- Increasing the steric hindrance around the catalytic core of a self-assembled imine-based non-heme iron catalyst for C-H oxidation
-
Sterically hindered imine-based non-heme complexes4and5rapidly self-assemble in acetonitrile at 25 °C, when the corresponding building blocks are added in solution in the proper ratios. Such complexes are investigated as catalysts for the H2O2oxidation of a series of substrates in order to ascertain the role and the importance of the ligand steric hindrance on the action of the catalytic core1, previously shown to be an efficient catalyst for aliphatic and aromatic C-H bond oxidation. The study reveals a modest dependence of the output of the oxidation reactions on the presence of bulky substituents in the backbone of the catalyst, both in terms of activity and selectivity. This result supports a previously hypothesized catalytic mechanism, which is based on the hemi-lability of the metal complex. In the active form of the catalyst, one of the pyridine arms temporarily leaves the iron centre, freeing up a lot of room for the access of the substrate.
- Frateloreto, Federico,Capocasa, Giorgio,Olivo, Giorgio,Abdel Hady, Karim,Sappino, Carla,Di Berto Mancini, Marika,Levi Mortera, Stefano,Lanzalunga, Osvaldo,Di Stefano, Stefano
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p. 537 - 542
(2021/02/09)
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- A mild and practical method for deprotection of aryl methyl/benzyl/allyl ethers with HPPh2andtBuOK
-
A general method for the demethylation, debenzylation, and deallylation of aryl ethers using HPPh2andtBuOK is reported. The reaction features mild and metal-free reaction conditions, broad substrate scope, good functional group compatibility, and high chemical selectivity towards aryl ethers over aliphatic structures. Notably, this approach is competent to selectively deprotect the allyl or benzyl group, making it a general and practical method in organic synthesis.
- Pan, Wenjing,Li, Chenchen,Zhu, Haoyin,Li, Fangfang,Li, Tao,Zhao, Wanxiang
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p. 7633 - 7640
(2021/09/22)
-
- Development of a green and sustainable manufacturing process for gefapixant citrate (MK-7264) Part 2: Development of a robust process for phenol synthesis
-
Various synthetic routes to 2-isopropyl-4-methoxyphenol 3, the phenol core of Gefapixant citrate (MK-7264), are described, which provide better alternatives to the initial four-step supply route. These new routes include a coumarin fragmentation approach in flow, a rhenium-catalyzed isopropylation of mequinol, and a bromination/methoxylation of 2-isopropylphenol. After exploring several approaches, a robust two-step process for the preparation of 3 from the commodity starting material 2-isopropylphenol was developed. The optimized route employs a highly regioselective bromination. After isolating the bromophenol DABCO cocrystal, a copper-catalyzed methoxylation delivers 3 in high yield. This route is successfully demonstrated at the plant scale with low process mass intensity and cost.
- Peng, Feng,Humphrey, Guy R.,Maloney, Kevin M.,Lehnherr, Dan,Weisel, Mark,Lévesque, Francois,Naber, John R.,Brunskill, Andrew P.J.,Larpent, Patrick,Zhang, Si-Wei,Lee, Alfred Y.,Arvary, Rebecca A.,Lee, Claire H.,Bishara, Daniel,Narsimhan, Karthik,Sirota, Eric,Whittington, Michael
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p. 2453 - 2461
(2020/11/18)
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- Benzene Hydroxylation by Bioinspired Copper(II) Complexes: Coordination Geometry versus Reactivity
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A series of bioinspired copper(II) complexes of N4-tripodal and sterically crowded diazepane-based ligands have been investigated as catalysts for functionalization of the aromatic C-H bond. The tripodal-ligand-based complexes exhibited distorted trigonal-bipyramidal (TBP) geometry (τ, 0.70) around the copper(II) center; however, diazepane-ligand-based complexes adopted square-pyramidal (SP) geometry (τ, 0.037). The Cu-NPy bonds (2.003-2.096 ?) are almost identical and shorter than Cu-Namine bonds (2.01-2.148 ?). Also, their Cu-O (Cu-Owater, 1.988 ? Cu-Otriflate, 2.33 ?) bond distances are slightly varied. All of the complexes exhibited Cu2+ → Cu+ redox couples in acetonitrile, where the redox potentials of TBP-based complexes (-0.251 to -0.383 V) are higher than those of SP-based complexes (-0.450 to -0.527 V). The d-d bands around 582-757 nm and axial patterns of electron paramagnetic resonance spectra [g∥, 2.200-2.251; A∥, (146-166) × 10-4 cm-1] of the complexes suggest the existence of five-coordination geometry. The bonding parameters showed K∥ > K∥ for all complexes, corresponding to out-of-plane πbonding. The complexes catalyzed direct hydroxylation of benzene using 30% H2O2 and afforded phenol exclusively. The complexes with TBP geometry exhibited the highest amount of phenol formation (37%) with selectivity (98%) superior to that of diazepane-based complexes (29%), which preferred to adopt SP-based geometry. Hydroxylation of benzene likely proceeded via a CuII-OOH key intermediate, and its formation has been established by electrospray ionization mass spectrometry, vibrational, and electronic spectra. Their formation constants have been calculated as (2.54-11.85) × 10-2 s-1 from the appearance of an O (π?σ) → Cu ligand-to-metal charge-transfer transition around 370-390 nm. The kinetic isotope effect (KIE) experiments showed values of 0.97-1.12 for all complexes, which further supports the crucial role of Cu-OOH in catalysis. The 18O-labeling studies using H218O2 showed a 92% incorporation of 18O into phenol, which confirms H2O2 as the key oxygen supplier. Overall, the coordination geometry of the complexes strongly influenced the catalytic efficiencies. The geometry of one of the CuII-OOH intermediates has been optimized by the density functional theory method, and its calculated electronic and vibrational spectra are almost similar to the experimentally observed values.
