- 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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- Decarboxylative Hydroxylation of Benzoic Acids
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Herein, we report the first decarboxylative hydroxylation to synthesize phenols from benzoic acids at 35 °C via photoinduced ligand-to-metal charge transfer (LMCT)-enabled radical decarboxylative carbometalation. The aromatic decarboxylative hydroxylation is synthetically promising due to its mild conditions, broad substrate scope, and late-stage applications.
- Ritter, Tobias,Su, Wanqi,Xu, Peng
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p. 24012 - 24017
(2021/10/06)
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- Method for preparing O-fluorophenol by one-pot method
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The invention discloses a method for preparing o-fluorophenol by a one-pot method, and belongs to the technical field of organic synthesis. O-bromine/chlorofluorobenzene is used as a raw material, a 2-fluorophenyl Grignard reagent is obtained through magnesium metal or Grignard reagent exchange in the presence of a stabilizer, and then oxygen or compressed air is introduced to obtain the o-fluorophenol. The method is simple and convenient in reaction operation, less in three wastes, high in yield and free of isomers, inhibits elimination of a Grignard reagent due to addition of the stabilizer, and accords with industrial amplification prospects.
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Paragraph 0023-0025
(2021/04/14)
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- Photo-induced thiolate catalytic activation of inert Caryl-hetero bonds for radical borylation
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Substantial effort is currently being devoted to obtaining photoredox catalysts with high redox power. Yet, it remains challenging to apply the currently established methods to the activation of bonds with high bond dissociation energy and to substrates with high reduction potentials. Herein, we introduce a novel photocatalytic strategy for the activation of inert substituted arenes for aryl borylation by using thiolate as a catalyst. This catalytic system exhibits strong reducing ability and engages non-activated Caryl–F, Caryl–X, Caryl–O, Caryl–N, and Caryl–S bonds in productive radical borylation reactions, thus expanding the available aryl radical precursor scope. Despite its high reducing power, the method has a broad substrate scope and good functional-group tolerance. Spectroscopic investigations and control experiments suggest the formation of a charge-transfer complex as the key step to activate the substrates.
- K?nig, Burkhard,Wang, Hua,Wang, Shun
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supporting information
p. 1653 - 1665
(2021/06/17)
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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 0025-0026
(2021/03/13)
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- Preparation method of 2-fluorophenol
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The invention relates to the field of fluorine-containing compounds, and particularly discloses a preparation method of 2-fluorophenol. The invention relates to a preparation method of 2-fluorophenol.The preparation method comprises the following steps: (1) diazotization reaction: adding 2-fluoroaniline into a dilute acid solution under stirring, cooling after the reaction is finished, dropwise adding a sodium nitrite water solution, stirring, and keeping the temperature to obtain a diazonium salt solution; (2) quenching: adding urea into the diazonium salt solution, and stirring to obtain anintermediate solution; (3) hydrolysis reaction: firstly, mixing a copper salt aqueous solution with an organic solvent to obtain a mixed solution, dropwise adding the intermediate solution into the preheated mixed solution, and obtaining a hydrolysate after dropwise adding is finished; wherein the organic solvent is immiscible with water; and (4) post-treatment: carrying out post-treatment on thehydrolysate to obtain 2-fluorophenol. The preparation method has the advantages that the yield and purity of 2-fluorophenol are high, the use amount of a copper catalyst is reduced, and hydrolysis side reactions are reduced.
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Paragraph 0003; 0030-0058
(2021/01/25)
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- Phenol compound ortho-position direct fluorination method
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The invention relates to a phenol compound ortho-position direct fluorination method which comprises the following steps: reacting a phenol compound shown in a formula (1A) with a fluorination reagentin a solvent under the action of a photocatalyst and a light source at room temperature, and separating and purifying a reaction mixture after the reaction to obtain a fluorinated phenol compound shown in a formula (2A). The advantages are as follows: the method for directly fluorinating phenol by organic photocatalysis is simple in operation process; raw materials are commercialized and easy toobtain; the photocatalyst is low in price, easy to obtain and environmentally friendly; the reaction condition is mild; the site selectivity is high; the reaction is efficient; and a fluorinated phenol derivative can be prepared only through one step.
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Paragraph 0043-0045
(2020/04/17)
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- The highly efficient air oxidation of aryl and alkyl boronic acids by a microwave-assisted protocol under transition metal-free conditions
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Molecular oxygen is the most important green-oxidant due to its excellent properties. However, the effective utilization of molecular oxygen remains a major challenge in modern chemistry. Herein, we report the development a rapid, green and efficient microwave-assisted protocol for the air oxidation of boronic acids to phenols and alcohols under transition metal-free conditions. In the presence of KOH and DMSO, high yields of the expected phenols and alcohol were obtained with microwave-assistance, and a variety of functional groups were tolerated in this procedure. Notably, this transition metal-free method represents a breakthrough in both organic synthesis and green chemistry for the oxidative hydroxylation of boronic acids to phenols and alcohols.
