- A Method for the Measurement of Site-Specific Tautomeric and Zwitterionic Microspecies Equilibrium Constants
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We describe a method for the individual measurement of simultaneously occurring, unimolecular, site-specific "microequilibrium" constants as in, for example, prototronic tautomerism and zwitterionic equilibria.Our method represents an elaboration of that of Nygren et al. (Anal.Chem. 1996, 68, 1706-10), which thereby becomes generalized and improves the accuracy.Specifically, by making spectral measurements as a function of temperature, we demonstrate the ability to determine site-specific microenthalpies unambiguously.Analysis proceeds via multivariate nonlinear regression modeling of, for example, the Gibbs-Helmholtz relation.Additional determinations of macroscopic equilibrium constants as a function of temperature, in combination with the previously determined microenthalpies, in turn enables the determination of all remaining site-specific thermodynamic parameters, i.e., microentropies, micro free energies, and/or microequilibrium constants, and moreover allows us to resolve and measure the spectra of tautomeric isocoulombers.To our knowledge, we have hereby devised the first such universally applicable and accurate measurement method on record.
- D'Angelo, Joseph C.,Collette, Timothy W.
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- Reaction of OH with Pyridine. Pulse-Radiolytic and Product-Analysis Studies
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The products obtained from the reaction of OH radicals, generated radiolytically, with pyridine under conditions where the intermediate 1-azahydroxycyclohexadienyl radicals are oxidized to isomeric hydroxypyridines have been examined by high-performance liquid chromatographic methods.From product-analysis data, the initial radiation chemical yields of o-, m-, and p-hydroxypyridines are 1.0, 3.8, and 0.3, respectively.The high yield of m-hydroxypyridine exemplifies the electrophilic nature of OH.The low yield of p-hydroxypyridine is attributed to the failure to quantitatively oxidize the 1-aza-p-hydroxycyclohexadienyl radical by the more powerful oxidant such as IrCl62-.The isomeric OH adducts of pyridine exhibit selectivity in reactivity with the two oxidants examined, and their reducing strength follows the order meta > ortho > para.From optical pulse radiolysis the second-order rate constant for the electron-transfer processes between hexachloroiridate and meta and ortho pyridine-OH adducts was determined to be 5.8 * 1E8 M-1 s-1.
- Selvarajan, N.,Raghavan, N. V.
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- Conversion of 5-hydroxymethylfurfural into 6-(hydroxymethyl)pyridin-3-ol: A pathway for the formation of pyridin-3-ols in honey and model systems
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The formation of 6-(hydroxymethyl)pyridin-3-ol by ring expansion of 5-(hydroxymethyl)furfural (HMF) in the presence of ammonia-producing compounds was studied to determine the routes of formation of pyridin-3-ols in foods. 6-(Hydroxymethyl)pyridin-3-ol was produced from HMF in model systems, mostly at neutral pH values, as a function of reaction times and temperature and with an activation energy (Ea) of 74 ± 3 kJ/mol, which was higher than that of HMF disappearance (43 ± 4 kJ/mol). A reaction pathway is proposed, which is general for the formation of pyridin-3-ols from 2-oxofurans. Thus, it explains the conversions of furfural into pyridin-3-ol and of 2-acetylfuran into 2-methylpyridin-3-ol, which were also studied. When honey and sugarcane honey were heated, they produced different pyridin-3-ols, although 6-(hydroxymethyl)pyridin-3-ol was the pyridine-3-ol produced to the highest extent. Obtained results suggest that formation of pyridin-3-ols in foods is unavoidable when 2-oxofurans are submitted to thermal heating and ammonia (or ammonia-producing compounds) is present.
- Hidalgo, Francisco J.,Lavado-Tena, Cristina M.,Zamora, Rosario
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- Cleavage of aromatic methyl ethers by chloroaluminate ionic liquid reagents
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We have discovered serendipitously that chloroaluminate ionic liquids can cleave aromatic methyl ethers under surprisingly mild conditions. Three ionic liquids, viz. [TMAH]-[Al2Cl7], [BMIM][Al2Cl7], and [EMIM][Al2Cl6I], and aluminum chloride were compared in the selective demethylation of 4,5-dimethoxyindanone at the 4-methoxy-function. The ionic liquids exhibited a remarkably high selectivity (96:4) in comparison with aluminum chloride (70:30). In addition, the reaction time was drastically shortened when the ionic liquids were used. Interestingly, the three ionic liquids displayed the same reactivity in the demethylation of 4,5-dimethoxyindanone. Considering the lower cost and the bulk availability of the precursors of [TMAH][Al2Cl7], we conclude that this is the most attractive ionic liquid from an industrial point of view. To make the large-scale application of [TMAH][Al2Cl7] feasible, we have developed a safe upscalable method for its preparation. Furthermore, the scope of ether cleavage by the ionic liquid reagent [TMAH][Al2Cl7] was investigated and it was found that aromatic methyl-, al- lyl-, and benzyl-ether cleavage is applicable to a variety of heterocyclic compounds. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Kemperman, Gerardus J.,Roeters, Theodorus A.,Hilberink, Peter W.
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- Demethylation of methoxypyridines with sodium trimethylsilanethiolate
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Demethylation of methoxypyridines was accomplished in 55-87percent yield by use of ca. 1.5-2.5 equivalents of NaSSiMe3 in 1,3-dimethyl-2-imidazolidinone at 120-180 deg C.This method was found applicable to a methoxyquinoline and methoxypyridines containing a second substituent, such as Cl, OMe, and COOMe.
