- A Hydroperoxide Method for 3,4-Xylenol Synthesis
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The aerobic oxidation reaction of 1,2-dimethyl-4-isopropylbenzene to a hydroperoxide in the presence of N-hydroxyphthalimide and its derivatives has been studied. It has been found that up to a hydrocarbon (HC) conversion of 25–30%, the selectivity for the tertiary hydroperoxide of 1,2-dimethyl-4-isopropylbenzene is over 90–95%. A method for assessing the catalytic activity of phthalimide compounds in liquid-phase oxidation reactions of 1,2-dimethyl-4-isopropylbenzene with the use of quantum-chemically calculated values for the energies of singly occupied molecular orbitals (ΔЕSOMO) has been proposed.
- Kurganova,Frolov,Koshel’,Nesterova,Shakun,Mazurin
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Read Online
- Reaction of hydroxyl radical with arenes in solution—On the importance of benzylic hydrogen abstraction
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The regioselectivity of hydroxyl radical reactions with alkylarenes was investigated using a nuclear magnetic resonance (NMR)-based methodology capable of trapping and quantifying addition and hydrogen abstraction products of the initial elementary step of the oxidation process. Abstraction products are relatively minor components of the product mixtures (15–30 mol%), depending on the magnitude of the overall rate coefficient and the number of available hydrogens. The relative reactivity of addition at a given position on the ring depends on its relation to the methyl substituents on the hydrocarbons under study. The reactivity enhancements for disubstituted and trisubstituted rings are approximately additive under the conditions of this study.
- Waggoner, Abygail R.,Abdulrahman, Yahya,Iverson, Alexis J.,Gibson, Ethan P.,Buckles, Mark A.,Poole, James S.
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- REARRANGEMENT OF DIMETHYLPHENYLACYLATES USING ZEOLITES
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The present invention relates to a Fries rearrangement of specific dimethylphenylacylates to form the desired respective hydroxyaryl ketones having two methyl groups bound to the aromatic ring. It has been found that the process is surprisingly very specific in view of the number and position of the methyl group(s) bound to the aromatic ring.
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Page/Page column 9-11
(2021/08/14)
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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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- Substrate substitution effects in the Fries rearrangement of aryl esters over zeolite catalysts
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The catalytic transformation of aryl esters to hydroxyacetophenones via Fries rearrangement over solid acids is of interest to avoid the use of corrosive and toxic Lewis and Br?nsted acids traditionally applied. Microporous zeolites are known to catalyze the reaction of simple substrates such as phenyl acetate, but their application to substituted derivatives has received limited attention. To refine structure-activity relationships, here we examine the impact of various parameters including the solvent polarity, water content, acidic properties, and framework type on the reaction scheme in the Fries rearrangement of p-tolyl acetate over common solid acids. The results confirm the importance of providing a high concentration of accessible Br?nsted acid sites, with beta zeolites exhibiting the best performance. Extension of the substrate scope by substituting methyl groups in multiple positions identifies a framework-dependent effect on the rearrangement chemistry and highlights the potential for the transformation of dimethylphenyl acetates. Kinetic studies show that the major competitive path of cleavage of the ester C-O bond usually occurs in parallel to the Fries rearrangement. The possibility of sequentially acylating the resulting phenol depends on the substrate and reaction conditions.
- Bonrath, Werner,Létinois, Ulla,Lin, Ronghe,Medlock, Jonathan,Mitchell, Sharon,Netscher, Thomas,Pérez-Ramírez, Javier,Stemmler, René T.
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p. 4282 - 4292
(2020/07/30)
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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; 0076-0078; 0085-0106
(2020/12/08)
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- Thermal Behavior Analysis of Two Synthesized Flavor Precursors of N-alkylpyrrole Derivatives
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To expand the library of pyrrole-containing flavor precursors, two new flavor precursors—methyl N-benzyl-2-methyl-5-formylpyrrole-3-carboxylate (NBMF) and methyl N-butyl-2-methyl-5-formylpyrrole-3-carboxylate (NUMF)—were synthesized by cyclization, oxidation, and alkylation reactions. Thermogravimetry (TG), differential scanning calorimeter, and pyrolysis–gas chromatography/mass spectrometry were utilized to analyze the thermal degradation behavior and thermal degradation products of NBMF and NUMF. The TG-DTG curve indicated that the maximum mass loss rates of NBMF and NUMF appear at 310 and 268°C, respectively. The largest peaks of NBMF and NUMF showed by the differential scanning calorimeter curve were 315 and 274°C, respectively. Pyrolysis–gas chromatography/mass spectrometry detected small molecule fragrance compounds appeared during thermal degradation, such as 2-methylpyrrole, 1-methylpyrrole-2-carboxylic acid methyl ester, limonene, and methyl formate. Finally, the thermal degradation mechanism of NBMF and NUMF was discussed, which provided a theoretical basis for their application in tobacco flavoring additives.
