- A metallomicelle enzyme model for phospholipase C catalysis and inhibition
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A CuII metallomicelle mimics phospholipase C enzymes in catalysis and inhibition of transesterification reactions of phosphate diesters.
- Kriste, Angela G.,Vizitiu, Dragos,Thatcher, Gregory R. J.
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- Increasing the steric hindrance around the catalytic core of a self-assembled imine-based non-heme iron catalyst for C-H oxidation
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Sterically hindered imine-based non-heme complexes4and5rapidly self-assemble in acetonitrile at 25 °C, when the corresponding building blocks are added in solution in the proper ratios. Such complexes are investigated as catalysts for the H2O2oxidation of a series of substrates in order to ascertain the role and the importance of the ligand steric hindrance on the action of the catalytic core1, previously shown to be an efficient catalyst for aliphatic and aromatic C-H bond oxidation. The study reveals a modest dependence of the output of the oxidation reactions on the presence of bulky substituents in the backbone of the catalyst, both in terms of activity and selectivity. This result supports a previously hypothesized catalytic mechanism, which is based on the hemi-lability of the metal complex. In the active form of the catalyst, one of the pyridine arms temporarily leaves the iron centre, freeing up a lot of room for the access of the substrate.
- Frateloreto, Federico,Capocasa, Giorgio,Olivo, Giorgio,Abdel Hady, Karim,Sappino, Carla,Di Berto Mancini, Marika,Levi Mortera, Stefano,Lanzalunga, Osvaldo,Di Stefano, Stefano
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p. 537 - 542
(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 0046-0049
(2021/09/29)
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- Reduced Amino Acid Schiff Base-Iron(III) Complexes Catalyzing Oxidation of Cyclohexane with Hydrogen Peroxide
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The reduced amino acid Schiff base ligands have been prepared and were coordinated with ferric chloride to generate the iron(III) complexes. The ligands and complexes have been characterized using FT-IR, UV-vis, elemental analysis, ICP-AES analysis, mass spectra etc. After the structural characterization, these complexes were applied for the oxidation of cyclohexane using hydrogen peroxide as the oxidant under mild conditions. The activity tests showed that the L-phenylalanine-derived reduced Schiff base iron(III) complex(Ph?FeCl) afforded the highest yield of cyclohexanol and cyclohexanone(total yield up to 23.2 %). Notably, the Ph?FeCl complex catalyzes the reaction via a heterogeneous approach, allowing the complex to be separated and recycled conveniently after the oxidation reaction. Besides, the Ph?FeCl catalyst can also be extended for the selective oxidation of other alkanes and aromatics into alcohols, ketones and phenols etc. Finally, the reaction mechanism of cyclohexane oxidation on the iron(III) complex was proposed as well by the free radical inhibitors and EPR study of active intermediates.
- Zheng, Anna,Zhou, Qingqing,Ding, Bingjie,Li, Difan,Zhang, Tong,Hou, Zhenshan
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p. 3385 - 3395
(2021/08/23)
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- Aromatic C?H Hydroxylation Reactions with Hydrogen Peroxide Catalyzed by Bulky Manganese Complexes
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The oxidation of aromatic substrates to phenols with H2O2 as a benign oxidant remains an ongoing challenge in synthetic chemistry. Herein, we successfully achieved to catalyze aromatic C?H bond oxidations using a series of biologically inspired manganese catalysts in fluorinated alcohol solvents. While introduction of bulky substituents into the ligand structure of the catalyst favors aromatic C?H oxidations in alkylbenzenes, oxidation occurs at the benzylic position with ligands bearing electron-rich substituents. Therefore, the nature of the ligand is key in controlling the chemoselectivity of these Mn-catalyzed C?H oxidations. We show that introduction of bulky groups into the ligand prevents catalyst inhibition through phenolate-binding, consequently providing higher catalytic turnover numbers for phenol formation. Furthermore, employing halogenated carboxylic acids in the presence of bulky catalysts provides enhanced catalytic activities, which can be attributed to their low pKa values that reduces catalyst inhibition by phenolate protonation as well as to their electron-withdrawing character that makes the manganese oxo species a more electrophilic oxidant. Moreover, to the best of our knowledge, the new system can accomplish the oxidation of alkylbenzenes with the highest yields so far reported for homogeneous arene hydroxylation catalysts. Overall our data provide a proof-of-concept of how Mn(II)/H2O2/RCO2H oxidation systems are easily tunable by means of the solvent, carboxylic acid additive, and steric demand of the ligand. The chemo- and site-selectivity patterns of the current system, a negligible KIE, the observation of an NIH-shift, and the effectiveness of using tBuOOH as oxidant overall suggest that hydroxylation of aromatic C?H bonds proceeds through a metal-based mechanism, with no significant involvement of hydroxyl radicals, and via an arene oxide intermediate. (Figure presented.).
- Masferrer-Rius, Eduard,Borrell, Margarida,Lutz, Martin,Costas, Miquel,Klein Gebbink, Robertus J. M.
