Xn:Harmful;
106-43-4Relevant articles and documents
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Hodgson,Foster
, p. 747 (1942)
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Kaluszyner,Reuter
, p. 5126 (1953)
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Barkenbus,Hopkins,Allen
, p. 2452 (1939)
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Norris,Turner
, p. 2128,2130 (1939)
The base-induced fragmentation of N,N-dibenzyl-N'-aryltriazenes
Lormann, Matthias E. P.,Dahmen, Stefan,Avemaria, Frank,Lauterwasser, Frank,Bra?se, Stefan
, p. 915 - 918 (2002)
Deprotonation of N,N-dibenzyl-N'-aryltriazenes, either in liquid phase or on solid support, by a strong base (n-BuLi or LDA) leads to fragmentation of the N-N single bond to give an imine and a diazenyl anion, which decomposes by loss of nitrogen to the parent aryl anion. The imine is deprotonated to give a 2-aza allyl anion, which is subsequently trapped by electrophiles. As an overall result, this fragmentation of the T1 triazene anchoring group represents a new traceless cleavage mode of this linker. The same mode of fragmentation was observed for the T2 linker leading to 2-aza allyl anions in liquid phase. The dibenzylamino moiety is apparently crucial since pyrrolidinodiazenylarenes can be metallated at the heterocycle without cleavage.
Kinetic and Mechanisms of the Homogeneous, Unimolecular Elimination of Phenyl Chloroformate and p-Tolyl Chloroformate in the Gas Phase
Lezama, Jesus,Chuchani, Gabriel
, p. 664 - 670 (2015)
The gas-phase elimination of phenyl chloroformate gives chlorobenzene, 2-chlorophenol, CO2, and CO, whereasp-tolyl chloroformate produces p-chlorotoluene and 2-chloro-4-methylphenol CO2 and CO. The kinetic determination of phenyl chloroformate (440-480oC, 60-110 Torr) and p-tolyl chloroformate (430-480°C, 60-137 Torr) carried out in a deactivated static vessel, with the free radical inhibitor toluene always present, is homogeneous, unimolecular and follows a first-order rate law. The rate coefficient is expressed by the following Arrhenius equations: Phenyl chloroformate: Formation of chlorobenzene, log kI = (14.85 ± 0.38) - (260.4 ± 5.4) kJ mol-1 (2.303RT)-1; r = 0.9993 Formation of 2-chlorophenol, log kII = (12.76 ± 0.40) - (237.4 ± 5.6) kJ mol-1(2.303RT)-1; r = 0.9993 p-Tolyl chloroformate: Formation of p-chlorotoluene: log kI = (14.35 ± 0.28) - (252.0 ± 1.5) kJ mol-1 (2.303RT)-1; r = 0.9993 Formation of 2-chloro-4-methylphenol, log kII = (12.81 ± 0.16) - (222.2 ± 0.9) kJ mol-1(2.303RT)-1; r = 0.9995 The estimation of the kI values, which is the decarboxylation process in both substrates, suggests a mechanism involving an intramolecular nucleophilic displacement of the chlorine atom through a semipolar, concerted four-membered cyclic transition state structure; whereas the kII values, the decarbonylation in both substrates, imply an unusual migration of the chlorine atom to the aromatic ring through a semipolar, concerted five-membered cyclic transition state type of mechanism. The bond polarization of the C-Cl, in the sense Cδ+Clδ-, appears to be the rate-determining step of these elimination reactions.
New Reagent Systems for Electrophilic Chlorination of Aromatic Compounds: Organic Chlorine-Containing Compounds in the Presence of Silica
Smith, Keith,Butters, Michael,Paget, Walter E.,Nay, Barry
, p. 1155 - 1156 (1985)
In the presence of silica, a number of chlorine-containing organic compounds, such as N,N-dichlorourethane, dichloramine-T, and t-butyl hypochlorite, become active electrophilic reagents capable of controlled monochlorination of aromatic compounds under mild conditions; for example, t-butyl hypochlorite/silica chlorinates alkylbenzenes, naphthalene, and anisole readily at 25 deg C; N,N-dichlorourethane/silica chlorinates benzene within 2 days 50 deg C.