- Yin, Weiyan,Pan, Xizhi,Leng, Wenxi,Chen, Jian,He, Haifeng
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supporting information
p. 4614 - 4618
(2019/09/09)
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- Phthalocyanine Zinc-catalyzed Hydroxylation of Aryl Boronic Acids under Visible Light
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A visible-light-promoted aerobic oxidative hydroxylation of boronic acids using phthalocyanine zinc as an easily available photosensitizer has been developed. It provided a direct access to synthesize aliphatic alcohols and phenols from boronic acids. The advantages of this approach included the low catalyst loading (0.5 mol%), high efficient, the use of O2 as an oxygen source, wide substrate range, the simple operational process, and mild conditions. (Figure presented.).
- Luo, Dong-Ping,Huang, Yang-Feng,Hong, Xiao-Yi,Chen, Dingben,Li, Guo-Xing,Huang, Xiao-Bo,Gao, Wen-Xia,Liu, Miao-Chang,Zhou, Yun-Bing,Wu, Hua-Yue
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supporting information
p. 961 - 964
(2019/01/25)
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- Room-Temperature Ionic Liquids (RTILs) as Green Media for Metal- and Base-Free ipso -Hydroxylation of Arylboronic Acids
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The oxidative hydroxylation of arylboronic acids to the corresponding phenolic compounds under metal- and base-free aerobic conditions is successfully demonstrated on a greener media. Hydrogen peroxide, as an eco-friendly oxidant, is compatible with green mediates room-temperature ionic liquids (RTIL)s, providing hydroxylation products of arylboronic acids in an efficient manner. The RTIL support is particularly interesting for its reusability.
- Kim, Seung-Hoi,Kwon, Gyu-Tae,Shin, Eun-Jae
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supporting information
p. 1815 - 1819
(2019/09/09)
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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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- Whole-Cell Biotransformation of Benzene to Phenol Catalysed by Intracellular Cytochrome P450BM3 Activated by External Additives
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An Escherichia coli whole-cell biocatalyst for the direct hydroxylation of benzene to phenol has been developed. By adding amino acid derivatives as decoy molecules to the culture medium, wild-type cytochrome P450BM3 (P450BM3) expressed in E.coli can be activated and non-native substrates hydroxylated, without supplementing with NADPH. The yield of phenol reached 59 % when N-heptyl-l-prolyl-l-phenylalanine (C7-Pro-Phe) was employed as the decoy molecule. It was shown that decoy molecules, especially those lacking fluorination, reached the cytosol of E. coli, thus imparting in vivo catalytic activity for the oxyfunctionalisation of non-native substrates to intracellular P450BM3.
- Karasawa, Masayuki,Stanfield, Joshua Kyle,Yanagisawa, Sota,Shoji, Osami,Watanabe, Yoshihito
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supporting information
p. 12264 - 12269
(2018/07/31)
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- Nitrogen Oxides and Nitric Acid Enable the Sustainable Hydroxylation and Nitrohydroxylation of Benzenes under Visible Light Irradiation
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A new type of waste recycling strategy is described in which nitrogen oxides or nitric acid are directly employed in photocatalyzed hydroxylations and nitrohydroxylations of benzenes. Through these transformations, otherwise costly denitrification can be combined with the synthesis of valuable compounds for various applications.
- Hofmann, Laura Elena,Mach, Leonard,Heinrich, Markus R.
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supporting information
p. 431 - 436
(2017/12/15)
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- Promotional effect of ionic liquids in the electrophilic fluorination of phenols
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The influence of a stoichiometric amount of ionic liquids (IL) on the fluorination of phenols in various solvents has been studied. The fluorination of phenol, 1-naphthol and resorcinol was carried out using 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (F-TEDA-BF4, Selectfluor) with the formation of 2-fluoro-, 4-fluorophenol, 2-fluoro-, 4-fluoronaphthol and 4-fluoro-, 4,6-difluoro-benzene-1,3-diol as the main products. The use of a stoichiometric amount of ionic liquid as an additive results in acceleration of the reactions. The effect is most significant at low temperatures. It has been found that solvent polarity has an essential effect on the difference in yields of fluoroproducts obtained in the presence of IL and without it.
- Borodkin, Gennady I.,Elanov, Innokenty R.,Shubin, Vyacheslav G.
