- Eco-Friendly Methodology for the Formation of Aromatic Carbon–Heteroatom Bonds by Using Green Ionic Liquids
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A new sustainable method is reported for the formation of aromatic carbon–heteroatom bonds under solvent-free and mild conditions (no co-oxidant, no strong acid and no toxic reagents) by using a new type of green ionic liquid. The bromination of methoxy arenes was chosen as a model reaction. The reaction methodology is based on only using natural sodium bromine, which is transformed into an electrophilic brominating reagent within an ionic liquid, easily prepared from the melted salt FeCl3 hexahydrate. Bromination reactions with this in-situ-generated reagent gave good yields and excellent regioselectivity under simple and environmentally friendly conditions. To understand the unusual bromine polarity reversal of sodium bromine without any strong oxidant, the molecular structure of the reaction medium was characterised by Raman and direct infusion electrospray ionisation mass spectroscopy (ESI-MS). An extensive computational investigation using density functional theory methods was performed to describe a mechanism that suggests indirect oxidation of Br? through new iron adducts. The versatility of the methodology was successively applied to nitration and thiocyanation of methoxy arenes using KNO3 and KSCN in melted hexahydrated FeCl3.
- Richards, Kenza,Petit, Eddy,Legrand, Yves-Marie,Grison, Claude
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supporting information
p. 809 - 814
(2020/11/30)
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- Electrochemical Nitration with Nitrite
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Aromatic nitration has tremendous importance in organic chemistry as nitroaromatic compounds serve as versatile building blocks. This study represents the electrochemical aromatic nitration with NBu4NO2, which serves a dual role as supporting electrolyte and as a safe, readily available, and easy-to-handle nitro source. Stoichiometric amounts of 1,1,1-3,3,3-hexafluoroisopropan-2-ol (HFIP) in MeCN significantly increase the yield by solvent control. The reaction mechanism is based on electrochemical oxidation of nitrite to NO2, which initiates the nitration reaction in a divided electrolysis cell with inexpensive graphite electrodes. Overall, the reaction is demonstrated for 20 examples with yields of up to 88 %. Scalability is demonstrated by a 13-fold scale-up.
- Blum, Stephan P.,Nickel, Christean,Sch?ffer, Lukas,Karakaya, Tarik,Waldvogel, Siegfried R.
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p. 4936 - 4940
(2021/10/25)
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- Synthesis of thioethers, arenes and arylated benzoxazoles by transformation of the C(aryl)-C bond of aryl alcohols
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Transformation of aryl alcohols into high-value functionalized aromatic compounds by selective cleavage and functionalization of the C(aryl)-C(OH) bond is of crucial importance, but very challenging by far. Herein, for the first time, we report a novel and versatile strategy for activation and functionalization of C(aryl)-C(OH) bonds by the cooperation of oxygenation and decarboxylative functionalization. A diverse range of aryl alcohol substrates were employed as arylation reagents via the cleavage of C(aryl)-C(OH) bonds and effectively converted into corresponding thioether, arene, and arylated benzoxazole products in excellent yields, in a Cu based catalytic system using O2 as the oxidant. This study offers a new way for aryl alcohol conversion and potentially offers a new opportunity to produce high-value functionalized aromatics from renewable feedstocks such as lignin which features abundant C(aryl)-C(OH) bonds in its linkages.
- Chen, Bingfeng,Han, Buxing,Liu, Mingyang,Meng, Qinglei,Song, Jinliang,Zhang, Pei,Zhang, Zhanrong
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p. 7634 - 7640
(2020/08/14)
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- Sequential Cleavage of Lignin Systems by Nitrogen Monoxide and Hydrazine
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The cleavage of representative lignin systems has been achieved in a metal-free two-step sequence first employing nitrogen monoxide for oxidation followed by hydrazine for reductive C?O bond scission. In combining nitrogen monoxide and lignin, the newly developed valorization strategy shows the particular feature of starting from two waste materials, and it further exploits the attractive conditions of a Wolff-Kishner reduction for C?O bond cleavage for the first time. (Figure presented.).