- Anandababu, Karunanithi,Mayilmurugan, Ramasamy,Muthuramalingam, Sethuraman,Velusamy, Marappan
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p. 5918 - 5928
(2020/04/20)
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- Thermal Stability Study of 4-tert-Butylphenol
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Abstract: The thermal stability of 4-tert-butylphenol has been studied in the temperature range of 673–738?K, the components of the thermolysis reaction mixture have been identified, a kinetic model of the process has been proposed, and the rate constants and parameters of the Arrhenius equation have been calculated for all of the reactions considered. The predominant role of 4-tert-butylphenol isomerization transformations has been established. Information on the 4-tert-butylphenol thermal stability facilitates to a more substantiated approach to its use as an additive that increases the oxidative stability of fuels and lubricants, as well as an antioxidant for polymer compositions.
- Shakun,Nesterova,Naumkin
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p. 120 - 127
(2019/04/27)
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- Direct hydroxylation of benzene and aromatics with H2O2 catalyzed by a self-assembled iron complex: Evidence for a metal-based mechanism
-
An iminopyridine Fe(ii) complex, easily prepared in situ by self-assembly of cheap and commercially available starting materials (2-picolylaldehyde, 2-picolylamine, and Fe(OTf)2 in a 2 : 2 : 1 ratio), is shown to be an effective catalyst for the direct hydroxylation of aromatic rings with H2O2 under mild conditions. This catalyst shows a marked preference for aromatic ring hydroxylation over lateral chain oxidation, both in intramolecular and intermolecular competitions, as long as the arene is not too electron poor. The selectivity pattern of the reaction closely matches that of electrophilic aromatic substitutions, with phenol yields and positions dictated by the nature of the ring substituent (electron-donating or electron-withdrawing, ortho-para or meta-orienting). The oxidation mechanism has been investigated in detail, and the sum of the accumulated pieces of evidence, ranging from KIE to the use of radical scavengers, from substituent effects on intermolecular and intramolecular selectivity to rearrangement experiments, points to the predominance of a metal-based SEAr pathway, without a significant involvement of free diffusing radical pathways.
- Capocasa, Giorgio,Olivo, Giorgio,Barbieri, Alessia,Lanzalunga, Osvaldo,Di Stefano, Stefano
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p. 5677 - 5686
(2017/12/07)
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- Highly Selective and Efficient Ring Hydroxylation of Alkylbenzenes with Hydrogen Peroxide and an Osmium(VI) Nitrido Catalyst
-
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
-
supporting information
p. 12260 - 12263
(2017/09/06)
-
- Synthesis and catalytic performance of HMCM-49/MCM-41 composite molecular sieve for alkylation of phenol with isopropanol
-
HMCM-49/MCM-41 composite molecular sieve was synthesized with hydrothermal method. The physicochemical properties of the composite were characterized by using XRD, FT-IR, SEM, N2 isothermal adsorption-desorption and NH3-TPD. Results of different characterizations indicated that the synthesized composite molecular sieve possessed the characteristics of both HMCM-49 and MCM-41. XRD and N2 isothermal adsorption-desorption revealed that it has both micropores and mesopores, a larger surface area than that of HMCM-49, NH3-TPD and pyridine adsorbed FT-IR revealed that the strong acidic sites that caused side reaction in HMCM-49 are deactivated in the composite molecular sieve of HMCM-49/MCM-41. When applied to the alkylation of phenol with isopropanol, the HMCM-49/MCM-41 composite molecular sieve exhibit an enhanced catalytic performance with significant enhancement in p-isopropylphenol and o-isopropylphenol selectivity, which can be ascribed to the composite characteristics of HMCM-49 and MCM-41. This kind of material will has widely industrial application in preparation of alkyl-phenol.
- Wei, Liguo,Wang, Dong,Dong, Yongli,Song, Weina,Liu, Xiaoxu,Song, Kunyao
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p. 2061 - 2066
(2017/01/28)
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- Construction of Acid–Base Synergetic Sites on Mg-bearing BEA Zeolites Triggers the Unexpected Low-Temperature Alkylation of Phenol
-
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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- Synthesis of (-)-Piperitylmagnolol Featuring ortho-Selective Deiodination and Pd-Catalyzed Allylation
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A 1,4-addition strategy using an enone and a copper reagent was studied for the synthesis of (-)-piperitylmagnolol. A MOM-protected biphenol copper reagent was added to BF3·OEt2-activated 4-isopropylcyclohexenone, whereas 1,4-addition of protected monophenol reagents possessing an allyl group was found to be unsuccessful. The allyl group was later attached to the p-,p′-diiodo-biphenol ring by Pd-catalyzed coupling with allylborate. The aforementioned iodide was synthesized using a new method for ortho-selective deiodination of o-,p-diiodophenols.
