- Aromatic C?H Hydroxylation Reactions with Hydrogen Peroxide Catalyzed by Bulky Manganese Complexes
-
The oxidation of aromatic substrates to phenols with H2O2 as a benign oxidant remains an ongoing challenge in synthetic chemistry. Herein, we successfully achieved to catalyze aromatic C?H bond oxidations using a series of biologically inspired manganese catalysts in fluorinated alcohol solvents. While introduction of bulky substituents into the ligand structure of the catalyst favors aromatic C?H oxidations in alkylbenzenes, oxidation occurs at the benzylic position with ligands bearing electron-rich substituents. Therefore, the nature of the ligand is key in controlling the chemoselectivity of these Mn-catalyzed C?H oxidations. We show that introduction of bulky groups into the ligand prevents catalyst inhibition through phenolate-binding, consequently providing higher catalytic turnover numbers for phenol formation. Furthermore, employing halogenated carboxylic acids in the presence of bulky catalysts provides enhanced catalytic activities, which can be attributed to their low pKa values that reduces catalyst inhibition by phenolate protonation as well as to their electron-withdrawing character that makes the manganese oxo species a more electrophilic oxidant. Moreover, to the best of our knowledge, the new system can accomplish the oxidation of alkylbenzenes with the highest yields so far reported for homogeneous arene hydroxylation catalysts. Overall our data provide a proof-of-concept of how Mn(II)/H2O2/RCO2H oxidation systems are easily tunable by means of the solvent, carboxylic acid additive, and steric demand of the ligand. The chemo- and site-selectivity patterns of the current system, a negligible KIE, the observation of an NIH-shift, and the effectiveness of using tBuOOH as oxidant overall suggest that hydroxylation of aromatic C?H bonds proceeds through a metal-based mechanism, with no significant involvement of hydroxyl radicals, and via an arene oxide intermediate. (Figure presented.).
- Masferrer-Rius, Eduard,Borrell, Margarida,Lutz, Martin,Costas, Miquel,Klein Gebbink, Robertus J. M.
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p. 3783 - 3795
(2021/03/09)
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- Controlled lignosulfonate depolymerization: Via solvothermal fragmentation coupled with catalytic hydrogenolysis/hydrogenation in a continuous flow reactor
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Sodium lignosulfonate (LS) was valorized to low molecular weight (Mw) fractions by combining solvothermal (SF) and catalytic hydrogenolysis/hydrogenation fragmentation (SHF) in a continuous flow system. This was achieved in either alcohol/H2O (EtOH/H2O or MeOH/H2O) or H2O as a solvent and Ni on nitrogen-doped carbon as a catalyst. The tunability according to the temperature of both SF and catalytic SHF of LS has been separately investigated at 150 °C, 200 °C, and 250 °C. In SF, the minimal Mw was 2994 g mol-1 at 250 °C with a dispersity (?) of 5.3 using MeOH/H2O. In catalytic SHF using MeOH/H2O, extremely low Mw was found (433 mg gLS-1) with a ? of 1.2 combined with 34 mg gLS-1. The monomer yield was improved to 42 mg gLS-1 using dual catalytic beds. These results provide direct evidence that lignin is an unstable polymer at elevated temperatures and could be efficiently deconstructed under hydrothermal conditions with and without a catalyst. This journal is
- Al-Naji, Majd,Antonietti, Markus,Brandi, Francesco
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supporting information
p. 9894 - 9905
(2021/12/24)
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- Rational design of oligomeric MoO3 in SnO2 lattices for selective hydrodeoxygenation of lignin derivatives into monophenols
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Novel Mo-Sn bimetallic oxide catalysts with highly dispersed oligomeric MoO3 in SnO2 lattices, which were synthesized by the co-precipitation method and pretreated by anhydrous ethanol, were first employed in the hydrodeoxygenation of various lignin derivatives to produce monophenols with high activity and selectivity. In comparison with the pure α-MoO3 and the previous reported catalysts, the α-2Mo1Sn exhibited superior activity in the hydrodeoxygenation of guaiacol, with full conversion and 92.5% phenol yield at 300 °C under 4 MPa initial H2 pressure in n-hexane for 4 h. According to comprehensive characterizations and catalytic measurements, the excellent performance of α-2Mo1Sn was ascribed to the formation of abundant Sn-O-Mo-OV interfacial sites, which possessed strong Mo-Sn interaction with enhanced surface area, electron-donating group binding ability, Lewis acidity, and redox ability. It was demonstrated that over the present α-2Mo1Sn catalyst system, the Sn-O-Mo-OV interfacial sites could greatly facilitate the adsorption and activation of Caromatic-OCH3 and Caromatic-CH3 bonds, and thus significantly promote the demethoxylation and demethylation reaction to produce phenol. This work figures out the rational design of MoO3-based catalyst and displays a clear potential for the selective hydrodeoxygenation of lignin derivatives into monophenols.