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- Ir-Catalyzed ortho-Borylation of Phenols Directed by Substrate-Ligand Electrostatic Interactions: A Combined Experimental/in Silico Strategy for Optimizing Weak Interactions
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A strategy for affecting ortho versus meta/para selectivity in Ir-catalyzed C-H borylations (CHBs) of phenols is described. From selectivity observations with ArylOBpin (pin = pinacolate), it is hypothesized that an electrostatic interaction between the partial negatively charged OBpin group and the partial positively charged bipyridine ligand of the catalyst favors ortho selectivity. Experimental and computational studies designed to test this hypothesis support it. From further computational work a second generation, in silico designed catalyst emerged, where replacing Bpin with Beg (eg = ethylene glycolate) was predicted to significantly improve ortho selectivity. Experimentally, reactions employing B2eg2 gave ortho selectivities > 99%. Adding triethylamine significantly improved conversions. This ligand-substrate electrostatic interaction provides a unique control element for selective C-H functionalization.
- Chattopadhyay, Buddhadeb,Dannatt, Jonathan E.,Andujar-De Sanctis, Ivonne L.,Gore, Kristin A.,Maleczka, Robert E.,Singleton, Daniel A.,Smith, Milton R.
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supporting information
p. 7864 - 7871
(2017/06/20)
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- Process for preparing phenol fluoride by amine catalytic method
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The invention relates to a process for preparing phenol fluoride by amine catalytic method and belongs to the technical field of chemical synthesis.The process comprises: adding phenol and a catalyst sequentially into a reactor for heating, introducing fluorine-nitrogen mixed gas into the reactor for reacting, purging with nitrogen after reacting to obtain crude phenol fluoride, charging purging gas and reaction tail gas sequentially into an activated carbon absorber and a solid sodium lime absorber for adsorption, discharging finally obtained non-condensable gas at a great height, rectifying and separating the crude phenol fluoride to obtain o-fluorophenol, p-fluorophenol, 2,4-difluorophenol and 2,6-difluorophenol.The problem that an existing preparation process has low product yield, high solvent consumption, high cost and environmental pollution is solved herein, the process has the advantages of material conversion completeness, little byproduct and low production cost, no additional solvent is added to maintain a certain temperature range, cost is saved, and solvent loss is reduced.
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Paragraph 0028-0038
(2017/04/03)
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- Synthesis of 2 - fluoro phenol compounds
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The present invention provides a method for synthetizing a 2-fluoro phenol compound shown in a formula IV. The phenol compound shown in the formula I is prepared into a 2-pyridine oxygroup arene compound shown in a formula II through an Ullmann reaction, the 2-pyridine oxygroup arene compound shown in the formula II is mixed with a palladium catalyst, a fluorinating reagent, an additive and an organic solvent, the mixture is stirred under the temperature of 30-160 DEG C to perform a fluorination reaction to obtain an ortho-position fluoridated 2-pyridine oxygroup arene compound shown in a formula III, and the ortho-position fluoridated 2-pyridine oxygroup arene compound shown in the formula III is prepared into the 2-fluoro phenol compound shown in the formula IV through the action of alkali. The method provided by the present invention has the advantages of mild reaction conditions, simplicity in operations, good substrate adaptability, high fluorination selectivity and the like. The 2-fluoro phenol compound is shown in the figure below.
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- Tubular continuous o-fluorophenol production method
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The present invention discloses a tubular continuous o-fluorophenol production method comprising tubular diazo reaction of a nitrosyl sulfuric acid solution and an o-fluoroaniline solution in a tubular reactor to obtain a diazo solution; tubular hydrolysis reaction of the diazo solution and a copper sulphate water solution in the tubular reactor to obtain a hydrolysis solution; and after-treatment of the hydrolysis solution to obtain o-fluorophenol. The method uses the tubular reactor for the tubular diazo reaction and the tubular hydrolysis reaction to solve the phenomenon of material backmixing and uneven temperature distribution of kettle-type reaction, reduces the incidence of side effects, and improves the yield of the product.
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Paragraph 0044
(2016/12/07)
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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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- Biocatalytic One-Pot Synthesis of l-Tyrosine Derivatives from Monosubstituted Benzenes, Pyruvate, and Ammonia
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l-Tyrosine derivatives were obtained in >97% ee via a biocatalytic one-pot two-step cascade using substituted benzenes, pyruvate, and NH3 as starting materials. In the first step, monosubstituted arenes were regioselectively hydroxylated in the o-position by monooxygenase P450 BM3 (using O2 as oxidant with NADPH-recycling) to yield the corresponding phenols, which subsequently underwent C-C coupling and simultaneous asymmetric amination with pyruvate and NH3 using tyrosine phenol lyase to furnish l-DOPA surrogates in up to 5.2 g L-1. Instead of analytically pure arenes, crude aromatic gasoline blends containing toluene were used to yield 3-methyl-l-tyrosine in excellent yield (2 g L-1) and >97% ee.