- Ikoma, Atsushi,Ogawa, Narihito,Kondo, Daiki,Kawada, Hiroki,Kobayashi, Yuichi
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supporting information
p. 2074 - 2077
(2016/06/01)
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- IPSO-hydroxylation of boronic acid via ozonolysis: A metal-, ligand-, and base-free method
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Here, we have developed a simple, efficient, and metal-, ligand-, and base-free method for the synthesis of functionalized aryl and alicyclic alcohols via ozonolysis of corresponding boronic acids in aqueous ethanol. The procedure is compatible with a variety of functional groups and can be utilized as an alternative method for the synthesis of hydroxy arenes and alicyclic alcohols.
- Bommegowda, Yadaganahalli K.,Mallesha, Ningegowda,Vinayaka, Ajjampura C.,Sadashiva, Maralinganadoddi P.
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supporting information
p. 268 - 270
(2016/05/02)
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- Design and synthesis of a novel series of [1-(4-hydroxy-benzyl)-1H-indol-5-yloxy]-acetic acid compounds as potent, selective, thyroid hormone receptor β agonists
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The design, synthesis, and structure activity relationships for a novel series of indoles as potent, selective, thyroid hormone receptor β (TRβ) agonists is described. Compounds with >50× binding selectivity for TRβ over TRα were generated and evaluation of compound 1c from this series in a model of dyslipidemia demonstrated positive effects on plasma lipid endpoints in vivo.
- Burkholder, Timothy P.,Cunningham, Brian E.,Clayton, Joshua R.,Lander, Peter A.,Brown, Matthew L.,Doti, Robert A.,Durst, Gregory L.,Montrose-Rafizadeh, Chahrzad,King, Constance,Osborne, Harold E.,Amos, Robert M.,Zink, Richard W.,Stramm, Lawrence E.,Burris, Thomas P.,Cardona, Guemalli,Konkol, Debra L.,Reidy, Charles,Christe, Michael E.,Genin, Michael J.
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p. 1377 - 1380
(2015/03/30)
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- Selective catalytic conversion of guaiacol to phenols over a molybdenum carbide catalyst
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An activated carbon supported α-molybdenum carbide catalyst (α-MoC1-x/AC) showed remarkable activity in the selective deoxygenation of guaiacol to substituted mono-phenols in low carbon number alcohol solvents. Combined selectivities of up to 85% for phenol and alkylphenols were obtained at 340°C for α-MoC1-x/AC at 87% conversion in supercritical ethanol. The reaction occurs via consecutive demethylation followed by a dehydroxylation route instead of a direct demethoxygenation pathway.
- Ma, Rui,Cui, Kai,Yang, Le,Ma, Xiaolei,Li, Yongdan
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supporting information
p. 10299 - 10301
(2015/06/25)
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- Direct Hydroxylation of Benzene to Phenol Using Hydrogen Peroxide Catalyzed by Nickel Complexes Supported by Pyridylalkylamine Ligands
-
Selective hydroxylation of benzene to phenol has been achieved using H2O2 in the presence of a catalytic amount of the nickel complex [NiII(tepa)]2+ (2) (tepa = tris[2-(pyridin-2-yl)ethyl]amine) at 60°C. The maximum yield of phenol was 21% based on benzene without the formation of quinone or diphenol. In an endurance test of the catalyst, complex 2 showed a turnover number (TON) of 749, which is the highest value reported to date for molecular catalysts in benzene hydroxylation with H2O2. When toluene was employed as a substrate instead of benzene, cresol was obtained as the major product with 90% selectivity. When H218O2 was utilized as the oxidant, 18O-labeled phenol was predominantly obtained. The reaction rate for fully deuterated benzene was nearly identical to that of benzene (kinetic isotope effect = 1.0). On the basis of these results, the reaction mechanism is discussed.
- Morimoto, Yuma,Bunno, Shuji,Fujieda, Nobutaka,Sugimoto, Hideki,Itoh, Shinobu
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supporting information
p. 5867 - 5870
(2015/05/27)
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- Ligand- and base-free synthesis of phenols by rapid oxidation of arylboronic acids using iron(III) oxide
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Fe2O3 catalyzed rapid oxidation of arylboronic acids to obtain phenols in excellent yields (90-95%) in the presence of atmospheric oxygen under solar VIS-light irradiation using α-Fe2O3 as a catalyst in ligand- and base-free conditions is presented.
- Sawant, Sanghapal D.,Hudwekar, Abhinandan D.,Aravinda Kumar,Venkateswarlu, Vunnam,Singh, Parvinder Pal,Vishwakarma, Ram A.