- Diao, Xinyong,Ji, Na,Jia, Zhichao,Jiang, Sinan,Li, Tingting,Liu, Caixia,Liu, Qingling,Lu, Xuebin,Song, Chunfeng,Wang, Zhenjiao
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p. 234 - 251
(2021/08/19)
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- CATALYTIC FUNNELING OF PHENOLICS
-
In general, present invention concerns an integrated wood-to-xylochemicals biorefinery, enabling production of renewable phenol, phenolic oligomers, propylene, and carbohydrate pulp from lignocellulosic biomass.
- -
-
Paragraph 0025; 0087-0088; 0133-0139; 0142; 0145
(2021/04/30)
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- Activity and specificity studies of the new thermostable esterase EstDZ2
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In this paper, we study the activity and specificity of EstDZ2, a new thermostable carboxyl esterase of unknown function, which was isolated from a metagenome library from a Russian hot spring. The biocatalytic reaction employing EstDZ2 proved to be an efficient method for the hydrolysis of aryl p-, o- or m-substituted esters of butyric acid and esters of secondary alcohols. Docking studies revealed structural features of the enzyme that led to activity differences among the different substrates.
- Myrtollari, Kamela,Katsoulakis, Nikolaos,Zarafeta, Dimitra,Pavlidis, Ioannis V.,Skretas, Georgios,Smonou, Ioulia
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supporting information
(2020/09/16)
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- Photocatalytic transfer hydrogenolysis of aromatic ketones using alcohols
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A mild method of photocatalytic deoxygenation of aromatic ketones to alkyl arenes was developed, which utilized alcohols as green hydrogen donors. No hydrogen evolution during this transformation suggested a mechanism of direct hydrogen transfer from alcohols. Control experiments with additives indicated the role of acid in transfer hydrogenolysis, and catalyst characterization confirmed a larger number of Lewis acidic sites on the optimal Pd/TiO2 photocatalyst. Hence, a combination of hydrogen transfer sites and acidic sites may be responsible for efficient deoxygenation without additives. The photocatalyst showed reusability and achieved selective reduction in a variety of aromatic ketones.
- Gao, Zhuyan,Han, Jianyu,Hong, Feng,Lei, Lijun,Li, Hongji,Liu, Huifang,Luo, Nengchao,Wang, Feng
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p. 3802 - 3808
(2020/07/09)
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- One-pot hydrodeoxygenation (HDO) of lignin monomers to C9 hydrocarbons co-catalysed by Ru/C and Nb2O5
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A physical mixture of Ru/C and Nb2O5 is an effective catalyst for upgrading lignin monomers under low H2 pressure at 250 °C to a clean cut of hydrocarbon liquid fuels. The reaction solvent is water with a small amount of methanol additive. Hydrodeoxygenation (HDO) was evaluated using dihydroeugenol (DHE) as an exemplary lignin monomer model. Under optimized conditions, 100% conversion of DHE and very high selectivity to propyl cyclohexane (C9 hydrocarbon) was achieved. Nb2O5 was prepared at a low temperature (450 °C) and was shown to contain acid sites that enhance the production of fully deoxygenated products. The methanol additive serves as a hydrogen source for the Ru/C catalysed reduction of the aromatic ring. In addition, when a substrate mixture of DHE, isoeugenol and 4-allylsyringol simulating lignin products was employed, 100% conversion to propyl cyclohexane (76%) and propyl benzene (24%) was observed, thereby suggesting the general applicability of this catalyst system for funneling lignin monomers into a clean cut of hydrocarbon liquid fuels. This study sheds light on the function of each catalyst component and provides a simple and green utilization of biomass monomers as a feedstock for renewable hydrocarbon fuels. This journal is
- Abu-Omar, Mahdi M.,Ford, Peter C.,Li, Simin,Liu, Baoyuan,Luo, Zhongyang,Truong, Julianne
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supporting information
p. 7406 - 7416
(2020/11/25)
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- Low-Temperature Catalytic Hydrogenolysis of Guaiacol to Phenol over Al-Doped SBA-15 Supported Ni Catalysts
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Selective hydrogenolysis of aromatic carbon-oxygen (Caryl?O) bonds is a key strategy for the generation of aromatic chemicals from lignin. However, this process is usually operated at high temperatures and pressures over hydrogenation catalysts, resulting in a low selectivity for aromatics and an extra consumption of hydrogen. Here, a series of Al-doped SBA-15 mesoporous materials with different Si/Al molar ratios (Al-SBA-15) were prepared via a post-synthesis method using NaAlO2 as the Al source, and then Al-SBA-15 supported Ni catalysts (Ni/Al-SBA-15) were prepared by a deposition-precipitation method using urea as the hydrolysis reagent. The prepared supports and catalysts were extensively characterized using various techniques such as XRD, N2 adsorption/desorption, TEM, 27Al NMR, NH3-TPD, XPS, H2-TPR, and pyridine-FT-IR, and the catalysts were evaluated in the hydrogenolysis of the Caryl?O bond in guaiacol and lignin derived compounds under mild conditions. The effects of the Si/Al ratio in catalyst and reaction parameters on guaiacol conversion and product distribution were investigated in detail, associated with solvent effect. The incorporation of Al into the framework of SBA-15 can improve the Lewis acidity and the dispersion of the supported Ni particles and yet modulate the metal-support interactions, which are propitious to the hydrogenolysis of the Caryl?O bond in guaiacol. The catalyst Ni/Al-SBA-15 with a Si/Al molar ratio of 10 shows the best performance with a guaiacol conversion of 87.4 % and a phenol selectivity of 76.9 % under the mild conditions conducted, because of its proper acidity, suitable metal-support interactions, and high dispersion of the active species. The present study would stimulate research and development in multi-functional catalysts for the generation of valuable chemicals from biomass.
