogt, Tatjana N.,Binnemans, Koen
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p. 3137 - 3139
(2007/10/03)
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- Electrophilic Aromatic Nitration Using a Mixed Catalyst of Lithium, Molybdenum, Ytterbium on Silica Gel
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A novel mixed catalyst of LiClO4 (15% w/w), Yb(OPf)3 (15% w/w, Pf = perfluorooctanesulfonyl), MoO3 (15% w/w) on silica gel for electrophilic aromatic nitration reaction has been explored. The nitration reactions were accomplished by this mixed catalyst and nitric acid under solvent-free conditions. Moreover, the mixed catalyst can be easily recovered from the aqueous layer by heating in an oven and reused for the next nitration reaction.
- Shi, Min,Cui, Shi-Cong
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p. 1329 - 1333
(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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- Counterion effects in indium-catalysed aromatic electrophilic substitution reactions
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Indium(III) triflamide (In(NTf2)3) has been prepared in high yield and has been demonstrated to be an efficient, recoverable catalyst for a range of aromatic electrophilic substitution reactions. When compared to other indium(III) complexes, anomalous reactivities suggest a non-innocent role for the counterion in the studied processes.
- Frost, Christopher G,Hartley, Joseph P,Griffin, David
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p. 4789 - 4791
(2007/10/03)
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- Scandium(III) trifluoromethanesulfonate catalyzed aromatic nitration with inorganic nitrates and acetic anhydride
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The rare earth metal(III) trifluoromethanesulfonate (rare earth metal(III) triflate, RE(OTf)3) was found to be an efficient catalyst for aromatic nitration with carboxylic anhydride-inorganic nitrate as the nitrating agent. In the presence of a catalytic amount of RE(OTf)3, the nitration of substituted benzenes proceeded to afford the corresponding nitrobenzenes. Especially, scandium(III) trifluoromethanesulfonate (scandium(III) triflate, Sc(OTf)3) is the most active catalyst among our tested Lewis acids. It was also found that acetic anhydride-Al(NO 3) · 9H2O is the most active nitrating agent in this system.
- Kawada, Atsushi,Takeda, Shigemitsu,Yamashita, Kazumi,Abe, Hitoshi,Harayama, Takashi
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p. 1060 - 1065
(2007/10/03)
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- Bis(dealkoxycarbonylation) of nitroarylmalonates: A facile entry to alkylated nitroaromatics
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A simple approach to alkylated nitroaromatics from substituted nitroaryl malonic esters by double decarboxylation is detailed.
- Gurjar,Reddy,Murugaiah,Murugaiah
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p. 1659 - 1661
(2007/10/03)
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- Nitro compound-reducing process
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PCT No. PCT/EP96/03415 Sec. 371 Date May 23, 1998 Sec. 102(e) Date May 23, 1998 PCT Filed Aug. 2, 1996 PCT Pub. No. WO97/07087 PCT Pub. Date Feb. 27, 1997The invention concerns a process for the reduction of nitro groups to amino groups, characterized that a nitro compound is reacted with hydrogen in the presence of an aqueous solution of a water-soluble metal catalyst of the formula M (L)n(Y)m wherein M is ruthenium, rhodium, nickel, or palladium; L, is a water soluble ligand; Y is a further ligand or an alkaline earth ion; n is 1, 2, 3, or 4; and m is 0, 1, or 2.
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- Kinetics and mechanism of nitrosation of toluene, o-xylene, and m-xylene in trifluoroacetic acid, or in acetic-sulfuric acid mixtures, under nitric oxide
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The title reactions give good yields with m-xylene, and modest yields with toluene and o-xylene which are successfully directly nitrosated for the first time. The advantages of purging with nitric oxide are demonstrated and discussed. The kinetics have been successfully interpreted in terms of a mechanism in which both the aromatic substrate and the nitrosoaromatics form, reversibly, complexes with nitrosonium ion. The nitrosoaromatics are unstable under the acid conditions and the method is successful only because of the protective complexation with the nitrosonium ion.
- Atherton, John H.,Moodie, Roy B.,Noble, Darren R.
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p. 699 - 705
(2007/10/03)
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- Reductive coupling of nitrobenzene or nitrobenzenes substituted on the nucleus to give the corresponding azobenzenes and azoxybenzenes by means of redox catalysts
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Nitrobenzene or a nitrobenzene substituted on the nucleus is subjected to reductive coupling to give the corresponding azobenzene and azoxybenzene under heterogeneous catalysis with substantial avoidance of overreduction to aniline derivatives by means of a redox catalyst in its reduced or partly reduced form, the redox catalyst containing at least one active metal component capable of a change of oxidation state.