- Altmann, Lisa-Marie,Heinrich, Markus R.,Hofmann, Dagmar,Hofmann, Laura Elena,Prusko, Lea
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- Base promoted peroxide systems for the efficient synthesis of nitroarenes and benzamides
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A useful and efficient approach for the synthesis of nitroarenes from several aromatic amines (including heterocycles) using peroxide and base has been developed. This oxidative reaction is very easy to handle and afforded the products in good yields. Formation of benzamides from benzylamine was also successfully carried out with this metal-free catalytic system in good to excellent yields.
- Gupta, Sampa,Ansari, Alisha,Sashidhara, Koneni V.
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supporting information
(2019/09/07)
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- Nitration method for aryl phenol or aryl ether derivative
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The invention relates to a nitration method for an aryl phenol or aryl ether derivative. The method comprises the steps of stirring an aryl phenol or aryl ether compound, nitrate, trimethylchlorosilane (TMSCl) and a copper salt in an acetonitrile solution in air at room temperature, simultaneously, monitoring extent of reaction through a TLC dot plate, removing a solvent from a mixture by a rotaryevaporator after a substrate is consumed completely, and carrying out purification through a silica-gel column, thereby obtaining a nitroolefin derivative. Meanwhile, the selective mono-nitration orbis-nitration of the substrate can be achieved through controlling equivalent weight of the nitrate. Compared with the prior art, the nitration method disclosed by the invention has the advantages that the consumption of strong-acid substances is avoided, the reaction conditions are mild, the yield is high, the applicable range of the substrate is wide, reaction activity is free of obvious attenuation after an amplified reaction, and an excellent yield is still obtained, so that the method has an obvious industrial application value.
- -
-
Paragraph 0050-0055; 0092-0094
(2020/01/03)
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- Iodine(III)-Catalyzed Electrophilic Nitration of Phenols via Non-Br?nsted Acidic NO2+ Generation
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The first catalytic procedure for the electrophilic nitration of phenols was developed using iodosylbenzene as an organocatalyst based on iodine(III) and aluminum nitrate as a nitro group source. This atom-economic protocol occurs under mild, non-Br?nsted acidic and open-flask reaction conditions with a broad functional-group tolerance including several heterocycles. Density functional theory (DFT) calculations at the (SMD:MeCN)Mo8-HX/(LANLo8+f,6-311+G) level indicated that the reaction proceeds through a cationic pathway that efficiently generates the NO2+ ion, which is the nitrating species under neutral conditions.
- Juárez-Ornelas, Kevin A.,Jiménez-Halla, J. Oscar C.,Kato, Terumasa,Solorio-Alvarado, César R.,Maruoka, Keiji
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supporting information
p. 1315 - 1319
(2019/03/07)
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- Coordinative interaction between nitrogen oxides and iron-molybdenum POM Mo72Fe30
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The process of adsorption of nitrogen monoxide and dioxide by the giant Keplerate nanocluster Mo72Fe30 was studied in detail under ambient conditions and air/argon atmosphere. The obtained Raman and IR spectra showed that the coordination of NOx to the Mo72Fe30 leads to the formation of nitrate ions by sharing the bridged or terminal oxygen in FeO6 polyhedra with the adsorbed NO2 molecules. In accordance with elemental analysis and X-ray photoelectron spectroscopy, the composition of the produced complex was found to be [POM-(NO2)x]·(NO2)y (where x = 6, y = 14 ± 3). The carried out thermal analysis revealed the significant influence of NOx coordination in the release of water molecules and decomposition of the constitutional acetate ligands for Mo72Fe30. Furthermore, the performed measurements of the temperature dependency of the electron paramagnetic resonance spectra for the pure nanocluster and that treated with NO2 allowed us to draw up a conclusion about the delocalization of weak-bonded NO2 molecules in the pores of the Mo72Fe30 crystal at 25 °C. The opposite situation was observed under cryogenic temperatures. The localization of NO2 molecules occurs resulting in the distortion of FeO6 octahedra towards tetrahedral symmetry accompanied with the appearance of the signal at g-factor 4.3. The produced complex compound [POM-(NO2)x]·(NO2)y possesses sufficient NO2 capacity, water solubility and pH-dependant decomposition; these are important properties of a potential NOx donor, which can be hypothetically applied in biomedicine.
- Grzhegorzhevskii, Kirill V.,Tonkushina, Margarita O.,Fokin, Andrei V.,Belova, Ksenia G.,Ostroushko, Alexander A.
