- Process development and manufacture of potassium 2-fluoro-6-hydroxyphenyltrifluoroborate
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The development of a phase-appropriate manufacturing-scale synthesis of potassium 2-fluoro-6-hydroxyphenyltrifluoroborate was achieved. Investigations into improving the yield and robustness indicated that pH of the reaction medium is a critical process parameter. Additional development resulted in replacing tartaric acid with citric acid, resulting in improved process robustness and enabling scale-up to >10 kg.
- Pawar, Lokesh,Jayaramaiah, Ramesh,Krishnan, Baburaj,Arunachalampillai, Athimoolam,Chen, Ying,Parsons, Andrew T.,Robinson, Jo Anna,Tedrow, Jason S.
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Read Online
- A mild and practical method for deprotection of aryl methyl/benzyl/allyl ethers with HPPh2andtBuOK
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A general method for the demethylation, debenzylation, and deallylation of aryl ethers using HPPh2andtBuOK is reported. The reaction features mild and metal-free reaction conditions, broad substrate scope, good functional group compatibility, and high chemical selectivity towards aryl ethers over aliphatic structures. Notably, this approach is competent to selectively deprotect the allyl or benzyl group, making it a general and practical method in organic synthesis.
- Pan, Wenjing,Li, Chenchen,Zhu, Haoyin,Li, Fangfang,Li, Tao,Zhao, Wanxiang
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p. 7633 - 7640
(2021/09/22)
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- Nickel Hydride Catalyzed Cleavage of Allyl Ethers Induced by Isomerization
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This report discloses the deallylation of O - and N -allyl functional groups by using a combination of a Ni-H precatalyst and excess Bronsted acid. Key steps are the isomerization of the O - or N -allyl group through Ni-catalyzed double-bond migration followed by Bronsted acid induced O/N-C bond hydrolysis. A variety of functional groups are tolerated in this protocol, highlighting its synthetic value.
- Kathe, Prasad M.,Berkefeld, Andreas,Fleischer, Ivana
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supporting information
p. 1629 - 1632
(2021/02/09)
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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 0146-0149
(2021/09/29)
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- Synthesis method of fluorine-containing phenol structure compound
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The invention discloses a synthesis method of a fluorine-containing phenol structure compound, and belongs to the technical field of chemical synthesis. Fluorine-containing benzoic acid is subjected to a one-pot reaction in a solvent under the action of alkali to obtain fluorine-containing phenate, and fluorine-containing phenol is obtained after acid regulation and dissociation. The synthesis method has the advantages of rich, cheap and easily available raw material structure, short synthesis steps, mild reaction conditions, simple and convenient operation, high synthesis yield, good productquality, wide application range and the like, and is suitable for simple and efficient synthesis of various high-value and high-purity fluorine-containing phenol compounds.
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Paragraph 0021-0022
(2021/03/13)
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- Nickel-catalyzed removal of alkene protecting group of phenols, alcohols via chain walking process
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An efficient nickel-catalyzed removal of alkene protection group under mild condition with high functional group tolerance through chain walking process has been established. Not only phenolic ethers, but also alcoholic ethers can be tolerated with the retention of stereocenter adjacent to hydroxyl group. The new reaction brings the homoallyl group into a start of new type of protecting group.
- Meng, Chenkai,Niu, Haolin,Ning, Juehan,Wu, Wengang,Yi, Jun
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- Pyrenediones as versatile photocatalysts for oxygenation reactions with: In situ generation of hydrogen peroxide under visible light
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Pyrenediones (PYDs) are efficient photocatalysts for three oxygenation reactions: Epoxidation of electron deficient olefins, oxidative hydroxylation of organoborons, and oxidation of sulfides via in situ generation of H2O2 under visible light irradiation, using oxygen as a terminal oxidant and IPA as a solvent and a hydrogen donor.