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p. 811 - 814
(2015/03/03)
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- Protonation switching to the least-basic heteroatom of carbamate through cationic hydrogen bonding promotes the formation of isocyanate cations
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We found that phenethylcarbamates that bear ortho-salicylate as an ether group (carbamoyl salicylates) dramatically accelerate O-C bond dissociation in strong acid to facilitate generation of isocyanate cation (N-protonated isocyanates), which undergo subsequent intramolecular aromatic electrophilic cyclization to give dihydroisoquinolones. To generate isocyanate cations from carbamates in acidic media as electrophiles for aromatic substitution, protonation at the ether oxygen, the least basic heteroatom, is essential to promote C-O bond cleavage. However, the carbonyl oxygen of carbamates, the most basic site, is protonated exclusively in strong acids. We found that the protonation site can be shifted to an alternative basic atom by linking methyl salicylate to the ether oxygen of carbamate. The methyl ester oxygen ortho to the phenolic (ether) oxygen of salicylate is as basic as the carbamate carbonyl oxygen, and we found that monoprotonation at the methyl ester oxygen in strong acid resulted in the formation of an intramolecular cationic hydrogen bond (>C=O+-H...O) with the phenolic ether oxygen. This facilitates O-C bond dissociation of phenethylcarbamates, thereby promoting isocyanate cation formation. In contrast, superacid-mediated diprotonation at the methyl ester oxygen of the salicylate and the carbonyl oxygen of the carbamate afforded a rather stable dication, which did not readily undergo C-O bond dissociation. This is an unprecedented and unknown case in which the monocation has greater reactivity than the dication.
- Kurouchi, Hiroaki,Sumita, Akinari,Otani, Yuko,Ohwada, Tomohiko
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supporting information
p. 8682 - 8690
(2014/07/21)
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- Ligand- and base-free synthesis of phenols by rapid oxidation of arylboronic acids using iron(III) oxide
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Fe2O3 catalyzed rapid oxidation of arylboronic acids to obtain phenols in excellent yields (90-95%) in the presence of atmospheric oxygen under solar VIS-light irradiation using α-Fe2O 3 as a catalyst in ligand- and base-free conditions is presented.
- Sawant, Sanghapal D.,Hudwekar, Abhinandan D.,Aravinda Kumar,Venkateswarlu, Vunnam,Singh, Parvinder Pal,Vishwakarma, Ram A.
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p. 811 - 814
(2014/02/14)
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- PROCESS FOR PREPARING ALKYLATED HYDROXYAROMATICS IN MICROREACTORS
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A process is proposed for preparing hydroxyaromatics by heterogeneous catalytic reaction of hydroxyaromatics with C1-C4-alkanols in a microreactor (10), comprising the steps of: a) introducing the hydroxyaromatic and at least one compound selected from the group consisting of C1-C4-alkanols as reactants into at least one inlet orifice (22) of the microreactor (10) comprising at least one microreactor unit (18),b) passing the reactants through at least one microreactor unit (18) of the microreactor (10), said unit comprising a multitude of microchannels (28), said microchannels (28) having a lateral extent of less than 1 mm, and a heterogeneous catalyst being incorporated in the microchannels (28) for conversion of the reactants,c) passing the hydroxyaromatics prepared out through at least one outlet orifice (24) of the microreactor (10).
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Page/Page column 6
(2012/09/25)
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- Chemo- and regioselective direct hydroxylation of arenes with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
-
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)
-
- Catalytic performance of Al-MCM-48 molecular sieves for isopropylation of phenol with isopropyl acetate
-
Al-MCM-48 molecular sieves (Si/Al molar ratios = 25, 50, 75, and 100) were synthesized hydrothermally using cetyltrimethylammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffr
- Venkatachalam, Kandan,Visuvamithiran, Pitchai,Sundaravel, Balachandran,Palanichamy, Muthiapillai,Murugesan, Velayutham
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experimental part
p. 478 - 486
(2012/07/17)
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- Low Triphenylphosphate, High Phosphorous Content Isopropyl Phenyl Phosphates With High Ortho Alkylation
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The present invention relates to low triphenyl phosphate, high phosphorous content aryl phosphates with high ortho alkylation that are suitable for use as flame retardant compositions, processes for their preparation, and their use as flame retardants.
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Page/Page column 9
(2012/01/14)
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- Reductive cleavage versus hydrogenation of allyl aryl ethers and allylic esters using sodium borohydride/catalytic ruthenium(III) in various aqueous solvent mixtures
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The reduction of allyl aryl ethers using sodium borohydride in the presence of a catalytic amount of ruthenium(III) chloride in various aqueous solvent mixtures at 0 °C was examined. In aqueous tetrahydrofuran, hydrogenation was the favored pathway (85-100% yield of the corresponding aryl propyl ether); whereas in aqueous N-methylformamide, reductive cleavage predominated (4:1 mixture of phenolic product/aryl propyl ether). In order to gain some insight into the mechanism for this process, 3-octyn-1-ol and trans-2-decen-1-yl acetate were subjected to similar reductive conditions; and both substrates afforded products inconsistent with a single-electron-transfer mechanism.
- Babler, James H.,White, Nicholas A.,Kowalski, Eric,Jast, Jeffrey R.
