- Cross-Coupling through Ag(I)/Ag(III) Redox Manifold
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In ample variety of transformations, the presence of silver as an additive or co-catalyst is believed to be innocuous for the efficiency of the operating metal catalyst. Even though Ag additives are required often as coupling partners, oxidants or halide scavengers, its role as a catalytically competent species is widely neglected in cross-coupling reactions. Most likely, this is due to the erroneously assumed incapacity of Ag to undergo 2e? redox steps. Definite proof is herein provided for the required elementary steps to accomplish the oxidative trifluoromethylation of arenes through AgI/AgIII redox catalysis (i. e. CEL coupling), namely: i) easy AgI/AgIII 2e? oxidation mediated by air; ii) bpy/phen ligation to AgIII; iii) boron-to-AgIII aryl transfer; and iv) ulterior reductive elimination of benzotrifluorides from an [aryl-AgIII-CF3] fragment. More precisely, an ultimate entry and full characterization of organosilver(III) compounds [K]+[AgIII(CF3)4]? (K-1), [(bpy)AgIII(CF3)3] (2) and [(phen)AgIII(CF3)3] (3), is described. The utility of 3 in cross-coupling has been showcased unambiguously, and a large variety of arylboron compounds was trifluoromethylated via [AgIII(aryl)(CF3)3]? intermediates. This work breaks with old stereotypes and misconceptions regarding the inability of Ag to undergo cross-coupling by itself.
- Demonti, Luca,Mézailles, Nicolas,Nebra, Noel,Saffon-Merceron, Nathalie
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supporting information
p. 15396 - 15405
(2021/10/12)
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- Method for hydrolyzing diarylether compound to generate aryl phenol compound
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The invention discloses a method for hydrolyzing a diarylether compound to generate an arylphenol compound. According to the method, visible light is utilized to excite a photosensitizer for catalysis. In a reaction solvent, the raw material in the formula (1) breaks a C (sp2)-O bond under the auxiliary action of acid, and hydrolysis is performed to obtain the bimolecular aryl phenol compounds in the formula (3) and the formula (4). The method can catalyze the reaction at room temperature, is green and environment-friendly, and is easy to operate; the universality is wide, the reaction yield is relatively high, and the tolerance of functional groups is strong; the synthesis method not only can realize small-scale hydrolysis conversion of various diarylether compounds, but also can realize hydrolysis of herbicidal ether, triclosan and a lignin template substrate, and even can realize large-scale hydrolysis of triclosan and the lignin template substrate to realize gram-level degradation. A new strategy is provided for recovering phenol derivatives through lignin hydrolysis, degrading pesticides and purifying wastewater containing a degerming agent or herbicide. The method has wide application prospect and use value.
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Paragraph 0111-0114
(2021/09/29)
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- Aerobic photooxidative hydroxylation of boronic acids catalyzed by anthraquinone-containing polymeric photosensitizer
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We report herein the synthesis of a polymeric photosensitizer and its application in aerobic photooxidative hydroxylation of boronic acids. The polymeric photosensitizer was synthesized by the condensation of anthraquinone-2-carbonyl chloride (AQ-2-COCl) with poly (2-hydroxyethyl methacrylate) (PHEMA). The photo-oxidative hydroxylation of boronic acids using anthraquinone-containing-poly (2-hydroxyethyl methacrylate) (AQ-PHEMA) was then explored and shown to exhibit high efficiency and broad scope. Moreover, AQ-PHEMA could be easily recovered and reused for more than 20 times without significant loss of the catalytic activity.
- Chen, Yang,Ding, Aishun,Hu, Jianhua
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p. 7927 - 7932
(2020/03/11)
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- Visible-light-induced Pd-catalyzed: Ortho -trifluoromethylation of acetanilides with CF3SO2Na under ambient conditions in the absence of an external photocatalyst
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A visible-light-induced Pd-catalyzed ortho-trifluoromethylation of acetanilides with CF3SO2Na was developed. The reaction proceeded smoothly at room temperature in air without any external photocatalyst or additive, providing the desired products in moderate to good yields with good functional group tolerance and regioselectivity.