- Zhang, Yuannian,Yang, Xin,Tang, Haidi,Liang, Dong,Wu, Jie,Huang, Dejian
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supporting information
p. 22 - 27
(2020/01/13)
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- Quaternary ammonium hydroxide-functionalized g-C3N4 catalyst for aerobic hydroxylation of arylboronic acids to phenols
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A new and efficient metal-free approach toward the synthesis of phenols via an aerobic hydroxylation of arylboronic acids by using a novel quaternary ammonium hydroxide g-C3N4 catalyst has been described. The functionalized quaternary ammonium hydroxide (g-C3N4-OH) has been prepared from graphitic carbon nitride (g-C3N4) scaffold by converting the residual –NH2 and –NH groups to quaternary methyl ammonium iodide by performing a methylation reaction with methyl iodide followed by ion-exchange with 0.1 N KOH or anion exchange resin Amberlyst A26 (OH- form) by post-synthetic modification. The resultant g-C3N4-OH was characterized by XRD, FTIR, field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), N2 adsorption/desorption isotherms, and acid–base titration. Tested as solid-base catalysts, the g-C3N4-OH showed excellent catalytic activity in the aerobic hydroxylation reaction by converting a variety of arylboronic acids to the corresponding phenols in high yields. More importantly, the g-C3N4-OH solid-base has been successfully reused four times with the minor loss of initial catalytic activity (10.5percent).
- Muhammad, Ibrahim,Mannathan, Subramaniyan,Sasidharan, Manickam
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p. 1470 - 1476
(2020/07/13)
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- Method for preparing alcohol and phenol through aerobic hydroxylation reaction of boric acid derivative in absence of photocatalyst
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The invention discloses a method for preparing alcohol and phenol through aerobic hydroxylation reaction of a boric acid derivative in the absence of a photocatalyst, wherein the boric acid derivativeis aryl boronic acid or alkyl boronic acid, and the corresponding target compounds are respectively a phenol-based compound and an alcohol-based compound. According to the method, by using a boric acid derivative as a reaction substrate, an additive is added under a solvent condition, and a hydroxylation reaction is performed under aerobic and illumination conditions to obtain a corresponding target compound. According to the invention, the new strategy is provided for the synthesis of phenols through aerobic hydroxylation of aryl boronic acid without a photocatalyst; the catalyst-free aerobic hydroxylation method for photocatalysis of aryl boronic acid or alkyl boronic acid by using triethylamine as an additive is firstly disclosed; and the new method has advantages of photocatalyst-freecondition, wide substrate range and good functional group compatibility.
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Paragraph 0025-0028; 0030-0032
(2020/01/25)
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- Method of removing protective groups of olefins under catalytic action of nickel
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The invention relates to a method of removing protective groups of olefins under the catalytic action of nickel. The method comprises following steps: dissolving olefin containing compounds into an organic solvent, carrying out reactions in the presence of a catalyst, organic ligands, bis(pinacolato)diboron, alkalis, alcohols, and water, wherein the catalyst contains nickel; after reactions, adding excess hydrochloric acid solution (1M) to adjust the pH to the acidic region, stirring the solution until the solution becomes clear; adding water and ethyl acetate to carry out extraction; washing the organic phase by saturated brine, drying the organic phase by anhydrous sodium sulfate, carrying out condensation, and adopting a 200-300 mesh silica gel column to carry out chromatographic separation to obtain compounds that contains alcohols or phenol. The provide method has the advantages that the adopted chemical reagents are common, the primary alkyl halide protective groups of olefins can be removed efficiently, and the method has a good application prospect in the field of organic synthesis and good industrial potential.
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Paragraph 0223-0226
(2019/10/04)
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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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- Potassium: Tert -butoxide mediated aerobic hydroxylation of arylboronic acids: An application towards the synthesis of (E)-phenoxy acrylates
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The first example of potassium tert-butoxide mediated aerobic hydroxylation of arylboronic acids is described. A variety of arylboronic acids bearing both electron donating and withdrawing substituents successfully participated in the reaction and furnished phenols in good yields. This strategy also provides access to one pot synthesis of (E)-3-phenoxy acrylates from arylboronic acids and propiolates. The solvent plays an important role and a binary solvent system comprising CH3CN/THF is found to be the best.
- Muhammad, Ibrahim,Balakrishnan, Madasamy Hari,Sasidharan, Manickam,Mannathan, Subramaniyan
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supporting information
p. 11065 - 11068
(2019/07/31)
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- Photoinduced hydroxylation of arylboronic acids with molecular oxygen under photocatalyst-free conditions
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Photoinduced hydroxylation of boronic acids with molecular oxygen under photocatalyst-free conditions is reported, providing a green entry to a variety of phenols and aliphatic alcohols in a highly concise fashion. This new protocol features photocatalyst-free conditions, wide substrate scope and excellent functional group compatibility.