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experimental part
p. 745 - 748
(2011/03/21)
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- ANALOGS OF PROPOFOL, PREPARATION THEREOF AND USE AS ANESTHETICS
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Compounds of formula (I) wherein X is H or F and pharmaceutically acceptable salts thereof are useful as anesthetics.
- -
-
Page/Page column 16-17
(2009/12/23)
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- Zirconia-modified superacid UDCaT-5: An efficient and versatile catalyst for alkylation reactions under solvent-free conditions
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UDCaT-5, a modified version of zirconia, efficiently catalyzes alkylation of phenols with alcohols under environmentally safe, heterogeneous reaction conditions with high selectivity and in excellent yields. The high content present in UDCaT-5 with preservation of tetragonal phase of zirconia was responsible for the superactivity. Several phenolic compounds carrying either electron-sulfer releasing or electron-withdrawing substituents in the ortho, meta, and para positions afforded high yields of the products. Copyright Taylor & Francis Group, LLC.
- Yadav, Ganapati D.,Pathre, Ganesh S.
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p. 2684 - 2691
(2008/12/22)
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- Reaction of menthol and phenol in the presence of aluminium alkoxides
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Phenol was alkylated with menthol in the presence of organoaluminium catalysts such as aluminium phenoxide and aluminium isopropoxide. Reaction products were isolated and characterized. Certain features of the process were determined.
- Chukicheva,Fedorova,Koroleva,Kuchin
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experimental part
p. 450 - 454
(2009/04/11)
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- Desaturation of alkylbenzenes by cytochrome P450BM3 (CYP102A1)
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A study was conducted to investigate the desaturation of alkylbenezenes by cytochrome P450BM3 (CYP102A1). It was observed during the study that oxidation of alkylbenzenes with CYP102A1 involves a gamut of P450 activity types that are terminal, sub-terminal benzylic and aromatic hydroxylation; terminal and sub-terminal desaturation; and epoxidation of the olefins. It was also found that the desaturation of cumene by CYP102A1 is sensitive to α-deuteration and insensitive to β-deuteration. Intramolecular deuterium isotope study revealed that the first abstraction in the desaturation of valproic acid and ezlopitant by microsomal P450s take place from activated carbon atoms. The increased β-hydroxylation percentages show that the β-carbon lies closer to the ferryl oxygen in the KT5.
- Whitehouse, Christopher J.C.,Bell, Stephen G.,Wong, Luet-Lok
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supporting information; scheme or table
p. 10905 - 10908
(2009/11/30)
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- Palladium-catalyzed C-O bond formation: direct synthesis of phenols and aryl/alkyl ethers from activated aryl halides
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A simple and efficient palladium-catalyzed carbon-oxygen bond formation is reported. The palladium-tri-tert-butylphosphine complex was found to be effective in converting haloarenes to corresponding substituted phenols. This methodology offers a direct transformation of aryl halides to phenols, as well as the straightforward application to generate a wide variety of diaryl or alkyl/aryl ethers.
- Chen, Guoshu,Chan, Albert S.C.,Kwong, Fuk Yee
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p. 473 - 476
(2008/02/03)
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- The selective reaction of aryl halides with KOH: Synthesis of phenols, aromatic ethers, and benzofurans
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The direct and selective synthesis of phenols from aryl/heteroaryl halides and KOH has been achieved through the use of highly active monophosphine-based catalysts derived from Pd2dba3 and ligands L1 or L2 and the biphasic solvent system 1,4-dioxane/H2O. We have also demonstrated a one-pot method of phenol formation/alkylation for the preparation of alkyl aryl ethers from aryl halides. In many instances, this protocol overcomes limitations in existing Pd-catalyzed coupling reactions of aliphatic alcohols with aryl halides. Finally, we demonstrate that substituted benzofurans can be prepared efficiently via a Pd-catalyzed phenol formation/cyclization protocol starting from 2-chloroaryl alkynes. Copyright
- Anderson, Kevin W.,Ikawa, Takashi,Tundel, Rachel E.,Buchwald, Stephen L.
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p. 10694 - 10695
(2007/10/03)
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- Scope and limitations of lithium-ethylenediamine-THF-mediated cleavage at the α-position of aromatics: Deprotection of aryl methyl ethers and benzyl ethers under mild conditions
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The scope and limitation of lithium-ethylenediamine-THF-mediated reductive bond cleavage at the α-position of aromatics were examined. Very mild conditions such as lithium metal (5 equiv) and ethylenediamine (7 equiv) in oxygen-free THF were quite effective for the demethylation of aromatic ethers even at as low as -10°C. Allyl benzyl ethers were also deprotected under these conditions with very little change of the allylic alcohol moiety. Through this study, 2,6-dimethylbenzyl (m-xylylmethyl, MXM) group was developed as an alternative of benzyl group, which is readily cleavable under the above mentioned reductive conditions.
- Shindo, Takeyuki,Fukuyama, Yasuaki,Sugai, Takeshi
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p. 692 - 700
(2007/10/03)
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- Non-catalytic and selective alkylation of phenol with propan-2-ol in supercritical water
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Phenol can be alkylated with propan-2-ol without catalyst in supercritical water at 673 K with mainly ortho substituted alkylphenols being obtained and alkylation reaction rate increasing with increasing water density.