- Ai, Lvye,Liu, Mengzhen,Ji, Xiaoming,Lai, Miao,Zhao, Mingqin,Ren, Tianbao
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p. 2389 - 2397
(2019/08/01)
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- Method for synthesizing high added value xylenol through isomerization of 2,6-dimethylphenol
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The invention discloses a method for synthesizing high added value xylenol through isomerization of 2,6-dimethylphenol. The method comprises: 1, pouring a catalyst and 2,6-dimethylphenol into a reaction bottle, uniformly stirring, and carrying out a thermal insulation reaction to obtain a reaction product; 2, carrying out a hydrolysis reaction on the reaction product, carrying out standing layering, and separating to obtain a water phase and an organic phase; and 3, combining the extractant obtained by extracting the water phase and the organic phase, and sequentially carrying out washing, drying, decolorization and pressure reducing distillation treatment to obtain xylenol. According to the present invention, 2,6-dimethylphenol is subjected to methyl rearrangement isomerization under theaction of the catalyst to obtain the wide-use and high-added value xylenol including 2,5-dimethylphenol, 3,5-dimethylphenol, 2,3-dimethylphenol and 3,4-dimethylphenol, such that the low value productis converted into the high value product, the raw material and process costs are reduced, the environmental pollution is low, and the method is suitable for industrial production.
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Paragraph 0038-0140
(2019/02/08)
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- Polymer-supported eosin Y as a reusable photocatalyst for visible light mediated organic transformations
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A novel polymer-supported recyclable photocatalyst has been developed for visible light mediated oxidation reactions. The organic dye eosin Y was loaded on macroporous commercially available Amberlite IRA 900 chloride resin and exploited as a photocatalyst for visible light mediated oxidation of thioethers to sulfoxides and phenylboronic acids to phenols under open atmospheric air. Varieties of functional groups were well tolerated during oxidation. The catalyst is recyclable for six cycles without significant loss in its efficiency. Furthermore, gram-scale oxidation of sulfides to sulfoxides has been demonstrated to prove the commercial viability of the method.
- Sridhar, Arunasalam,Rangasamy, Rajmohan,Selvaraj, Mari
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p. 17974 - 17979
(2019/12/02)
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- Regioselectivity of Hydroxyl Radical Reactions with Arenes in Nonaqueous Solutions
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The regioselectivity of hydroxyl radical addition to arenes was studied using a novel analytical method capable of trapping radicals formed after the first elementary step of reaction, without alteration of the product distributions by secondary oxidation processes. Product analyses of these reactions indicate a preference for o- over p-substitution for electron donating groups, with both favored over m-addition. The observed distributions are qualitatively similar to those observed for the addition of other carbon-centered radicals, although the magnitude of the regioselectivity observed is greater for hydroxyl. The data, reproduced by high accuracy CBS-QB3 computational methods, indicate that both polar and radical stabilization effects play a role in the observed regioselectivities. The application and potential limitations of the analytical method used are discussed.
- Moores, Lee C.,Kaur, Devinder,Smith, Mathew D.,Poole, James S.
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p. 3260 - 3269
(2019/03/11)
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- Synthesis of substituted phenols via hydroxylation of arenes using hydrogen peroxide in the presence of hexaphenyloxodiphosphonium triflate
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A mild and efficient protocol for the synthesis of phenols from arenes has been developed using aqueous hydrogen peroxide as an oxidizing agent and hexaphenyloxodiphosphonium triflate as a promoter. The reactions were carried out with the simple procedure in EtOH-H2O at room temperature in short reaction times.
- Khodaei, Mohammad Mehdi,Alizadeh, Abdolhamid,Hezarkhani, Hadis Afshar
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p. 878 - 882
(2018/11/06)
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- Liquid phase hydrodeoxygenation of anisole, 4-ethylphenol and benzofuran using Ni, Ru and Pd supported on USY zeolite
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The objective of this work is to understand the role of metals on the hydrodeoxygenation (HDO) reaction pathways of three bio-oil model compounds. Ni, Ru and Pd were impregnated on USY zeolite, and the catalysts were characterized to determine metal reduction profile, surface concentration and nanoparticle size. Ru-USY and Pd-USY were completely reduced at a temperature below 450 °C, but Ni-USY still contained surface metal oxides after reduction. There was no indication of strong interactions between the metals and USY support. Anisole, 4-ethylphenol and benzofuran were used as bio-oil model compounds, in order to determine the effects of each metal on deoxygenation of methoxy-, phenol and furan functional groups, respectively. Pd-USY was the most effective HDO catalyst, exhibiting the highest turnover frequency for HDO of all three model compounds, in addition to and high selectivity to deoxygenated products. A mechanism was proposed for each model compound, and the kinetics of hydrogenation, dehydration, C–C coupling and ring-opening reactions were determined.