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p. 3783 - 3795
(2021/03/09)
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- Nickel-catalyzed oxidative hydroxylation of arylboronic acid: Ni(HBTC)BPY MOF as an efficient and ligand-free catalyst to access phenolic motifs
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A straightforward and mild oxidative ipso-hydroxylation of arylboronic acids has been achieved using a simple and non-noble metal, nickel-based reusable heterogeneous catalyst Ni(HBTC)BPY MOF (HBTC = benzene-1,3,5-tricarboxylate, BPY = 4,4′-bipyridine) in the presence of benign hydrogen peroxide as an oxidant under ambient reaction condition. The Ni(HBTC)BPY MOF exhibits excellent catalytic activity towards the formation of phenols from diverse arylboronic acids within short time and can be reused up to five times without any notable loss in its activity as well as shown high functional group tolerance even in the presence of sensitive functionalities and useful to achieve hydroxyl group in heterocycles.
- Latha, Ganesapandian,Devarajan, Nainamalai,Karthik, Murugan,Suresh, Palaniswamy
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- Reductive Aromatization of Quinols with B2pin2 as Deoxidizing Agent
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We have demonstrated B2pin2 as superior deoxidizing agent for the reductive deoxygenation of quinol derivatives under basic conditions. A wide range of highly functionalized phenols were obtained in good yields including a complex drug molecule, which revealed the high functional group tolerance of this protocol.
- Liu, Bin,Xu, Yin,Luo, Zhibin,Xie, Jimin
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supporting information
p. 1022 - 1024
(2020/03/19)
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- Mechanistic study of carboxylic acid and phosphate ester cleavage by oximate metal complexes surpassing the limiting reactivity of highly basic free oximate anions
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Two tridentate and one tetradentate new ligands containing the terminal oxime group separated from secondary amino and pyridine groups as additional binding sites by two or three methylene groups have been prepared. Their acid-base properties, as well as the composition and stability of their complexes with Zn(ii) and Cd(ii) ions, were determined by potentiometric and spectrophotometric titrations. The X-ray structure of a Cd(ii) complex of a related tridentate oxime ligand previously studied in solution was determined. All oximate complexes show high reactivity in the cleavage of aryl acetates, paraoxon, parathion and 4-nitrophenyl diphenyl phosphate, with rate constants significantly surpassing the limiting rate constants observed for highly basic free oximate anions. The second-order rate constants for individual oximate complexes in solution are assigned to each ligand, metal cation and substrate. The results of the cleavage of 4-substituted phenyl acetates were analyzed in terms of Br?nsted correlations with the leaving group pKa, which demonstrated a change in the rate determining step from the nucleophilic attack to the leaving group departure upon an increase in the leaving group basicity. The zero slope of the Br?nsted correlation for the nucleophilic attack indicates transition state stabilization through electrophilic assistance by the metal ion. This interpretation is supported by metal selectivity in the relative efficiency of the cleavage of paraoxon and parathion. The existence of the alpha-effect in ester cleavage by coordinated oximates is confirmed by an analysis of the Br?nsted correlations with the nucleophile basicity for metal bound oximate and alkoxo or hydroxo nucleophiles. The very high reactivity of the oximate complexes of the new ligands is attributed to transition state stabilization and to the removal of the solvational imbalance of oximate anions that impedes the expected increase in the reactivity of highly basic free anions.
- Flores-Alamo, Marcos,Gómez-Tagle, Paola,Lugo-González, José Carlos,Yatsimirsky, Anatoly K.
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supporting information
p. 2452 - 2467
(2020/03/05)
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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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- Catalyst- And solvent-free: Ipso -hydroxylation of arylboronic acids to phenols
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A catalyst-free method for the hydroxylation of arylboronic acids to form the corresponding phenols with sodium perborate as the oxidant was developed using water as the solvent. Under the reaction conditions, the yield of phenol reached 92% at only 5 min. Moreover, the reaction could be conducted without a catalyst under the solvent-free condition, the efficiency of which was as high as that of a liquid-phase reaction. Using a microcalorimeter, the reaction was found to be an exothermic reaction. The reaction mechanism was investigated and understood via DFT calculations, which revealed that it was a nucleophilic reaction.
- Yang, Xiufang,Jiang, Xulu,Wang, Weitao,Yang, Qi,Ma, Yangmin,Wang, Kuan
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p. 34529 - 34534
(2019/11/13)
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- Thermal Stability Study of 4-tert-Butylphenol
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Abstract: The thermal stability of 4-tert-butylphenol has been studied in the temperature range of 673–738?K, the components of the thermolysis reaction mixture have been identified, a kinetic model of the process has been proposed, and the rate constants and parameters of the Arrhenius equation have been calculated for all of the reactions considered. The predominant role of 4-tert-butylphenol isomerization transformations has been established. Information on the 4-tert-butylphenol thermal stability facilitates to a more substantiated approach to its use as an additive that increases the oxidative stability of fuels and lubricants, as well as an antioxidant for polymer compositions.
- Shakun,Nesterova,Naumkin
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p. 120 - 127
(2019/04/27)
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- Functionalized Allyl Aryl Ether Synthesis from Benzoic Acids Using a Dearomatization and Decarboxylative Allylation Approach
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A strategy toward the preparation of substituted allyl aryl ethers from benzoic acids via a dearomatization and decarboxylative allylation (DcA) reaction is presented. The benzoic acids undergo a dearomatization to give alkylated 2,5-cyclohexadienyl ketoesters which are subjected to a palladium-catalyzed DcA reaction, providing a variety of functionalized allyl aryl ethers. In addition, the combination of a resonance stabilized DcA reaction with a Claisen rearrangement for the synthesis of multisubstituted phenols and applying to dihydroplicatin B derivative synthesis is also presented.