Solvolysis of some arenediazonium salts in binary EtOH/H2O mixtures under acidic conditions
Pazo-Llorente, Roman,Bravo-Diaz, Carlos,Gonzalez-Romero, Elisa
, p. 3421 - 3428 (2003)
We have determined the product distribution, the rate constants for dediazoniation product formation, and the solvolytic rate constants for 2-, 3-, and 4-methylbenzenediazonium ions (2-, 3-, and 4-MBD, respectively) loss in acidic ethanol/water mixtures over the whole composition range by a combination of spectrophotometric (UV/Vis) and high performance liquid chromatography (HPLC) measurements. The observed rate constants (kobs) for substrate loss are equal to those for product formation, and they remain essentially constant (2-MBD) with changing solvent composition but increase by a factor of ≈2 (4MBD) on going from water to 100% EtOH. Up to four dediazoniation products - cresols (ArOH), chlorotoluene (ArCl), methylphenetole (ArOEt), and toluene (ArH) - were detected, depending on the solvent composition; the major dediazoniation products were the ArOH and ArOEt derivatives. The product selectivity (S) of the reaction towards nucleophiles is low and essentially constant with changing solvent composition, and good linear correlations between log kobs and Yc1 (solvent ionizing power) were observed for the three ArN2+ ions. All data are consistent with the rate-determining formation of an aryl cation, which reacts immediately with available nucleophiles. The data suggest that the distribution of neutral and anionic nucleophiles in the neighborhood of the ground state arenediazonium ion remains essentially unchanged upon dediazoniation, the observed product distribution reflecting the concentrations of nucleophiles in their immediate environment (i.e., in the first solvation shells of the arenediazonium ions). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Synthesis, Structure, and Reductive Elimination of Cationic Monoarylpalladium(IV) Complexes Supported by a Tripodal Oxygen Ligand
So, Yat-Ming,Au-Yeung, Ka-Chun,Sung, Herman H. -Y.,Williams, Ian D.,Leung, Wa-Hung
, p. 2928 - 2935 (2017)
Cationic monoaryl–PdIV complexes supported by the Kl?ui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]– (LOEt–) were synthesized, and their reductive elimination was studied. Treatment of trans-[Pd(PPh3)2(Ar)(I)] and [{Pd(η2-ppytBu)Cl}2] [ppytBuH = 2-(4-tert-butylphenyl)pyridine] with [AgLOEt] afforded [Pd(Ar)(PPh3)(η2-LOEt)] [Ar = Ph (1), p-tolyl (2)] and [Pd(η2-ppytBu)(η2-LOEt)] (3), respectively. Chlorination of 1, 2, and 3 with PhICl2 in the presence of NH4PF6 afforded the cationic aryl–PdIV chloride complexes [Pd(Ph)(PPh3)(Cl)(LOEt)](PF6) (4), [Pd(p-tolyl)(PPh3)(Cl)(LOEt)](PF6) (5), and [Pd(η2-ppytBu)(Cl)(LOEt)](PF6) (6), respectively. Complexes 4 and 5 underwent C(sp2)–Cl elimination at 40 °C in acetonitrile to give a PdII–LOEt species and the corresponding chloroarene. On the other hand, the C(sp2)–Cl elimination of 6 occurred at room temperature and afforded a PdII species, presumably [Pd(ClppytBuH)(LOEt)](PF6), which further reacted with PhICl2 to yield [Pd(η2-ClppytBu)Cl(LOEt)](PF6) (7) [ClppytBuH = 2-(4-tert-butyl-2-chlorophenyl)pyridine]. The structures of complexes 1, 4, 6, and 7 were established by X-ray crystallography.