- Dennig, Alexander,Busto, Eduardo,Kroutil, Wolfgang,Faber, Kurt
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p. 7503 - 7506
(2015/12/11)
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- Thermal Protodeboronation of hydroxyarene Boronic Acids and Its Application to ortho- and meta- Functionalization of hydroxyarene Using Boronic Acids as Blocking and Directing Groups
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The present invention refers to hydroxy arene boron acid compounds that thermal de borohydride of phenolic compounds using functional groups in ortho-or meta-position with hydroxy [...] manufacturing method relates to, more particularly boron position and outputs ortho of phenol then substituted acid, ortho-or meta-position boron arene hydroxy then introduced to a functional groups in making and compounds, thermal de using borohydride said boron acid by removing phenol from ortho-or meta-position functional groups in have been introduced method for preparing the compounds of arene hydroxy relates to. Manufacturing method of arene compound hydroxy the present invention according to such as iridium or a palladium metal catalyst-free, a stronger acid than the acid or base conditions, a low-temperature reaction acid and acetic anhydride the microbeam generating reactions, by causing or permitting a condition without requiring a step of client and, simply phenol from ortho-or meta-position for introducing functional groups to hydroxy arene compound can be produced.
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Paragraph 0092; 0106-0108
(2016/10/27)
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- Direct hydroxylation of arenes with O2 catalyzed by V@CN catalyst
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A vanadium doped graphitic carbon nitride catalyst has been prepared and used for the direct hydroxylation of arenes with O2. Substituted arenes with electron-withdrawing groups such as CN, NO2, COOH, CF3, and COCH3 were oxygenated to the corresponding phenols in moderate yields. The catalyst also proved applicable for the hydroxylation of aromatic halides (F, Cl, and Br) with O2.
- Li, Yan,Li, Bing,Chen, Ting,Zhou, Zhicheng,Wang, Jun,Huang, Jun
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p. 1086 - 1092
(2015/07/01)
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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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- Fries rearrangement: Scalable synthesis of key fluoro building blocks 3-fluoro-4-methoxybenzoyl chloride and 1,2-diethoxy-3-fluorobenzene
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Lewis acid catalyzed Fries rearrangement of 2-fluorophenyl acetate (3) was performed on kg scale. The ortho 5 and para 4 isomers obtained were separated in an industrially feasible way. Compound 4 was then converted into fluorinated building block 3-fluoro-4-methoxybenzoyl chloride (1) while compound 5 was converted into 1,2-diethoxy-3-fluorobenzene (2) in high yields.
- Yerande, Swapnil G.,Shendage, Deepak M.,Wakchaure, Prasad B.,Phadtare, Ganesh R.,Bhoite, Madhavrao Y.,Gangopadhyay, Ashok Kumar,Nagarajan, Kuppuswamy,Rupp, Richard Helmut
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p. 2426 - 2429
(2014/05/06)
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- Protonation switching to the least-basic heteroatom of carbamate through cationic hydrogen bonding promotes the formation of isocyanate cations
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We found that phenethylcarbamates that bear ortho-salicylate as an ether group (carbamoyl salicylates) dramatically accelerate O-C bond dissociation in strong acid to facilitate generation of isocyanate cation (N-protonated isocyanates), which undergo subsequent intramolecular aromatic electrophilic cyclization to give dihydroisoquinolones. To generate isocyanate cations from carbamates in acidic media as electrophiles for aromatic substitution, protonation at the ether oxygen, the least basic heteroatom, is essential to promote C-O bond cleavage. However, the carbonyl oxygen of carbamates, the most basic site, is protonated exclusively in strong acids. We found that the protonation site can be shifted to an alternative basic atom by linking methyl salicylate to the ether oxygen of carbamate. The methyl ester oxygen ortho to the phenolic (ether) oxygen of salicylate is as basic as the carbamate carbonyl oxygen, and we found that monoprotonation at the methyl ester oxygen in strong acid resulted in the formation of an intramolecular cationic hydrogen bond (>C=O+-H...O) with the phenolic ether oxygen. This facilitates O-C bond dissociation of phenethylcarbamates, thereby promoting isocyanate cation formation. In contrast, superacid-mediated diprotonation at the methyl ester oxygen of the salicylate and the carbonyl oxygen of the carbamate afforded a rather stable dication, which did not readily undergo C-O bond dissociation. This is an unprecedented and unknown case in which the monocation has greater reactivity than the dication.