- Hsieh, Cheng-En,Jiang, Yu-Min,Chou, Chih-Ming
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supporting information
p. 653 - 665
(2019/01/24)
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- Hydrogenolysis of lignin model compounds into aromatics with bimetallic Ru-Ni supported onto nitrogen-doped activated carbon catalyst
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Lignin is the most abundant and renewable resources for production of natural aromatics. In this paper, new bimetallic catalytic system of Ru and Ni supported onto nitrogen-doped activated carbon (Ru-Ni-AC/N) was developed and its performances on hydrogenolysis of lignin model compounds under mild reaction conditions (1.0 MPa, 230 °C, in aqueous) were investigated. The results indicate that Ru-Ni-AC/N was a highly active, selective and stable catalyst for the conversion of lignin model compounds into aromatics, e.g. phenol, benzene and their derivatives. As verified by BET, XRD, HRTEM, XPS, H2-TPR and ICP-MS, the strong synergistic effects between i) Ru and Ni and ii) metals and N-groups were contributed to its excellent aromatics selectivity. What's more, the introduction of electron rich N atoms on AC was beneficial to the stabilization of metal particles, which greatly enhanced the durability of the catalyst.
- Hu, Yinghui,Jiang, Guangce,Xu, Guoqiang,Mu, Xindong
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p. 316 - 326
(2018/01/05)
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- Direct hydroxylation of benzene and aromatics with H2O2 catalyzed by a self-assembled iron complex: Evidence for a metal-based mechanism
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An iminopyridine Fe(ii) complex, easily prepared in situ by self-assembly of cheap and commercially available starting materials (2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 in a 2 : 2 : 1 ratio), is shown to be an effective catalyst for the direct hydroxylation of aromatic rings with H2O2 under mild conditions. This catalyst shows a marked preference for aromatic ring hydroxylation over lateral chain oxidation, both in intramolecular and intermolecular competitions, as long as the arene is not too electron poor. The selectivity pattern of the reaction closely matches that of electrophilic aromatic substitutions, with phenol yields and positions dictated by the nature of the ring substituent (electron-donating or electron-withdrawing, ortho-para or meta-orienting). The oxidation mechanism has been investigated in detail, and the sum of the accumulated pieces of evidence, ranging from KIE to the use of radical scavengers, from substituent effects on intermolecular and intramolecular selectivity to rearrangement experiments, points to the predominance of a metal-based SEAr pathway, without a significant involvement of free diffusing radical pathways.
- Capocasa, Giorgio,Olivo, Giorgio,Barbieri, Alessia,Lanzalunga, Osvaldo,Di Stefano, Stefano
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p. 5677 - 5686
(2017/12/07)
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- Highly Selective and Efficient Ring Hydroxylation of Alkylbenzenes with Hydrogen Peroxide and an Osmium(VI) Nitrido Catalyst
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The OsVI nitrido complex, OsVI(N)(quin)2(OTs) (1, quin=2-quinaldinate, OTs=tosylate), is a highly selective and efficient catalyst for the ring hydroxylation of alkylbenzenes with H2O2 at room temperature. Oxidation of various alkylbenzenes occurs with ring/chain oxidation ratios ranging from 96.7/3.3 to 99.9/0.1, and total product yields from 93 % to 98 %. Moreover, turnover numbers up to 6360, 5670, and 3880 can be achieved for the oxidation of p-xylene, ethylbenzene, and mesitylene, respectively. Density functional theory calculations suggest that the active intermediate is an OsVIII nitrido oxo species.
- Kwong, Hoi-Ki,Lo, Po-Kam,Yiu, Shek-Man,Hirao, Hajime,Lau, Kai-Chung,Lau, Tai-Chu
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supporting information
p. 12260 - 12263
(2017/09/06)
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- Direct oxidation of the C(sp2)-C(sp3) bond from benzyltrimethylsilanes to phenols
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A novel pathway for direct conversion of benzylsilanes to phenols by oxidation with Na2S2O8 and oxygen is efficiently developed under mild and neutral conditions. The reaction shows good functional group tolerance to afford phenols in moderate yields. The possible mechanism is proposed based on the isotopic labeling trials.
- Li, Wei,Gao, Guolin,Gao, Yuan,Yang, Chao,Xia, Wujiong
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p. 5291 - 5293
(2017/07/10)
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- Construction of Acid–Base Synergetic Sites on Mg-bearing BEA Zeolites Triggers the Unexpected Low-Temperature Alkylation of Phenol
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Novel Mg-bearing BEA zeolites are synthesized to simultaneously endow significantly enhanced basicity without compromising acidity over the zeolite framework. Serving as efficient solid acid–base bifunctional catalysts, they achieve the liquid-phase selective methylation of phenol with methanol to produce o- and p-cresol (o/p=2) under mild conditions. The method is readily extendable to the alkylation of phenols with various alcohols. Stereo- and regioselectivity (>95 % for p-product) was attained on the alkylation of phenol with bulky tert-butyl alcohol, rendering the first acid–base cooperative shape-selective catalysis relying on the basicity of zeolites. A preliminary mechanistic analysis reveals that the remarkable activity and shape-selectivity come from the superior special acidic–basic synergetic catalytic sites on the uniform microporous channels of the BEA zeolite.