- Gamliel, David P.,Karakalos, Stavros,Valla, Julia A.
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- Tuning the Reactivity of Peroxo Anhydrides for Aromatic C-H Bond Oxidation
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Phenol moieties are key structural motifs in many areas of chemical research from polymers to pharmaceuticals. Herein, we report on the design and use of a structurally demanding cyclic peroxide (spiro[bicyclo[2.2.1]heptane-2,4′-[1,2]dioxolane]-3′,5′-dione, P4) for the direct hydroxylation of aromatic substrates. The new peroxide benefits from high thermal stability and can be synthesized from readily available starting materials. The aromatic C-H oxidation using P4 exhibits generally good yields (up to 96%) and appreciable regioselectivities.
- Pilevar, Afsaneh,Hosseini, Abolfazl,?ekutor, Marina,Hausmann, Heike,Becker, Jonathan,Turke, Kevin,Schreiner, Peter R.
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p. 10070 - 10079
(2018/09/06)
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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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- 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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- A Ni-Mg-Al layered triple hydroxide-supported Pd catalyst for heterogeneous acceptorless dehydrogenative aromatization
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In the presence of a Ni-Mg-Al layered triple hydroxide-supported Pd catalyst, the acceptorless dehydrogenative aromatization of a wide range of cyclohexanols/cyclohexanones and cyclohexylamines efficiently proceeded to give the corresponding phenols and anilines, respectively, in moderate to high yields with the liberation of molecular hydrogen.
- Jin, Xiongjie,Taniguchi, Kento,Yamaguchi, Kazuya,Nozaki, Kyoko,Mizuno, Noritaka
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supporting information
p. 5267 - 5270
(2017/07/10)
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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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p. 12260 - 12263
(2017/09/06)
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- Process for the preparation of phenols
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The present invention relates to a process for the preparation of phenols in which an aryldiazonium salt, which is prepared by the diazotization of a corresponding aromatic, primary amine, by heating in a mixture comprising hot water, a mineral acid and an organic solvent, is decomposed, where the organic solvent comprises a ketone of the formula (I) R1C(O)R2, in which R1 and R2, independently of one another, are (C1-C5)-alkyl and R1 and R2 together have at least four carbon atoms, where the aromatic primary amine is aniline or a substituted aniline which comprises at least one further substituent which is selected from: alkyl, alkenyl, alkynyl, halogen, haloalkyl, cycloalkyl, heteroalkyl, carboxyl, cyano, alkoxy and ester, and where essentially no copper salts are present in the mixture.
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Paragraph 0029
(2017/01/12)
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- Au-Pd alloy nanoparticles supported on layered double hydroxide for heterogeneously catalyzed aerobic oxidative dehydrogenation of cyclohexanols and cyclohexanones to phenols
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Phenol, an important industrial chemical, is widely produced using the well-developed cumene process. However, demand for the development of a novel alternative method for synthesizing phenol from benzene has been increasing. Herein, we report a novel system for the synthesis of phenols through aerobic oxidative dehydrogenation of cyclohexanols and cyclohexanones, including ketone-alcohol (KA) oil, catalyzed by Mg-Al-layered double hydroxide (LDH)-supported Au-Pd alloy nanoparticles (Au-Pd/LDH). Alloying of Au and Pd and basicity of LDH are key factors in achieving the present transformation. Although monometallic Au/LDH, Pd/LDH, and their physical mixture showed almost no catalytic activity, Au-Pd/LDH exhibited markedly high catalytic activity for the dehydrogenative phenol production. Mechanistic studies showed that β-H elimination from Pd-enolate species is accelerated by Au species, likely via electronic ligand effects. Moreover, the effect of supports was critical; despite the high catalytic performance of Au-Pd/LDH, Au-Pd bimetallic nanoparticles supported on Al2O3, TiO2, MgO, and CeO2 were ineffective. Thus, the basicity of LDH plays a deterministic role in the present dehydrogenation possibly through its assistance in the deprotonation steps. The synthetic scope of the Au-Pd/LDH-catalyzed system was very broad; various substituted cyclohexanols and cyclohexanones were efficiently converted into the corresponding phenols, and N-substituted anilines were synthesized from cyclohexanones and amines. In addition, the observed catalysis was truly heterogeneous, and Au-Pd/LDH could be reused without substantial loss of its high performance. The present transformation is scalable, utilizes O2 in air as the terminal oxidant, and generates water as the only by-product, highlighting the potential practical utility and environmentally benign nature of the present transformation. Dehydrogenative aromatization of cyclohexanols proceeds through (1) oxidation of cyclohexanols to cyclohexanones; (2) dehydrogenation of cyclohexanones to cyclohexenones; and (3) disproportionation of cyclohexenones to afford the desired phenols. In the present Au-Pd/LDH-catalyzed transformation, the oxidation of the Pd-H species is included in the rate-determining step.