- Kurouchi, Hiroaki,Sumita, Akinari,Otani, Yuko,Ohwada, Tomohiko
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supporting information
p. 8682 - 8690
(2014/07/21)
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- Efficient hydroxylation of aromatic compounds catalyzed by an iron(II) complex with H2O2
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A mononuclear iron(II) complex, Et4N[Fe(C10H 6NO2)3], coordinated by three 1-nitroso-2-naphtholate ligands in a fac-N3O3 geometry, was initiated to catalyze the direct hydroxylation of aromatic compounds to phenols in the presence of H2O2 under mild conditions. Various reaction parameters, including the catalyst dosage, temperature, mole ratio of H2O2 to benzene, reaction time and solvents which could affect the hydroxylation activity of the catalyst, were investigated systematically for benzene hydroxylation to obtain ideal benzene conversion and high phenol distribution. Under the optimum conditions, the benzene conversion was 10.2% and only phenol was detected. The catalyst was also found to be active towards hydroxylation of other aromatic compounds with high substrate conversions. The hydroxyl radical formed due to the reaction of the catalyst and H2O2 was determined to be the crucial active intermediate in the hydroxylation. A rational pathway for the formation of the hydroxyl radical was proposed and justified by the density functional theory calculations. Copyright
- Wang, Xiao,Zhang, Tianyong,Li, Bin,Yang, Qiusheng,Jiang, Shuang
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p. 666 - 672
(2014/12/09)
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- Visible-light-induced oxygenation of benzene by the triplet excited state of 2,3-dichloro-5,6-dicyano-p-benzoquinone
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Photocatalytic oxygenation of benzene to phenol occurs under visible-light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in an oxygen-saturated acetonitrile solution of benzene and tert-butyl nitrite. The photocatalytic reaction is initiated by photoinduced electron transfer from benzene to the triplet excited state of DDQ.
- Ohkubo, Kei,Fujimoto, Atsushi,Fukuzumi, Shunichi
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supporting information
p. 5368 - 5371
(2013/06/04)
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- Protodeboronation of ortho- and para-phenol boronic acids and application to ortho and meta functionalization of phenols using boronic acids as blocking and directing groups
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The first metal-free thermal protodeboronation of ortho- and para-phenol boronic acids in DMSO was developed. The protodeboronation was successfully applied to the synthesis of ortho- and meta-functionalized phenols using the boronic acid moiety as a blocking group and a directing group, respectively. Mechanistic studies suggested that this protodeboronation proceeds through the coordination of water to the boron atom followed by σ-bond metathesis.
- Lee, Chun-Young,Ahn, Su-Jin,Cheon, Cheol-Hong
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p. 12154 - 12160
(2014/01/06)
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- Regioselective o-hydroxylation of monosubstituted benzenes by P450 BM3
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Dream come true: A new monooxygenase catalyst shows excellent activity for the hydroxylation of halogenated benzenes, anisole, and toluene with almost complete ortho regioselectivity (see scheme; R=F, Cl, Br, I, CH3, OCH3). The substrates were hydroxylated at room temperature in water without cosolvent using molecular oxygen as oxidant. Copyright
- Dennig, Alexander,Luelsdorf, Nina,Liu, Haifeng,Schwaneberg, Ulrich
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p. 8459 - 8462
(2013/09/02)
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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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- 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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- 2-(Trimethylsilyl)ethanol as a new alcohol equivalent for copper-catalyzed coupling of aryl iodides
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2-(Trimethylsilyl)ethanol as a new alcohol equivalent has been employed for copper-catalyzed coupling of aryl iodides. Using mild reaction conditions, it has been observed that substituted phenols and phenols with sensitive functional groups can be readily prepared.
- Dibakar, Mullick,Prakash, Anjanappa,Selvakumar, Kumaravel,Ruckmani, Kandasamy,Sivakumar, Manickam
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p. 5338 - 5341
(2011/10/19)
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- Synthesis, structural properties, and catalytic behavior of Cu-BTC and mixed-linker Cu-BTC-PyDC in the oxidation of benzene derivatives
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Mixed-linker metal-organic frameworks based on the Cu-BTC structure have been synthesized in which the benzene-1,3,5-tricarboxylate (BTC) linkers have been partially replaced by pyridine-3,5-dicarboxylate (PyDC). X-ray-based techniques (powder XRD and XAS), thermal analysis, and infrared spectroscopy proved that a desired amount of PyDC (up to 50%) can be incorporated without changing significantly the crystal structure. The pyridine unit can be seen as a defect site in the local coordination environment of the dimeric copper units, which is significantly altering their electronic structure and the catalytic properties. Both Cu-BTC and the mixed Cu-BTC-PyDCs catalyze the demanding direct hydroxylation of toluene both in acetonitrile and in neat substrate. Different selectivity toward the desired ortho- and para-cresol and other oxidation products (benzaldehyde, benzyl alcohol, methylbenzoquinone) was observed for Cu-BTC and the Cu-BTC-PyDCs, respectively. Leaching tests and comparison with homogeneously dissolved Cu catalysts indicate mainly a heterogeneous reaction pathway.