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p. 6984 - 6996
(2019/05/27)
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- Direct nitration method of electron-enriched aromatic hydrocarbons
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The invention discloses a direct nitration method of electron-enriched aromatic hydrocarbons, and belongs to the field of organic synthesis. The direct nitration method is a novel green free radical nitration method; aromatic hydrocarbons are taken as raw materials, acetonitrile, dichloromethane, chloroform, or acetone is taken as a reaction solvent, at room temperature conditions, the raw materials and green nitration reagent tert-butyl nitrite (TBN) are subjected to free radical nitration so as to obtain nitro-aromatic compounds. According to the direct nitration method, no metal is adoptedin reaction, tert-butyl nitrite is directly adopted in nitration reaction. Electron-donating groups such as OMe are introduced, the electron density of aromatic compounds is increased, the nitration reaction possibility is increased. The using amount of tert-butyl nitrite is reduced; only a product and tert-butyl alcohol are generated, environment pollution is reduced. The direct nitration methodis promising in application prospect in the field of nitro-aromatic compound synthesis, green nitration is realized, and a novel idea is provided for large-scale industrialized nitro-aromatic compoundproduction.
- -
-
Paragraph 0057-0059
(2018/10/02)
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- Rapid aerobic iodination of arenes mediated by hypervalent iodine in fluorinated solvents
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Arenes are rapidly converted to the corresponding iodides by aerobic oxidative iodination at room temperature by treatment with iodine and catalytic quantities of nitrous acid in a fluorinated solvent. Dichloroiodic acid is proposed as the actual iodination reagent.
- Iskra, Jernej,Murphree, S. Shaun
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supporting information
p. 645 - 648
(2017/01/28)
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- Novel Aryl-Modified Benzoylamino-N-(5,6-dimethoxy-1H-benzoimidazol-2-yl)-heteroamides as Potent Inhibitors of Vascular Endothelial Growth Factor Receptors 1 and 2
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Tumor angiogenesis has become an important target for antitumor therapy, with most current therapies aimed at blocking the vascular endothelial growth factor (VEGF) pathway. The VEGF and its receptors have been implicated as key factors in tumor angiogenesis and are major targets in cancer therapy. A series of aryl-modified benzoylamino-N-(5,6-dimethoxy-1H-benzoimidazol-2-yl)-heteroamides were synthesized from 2-amino-5,6-dimethoxy benzimidazole and aryl-substituted benzoylamino hetero acids. The new compounds were tested for inhibition of VEGF receptors I and II (VEGFR-1 and VEGFR-2). Compound 6e displayed VEGFR-2 inhibitory activity with a 50% inhibition concentration value as low as 0.020 μM in a homogeneous time-resolved fluorescence enzymatic assay. VEGFR-2 active compounds display good activity against VEGFR-1 as well.
- Ashok, Abhishek,Thanukrishnan, Kannan,Bhojya Naik, Halehatty S.,Maridu, Rajendraswami
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p. 1949 - 1956
(2017/05/29)
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- Nucleophilic Nitration of Arynes by Sodium Nitrite and its Multicomponent Reaction Leading to Double-Functionalized Arenes
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An unusual nucleophilic nitration of arynes by NaNO2 in the presence of water has been developed, and the concept was further demonstrated to accomplish a double functionalization of arynes using a multicomponent reaction protocol to synthesize pharmaceutically important (2-nitrophenyl)methanol derivatives. Such substitution ortho to -NO2 is difficult by other means. The reaction conditions are mild and avoid the use of strong acids, expensive transition metal catalysts, and additives.
- Dhokale, Ranjeet A.,Mhaske, Santosh B.
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supporting information
p. 3010 - 3013
(2016/07/06)
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- A simple protocol for Cu-catalyzed protodecarboxylation of (hetero)aromatic carboxylic acids
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A simple and practical protodecarboxylation of o-nitrobenzoic acids as well as heteroaromatic carboxylic acids with various substituents via using CuI/Et3N has been established. This transformation provides a viable and low-cost approach to generating previously unavailable substituted arenes from readily accessible aryl carboxylic acids as the starting materials.
