- Brightly shining nanoparticles: Lipophilic perylene bisimides in aqueous phase
-
The dispersion of lipophilic perylene bisimides down to nanoparticle dimensions opens the aqueous phase to these highly fluorescent, water insoluble materials. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Langhals, Heinz
-
-
Read Online
- Photoinduced Iron-Catalyzed ipso-Nitration of Aryl Halides via Single-Electron Transfer
-
A photoinduced iron-catalyzed ipso-nitration of aryl halides with KNO2 has been developed, in which aryl iodides, bromides, and some of aryl chlorides are feasible. The mechanism investigations show that the in situ formed iron complex by FeSO4, KNO2, and 1,10-phenanthroline acts as the light-harvesting photocatalyst with a longer lifetime of the excited state, and the reaction undergoes a photoinduced single-electron transfer (SET) process. This work represents an example for the photoinduced iron-catalyzed Ullmann-type couplings.
- Wu, Cunluo,Bian, Qilong,Ding, Tao,Tang, Mingming,Zhang, Wenkai,Xu, Yuanqing,Liu, Baoying,Xu, Hao,Li, Hai-Bei,Fu, Hua
-
p. 9561 - 9568
(2021/08/06)
-
- NITRATION
-
The present invention relates to a process for preparing a nitrated compound, comprising the step of reacting a compound (A) comprising at least one substituted or unsubstituted aromatic or heteroaromatic ring, wherein said heteroaromatic ring comprises at least one heteroatom selected from the group consisting of oxygen, sulfur, phosphor, selenium and nitrogen, with a compound of formula (I) wherein Y is selected from the group consisting of hydrogen and nitro.
- -
-
Page/Page column 36; 41; 46; 64; 37
(2020/05/28)
-
- N-Nitroheterocycles: Bench-Stable Organic Reagents for Catalytic Ipso-Nitration of Aryl- And Heteroarylboronic Acids
-
Photocatalytic and metal-free protocols to access various aromatic and heteroaromatic nitro compounds through ipso-nitration of readily available boronic acid derivatives were developed using non-metal-based, bench-stable, and recyclable nitrating reagents. These methods are operationally simple, mild, regioselective, and possess excellent functional group compatibility, delivering desired products in up to 99% yield.
- Budinská, Alena,Katayev, Dmitry,Passera, Alessandro,Zhang, Kun
-
supporting information
(2020/03/30)
-
- Nucleophilic Iron Complexes in Proton-Transfer Catalysis: An Iron-Catalyzed Dimroth Cyclocondensation
-
The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) is an active catalyst in C?H-amination but also in proton-transfer catalysis. Herein, we describe the successful use of this complex as a proton-transfer catalyst in the cyclocondensation reaction between azides and ketones to the corresponding 1,2,3-triazoles. Cross-experiments indicate that the proton-transfer catalysis is significantly faster than the nitrene-transfer catalysis, which would lead to the C?H amination product. An example of a successful sequential Dimroth triazole–indoline synthesis to the corresponding triazole-substituted indolines is presented.
- Baykal, Aslihan,Zhang, Dihan,Knelles, Jakob,Alt, Isabel T.,Plietker, Bernd
-
supporting information
p. 3003 - 3010
(2019/08/21)
-
- Base promoted peroxide systems for the efficient synthesis of nitroarenes and benzamides
-
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.
-
supporting information
(2019/09/07)
-
- Synthesis of nitroolefins and nitroarenes under mild conditions
-
1,3-Disulfonic acid imidazolium nitrate {[Dsim]NO3} was prepared and characterized as a new ionic liquid and nitrating agent for the ipso-nitration of various arylboronic acids and nitro-Hunsdiecker reaction of different α,β-unsaturated acids and benzoic acid derivatives, by in situ generation of NO2 to give various nitroarenes and nitroolefins without using any cocatalysts and solvents under mild conditions.
- Zarei, Mahmoud,Noroozizadeh, Ehsan,Moosavi-Zare, Ahmad R.,Zolfigol, Mohammad A.