- Xu, Yu-Ting,Li, Chen-Yuan,Huang, Xiao-Bo,Gao, Wen-Xia,Zhou, Yun-Bing,Liu, Miao-Chang,Wu, Hua-Yue
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supporting information
p. 4971 - 4975
(2019/09/30)
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- Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom
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The sustainable, selective direct hydroxylation of arenes, such as benzene to phenol, is an important research challenge. An electrocatalytic transformation using formic acid to oxidize benzene and its halogenated derivatives to selectively yield aryl formates, which are easily hydrolyzed by water to yield the corresponding phenols, is presented. The formylation reaction occurs on a Pt anode in the presence of [CoIIIW12O40]5? as a catalyst and lithium formate as an electrolyte via formation of a formyloxyl radical as the reactive species, which was trapped by a BMPO spin trap and identified by EPR. Hydrogen was formed at the Pt cathode. The sum transformation is ArH+H2O→ArOH+H2. Non-optimized reaction conditions showed a Faradaic efficiency of 75 % and selective formation of the mono-oxidized product in a 35 % yield. Decomposition of formic acid into CO2 and H2 is a side-reaction.
- Khenkin, Alexander M.,Somekh, Miriam,Carmieli, Raanan,Neumann, Ronny
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supporting information
p. 5403 - 5407
(2018/04/19)
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- Boron compound conjugated π, electronic device, and triazoles [...] number bath preparation method
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There are provided a π-conjugated boron compound, an electronic device containing an organic functional layer including the π-conjugated boron compound, a method for producing a triarylborane, and a method for producing a triarylborane intermediate. In the π-conjugated boron compound, a boron atom is bonded to three aromatic groups via three boron-carbon bonds. Bond distances of the three boron-carbon bonds are all 1.48 ? or less.
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Paragraph 0226; 0230
(2019/01/06)
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- Synergistic Photo-Copper-Catalyzed Hydroxylation of (Hetero)aryl Halides with Molecular Oxygen
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Photoredox-mediated copper-catalyzed hydroxylation of (hetero)aryl halides (including chlorides, bromides, and iodides) with O2 at room temperature has been developed. Preliminary mechanistic studies indicate no arylcopper intermediate and that aryl radicals are involved in this procedure. 18O-labeling experiments confirm the hydroxyl oxygen atom originated from molecular oxygen.
- Zhang, Xin,Wu, Ge,Gao, Wenxia,Ding, Jinchang,Huang, Xiaobo,Liu, Miaochang,Wu, Huayue
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supporting information
p. 708 - 711
(2018/02/09)
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- Green Photoorganocatalytic Synthesis of Phenols from Arylboronic Acids
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A green and cheap protocol for the photocatalytic hydroxylation of arylboronic acids is presented. 2,2-Dimethoxy-2-phenylacetophenone proved to be the best photoinitiator, among a range of organocatalysts in promoting this reaction. This photocatalytic protocol can be expanded into a wide substrate scope of aromatic boronic acids bearing various functional groups, leading to the corresponding phenols in good to high yields under mild reaction conditions, which include water as solvent, light irradiation provided from standard light-bulbs at room temperature.
- Sideri, Ioanna K.,Voutyritsa, Errika,Kokotos, Christoforos G.
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supporting information
p. 1324 - 1328
(2017/12/06)
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- Reagent Design and Ligand Evolution for the Development of a Mild Copper-Catalyzed Hydroxylation Reaction
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Parallel synthesis and mass-directed purification of a modular ligand library, high-throughput experimentation, and rational ligand evolution have led to a novel copper catalyst for the synthesis of phenols with a traceless hydroxide surrogate. The mild reaction conditions reported here enable the late-stage synthesis of numerous complex, druglike phenols.
- Fier, Patrick S.,Maloney, Kevin M.
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supporting information
p. 3033 - 3036
(2017/06/07)
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- Method for continuous flow synthesis of phenol-based compound
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The present invention provides a method for continuous flow synthesis of a phenol-based compound represented by a formula (III), wherein the method is performed in two static mixers, a tubular reactor and an oil-water separator, wherein the two static mixers, the tubular reactor and the oil-water separator are sequentially connected in series. The method comprises that an acid solution and an aniline compound represented by a formula (I) are pumped into the static mixer A; the mixture of the acid solution and the compound represented by the formula (I) flows out from the static mixer A and flows into the static mixer B connected to the static mixer A; a sodium nitrite solution is pumped into the static mixer B, and a reaction is performed to produce a diazonium salt solution represented by a formula (II); and the solution represented by the formula (II) flows out from the static mixer B, is pumped into the tubular reactor connected to the static mixer B, and then into the oil-water separator connected to the tubular reactor, and the water phase is separated to obtain the compound represented by the formula (III). According to the present invention, the method has characteristics of short reaction time, solvent saving and high yield, and can well solve the problems in the synthesis of the phenol-based compound through diazotization hydrolysis in the intermittent kettle type reactor. The formulas (I), (II) and (III) are defined in the specification.