- Wang, Qiuyue,Chen, Yufang,Yang, Guanheng,Deng, Ping,Lu, Xinqing,Ma, Rui,Fu, Yanghe,Zhu, Weidong
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p. 4930 - 4938
(2020/08/26)
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- Efficient Conversion of Pine Wood Lignin to Phenol
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Obtaining chemical building blocks from biomass is attractive for meeting sustainability targets. Herein, an effective approach was developed to convert the lignin part of woody biomass into phenol, which is a valuable base chemical. Monomeric alkylmethoxyphenols were obtained from pinewood, rich in guaiacol-type lignin, through Pt/C-catalyzed reductive depolymerization. In a second step, an optimized MoP/SiO2 catalyst was used to selectively remove methoxy groups in these lignin monomers to generate 4-alkylphenols, which were then dealkylated by zeolite-catalyzed transalkylation to a benzene stream. The overall yield of phenol based on the initial lignin content in pinewood was 9.6 mol %.
- Boot, Michael D.,Hensen, Emiel J. M.,Huang, Xiaoming,Ouyang, Xianhong
-
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- Degradation of lignin with aqueous ammonium-based ionic liquid solutions under milder conditions
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This study investigates the performance of two aqueous ionic liquids (ILs), dimethylbutylammonium acetate ([DMBA][Ac]) and dimethylbutylammonium butanoate ([DMBA][B]), solutions for depolymerizing alkali lignin into valuable phenolic compounds. The favorable operation conditions, including reaction temperature and reaction time, are explored. The extent of depolymerization of the lignin is evaluated by analysis with gel permeation chromatography (GPC). The results show that the average molecular weights of the depolymerized lignin samples can be reduced by as high as 93.8% and 86.8% after treating with the aqueous [DMBA][Ac] and [DMBA][B], respectively. Moreover, the aromatic chemical species in the depolymerized solutions are identified by using gas chromatography?mass spectrophotometry (GC-MS). The confirmation of the chemical species is further made by using a series of spectroscopic techniques, such as FT-IR, and 1H NMR and 13C NMR spectroscopy. Promising results have been achieved for the depolymerization of the lignin into valuable chemicals by using the proposed green media, aqueous solutions of ionic liquids [DMBA][Ac] and [DMBA][B], under milder conditions.
- Gupta, Bhupender S.,Lee, Ming-Jer,Tolesa, Leta Deressa
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p. 3357 - 3365
(2019/02/25)
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- Selective Preparation of 4-Alkylphenol from Lignin-Derived Phenols and Raw Biomass over Magnetic Co–Fe?N-Doped Carbon Catalysts
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Lignin valorization to produce high-value chemicals selectively is an enormous challenge in biorefinery. In this study, 4-alkylphenol, formed by breaking the robust Caryl?OCH3 bonds solely with the retention of other structures in lignin-derived methoxylalkylphenols, was produced selectively over a Co1–Fe0.1?NC catalyst from real lignin oil as feedstock, which was obtained by a “lignin-first” strategy from either birch or cornstalk. A yield of 64.7 or 88.3 mol % of 4-propylphenol was obtained if birch lignin oil or eugenol was used as the substrate, respectively. The catalysts were characterized by using methods that include Brunauer–Emmett–Teller measurements, XRD, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and temperature-programmed desorption with synchrotron vacuum ultraviolet photoionization mass spectrometry. The results of catalyst characterization and comparison experiments indicated that CoNx was the main active phase for demethoxylation and hydrogenation, and the incorporation of Fe weakens the adsorption of 4-propylphenol to the catalyst, which inhibits the excessive hydrogenation of 4-propylphenol. This work shows the potential to produce high-value-added 4-alkylphenol from renewable raw biomass.