-
p. 3645 - 3650
(2018/04/14)
-
- One-Pot C?H Functionalization of Arenes by Diaryliodonium Salts
-
A transition-metal-free, mild, and highly regioselective synthesis of nitroarenes from arenes has been developed. The products are obtained in a sequential one-pot reaction by nitration of iodine(III) reagents with two carbon ligands, which are formed in situ from iodine(I). This novel concept has been extended to formation of aryl azides, and constitutes an important step towards catalytic reactions with these hypervalent iodine reagents. An efficient nitration of isolated diaryliodonium salts has also been developed, and the mechanism is proposed to proceed by a [2,2] ligand coupling pathway.
- Reitti, Marcus,Villo, Piret,Olofsson, Berit
-
p. 8928 - 8932
(2016/07/26)
-
- Transition-metal-free synthesis of thiocyanato- or nitro-arenes through diaryliodonium salts
-
A transition-metal-free approach to facile synthesis of thiocyanato- and nitro-arenes was developed from KSCN (potassiumthiocyanate) or NaNO2with diaryliodonium salts in good yields under mild conditions. The reaction was compatible with a variety of sensitive functional substituents such as halides and nitro and ester groups. The usefulness of arylation products has been realized. (Formula Present).
- Li, Xiao-Hua,Li, Liang-Gui,Mo, Xue-Ling,Mo, Dong-Liang
-
p. 963 - 970
(2016/07/07)
-
- Regioselective nitration of aromatics with nanomagnetic solid superacid SO42-/ZrO2-MxOy-Fe 3O4 and its theoretical studies
-
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
-
p. 310 - 317
(2013/08/23)
-
- Preparation of heteropoly acid based amphiphilic salts supported by nano oxides and their catalytic performance in the nitration of aromatics
-
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
-
p. 2197 - 2202
(2013/03/14)
-
- Rare earth metal triflates catalyzed electrophilic nitration using N 2O5
-
A mild, efficient and eco-friendly process for the electrophilic nitration is described using N2O5 as a green nitrating agent in the presence of rare earth metal triflates [RE(OTf)3] under mild conditions.
- Ma, Xiao Ming,Li, Bin Dong,Lu, Ming,Lv, Chun Xu
-
experimental part
p. 73 - 76
(2012/03/26)
-
- Green and controllable metal-free nitrification and nitration of arylboronic acids
-
A novel and green nitrating reagent has been developed for the nitrification and nitration of arylboronic acids, which can be controlled by the reaction conditions. The process provides an attractive alternative to the traditional nitration protocols.
- Wang, Shuai,Shu, Chun Chun,Wang, Tao,Yu, Jian,Yan, Guo Bing
-
scheme or table
p. 643 - 646
(2012/08/07)
-
- Selective nitration of aromatic compounds catalyzed by Hβ zeolite using N2O5
-
A selective and efficient process for the electrophilic nitration is described using N2O5 as a green nitrating agent, Hβ zeolite as a solid acid catalyst and shape controlling agent under mild conditions.
- Ma, Xiao Ming,Li, Bin Dong,Chen, Lei,Lu, Ming,Lv, Chun Xu
-
scheme or table
p. 809 - 812
(2012/08/08)
-
- Reusable and efficient polystryrene-supported acidic ionic liquid catalyst for mononitration of aromatic compounds
-
A series of polystyrene-supported 1-(propyl-3-sulfonate)-3-methyl- imidazolium hydrosulfate acidic ionic liquid (PS-[SO3H-PMIM][HSO 4]) catalysts were prepared and tested for mononitration of simple aromatics compounds with nitric acid. It was found that the reactivity of the catalysts increased with increasing [SO3HPMIM][ HSO4] content. The para-selectivity was not only related to the [SO 3H-PMIM][HSO4] content but also the substituent groups in aromatics. A reaction mechanism of nitration over this new catalyst was proposed. The catalytic activity of this catalyst decreased slightly after fifth runs in the synthesis of nitrotoluene.
- Li, Li Xia,Ling, Qi Long,Liu, Zu Liang,Xing, Xiao Dong,Zhu, Xiao Qin,Meng, Xiao
-
p. 3373 - 3377
(2013/01/15)
-
- Copper-catalyzed nitration of arylboronic acids with nitrite salts under mild conditions: An efficient synthesis of nitroaromatics
-
Copper-catalyzed nitration of arylboronic acids has been developed with nitrite salts as nitrating agent under mild conditions. This process provides an efficient and practical method for the synthesis of nitro aromatics, due to its simple experimental procedure and its use of convenient and inexpensive copper catalyst.