- Shiao, Min-Jen,Ku, Wei-Shen,Hwu, Jih Ru
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- A BODIPY dye as a reactive chromophoric/fluorogenic probe for selective and quick detection of vapors of secondary amines
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A new reaction based fluorescence turn-off strategy for detection of secondary amines was developed. The probe shows fast response and high selectivity to secondary amines in solution/film at sub-ppm levels through chromogenic and fluorescent dual-mode signal changes.
- Fu, Yanyan,He, Qingguo,Zhu, Defeng,Wang, Yuerong,Gao, Yixun,Cao, Huimin,Cheng, Jiangong
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- Isomeric methoxypyridine-1-oxides and 1-methoxypyridones: electronic spectra and structure
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The electronic spectra of the isomeric of hydroxypyridine-1-oxides and 1-hydroxy-pyridones were calculated by the CNDO/CI method.Transition energies, intensities and assignments were compared with the u.v. spectra recorded for the first time on all the methyl.substituted isomers under similar conditions in non-aqueous solvents.Ground state properties of the same compounds were calculated after a full geometry optimization using the CNDO/2 and MINDO/3 approximations.
- Cignitti, Maurizio,Soccorsi, Laura,Gatta, Franco,Cotta-Ramusino, Marina
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- Highly efficient heterogeneous V2O5@TiO2 catalyzed the rapid transformation of boronic acids to phenols
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A V2O5@TiO2 catalyzed green and efficient protocol for the hydroxylation of boronic acid into phenol has been developed utilizing environmentally benign oxidant hydrogen peroxide. A wide range of electron-donating and the electron-withdrawing group-containing (hetero)aryl boronic acids were transformed into their corresponding phenol. The methodology was also applied successfully to transform various natural and bioactive molecules like tocopherol, amino acids, cinchonidine, vasicinone, menthol, and pharmaceuticals such as ciprofloxacin, ibuprofen, and paracetamol. The other feature of the methodology includes gram-scale synthetic applicability, recyclability, and short reaction time.
- Upadhyay, Rahul,Singh, Deepak,Maurya, Sushil K.
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supporting information
p. 3925 - 3931
(2021/08/24)
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- Building a Pyrazole–Benzothiadiazole–Pyrazole Photosensitizer into Metal–Organic Frameworks for Photocatalytic Aerobic Oxidation
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Charge separation plays a crucial role in regulating photochemical properties and therefore warrants consideration in designing photocatalysts. Metal–organic frameworks (MOFs) are emerging as promising candidates for heterogeneous photocatalysis due to their structural designability and tunability of photon absorption. Herein, we report the design of a pyrazole–benzothiadiazole–pyrazole organic molecule bearing a donor–acceptor–donor conjugated π-system for fast charge separation. Further attempts to integrate such a photosensitizer into MOFs afford a more effective heterogeneous photocatalyst (JNU-204). Under visible-light irradiation, three aerobic oxidation reactions involving different oxygenation pathways were achieved on JNU-204. Recycling experiments were conducted to demonstrate the stability and reusability of JNU-204 as a robust heterogeneous photocatalyst. Furthermore, we illustrate its applications in the facile synthesis of pyrrolo[2,1-a]isoquinoline-containing heterocycles, core skeletons of a family of marine natural products. JNU-204 is an exemplary MOF platform with good photon absorption, suitable band gap, fast charge separation, and extraordinary chemical stability for proceeding with aerobic oxidation reactions under visible-light irradiation.
- Jin, Ji-Kang,Wu, Kun,Liu, Xin-Yi,Huang, Guo-Quan,Huang, Yong-Liang,Luo, Dong,Xie, Mo,Zhao, Yifang,Lu, Weigang,Zhou, Xiao-Ping,He, Jian,Li, Dan
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supporting information
p. 21340 - 21349
(2021/12/17)
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- A copper nitride catalyst for the efficient hydroxylation of aryl halides under ligand-free conditions
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Copper nitride (Cu3N) was used as a heterogeneous catalyst for the hydroxylation of aryl halides under ligand-free conditions. The cubic Cu3N nanoparticles showed high catalytic activity, comparable to those of conventional Cu catalysts with nitrogen ligands, demonstrating that the nitrogen atoms in Cu3N act as functional ligands that promote hydroxylation.
- Mitsudome, Takato,Mizugaki, Tomoo,Xu, Hang,Yamaguchi, Sho
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supporting information
p. 6593 - 6597
(2021/08/10)
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- Electrochemical-induced hydroxylation of aryl halides in the presence of Et3N in water
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A thorough study of mild and environmentally friendly electrochemical-induced hydroxylation of aryl halides without a catalyst is presented. The best protocol consists of hydroxylation of different aryl iodides and aryl bromides by water solution in the presence of Et3N under air, affording the target phenols in good isolated yields. Moreover, aryl chlorides were successfully employed as substrates. This methodology also provides a direct pathway for the formation of deoxyphomalone, which displayed a significant anti-proliferation effect.
- Ke, Fang,Lin, Chen,Lin, Mei,Long, Hua,Wu, Mei,Yang, Li,Zhuang, Qinglong
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supporting information
p. 6417 - 6421
(2021/08/03)
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- Photocatalytic synthesis of phenols mediated by visible light using KI as catalyst
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A transition-metal-free hydroxylation of iodoarenes to afford substituted phenols is described. The reaction is promoted by KI under white LED light irradiation and uses atmospheric oxygen as oxidant. By the use of triethylamine as base and solvent, the corresponding phenols are obtained in moderate to good yields. Mechanistic studies suggest that KI and catalysis synergistically promote the cleavage of C-I bond to form free aryl radicals.