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Leicester
, p. 1901 (1935)
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pH effects on ethanolysis of some arenediazonium ions: Evidence for homolytic dediazoniation proceeding through formation of transient diazo ethers
Pazo-Llorente, Roman,Bravo-Diaz, Carlos,Gonzalez-Romero, Elisa
, p. 3221 - 3226 (2004)
The effects of pH on the observed rate constants (kobsd.) and on the solvolytic dediazoniation product distributions of ethanolysis of 2-, 3-, and 4-methylbenzenediazonium ions (2MBD, 3MBD, and 4MBD, respectively) were determined by a combination of spectrophotometric (UV/Vis) and Chromatographic (HPLC) techniques. The variation of both kobsd. and product yields with pH follow S-shaped curves with inflection points at pH ≈ 3.6, depending on solvent composition. With increasing pH, kobsd. values increase by factors of up to about 4 (2MBD), about 3 (3MBD), and about 50 (4MBD) with respect to the kobsd. values at low pH. HPLC analyses of the reaction mixtures show that only heterolytic products are obtained at low pH, indicating that solvolytic dediazoniation takes place through an ionic mechanism, but an increase in pH favors homolytic dediazoniation, with quantitative conversion into the reduction product toluene being obtained at pH ≥ 6 (4MBD), indicating that a turnover from the heterolytic to the homolytic mechanisms is taking place under experimental conditions under which insignificant amounts of EtO- or OH- should be present in solution. The obtained S-shaped profiles suggest that the initiation process of the homolytic pathway is the result of the formation of a highly unstable transient diazo ether complex and not by direct electron transfer from the solvent (EtOH) to the arenediazonium ions as is currently believed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Electrophilic Aromatic Substitution. Part 30. The Kinetics and Products of the Solvolyses in Aqueous Sulphuric Acids of 5-Chloro-2-methyl-2-nitrocyclohexa-3,5-dienyl Acetate: the Occurence of AAC2 and AAl1 Solvolyses, and of an Acid-catalysed Elimination of Nitrous Acid, and the...
Bloomfield, Colin,Moodie, Roy B.,Schofield, Kenneth
, p. 1793 - 1802 (1983)
Good first order kinetics of solvolysis of the above-named diene in water and in 6.5-43.6percent H2SO4 at 25 deg C, and in water and in 15.2-58.8percent H2SO4 at 5 deg C have been observed.The yields of 4-chlorotoluene, 5-chloro-2-methylphenyl acetate, 5-chloro-2-methylphenol, 4-chloro-2-nitrotoluene, 4-chloro-3-nitrotoluene, and 4-methyl-2-nitrophenol produced in water and in 21.5-92.4percent H2SO4 at 25 deg C in the presence of sulphanilic acid or hydrazinium sulphate, and additionally of 2- and 4-nitroanisole when anisole was also added, have been measured.The solvolysis proceeds by an acid-catalysed elimination of nitrous acid (confirming a tentative conclusion in another case), which competes with AAC2 and AAL1 ester solvolyses.With increasing acidity the solvolyses become dominant, the AAL1 reaction increasingly so.The small yield of 4-chloro-3-nitrotoluene comes from a thermal reaction of the diene unrelated to the elimination and solvolyses.The AAL1 reaction generates the ipso-Wheland intermediate (WiMe) that is also formed in the nitration of 4-chlorotoluene.The intermediate reacts by return to 4-chlorotoluene and nitronium ion (which can be captured by anisole), by 1,2-and 1,4-nucleophilic capture by water (giving 5-chloro-2-methylphenol and 4-methyl-2-nitrophenol, respectively), and by 1,2-rearrangement to 4-chloro-2-nitrotoluene.The first of these reactions never accounts for more than about 12percent of the WiMe and competition between capture and rearrangement moves strongly in favour of the latter with increasing acidity.Re-examination of the nitration of 4-chlorotoluene has revealed products arising from 1,2- and 1,4-capture of WiMe, previously overlooked.An improved assessmentof positional reactivities shows 59percent of primary attack by nitronium ion to occur at C-Me in 63percent H2SO4.