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- Lanthanide(III) triflates as recyclable catalysts for atom economic aromatic nitration
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Lanthanide(III) triflates catalyse (1-10 mol%) the nitration of a range of simple aromatic compounds in good to excellent yield using stoichiometric quantities of 69% nitric acid; the only by-product is water and the catalyst can be readily recycled by simple evaporation.
- Waller, Francis J.,Barrett, Anthony G. M.,Braddock, D. Christopher,Ramprasad, Dorai
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p. 613 - 614
(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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- Method for preparing aromatic secondary amino compound
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Disclosed are (1) a method for preparing an aromatic secondary amino compound which comprises reacting an N-cyclohexylideneamino compound in the presence of a hydrogen moving catalyst and a hydrogen acceptor by the use of a sulfur-free polar solvent and/or a cocatalyst, and (2) a method for preparing an aromatic secondary amino compound which comprises reacting cyclohexanone or a nucleus-substituted cyclohexanone, an amine and a nitro compound corresponding to the amine in a sulfur-free polar solvent in the presence of a hydrogen moving catalyst, a cocatalyst being added or not added. In a further aspect, a method is provided for the preparation of aminodiphenylamine by reacting phenylenediamine and cyclohexanone in the presence of a hydrogen transfer catalyst in a sulfur-free polar solvent while using nitroaniline as a hydrogen acceptor.
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- Method for preparing aromatic secondary amino compound
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Disclosed are (1) a method for preparing an aromatic secondary amino compound which comprises reacting an N-cyclohexylideneamino compound in the presence of a hydrogen moving catalyst and a hydrogen acceptor by the use of a sulfur-free polar solvent and/or a cocatalyst, and (2) a method for preparing an aromatic secondary amino compound which comprises reacting cyclohexanone or a nucleus-substituted cyclohexanone, an amine and a nitro compound corresponding to the amine in a sulfur-free polar solvent in the presence of a hydrogen moving catalyst, a cocatalyst being added or not added.
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-
- Thermal and Photochemical Nitration of Aromatic Hydrocarbons with Nitrogen Dioxide
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Aromatic hydrocarbons (ArH) are readily nitrated by nitrogen dioxide (NO2) in dichloromethane at room temperature and below (in the dark).The red colors, transiently observed, arise from the metastable precursor complex NO3(1-), which is formed in the prior disproportionation of nitrogen dioxide induced by the aromatic donor (eq 7).The deliberate irradiation of the diagnostic (red) charge-transfer absorption band (hνCT) of NO3(1-) at low temperatures results directly in aromatic nitration, even at -78 deg C, where the thermal nitration is too slow to complete.The mechanism of the photochemical (charge-transfer) nitration is established by time-resolved laser spectroscopy to proceed via the aromatic cation radical (ArH.+) formed spontaneously upon the charge-transfer excitation of NO3(1-) in Scheme 1.The related thermal activation of NO3(1-) derives from the adiabatic electron transfer that produces the same radical pair as the reactive intermediate in Scheme 3.The close relationship between the thermal/photochemical nitrations with nitrogen dioxide and those conventionally carried out with nitric acid (in the presence of nitrous acid) is delineated by Scheme 4.
- Bosch, E.,Kochi, J. K.
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p. 3314 - 3325
(2007/10/02)
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- Ozone-mediated Nitration of Alkylbenzenes and Related Compounds with Nitrogen Dioxide
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In the presence of ozone, nitrogen dioxide exhibits a strong nitrating ability for alkylbenzenes at low temperatures, converting them into the corresponding nitro derivatives in high yield.The addition of a protonic acid as catalyst enhances considerably the ability of this nitrating system and leads to a good yield of polynitro compounds.The reaction is clean and proceeds rapidly without any accompanying side-chain substitution or aryl-aryl coupling.It shows no kinetic dependence on the concentration of substrates and, as far as can be judged from relative reactivities and isomer distributions of products, it gives the appearance of being an electrophilic aromatic process.A possible role for nitrogen trioxide has been suggested as the initial electrophilic agent for the nitration of alkylbenzenes.
- Suzuki, Hitomi,Murashima, Takashi,Kozai, Iku,Mori, Tadashi
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p. 1591 - 1598
(2007/10/02)
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- GAS-PHASE NITRATION OF AROMATIC COMPOUNDS AT ZEOLITES WITH NITROGEN DIOXIDE
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The gas-phase nitration of benzene, toluene, ethylbenzene, chlorobenzene, and isomeric xylenes at various zeolites was studied. The dependence of the isomeric composition of the obtained products on the reaction conditions was investigated. A possible reaction mechanism is proposed.