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Paragraph 0049; 0050
(2017/07/21)
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- 4-amino-3-fluorophenol and synthesizing method thereof
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The invention discloses 4-amino-3-fluorophenol and a synthesizing method thereof.The synthesizing method comprises the steps that fluoroaniline serves as a raw material, a diazo-reaction is carried out first, then a fluorine resolving reaction is carried out, and a white diazonium salt solid is obtained; then, the white diazonium salt solid is subjected to a hydrolysis reaction, and 3-fluorophenol is obtained; 3-fluorophenol is then subjected to a nitration reaction, and 3-fluorine-4-nitrophenol is obtained; then, obtained 3-fluorine-4-nitrophenol is reduced, and 4-amino-3-fluorophenol is obtained.According to 4-amino-3-fluorophenol and the synthesizing method thereof, ionic liquid serves as a reaction solvent, the volatility is low, environment is easily protected, and no harm is caused to the human body; in the reaction of reducing nitro groups into amino groups, the microwave heating mode is adopted, so that the reaction efficiency is greatly improved, and the product yield is increased.
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Paragraph 0020; 0022
(2016/10/10)
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- A Mild Strategy for the Preparation of Phenols via the Ligand-Free Copper-Catalyzed O-Arylation of para -Toluenesulfonic Acid
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A facile and simple ligand-free copper-catalyzed reaction to synthesize substituted phenols is reported. The reaction presumably proceeds via an O-arylsulfonate intermediate that is hydrolyzed to afford good to excellent yields of up to 88%. This protocol provides an alternative to existing reports which use strong hydroxide salts as the direct hydroxylation partner. Demonstrating a wide substrate scope and functional group tolerance, this protocol can also be applied to inexpensive and commercially available carboxylic acids to yield phenols.
- Tan, Bryan Yong-Hao,Teo, Yong-Chua
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supporting information
p. 1814 - 1819
(2016/07/16)
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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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- PROCESS FOR MANUFACTURING FLUOROAROMATICS
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The present invention relates to a process for manufacturing fluoroaromatics of formula (I), A-F, comprising step a) diazotization of aminoaromaticsof formula (II) in anhydrous HF with an aqueous solution of a diazotizing agent; followed by step b) thermic decomposition of the diazonium salt of formula (III) resulting from step a); wherein the variables are defined according to the description.
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Page/Page column 14
(2014/02/15)
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- Reductive cleavage of aryl O-carbamates to phenols by the Schwartz reagent. Expedient link to the directed ortho metalation strategy?
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A general, mild, and efficient method for the reductive cleavage of aryl O-carbamates to phenols, 1 → 2 using the Schwartz reagent is reported. The method is selective, tolerating a large number of functional groups; may be carried out by direct or by an economical in situ procedure; and, notably, establishes a synthetic connection to the directed ortho metalation strategy (Figure 1) allowing new entries into difficult to prepare contiguously substituted aromatics and heteroaromatics.
- Morin, Justin,Zhao, Yigang,Snieckus, Victor
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supporting information
p. 4102 - 4105
(2013/09/12)
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- Catalysis by Amberlite IR-120 resin: A rapid and green method for the synthesis of phenols from arylboronic acids under metal, ligand, and base-free conditions
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A clean process has been developed for the ipso-hydroxylation of aryl and heteroaryl boronic acids to the corresponding phenols using commercially available and recyclable Amberlite IR-120 resin and aqueous hydrogen peroxide as an oxidizing agent. The ion-exchange sulfonic acid resin catalyst could be readily recycled by filtration and directly reused at least four times without any significant loss of activity.
- Mulakayala, Naveen,Ismail,Kumar, Kottur Mohan,Rapolu, Rajesh Kumar,Kandagatla, Bhaskar,Rao, Pallavi,Oruganti, Srinivas,Pal, Manojit
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supporting information
p. 6004 - 6007,4
(2020/07/31)
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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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- CuII-β-cyclodextrin complex as a nanocatalyst for the homo-and cross-coupling of arylboronic acids under ligand-and base-free conditions in air: Chemoselective cross-coupling of arylboronic acids in water
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We report here the transition-metal-catalyzed chemoselective cross-coupling of arylbroronic acids in high yields without using ligand or base. We have developed an efficient copper-catalyzed protocol for the homocoupling and cross-coupling of arylboronic acids. The protocol is also suitable for the cross-coupling of aliphatic primary amines with arylboronic acids. Aminophenols and primary amines bearing an alcoholic substituent on the aliphatic chain were coupled with arylboronic acids, and the products were obtained with high C-N coupling selectivity. An effective catalyst was Cu2-β- cyclodextrin, which is readily available and structurally simple, but has not previously been explored as a catalyst.