- Marx, Stefan,Kleist, Wolfgang,Baiker, Alfons
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experimental part
p. 76 - 87
(2011/08/04)
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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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- Fluorination of aromatic compounds with N-fluorobenzenesulfonimide under solvent-free conditions
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Reactions of N-fluorobenzenesulfonimide with methylbenzenes, phenols, and phenol ethers were studied under solvent-free conditions. The rate constant ratio for the reactions with mesitylene and durene indicates polar mechanism of the process. Solvent-free fluorination of aromatic compounds with N-fluorobenzenesulfonimide in some cases is more selective than reactions with other N-F reagents in a solvent.
- Andreev,Borodkin,Shubin
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scheme or table
p. 1468 - 1473
(2010/03/24)
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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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- 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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- Kinetic study of alkaline hydrolysis of substituted phenyl tosylates. XXII. Variation of ortho substituent effect with solvent
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The second-order rate constants k (dm3 mol-1 s -1) for the alkaline hydrolysis of meta-, para-, and ortho-substituted phenyl tosylates 4-CH3C6H 4SO2OC6H4-X in aqueous 0.5 M Bu 4NBr have been measured spectrophotometrically in a wide temperature range. The log k values for ortho-substituted derivatives at various temperatures together with meta- and para-substituted derivatives were analyzed using the modified Fujita-Nishioka equation log km,p,ortho = c 0 + c1(m,p,ortho)σ° + c 2(ortho)σ1 + c3(1/T) + c 4(m,p,ortho)(1/T)σ° + c5(ortho)(1/T) σI. In order to study the dependence of substituent effects, especially ortho inductive and resonance terms on different solvent parameters, the following equation was used: Δlog km,p,ortho = c 0 + c1(m,p,ortho)σ° + c 2(ortho)σI + c3ΔE + c 4ΔY + c5ΔP + c 6(m,p,ortho)ΔEσ° + + c 7(m,p,ortho)ΔYσ° + c 8(m,p,ortho)ΔPσ° + c 9(ortho)ΔEσI + c 10(ortho)ΔYσI + c 11(ortho)ΔPσI. Δlog k = log k X - log kH, σ° and σI, are the Taft polar and inductive substituent constants, E, Y and P, are the solvent electrophilicity, polarity and polarizability parameters, respectively. In data treatment ΔE = ES - EH2O, ΔY = YS - YH2O, ΔP = PS - PH2O were used. The solvent electrophilicity was found to be the main factor responsible for changes in the ortho, para, and meta polar substituent effects with medium. The variation of the ortho inductive term with the solvent electrophilicity E S was found to be twice smaller than that for para substituents, while the ortho resonance term appeared to vary with solvent nearly similarly to that for para substituents. The ortho effect caused by the supplementary inductive effect from ortho position was found to disappear in a solvent whose electrophilic solvating power is comparable to pure DMSO (E ≈ 4).
- Nummert, Vilve,Piirsalu, Mare,Lepp, Marika,Maeemets, Vahur,Koppel, Ilmar
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p. 198 - 222
(2007/10/03)
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- Microwave fluorination: A novel, rapid approach to fluorination with Selectfluor
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Fluorination of electron rich aromatic systems with electrophilic fluorination reagents such as Selectfluor and Accufluor is a well-established process. Herein we report results from investigations into the use of such procedures to perform rapid, small-scale fluorinations under microwave irradiation. We have investigated the transformation with a range of different substrates and discuss the effects of two key factors, namely reaction time and choice of fluorination reagent. The use of Selectfluor in acetonitrile at 150°C with microwave heating for 10 min affords products in comparable yields to those obtained by prolonged heating in acetonitrile at its reflux temperature.
- Bluck, Gavin W.,Carter, Neil B.,Smith, Stephen C.,Turnbull, Michael D.
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p. 1873 - 1877
(2007/10/03)
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- Enantioselective hydrogenation of α-aryloxy α,β- unsaturated acids. Asymmetric synthesis of α-aryloxycarboxylic acids
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(Chemical Equation Presented) A facile preparation of chiral α-aryloxy carboxylic acids via asymmetric hydrogenation of the corresponding unsaturated acids has been discovered. A number of catalysts have been identified that give high product enantioselectivity, and the scope of the reaction has been examined with respect to substitution on the aromatic ring and olefin.
- Maligres, Peter E.,Krska, Shane W.,Humphrey, Guy R.