- Liu, Xiaohao,Wang, Chenguang,Zhang, Ying,Qiao, Yan,Pan, Yang,Ma, Longlong
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p. 4791 - 4798
(2019/11/03)
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- CATALYTIC CONVERSION OF BIOMASS TO BIOPHENOL
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The invention relates to a demethoxylation process for demethoxylating alkylmethoxyphenols using an aromatic solvent to produce alkylphenols. The invention also relates to dealkylation process for dealkylating alkylphenols using an aromatic solvent to produce phenol. The invention further relates to a tandem demethoxylation and dealkylation process, which can be performed in a single reactor. The process is useful in the conversion of lignin derived alkylmethoxyphenols into biophenol.
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Page/Page column 19; 21-22
(2019/10/04)
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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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- Production of Terephthalic Acid from Corn Stover Lignin
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Funneling and functionalization of a mixture of lignin-derived monomers into a single high-value chemical is fascinating. Reported herein is a three-step strategy for the production of terephthalic acid (TPA) from lignin-derived monomer mixtures, in which redundant, non-uniform substitutes such as methoxy groups are removed and the desired carboxy groups are introduced. This strategy begins with the hydro-treatment of corn-stover-derived lignin oil over a supported molybdenum catalyst to selectively remove methoxy groups. The generated 4-alkylphenols are converted into 4-alkylbenzoic acids by carbonylation with carbon monoxide. The Co-Mn-Br catalyst then oxidizes various alkyl chains into carboxy groups, transforming the 4-alkylbenzoic acid mixture into a single product: TPA. For this route, the overall yields of TPA based on lignin content of corn stover could reach 15.5 wt %, and importantly, TPA with greater than 99 % purity was obtained simply by first decanting the reaction mixture and then washing the solid product with water.
- Song, Song,Zhang, Jiaguang,G?zayd?n, G?kalp,Yan, Ning
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p. 4934 - 4937
(2019/02/24)
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- Effective hydrodeoxygenation of lignin-derived phenols using bimetallic RuRe catalysts: Effect of carbon supports
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We have previously shown that an activated carbon-supported ruthenium catalyst promoted with ReOx (RuRe/AC) is highly active for the hydrodeoxygenation (HDO) of lignin-derived phenols (e.g., guaiacol). In this work, we have investigated the effect of carbon supports on the structure and HDO activity of bimetallic RuRe particles using three different carbon supports, i.e., activated carbon (AC), carbon black (Vulcan carbon, VC), multi-walled carbon nanotube (MWCNT). The MWCNT- and VC-supported catalysts show remarkably enhanced activity and hydrocarbon selectivity for the HDO of a range of phenolic molecules (i.e., guaiacol, eugenol, benzyl phenyl ether) compared to RuRe/AC. STEM-EDS and XPS analyses reveal that bimetallic RuRe particles are more common than monometallic Ru or Re particles in the VC- and MWCNT-supported catalysts, and hexavalent rhenium species are more easily reduced to tetravalent rhenium during the HDO reactions in these catalysts, suggesting that Ru and Re in close proximity are required for the efficient hydrogenolysis of phenols. The formation of bimetallic particles on the AC surface is likely hindered by high microporosity and high surface oxygen functionalities, both of which restrict the mobility of Re and Ru for assembly.
- Jung, Kyung Bin,Lee, Jinho,Ha, Jeong-Myeong,Lee, Hyunjoo,Suh, Dong Jin,Jun, Chul-Ho,Jae, Jungho
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p. 191 - 199
(2017/09/06)
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- Slowing the Kinetics of Alumina Sol–Gel Chemistry for Controlled Catalyst Overcoating and Improved Catalyst Stability and Selectivity
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Catalyst overcoating is an emerging approach to engineer surface functionalities on supported metal catalyst and improve catalyst selectivity and durability. Alumina deposition on high surface area material by sol–gel chemistry is traditionally difficult to control due to the fast hydrolysis kinetics of aluminum-alkoxide precursors. Here, sol–gel chemistry methods are adapted to slow down these kinetics and deposit nanometer-scale alumina overcoats. The alumina overcoats are comparable in conformality and thickness control to overcoats prepared by atomic layer deposition even on high surface area substrates. The strategy relies on regulating the hydrolysis/condensation kinetics of Al(sBuO)3 by either adding a chelating agent or using nonhydrolytic sol–gel chemistry. These two approaches produce overcoats with similar chemical properties but distinct physical textures. With chelation chemistry, a mild method compatible with supported base metal catalysts, a conformal yet porous overcoat leads to a highly sintering-resistant Cu catalyst for liquid-phase furfural hydrogenation. With the nonhydrolytic sol–gel route, a denser Al2O3 overcoat can be deposited to create a high density of Lewis acid–metal interface sites over Pt on mesoporous silica. The resulting material has a substantially increased hydrodeoxygenation activity for the conversion of lignin-derived 4-propylguaiacol into propylcyclohexane with up to 87% selectivity.
- Du, Yuan-Peng,Héroguel, Florent,Luterbacher, Jeremy S.