Isolation, structure, and reactivity of a novel chloro-arenium cation for electrophilic (transfer) chlorinations
Rathore,Loyd,Kochi
, p. 8414 - 8415 (1994)
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Miller
, p. 1243 (1973)
Regioselective Para Halogenation of Substituted Benzenes with Benzeneseleninyl Chloride and Aluminum Halide
Kamigata, Nobumasa,Satoh, Takeshi,Yoshida, Masato,Matsuyama, Haruo,Kameyama, Masayuki
, p. 2226 - 2228 (1988)
In the presence of aluminum halide, benzeneseleninyl chloride is an efficient regioselective halogenating reagent for activated aromatics such as toluene, phenol, anisole, phenetole, diphenyl ether, and N,N-dimethylaniline.Benzene and chlorobenzene are not halogenated under similar conditions.
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Brown,Stock
, p. 5175,5178 (1957)
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Trichloroisocyanuric acid in 98% sulfuric acid: A superelectrophilic medium for chlorination of deactivated arenes
Mendo?a, Gabriela Fonseca,Senra, M?nica Rufino,Esteves, Pierre M.,De Mattos, Marcio C.S.
, p. 176 - 181 (2011)
Trichloroisocyanuric acid (TCCA) reacts with arenes and its reactivity is highly affected by the acid strength of the reaction medium. Deactivated arenes are efficiently chlorinated by TCCA in H2SO4. Our results, along with DFT calculations and 13C NMR spectrometry suggest the formation of a monoprotonated TCCA superelectrophile as the reactive species that can efficiently transfer electrophilic Cl+ to even very weak nucleophiles, such as m-dinitrobenzene.
Phosphonium nitrate ionic liquid catalysed electrophilic aromatic oxychlorination
Noe, Marco,Perosa, Alvise,Selva, Maurizio,Zambelli, Luca
, p. 1654 - 1660 (2010)
Trioctylmethylphosphonium nitrate (P8,8,8,1NO3), an ionic liquid made via a green synthesis, catalyses electrophilic aromatic chlorination of arenes with HCl and air at 80 °C. The aromatic oxychlorination is truly catalytic in nitrate, proceeds without added solvents, and uses atmospheric oxygen as oxidant. The extent of chlorination can be controlled to yield selectively mono or dichlorinated products, and the ionic liquid catalyst can be recycled. Dependence of the chlorination rate on HCl and nitrate concentrations as well as on the rate of re-oxidation of the nitrogen intermediates by air, allowed us to propose a reaction mechanism.
An unprecedented deoxygenation protocol of benzylic alcohols using bis(1-benzotriazolyl)methanethione
Kumar, Dhananjay,Singh, Anoop S.,Tiwari, Vinod K.
, p. 31584 - 31593 (2015)
A facile and regioselective two-step protocol for the deoxygenation of benzylic alcohols using bis(benzotriazole)methanethione has been devised. Benzotriazole derivatives, namely, benzyloxythioacylbenzotriazoles (ROCSBt), on reaction with silanes or Bu3SnH under microwave irradiation or conventional heating undergo a free radical β-scission of C-O bond instead of N-N bond (benzotriazole ring cleavage) to afford a deoxy product. The methodology has various applications because it selectively deoxygenates benzylic alcohols with the aid of a relatively nontoxic (TMS)3SiH reagent as an acceptable alternate to Bu3SnH.
Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
supporting information, p. 9029 - 9039 (2021/06/28)
Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
Arylation ofgem-difluoroalkenes using a Pd/Cu Co-catalytic system that avoids β-fluoride elimination
Yuan, Kedong,Feoktistova, Taisiia,Cheong, Paul Ha-Yeon,Altman, Ryan A.
, p. 1363 - 1367 (2021/02/12)
PdII/CuIco-catalyze an arylation reaction ofgem-difluoroalkenes using arylsulfonyl chlorides to deliver α,α-difluorobenzyl products. The reaction proceeds through a β,β-difluoroalkyl-Pd intermediate that typically undergoes unimolecular β-F elimination to deliver monofluorinated alkene products in a net C-F functionalization reaction. However to avoid β-F elimination, we offer the β,β-difluoroalkyl-Pd intermediate an alternate low-energy route involving β-H elimination to ultimately deliver difluorinated products in a net arylation/isomerization sequence. Overall, this reaction enables exploration of new reactivities of unstable fluorinated alkyl-metal species, while also providing new opportunities for transforming readily available fluorinated alkenes into more elaborate substructures.