- Huiqin, Wei,Wu, Mei
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supporting information
(2021/11/30)
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- Catalyst-Free N-Deoxygenation by Photoexcitation of Hantzsch Ester
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A mild and operationally simple protocol for the deoxygenation of a variety of heteroaryl N-oxides and nitroarenes has been developed. A mixture of substrate and Hantzsch ester is proposed to result in an electron donor-acceptor complex, which upon blue-light irradiation undergoes photoinduced electron transfer between the two reactants to afford the products. N-oxide deoxygenation is demonstrated with 22 examples of functionally diverse substrates, and the chemoselective reduction of nitroarenes to the corresponding hydroxylamines is also shown.
- Cardinale, Luana,Jacobi Von Wangelin, Axel,Konev, Mikhail O.
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supporting information
(2020/02/15)
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- Preparation method of (S)-1-tert-butyloxycarbonyl-3-hydroxypiperidine
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The invention discloses a preparation method of (S)-1-tert-butyloxycarbonyl-3-hydroxypiperidine, and relates to the technical field of biological pharmacy. The preparation method comprises the following steps: 1, preparing 3-hydroxypyridine (2) as a raw material; 2, preparing racemic 3-hydroxypiperidine (3) from 3-hydroxypyridine (2); 3, preparing a derivative (2S, 3S)-N-(4-chlorphenyl)-2, 3-dihydroxy succinamic acid (4) from racemic 3-hydroxypiperidine (3) and D-tartaric acid; 4, carrying out resolution reaction on the derivative (2S, 3S)-N-(4-chlorphenyl)-2, 3-dihydroxy succinamic acid (4) prepared from D-tartaric acid to obtain a (S)-hydroxypiperidine salt (5); and 5, subjecting an obtained mixture to extraction, concentration and crystallization, to prepare a (S)-1-tert-butyloxycarbonyl-3-hydroxypiperidine salt (5). The preparation process has the advantages that the synthesis steps are reduced, the yield is increased, an adopted chiral resolving agent can be recycled, and the preparation process is suitable for industrial production.
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Paragraph 0024-0025; 0034-0035; 0044-0045; 0055-0056
(2020/03/25)
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- Method for synthesizing phenol or derivative thereof in aqueous phase by photocatalytic one-pot method
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The invention discloses a method for synthesizing phenol or a derivative thereof in an aqueous phase by a photocatalytic one-pot method. The method comprises the following steps: by taking a compoundaryl halide shown in formula (I) as a raw material and water as a solvent, adding a catalyst and an auxiliary agent, and carrying out reacting under the conditions of alkali and visible light to obtain the phenol or the derivative (II) thereof. Compared with the prior art, the method is applicable to a large number of functional groups, high in yield, few in byproducts, simple and safe to operate,low in cost and environmentally friendly, wherein R is selected from substituted or non-substituted phenyl, pyridyl, quinolyl or pyrimidinyl; X is selected from halogen; the substituted phenyl is substituted by C1-C4 alkyl, C1-C4 alkoxy, hydroxyl, halogen, cyano, aldehyde group, nitro, amino, acetyl or carboxyl; and the substituted pyridyl, quinolyl or pyrimidinyl is pyridyl, quinolyl or pyrimidinyl substituted by C1-C4 alkyl.
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Paragraph 0032-0033; 0081-0082; 0085-0106
(2020/12/08)
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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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- Copper nanoparticles supported on highly nitrogen-rich covalent organic polymers as heterogeneous catalysts for the ipso -hydroxylation of phenyl boronic acid to phenol
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This work describes a simple procedure for the synthesis of highly nitrogen-rich covalent organic polymers using commercially available starting materials like melamine and cyanuric chloride as a solid heterogeneous catalyst Cu/TCOP under solvothermal conditions. The structural properties of the as-synthesized solid heterogeneous catalyst were determined by X-ray diffraction (XRD), diffuse reflectance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), 13C-CP MAS nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. The catalytic activity of Cu/TCOP was investigated by focusing on the oxidation of phenylboronic acid under atmospheric conditions in an aqueous medium, achieving a very good yield up to 99%. The reaction performance was evaluated considering the effect of various parameters, such as the amount of the catalyst, reaction time, temperature, and the amount of the base and solvent. The Cu/TCOP catalyst is completely recoverable in a facile manner from the reaction mixture and the efficiency of the copper nanocatalyst can be recovered after five cycles.
- Sadhasivam, Velu,Harikrishnan, Muniyasamy,Elamathi, Ganesan,Balasaravanan, Rajendran,Murugesan, Sepperumal,Siva, Ayyanar
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supporting information
p. 6222 - 6231
(2020/05/13)
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- Synthesis of Phenols via Metal-Free Hydroxylation of Aryl Boronic Acids with Aqueous TBHP
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An alternate procedure for oxidative hydroxylation of aryl boronic acids with aqueous TBHP to access phenols is described. The protocol tolerated various functional groups substituted with aromatic rings. The reaction was performed in water and free from transition metal oxidants.