- Sato,Sekiguchi,Adschiri,Arai
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p. 1566 - 1567
(2007/10/03)
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- A mild anionic method for generating o-quinone methides: Facile preparations of ortho-functionalized phenols
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A low-temperature method for generating o-quinone methides is described which permits facile introduction of assorted R substituents onto the aryl ring system at low temperature. The method is useful for the efficient preparation of ortho-ring-alkylated phenols.
- Jones,Van De Water,Lindsey,Hoarau,Ung,Pettus
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p. 3435 - 3441
(2007/10/03)
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- A fluorescence detection scheme for capillary electrophoresis of N- methylcarbamates with on-column thermal decomposition and derivatization
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This paper describes a fluorescence detection method for N- methylcarbamate (NMC) pesticides in micellar electrokinetic chromatography (MEKC) separation. Fulfillment of the fluorescence detection hinged on the discovery that quaternary ammonium surfactants (particularly cetyltrimethylammonium bromide, CTAB), besides serving as hydrophobic pseudophases in MEKC, are also capable of catalyzing the thermal decomposition of NMCs to liberate methylamine. Thus, a multifunctional MEKC medium consisting of borate buffer, CTAB, and derivatizing components (o- phthaldialdehyde/2-mercaptoethanol) was formulated, which allowed first normal MEKC separation, subsequent thermal decomposition, and finally in situ derivatization of NMCs. With careful optimization of the operation conditions, fluorescence detection of 10 NMC compounds was achieved, with column efficiencies typically higher than 50 000 and detection limits better than 0.5 ppm. The present work represents an unprecedented effort in capillary electrophoresis (CE), in which an intact capillary was consecutively utilized as chambers for separation, decomposition, derivatization, and detection, without involving any interfacing features. The success in the implementation of such a detection system resulted in strikingly simple instrumentation as compared with the traditional postcolumn fluorescence determination of NMCs by reversed-phase HPLC. Similar protocols should be workable in the determination of a wide range of pesticides and pharmaceuticals in CE formats.
- Wu, Yuan Sheng,Lee, Hian Kee,Li
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p. 1441 - 1447
(2007/10/03)
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- The continuous acid-catalyzed dehydration of alcohols in supercritical fluids: A new approach to the cleaner synthesis of acetals, ketals, and ethers with high selectivity
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We report a new continuous method for forming ethers, acetals and ketals using solid acid catalysts, DELOXAN ASP or AMBERLYST 15, and supercritical fluid solvents. In the case of ether formation, we observe a high selectivity for linear alkyl ethers with little rearrangement to give branched ethers. Such rearrangement is common in conventional syntheses. Our approach is effective for a range of n-alcohols up to n-octanol and also for the secondary alcohol 2-propanol. In the reaction of phenol with an alkylating agent, the continuous reaction can be tuned to give preferential O- or C- alkylation with up to 49% O-alkylation with supercritical propene. We also investigate the synthesis of a range of cyclic ethers and show an improved method for the synthesis of THF from 1,4-butandiol under very mild conditions.
- Gray, William K.,Smail, Fiona R.,Hitzler, Martin G.,Ross, Stephen K.,Poliakoff, Martyn
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p. 10711 - 10718
(2007/10/03)
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- Acid-catalyzed hydrolysis of some primary alkyl phenyl ethers
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Products were analyzed and rate constants of disappearance and hydrolysis, alkylation and/or rearrangement were measured for methyl, ethyl, propyl and allyl phenyl ethers by GC in concentrated aqueous perchloric acid solutions. Chlorination of the substrate and possibly of the product, phenol, was observed beside the hydrolysis of methyl phenyl ether and a slight chlorination of phenol beside the hydrolysis of ethyl phenyl ether. A marked Claisen rearrangement to isopropylphenols and alkylation to propyl isopropylphenyl ethers were observed in addition to the hydrolysis of propyl phenyl ether. The Claisen rearrangement to o-allylphenol was estimated to be quantitative in the case of allyl phenyl ether. The change of the reaction mechanism from A-2 (MeOPh and EtOPh) possibly via A-2(carbocation)(PrOPh?) to A-1 (allyl phenyl ether and possibly PrOPh) was deduced from the products, reaction rates, activation parameters, solvent deuterium isotope effect and parameters of excess acidity plots. Acta Chemica Scandinavica 1997.
- Lajunen, Martti,Laine, Riitta,Aaltonen, Marika
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p. 1155 - 1161
(2007/10/03)
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- ALKYLATING PROPERTIES OF ACID ORGANIC PHOSPHATES
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Under the action of phenols and alcohols, acid alkyl phosphates undergo transesterification, which is accompanied by dealkylation of the latter and alkylation of the alcohols (phenols) at the hydroxy groups and aromatic rings.Isopropyl phosphates are stronger alkylating agents than methyl phosphates.Diphenyl methyl and phenyl dimethyl phosphates yield products of methylation of their own aromatic rings only upon prolonged pyrolysis.In all cases organic polyphosphates are formed.
- Munik, S. N.,Eliseenkov, V. N.,Ivanov, B. E.