- Yan, Guobing,Zhang, Ling,Yu, Jian
-
experimental part
p. 133 - 137
(2012/07/28)
-
- Ipso-nitration of arylboronic acids with bismuth nitrate and perdisulfate
-
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
-
supporting information; experimental part
p. 1736 - 1739
(2012/05/20)
-
- Copper catalyzed ipso-nitration of iodoarenes, bromoarenes and heterocyclic haloarenes under ligand-free conditions
-
A catalytic protocol for the conversion of haloarenes into the corresponding nitroarenes is presented using copper salts under ligand-free conditions. The method was effectively utilized for the ipso-nitration of a broad variety of haloarenes that includes iodoarenes, bromoarenes, and heterocyclic haloarenes.
- Amal Joseph,Priyadarshini,Lakshmi Kantam,Maheswaran
-
supporting information; experimental part
p. 1511 - 1513
(2012/03/27)
-
- Regioselectivity nitration of aromatics with N2O5 in PEG-based dicationic ionic liquid
-
Regioselective mononitration of simple aromatic compounds has been investigated with N2O5 as nitrating agent and a new PEG200-based dicationic acidic ionic liquid (PEG200-DAIL) as catalyst. The results of experiments show that this nitration system can significantly improve the para-selectivity of alkyl-benzenes and the ortho-selectivity of halogenated-benzenes. The PEG200-DAIL exhibits recyclable temperature-dependant phase behavior in CCl4 solvent, and it can be recycled without apparent loss of catalytic activity, and only 5% loss of weight is observed after six times recycling.
- Wang, Peng-Cheng,Lu, Ming
-
supporting information; experimental part
p. 1452 - 1455
(2011/05/16)
-
- An efficient and eco-friendly MoO3-SiO2 solid acid catalyst for electrophilic aromatic nitration with N2O5
-
Electrophilic aromatic nitration using N2O5 as a green nitrating agent catalyzed by MoO3-SiO2 under mild conditions has been described. A series of MoO3-SiO2 catalysts with varying MoO3 loadings (5-20 mol%) were prepared by sol-gel technique and characterized using FTIR, XRD, SEM, BET and NH 3-TPD to study its surface properties. MoO3-SiO 2 shows good catalytic activity and reusability for the nitration of alkyl and halogen aromatics giving high conversions, but less efficiency for the deactivated aromatics. Reactions conducted under non-acidic conditions using N2O5 makes the process safe and environmentally friendly. Graphical Abstract: [Figure not available: see fulltext.]
- Ma, Xiaoming,Li, Bindong,Lv, Chunxu,Lu, Ming,Wu, Jian,Liang, Linjie
-
experimental part
p. 1814 - 1820
(2012/03/08)
-
- Pd-catalyzed conversion of aryl chlorides, triflates, and nonaflates to nitroaromatics
-
(Chemical Equation Presented) An efficient Pd catalyst for the transformation of aryl chlorides, triflates, and nonaflates to nitroaromatics has been developed. This reaction proceeds under weakly basic conditions and displays a broad scope and excellent
- Fors, Brett P.,Buchwald, Stephen L.
-
supporting information; experimental part
p. 12898 - 12899
(2009/12/07)
-
- LIGANDS FOR TRANSITION-METAL-CATALYZED CROSS-COUPLINGS, AND METHODS OF USE THEREOF
-
Ligands for transition metals are disclosed herein, which may be used in various transition-metal-catalyzed carbon-heteroatom and carbon-carbon bond-forming reactions. The disclosed methods provide improvements in many features of the transition-metal-catalyzed reactions, including the range of suitable substrates, number of catalyst turnovers, reaction conditions, and efficiency. For example, improvements have been realized in transition-metal-catalyzed cross-coupling reactions.
- -
-
Page/Page column 144-145
(2009/07/17)
-
- Metal complexes of tetra(6-tert-butyl-2,3-quinolino)porphyrazine: I. Synthesis
-
Complexes of tetra(6-tert-butyl-2,3-quinolino)porphyrazine with Cu, Co, Zn, and Ni soluble in hydrophobic liquids were synthesized for the first time by template tetramerization of derivatives of 6-tert-butylquinoline-2,3- dicarboxylic acid formed from the corresponding acid in the course of carbamide synthesis in presence of the bivalent metal ions.