- Shaikh, Tanveer MahmadAlli
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- Cu(I)/sucrose-catalyzed hydroxylation of arenes in water: The dual role of sucrose
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A protocol for the hydroxylation of aryl halides catalyzed by copper(I) and sucrose in neat water has been developed. The dual role of sucrose, the reaction pathway, and the high selectivity for hydroxylation were investigated using a combination of experimental and theoretical techniques. This journal is
- Murata, Shigeo,Takagi, Mio,Takita, Ryo,Watanabe, Ayako,Watanabe, Kohei
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supporting information
p. 7827 - 7831
(2020/11/02)
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- Preparation method of 3-hydroxypyridine
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The invention belongs to the field of organic synthesis, and particularly relates to a 3-hydroxypyridine preparation method, which comprises: (1) dissolving 3-chloropyridine in a solvent, heating to atemperature of 130-140 DEG C, adding an alkaline hydroxide in batches, carrying out thermal insulation, stirring for 2 hours after the addition is completed, carrying out distillation to remove the solvent after the reaction is completed, adding deionized water, and carrying out distillation again; and (2) cooling the reaction solution in the step (1) to a room temperature, neutralizing the reaction solution with concentrated hydrochloric acid to reduce the pH value to 6-7, heating and reducing the pressure to evaporate water, cooling to 60-70 DEG C, adding methanol, performing reflux under stirring for 30 minutes, cooling to a room temperature, filtering, concentrating the filtrate, and performing reduced pressure distillation. The method has the beneficial effects that the reaction conditions are mild, the operation is easy, the post-treatment is simple, the scale-up production is easy, and the method is very suitable for industrial production; the catalytic effect is good, the yield is high, the raw materials are cheap, and the production cost is low.
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Paragraph 0015; 0018-0029
(2020/05/05)
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- Chemoselective Demethylation of Methoxypyridine
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A chemoselective demethylation method for various methoxypyridine derivatives has been developed. Treatment of 4-methoxypyridine with L-selectride in THF for 2 h at reflux temperature afforded 4-hydroxypyridine in good yield; no reaction to anisole occurred. The utility of our method was demonstrated by the efficient synthesis of the metabolic substances of the antiulcer agent omeprazole. Chemoselective demethylation at the site of 3,5-dimethyl-4-methoxypyridine in the presence of 4-methoxybenzimidazole was achieved.
- Makino, Kosho,Hasegawa, Yumi,Inoue, Takahide,Araki, Koji,Tabata, Hidetsugu,Oshitari, Tetsuta,Ito, Kiyomi,Natsugari, Hideaki,Takahashi, Hideyo
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p. 951 - 954
(2019/05/10)
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- Preparation method of low-cost 3-hydroxypyridine
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The invention relates to a preparation method of low-cost 3-hydroxypyridine. The method comprises the steps of enabling 4-benzylaminobutyrate hydrochloride and 2-haloacetate to be subjected to a substitution reaction so as to obtain N-benzyl-3-aza-1, 7-pimelate diester; then, enabling the N-benzyl-3-aza-1, 7-pimelate diester to be subjected to an intramolecular condensation reaction, and carrying out hydrolytic decarboxylation to obtain N-benzylpiperidin-3-one; then, carrying out catalytic hydrogenolysis to remove benzyl so as to obtain piperidin-3-one; enabling the piperidin-3-one and halogen to be subjected to a halogenating reaction so as to obtain 2, 4-dihalogenated piperidine-3-one; then, enabling the 2, 4-dihalogenated piperidine-3-one and an acid-binding agent to be subjected to an elimination reaction to obtain 3-hydroxypyridine. The raw materials used in the preparation method are low in price and easy to obtain, the operation conditions are mild, simple and convenient, and less wastewater is produced; the method is high in operation safety, environmental protection property, product yield and purity, and low in cost.
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- Tetrafluoropyridyl (TFP): a general phenol protecting group readily cleaved under mild conditions
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Phenols are extremely valuable building blocks in the areas of pharmaceuticals, natural products, materials and catalysts. In order to carry out modifications on phenols, the phenolic oxygen is routinely protected to prevent unwanted side reactions. Presently many of the protecting groups available can require harsh conditions, specialist equipment, expensive or air/moisture-sensitive reagents to install and remove. Here we introduce the use of the tetrafluoropyridyl (TFP) group as a general protecting group for phenols. TFP can be installed in one step with no sensitivity to water or air, and it is stable under a range of commonly employed reaction conditions including acid and base. The TFP protecting group is readily cleaved under mild conditions with quantitative conversion to the parent phenol, observed in many cases in less than 1 hour.
- Brittain, William D. G.,Cobb, Steven L.
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supporting information
p. 2110 - 2115
(2019/02/27)
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- A 3 - hydroxy pyridine preparation method (by machine translation)
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The invention belongs to the field of organic synthesis, in particular to a 3 - hydroxy pyridine method, comprises the following steps: (1) the 3 - chloro pyridine is dissolved in the solvent, heating up to 130 - 140 °C, addition of alkaline hydroxide, after adding insulation stirring 2 h, reaction finishes, and distilled to remove the solvent, the deionized water is added, then distillation; (2) step (1) of the reaction solution in the temperature to room temperature, concentrated hydrochloric acid in the reaction solution is pH and 6 - 7, the temperature of the water evaporated to dryness at reduced pressure, and then cooled to 60 - 70 °C adding methanol, reflux stirring 30 min, cooled to room temperature, filtered, the filtrate is concentrated by reduced pressure distillation after. The beneficial effect of the invention is: mild reaction conditions, is easy to operate, after treatment is simple, and easy to enlarge production, is extremely suitable for industrial production; good catalytic effect, high yield; low prices of raw materials, the production cost is low. (by machine translation)
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Paragraph 0018-0029
(2019/05/28)
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- Reagent Design and Ligand Evolution for the Development of a Mild Copper-Catalyzed Hydroxylation Reaction
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Parallel synthesis and mass-directed purification of a modular ligand library, high-throughput experimentation, and rational ligand evolution have led to a novel copper catalyst for the synthesis of phenols with a traceless hydroxide surrogate. The mild reaction conditions reported here enable the late-stage synthesis of numerous complex, druglike phenols.
- Fier, Patrick S.,Maloney, Kevin M.