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p. 378 - 382
(2007/10/03)
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- Mechanism of Arene Hydroxylation by Vanadium Picolinato Peroxo Complexes
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The mechanism of the reaction of VO(O2)PIC(H2O)2 (PIC = picolinic acid anion) with benzene and substituted benzenes in CH3CN, affording the corresponding phenols together with dioxygen, has been further investigated.The reaction is a radical chain process whose initiation produces the actual oxidant which may be described as a radical anion derived from the peroxovanadium complex, possessing, however, a marked electrophilic character.In the propagation steps such species react either with the original peroxo complex yielding dioxygen or with the aromatic substrates affording phenols via the formation of an intermediate.
- Bonchio, Marcella,Conte, Valeria,Di Furia, Fulvio,Modena, Giorgio,Moro, Stefano
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p. 6262 - 6267
(2007/10/02)
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- Acid-Catalyzed Hydrolysis of Some Secondary Alkyl Phenyl Ethers in Perchloric Acid: Kinetics and Mechanism
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Hydrolysis rates and products of isopropyl, cyclopentyl and cyclohexyl phenyl ethers were studied in concentrated aqueous perchloric acid solutions.The activation parameters, solvent deuterium isotope effects, dependences of the reaction rates on acid concentration, substituent effects and products were in agreement with the A-1 mechanism.The pKSH+ values (-6.13 to -5.76) and the slope parameters m* (av. 0.98 +/- 0.03) were measured spectrophotometrically by the excess acidity method.They were used to calculate the m++-parameters (1.46-2.01).Comparisons weremade with the hydrolyses of exo- ad endo-2-norbornyl phenyl ethers and secondary alyl methanesulfonates.
- Lajunen, Martti,Kaehkoenen, Mika
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p. 726 - 731
(2007/10/02)
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- Process for the production of N-methylcarbamates
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Process for the production of N-methylcarbamates: STR1 (wherein RO- is the radical of a substituted phenol or of a naphthol), wherein: in a first reaction step methylamine and diphenyl carbonate are reacted with each other, operating in the liquid phase and as a continuous process, in order to form phenol and phenyl-N-methylurethane; in a second reaction step phenyl-N-methylurethane, within the related reaction mixture outcoming from the first step, is thermally continuously decomposed, to yield a gaseous stream containing methyl isocyanate, from which the components different than methyl isocyanate are condensed off; in a third step the methyl isocyanate stream, outcoming from the second step, after an optional preliminary condensation, is continuously fed and contacted with a solution of a substituted phenol or of a naphthol in an inert organic solvent, containing a basic catalyst, to form N-methylcarbamate (I); N-methylcarbamate (I) is finally recovered from the reaction mixture outcoming from the third step.
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- Preparation of diphenolics
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A process for the production of diphenolic compounds having a divalent bridge. A first disubstituted phenol is reacted with an aldehyde in the presence of a secondary amine and excess alcohol to form an ether intermediate. The ether intermediate is reacted with a phenol having an open ortho or para position to form a diphenolic.
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- Process for the selective production of dihydroxybenzenes
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The known nuclear hydroxylation of phenol or substituted phenols or phenol ethers with organic solutions of hydrogen peroxide in the presence of a catalyst is carried out in improved manner by employing both (1) a special, practically water free solution of hydrogen peroxide in an organic solvent which forms an azeotrope with water, which azeotrope boils below the boiling point of hydrogen peroxide, and (2) selenium dioxide as a catalyst. Through this, the nuclear hydroxylation is substantially simpler than previously. Besides, for the first time, it is possible to control the ortho to para ratio or the two ortho ratios to each other.
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- REACTION OF PHENOL WITH ALKYLBENZENES ON A ZEOLITE-CONTAINING CATALYST.
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The purpose of this investigation is a study of transfer of ethyl and isopropyl groups from the aromatic hydrocarbon molecule to phenol with a zeolite-containing catalyts. From the data given it is evident that ethyltoluene reacts with phenol significantly more energetically than ethylbenzene. In addition, the reaction proceeded well at 350 degree C with 15% conversion of phenol. Under these conditions, the main transalkylation product was a mixture of ethylphenol isomers. Increasing the temperature increased the conversion both of phenol and of the hydrocarbon. However, this led to a decrease of the yield of ethylphenols and simultaneously to an increase of the amount of cresols in the reaction products.
- Sibarov,Dokuchaeva,Mukhin
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p. 2479 - 2481
(2007/10/02)
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- Superacid catalyzed preparation of resorcinol from meta-isopropylepheol
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Resorcinol is prepared by an improved process through superacid (such as perfluorinated alkanesulfonic superacids of one to eighteen carbon atoms or polymeric perfluorinated resinsulfonic acids, such as Nafion-H) catalyzed cleavage-rearrangement reaction of meta-isopropylphenol hydroperoxide in the form of its protected ether or ester derivatives, including readily cleavable and reusable trimethylsilyl and trifluoromethanesulfonyl derivates. Part of the process is the preparation of needed meta-isopropylphenol in high purity free of other isomers by treating any mixture of isopropylphenol isomers in an excess of anhydrous hydrogen fluoride or a perfluorinated alkanesulfonic superacid of one to eighteen carbon atoms and a Lewis acid fluoride or by alkylating (transalkylating) phenol with a propyl alkylating agent in the presence of the aforementioned superacid systems.