- Efimova,Korzhenevskii,Koifman
-
scheme or table
p. 1614 - 1621
(2009/06/28)
-
- Synthesis of o-nitrosoacylbenzenes from o-nitrobenzyl alcohols and their derivatives
-
Nitration of substituted benzyl alcohols, as well as ethers and esters derived therefrom, with nitric acid in acetic anhydride was studied. The corresponding o-nitrobenzyl alcohols and their derivatives formed as the primary products are capable of being converted into o-nitrosoacylbenzenes by the action of acids. Pleiades Publishing, Inc., 2006.
- Gazzaeva,Fedotov,Trofimova,Popova,Mochalov,Zefirov
-
-
- Transformations of para-substituted benzylcyclopropanes, allylbenzenes, and diphenylmethanes under nitration with nitric acid in acetic anhydride
-
Electrophilic nitration of benzylcyclopropanes, allylbenzenes, and diphenylmethanes containing ortho, para-orienting substituents in the para position of the benzene ring results mainly in replacement of the cyclopropylmethyl, allyl, or benzyl group, respectively (ipso substitution). The nitration of 4-cyclopropylallylbenzene is not accompanied by nitrodealkylation, and the products are only 2- and 3-nitro-4-cyclopropylallylbenzenes.
- Mochalov,Gazzaeva,Fedotov,Archegov,Trofimova,Shabarov,Zefirov
-
p. 406 - 416
(2007/10/03)
-
- Copper-catalyzed coupling of aryl halides and nitrite salts: A mild Ullmann-type synthesis of aromatic nitro compounds
-
Nitration of aromatic halides proceeded smoothly in the presence of catalytic amounts of Cu bronze and N,N′-dimethylethylenediamine. Sodium nitrite-18-crown-6, or tetra-n-butylammonium nitrite (n-Bu4NNO 2) turned out to be efficient nitrating agents. The aromatic nitro compounds were synthesized under essentially neutral conditions.
- Saito, Shinichi,Koizumi, Yuichiro
-
p. 4715 - 4717
(2007/10/03)
-
- Electrophilic nitration of aromatics in ionic liquid solvents
-
Potential utility of a series of 1-ethyl-3-methylimidazolium salts [emim][X] with X = OTf-, CF3COO-, and NO3- as well as [HNEtPri2][CF3COO] (protonated Huenig's base) ionic liquids were explored as solvent for electrophilic nitration of aromatics using a variety of nitrating systems, namely NH4NO3/TFAA, isoamyl nitrate/BF3·Et2O, isoamyl nitrate/TfOH, Cu(NO3)/TFAA, and AgNO3/Tf2O. Among these, NH4NO3/TFAA (with [emim][CF3COO], [emim][NO3]) and isoamyl nitrate/BF3·Et2O, isoamyl nitrate/TfOH (with [emim][OTf]) provided the best overall systems both in terms of nitration efficiency and recycling/reuse of the ionic liquids. For [NO2][BF4] nitration, the commonly used ionic liquids [emim][AlCl4] and [emim][Al2Cl7] are unsuitable, as counterion exchange and arene nitration compete. [Emim][BF4] is ring nitrated with [NO2][BF4] producing [NO2-emim][BF4] salt, which is of limited utility due to its increased viscosity. Nitration in ionic liquids is surveyed using a host of aromatic substrates with varied reactivities. The preparative scope of the ionic liquids was also extended. Counterion dependency of the NMR spectra of the [emim][X] liquids can be used to gauge counterion exchange (metathesis) during nitration. Ionic liquid nitration is a useful alternative to classical nitration routes due to easier product isolation and recovery of the ionic liquid solvent, and because it avoids problems associated with neutralization of large quantities of strong acid.
- Laali,Gettwert
-
-
- Improved nitrations using metal nitrate-sulfuric acid systems
-
Procedures for efficient mono- and di-nitration of aromatic substrates have been developed using ceric ammonium nitrate suspended in dichloromethane in the presence of 2 equiv. of sulfuric acid. By suspending the sulfuric acid on silica gel following nitration, products are easily isolated by filtration and evaporation of solvent. In these nitrations ceric ammonium nitrate can be replaced by other metal nitrates, for example potassium- or tetrabutylammonium-nitrate. In contrast the nitration of naphthalene by ceric ammonium nitrate in the presence of methanol and sulfuric acid affords a mixture of 1,4- and 1,2-methoxynitronaphthalenes, but these nitrations cannot be achieved using potassium or tetrabutylammonium nitrate. The mechanism of this nitration/oxidation is discussed. (C) 2000 Elsevier Science Ltd.