- Kaboudin, Babak,Abedi, Yaghoub,Yokomatsu, Tsutomu
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experimental part
p. 6656 - 6662
(2012/01/06)
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- Aromatic Hydroxylation at a Non-Heme Iron Center: Observed Intermediates and Insights into the Nature of the Active Species
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Mechanism of substrate oxidations with hydrogen peroxide in the presence of a highly reactive, biomimetic, iron aminopyridine complex, [Fe II(bpmen)(CH3CN)2][ClO4] 2 (1; bpmen=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2- diamine), is elucidated. Complex 1 has been shown to be an excellent catalyst for epoxidation and functional-group-directed aromatic hydroxylation using H2O2, although its mechanism of action remains largely unknown.1, 2 Efficient intermolecular hydroxylation of unfunctionalized benzene and substituted benzenes with H2O2 in the presence of 1 is found in the present work. Detailed mechanistic studies of the formation of iron(III)-phenolate products are reported. We have identified, generated in high yield, and experimentally characterized the key FeIII(OOH) intermediate (Imax=560 nm, rhombic EPR signal with g=2.21, 2.14, 1.96) formed by 1 and H2O2. Stopped-flow kinetic studies showed that FeIII(OOH) does not directly hydroxylate the aromatic rings, but undergoes rate-limiting self-decomposition producing transient reactive oxidant. The formation of the reactive species is facilitated by acid-assisted cleavage of the O-O bond in the iron-hydroperoxide intermediate. Acid-assisted benzene hydroxylation with 1 and a mechanistic probe, 2-Methyl-1-phenyl-2-propyl hydroperoxide (MPPH), correlates with O-O bond heterolysis. Independently generated FeIV=O species, which may originate from O-O bond homolysis in FeIII(OOH), proved to be inactive toward aromatic substrates. The reactive oxidant derived from 1 exchanges its oxygen atom with water and electrophilically attacks the aromatic ring (giving rise to an inverse H/D kinetic isotope effect of 0.8). These results have revealed a detailed experimental mechanistic picture of the oxidation reactions catalyzed by 1, based on direct characterization of the intermediates and products, and kinetic analysis of the individual reaction steps. Our detailed understanding of the mechanism of this reaction revealed both similarities and differences between synthetic and enzymatic aromatic hydroxylation reactions.
- Makhlynets, Olga V.,Rybak-Akimova, Elena V.
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supporting information; scheme or table
p. 13995 - 14006
(2011/04/12)
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- Arylsilane oxidation - New routes to hydroxylated aromatics
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An efficient route to hydroxylated aromatics has been developed, via the oxidation of aryl organosilanes under functional group-tolerant and relatively mild conditions, using sub-stoichiometric amounts of fluoride promoters.
- Bracegirdle, Sonia,Anderson, Edward A.
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supporting information; experimental part
p. 3454 - 3456
(2010/07/16)
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- Highly efficient synthesis of phenols by copper-catalyzed oxidative hydroxylation of arylboronic acids at room temperature in water
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Figure presented A general and efficient procedure for the preparation of phenols was developed by copper-catalyzed oxidative hydroxylation of arylboronic acids at room temperature in water.
- Xu, Jimin,Wang, Xinyan,Shao, Changwei,Su, Deyong,Cheng, Guolin,Hu, Yuefei
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supporting information; experimental part
p. 1964 - 1967
(2010/07/04)
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- Photocatalytic hydroxylation of aromatic ring by using water as an oxidant
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Electrophilic oxygen species photocatalytically derived from water molecules can selectively react with the aromatic ring of both benzene and its derivatives to produce the corresponding phenols and hydrogen over platinum-loaded titanium oxide when illuminated with light of appropriate wavelength in the absence of oxygen. The Royal Society of Chemistry.
- Yoshida, Hisao,Yuzawa, Hayato,Aoki, Masanori,Otake, Kazuko,Itoh, Hideaki,Hattori, Tadashi
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scheme or table
p. 4634 - 4636
(2009/03/11)
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- A mild conversion of arylboronic acids and their pinacolyl boronate esters into phenols using hydroxylamine
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Hydroxylamine was found to be a mild reagent for conversion of arylboronic acids and their pinacolyl boronate esters into phenols. This procedure works on most arylboronic acids at room temperature, yielding phenols in moderate to good yields, and efficiently on arylboronates also yielding phenols in good yields.