- Jin, Xiongjie,Taniguchi, Kento,Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 5371 - 5383
(2016/07/29)
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- Improved oxidation of aromatic and aliphatic hydrocarbons using rate enhancing variants of P450Bm3 in combination with decoy molecules
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Enzyme performance can be improved using decoy molecules or engineered variants to accelerate the activity without affecting selectivity. Here we combine a rate accelerator variant of cytochrome P450Bm3 with decoy molecules to enhance the oxidation activity of a range of small organic molecules. This combined approach offers superior biocatalytic efficiency without modifying the product distribution.
- Munday, Samuel D.,Shoji, Osami,Watanabe, Yoshihito,Wong, Luet-Lok,Bell, Stephen G.
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supporting information
p. 1036 - 1039
(2016/01/16)
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- Study of gas phase m-cresol alkylation with methanol on solid acid catalysts
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The gas-phase alkylation of m-cresol with methanol was studied at 523 K on Al-MCM-41 and zeolites ZnY, HBEA, HZSM5 and HMCM22. The acidity was determined by ammonia TPD and FTIR of adsorbed pyridine. On acid sites of moderate strength (Al-MCM-41), initially the O-alkylation rate was higher than the C-alkylation rate. In contrast, formation of dimethylphenols by C-alkylation was highly favored on ZnY and HMCM22 which have both strong acidity although different nature; Lewis (ZnY) and Bronsted and Lewis (HMCM22). High selectivity of 2,5-DMP was observed on HZSM5, probably due to diffusional constraint. All catalysts, except Al-MCM-41, showed deactivation by coke formation.
- Acevedo,Bedogni,Okulik,Padr
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p. 1946 - 1954
(2015/02/19)
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- CYCLIC PEROXIDE OXIDATION OF AROMATIC COMPOUND PRODUCTION AND USE THEREOF
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The present invention provides a method for converting an aromatic hydrocarbon to a phenol by providing an aromatic hydrocarbon comprising one or more aromatic C-H bonds and one or more activated C-H bonds in a solvent; adding a phthaloyl peroxide to the solvent; converting the phthaloyl peroxide to a di-radical; contacting the di-radical with the one or more aromatic C-H bonds; oxidizing selectively one of the one or more aromatic C-H bonds in preference to the one or more activated C-H bonds; adding a hydroxyl group to the one of the one or more aromatic C-H bonds to form one or more phenols; and purifying the one or more phenols.
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Page/Page column 9; 10
(2014/10/15)
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- Base-promoted, mild and highly efficient conversion of arylboronic acids into phenols with tert-butyl hydroperoxide
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A mild and efficient protocol for the synthesis of phenols from arylboronic acids has been developed by using tert-butyl hydroperoxide with base as promoter. The corresponding phenols were obtained in good to excellent yields within several minutes. Georg Thieme Verlag Stuttgart New York.
- Guo, Shengmei,Lu, Lin,Cai, Hu
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p. 1712 - 1714
(2013/09/02)
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- Highly efficient and selective deprotection method for prenyl, geranyl, and phytyl ethers and esters using borontrifluoride-etherate
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An efficient, simple, and practical method has been developed for the deprotection of prenyl, geranyl, and phytyl ethers and esters of aromatic and aliphatic compounds using borontrifluoride-etherate (BF3· OEt2) at room temperature in good to excellent yields for the first time. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file. Copyright Taylor & Francis Group, LLC.
- Narender,Venkateswarlu,Madhur,Reddy, K. Papi
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- Metal-free oxidation of aromatic carbon-hydrogen bonds through a reverse-rebound mechanism
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Methods for carbon-hydrogen (C-H) bond oxidation have a fundamental role in synthetic organic chemistry, providing functionality that is required in the final target molecule or facilitating subsequent chemical transformations. Several approaches to oxidizing aliphatic C-H bonds have been described, drastically simplifying the synthesis of complex molecules. However, the selective oxidation of aromatic C-H bonds under mild conditions, especially in the context of substituted arenes with diverse functional groups, remains a challenge. The direct hydroxylation of arenes was initially achieved through the use of strong Bronsted or Lewis acids to mediate electrophilic aromatic substitution reactions with super-stoichiometric equivalents of oxidants, significantly limiting the scope of the reaction. Because the products of these reactions are more reactive than the starting materials, over-oxidation is frequently a competitive process. Transition-metal-catalysed C-H oxidation of arenes with or without directing groups has been developed, improving on the acid-mediated process; however, precious metals are required. Here we demonstrate that phthaloyl peroxide functions as a selective oxidant for the transformation of arenes to phenols under mild conditions. Although the reaction proceeds through a radical mechanism, aromatic C-H bonds are selectively oxidized in preference to activated-H bonds. Notably, a wide array of functional groups are compatible with this reaction, and this method is therefore well suited for late-stage transformations of advanced synthetic intermediates. Quantum mechanical calculations indicate that this transformation proceeds through a novel addition-abstraction mechanism, a kind of 'reverse-rebound' mechanism as distinct from the common oxygen-rebound mechanism observed for metal-oxo oxidants. These calculations also identify the origins of the experimentally observed aryl selectivity.