- Mellor, John M.,Mittoo, Stifun,Parkes, Rachel,Millar, Ross W.
-
p. 8019 - 8024
(2007/10/03)
-
- A convenient copper-catalyzed direct animation of nitroarenes with 9-alkylhydroxylamines
-
O-Alkylhydroxylamines, particularly O-methylhydroxylamine, aminate nitroarenes in the presence of a strong base and a copper catalyst to give aminonitroarenes in good yields, ortho- or para-Animation with respect to the nitro group takes place, and in some cases the ortho-aminated product is preferentially obtained. With 3-substituted nitrobenzenes where the substituent has a lone pair of electrons, preferential amination occurs at the 2-position to give the sterically most congested 3c-f, 14 and 22g.
- Seko, Shinzo,Miyake, Kunihito,Kavvamura, Norio
-
p. 1437 - 1444
(2007/10/03)
-
- Rotational features of carbon-nitrogen bonds in N-aryl maleimides. Atroposelective reactions of o-tert-butylphenylmaleimides
-
Atroposelective addition and cycloaddition reactions of N-2- (tertbutylphenyl)- and N-2,5 (di-tert-butylphenyl)maleimide and a substituted derivative have been studied. Good to excellent stereoselectivities are generally observed, and high rotation barriers (about 29 kcal/mol) prevent the products from inter, converting. Crystal structures of the precursors and products support a straightforward model where reactants attack trans to the o-tert butyl group.
- Curran, Dennis P.,Geib, Steven,DeMello, Nicholas
-
p. 5681 - 5704
(2007/10/03)
-
- Vanadium(v) oxytrinitrate, VO(NO3)3. A powerful reagent for the nitration of aromatic compounds at room temperature under non-acidic conditions
-
Vanadium(v) oxytrinitrate is an easy to handle reagent which can be used to nitrate a range of substituted aromatic compounds in dichloromethane at room temperature, leading to >99% yields of nitration products in most cases.
- Dove, Michael F. A.,Manz, Berthold,Montgomery, John,Pattenden, Gerald,Wood, Simon A.
-
p. 1589 - 1590
(2007/10/03)
-
- A novel method for the nitration of simple aromatic compounds
-
Simple aromatic compounds such as benzene, alkylbenzenes, halogenobenzenes, and some disubstituted benzenes are nitrated in excellent yields with high regioselectivity under mild conditions using zeolite β as a catalyst and a stoichiometric quantity of nitric acid and acetic anhydride. The zeolite can be recycled, and the only byproduct is acetic acid, which can be separated easily from the nitration product by distillation; the process is inexpensive and represents an attractive method for the clean synthesis of a range of nitroaromatic compounds. For example, nitration of toluene gives a quantitative yield of mononitrotoluenes, of which 79% is 4-nitrotoluene; fluorobenzene gives a quantitative yield of mononitro compounds, of which 94% is 4-nitrofluorobenzene; and 2-fluorotoluene gives a 96% yield of mononitro products, of which 90% is the 5-nitro isomer and 10% is the 4-nitro isomer.
- Smith, Keith,Musson, Adam,DeBoos, Gareth A.
-
p. 8448 - 8454
(2007/10/03)
-
- Synthesis of functionalized carbamates through a palladium-catalyzed reductive carbonylation of substituted nitrobenzenes
-
The palladium-catalyzed reductive carbonylation of ortho and para-substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1,10-phenanthroline)2(triilate}2 catalyst system, the scope of the reaction has been studied. Substrates with electron-donating substituents at the para position were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. The selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron-withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at the ortho position of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion of the nitro group. Especially with 4-nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis for N-protected amines containing carboxylic acid functions. VCH Verlagsgesellschaft mbH.
- Wchman, Petra,Borst, Leo,Kamer, Paul C. J.,Van Leeuwen, Piet W. N. M.