- Li, Zhaojie,Fu, Zhengjiang,Zhang, Haixia,Long, Jiao,Song, Yuanyuan,Cai, Hu
-
supporting information
p. 3014 - 3018
(2016/05/09)
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- Intramolecular dehydrogenative coupling of 2,3-diaryl acrylic compounds: Access to substituted phenanthrenes
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A simple, facile, and environmentally benign intramolecular dehydrogenative coupling of various 1,2-diarylethylenes for the synthesis of phenanthrenes in excellent yield has been described. This new methodology uses ceric ammonium nitrate (CAN) as a promoter at room temperature and has been extended to intermolecular synthesis of biaryl compounds. The electron transfer from methoxyarene to cerium leads to cationic radical formation, which further proceeds to intramolecular coupling. Preliminary mechanistic investigation by EPR spectroscopy and density functional theory calculation suggested a similar view.
- Gupta, Vijay,Rao, V. U. Bhaskara,Das, Tamal,Vanka, Kumar,Singh, Ravi P.
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p. 5663 - 5669
(2016/07/14)
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- A novel transition metal free [bis-(trifluoroacetoxy)iodo]benzene (PIFA) mediated oxidative ipso nitration of organoboronic acids
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A mild, convenient and transition metal free methodology for oxidative ipso nitration of diversely functionalized organoboronic acids, including heteroaryl- and alkylboronic acids, has been developed at ambient temperature using a combination of [bis-(trifluoroacetoxy)]iodobenzene (PIFA) - N-bromosuccinimide (NBS) and sodium nitrite as the nitro source. It is anticipated that the reaction proceeds through in situ generation of NO2 and O-centred organoboronic acid radicals followed by the formation of an O-N bond via combination of the said radicals. Finally transfer of the NO2 group to the aryl moiety occurs through 1,3-aryl migration to provide the nitroarenes.
- Chatterjee, Nachiketa,Bhatt, Divya,Goswami, Avijit
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supporting information
p. 4828 - 4832
(2015/05/05)
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- Palladium-catalyzed methoxylation of aromatic chlorides with borate salts
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Herein we disclose a simple palladiumcatalyzed transformation for the methoxylation of aromatic chlorides with tetramethoxyborate salts. The procedure provides a new and efficient synthetic tool for the introduction of a methoxy group into aromatic systems. In addition, the reaction can be achieved using a wide range of aromatic and heteroaromatic chlorides, the cheapest class of halides.
- Tolnai, Gergely L.,Petho, Bálint,Králl, Péter,Nováka, Zoltán
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supporting information
p. 125 - 129
(2014/03/21)
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- Ipso-nitration of arylboronic acids with bismuth nitrate and perdisulfate
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An efficient and one pot synthetic method of ipso-nitration of arylboronic acids has been developed. The high efficiency, general applicability, and broader substrate scope including heterocycles and functional groups make this method advantageous. Due to its simplicity, we expect to find application of this method in synthesis.
- Manna, Srimanta,Maity, Soham,Rana, Sujoy,Agasti, Soumitra,Maiti, Debabrata
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supporting information; experimental part
p. 1736 - 1739
(2012/05/20)
-
- Detection of explosives via photolytic cleavage of nitroesters and nitramines
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The nitramine-containing explosive RDX and the nitroester-containing explosive PETN are shown to be susceptible to photofragmentation upon exposure to sunlight. Model compounds containing nitroester and nitramine moieties are also shown to fragment upon exposure to UV irradiation. The products of this photofragmentation are reactive, electrophilic NOx species, such as nitrous and nitric acid, nitric oxide, and nitrogen dioxide. N,N-Dimethylaniline is capable of being nitrated by the reactive, electrophilic NOx photofragmentation products of RDX and PETN. A series of 9,9-disubstituted 9,10-dihydroacridines (DHAs) are synthesized from either N-phenylanthranilic acid methyl ester or a diphenylamine derivative and are similarly shown to be rapidly nitrated by the photofragmentation products of RDX and PETN. A new (turn-on) emission signal at 550 nm is observed upon nitration of DHAs due to the generation of fluorescent donor-acceptor chromophores. Using fluorescence spectroscopy, the presence of ca. 1.2 ng of RDX and 320 pg of PETN can be detected by DHA indicators in the solid state upon exposure to sunlight. The nitration of aromatic amines by the photofragmentation products of RDX and PETN is presented as a unique, highly selective detection mechanism for nitroester- and nitramine-containing explosives and DHAs are presented as inexpensive and impermanent fluorogenic indicators for the selective, standoff/remote identification of RDX and PETN.