- Xie, Jingyan,Zhuang, Wenxia,Zhang, Wei,Yan, Ning,Zhou, Yu,Wang, Jun
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p. 1076 - 1083
(2017/03/27)
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- Chemoselective oxidation of aryl organoboron systems enabled by boronic acid-selective phase transfer
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We report the direct chemoselective Brown-type oxidation of aryl organoboron systems containing two oxidizable boron groups. Basic biphasic reaction conditions enable selective formation and phase transfer of a boronic acid trihydroxyboronate in the presence of boronic acid pinacol (BPin) esters, while avoiding speciation equilibria. Spectroscopic investigations validate a base-promoted phase-selective discrimination of organoboron species. This phenomenon is general across a broad range of organoboron compounds and can also be used to invert conventional protecting group strategies, enabling chemoselective oxidation of BMIDA species over normally more reactive BPin substrates. We also demonstrate the selective oxidation of diboronic acid systems with chemoselectivity predictable a priori. The utility of this method is exemplified through the development of a chemoselective oxidative nucleophile coupling.
- Molloy, John J.,Clohessy, Thomas A.,Irving, Craig,Anderson, Niall A.,Lloyd-Jones, Guy C.,Watson, Allan J. B.
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p. 1551 - 1559
(2017/02/10)
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- Synthesis and catalytic performance of HMCM-49/MCM-41 composite molecular sieve for alkylation of phenol with isopropanol
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HMCM-49/MCM-41 composite molecular sieve was synthesized with hydrothermal method. The physicochemical properties of the composite were characterized by using XRD, FT-IR, SEM, N2 isothermal adsorption-desorption and NH3-TPD. Results of different characterizations indicated that the synthesized composite molecular sieve possessed the characteristics of both HMCM-49 and MCM-41. XRD and N2 isothermal adsorption-desorption revealed that it has both micropores and mesopores, a larger surface area than that of HMCM-49, NH3-TPD and pyridine adsorbed FT-IR revealed that the strong acidic sites that caused side reaction in HMCM-49 are deactivated in the composite molecular sieve of HMCM-49/MCM-41. When applied to the alkylation of phenol with isopropanol, the HMCM-49/MCM-41 composite molecular sieve exhibit an enhanced catalytic performance with significant enhancement in p-isopropylphenol and o-isopropylphenol selectivity, which can be ascribed to the composite characteristics of HMCM-49 and MCM-41. This kind of material will has widely industrial application in preparation of alkyl-phenol.
- Wei, Liguo,Wang, Dong,Dong, Yongli,Song, Weina,Liu, Xiaoxu,Song, Kunyao
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p. 2061 - 2066
(2017/01/28)
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- Introduction of PEG-SANM nanocomposite as a new and highly efficient reagent for the promotion of the silylation of alcohols and phenols and deprotection of the silyl ethers
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Poly (ethylene glycol)-sulfonated sodium montmorillonite (PEG-SANM) nanocomposite was prepared by a simple method and characterized using XRD, TGA, SEM, TEM, and FT-IR techniques. After preparation and characterization, this reagent was used as a highly efficient and reusable solid acid catalyst for the chemoselective silylation of alcohols and phenols and deprotection of the obtained silyl ethers. Themethod offers several advantages including high to excellent yields of the products, short reaction times, easy preparation of the catalyst and easy work-up procedure. In addition, the catalyst can be recycled and reused at least for five times without significant decrease in the catalytic activity.
- Shirini, Farhad,Shojaei, Abdollah Fallah,Heirati, Seyedeh Zahra Dalil
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p. 944 - 951
(2016/07/06)
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- Direct Hydroxylation of Benzene to Phenol Using Hydrogen Peroxide Catalyzed by Nickel Complexes Supported by Pyridylalkylamine Ligands
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Selective hydroxylation of benzene to phenol has been achieved using H2O2 in the presence of a catalytic amount of the nickel complex [NiII(tepa)]2+ (2) (tepa = tris[2-(pyridin-2-yl)ethyl]amine) at 60°C. The maximum yield of phenol was 21% based on benzene without the formation of quinone or diphenol. In an endurance test of the catalyst, complex 2 showed a turnover number (TON) of 749, which is the highest value reported to date for molecular catalysts in benzene hydroxylation with H2O2. When toluene was employed as a substrate instead of benzene, cresol was obtained as the major product with 90% selectivity. When H218O2 was utilized as the oxidant, 18O-labeled phenol was predominantly obtained. The reaction rate for fully deuterated benzene was nearly identical to that of benzene (kinetic isotope effect = 1.0). On the basis of these results, the reaction mechanism is discussed.
- Morimoto, Yuma,Bunno, Shuji,Fujieda, Nobutaka,Sugimoto, Hideki,Itoh, Shinobu
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supporting information
p. 5867 - 5870
(2015/05/27)
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- Ligand- and base-free synthesis of phenols by rapid oxidation of arylboronic acids using iron(III) oxide
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Fe2O3 catalyzed rapid oxidation of arylboronic acids to obtain phenols in excellent yields (90-95%) in the presence of atmospheric oxygen under solar VIS-light irradiation using α-Fe2O3 as a catalyst in ligand- and base-free conditions is presented.