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- PHOTOOXIDATION OF SOME AROMATIC SULFONIC ACIDS WITH ALKALINE HYPOCHLORITE.
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Photochemical oxidation of aromatic sulfonic acids such as p-cumenesulfonic, 2-mesitylenesulfonic, 1- and 2-naphthalensulfonic acids with aqueous sodium hypochlorite has been studied. Addition of a large excess of alkali enhances the decomposition of sulfonic acids remarkably. p-Cumenesulfonic and 2-mesitylenesulfonic acids are oxidized faster than 1- and 2-naphthalenesulfonic acids. The photooxidation of sulfonic acids with an equimolar amount of hypochlorite gives intermediary oxidation products involving desulfonation to parent hydrocarbons, aromatic hydroxylation, side-chain oxidation, and ring cleavage; e. g. , p-cumenesulfonic acid gives cumene, 2- and 4-isopropylphenol and 2-phenyl-2-propanol; 1- and 2-naphthalenesulfonic acids give phthalic anhydride. Light-absorbing aromatic sulfonic acids sensitize the decomposition of hypochlorite ion leading to hydroxyl radical, which reacts mainly with ground state sulfonic acid to give radical intermediates.
- Kimura,Ogata
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p. 471 - 473
(2007/10/02)
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- Superacid catalyzed preparation of resorcinol from meta-isopropylphenol
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Resorcinol is prepared by an improved process through superacid (such as perfluorinated alkanesulfonic superacids of one to eighteen carbon atoms or polymeric perfluorinated resinsulfonic acids, such as Nafion-H catalyzed cleavage-rearrangement reaction of meta-isopropylphenol hydroperoxide in the form of its protected ether or ester derivatives, including readily cleavable and reusable trimethylsilyl and trifluoromethanesulfonyl derivates. Part of the process is the preparation of needed meta-isopropylphenol in high purity free of other isomers by treating any mixture of isopropylphenol isomers in an excess of anhydrous hydrogen fluoride or a perfluorinated alkanesulfonic superacid of one to eighteen carbon atoms and a Lewis acid fluoride or by alkylating (transalkylating) phenol with a propyl alkylating agent in the presence of the aforementioned superacid systems.
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- DIRECT HYDROXYLATION OF COMPOUNDS IN AN RF PLASMA
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The hydoxylation of aromatic compounds was carried out in the plasma generated by a radiofrequency discharge.Benzene and naphthalene yielded phenol and naphthols, respectively, as single volatile products.With respect to alkylbenzenes, the oxidation of the side-chains competed with the aromatic hydroxylation.
- Tezuka, Meguru,Yajima, Tatsuhiko,Tsuchiya, Atsuhiko
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p. 1437 - 1438
(2007/10/02)
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- Superacid catalyzed preparation of resorcinol from meta-isopropylphenol
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Resorcinol is prepared by an improved process through superacid (such as perfluorinated alkanesulfonic acids of one to eighteen carbon atoms or polymeric perfluorinated resinsulfonic acids, such as Nafion-H catalyzed cleavage-rearrangement reaction of meta-isopropylphenol hydroperoxide in the form of its protected ether or ester derivatives, including readily cleavable and reusable trimethylsilyl and trifluoromethanesulfonyl derivates. Part of the process is the preparation of needed meta-isopropylphenol in high purity free of other isomers by treating any mixture of isopropylphenol isomers in an excess of anhydrous hydrogen fluoride or a perfluorinated alkanesulfonic acid of one to six carbon atoms and a Lewis acid fluoride or by alkylating (transalkylating) phenol with a propyl alkylating agent in the presence of the aforementioned superacid systems.
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- Alumina-Catalyzed Reactions of Hydroxyarenes and Hydroaromatic Ketones. 10. Reaction of Phenol with 2-Propanol
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At 300-350 deg C in the presence of alumina, phenol (1) reacts with excess 2-propanol (37) to give mixed monopropyl-, dipropyl-, and 2,4,6-triisopropyl- (42) phenols. At 300 deg C the principal components of the product mixture are 2-isopropylphenol (26-30 mol percent yield) and 2,6-diisopropylphenol (44-52percent); at 350-400 deg C , they are the isomeric monoisopropylphenols (50-60percent). With 3-isopropylphenol as substrate (instead of 1), 2,5-diisopropylphenol is obtained (79percent), while 4-isopropylphenol gives 2,4-diisopropylphenol and 42 (70percent combined yield). In various runs, 0-20percent of the propyl groups introduced are n-propyl ones. It is proposed that the principal products result from an SN2-type reaction mechanism which involves nucleophilic attack (variously by C-2, C-4, and C-6) of an adsorbed ambident phenoxide ion onto C-2 of an adsorbed isopropoxide group. n-Propylation is ascribed to a side reaction of SN1 type.
- Klemm, LeRoy H.,Taylor, Dennis R.
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p. 4326 - 4329
(2007/10/02)
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