- Kianmehr, Ebrahim,Yahyaee, Maryam,Tabatabai, Katayoun
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p. 2713 - 2715
(2008/02/03)
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- Enzymatic Baeyer-Villiger oxidation of benzaldehydes
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The selectivity of the chemical Baeyer-Villiger oxidation of benzaldehydes depends on steric and electronic factors, the type of oxidizing agent and the reaction conditions. Here we report on the enzymatic Baeyer-Villiger oxidation of fluorobenzaldehydes
- Moonen, Marielle J. H.,Westphal, Adrie H.,Rietjens, Ivonne M. C. M.,Van Berkel, Willem J. H.
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p. 1027 - 1034
(2007/10/03)
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- A product analytical study of the thermal and photolytic decomposition of some arenediazonium salts in solution
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Products of thermal and photochemical reactions of eleven arenediazonium tetrafluoroborates in various solvents have been analyzed. All compounds in most solvents undergo unimolecular heterolysis to give singlet aryl cations which are captured by solvent. This mechanism is dominant for arenediazonium ions without electron-withdrawing substituents in all solvents, and the only reaction observed in water. Additionally, appreciable yields of fluoroarenes are obtained by fluoride abstraction by the aryl cation from fluorinated solvents and from tetrafluoroborate in fluorinated solvents. Yields from photochemical processes are very similar to those from thermal reactions indicating that the main reactions proceed through common or very similar intermediates. Aryl cations formed from ion-paired diazonium ions may react with the counterion, but fragmentation of dissociated diazonium ions leads only to solvent-derived product. Some arenediazonium ions in some solvents undergo an alternative radical reaction leading principally to hydrodediazoniation. It is proposed that this reaction involves initial rate-limiting electron transfer from ethanol to the arenediazonium ion followed rapidly by homolysis of the resultant aryldiazenyl radical. Within the same solvent cage, the aryl radical then either abstracts an α-hydrogen from the ethanol radical cation generated in the first step to give the reduction product and protonated acetaldehyde, or combines with it at the oxygen to give a protonated aryl ethyl ether.
- Canning, Peter S. J.,Maskill, Howard,McCrudden, Katharine,Sexton, Brian
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p. 789 - 800
(2007/10/03)
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- Photochemistry of aryl tert-butyl ethers in methanol: The effect of substituents on an excited state cleavage reaction
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The photolysis of a set of 10 substituted aryl tert-butyl ethers, 8a-j, in methanol gave, as the major product, the corresponding phenol along with tert-butyl-substituted phenols resulting from photo-Fries reaction. The corresponding 4-cyanophenyl 1-adamantyl ether, 9, also gave 1-meth-oxyadamantane 16 (16%), indicating that, at least for this ether, some of the products were ion-derived. Quenching studies with 2,3-dimethylbutadiene for the tert-butyl ethers indicated that these reactions were occurring from the singlet excited state. Rate constants for the reaction, obtained from quantum yields and singlet lifetimes, were found to correlate reasonably well with σhv values, ρ = -0.77 (r = 0.975), a result that is unexpected for a reaction where the polarity of the bond breaking in the transition state is expected to be -O(δ-)···C(δ+).
- DeCosta,Bennett,Pincock,Pincock,Stefanova
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p. 4162 - 4168
(2007/10/03)
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- Sulphonamide derivatives
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The present invention relates to the potentiation of glutamate receptor function using certain sulphonamide derivatives. It also relates to novel sulphonamide derivatives, to processes for their preparation and to pharmaceutical compositions containing them.
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- Arene complexes of transition metals in reactions with nucleophilic reagents. XXIX. Poly[(p-cyclopentadienylmethylstyrene)rhodium]2+ as catalyst of alkoxydefluorination of fluoroarenes
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The poly[(p-cyclopentadienylmethylstyrene)rhodium]2+ produced in situ by treating the respective dichloride complex with silver triflate in the presence of primary alcohols (methanol, propanol, hexanol) was used as catalyst grafted on polymeric sublayer for alkoxydefluorination of fluoroarenes. The activity of the catalyst in alcoholysis of fluorobenzene and p-fluorotolyene is similar to that of the corresponding homogeneous catalysts. The catalyst conserves its activity for repeated application.