- Andrew, Trisha L.,Swager, Timothy M.
-
body text
p. 2976 - 2993
(2011/06/21)
-
- Layered double hydroxide-supported l-methionine-catalyzed chemoselective o-methylation of phenols and esterification of carboxylic acids with dimethyl carbonate: A "green" protocol
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" Chemical equation presented" Simple methodology: A layered double hydroxide-supported L-methionine (LDH-Met) catalyst is designed in a simple methodology to explore its synthetic utility in biologically relevant reactions. The organocatalyst is characterized by FT-IR, TGA/DTA, powder XRD, and EDX spectroscopic techniques. This material has been successfully utilized for the preparation of aryl methyl ethers and esters from the corresponding phenols and carboxylic acids, respectively, in moderate to high yields (see scheme).
- Dhakshinamoorthy, Amarajothi,Sharmila, Alagarsamy,Pitchumani, Kasi
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supporting information; experimental part
p. 1128 - 1132
(2010/06/13)
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- Silver-catalysed protodecarboxylation of ortho-substituted benzoic acids
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Catalytic amounts of Ag(i) salts in DMSO have been found to promote the protodecarboxylation of a wide variety of ortho-substituted benzoic acids under mild conditions and in excellent yields, highlighting a possible role for silver in decarboxylative cross-couplings. The Royal Society of Chemistry 2009.
- Cornella, Josep,Sanchez, Carolina,Banawa, David,Larrosa, Igor
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supporting information; experimental part
p. 7176 - 7178
(2010/03/25)
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- Nitric acid in the presence of P2O5 supported on silica gel - A useful reagent for nitration of aromatic compounds under solvent-free conditions
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A variety of aromatic compounds are nitrated to parent nitro aromatic compounds under solvent-free conditions using 65% nitric acid in the presence of P2O5 supported on silica gel is described. This methodology is useful for nitration of activated and deactivated aromatic rings.
- Hajipour, Abdol Reza,Ruoho, Arnold E.
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p. 8307 - 8310
(2007/10/03)
-
- A fast and mild method for nitration of aromatic rings
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The use of benzyltriphenylphosphonium nitrate (PhCH2Ph 3P+NO3-) (BTPPN) as a useful reagent for nitration aromatic compounds in the presence of methanesulfonic anhydride under solvent-free conditions is described. This methodology is useful for nitration of activated aromatic rings.
- Hajipour, Abdol R.,Ruoho, Arnold E.
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p. 221 - 226
(2007/10/03)
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- tGENTS AND METHODS FOR THE TREATMENT OF DISORDERS ASSOCIATED WITH OXIDATIVE STRESS
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The invention provides a method for preventing or reducing the effects of oxidative stress on a substrate. The method includes the step of treating the substrate with a compound of formula (I), or a pharmaceutically acceptable salt thereof, wherein: R1 is one or more substituents selected from -H, -alkyl, -alkoxy, -aryl, -aryloxy, -halogen, -amino (mono-, di- and tri-substituted), -alkylthio, -NO2, -COOH, -COOAlkyl, -CO-alkyl, -CN; R2 is one or more substituents selected from -H, -alkyl, -(CH2CH2O)n-R5, a sugar moiety; R3 is -H, -alkyl, -aryl, -alkylOR6 , -alkylC(O)R6; R5 is selected from -H, -alkyl, -aryl; and R4 and R6 are independently selected from -OH, -O-alkyl, -O-polyalkyleneoxy, -O-aryl, -OC(O)O-alkyl, -S-alkyl and -amino.
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-
-
- Structural requirements for ipso-nitration with cerium(IV) ammonium nitrate (CAN)
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Compounds in which the carbon skeleton contains at least a diarylmethane with the aromatic rings appropriately substituted by electron donating groups exhibited ipso-nitration when treated with cerium(IV) ammonium nitrate (CAN).