-
-
- Iron(III)-catalysed nitration of non-activated and moderately activated arenes with nitrogen dioxide-molecular oxygen under neutral conditions
-
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
-
p. 2385 - 2389
(2007/10/03)
-
- Cobalt schiff base complex-catalyzed oxidation of anilines with tert-butyl hydroperoxide
-
Cobalt Schiff base complexes [Co(SB)] catalyze the oxidation of anilines (1) with tert-butyl hydroperoxide to give nitrobenzenes 2 and 4-(tert-butylperoxy)-2,5-cyclohexadien-1-imine derivatives 3 in yield distributions depending on the substitution mode of the substrate. 4-Alkyl- and 4-aryl-2,6-di-tert-butylanilines gave mixtures of 2 and 3, where the higher the bulkiness of the 4-substituent, the higher the yield of 2. With 2,4,6-trimethylaniline, the ratio of oxidations of the nitrogen and C-4 atoms was almost the same; but a hydrolyzed product 5 of the imine was obtained. 2,4,6-Triphenylaniline gave only 2. Nitrobenzene derivatives were also obtained from 2,6-dialkylanilines and 4-substituted anilines. The catalytic activity of Co(SB) depended on the nature of the SB ligand: the formal potential E° and steric factors seem to affect the reaction rate. Kinetic studies showed that the key step may involve hydrogen abstraction from the aniline, presumably by t-BuO? generated from homolytic decomposition of initially formed CoIII(SB)(OO-t-Bu). A precursor of 2 was found to be the nitrosobenzene derivative.
- Foerster, Stefan,Rieker, Anton,Maruyama, Kazushige,Murata, Kunihiko,Nishinaga, Akira
-
p. 3320 - 3326
(2007/10/03)
-
- Structure-activity relationship of omeprazole and analogues as Helicobacter pylori urease inhibitors
-
Helicobacter pylori urease belongs to a family of highly conserved urea- hydrolyzing enzymes. A common feature of these enzymes is the presence of two Lewis acid nickel ions and a reactive cysteine residue in the active site. The H+/K+-ATPase inhibitor omeprazole is a prodrug of a sulfenamide which covalently modifies cysteine residues on the luminal side of the H+/K+- ATPase of gastric parietal cells. Omeprazole and eight analogues were selected based on their chemical, electronic, and kinetic properties, and each was incubated with viable H. pylori in phosphate-buffered saline at pH 7.4 for 30 min, after which 100 mM urea was added and the amount of ammonia formed analyzed after a further 10 min. Inhibition between 0% and 100% at a 0.1 mM concentration was observed for the different analogues and could be expressed as a function of the pK(a)-value of the pyridine, the pK(a)-value of the benzimidazole, the overall lipophilicity, and, most importantly, the rate of sulfenamide formation, in a quantitative structure-activity relationship. The inhibition was potentiated by a lower pH (favoring the formation of the sulfenamide) but abolished in the presence of β- mercaptoethanol (a scavenger of the sulfenamide). Structural analogues incapable of yielding the sulfenamide did not inhibit ammonia production. Treatment of Helicobacter felis-infected mice with 230 μmol/kg flurofamide b.i.d. for 4 weeks, known to potently inhibit urease activity in vivo, as a means of eradicating the infection, was tested and compared with the effect of 125 μmol/kg omeprazole b.i.d. for 4 weeks. Neither treatment proved efficacious.
- Kuhler,Fryklund,Bergman,Weilitz,Lee,Larsson
-
p. 4906 - 4916
(2007/10/03)
-
- Reductive Activation of Arenes. X. Effect of the Cation and Crown-Ether Additions on the Direction of tert-Butylation of Products of One-Electron Reduction of Nitrobenzene by Alkali Metals in Liquid Ammonia
-
Reaction of tert-butyl iodide with products of one-electron reduction of nitrobenzene by alkali metals (Li, Na, K, Rb, Cs) in liquid ammonia results in formation of compounds alkylated at the nitro group (N-alkylation) and the benzene ring (C-alkylation).The ratio of the N- and C-alkylated products (N/C) increases with increasing size of the alkali metal cation.Additions of crown ethers or sodium bromide and iodide, as well as variation of the concentration of the reduction product have almost no effect on the N/C value.Increased overall yield of the alkylation products and reduced N/C ratio were observed when the product of nitrobenzene reduction with potassium reacted with tert-butyl iodide in the presence of dicyclohexano-18-crown-6.