- Goryunov,Steingarts
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p. 246 - 251
(2007/10/03)
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- Facile preparation of aromatic fluorides by deaminative fluorination of aminoarenes using hydrogen fluoride combined with bases
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One-pot deaminative fluorination of aminoarenes including heteroaromatics, namely, diazotization of aminoarenes followed by in situ fluoro-dediazoniation of the corresponding diazonium ions, was successfully accomplished to produce fluoroarenes in high yields by using hydrogen fluoride combined with base solutions. The diazotization stage has been found to play the most important part in yielding fluoroarenes effectively. It was greatly influenced by the composition of the HF solution and enhanced by employing appropriate amounts of bases such as pyridine under carefully controlled conditions. The fluoro-dediazoniation stage was effectively accelerated photochemically to afford fluoroarenes having polar substituents such as hydroxyl, nitro and so on in high yields.
- Yoneda,Fukuhara
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- Regiospecific hydroxylation in aromatic series by the organosilicon pathway
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Regiospecific hydroxylation of functional arylsilanes by hydrogen peroxide (30percent) or by bis(trimethylsilyl) peroxide, in the presence of a stoichiometric amount of fluoride ions, gives the corresponding phenols in good yields. regiospecific hydroxylation / phenol / hydrogen peroxide / bis(trimethylsilyl) peroxide / arylsilane
- Prouilhac-Cros, Sylvie,Babin, Pierre,Bennetau, Bernard,Dunogues, Jacques
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p. 513 - 516
(2007/10/02)
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- Hydrolysis of orthocarbonates. Evidence for charge imbalance in the transition state for the general acid catalyzed process
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Catalytic constants have been measured for the hydrolysis of a range of aryl orthocarbonates, in which both the leaving group and trioxocarbenium ion moiety have been systematically varied, by neutral carboxylic acids (trichloroacetic, difluoroacetic, dichloroacetic, malonic, chloroacetic, and acetic) at 70.0°C in 60% water-40% acetonitrile, I = 1.0 M (KCI). Curvature cannot be detected in Br?nsted plots involving carboxylic acids only, but inclusion of the point for H3O+ suggests downward curvature (i.e. px ≥ 0). β1g Plots are curved downward (i.e. py′ = -?β1g/?pK1g > 0). Substitutent effects in the tris(aryloxy)carbenium ion fragment were quantitated by use of the experimental aqueous pKa alues of the phenol (pKrc), rather than Hammett σ values, since this gave better correlations for the spontaneous reactions (Kandanarachchi, P.; Sinnott, M. L. J. Am. Chem. Soc., preceding paper in this issue). Cross coefficients are large and not constant: pxy′ (measured as ?α/?pK1g rather than -?β1g/?pKHA) varies from 0.26 for (PhO)3C+ to 0.16 for (PMeOC6H4O)3C+. Likewise,pxy (measured as -?α/?pKrc rather than -?βrc/?pKHA) experiences large changes with the leaving group pK. Data to estimate pyy′ (?βrc/?pK1g) are more limited, but it too changes with the pKa of the catalyzing acid. These data indicate that a two-dimensional More O'Ferrall-Jencks diagram, with one axis representing both C-O cleavage and the ability of substituents in the tris(aryloxy)carbenium ion moiety to sense positive charge development, is inadequate to represent this reaction: separate axes are required for carbon-oxygen bond cleavage and development of carbon-oxygen double-bond character.
- Kandanarachchi, Pramod,Sinnott, Michael L.
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p. 5601 - 5606
(2007/10/02)
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- Mechanism of Arene Hydroxylation by Vanadium Picolinato Peroxo Complexes
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The mechanism of the reaction of VO(O2)PIC(H2O)2 (PIC = picolinic acid anion) with benzene and substituted benzenes in CH3CN, affording the corresponding phenols together with dioxygen, has been further investigated.The reaction is a radical chain process whose initiation produces the actual oxidant which may be described as a radical anion derived from the peroxovanadium complex, possessing, however, a marked electrophilic character.In the propagation steps such species react either with the original peroxo complex yielding dioxygen or with the aromatic substrates affording phenols via the formation of an intermediate.