- Yuan, Changxia,Liang, Yong,Hernandez, Taylor,Berriochoa, Adrian,Houk, Kendall N.,Siegel, Dionicio
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p. 192 - 196
(2013/08/23)
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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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- 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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- 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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- Sulfoximines: A reusable directing group for chemo-and regioselective ortho C-H oxidation of arenes
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Sulfoximines direct: A new protocol for the chemo-and regioselective ortho C-H acetoxylation of arenes in N-benzoylated sulfoximines is reported. The sulfoximine directing group is easily detached from the C-H oxidation product through acid-promoted hydrolysis, isolated, and reused (see scheme). The meta-substituted phenols are synthesized following this strategy and the stereointegrity of the sulfoximine is preserved in this transformation. C(sp3)-H acetoxylation of the methyl group is also demonstrated.
- Yadav, M. Ramu,Rit, Raja K.,Sahoo, Akhila K.
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supporting information; experimental part
p. 5541 - 5545
(2012/06/01)
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- One-pot synthesis of phenols by hydroxylation of aromatics with hydroxylamine
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In this study, a new approach for one-pot synthesis of phenols is presented, i.e., benzene, ethylbenzene, and xylene were hydroxylated with hydroxylamine to give the corresponding phenols in good yield using molybdenum as a key catalyst.
- Zhang, Dongsheng,Gao, Liya,Xue, Wei,Zhao, Xinqiang,Wang, Shufang,Wang, Yanji
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scheme or table
p. 369 - 371
(2012/06/01)
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- Synthesis, structural properties, and catalytic behavior of Cu-BTC and mixed-linker Cu-BTC-PyDC in the oxidation of benzene derivatives
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Mixed-linker metal-organic frameworks based on the Cu-BTC structure have been synthesized in which the benzene-1,3,5-tricarboxylate (BTC) linkers have been partially replaced by pyridine-3,5-dicarboxylate (PyDC). X-ray-based techniques (powder XRD and XAS), thermal analysis, and infrared spectroscopy proved that a desired amount of PyDC (up to 50%) can be incorporated without changing significantly the crystal structure. The pyridine unit can be seen as a defect site in the local coordination environment of the dimeric copper units, which is significantly altering their electronic structure and the catalytic properties. Both Cu-BTC and the mixed Cu-BTC-PyDCs catalyze the demanding direct hydroxylation of toluene both in acetonitrile and in neat substrate. Different selectivity toward the desired ortho- and para-cresol and other oxidation products (benzaldehyde, benzyl alcohol, methylbenzoquinone) was observed for Cu-BTC and the Cu-BTC-PyDCs, respectively. Leaching tests and comparison with homogeneously dissolved Cu catalysts indicate mainly a heterogeneous reaction pathway.
- Marx, Stefan,Kleist, Wolfgang,Baiker, Alfons
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experimental part
p. 76 - 87
(2011/08/04)
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- CuI-nanoparticles-catalyzed selective synthesis of phenols, anilines, and thiophenols from aryl halides in aqueous solution
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CuI-nanoparticles-catalyzed selective synthesis of phenols, anilines, and thiophenols from aryl halides was developed in the absence of both ligands and organic solvents. Anilines were formed selectively with ammonia competing with hydroxylation and thiophenols were generated selectively with sulfur powder after subsequent reduction competing with hydroxylation and amination.
- Xu, Hua-Jian,Liang, Yu-Feng,Cai, Zhen-Ya,Qi, Hong-Xia,Yang, Chun-Yan,Feng, Yi-Si
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supporting information; experimental part
p. 2296 - 2300
(2011/06/17)
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- The balance of acid, basic and redox sites in Mg/Me-mixed oxides: The effect on catalytic performance in the gas-phase alkylation of m-cresol with methanol
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The reactivity of Mg/Me-mixed oxides (Me = Fe, Cr, Al) in m-cresol gas-phase methylation with methanol was studied, with the aim of finding relationships between catalytic performance and surface/bulk features. All systems exhibit similar surface properties (basically due to the presence of basic and Lewis-type acid sites), but the presence of extra cations in the MgO framework affects greatly the products obtained in the mentioned catalytic reaction, depending on the possible co-presence of redox capacity. In particular, (i) the Mg/Al/O system, characterized by no redox capacity, shows catalytic behaviour quite similar to that of conventional Bronsted-type acid catalysts, though with the advantage of exhibiting almost no deactivation during use (a rather common problem for acid catalysts activating methanol for phenol attack); (ii) the Mg/Cr/O catalyst shows a reactivity typical of a basic catalyst, with high chemo- and regio-selectivity and the favoured formation of 2,5-dimethylphenol; (iii) the Mg/Fe/O system presents a catalytic behaviour closer to that of Mg/Cr/O, if referred to the distribution of phenolic products, but it also exhibits a better activity in methanol dehydrogenation to formaldehyde (that is the true electrophilic reactant for m-cresol ring methylation), and in the decomposition of formaldehyde into light compounds. This behaviour causes a poor selectivity to dimethylphenols with respect to converted methanol, whereas the selectivity with respect to converted m-cresol is not different from that shown by Mg/Cr/O system.