- Zou, Long,Li, Pinhua,Wang, Bin,Wang, Lei
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p. 3737 - 3740
(2019/04/01)
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- Photoinduced Hydroxylation of Organic Halides under Mild Conditions
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Presented in this paper is photoinduced hydroxylation of organic halides, providing a mild access to a range of functionalized phenols and aliphatic alcohols. These reactions generally proceed under mild reaction conditions with no need for a photocatalyst or a strong base and show a wide substrate scope as well as excellent functional group tolerance. This work highlights the unique role of NaI that allows a challenging transformation to proceed under mild reaction conditions.
- Cai, Yue-Ming,Xu, Yu-Ting,Zhang, Xin,Gao, Wen-Xia,Huang, Xiao-Bo,Zhou, Yun-Bing,Liu, Miao-Chang,Wu, Hua-Yue
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supporting information
p. 8479 - 8484
(2019/10/16)
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- Regioselectivity of Hydroxyl Radical Reactions with Arenes in Nonaqueous Solutions
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The regioselectivity of hydroxyl radical addition to arenes was studied using a novel analytical method capable of trapping radicals formed after the first elementary step of reaction, without alteration of the product distributions by secondary oxidation processes. Product analyses of these reactions indicate a preference for o- over p-substitution for electron donating groups, with both favored over m-addition. The observed distributions are qualitatively similar to those observed for the addition of other carbon-centered radicals, although the magnitude of the regioselectivity observed is greater for hydroxyl. The data, reproduced by high accuracy CBS-QB3 computational methods, indicate that both polar and radical stabilization effects play a role in the observed regioselectivities. The application and potential limitations of the analytical method used are discussed.
- Moores, Lee C.,Kaur, Devinder,Smith, Mathew D.,Poole, James S.
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supporting information
p. 3260 - 3269
(2019/03/11)
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- An efficient and chemoselective deprotection of aryl tert-butyldimethylsilyl (TBDMS) ethers by NaCN
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Phenolic tert-butyldimethylsilyl (TBDMS) ethers can be deprotected to yield phenols in excellent yield using sodium cyanide (NaCN) as catalyst in ethanol. The deprotectation of various phenolic TBDMS ethers were found to be very convenient, fast, high yielding and chemoselective.
- Qiao, Xue-Jun,Hou, Xiao,Fang, Wu-Hong,Bao, Xue-Fei,Chen, Guo-Liang
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p. 899 - 904
(2016/05/19)
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- Selective Aromatic C-H Hydroxylation Enabled by η6-Coordination to Iridium(III)
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We report an aromatic C-H hydroxylation protocol in which the arene is activated through η6-coordination to an iridium(III) complex. η6-Coordination of the arene increases its electrophilicity and allows for high positional selectivity of hydroxylation at the site of least electron density. Through investigation of intermediate η5-cyclohexadienyl adducts and arene exchange reactions, we evaluate incorporation of arene π-activation into a catalytic cycle for C-H functionalization.
- D'Amato, Erica M.,Neumann, Constanze N.,Ritter, Tobias
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supporting information
p. 4626 - 4631
(2015/10/06)
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- Solvent-free one-step photochemical hydroxylation of benzene derivatives by the singlet excited state of 2,3-dichloro-5,6-dicyano-p-benzoquinone acting as a super oxidant
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Photoinduced hydroxylation of neat deaerated benzene to phenol occurred under visible-light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), which acts as a super photooxidant in the presence of water. Photocatalytic solvent-free hydroxylation of benzene derivatives with electron-withdrawing substituents such as benzonitrile, nitrobenzene, and trifluoromethylbenzene used as neat solvents has been achieved for the first time by using DDQ as a super photooxidant to yield the corresponding phenol derivatives and 2,3-dichloro-5,6-dicyanohydroquinone (DDQH2) in the presence of water under deaerated conditions. In the presence of dioxygen and tert-butyl nitrite, the photocatalytic hydroxylation of neat benzene occurred with DDQ as a photocatalyst to produce phenol. The photocatalytic reactions are initiated by oxidation of benzene derivatives with the singlet and triplet excited states of DDQ to form the corresponding radical cations, which associate with benzene derivatives to produce the dimer radical cations, which were detected by the femto- and nanosecond laser flash photolysis measurements to clarify the photocatalytic reaction mechanisms. Radical cations of benzene derivatives react with water to yield the OH-adduct radicals. On the other hand, DDQC?- produced by the photoinduced electron transfer from benzene derivatives reacts with the OH-adduct radicals to yield the corresponding phenol derivatives and DDQH2. DDQ is recovered by the reaction of DDQH2 with tert-butyl nitrite when DDQ acts as a photocatalyst for the hydroxylation of benzene derivatives by dioxygen.