- Asghedom,LaLonde,Ramdayal
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p. 3989 - 3991
(2007/10/03)
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- A mild one-pot procedure for the polynitration of activated arenes. Convenient preparation of dinitro- and trinitrodialkoxybenzenes
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When first treated with an excess of nitrogen dioxide alone and then in the presence of ozone at low temperature, dialkoxybenzenes are smoothly and stepwise polynitrated in a one-pot manner to afford the corresponding dinitro or trinitro derivatives in good yield.
- Nose,Suzuki
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p. 1539 - 1542
(2007/10/03)
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- Reactions of 1,2- and 1,3-dimethoxy- and 1,3,5-trimethoxybenzene with nitrogen dioxide/dinitrogen tetraoxide in dichloromethane
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The products of reaction of nitrogen dioxide/dinitrogen tetraoxide with dichloromethane solutions of three different methoxybenzenes are studied and interpreted in terms of initial nitrosation followed by oxidation with nitrogen dioxide.
- Gowenlock, Brian G.,King, Boyd,Pfab, Josef
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p. 276 - 277
(2007/10/03)
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- Nitration of electron-rich aromatic compounds by cerium ammonium nitrate coated on silica
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Treatment of electron-rich aromatic derivatives with cerium (IV) ammonium nitrate coated on silica (CANSio2) affords nitro aromatic compounds. The scope and the limitation of this reaction are discussed.
- Grenier, Jean-Luc,Catteau, Jean-Pierre,Cotelle, Philippe
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p. 1201 - 1208
(2007/10/03)
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- Thermal and photochemical decomposition pathways of trinitromethylarenes. part II. The effects of ethanol on the photolysis reactions of some alkoxy- and dialkoxyarenes in the presence of tetranitromethane. enhancement of adduct and trinitromethyl substitution product formation
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The photolysis of the charge transfer (CT) complex of tetranitromethane with 1-methoxynaphthalene, 1,4-dimethoxybenzene, 1,2-dimethoxybenzene, 1,2-methylenedioxybenzene or 2-methylanisole is reported for dichloromethane, acetonitrile, dichloromethane-ethanol and acetonitrile-ethanol solvent systems. The effects of adding ethanol (8% v/v ? 1.4 mol dm-3) to dichloromethane or acetonitrile as reaction solvents include: (i) the stabilization of alkoxytrinitro-methylarenes, thus reducing their normal tendency for decomposition according to ArC (NO2)3→ArCOOH→ArNO2, (ii) a reduction in the nucleophilicity of trinitromethanide ion, and (iii) changes in the regioselectivity of trinitromethanide ion attack on the radical cations of alkoxyaromatic compounds away from attack ipso to the alkoxy substituent. Adducts are also stabilized, as shown by the photolysis of the CT complex of 1,4-dimethoxybenzene-tetranitromethane in dichloromethane-ethanol (8% v/v) which gives the epimeric 1,4-dimethoxy-3-nitro-6-trinitromethylcyclohexa-1,4-dienes and 1,4-dimethoxy-2-trinitromethylbenzene, in addition to 1,4-dimethoxy-2-nitrobenzene. The adducts are detected also among the products of photolysis reactions in neat dichloromethane or acetonitrile. Acta Chemica Scandinavica 1997.
- Butts, Craig P.,Eberson, Lennart,Hartshorn, Michael P.,Persson, Ola
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p. 718 - 732
(2007/10/03)
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- Substituted methoxybenzene derivatives: C8H9NO4, C9H11NO5 and C13H18O4
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The structures of three methoxybenzenes, namely 1,2-dimethoxy-4-nitrobenzene, C8H9NO4, (I), 1,2,3-trimethoxy-5-nitrobenzene, C9H11NO5, (II), and 1-(2,4,5-trimethoxyphenyl)-1-butanone, C13H18O4, (III), are reported. Molecules of (I) and (III) are planar, but one of the three methoxy groups of (II) is twisted out of the phenyl ring plane as a result of steric hindrance. In all three solids, the molecules are linked to form centrosymmetrically hydrogen-bonded dimers; they are packed in parallel layers in (I) and (II), but in zigzag layers in (III).