- Crocella,Cerrato,Magnacca,Morterra,Cavani,Cocchi,Passeri,Scagliarini,Flego,Perego
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body text
p. 125 - 135
(2010/06/12)
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- Copper-catalyzed hydroxylation of aryl halides with tetrabutylammonium hydroxide: Synthesis of substituted phenols and alkyl aryl ethers
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The selective hydroxylation of aryl iodides and aryl bromides with tetrabutylammonium hydroxide pentahydrate is described. For this, the combination of copper(I) iodide and 8-hydroxyquinaldine at 70-130C in a mixture of dimethyl sulfoxide and water (2:3) is used. The resultant phenols can be readily reacted with alkyl and allyl halides in situ to provide the corresponding alkyl or allyl aryl ethers in high yields. The reactions are simple, general, and efficient, affording substituted phenols and alkyl aryl ethers under aerobic conditions
- Paul, Rajesh,Ali, Md Ashif,Punniyamurthy, Tharmalingam
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supporting information; experimental part
p. 4268 - 4272
(2011/02/25)
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- Reaction of atomic carbon with isomeric cresols
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Reaction of atomic carbon with isomeric cresols generates methyltropones and xylenols. Methyltropone to xylenol ratio was found to be highest for m-cresol and lowest for p-cresol. Stability of singlet carbenes produced after insertion of atomic carbon int
- Soekmen, Ilkay,Ece, Abdulilah,Duez, Buelent,Sevin, Fatma
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experimental part
p. 650 - 653
(2010/06/16)
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- Electrochemically induced transformation of 4-halomethyl-4-methylcyclohexa- 2,5-dien-1-ones into 3,4-dimethylphenol
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Electrochemical behavior of 4-halomethyl-4-methylcyclohexa-2,5-dien-1-ones and 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-one was studied. Reductive dehalogenation of cyclohexa-2,5-dien-1-ones having a halogen atom at the neopentyl-like carbon atom give
- Gavrilova,Moiseeva,Beloglazkina,Gavrilov,Zyk
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experimental part
p. 264 - 268
(2009/08/14)
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- Process for the preparation of substituted phenols
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A substituted phenolic compound is prepared by oxidizing a substituted diarylethane compound with oxygen in the presence of a nitrogen-containing cyclic compound, and treating the oxidized product with an acid. The nitrogen-containing cyclic compound includes, as a constituent of its ring, a skeleton represented by following Formula (I): wherein X is oxygen atom or an -OR group, where R is hydrogen atom or a hydroxyl-protecting group. The substituted diarylethane compound is represented by following Formula (1): wherein each of Ring Ar1 and Ring Ar2 is independently a monocyclic or polycyclic aromatic carbocyclic ring; Y1 is an electron-donating group; Y2 is an electron-withdrawing group; "p" is an integer of 1 or more; and "q" is an integer of 0 or more. The substituted phenolic compound is represented by following Formula (2): wherein Ring Ar1, Y1, and "p" are as defined above.
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Page/Page column 14
(2008/12/08)
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- Selective one-pot synthesis of various phenols from diarylethanes
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Various substituted phenols were selectively synthesized by a one-pot reaction through the NHPI-catalyzed aerobic oxidation of 1,1-diarylethanes followed by treatment with dilute sulfuric acid. The Royal Society of Chemistry.
- Nakamura, Ryota,Obora, Yasushi,Ishii, Yasutaka
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supporting information; experimental part
p. 3417 - 3419
(2009/02/05)
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- AlCl3·6H2O/KI/CH3CN/H 2O: An efficient and versatile system for chemoselective C-O bond cleavage and formation of halides and carbonyl compounds from alcohols in hydrated media
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AlCl3·6H2O/KI/CH3CN/H 2O, an efficient and versatile system, cleaves the C-O bonds of esters, acetals, ethers, and oxathiolanes to the corresponding acids, alcohols, and carbonyl compounds chemoselectively at 80°C in hydrated media with good yields. This system also converts the alcohols (primary/secondary) to halides and oxidizes the alcohols (primary/secondary) to the corresponding carbonyl compounds in the presence of DMSO. Copyright Taylor & Francis Group, LLC.