- Salakhutdinov, N. F.,Ione, K. G.,Kobzar', E. A.,Malysheva, L. V.
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p. 457 - 466
(2007/10/02)
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- The Rearrangement of Aromatic Compounds. Part 3. The Mechanism of Rearrangement of Nitrated Hydrocarbons in Trifluoromethanesulphonic Acid
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1,3-Dialkyl-2-nitrobenzenes (C6H3R2NO2; R = Me, Et, and Pri) rearrange in trifluoromethanesulphonic acid to the corresponding 4-nitro derivatives; with R = Et, this reaction is accompanied by dehydration to 7-ethyl-3-methylanthranil.The reaction rate increases markedly with the size of the alkyl group; with R = Me, the reaction was studied at 110 deg C but, with R = Pri, temperatures of 36-54 deg C were used.The studies with R = Me show the reaction to be first-order with the rate coefficients (k1) increasing rapidly with the acidity of the solution 1)/d(-H0)> = 1.45, decreasing with acidity to o.49.Double-labelling experiments with 1H and 15N show the reaction to be intramolecular. 1,2,4-Trimethyl-3-nitrobenzene also rearranges under these conditions to give mainly the 5-nitro isomer.The above results are discussed in terms of a direct 1,3-shift of the nitro group.
- Bullen, John V.,Ridd, John H.,Sabek, Omaima
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p. 1681 - 1685
(2007/10/02)
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- THE CYCLISATION AND REARRANGEMENT OF THE NITRO DERIVATIVES OF AROMATIC HYDROCARBONS IN TRIFLUOROMETHANESULPHONIC ACID
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A number of the nitro derivatives of aromatic hydrocarbons undergo reactions in trifluoromethanesulphonic acid at ca. 100 deg C in which either the nitro group undergoes a 1,3-rearrangement or cyclisation occurs to form an anthranil.The rates and product composition have been determined for reactions in which the subsituents ortho to the nitro group are methyl or ethyl.For the rearrangement reaction to occur, it appears necessary that the nitro group should be initially between two alkyl substituents.The cyclisation reaction is significant only when one of the ortho-substituents is an ethyl group.
- Bullen, John V.,Ridd, John H.,Sabek, Omaima
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p. 291 - 296
(2007/10/02)
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- THE SELECTIVITY OF ELECTROPHILIC AROMATIC NITRATION AND THE EFFECT OF THE ORGANIC SOLVENTS
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The nitrating agent prepared by mixing Bu4NNO3 and (CF3CO)2O has been used to nitrate in homogeneous conditions eight aromatic substrates, ranging in reactivity from benzene to mesitylene, in several organic solvents.From competitive kinetic experiments and glc analysis, partial rate factors were obtained.The nature of the solvent significantly affects selectivity in the whole activation range.Selectivity was quantitatively measured by the selectivity factor for toluene, and, more properly, by the slopes in the correlations between log values of partial rate factors in a given solvent and the corresponding values in a reference solvent.Good correlations were obtained also including ortho positions and polysubstituted substrates, and the following order of relative selectivity could be established: MeNO2 MeCN /= sulfolane CH2ClCH2Cl CH2Cl2 /= EtOAc /= i-PrBr = n-BuCl = n-BuBr /= CHCl3.Correlation between partial rate factors has been extended to compare the selectivity of different nitrating agents in the same solvent, and the method can be used to ascertain whether the same electrophilic species actually operates in the two systems.
- Masci, Bernardo
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p. 2719 - 2730
(2007/10/02)
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- Electron-Transfer Substitution Reactions: Facilitation by the Cyano Group
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It is now clear that a cyano group facilitates electron-transfer substitution reactions.Of particular interest is the demonstration that electron-transfer chain substitution at a saturated carbon atom has been achieved in the absence of a nitro group.
- Kornblum, Nathan,Fifolt, Michael J.
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p. 1311 - 1322
(2007/10/02)
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- REGIOSELECTIVE NITRATION OF AROMATIC HYDROCARBONS BY METALLIC NITRATES ON THE K10 MONTMORILLONITE UNDER MENKE CONDITIONS
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Aromatic hydrocarbons are nitrated with good regioselectivities by clay-supported cupric nitrate in the presence of acetic anhydride.The procedure commends itself by its simplicity and gives useful yields (75-98percent).In each case, the predominant product can be predicted by consideration of the Hueckel HOMO for the aromatic ring.