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-
- Single-step conversion of lignin monomers to phenol: Bridging the gap between lignin and high-value chemicals
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Transformation of lignin into high-value chemicals is hampered by the complexity of monomers obtained from lignin depolymerization. Here we report a strategy, composed of hydro-demethoxylation and de-alkylation reactions, that is able to chemically converge various lignin-derived phenolic monomers into phenol in a single-step. Using 2-methoxy-4-propylphenol as a model compound, Pt/C exhibited the best performance in hydro-demethoxylation reaction affording >80% 4-propylphenol from 2-methoxy-4-propylphenol, while H-ZSM-5 was identified as the most suitable catalyst for de-alkylation, achieving 83% yield of phenol from 4-propylphenol. Since the two catalysts operate under compatible conditions, combining the two catalysts to simultaneously promote both hydro-demethoxylation and de-alkylation reactions was achieved. Configuration of how to organize the catalysts is a critical parameter, where the physical mixture of the two was most effective, providing over 60% phenol from 2-methoxy-4-propylphenol in a single-step.
- Zhang, Jiaguang,Lombardo, Loris,G?zayd?n, G?kalp,Dyson, Paul J.,Yan, Ning
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p. 1445 - 1452
(2018/07/29)
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- On the Reactivity of Dihydro-p-coumaryl Alcohol towards Reductive Processes Catalyzed by Raney Nickel
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There are several established approaches for the reductive fractionation of lignocellulose (e.g., “catalytic upstream biorefining” and “lignin-first” approaches) that lead to a lignin oil product that is composed primarily of dihydro-p-monolignols [e.g., 4-(3-hydroxypropyl)-2-methoxyphenol and 4-(3-hydroxypropyl)-2,6-dimethoxyphenol]. Although effective catalytic methods have been developed to perform reductive or deoxygenative processes on the lignin oil, the influence of the 3-hydroxypropyl substituent on catalyst activity has previously been overlooked. Herein, to better understand the reactivity of the depolymerized lignin oil obtained from catalytic upstream biorefining processes, dihydro-p-coumaryl alcohol was selected as a model compound. Hydrogenation of this species in the presence of Raney Ni with molecular hydrogen led to ring saturation (100 % selectivity) in the absence of hydrodeoxygenation, whereas under hydrogen-transfer conditions with 2-propanol, hydrogenation occurred (≈55 % selectivity) simultaneously with hydrodeoxygenation (≈40 % selectivity). In a broader context, this study sheds light not only on the reactivity of dihydro-p-monolignols but also on the intricacies of the catalytic upstream biorefining reaction network in which these species are revealed to be key intermediates in the formation of less-functionalized p-alkylphenols.
- Calvaruso, Gaetano,Burak, Jorge Augusto,Clough, Matthew T.,Kennema, Marco,Meemken, Fabian,Rinaldi, Roberto
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p. 2627 - 2632
(2017/07/28)
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- PRODUCTION OF 3-ALKYLPHENOLS AND USES THEREOF
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In general the present invention concerns a method for conversion of particular 4-alkyl-2- hydroxyphenols and 4-alkyl-2-alkoxyphenols into 3-alkylphenols. More specifically, this invention relates to a novel process of selectively forming meta-alkyl phenols of various alkylphenols, such as for instance converting the fraction of 4-alkyl-2-hydroxyphenols and 4- alkyl-2-alkoxyphenols into high yields of 3-alkylphenols.
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Page/Page column 20
(2016/12/16)
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- Selective Hydrodeoxygenation of Lignin-Derived Phenols to Cyclohexanols or Cyclohexanes over Magnetic CoNx@NC Catalysts under Mild Conditions
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The hydrodeoxygenation (HDO) of lignin-derived phenols is important to produce the renewable biofuels. Herein, we reported a simple method to prepare magnetic nitrogen-doped carbon supported cobalt nitride catalysts (CoNx@NC) by copyrolysis of cellulose and cobalt nitrate under ammonia atmosphere. The catalysts were prepared at different temperatures and characterized by elemental analysis, atomic absorption spectroscopy (AAS), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and temperature-programmed reduction (TPR). The CoNx@NC-650 (pyrolyzed at 650°C) exhibited the best HDO activity for eugenol conversion among a series of Co-based catalysts. The yield of propylcyclohexanol from eugenol was >99.9% under 2 MPa H2 at 200°C for 2 h. Moreover, a high yield of propylcyclohexane (99.1%) could be achieved when the solid acid HZSM-5 was added to the reaction system. Other lignin-derived phenolic compounds were also investigated and the yield of alkanes was >90%. Based on the mechanism investigation, the catalyst demonstrated a high selectivity to cleave the Caryl-OR bond under mild conditions. (Chemical Equation Presented).