- Sawant, Sanghapal D.,Hudwekar, Abhinandan D.,Aravinda Kumar,Venkateswarlu, Vunnam,Singh, Parvinder Pal,Vishwakarma, Ram A.
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p. 811 - 814
(2015/03/03)
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- PROCESS FOR PREPARING A PARA-LINEAR ALKYL-SUBSTITUTED HYDROXYAROMATIC COMPOUND
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Disclosed herein is a process for preparing an isomeric mixture comprising a major amount of a para-linear mono-alkyl-substituted hydroxyaromatic compound. The process involves the steps of: (a) providing an isomeric mixture comprising a major amount of a para-di(alkyl-substituted)aromatic compound; wherein a first alkyl substituent is a C3 to C8 alkyl moiety and a second alkyl substituent is a C4+n to C8+n linear alkyl moiety, wherein n is 0 to 42 and further wherein the second alkyl substituent is at least one carbon atom greater than the first alkyl substituent; (b) subjecting the isomeric mixture comprising a major amount of a para-di(alkyl-substituted)aromatic compound to oxidation conditions in the presence of an oxygen-containing source, thereby converting the first alkyl substituent which is a C3 to C8 alkyl moiety to a hydroperoxide-containing substituted moiety to produce an isomeric mixture comprising a major amount of a para-linear alkyl-substituted, hydroperoxide-containing substituted aromatic compound; and (c) converting the hydroperoxide-containing substituted moiety to a hydroxyl moiety thereby providing an isomeric mixture comprising a major amount of a para-linear mono-alkyl-substituted hydroxyaromatic compound.
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Paragraph 0088; 0089
(2015/05/05)
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- Metal-free synthesis of substituted phenols from arylboronic acids in water at room temperature
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A convenient, efficient and practical metal-free method for the synthesis of substituted phenols from arylboronic acids has been developed. The protocol uses hydrogen peroxide as a hydroxylating agent, ammonium bicarbonate as an additive, and the reactions were conveniently performed in water at room temperature. The method shows an excellent tolerance of functional groups, so it will find a wide variety of applications in academic and industrial research.
- Jiang, Min,Yang, Hai-Jun,Li, Yong,Jia, Zhi-Ying,Fu, Hua
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supporting information
p. 715 - 719
(2014/06/09)
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- Ligand- and base-free synthesis of phenols by rapid oxidation of arylboronic acids using iron(III) oxide
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Fe2O3 catalyzed rapid oxidation of arylboronic acids to obtain phenols in excellent yields (90-95%) in the presence of atmospheric oxygen under solar VIS-light irradiation using α-Fe2O 3 as a catalyst in ligand- and base-free conditions is presented.
- Sawant, Sanghapal D.,Hudwekar, Abhinandan D.,Aravinda Kumar,Venkateswarlu, Vunnam,Singh, Parvinder Pal,Vishwakarma, Ram A.
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p. 811 - 814
(2014/02/14)
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- Metal-free UV-Vis-light-induced aerobic oxidative hydroxylation of arylboronic acids in the absence of a photosensitizer
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A simple and efficient method has been developed for the metal-free photosynthesis of phenols with UV-Vis (ultraviolet-visible) light in quartz tubes. The protocol uses readily available arylboronic acids as the starting materials, triethylamine as the sacrificial electron donor, and air as the oxidant. The method shows high efficiency, environmental friendliness and mild reaction conditions, without the addition of a photosensitizer. This journal is the Partner Organisations 2014.
- Jiang, Min,Li, Yong,Yang, Haijun,Zong, Ruilong,Jin, Yunhe,Fu, Hua
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p. 12977 - 12980
(2014/04/03)
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- Efficient cleavage of alkyl aryl ethers using an ionic liquid under microwave irradiation
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A highly reliable dealkylation protocol of alkyl aryl ethers, whose alkyl groups are longer than methyl group, has been developed. We report that various ethyl, n-propyl, and benzyl aryl ethers are successfully cleaved using an ionic liquid, 1-n-butyl-3-methylimidazolium bromide, [bmim][Br], under microwave irradiation. Despite many characteristics such as lower cost and less toxicity of the alkylating agents, and greater hydrophobicity of the products, longer alkyl ethers have been significantly less exploited than methyl ethers, probably due to more difficulty in the deprotection step. Since it has the same advantages as the demethylation method developed by this group including mild conditions, short reaction time, and small use of the ionic liquids, the dealkylation protocol can greatly encourage the broader use of longer alkyl groups in the protection of phenolic groups. As with our previous study of demethylation using [bmim][Br], the microwave irradiation is crucial for the deprotection of longer alkyl aryl ethers. Unlike the conventional heating, which causes either low conversion or decomposition, the microwave irradiation seems to more effectively provide energy to cleave the ether bonds and therefore suppresses the undesired reactions.