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supporting information
p. 3033 - 3036
(2017/06/07)
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- Facile and metal-free synthesis of phenols from benzaldoxime and diaryliodonium salts
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A metal-free, base-promoted facile synthesis of phenol derivatives utilising diaryliodonium salts as the aryl source and benzaldoxime as the hydroxide surrogate has been developed. The reaction is fast and shows good substrate compatibility, giving the corresponding products in good to excellent yields. A gram-scale synthesis of phenols utilising this protocol has also been achieved.
- Zhou, Yongsheng
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p. 591 - 593
(2017/11/14)
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- Silica chloride: An efficient promoter for oxidation of arylboronic acids to phenols
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This work reports simple, highly efficient protocol for the oxidation of arylboronic acids. Various arylboronic acids were selectively and completely converted into their corresponding oxidized phenols using H2O2 as an oxidant in presence of catalytic amount of silica chloride. The results show that silica chloride is a suitable and efficient promoter for the oxidation of arylboronic acids. Heterogeneous catalyst, mild reaction conditions, easy availability of the reagent, easy work-up, excellent yield of corresponding phenols, short reaction time and broad substrate scope makes this protocol attractive and a practical alternative to the existing methods.
- Wagh, Ravindra B.,Nagarkar, Jayashree M.
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supporting information
p. 3323 - 3326
(2017/07/27)
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- Facile and effective approach for oxidation of boronic acids
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This present work illustrates facile and effective approach for oxidation of boronic acids using environmentally benign dimethyl carbonate (DMC) as a solvent with H2O2 as an oxidant at room temperature. In contrast to previous reaction reports, which make use of metal catalyst, hazardous reagent and oxidants that creates environmental concern. This method provides good to excellent yield of products and showed better tolerance towards various functional groups present on boronic acids. Moreover, this developed process is an alternative in terms of inexpensive, non toxic and easy reaction conditions.
- Wagh, Ravindra B.,Nagarkar, Jayashree M.
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supporting information
p. 4572 - 4575
(2017/11/03)
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- Synthesis of Complex Phenols Enabled by a Rationally Designed Hydroxide Surrogate
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The conversion of aryl halides to phenols under mild reaction conditions is a longstanding and formidable challenge in organic chemistry. Herein, we report the rational design of a broadly applicable Pd-catalyzed method to prepare phenols with benzaldehyde oxime as a hydroxide surrogate. These reactions occur under mildly basic conditions and enable the late-stage hydroxylation of several functionally-dense drug-like aryl halides.
- Fier, Patrick S.,Maloney, Kevin M.
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supporting information
p. 4478 - 4482
(2017/04/13)
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- Sustainable oxidations with air mediated by gallic acid: Potential applicability in the reutilization of grape pomace
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Gallic acid converts atmospheric oxygen into hydrogen peroxide, which is able to oxidize arylboronic acids as a proof of concept of sustainable oxidations. Moreover, tannic acid and grape pomace extract are also able to perform oxidations with air. Therefore this work unleashes an alternative method for reutilization and valorization of bio-wastes rich in tannins.
- Scoccia, Jimena,Perretti, Marcelle D.,Monzón, Diego M.,Crisóstomo, Fernando P.,Martín, Víctor S.,Carrillo, Romen
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supporting information
p. 2647 - 2650
(2016/06/06)
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- A chemoselective ipso-hydroxylation of arylboronic acids using urea-hydrogen peroxide under catalyst free condition
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An efficient and practical method for the chemoselective ipso-hydroxylation of arylboronic acids is demonstrated using urea-hydrogen peroxide under catalyst free condition at room temperature. Remarkably, oxidation sensitive functional groups such as olefin, aldehyde, alcohol, ketone, and sulfide as well as heterocycles such as pyridine and thiophene were tolerated under the standard reaction condition. In addition to the solution phase, a solid phase ipso-hydroxylation of arylboronic acids has been investigated with urea hydrogen peroxide. The scope and limitations of the solid phase protocol is discussed.
- Gupta, Surabhi,Chaudhary, Priyanka,Srivastava, Vandana,Kandasamy, Jeyakumar
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supporting information
p. 2506 - 2510
(2016/05/24)
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- Copper-Catalyzed Hydroxylation of (Hetero)aryl Halides under Mild Conditions
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The combination of Cu(acac)2 and N,N′-bis(4-hydroxyl-2,6-dimethylphenyl)oxalamide (BHMPO) provides a powerful catalytic system for hydroxylation of (hetero)aryl halides. A wide range of (hetero)aryl chlorides bearing either electron-donating or -withdrawing groups proceeded well at 130 °C, delivering the corresponding phenols and hydroxylated heteroarenes in good to excellent yields. When more reactive (hetero)aryl bromides and iodides were employed, the hydroxylation reactions completed at relatively low temperatures (80 and 60 °C, respectively) at low catalytic loadings (0.5 mol % Cu).
- Xia, Shanghua,Gan, Lu,Wang, Kailiang,Li, Zheng,Ma, Dawei
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supporting information
p. 13493 - 13496
(2016/10/31)
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- Oxidation with air by ascorbate-driven quinone redox cycling
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Transition metal-free oxidation with air at room temperature has been achieved by simply using ascorbate (vitamin C) and catalytic amounts of menadione (vitamin K3). A combination of the mentioned vitamins transforms atmospheric oxygen into hydrogen peroxide, which is able to oxidize arylboronic acids and other chemical moieties. This journal is
- Silveira-Dorta, Gastón,Monzón, Diego M.,Crisóstomo, Fernando P.,Martín, Tomás,Martín, Víctor S.,Carrillo, Romen
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supporting information
p. 7027 - 7030
(2015/04/22)
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- Hydrolysis of diazonium salts using a two-phase system (CPME and water)
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A new method for the hydrolysis of diazonium salts, without the formation of tar, was developed. A two-phase system consisting of cyclopentyl methyl ether (CPME) and water is very effective for the hydrolysis of diazonium salts. Using this solvent system, the diazonium salt prepared from 3-(4-nitrophenoxy)aniline gave 3-(4-nitrophenoxy)phenol in high yield (96%) within 20 min. The synthesized phenol is an industrially important raw material in polymer syntheses. Furthermore, the use of the present two-phase system of CPME and water successfully brought about the efficient conversions of several m-substituted anilines into the corresponding m-substituted phenols. This is the first example of hydrolysis of diazonium salts using the two-phase system (CPME and water).