- Liu, Xiaohao,Xu, Lujiang,Xu, Guangyue,Jia, Wenda,Ma, Yanfu,Zhang, Ying
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p. 7611 - 7620
(2016/11/17)
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- Function of metals and supports on the hydrodeoxygenation of phenolic compounds
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Hydrodeoxygenation (HDO) is an important process for removing oxygen from lignin-derived phenolic monomers to obtain chemicals that can be used as fuel or fuel additives. A systematic study is performed to check the effects of supports (acidic, neutral, basic) and noble metals (Pd, Pt, Ru) on the HDO of phenol, guaiacol, and eugenol. Evaluation of the combinations of metals and supports under the similar reaction conditions shows that the metals supported on a highly acidic support (SiO2-Al2O3) yield complete hydrogenation products with the possibility of C-O bond cleavage to achieve a real HDO activity, whereas on a mildly acidic support (γ-Al2O3), a complicated product distribution is achieved, and neutral (C) and basic (HT) supports give restricted hydrogenation activity but yield the products with very high selectivity. On the basis of the results, reaction pathways are suggested and deliberated. The catalysts show reproducible activity in recycle runs. The catalysts are characterized by various techniques (XRD, TEM, TPD, ICP-OES) to establish the catalyst activity-property relationship.
- Deepa, Ayillath K.,Dhepe, Paresh L.
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p. 1573 - 1583
(2015/02/02)
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- Function of Metals and Supports on the Hydrodeoxygenation of Phenolic Compounds
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Hydrodeoxygenation (HDO) is an important process for removing oxygen from lignin-derived phenolic monomers to obtain chemicals that can be used as fuel or fuel additives. A systematic study is performed to check the effects of supports (acidic, neutral, basic) and noble metals (Pd, Pt, Ru) on the HDO of phenol, guaiacol, and eugenol. Evaluation of the combinations of metals and supports under the similar reaction conditions shows that the metals supported on a highly acidic support (SiO2-Al2O3) yield complete hydrogenation products with the possibility of C-O bond cleavage to achieve a real HDO activity, whereas on a mildly acidic support (γ-Al2O3), a complicated product distribution is achieved, and neutral (C) and basic (HT) supports give restricted hydrogenation activity but yield the products with very high selectivity. On the basis of the results, reaction pathways are suggested and deliberated. The catalysts show reproducible activity in recycle runs. The catalysts are characterized by various techniques (XRD, TEM, TPD, ICP-OES) to establish the catalyst activity-property relationship.
- Deepa, Ayillath K.,Dhepe, Paresh L.
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p. 1573 - 1583
(2015/08/24)
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- PROCESS FOR THE CONVERSION OF LIGNIN TO LIQUID HYDROCARBONS
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Process for the conversion of lignin to liquid hydro-carbons comprising: subjecting the lignin to hydrogenolysis in the presence of at least one hydrogenolysis catalyst, at a temperature ranging from 250° C. to 350° C., preferably ranging from 290° C. to 320 ° C., so as to obtain depolymerized lignin; subjecting said depolymerized lignin to hydrotreating so as to obtain a mixture of liquid hydrocarbons. Said liquid hydrocarbons can be used as such (biofuels) for the production of reformulated gasolines, or they can be used for the production of gasolines or of gas oils through conventional refining processes.
- -
-
Paragraph 0153-0168
(2013/03/26)
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- Hydrogenolysis of lignosulfonate into phenols over heterogeneous nickel catalysts
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We report a strategy for the catalytic conversion of lignosulfonate into phenols over heterogeneous nickel catalysts. Aryl-alkyl bonds (C-O-C) and hydroxyl groups (-OH) are hydrogenated to phenols and alkanes, respectively, without disturbing the arenes. The catalyst is based on a naturally abundant element, and is recyclable and reusable. The Royal Society of Chemistry 2012.
- Song, Qi,Wang, Feng,Xu, Jie
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p. 7019 - 7021
(2012/08/14)
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- Structural basis for the properties of two single-site proline mutants of CYP102A1 (P450BM3)
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The crystal structures of the haem domains of Ala330Pro and Ile401Pro, two single-site proline variants of CYP102A1 (P450BM3) from Bacillus megaterium, have been solved. In the A330P structure, the active site is constricted by the relocation of the Pro329 side chain into the substrate access channel, providing a basis for the distinctive C-H bond oxidation profiles given by the variant and the enhanced activity with small molecules. I401P, which is exceptionally active towards non-natural substrates, displays a number of structural similarities to substrate-bound forms of the wild-type enzyme, notably an off-axial water ligand, a drop in the proximal loop, and the positioning of two I-helix residues, Gly265 and His266, the reorientation of which prevents the formation of several intrahelical hydrogen bonds. Second-generation I401P variants gave high in vitro oxidation rates with non-natural substrates as varied as fluorene and propane, towards which the wild-type enzyme is essentially inactive. The substrate-free I401P haem domain had a reduction potential slightly more oxidising than the palmitate-bound wild-type haem domain, and a first electron transfer rate that was about 10 % faster. The electronic properties of A330P were, by contrast, similar to those of the substrate-free wild-type enzyme. Protein evolution with proline: The crystal structures of two contrasting single-site proline mutants of CYP102A1 (P450BM3) have been solved. The two mutations combine to give a variant that shows substantially enhanced catalytic activity with small non-natural substrates (see graph).