- Ohkubo, Kei,Hirose, Kensaku,Fukuzumi, Shunichi
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supporting information
p. 2855 - 2861
(2015/02/05)
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- The Hydroxylation of Aromatics with Oxygen by Vanadium Catalysts Supported on N-doped Carbon Materials
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Vanadium catalysts supported on N-doped carbon materials (CN) were prepared and the catalyst VOSiW showed high activity for the hydroxylation of various aromatics with O2. Aromatics with electron-withdrawing groups such as CN, NO2, COOH, CF3, COCH3 and aromatic halides (F, Cl and Br) were oxygenated to the corresponding phenols in considerable yields. The CN materials were not only indispensable for the reusability of the vanadium catalyst VOSiW, but also favorable to the high catalytic activity. The VOSiW catalyst is ready for the hydroxylation of aromatics with O2 as both V4+ and V5+ species are coexisted in the VOSiW catalyst.
- Li, Yan,Li, Bing,Geng, Longfei,Wang, Jun,Wang, Yong,Huang, Jun
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p. 1014 - 1021
(2015/08/04)
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- A novel catalytic process for trifluoromethylation of bromoaromatic compounds
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The palladium-catalyzed trifluoromethylation of aryl bromides has been achieved in micellar media. The micellar conditions result in enhanced yields and are applicable to bromoaromatics with ketone, aldehyde, hydroxyl and amine functionalities.
- Samant, Bhupesh S.,Kabalka, George W.
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supporting information; experimental part
p. 7236 - 7238
(2011/08/22)
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- Copper-catalyzed trifluoromethylation of aryl boronic acids using a CF 3+ reagent
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A copper-catalyzed process for trifluoromethylation of aryl, heteroaryl, and vinyl boronic acids has been developed. The reaction is conducted under mild conditions and shows tolerance to moisture and a variety of functional groups.
- Xu, Jun,Luo, Dong-Fen,Xiao, Bin,Liu, Zhao-Jing,Gong, Tian-Jun,Fu, Yao,Liu, Lei
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supporting information; experimental part
p. 4300 - 4302
(2011/06/21)
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- Simple and efficient CuI/PEG-400 system for hydroxylation of aryl halides with potassium hydroxide
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This work reports a simple and efficient CuI/PEG-400 system for hydroxylation of aryl halides with potassium hydroxide. This protocol offers a direct transformation of aryl iodides or bromides to substituted phenols in great diversity. A very wide variety of functional groups are tolerated on aryl halides partners such as carboxyl, aldehyde and hydroxyl group.