- Selivanov, B. A.,Shteingarts, V. D.
-
p. 1276 - 1283
(2007/10/03)
-
- Hydrocarbons and chloroaromatics from anilines and n-butyl nitrite
-
A single reagent, i.e. n-butyl nitrite, can be used to oxidize an aromatic amine, or the corresponding N-methylene derivative, to a diazo compound followed by its subsequent reduction to hydrocarbon in a single batch.Alternatively, a chloro derivative can be obtained if carbon tetrachloride is used as the solvent.The reactions appear to be general and complete product identification was accomplished.
- Giumanini, Angelo G.,Verardo, Giancarlo,Gorassini, Fausto,Strazzolini, Paolo
-
p. 311 - 316
(2007/10/02)
-
- Oxidation of organic amide ions by dioxygen 2. Stable and intermediate products
-
The products of base-catalysed oxidation of secondary amines were identified by the GC-MS and EPR techniques as nitroxyls, quinone nitrones, quinone imines, and for diarylamines also as the products of C-N bond cleavage/substituted nitrobenzenes, anilines and phenols.It was shown that nitroxyl radicals are the primary paramagnetic products of the reaction and do not form by the interaction of aminyl radicals with dioxygen.A mechanism of the amide ion oxidation through the nonradical addition of dioxygen to the amide ion at the rate-limiting stage is suggested and discussed. - Key words: aromatic amines, amide ions, oxidation, dioxygen, mechanism, nitroxyl radicals, synthesis.
- Shashin, S. S.,Emanuel', O. N.,Skibida, I. P.
-
p. 1651 - 1656
(2007/10/02)
-
- REDUCTIVE ACTIVATION OF ARENES. VI. REACTION OF THE PRODUCT OF THE ONE-ELECTRON REDUCTION OF NITROBENZENE BY SODIUM IN LIQUID AMMONIA WITH ISOMERIC BUTYL IODIDES
-
The reaction of the product of the reduction of nitrobenzene by one equivalent of sodium in liquid ammonia with n-butyl, sec-butyl, and isobutyl iodides leads to the corresponding N,O-dialkylphenylhydroxylamines as the major products through an SN2 mechanism.The analogous reaction with tert-butyl iodide gives approximately equal amounts of products of butylation in the benzene ring, namely, 4-tert-butylnitrobenzene and 4-tert-butylaniline, and at the nitro-group, namely, N-tert-butylaniline and N-tert-butylphenylhydroxylamine.The formation of these N-tert-butyl produ cts is probably the result of the transfer of an electron from the nitrobenzene radical-anion to the alkyl iodide and subsequent recombination of the tert-butyl radical with the nitrobenzene radical-anion.The increase in the fraction of tert-butylation at the nitro group in going from hexamethylphosphorotriamide or its mixture with tetrahydrofuran as the solvent to liquid nitrogen is probably a consequence of a greater role for interaction with the medium, which affects the distribution of the spin density in the nitrobenzene radical-anion or on the relative stability of the transition states responsible for the competing recombination pathways.
- Selivanov, V. A.,Shteingarts, V. D.
-
p. 1654 - 1662
(2007/10/02)
-
- Ozone-mediated Nitration of Alkylbenzenes and Related Compounds with Nitrogen Dioxide
-
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
-
p. 1591 - 1598
(2007/10/02)
-
- Transition-State Polarization in Cleavage of C-C Bonds in Radical Anions
-
The substituent effect on the rate of C-C bond cleavage in radical anions of 1-(4-nitrophenyl)-2-(substituted-phenyl)-1,1,2,2-tetraethylethanes has been explored.The data provide evidence for two distinctive modes of bond scission.One mode is characterized by a significant negative charge transfer across the scissile bond in the transition state.Such polarization of the transition state is in contradiction to the prediction based on the fragments' stability.The second mode, dominant in cases where the charge shift leads to negative charge accumulation on an already electron-rich fragment, involves a ?* radical anion.Both modes point to a general kinetic preference for a cleavage of radical anions that allows for charge delocalization across the scissile bond.
- Maslak, Przemyslaw,Narvaez, Javier N.,Kula, Jozef,Malinski, David S.