- Laszlo, Pierre,Vandormael, Joseph
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p. 1843 - 1846
(2007/10/02)
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- Nitroacetylene Equivalents. Preparation and Cycloadditions of 2-Phenylsulphinyl-1-nitroalkenes
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β-Phenylsulphinyl-nitro-alkenes (7) are readily prepared from acyl imidazoles and react as nitroacetylene equivalents in Diels-Alder reactions to give good yields of cycloadducts and their further products.
- Jung, Michael E.,Grove, David D.
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p. 753 - 755
(2007/10/02)
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- The Rearrangement of Aromatic Nitro-compounds in Strongly Acid Media
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2-Nitro-m-xylene and a number of nitrophenols undergo a 1,3-nitro-group rearrangement in trifluoromethanesulphonic acid at 70-110 deg C.
- Barrow, Peter,Bullen, John V.,Dent, Andrea,Murphy, Timothy,Ridd, John H.,Sabek, Omaima
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p. 1649 - 1650
(2007/10/02)
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- Reactions of Cerium(IV) Ammonium Nitrate with Aromatic Compounds in Acetonitrile. Part 2. Nitration; Comparison with Reactions of Nitric acid
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The nitration of benzene and a number of alkylbenzenes by cerium(IV) ammonium nitrate in acetonitrile shows the same intra- and inter-molecular selectivity as nitration with nitric acid under the same conditions but the extent of the other products formed in the two sets of reactions is very different.Nitration by cerium(IV) ammonium nitrate (but not side-chain substitution) is suppressed by the addition of water.The results suggest that these nitration reactions by cerium(IV) ammonium nitrate occur through the intermediate formation of a nitronium ion from the cerium(IV) complex but the order with recpect to the aromatic compound shows that this nitronium ion must then be formed in the presence of the aromatic substrate as a 'spectator'.The relative reactivities with respect to benzene in the nitration of anisole and naphthalene are much greater than those observed in nitration by nitric acid and, with both, the isomer proportions are also anomalous.
- Dinctuerk, Suphi,Ridd, John H.
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p. 965 - 970
(2007/10/02)
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- Aromatic Substitution. 471. Acid-Catalyzed Transfer Nitration of Aromatics with N-Nitropyrazole, a Convenient New Nitrating Agent
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N-Nitropyrazole in the presence of Lewis or Bronsted acid catalysts was found to be an effective transfer nitrating agent for aromatic substrates.The nature of the acid catalyst both substrate and positional selectivies of the nitration of alkylbenzenes.No relationship was found between substrate and positional selectivities, which are considered to be determined in two separate steps.
- Olah, George A.,Narang, Subhash C.,Fung, Alexander P.
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p. 2706 - 2709
(2007/10/02)
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- Nitration of Some 2-Iodo-1,3,5-trialkylbenzenes. Competition between Nitrodeprotonation and Nitrodeiodination. Discussion of Steric Effects
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The nitration of some 2-iodo-1,3,5-trialkylbenzenes in a nitric acid-nitromethane medium has been investigated.The nitronium ion is found to replace three different substituents competitively, hydrogen, iodine or, to a smaller extent, an alkyl group.The expelled iodonium ion forms some iodo electrophile, which attacks the substrate in a secondary reaction and gives rise to a 2,4-diiodo-1,3,5-trialkylbenzene, which is then nitrodeiodinated.The product of this last reaction and that of the primary nitrodeprotonation are identical, which makes a careful kinetic analysis necessary.The true ratio between the nitrodeiodination and the nitrodeprotonation rate constants is determined via a simulation of the course of the total reaction.The rate ratios have been determined for eight iodotrialkylbenzenes with different steric properties and found to vary with the degree of branching in the alkyl substituents.The nitrodeiodination is favoured when the branching is in the α-position of each chain and disfavoured when the branching is in the β-position.The nitrodeiodination-nitrodeprotonation rate ratio is invariant with the medium, and the product-determinig transition states are thus similar for the two reactions.
- Johansson, Ingegaerd
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p. 723 - 730
(2007/10/02)
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- Aromatic Substitution. 45. Transfer Nitration of Aromatic with N-Nitropyridinium and Quinolinium Ions
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The transfer nitration of aromatics with various N-nitropyridinium and quinolinium salts (PF6- or BF4-) was studied.The nitroanions were found to take place via a nicleophilic displacement pathway, involving the N-nitropyridinium ions themselves and not free nitronium ion.Steric factors were, however, shown to play an insignificant role in determining the positional selectivity of nitration.Positional and substrate selectivities were found to be independent of one another and are suggested to be determined in two separate steps.
- Olah, George A.,Narang, Subhash C.,Olah, Judith A.,Pearson, Ronald L.,Cupas, Chris A.
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p. 3507 - 3510
(2007/10/02)
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