- Fun,Chinnakali,Sivakumar,Sam,How
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p. 1859 - 1862
(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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- Nitration of dimethoxybenzenes, mesitylene and toluene with nitric acid and mixed acid studied by 15N-CIDNP
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During nitration of 1,2- and 1,4-dimethoxybenzene 1,2 with 15N-labelled nitric acid in acetic acid, acetonitrile and CCl 4 at room temperature, the 15N NMR signals of the nitration products 5, 6 exhibit emission which is built up in radical pairs formed by encounters of independently generated radical cations 1 ?+, 2?+ and NO2. It is proved by a quantitative analysis of the 15N-CIDNP effect during nitration of 1 that the radical pathway is the main reaction, which is a nitrous acid catalysed nitration first proposed by Ridd. Mesitylene 3 and toluene 4 are not nitrated under these conditions. During nitration of 3 with mixed acid in acetic acid, a weak 15N-CIDNP effect is observed in nitromesitylene 7. 15N-CIDNP is not found with 4 in the nitrotoluenes 8-10, but in the side products 12 and 13. The nitration of 3 with mixed acid is described to more than 95% and of 4 exclusively by Ingold's classical mechanism.
- Lehnig, Manfred
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p. 1943 - 1948
(2007/10/03)
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- Convenient Nitration of Anisole and its Derivatives using an NO-O2 System
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Anisole and its derivatives are regioselectively nitrated by use of nitrogen monoxide-molecular dioxygen mixed gas under mild conditions.
- Mizuno, Kazuhiko,Tamai, Toshiyuki,Hashida, Isao,Otsuji, Yoshio,Inoue, Hiroo
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p. 284 - 285
(2007/10/03)
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- Selective nitration versus oxidative dealkylation of hydroquinone ethers with nitrogen dioxide
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Various alkyl-substituted p-dialkoxybenzenes (ArH) react readily with nitrogen dioxide (NO2) in dichloromethane solution via either nitration (ArNO2) or oxidative dealkylation to quinones (Q). Spectral transients indicate that these coupled processes proceed from the dialkoxybenzene radical cation (ArH+) formed as the common reactive intermediate from electron-transfer in the disproportionated precursor [ArH, NO+]NO3-. In fast subsequent steps, ArH+ undergoes homolytic coupling with NO2 (which leads to aromatic nitration) and nucleophilic attack of NO3- (which results in oxidative dealkylation). As such, the competition between nitration and oxidative dealkylation is effectively modulated by solvent polarity and added nitrate.
- Rathore,Bosch,Kochi
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p. 6727 - 6758
(2007/10/02)
-
- Kinetics and mechanisms of the gas-phase reactions of the NO3 radical with aromatic compounds
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The kinetics and nitrated products of the gas-phase reactions of the NO3 radical with methoxybenzene, 1,2-, 1,3-, and 1,4-dimethoxybenzene, dibenzofuran and dibenzo-p-dioxin have been investigated at 297 ± 2 K and in the presence of one atmosphere of air. A relative rate method was used for the kinetic measurements. No reactions of methoxybenzene or dibenzofuran with the NO3 radical were observed. The dimethoxybenzenes were observed to react by H-atom abstraction and NO3 radical addition to the aromatic ring, while dibenzo-p-dioxin reacted by NO3 radical addition to the aromatic rings. For these compounds, the NO3 radical addition pathways were observed to be reversible. At the NO2 concentrations employed, the NO3-aromatic adducts reacted with NO2 and the observed rate constants increased with increasing NO2 concentration. However, for dibenzo-p-dioxin the observed rate constant became independent of the NO2 concentration for concentrations ≥ 4.8 × 1013 molecule cm-3, and under these conditions the rate constant of 6.8 × 10-14 cm3 molecule-1 s-1 was taken to be that for addition of the NO3 radical to the aromatic rings. The proposed NO3 radical reaction mechanisms are discussed.
- Kwok,Atkinson,Arey
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p. 511 - 525
(2007/10/03)
-
- Correlation of Reaction Rates with a Substituent Constant Scale Derived from Calculated Electron Densities for a Computer Control Algorithm
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A new ? substituent scale based on electron density calculations by the AM1 quantum mechanical model has been established and used to correlate rates of O-methylation of substituted phenols, as part of a chemical artificial intelligence to control a fully automated apparatus for methyl iodide labeling.