- Taniguchi, Toshihide,Imoto, Mitsutaka,Takeda, Motonori,Nakai, Takeo,Mihara, Masatoshi,Iwai, Toshiyuki,Ito, Takatoshi,Mizuno, Takumi,Nomoto, Akihiro,Ogawa, Akiya
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p. 411 - 416
(2018/01/18)
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- Three-coordinate copper(I) 2-hydroxy-1,10-phenanthroline dinuclear complex catalyzed homocoupling of arylboronic acids towards biphenyls under air condition
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An efficient synthesis of biphenyls via three-coordinate planar dinuclear Cu2(ophen)2 complex catalyzed homocoupling of arylboronic acids under air condition and in the condition of alkali-free was demonstrated. Uniquely, this catalyst shows high selectivity towards biphenyls when the reaction was conducted in aqueous solution, which is significantly different from selectivity towards phenols in related Cu-catalysts. Utilization of environmentally friendly water as main solvent, reaction at room temperature and in the absence of base, cheapness, low loading and easy bulk preparation of catalyst make it potential in green synthesis of biphenyls.
- Wang, Yan-Hong,Xu, Mei-Chen,Liu, Jie,Zhang, Ling-Juan,Zhang, Xian-Ming
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p. 9598 - 9601
(2015/12/04)
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- Organic hypervalent iodine(III) catalyzed ipso-hydroxylation of aryl- and alkylboronic acids/esters
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An organo-hypervalent iodine(III) catalyzed highly efficient methodology for ipso-hydroxylation of diversely functionalized aryl- and alkylboronic acids/esters has been developed using NaIO4 as a co-oxidant. This protocol is also applicable to N-heterocyclic boronic acids and esters. Further mechanistic studies revealed that the organoboronic acid (an electron demanding moiety) is acting as a nucleophile in the presence of hypervalent iodine for hydroxylation reactions. In summary, this is the first Letter of a generalized route for organic hypervalent iodine(III) catalyzed hydroxylation of organoboronic compounds.
- Chatterjee, Nachiketa,Goswami, Avijit
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supporting information
p. 1524 - 1527
(2015/03/14)
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- Hydroxylation of aryl- and alkylboronic acids/esters mediated by iodobenzene diacetate - An avenue for using organoboronic acids/esters as nucleophiles for hydroxylation reactions
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A metal free, mild, and highly efficient methodology for ipso-hydroxylation of diversely functionalized aryl- and alkylboronic acids/esters mediated by iodobenzene diacetate (DAIB) under ambient temperature has been developed. This protocol is also applicable to N-heterocyclic boronic acids and esters. In the course of understanding the mechanism of this protocol, it is anticipated that organoboronic acid/ester, even being an electron demanding moiety, is acting as a nucleophile in the presence of DAIB for the hydroxylation reaction.
- Chatterjee, Nachiketa,Chowdhury, Hrishikesh,Sneh, Kumar,Goswami, Avijit
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supporting information
p. 172 - 174
(2015/02/02)
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- Exploration of relative chemoselectivity in the hydrodechlorination of 2-chloropyridines
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The chemoselectivity of hydrodechlorination in 2-chloropyridine derivatives possessing reduction-sensitive functionalities is examined. The reaction conditions employed tolerate a variety of functionalities illustrating highly chemoselective hydrodechlorination in the presence of nitrile, allyl, terminal olefin, and nitroamine functionalities in excellent yield. Chemoselective deprotection of carboxybenzyl ethers is illustrated in moderate yield.
- Kinarivala, Nihar,Trippier, Paul C.
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supporting information
p. 5386 - 5389
(2015/01/16)
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- Unexpected hydrazine hydrate-mediated aerobic oxidation of aryl/ heteroaryl boronic acids to phenols in ambient air
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The expedient and efficient sub-stoichimetric hydrazine hydrate-mediated aerobic hydroxylation of boronic acids that proceeds in poly(ethylene glycol) (PEG-400) has been successfully developed, providing diverse phenols in high yields. And heteroaryl boronic acids are also amenable to this protocol. the Partner Organisations 2014.
- Zhong, Yanzhen,Yuan, Linxin,Huang, Zheng,Gu, Wenchao,Shao, Ye,Han, Wei
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p. 33164 - 33167
(2014/08/18)
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- Biomimetic aerobic oxidative hydroxylation of arylboronic acids to phenols catalysed by a flavin derivative
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Flavin-catalysed oxidative hydroxylation of substituted arylboronic acids by molecular oxygen with the assistance of hydrazine or ascorbic acid resulted in phenols in high yields. This mild organocatalytic protocol is compatible with a variety of functional groups and it is alternatively usable for transformation of alkylboronic acids to alcohols. Reaction takes place also in water and fulfils criteria for a green procedure.