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p. 3147 - 3150
(2007/10/03)
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- Process for generating electrophiles from anions by reaction with electrophilic fluorinating agent
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A process includes substituting a substituent on a substrate. The process includes reacting a salt of an anionic form of the substituent with an electrophilic fluorination agent to provide an electrophile containing a cationic form of the substituent. The electrophile is then electrophilically substituted on the substrate. In some aspects of the process, the substrate can be an aromatic or a non-aromatic. The process can be used for a variety of reactions having electrophilic mechanisms, including halogenation, thiocyanation and nitration.
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- Method for producing an optically active 1-substituted 2-propanol
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A method for producing an optically active 1-substituted 2-propanol of the following formula 1, which comprises reacting a hydroxy aromatic compound of the following formula 2 with an optically active propylene oxide in the presence of a catalyst:AOH??Formula 2CH3C*H(OH)CH2OA??Formula 1wherein A is a univalent aromatic group, and C* is an asymmetric carbon atom.
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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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- Kinetic study of hydrolysis of benzoates. Part XXII. Variation of the ortho inductive, resonance and steric terms with temperature in the alkaline hydrolysis of substituted phenyl benzoates in aqueous 2.25 M Bu4NBr
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The second order rate constants k2 (M-1 s-1) for the alkaline hydrolysis of meta-, para-, and ortho-substituted phenyl benzoates C6H5CO2C6H4-X (X = H, 3-Cl, 3-CH2, 3-NH2, 3-NO2, 4-F, 4-NO2, 2-Cl, 2-F, 2-CH3, 2-OCH3, 2-NO2) in 2.25 M aqueous n-Bu4NBr have been measured spectrophotometrically at various temperatures (15, 25, 30, 40, 50°C). The log k values were treated using both the modified Fujita-Nishioka and the Charton three-parameter correlation equations. The σ°, σ1, σr°, EsB scales were used as the measure of the ordinary polar, inductive, resonance, and steric components of the substituent effects. EsB = (log kx - log kH)H+, where kx and kH are the rate constants of the acidic hydrolysis for ortho-substituted and unsubstituted phenyl benzoates in water at 50°C. The modified Fujita-Nishioka and Charton treatments gave the excellent and identical results. The susceptibility to the induction effect of ortho-substituents was found to be about 0.2 units of the ρ scale smaller [(ρI)ortho = 1.80] than that for meta- and para-substituents [(ρ°)m,p = 2.03], in the alkaline hydrolysis of substituted phenyl benzoates in 2.25 M aqueous n-Bu4NBr at 50°C. Also in this solution, the variation of the susceptibility to the inductive and the resonance effects with temperature for the ortho-derivatives appeared slightly smaller than that for para-derivatives. During the transition from water to 2.25 M aqueous Bu4NBr the susceptibility of the meta- and para-substituent polar effect (ρ°)m,p was found to increase by about 1.0 units, but the susceptibility to the inductive effect of ortho-substituents was enhanced only by about 0.5 units of the ρI scale at 50°C. The variation of the inductive term of ortho-substituents with both solvent and temperature was found to be half that for para-substituents. Variation of the inductive term of ortho-substituents with the solvent and temperature by the same extent had earlier been found for the alkaline hydrolysis of substituted phenyl tosylates, though the ratio of the susceptibilities to the polar influence of meta-, para-, and ortho-substituents in water differed two-fold. The steric term of ortho-substituents for 2.25 aqueous n-Bu4NBr was found to be independent of temperature and nearly equal to the steric term for water.
- Nummert, Vilve,Piirsalu, Mare
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p. 583 - 594
(2007/10/03)
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- Preparation of aromatic fluorides: Facile photo-induced fluorinative decomposition of arenediazonium salts and their related compounds using pyridine-nHF
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By employing pyridine-nHF solution, the photo-induced fluorinative decomposition of arenediazonium salts (ArN2BF4) (fluoro-dediazoniation) and the related compounds, such as quinonediazides and triazenes, has been successfully carried out to produce the corresponding aromatic fluorides (ArF) in good yields. The rate in the fluoro-dediazoniation of para-substituted ArN2BF4 in pyridine-nHF solution did not obey the classical Hammett equation but conformed well to Taft's treatment [dual substituent parameter relationships (DSP)]. In the thermal fluoro-dediazoniation of ArN2BF4 the rate of reaction was significantly influenced by the substituents in the substrates. On the contrary, only a slight effect by the substituents was observed on the rate of the photo-induced fluoro-dediazoniation of ArN2BF4.