- Whitehouse, Christopher J. C.,Yang, Wen,Yorke, Jake A.,Rowlatt, Benjamin C.,Strong, Anthony J. F.,Blanford, Christopher F.,Bell, Stephen G.,Bartlam, Mark,Wong, Luet-Lok,Rao, Zihe
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experimental part
p. 2549 - 2556
(2011/10/09)
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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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- Evolved CYP102A1 (P450BM3) variants oxidise a range of non-natural substrates and offer new selectivity options
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The evolution of CYP102A1 variants with enhanced activity and altered specificity characteristics. The Royal Society of Chemistry.
- Whitehouse, Christopher J. C.,Bell, Stephen G.,Tufton, Henry G.,Kenny, Richard J. P.,Ogilvie, Lydia C. I.,Wong, Luet-Lok
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p. 966 - 968
(2008/09/21)
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- One step hair coloring compositions using salts
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A hair coloring composition comprising the following two compositions which are mixed just prior to application to the hair: (a) a composition comprising a water-soluble peroxygen oxidizing agent; and (b) a composition comprising one or more oxidative hair coloring agents selected from the group consisting of an aromatic diamine, an amino phenol, a naphthol, a polyhydric phenol, a catechol and mixtures thereof; wherein the composition comprising one or more oxidative hair coloring agents further comprises al least one water soluble carbonate releasing salts; and optionally a water soluble ammonium salt, is described.
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- Synthesis and Antimicrobial Activity of Hydroxyalkyl- and Hydroxyacyl-phenols and Their Benzyl Ethers
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New phenolic compounds with hydrophilic side chains were prepared from 4-benzyloxybenzaldehyde and alkenyl magnesium bromides, followed by Sharpless dihydroxylation and hydrogenolytic removal of the benzyl group. The resulting compounds were tested in an agar diffusion assay against gram positive bacteria, gram negative bacteria, and against the fungi Candida glabrata and Aspergillus niger.
- Krauss, J.,Unterreitmeier, D.
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- Process for synthesis of 5-alkylbenzodioxoles
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The following description refers to a new process for the synthesis of 5-alkylated benzo[1,3]dioxole, comprising the following steps in sequence: catalytic hydrogenation of 4-acylphenol; acylation; displacement catalysed by Lewis acids; treatment with an inorganic basic compound and hydrogen peroxide; reaction with alkyl dihalides or dialkoxyalkanes. The process described herein, which yields 5-alkylbenzo[1,3]dioxoles, is economic and can be easily scaled up to industrial size.
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- Process for the synthesis of 5-allybenzodioxoles
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The following description refers to a new process for the synthesis of 5-alkylated benzo[1,3]dioxole, consisting in the following steps in sequence: catalytic hydrogenation of 4-acylphenol; acylation; displacement catalysed by Lewis acids; treatment with an inorganic basic compound and hydrogen peroxide; reaction with alkyl dihalides or dialkoxyalkanes. The process described herein, which yields 5-alkylbenzo[1,3]dioxoles, is economic and can be easily scaled up to industrial size.
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- O-alkylation of phenolic compounds via rare earth orthophosphate catalysts
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Carbocyclic/aliphatic ethers, for example anisole, quaicol, guaethol, p-methoxyphenol and ethylene dioxybenzene, are selectively prepared, in good yield, by reacting a phenolic compound, for example a phenol, hydroquinone, pyrocatechin, naphthol, or the like, with an alcohol, for example methanol, ethanol, isopropanol, ethylene glycol, etc., in gaseous phase, in the presence of a catalytically effective amount of a trivalent rare earth metal orthophosphate, for example a lanthanum, cerium or samarium orthophosphate, optionally doped with an alkali or alkaline earth metal, preferably cesium.
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- STRUCTURE AND REACTIVITY OF GLYCOSIDES. III. KINETICS AND MECHANISM OF THE ALKALINE HYDROLYSIS OF O-ARYL (2,3,4,6-TETRA-O-ACETYL-β-D-GLUCOPYRANOSYL)THIOCARBAMATES IN WATER-DIOXANE SOLUTIONS
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The kinetics were studied and the rate constants of hydrolysis were determined in water-dioxane alkaline solutions at 20 deg C and pH 10.87 of a number of O-aryl (tetra-O-acetyl-β-D-glucopyranosyl)thiocarbamates substituted in the aromatic ring.Logarithms of the rate constants observed correlate with the pKa values of the corresponding phenols and with a set of Hammett constants.The temperature dependence of the rate constants of the hydrolysis of O-(4-propylphenyl) (tetra-O-acetyl-β-D-glucopyranosyl)thiocarbamate was determined, and its activation parameters were calculated.An intermediate formed in the hydrolysis of a glycosylthiocarbamate was identified as a glycosyl isothiocyanate on the basis of the electronic spectra and TLC.