- Gogoi, Pranjal,Konwar, Dilip,Sharma, Saikat Das,Gogoi, Prodip Kumar
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p. 1259 - 1264
(2007/10/03)
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- Asymmetric ring-closing metathesis reactions involving achiral and meso substrates
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A composition and method for the catalytic conversion of a racemic mixture of dienes to a cyclic olefin by a ring-closing metathesis (RCM) reaction are disclosed. The composition, a transition metal complex with an M═C reaction site, contains a bidentate dialkoxide of at least 80% optical purity. Because the M═C reaction site is of a sufficient shape specificity, conferred in part by the dialkoxide of sufficient rigidity and a M═N—R1site, reacting the composition with a mixture of two enantiomeric dienes results in an olefin metathesis product that has at least a 50% enantiomeric excess of one enantiomer in the mixture. A method is also provided for reacting a composition with a racemic diene mixture to generate a metathesis product that has an enantiomeric excess of at least 50%. Methods are also provided for catalytic enantioselective desymmetrization. One method involves an olefin metathesis reaction with a molecular substrate having a plane of symmetry to form a product free of a plane of symmetry. Another method provides a desymmetrization reaction to occur in the absence of solvent. A method for producing quaternary carbon centers through a desymmetrization reaction is also described.
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Page column 25-26
(2010/01/30)
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- Microwave assisted selective cleavage of sulfonates and sulfonamides in dry media
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A simple and efficient method for the cleavage of Sulfonates and Sulfonamides has been achieved for the first time under microwave irradiation conditions using KF-Al2O3.
- Sabitha, Gowravaram,Abraham, Sunny,Reddy, B. V. Subba,Yadav
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p. 1745 - 1746
(2007/10/03)
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- Reaction of Resorcinol with α,β-Unsaturated Ketones
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Products of the acid-catalyzed reaction of resorcinol with α,β-unsaturated ketones have been found to fall into two classes. The first type of product is illustrated by 4-(3,4-dihydro-7-hydroxy-2,4,4-trimethyl-2H-1-benzopyran-2-yl)-1,3-benzenediol, 1, formed in 91% yield by the reaction of resorcinol with 4-methyl-3-penten-2-one (mesityl oxide). The second type of product is illustrated by (C2-symmetric) 2,2′-spirobi(7-hydroxy-4,4-dimethylchroman), 4, formed in 85% yield by the reaction of resorcinol with 2,6-dimethyl-2,5-heptadien-4-one (phorone). A number of examples of reactions leading, in quite good yields, to products analogous to 1 are presented, as well as some reactions that fail. Flavan 1 is identical to the compound formed by the acid-catalyzed reaction of acetone with excess resorcinol. Compound 1 and a steroidal analogue of 1 have been found to be fluorescent.
- Livant,Xu, Weizheng
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p. 636 - 641
(2007/10/03)
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- Cyclization of 2,6-Diones over H-ZSM-5: One-pot Synthesis of Dimethylphenols and Substituted α,β-Unsaturated Cyclohexenones
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2,6-Diones on treatment with zeolite H-ZSM-5 yield dimethylphenols (DMPs) or α,β-unsaturated cyclohexenones.
- Reddy, P. Veera,Prakash, Adekkanattu M.,Chakrabarty, Dipak K.,Bhat, Sujata V.
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p. 306 - 307
(2007/10/03)
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- Hydrolysis of aryl orthocarbonates by general acid catalyzed and spontaneous processes. Characterization of the water reaction of (ArO)3COAr′ and (ArO)3CN3
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Twenty-four aryl orthocarbonates of formula (Aro)4C, (ArO)2C(OAr′)2, or (ArO)3COAr′ have been made by coupling of the copper phenoxides with carbon disulfide, and their hydrolyses have been examined in 60% water-40% acetonitrile (I = 1.00 M, KCl) at 70.0 °C. Their hydrolysis by general acid catalyzed and, in the case of (ArO)3COAr′ when Ar′ = p-nitrophenyl and p-cyanophenyl, spontaneous processes yields aryl carbonates. The initial, rate-determining event for both processes is the cleavage of the bond between the central carbon and the least basic phenoxy group: with mixed orthocarbonates of phenols differing in pK by 6H4O)3C-O-P-C6H 4NO2 and (X-C6H4O)3C-O-p-C6H4CN where the σ value of X varies from -0.23 to 0.22 are 4-10 times slower than reactions of p-nitrophenyl tetrahydropyrans reported in the literature and give rise to nonlinear Hammett plots. However, plots against the pKa of X-C6H4OH are linear, and the derived β(reaction center) values indicate substantial buildup of positive charge on the central carbon atom. A similar plot is obtained for the spontaneous reactions of five azides (XC6H4O)3CN3 for which common ion inhibition experiments have been performed. The derived selectivities (M-1) of the tris(aryloxy)carbenium ion intermediates between azide ion and water vary from 8.5 × 103 to 6.6 × 103 as the σ value of X changes from -0.28 to 0.06. The lifetime of the tris(aryloxy)carbenium ion intermediates in water is therefore likely to be >10-6 s. The slow formation and slow hydrolysis of tris(aryloxy)carbenium ions suggests that (in the formation direction) development of conjugative stabilization lags behind carbon-oxygen bond cleavage and (in the hydrolysis direction) precedes carbon-oxygen bond formation. The stereochemistry of tetraaryl orthocarbonates immediately suggests reasons why this should be so.