- Kotoucova, Hana,Strnadova, Iveta,Kovandova, Martina,Chudoba, Josef,Dvorakova, Hana,Cibulka, Radek
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supporting information
p. 2137 - 2142
(2014/03/21)
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- Aerobic photooxidative synthesis of phenols from arylboronic acids using 2-propanol as solvent
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We report a useful method for the synthesis of phenols from arylboronic acids with hydrogen peroxide generated in situ by aerobic photooxidation. This reaction uses visible-light irradiation and easily handled 2-chloroanthraquinone as an organocatalyst under mild conditions, that is, an air atmosphere and ambient pressure and temperature. Because of this method's metal- and base-free conditions, it represents an environmentally benign approach to the synthesis of phenols from arylboronic acids.
- Matsui, Keita,Ishigami, Takafumi,Yamaguchi, Tomoaki,Yamaguchi, Eiji,Tada, Norihiro,Miura, Tsuyoshi,Itoh, Akichika
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p. 2613 - 2616
(2015/01/09)
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- Structural characterization and function determination of a nonspecific carboxylate esterase from the amidohydrolase superfamily with a promiscuous ability to hydrolyze methylphosphonate esters
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The uncharacterized protein Rsp3690 from Rhodobacter sphaeroides is a member of the amidohydrolase superfamily of enzymes. In this investigation the gene for Rsp3690 was expressed in Escherichia coli and purified to homogeneity, and the three-dimensional structure was determined to a resolution of 1.8 ? The protein folds as a distorted (β/α)8-barrel, and the subunits associate as a homotetramer. The active site is localized to the C-terminal end of the β-barrel and is highlighted by the formation of a binuclear metal center with two manganese ions that are bridged by Glu-175 and hydroxide. The remaining ligands to the metal center include His-32, His-34, His-207, His-236, and Asp-302. Rsp3690 was shown to catalyze the hydrolysis of a wide variety of carboxylate esters, in addition to organophosphate and organophosphonate esters. The best carboxylate ester substrates identified for Rsp3690 included 2-naphthyl acetate (kcat/Km = 1.0 × 105 M-1 s-1), 2-naphthyl propionate (k cat/Km = 1.5 × 105 M-1 s -1), 1-naphthyl acetate (kcat/Km = 7.5 × 103 M-1 s-1), 4-methylumbelliferyl acetate (kcat/Km = 2.7 × 103 M-1 s-1), 4-nitrophenyl acetate (kcat/Km = 2.3 × 105 M-1 s-1), and 4-nitrophenyl butyrate (kcat/Km = 8.8 × 105 M -1 s-1). The best organophosphonate ester substrates included ethyl 4-nitrophenyl methylphosphonate (kcat/Km = 3.8 × 105 M-1 s-1) and isobutyl 4-nitrophenyl methylphosphonate (kcat/Km = 1.1 × 104 M-1 s-1). The (SP)-enantiomer of isobutyl 4-nitrophenyl methylphosphonate was hydrolyzed 10 times faster than the less toxic (RP)-enantiomer. The high inherent catalytic activity of Rsp3690 for the hydrolysis of the toxic enantiomer of methylphosphonate esters make this enzyme an attractive target for directed evolution investigations.
- Xiang, Dao Feng,Kumaran, Desigan,Swaminathan, Subramanyam,Raushel, Frank M.
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p. 3476 - 3485
(2014/06/23)
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- Microwave-assisted copper-catalyzed hydroxylation of aryl halides in water
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A simple and efficient protocol for microwave-assisted copper-catalyzed hydroxylation of aryl halides is developed. A variety of phenols can be obtained in moderate to excellent yields of up to 95%. Its application is performed to synthesize 2,3-dihydroxy-1,4-naphthoquinone, which displays significant anti-proliferation effect.
- Ke, Fang,Chen, Xiaole,Li, Zhengkai,Xiang, Haifeng,Zhou, Xiangge
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p. 22837 - 22840
(2013/11/19)
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- Meteorites as catalysts for prebiotic chemistry
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From outer space: Twelve meteorite specimens, representative of their major classes, catalyse the synthesis of nucleobases, carboxylic acids, aminoacids and low-molecular-weight compounds from formamide (see figure). Different chemical pathways are identified, the yields are high for a prebiotic process and the products come in rich and composite panels.
- Saladino, Raffaele,Botta, Giorgia,Delfino, Michela,Di Mauro, Ernesto
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p. 16916 - 16922
(2014/01/06)
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- Synthesis of phenols via fluoride-free oxidation of arylsilanes and arylmethoxysilanes
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Rapid, efficient methods have been developed to prepare phenols from the oxidation of arylhydrosilanes. The effects of arene substituents and fluoride promoters on this process show that while electron-deficient arenes can undergo direct oxidation from the hydrosilane, electron-rich aromatics benefit from silane activation via oxidation to the methoxysilane using homogeneous or heterogeneous transition metal catalysis. The combination of these two oxidations into a streamlined flow procedure involving minimal processing of reaction intermediates is also reported.
- Rayment, Elizabeth J.,Summerhill, Nick,Anderson, Edward A.
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experimental part
p. 7052 - 7060
(2012/10/07)
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- Efficient and selective demethylation of heteroaryl methyl ethers in the presence of aryl methyl ethers
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A new and efficient method for the demethylation of 6-membered aza-heterocyclic methyl ethers is described using lithium chloride and para-toluenesulfonic acid. This process is chemoselective for aza-heterocyclic methyl ethers in the presence of aryl methyl ethers.
- Soni, Ajay,Dutt, Akhilesh,Sattigeri, Viswajanani,Cliffe, Ian A.