- Bonchio, Marcella,Conte, Valeria,Di Furia, Fulvio,Modena, Giorgio,Moro, Stefano
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p. 6262 - 6267
(2007/10/02)
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- Facile Preparation of Aromatic Fluorides by the Fluoro-Dediazoniation of Aromatic Diazonium Tetrafluoroborates Using HF-Pyridine Solution
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The fluoro-dediazoniation of ArN2BF4 using HF-pyridine solution has been successfully carried out either thermaly or photochemically to afford the corresponding ArF in good yields.Particularly, the photochemically induced reaction in HF-pyridine was a useful tool for the preparation of ArF having polar substituents such as halogens, OH, OMe, CF3, etc.
- Fukuhara, Tsuyoshi,Sekiguchi, Manabu,Yoneda, Norihiko
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p. 1011 - 1012
(2007/10/02)
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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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- Acid-catalyzed amino-migration of O-phenylhydroxylamines
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The mechanism of amino-migration of O-phenylhydroxylamine (1a) was studied. It was found that 1 rearranges to give 2-aminophenol (50%) and 4-aminophenol (7%) in trifluoroacetic acid (TFA). The predominance of the ortho rearrangement of 1 clearly distinguishes this process from the Bamberger rearrangement. From cross-coupling experiments employing stable isotopes, it was clarified that the ortho rearrangement proceeds intramolecularly and the para rearrangement involves both intra- and intermolecular processes. Good first-order kinetics were obtained for the rearrangement. The Hammett plot (σ+) with a large negative slope (ρ = -7.8) indicates that initial heterolytic N-O bond cleavage of 1 occurs and generates a positive charge on the oxygen atom with considerable delocalization into the aromatic ring. An ion-molecule pair involving a phenoxenium ion and an ammonia molecule as an intermediate rationalizes all of the results. In this pair, intramolecular combination to the ortho position proceeds preferentially over that to the para position. Formation of catechol and hydroquinone can be explained in terms of nucleophilic attack of TFA on the phenoxenium ion in a solvent-separated pair.
- Haga, Naoki,Endo, Yasuyuki,Kataoka, Ken-Ichiro,Yamaguchi, Kentaro,Shudo, Koichi
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p. 9795 - 9806
(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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- AROMATIC FLUORINE CHEMISTRY. PART 3. PREPARATION OF FLUOROPHENOLS VIA HYDROLYSIS OF CHLOROFLUOROBENZENES
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The 1,2-, 1,3-, and 1,4-fluorophenols have been prepared by a copper (e.g.CuO, CuSO4) catalyzed hydrolysis of chlorofluorobenzenes under conditions of controlled pH.
- Pews, R. G.,Gall, J. A.
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p. 377 - 380
(2007/10/02)
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- Preparation of fluorophenols
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2- and 3-fluorophenols are prepared by dehydrating 1,2-dihydroxy-3-fluorocyclohexa-3,5-diene under basic conditions and recovering the desired product, for example by fractional distillation.
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- Does the Reaction of Cu+ with H2O2 Give OH Radicals? A Study of Aromatic Hydroxylation
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The reaction of Cu+ with H2O2 was studied by using the isomer distribution obtained with fluorobenzene, anisole, and nitrobenzene as a probe for OH radicals.The reaction with benzene in presence of 5*10-2 M Cu2+ gave a maximum yield of 69percent phenol.The isomer distributions obtained with fluorobenzene, anisole, and nitrobenzene are almost identical with those obtained in the radiation-induced hydroxylation under similar conditions.In experiments with benzene and nitrobenzene we have shown that Cu3+ produced via Cu2+ + OH does not hydroxylate these aromatic compounds in neutral or weakly acidic solutions (pH 5.0 - 6.0).We therefore conclude that in the reaction of Cu+ with H2O2 the OH radical is the major reactive species that reacts with aromatic compounds.
- Eberhardt, Manfred K.,Ramirez, Glenda,Ayala, Erick
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p. 5922 - 5926
(2007/10/02)
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- 16-Substituted polyunsaturated hexadecanoic fatty acids
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Sixteen carbon atom carboxylic acids having 16-phenoxy or 16-phenylthio substituents, and 0, 1, or 4 triple bonds, methods of preparing them, and pharmaceutical preparations containing them. These compounds are useful as lipoxygenase inhibitors.
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- Fluorine-substituted phenyl benzoates and process for producing same
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A fluorine-substituted phenyl benzoate of the general formula wherein one of either Ar or Ar' is p- or o-fluorophenyl group, while the other is m-fluorophenyl group. This fluorine-substituted phenyl benzoate can be prepared by subjecting to an oxidative decarboxylation reaction a fluorobenzoic acid of the general formula wherein Ar" is a fluorophenyl group. This phenyl benzoate is valuable as in intermediate for producing the fluorophenols.
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