- Kandanarachchi, Pramod,Sinnott, Michael L.
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p. 5592 - 5600
(2007/10/02)
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- Hydrolysis of orthocarbonates. Evidence for charge imbalance in the transition state for the general acid catalyzed process
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Catalytic constants have been measured for the hydrolysis of a range of aryl orthocarbonates, in which both the leaving group and trioxocarbenium ion moiety have been systematically varied, by neutral carboxylic acids (trichloroacetic, difluoroacetic, dichloroacetic, malonic, chloroacetic, and acetic) at 70.0°C in 60% water-40% acetonitrile, I = 1.0 M (KCI). Curvature cannot be detected in Br?nsted plots involving carboxylic acids only, but inclusion of the point for H3O+ suggests downward curvature (i.e. px ≥ 0). β1g Plots are curved downward (i.e. py′ = -?β1g/?pK1g > 0). Substitutent effects in the tris(aryloxy)carbenium ion fragment were quantitated by use of the experimental aqueous pKa alues of the phenol (pKrc), rather than Hammett σ values, since this gave better correlations for the spontaneous reactions (Kandanarachchi, P.; Sinnott, M. L. J. Am. Chem. Soc., preceding paper in this issue). Cross coefficients are large and not constant: pxy′ (measured as ?α/?pK1g rather than -?β1g/?pKHA) varies from 0.26 for (PhO)3C+ to 0.16 for (PMeOC6H4O)3C+. Likewise,pxy (measured as -?α/?pKrc rather than -?βrc/?pKHA) experiences large changes with the leaving group pK. Data to estimate pyy′ (?βrc/?pK1g) are more limited, but it too changes with the pKa of the catalyzing acid. These data indicate that a two-dimensional More O'Ferrall-Jencks diagram, with one axis representing both C-O cleavage and the ability of substituents in the tris(aryloxy)carbenium ion moiety to sense positive charge development, is inadequate to represent this reaction: separate axes are required for carbon-oxygen bond cleavage and development of carbon-oxygen double-bond character.
- Kandanarachchi, Pramod,Sinnott, Michael L.
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p. 5601 - 5606
(2007/10/02)
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- Active Site Dynamics of Xylene Hydroxylation by Cytochrome P-450 As Revealed by Kinetic Deuterium Isotope Effects
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The cytochrome P-450 catalyzed hydroxylation of o- and p-xylene and five deuterated derivatives of each has been investigated using phenobarbital-induced rat liver microsomes.All possible monohydroxylation products were observed but benzylic hydroxylation predominated strongly (88-96percent).H/D discrimination was strongest when both isotopes were located on the same methyl gorup, less when they were located in different methyl groups on the same xylene molecule, and least when they were located in methyl groups on different molecules.Benzylic hydroxylation is subject to a large intrinsic (intramolecular) deuterium isotope effect (CH3/CD3=7.5-9.5), comprised of a large primary component (5.3-7.8) and a large normal α-secondary component (1.09-1.19).These isotope effects suggest a transition state for benzylic H-abstraction that is linear and symmetrical with substantial rehybridization toward planarity at the benzylic carbon and little residual C-H bond order remaining.In contrast aromatic hydroxylation of o- and p-xylene shows a small inverse α-secondary isotope effect (0.83-0.94).The D(V/K) isotope effect observed for benzylic hydroxylation in intermolecular competitions (ca. 1.9-2.3 for d0/d6 substrate mixtures) is substantially reduced by commitment to catalysis, with Cf=(kH+kr)k-1=3.6 for p-xylene and 5.9 for o-xylene.These results suggest a dynamic picture of catalysis with the following relative rates: methyl group rotation > substrate-orientation within the Michaelis complex (i.e. isotopically sensitive branching to different products) > product formation (i.e. commitment to catalysis) > substrate dissociation prior to hydroxylation.
- Hanzlik, Robert P.,Ling, Kah-Hiing John
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p. 9363 - 9370
(2007/10/02)
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- Process for the preparation of 2,3-dimethylphenol and of 3,4-dimethylphenol
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In a process for the preparation of mixtures of 2,3-dimethylphenol and 3,4-dimethylphenol a mixture of 2,3-dimethyl-bromobenzene and 3,4-dimethyl-bromobenzene is hydrolized in an aqueous alkaline solution in the presence of a copper compound catalyst of the formula: R represents --O or --OH or a residue of an inorganic or of an organic acid; n is 1 or 2; and m is 0, 1 or 2; the reaction being carried out at a temperature in the range between 200° and 300° C.
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