- Chen, Junmin,Yuan, Tangjun,Hao, Wenyan,Cai, Mingzhong
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experimental part
p. 1463 - 1465
(2012/06/18)
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- CF3 oxonium salts, O-(trifluoromethyl)dibenzofuranium salts: In situ synthesis, properties, and application as a real CF3+ species reagent
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(Chemical Equation Presented) We report in situ synthesis of the first CF3 oxonium salts, thermally unstable O-(trifluoromethyl)- dibenzofuranium salts, which furthermore have different counteranions (BF 4-, PF6-, SbF6 -, and Sb2F11-) and ring substituents (tert-butyl, F, and OCH3), by photochemical decomposition of the corresponding 2-(trifluoromethoxy)biphenylyl-2′- diazonium salts at -90 to -100°C. The yields markedly increased in the order of BF4- 6- 6- 2F11-. The CF3 oxonium salts were fully assigned by means of 1H and 19F NMR spectroscopy at low temperature. The CF3 salts decomposed to form CF4 and dibenzofurans. The half-life times at -60°C of the 2-tert-butyl salts having different counteranions were 29 min for BF4- salt 2d, 36 min for PF6- salt 2c, 270 min for SbF6- salt 2a, and 415 min for Sb2F11- salt 2b. Those at -60°C of the Sb2F11- salts having different 2-substituents were 13 min for F salt 3b, 63 min for H (unsubstituted) salt 1b, and 415 min for tert-butyl salt 2b. Thus, the stability of the CF3 oxonium salts increased in the order of BF4- 6 - 6- 2F 11- and F 3+ species source to the direct O- and N-trifluoromethylations of alcohols, phenols, amines, anilines, and pyridines under very mild conditions. The thermal decomposition method with a mixture of diazonium salt 17a and aryl- or alkylsulfonic acids, pyridine, or pyridines having an electron-withdrawing group also afforded CF3O or CF 3N products. The trifluoromethylation mechanism is discussed and an SN2 mechanism containing the transient formation of free CF 3+ is proposed. Thus, the present study has demonstrated that the exceedingly reactive CF3+ species can be generated much easier than the CH3+ species, contrary to the common sense that CF3+ is extremely difficult to generate in solution.
- Umemoto, Teruo,Adachi, Kenji,Ishihara, Sumi
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p. 6905 - 6917
(2008/02/11)
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- Oxidation of Carbon-Silicon Bonds: The Dramatic Advantage of Strained Siletanes
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(Matrix presented) Herein we report on the use of siletanes as substrates for the oxidation of carbon-silicon bonds. These tetraalkylsilanes are easy to handle yet susceptible to rapid ring opening and oxidation upon exposure to aqueous fluoride and peroxide. This combination of stability and reactivity presents many practical benefits, including compatibility with silicon protecting groups and electron-rich aromatic rings.
- Sunderhaus, James D.,Lam, Hubert,Dudley, Gregory B.
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p. 4571 - 4573
(2007/10/03)
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- 6-(Nonsubstituted or substituted) phenoxy picolinic acids, process of preparing the same, and agricultural/horticultural germicides containing the same
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An agricultural or horticultural fungicide containing 6-(unsubstituted or substituted) phenoxy picolinic acid represented by the general formula (I), as an effective ingredient. wherein R is a halogen atom, a C1to C4alkyl group, a C1to C4haloalkyl group, a C1to C4alkoxy group, a C1to C4haloalkoxy group, a C1to C4alkylthio group, a C1to C4alkylamino group, a di(C1to C4alkyl)amino group or a C7to C8aralkyl(C1to C4alkyl)amino group; n2is an integer of 0 to 3; Y is a C1to C4alkyl group, a C1to C4haloalkyl group, a C1to C4alkoxy group, a C1to C4haloalkoxy group, a C1to C4alkylthio group, a C1to C4haloalkylthio group or a halogen atom; and m is an integer of 0 to 5, and when m and n2are not less than 2, Rs and Ys may be the same or different, respectively. The compound is useful as an effective ingredient of agricultural or horticultural fungicides.
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- Acid-catalysed Aromatisation of Benzene cis-1,2-dihydrodiols: a Carbocation Transition State poorly stabilised by Resonance
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Acid-catalysed dehydration of 3-substituted benzene cis-1,2-dihydrodiols exhibits a Hammett plot with ρ=-8.2, consistent with reaction via a benzenonium ion-like intermediate; however, correlation of +M resonance substituents such as Me and MeO by ?p rather than ?+ constants indicates a marked imbalance between resonance and inductive stabilisation of the transition state.
- Boyd, Derek R.,Blacker, John,Byrne, Briege,Dalton, Howard,Hand, Mark V.,et al.