- Park, Se Kyung,Battsengel, Oyunsaikhan,Chae, Junghyun
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supporting information
p. 174 - 178
(2013/08/24)
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- Decomposition of ozonolysis peroxide products of (+)-α- and (+)-β-pinenes in methanol by Fe(III) salts
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The reaction of ozonolysis peroxide products of (+)-α and (+)-β-pinenes with Fe(III) salts in MeOH was studied. It was found that decomposition of methoxyhydroperoxides obtained via ozonolysis of (+)-β-pinene using FeCl3×6H2O occurre
- Garifullina,Salimova,Kasradze,Spirikhin,Kukovinets
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p. 791 - 793
(2013/06/05)
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- Preparation, characterization and use of 1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient, halogen-free and reusable ionic liquid catalyst for the trimethylsilyl protection of hydroxyl groups and deprotection of the obtained trimethylsilanes
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Novel 1,3-disulfonic acid imidazolium hydrogen sulfate, a halogen-free ionic liquid, is a recyclable and eco-benign catalyst for the trimethylsilyl protection of hydroxyl groups at room temperature under solvent free conditions to afford trimethylsilanes in excellent yields (92-100%) and in very short reaction times (1-5 min). Deprotection of the resulting trimethylsilanes can also be achieved using the same catalyst in methanol. The catalyst was characterized by IR, 1H NMR, 13C NMR and MS studies. All the products were extensively characterized by IR, 1H NMR, MS, and elemental and melting point analyses. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be recovered and reused for several times without loss of activity. The work-up of the reaction consists of a simple separation, followed by concentration of the crude product and purification.
- Shirini, Farhad,Khaligh, Nader Ghaffari,Akbari-Dadamahaleh, Somayeh
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- Chemo- and regioselective direct hydroxylation of arenes with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
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Peroxide in, phenol out: The catalyst [-PW10O38V 2(μ-OH)2]3- showed high activity in the hydroxylation of various aromatic compounds with aqueous H2O 2. The system was regioselective, producing para-phenols from monosubstituted benzene derivatives. Furthermore, alkylarenes with reactive side-chain Ca spa 3-H bonds could be chemoselectively hydroxylated without significant formation of side-chain oxygenated products. Copyright
- Kamata, Keigo,Yamaura, Taiyo,Mizuno, Noritaka
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supporting information; experimental part
p. 7275 - 7278
(2012/08/28)
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- Catalytic performance of Al-MCM-48 molecular sieves for isopropylation of phenol with isopropyl acetate
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Al-MCM-48 molecular sieves (Si/Al molar ratios = 25, 50, 75, and 100) were synthesized hydrothermally using cetyltrimethylammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffr
- Venkatachalam, Kandan,Visuvamithiran, Pitchai,Sundaravel, Balachandran,Palanichamy, Muthiapillai,Murugesan, Velayutham
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experimental part
p. 478 - 486
(2012/07/17)
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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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- Microwave-assisted demethylation of methyl aryl ethers using an ionic liquid
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An efficient demethylation of methyl aryl ethers using an ionic liquid, 1-n-butyl-3-methylimidazolium bromide ([bmim][Br]) has been developed. Methyl aryl ethers are successfully cleaved by the halide anion of [bmim][Br], without aid of any other activating agents. In this reaction, microwave irradiation was found to be crucial for the effective conversion. The newly developed protocol is a very attractive green chemical process as it utilizes minimal amount of cleaving reagents and does not require additional activating agents or solvents. Under the conditions described herein, a broad range of methyl aryl ethers were converted to the corresponding phenolic compounds in moderate to excellent yields in a short time. Georg Thieme Verlag Stuttgart New York.
- Park, Jiyeon,Chae, Junghyun
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experimental part
p. 1651 - 1656
(2010/08/22)
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- Methylation of phenolic hydroxyl group and demethylation of anisoles
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A mild methylation of phenolic hydroxyl groups with iodomethane was enabled in the presence of sodium bis(trimethylsilyl)amide at room temperature. The reverse reaction, namely demethylation of methyl phenyl ethers, was easily achieved by microwave heating with neat iodotrimethylsilane.
- Sato, Nobuhiro,Endo, Hiroyuki
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experimental part
p. 229 - 230
(2009/12/03)
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- Reaction of menthol and phenol in the presence of aluminium alkoxides
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Phenol was alkylated with menthol in the presence of organoaluminium catalysts such as aluminium phenoxide and aluminium isopropoxide. Reaction products were isolated and characterized. Certain features of the process were determined.
- Chukicheva,Fedorova,Koroleva,Kuchin
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experimental part
p. 450 - 454
(2009/04/11)
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- Liquid-phase oxidation of alkyl-substituted cyclohexylbenzenes
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The reactivity of alkyl-substituted cyclohexylbenzenes in liquid-phase oxidation was estimated by the k2/√k6 value which considerably decreased as the number of methyl groups in the substrate molecule increased. The observed difference in the reactivity of the title compounds was attributed to the degree of coplanarity of intermediate radical species.
- Koshel',Kurganova,Smirnova,Koshel',Plakhtinskii,Belysheva
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scheme or table
p. 553 - 556
(2009/04/05)
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- Zirconia-modified superacid UDCaT-5: An efficient and versatile catalyst for alkylation reactions under solvent-free conditions
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UDCaT-5, a modified version of zirconia, efficiently catalyzes alkylation of phenols with alcohols under environmentally safe, heterogeneous reaction conditions with high selectivity and in excellent yields. The high content present in UDCaT-5 with preservation of tetragonal phase of zirconia was responsible for the superactivity. Several phenolic compounds carrying either electron-sulfer releasing or electron-withdrawing substituents in the ortho, meta, and para positions afforded high yields of the products. Copyright Taylor & Francis Group, LLC.