- Sawaguchi, Masanori,Fukuhara, Tsuyoshi,Yoneda, Norihiko
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p. 127 - 133
(2007/10/03)
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- Synthesis, Properties, and Reactivity of N,N'-Difluorobipyridinium and Related Salts and Their Applications as Reactive and Easy-To-Handle Electrophilic Fluorinating Agents with High Effective Fluorine Content
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N,N′-Difluoro-2,2′-, -2,4′-, -3,3′-, -4,4′-bipyridinium and substituted N,N′-difluoro-2,2′-bipyridinmm bis(triflates), bis(tetrafluoroborates), bis(hexafluorophosphates), and bis(hexafluoroantimonates) 1-9 were synthesized in high yields by the direct fluorination of a mixture of a bipyridyl and a Lewis acid, a Br?nsted acid, or the alkali metal salt of an acid. The higher homologues, trimer 10 and polymer 11, were also synthesized. Unsubstituted or electron-donating group-substituted N,N′- difluorobipyridinium salts are stable nonhygroscopic crystals, while the electron-withdrawing group- substituted N,N′-diflurobipyridinium salts 3, 5, and 6 are moisture-sensitive crystals. Hydrolysis of 1b in boiling water gave 3,3′-dihydroxy-2,2′-bipyridyl. The reactivity determination indicated that the fluorinating capability decreased in the order 2,2′- ? 2,4' > 3,3′- ≈ 4,4′-isomer ? N-fluoropyridinium salt and that the two N-F moieties in a molecule were effective for fluorination. This fluorination occurred in a step-by-step manner, and the reactivity difference between the first and second fluorinations was very small. N,N′-Difluoro-2,2′-bipyridinium bis(tetrafluoroborate) (1b) is thus shown to be a highly reactive and easy-to-handle electrophilic fluorinating agent with the high effective fluorine content (103.3 g/kg) for preparing many fluoro organic compounds.
- Umemoto, Teruo,Nagayoshi, Masayuki,Adachi, Kenji,Tomizawa, Ginjiro
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p. 3379 - 3385
(2007/10/03)
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- N-Halogeno compounds part 19: Electrophilic fluorinating agents of the multiple mono-N-fluoro class derived from nitrogen heterocycles
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Bis(4-fluoro-1,4-diazoniabicyclo[2.2.2]oct-1-yl)-ethane and -propane tetratriflates (4, 5), and 1,1′-difluoro-4,4′-bipyridinium ditriflate (6) were prepared by solution-phase direct fluorination of bis(4-aza-1-azoniabicyclo[2.2.2]oct-1-yl)-ethane or -propane ditriflate (10, 11), and 4,4′-bipyridine respectively. The same technique was employed to convert the complex 4,4′-bipyridine · 2BF3 to the mono-NF derivative F3B-NC5H4-C5H4N+-F BF4- (7) and its monomethylated analogue (4-NC5H4)C5H4N+-CH3 TfO- to F-+ NC5H4-C5H4N+-CH3 (TfO- )2 (8). The results of site-specific electrophilic fluorination of some model substrates (1-morpholinocyclohexene, phenol, 2-naphthol, anisole, di-and tri-methoxybenzene) with 5, 7 and 8 are presented.
- Banks, R. Eric,Besheesh, Mohamed K.,Mohialdin-Khaffaf, Suad N.,Sharif, Iqbal
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p. 157 - 161
(2007/10/03)
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- Bi(III) as new catalyst for the selective hydrolysis of esters
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The selective hydrolysis of esters has been carried out in a reaction catalyzed by Bi(III)-mandelate in DMSO. The reaction is specific of aryl esters. Competition tests resulted in the quantitative hydrolysis of p-nitrophenyl acetate in the presence of ethyl benzoate or other aryl acetates.
- Le Boisselier, Veronique,Postel, Michele,Dunach, Elisabet
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p. 2981 - 2984
(2007/10/03)
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- N-Halogeno compounds. Part 16. Perfluoro-[N-fluoro-N-(4-pyridyl)acetamide] - A new site-selective electrophilic fluorinating agent
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Perfluoro-[N-fluoro-N-(4-pyridyl)acetamide] (2), prepared via direct fluorination of the sodium salt (4) of perfluoro-[N-(4-pyridyl)-acetamide], readily fluorinates diethyl sodio(phenyl)malonate [→PhCF(CO2Et)2], 1-morpholinocyclohexene(→2-fluorocyclohexanone), anisole (→2-and 4-FC6H4OMe), and phenol (→2-and 4-FC6H4OH) under mild conditions. The sodium salt precursor (4) of this side-chain N-F reagent (2) is easily made from pentafluoropyridine via the trifluoroacetylation of its 4-amino derivative or, more directly, by treating it with two equivalents of the monosodium salt of trifluoroacetamide.
- Banks,Besheesh,Tsiliopoulos
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