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p. 313 - 314
(2007/10/02)
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- Gas Phase Oxygenation of Benzene Derivatives at ca 300 K With O(3P) Atoms Produced by Microwave Discharge of N2O. Part 1. Rates and Mechanism of Phenol Formation
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The reactions of O(3P) with benzene derivatives C6H5Z (Z=H, Cl, F, CH3, CF3, and OCH3) have been studied in a flow reactor at ambient temperature in a helium atmosphere, using microwave discharge of nitrous oxide as the source of oxygen atoms.The main products are the substituted phenols; substituted cyclohexadienes were also observed. ipso-Substitution, with formation of phenol, is also an important path, except in the reaction with fluorobenzene and trifluorotoluene.The oxygen atom adds to the benzene ring to form a triplet adduct, which can isomerize to phenol or lose an H-atom, producing a phenoxyl radical.This phenoxy radical also leads to phenol via disproportionation with a cyclohexadienyl radical, the latter arising from H-atom addition to the substrate.Relative rates for O-addition were determined by competition experiments with benzene as a reference.A Hammett plot, using ? constants for the meta- and para-positions demonstrated the electrophilic character of O(3P).A good correlation was found for the para-positions, with ρ=-1.1.
- Sol, Veronica M.,Drunen, Michiel A. van,Louw, Robert,Mulder, Peter
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p. 937 - 942
(2007/10/02)
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- Reactions of Trifluoromethyl Bromide and Related Halides: Part 10. Perfluoroalkylation of Aromatic Compounds induced by Sulphur Dioxide Radical Anion Precursors
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Perfluoroalkylation of electron-rich aromatic compounds with trifluoromethyl bromide, or long-chain perfluoroalkyl iodides, was performed in the presence of sodium dithionite or zinc-sulphur dioxide.This alkylation occurred at the ortho and para positions relative to the amino or hydroxy substitutent.Pyrroles were perfluoroalkylated regioselectively at the 2-position.This alkylation was interpreted as a radical aromatic substitution; the formation of the perfluoroalkyl radical can be induced by a single-electron transfer from sulphur dioxide radical anion to the perfluoroalkyl halide.
- Tordeux, Marc,Langlois, Bernard,Wakselman, Claude
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p. 2293 - 2299
(2007/10/02)
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- Process for preparing 3-phenoxy-1-azetidines and carboxamide derivatives
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An improved process is disclosed for preparing 3-phenoxyazetidines which utilizes a phase transfer catalyst to add the phenoxy group to azetidine blocked in the 1-position by a diphenylmethane group and utilizes a stabilizing tertiary amine base to prevent dimerization during hydrogenolysis to remove the blocking group. The crude product containing diphenylmethane may be used without purification to prepare 3-phenoxy-1-azetidinecarboxamides.
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- Vapour-phase chemistry of arenes. Part XII. Reaction of chlorobenzene and derivatives with hydroxyl radicals at approx. 290 deg C. Hydroxy-dechlorination
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Hydroxy-dechlorination, ZC6H4Cl + .OH -> ZC6H4OH + Cl., is advanced as a straightforward process enabling measurement of structural effects on rates of addition of .OH to substituted benzenes.Hydroxyl radicals were generated from tert-butyl hydroperoxide.Under the conditions employed (gas phase, 290 deg C), reaction (9) with chlorobenzene is 0.3 times as fast as H abstraction to give o/m/p-ClC6H4. radicals.Analogous ipso substitution of methyl was not observed; with p-chlorotoluene, .OH forms p-ClC6H4CH2. at least 30 times faster than it gives reaction (9); with o- and p-ClC6H4CF3 (2c), both reaction 9 and displacement of CF3 to give ClC6H40H (reaction 12) occur, the latter ipso substitution being ca. 19 times faster with o- than with p-2c.A thermokinetic rationale is given, for what is apparently a steric effect.Site selectivities for reaction (9), expressed as isomer distribution o/m/p, are: 55/25/20 for Z = Cl and 54/31/15 for Z = Me at 290 deg C.
- Mulder, Peter,Louw, Robert
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p. 220 - 224
(2007/10/02)
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- N-TRIFLUOROMETHYL-N-NITROSOBENZENESULFONAMIDE. A NEW TRIFLUOROMETHYLATING AGENT.
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N-Trifluoromethyl-N-nitrosobenzenesulfonamide was synthesited.It was demonstrated that it acted as a new trifluoromethylating agent.
- Umemoto, Teruo,Miyano, Osamu
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p. 3929 - 3930
(2007/10/02)
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- Trifluoromethylphenyl benzyl ethers
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Trifluoromethylphenols are prepared by hydrogenation of the corresponding trifluoromethylbenzylethers.
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