- Yadav, Ganapati D.,Pathre, Ganesh S.
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p. 2684 - 2691
(2008/12/22)
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- Desaturation of alkylbenzenes by cytochrome P450BM3 (CYP102A1)
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A study was conducted to investigate the desaturation of alkylbenezenes by cytochrome P450BM3 (CYP102A1). It was observed during the study that oxidation of alkylbenzenes with CYP102A1 involves a gamut of P450 activity types that are terminal, sub-terminal benzylic and aromatic hydroxylation; terminal and sub-terminal desaturation; and epoxidation of the olefins. It was also found that the desaturation of cumene by CYP102A1 is sensitive to α-deuteration and insensitive to β-deuteration. Intramolecular deuterium isotope study revealed that the first abstraction in the desaturation of valproic acid and ezlopitant by microsomal P450s take place from activated carbon atoms. The increased β-hydroxylation percentages show that the β-carbon lies closer to the ferryl oxygen in the KT5.
- Whitehouse, Christopher J.C.,Bell, Stephen G.,Wong, Luet-Lok
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supporting information; scheme or table
p. 10905 - 10908
(2009/11/30)
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- (2R)-2-Methylchromane-2-carboxylic acids: Discovery of selective PPARα agonists as hypolipidemic agents
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A SAR study was conducted on chromane-2-carboxylic acid toward selective PPARα agonisim. As a result, highly potent, and selective PPARα agonists were discovered. The optimized compound 43 exhibited robust lowering of total cholesterol levels in hamster and dog animal models.
- Koyama, Hiroo,Boueres, Julia K.,Miller, Daniel J.,Berger, Joel P.,MacNaul, Karen L.,Wang, Pei-Ran,Ippolito, Marc C.,Wright, Samuel D.,Agrawal, Arun K.,Moller, David E.,Sahoo, Soumya P.
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p. 3347 - 3351
(2007/10/03)
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- METHOD FOR PRODUCING AROMATIC ALKOXY KETONES
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The invention relates to a method for producing aromatic alkoxy ketones. According to said method, an alkoxyalkyl aromate of general formula RO(Ar)CHCH3R', wherein R represents methyl, ethyl, propyl, butyl or tert.-butyl, Ar represents phenyl or naphthyl, and R' represents hydrogen or methyl, is reacted in the presence of oxygen, a transition metal salt and an organic alkyl ammonium compound, in a liquid phase at a temperature of between 40 and 150 °C.
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Page/Page column 6
(2008/06/13)
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- Enhanced O-dealkylation activity of SiCl4/LiI with catalytic amount of BF3
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Dibenzyloxydihydrobenzoxathiin 1, which resisted debenzylation with SiCl4/LiI, was effectively debenzylated with SiCl4/LiI in the presence of a catalytic amount of BF3. The HCl salt of the bis-debenzylated product 2 was isolated in 90% yield and 99% purity. This enhanced dealkylation activity has also been observed with other substrates.
- Zewge, Daniel,King, Anthony,Weissman, Steven,Tschaen, David
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p. 3729 - 3732
(2007/10/03)
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- Preparation of Hydroperoxides by N-Hydroxyphthalimide-Catalyzed Aerobic Oxidation of Alkylbenzenes and Hydroaromatic Compounds and Its Application
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An efficient approach to phenols and aldehydes through the formation of hydroperoxides from alkylbenzenes was successfully achieved by aerobic oxidation using N-hydroxyphthalimide (NHPI) as a catalyst. The oxidation of various alkylbenzenes with dioxygen by NHPI followed by treatment with a Lewis acid or triphenylphosphine led to phenols or aldehydes, respectively, in good yields. For example, the aerobic oxidation of cumene in the presence of a catalytic amount of NHPI at 75°C and subsequent treatment with H2SO4 gave phenol in 77% yield. 1,4-Dihydroxybenzene (61%) and 4-isopropylphenol (33%) were obtained from 1,4-diisopropylbenzene. On the other hand, dibenzyl ether was converted into phenol or benzaldehyde upon treatment of the resulting hydroperoxide with InCl3 or PPh3, respectively.
- Fukuda, Osamu,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 809 - 813
(2007/10/03)
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- Oxidation of organometallic compounds (RM, M = Li, MgBr, ZnBr, CuCNLi, Cu(R)CNLi2) with tBuOOLi, Ti(OiPr)4-mediated with tBuOOH, and with O2, to give alcohols (ROH). Are radicals R? involved?