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experimental part
p. 1852 - 1857
(2011/06/20)
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- Reduction of amine N-oxides by diboron reagents
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Facile reduction of alkylamino-, anilino-, and pyridyl-N-oxides can be achieved via the use of diboron reagents, predominantly bis- (pinacolato)- and in some cases bis(catecholato)diboron [(pinB)2 and (catB)2, respectively]. Reductions occur upon simply mixing the amine N oxide and the diboron reagent in a suitable solvent, at a suitable temperature. Extremely fast reductions of alkylamino- and anilino-N-oxides occur, whereas pyridyl-N-oxides undergo slower reduction. The reaction is tolerant of a variety of functionalities such as hydroxyl, thiol, and cyano groups, as well as halogens. Notably, a sensitive nucleoside N-oxide has also been reduced efficiently. The different rates with which alkylamino- and pyridyl-N-oxides are reduced has been used to perform stepwise reduction of the N,N-dioxide of (S)-(-)-nicotine. Because it was observed that (pinB)2 was unaffected by the water of hydration in amine oxides, the feasibility of using water as solvent was evaluated. These reactions also proceeded exceptionally well, giving high product yields. In constrast to the reactions with (pinB)2, triethylborane reduced alkylamino-N oxides, but pyridine N-oxide did not undergo efficient reduction even at elevated temperature. Finally, the mechanism of the reductive process by (pinB)2 has been probed by 1H and 11B NMR. (Figure presented) ; 2011 American Chemical Society.
- Kokatla, Hari Prasad,Thomson, Paul F.,Bae, Suyeal,Doddi, Venkata Ramana,Lakshman, Mahesh K.
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experimental part
p. 7842 - 7848
(2011/12/01)
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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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supporting information; experimental part
p. 5338 - 5341
(2011/10/19)
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- Lithium pipecolinate as a facile and efficient ligand for copper-catalyzed hydroxylation of aryl halides in water
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Direct hydroxylation of a wide scope of aryl halides was catalyzed by a combination of CuI and lithium pipecolinate in water with yields up to 92%.
- Jing, Linhai,Wei, Jiangtao,Zhou, Li,Huang, Zhiyong,Li, Zhengkai,Zhou, Xiangge
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supporting information; experimental part
p. 4767 - 4769
(2010/09/03)
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- Copper-catalyzed direct preparation of phenols from aryl halides
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A method for direct preparation of phenols from aryl halides using microwave heating is reported. A catalyst system comprising a simple copper salt and a diamine ligand is used, together with tripotassium phosphate as base and water as the solvent. Heating at 180 °C for 30 min allows for the conversion of a range of aryl bromides and iodides to the corresponding phenols. Aryl chlorides prove less reactive.
- Mehmood, Arshad,Leadbeater, Nicholas E.
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experimental part
p. 64 - 66
(2011/01/12)
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- Schwartz Reagents: Methods of In Situ Generation and Use
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Embodiments of the invention provide a method of using Schwartz Reagent, Cp2Zr(H)Cl, without accumulating or isolating it. Methods provide mixtures of Cp2ZrCl2, reductants that selectively reduce Cp2ZrCl2, and substrates. After reaction of Cp2ZrCl2 and the reductant, an intermediate reduction product is formed, apparently Schwartz Reagent. The in situ Schwartz Reagent then selectively reduces certain functional groups on the substrate. Substrates include tertiary amides, tertiary benzamides, aryl O-carbamates, and heteroaryl N-carbamates, which are reduced to aldehydes, benzaldehydes, aromatic alcohols, and heteroaromatics, respectively. Compared to prior methods, reagents are inexpensive and stable, reaction times are short, and reaction temperature in certain cases is conveniently room temperature. It has been estimated that using the in situ method described herein instead of synthesized or commercially obtained Schwartz Reagent provides a 50% reduction in cost.
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Page/Page column 7; 15
(2010/06/19)
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- NOVEL AROMATIC COMPOUND AND POLYARYLENE COPOLYMER HAVING NITROGEN-CONTAINING HETEROCYCLE INCLUDING SULFONIC ACID GROUP IN SIDE CHAIN
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Provided is a solid polymer electrolyte having increased heat resistance and high proton conductivity and a proton conductive membrane composed of the electrolyte. Also provided is a copolymer having a sulfonic acid group. The copolymer includes a repeating unit represented by Formula (1): (in the formula, Y denotes at least one kind of structure selected from the group consisting of —CO—, —SO2—, —SO—, —CONH—, —COO—, —(CF2)l— (l is an integer of 1 to 10), and —C(CF3)2—; W denotes at least one kind of structure selected from the group consisting of a direct bond, —CO—, —SO2—, —SO—, —CONH—, —COO—, —(CF2)l— (l is an integer of 1 to 10), —C(CF3)2—, —O—, and —S—; Z denotes a direct bond or at least one kind of structure selected from the group consisting of —(CH2)l—(l is an integer of 1 to 10), —C(CH3)2—, —O—, —S—, —CO—, and —SO2—; R30 denotes a nitrogen-containing aromatic ring having a substituent represented by —SO3H, —O(CH2)hSO3H, or —O(CF2)hSO3H (h is an integer of 1 to 12); p is an integer of 0 to 10; q is an integer of 0 to 10; r is an integer of 1 to 5; and k is an integer of 0 to 4).
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- Practical, environment-benign and atom economic KOAc-catalysed deprotection of aryl TIPS ethers under mild fluoride-free conditions
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A KOAc-catalysed, fluoride-free protocol not only effects chemoselective deprotection of phenolic TIPS ethers without affecting acetal, ketal, carbamate, O-acetyl and aliphatic silyl ethers, but also improves its atom economy by recycling the silanol byproduct.
- Wang, Bing,Sun, Hui-Xia,Chen, Bo,Sun, Zhi-Hua
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supporting information; experimental part
p. 1112 - 1114
(2010/04/23)
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