-
p. 4550 - 4559
(2007/10/02)
-
- THE SELECTIVITY OF ELECTROPHILIC AROMATIC NITRATION AND THE EFFECT OF THE ORGANIC SOLVENTS
-
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
-
p. 2719 - 2730
(2007/10/02)
-
- PARA-SELECTIVE MONONITRATION OF ALKYLBENZENES UNDER MILD CONDITIONS BY USE OF BENZOYL NITRATE IN THE PRESENCE OF A ZEOLITE CATALYST
-
Toluene and other alkylbenzenes are mononitrated in essentially quantitative yield at ambient temperature by benzoyl nitrate in the presence of aluminium/proton exchanged large port mordenite; the reaction is highly para-selective.
- Smith, Keith,Fry, Karl,Butters, Michael,Nay, Barry
-
p. 5333 - 5336
(2007/10/02)
-
- REGIOSELECTIVE NITRATION OF AROMATIC HYDROCARBONS BY METALLIC NITRATES ON THE K10 MONTMORILLONITE UNDER MENKE CONDITIONS
-
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
-
p. 1843 - 1846
(2007/10/02)
-
- Electrophilic Aromatic Nitration in the Gas Phase
-
Aromatic nitration by MeO+(H)NO2, in essence nitronium ion solvated by one methanol molecule, has been studied in the gas phase by using an integrated approach, based on the coordinate application of ICR, Cl, and CID mass spetrometric methods with a highly complementary radiolytic technique.The latter can be used in gases at atmospheric pressure and allows direct evaluation of key mechanistic features, in particular of substrate and positional selectivity.The results resolve early discrepancies between gas-phase and liquid-phase studies, characterizing the reaction as a typical, well-behaved electrophilic substitution of moderate selectivity.The date from the gas-phase nitration of ten monosubstituted benzenes fit a Hammett's type linear plot, characterized by a ρ value of -3.87.The correlation does not extend to highly activated substrates, such as anisole and mesitylene, since the nitration rate tends to a limiting value that cannot be increased by further enhancing the activation of the substrate, exactly as in "encounter-rate" nitrations occurring in solution.The mechanism and the energetics of the gas-phase nitration have been investigated, and the relative stability of the charged intermediates involved, in particular of the isomeric protonated nitrobenzenes, has been estimated by theoretical approaches at two different levels, using STO-3G minimal basis and 4-31G split-valence basis sets.
- Attina, Marina,Cacace, Fulvio,Yanez, Manuel
-
p. 5092 - 5097
(2007/10/02)
-
- RADICAL-ANIONS OF AROMATIC COMPOUNDS. VII. REACTION OF THE PRODUCTS FROM THE REDUCTION OF NITROBENZENE BY SODIUM WITH ISOPROPYL AND tert-BUTYL IODIDES
-
The reaction of the products from the reduction of nitrobenzene by one and two equivalents of sodium with isopropyl iodides leads to the formation of N,O-diisopropylphenylhydroxylamine, while the reaction with tert-butyl iodide leads to p-(tert-butyl)nitrobenzene.Such a change in the nature of the reaction product in the transition from the primary and secondary alkyl halides to the tertiary alkyl halides clearly results from a change in the SN2 mechanism to the SRN1 mechanism, involving transfer of an electron from the radical-anion or dianion of nitrobenzene to the alkyl halide.The formation of considerable amounts of azoxybenzene in the reaction with tert-butyl iodide shows that the dianion and, to a lesser degree, the radical-anion of nitrobenzene exhibit basic characteristics.
- Danilova, N. K.,Shteingarts, V. D.
-
p. 701 - 708
(2007/10/02)
-
- Reactions of Cerium(IV) Ammonium Nitrate with Aromatic Compounds in Acetonitrile. Part 2. Nitration; Comparison with Reactions of Nitric acid
-
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.
-
p. 965 - 970
(2007/10/02)
-
- ELECTRON TRANSFER FREE RADICAL MECHANISM IN THE REACTIONS OF ARENEDIAZONIUM CATIONS WITH GRIGNARD REAGENTS
-
The major pathway in the reactions of arenediazonium cations with certain Grignard reagents is found to involve an electron transfer from the latter to the ?-system of the former reactant and radicals are the immediate precursors of the final products.
- Singh, P. R.,Khanna, R. K.,Jayaraman, B.
-
p. 5475 - 5478
(2007/10/02)
-