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Organometallic compounds (RM, M = Li, MgBr, ZnBr, Cu(CN)Li, CuR(CN)Li2) are oxidized with tBuOOLi (or PhCMe2OOLi) (method A) to the corresponding alcohols (ROH), in good to very good yields. This oxidation works also well with the protic system Ti(OiPr)4 + tBuOOH (method B) in the case of RM, M = Li, MgBr and ZnBr. Stereochemical studies with the configurationally stable cis- and trans-cyclopropyl metal compounds, cis- and trans-1-M, respectively, show that the reactions of RM, M = Li, MgBr, with tBuOOLi (method A) and Ti(OiPr)4 + tBuOOH (method B) follow a SN2-type pathway of the nucleophile RM at the electrophilic (although anionic!) oxygen atom of tBuOOLi(TiX3) to give ROM (isolated as the esters 2) with retention of configuration at R. In contrast, the oxidations with dioxygen O2 (method C) occur with loss of stereochemistry in the cyclopropyl alcohols ROH (RM, M = Li, MgBr), and additional formation of cyclopropyl dimers R-R 3 in the case of RM, M = Cu(CN)Li, CuR(CN)Li2. This is due to facile electron transfer from RM to O2 and fast isomerization (dimerization) of the intermediate radicals R?. The high tendency of RM cuprates, M = Cu(CN)Li, CuR(CN)Li2, for electron transfer reactions is also indicated by some loss of stereospecificity in the formation of ROH, and some dimer 3 formation, even with the oxidant tBuOOLi (method A) .
- M?ller, Michael,Husemann, Marc,Boche, Gernot
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- Non-catalytic and selective alkylation of phenol with propan-2-ol in supercritical water
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Phenol can be alkylated with propan-2-ol without catalyst in supercritical water at 673 K with mainly ortho substituted alkylphenols being obtained and alkylation reaction rate increasing with increasing water density.
- Sato,Sekiguchi,Adschiri,Arai
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p. 1566 - 1567
(2007/10/03)
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- The continuous acid-catalyzed dehydration of alcohols in supercritical fluids: A new approach to the cleaner synthesis of acetals, ketals, and ethers with high selectivity
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We report a new continuous method for forming ethers, acetals and ketals using solid acid catalysts, DELOXAN ASP or AMBERLYST 15, and supercritical fluid solvents. In the case of ether formation, we observe a high selectivity for linear alkyl ethers with little rearrangement to give branched ethers. Such rearrangement is common in conventional syntheses. Our approach is effective for a range of n-alcohols up to n-octanol and also for the secondary alcohol 2-propanol. In the reaction of phenol with an alkylating agent, the continuous reaction can be tuned to give preferential O- or C- alkylation with up to 49% O-alkylation with supercritical propene. We also investigate the synthesis of a range of cyclic ethers and show an improved method for the synthesis of THF from 1,4-butandiol under very mild conditions.
- Gray, William K.,Smail, Fiona R.,Hitzler, Martin G.,Ross, Stephen K.,Poliakoff, Martyn
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p. 10711 - 10718
(2007/10/03)
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- Acid-catalyzed hydrolysis of some primary alkyl phenyl ethers
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Products were analyzed and rate constants of disappearance and hydrolysis, alkylation and/or rearrangement were measured for methyl, ethyl, propyl and allyl phenyl ethers by GC in concentrated aqueous perchloric acid solutions. Chlorination of the substrate and possibly of the product, phenol, was observed beside the hydrolysis of methyl phenyl ether and a slight chlorination of phenol beside the hydrolysis of ethyl phenyl ether. A marked Claisen rearrangement to isopropylphenols and alkylation to propyl isopropylphenyl ethers were observed in addition to the hydrolysis of propyl phenyl ether. The Claisen rearrangement to o-allylphenol was estimated to be quantitative in the case of allyl phenyl ether. The change of the reaction mechanism from A-2 (MeOPh and EtOPh) possibly via A-2(carbocation)(PrOPh?) to A-1 (allyl phenyl ether and possibly PrOPh) was deduced from the products, reaction rates, activation parameters, solvent deuterium isotope effect and parameters of excess acidity plots. Acta Chemica Scandinavica 1997.
- Lajunen, Martti,Laine, Riitta,Aaltonen, Marika
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p. 1155 - 1161
(2007/10/03)
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- ALKYLATING PROPERTIES OF ACID ORGANIC PHOSPHATES
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Under the action of phenols and alcohols, acid alkyl phosphates undergo transesterification, which is accompanied by dealkylation of the latter and alkylation of the alcohols (phenols) at the hydroxy groups and aromatic rings.Isopropyl phosphates are stronger alkylating agents than methyl phosphates.Diphenyl methyl and phenyl dimethyl phosphates yield products of methylation of their own aromatic rings only upon prolonged pyrolysis.In all cases organic polyphosphates are formed.
- Munik, S. N.,Eliseenkov, V. N.,Ivanov, B. E.
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p. 378 - 382
(2007/10/03)
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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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- Acid-Catalyzed Hydrolysis of Some Secondary Alkyl Phenyl Ethers in Perchloric Acid: Kinetics and Mechanism
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Hydrolysis rates and products of isopropyl, cyclopentyl and cyclohexyl phenyl ethers were studied in concentrated aqueous perchloric acid solutions.The activation parameters, solvent deuterium isotope effects, dependences of the reaction rates on acid concentration, substituent effects and products were in agreement with the A-1 mechanism.The pKSH+ values (-6.13 to -5.76) and the slope parameters m* (av. 0.98 +/- 0.03) were measured spectrophotometrically by the excess acidity method.They were used to calculate the m++-parameters (1.46-2.01).Comparisons weremade with the hydrolyses of exo- ad endo-2-norbornyl phenyl ethers and secondary alyl methanesulfonates.
- Lajunen, Martti,Kaehkoenen, Mika
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p. 726 - 731
(2007/10/02)
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