- Cork, David G.,Hayashi, Nobuyoshi
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p. 1583 - 1585
(2007/10/02)
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- Stable highly oxidizing cobalt complexes of macrocyclic ligands
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The first crystallographically characterized neutral square-planar complex of cobalt in an oxidation state higher than 2+, Co(η44-1), is reported. Structural data for this new class of compounds indicate that the macrocycle in Co(η4-1) is Equation Presented X = Cl, Co(η4-1) X = H, Co(η4-2) X = MeO, Co(η4-3) noninnocent; however, EPR data in toluene at 5.9 K (S = 1/2; g1 = 2.558, g2 = 2.170, g3 = 2.017; A2 ≈ 15 G) show that the metal center is the primary reisdence site of the unpaired electron. Co(η4-1) is a stable, yet potent, oxidant which is soluble in benzene and slightly soluble in pentane. The Co(η4-1)/[CoIII(η4-1)]- couple is reversible and found at 0.550 V vs Fc+/Fc in CH2Cl2 (ca. 1.26 V vs NHE). Co(η4-1) slowly oxidized water, yielding H[CoIII(η4-1)], which may also be prepared by the reaction of [CoIII(η4-1)]- with HBF4. Both the redox and the acid/base chemistries of [CoIII(η4-1)]- are reversible. Electrochemical and EPR data are also presented for Co(η4-2) and Co(η4-3).
- Collins, Terrence J.,Powell, Richard D.,Slebodnick, Carla,Uffelman, Erich S.
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p. 8419 - 8425
(2007/10/02)
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- STUDIES ON THE TWO-PHASE NITRATION OF PHENOLS (part 2)
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Gas phase Ionization Potentials can be correlated with solution Oxidation Potentials for phenols and used to predict the likelihood of successful nitration using the two-phase procedure.The interaction of steric and electronic effects then determines the sites of nitration by radical recombination of the phenoxy radical and NO2.Nitration of dioxybenzenes may give insights into the nitration mechanism.
- Thompson, Malcolm J.,Zeegers, Petrus J.
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p. 2661 - 2674
(2007/10/02)
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- THE SEARCH FOR NEW BIOCHEMICAL PHOTOPROBES. II. THE NUCLEOPHILIC PHOTOSUBSTITUTION OF 2-FLUORO-4-NITROANISOLE.
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The photosubstitutions of 2-fluoro-4-nitroanisole with several amines are studied.The preparative results, the thermal stability of the photochemical substrate, and the limiting quantum yield values obtained from photoreactions with several nucleophiles suggest the possible usefulness of 2-fluoro-4-nitrophenyl ethers as biochemical photoprobes.
- Pleixats, R.,Figueredo, M.,Marquet, J.,Moreno-Manas, M.,Cantos, A.
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p. 7817 - 7826
(2007/10/02)
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- THE PHOTOREACTIONS OF 2-FLUORO-4-NITROANISOLE WITH AMINES. THE SEARCH FOR NEW BIOCHEMICAL PHOTOPROBES
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The photosubstitutions of 2-fluoro-4-nitroanisole with several amines are studied from the preparative and the preliminary mechanistic points of view.The possible usefulness of this structure as biochemical photoprobe is discussed.
- Figueredo, M.,Marquet, J.,Moreno-Manas, M.,Pleixats, R.
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p. 2427 - 2428
(2007/10/02)
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- I. Photochemical nitration of methoxybenzenes from charge-transfer complexes with tetranitromethane
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The direct irradiation of the charge-transfer (CT) absorption band of the 1/1 electron donor-acceptor complexes of dimethoxybenzenes with tetranitromethane leads to aromatic nitration with a high quantum yield.The analogous methoxytoluenes under the same photochemical conditions are converted in equally high yields to products of aromatic trinitromethylation.This dichotomy with different methoxybenzenes (ArH) is discussed within the context of the common reactive intermediates derived from the CT excitation of the complex.The subsequent interactions of the geminate fragments, i.e., +., C(NO2)3-, .NO2>, by radical-pair and ion-pair annihilation represent a unifying mechanism for the CT photochemistry leading to aromatic nitration and trinitromethylation.
- Sankararaman, S.,Kochi, J. K.
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p. 278 - 285
(2007/10/02)
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