- Petushkova, S. G.,Pavlov, A. E.,Sokolov, V. M.,Zakharov, V. I.,Lavrent'ev, A. N.
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p. 796 - 798
(2007/10/02)
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- Acid-catalyzed amino-migration of O-phenylhydroxylamines
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The mechanism of amino-migration of O-phenylhydroxylamine (1a) was studied. It was found that 1 rearranges to give 2-aminophenol (50%) and 4-aminophenol (7%) in trifluoroacetic acid (TFA). The predominance of the ortho rearrangement of 1 clearly distinguishes this process from the Bamberger rearrangement. From cross-coupling experiments employing stable isotopes, it was clarified that the ortho rearrangement proceeds intramolecularly and the para rearrangement involves both intra- and intermolecular processes. Good first-order kinetics were obtained for the rearrangement. The Hammett plot (σ+) with a large negative slope (ρ = -7.8) indicates that initial heterolytic N-O bond cleavage of 1 occurs and generates a positive charge on the oxygen atom with considerable delocalization into the aromatic ring. An ion-molecule pair involving a phenoxenium ion and an ammonia molecule as an intermediate rationalizes all of the results. In this pair, intramolecular combination to the ortho position proceeds preferentially over that to the para position. Formation of catechol and hydroquinone can be explained in terms of nucleophilic attack of TFA on the phenoxenium ion in a solvent-separated pair.
- Haga, Naoki,Endo, Yasuyuki,Kataoka, Ken-Ichiro,Yamaguchi, Kentaro,Shudo, Koichi
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p. 9795 - 9806
(2007/10/02)
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- Catalysis of the Debromination of 4-Alkyl-4-bromo-2,5-cyclohexadienones in Aqueous Solution by α-Cyclodextrin
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α-Cyclodextrin (CD) has little or no effect on the rates of enolization of transient 4-bromo-2,5-cyclohexadienones (2), formed during the aqueous bromination of alkylphenols.In contrast, saturation kinetics and large catalytic effect are observed for the debromination of the title dienones (4), formed by ipso bromine attack on 4-alkylphenols (alkyl = Me, Et, i-Pr, n-pr, t-Bu, 3,4-diMe).With the exception of the n-propyl case, the extent of the catalysis kc/ku = 23-78) and the dissociation constant of the CD.dienone complexes (Kd = 2.32-4.83 mM) show surprisingly little variation for the different alkyl groups.The simplest interpretation of the results is that the CD-catalyzed debromination reaction involves attack by free bromide ion on the CD.dienone complex.However, the kinetically equivalent pathway, the reaction between the free dienone 4 and the CD complex of bromide ion, is much more consistent with the low sensitivity of the catalysis to the length and size of the different alkyl groups.For this mechanism the rate enhancements are much larger (2400-4600) and almost constant.They imply that Br- in its CD complex is a stronger nucleophile than bromide ion that is completely solvated by water.The preferred mechanism is the microscopic reverse of that postulated for the CD-catalyzed bromination of phenols.The common transition state for the ipso bromination of 5 (R=Me) and the debromination of 4 (R=Me) is strongly bound by CD (Kd ca. 4.5 1E-5 M).
- Tee, Oswald S.,Bennett, Janice M.
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p. 3226 - 3230
(2007/10/02)
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- The Behavior of 4-Alkyl-4-bromo-2,5-cyclohexadienones Formed during the Aqueous Bromination of p-Alkylphenols
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The title compounds ("ipso-dienones") 5 have been observed during the reaction of bromine with six p-alkylphenols 4 (R = Me, Et, n-Pr, i-Pr, t-Bu, 3,4-Me2) in aqueous solutions of pH 0-3.Their formation by ipso bromine attack on 4 accounts for about 10percent of the initial consumption of bromine.The decomposition of 5, which is catalyzed by H+ and by Br-, is attributed to debromination.The rates of this reaction and of the attack of bromine on 4 are not very sensitive to the nature of the alkyl substituents.Studies of the behavior of 5 (R = Me) in buffers give curved buffer plots which provide additional support for the debromination mechanism and also demonstrate general acid catalysis.Decomposition of 5 (R = Me) in the presence of a trap for liberated bromine give straight buffer plots from which a Broensted α ca. 0.27 is deduced.The ipso-dienone 8, derived from 5-methylsalicylic acid, shows intramolecular catalysis by the carboxyl group (EM = 58 M) and no catalysis by buffer acids.
- Tee, Oswald S.,Iyengar, N. Rani,Bennett, Janice M.
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p. 2585 - 2589
(2007/10/02)
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- Preparation and Reactions of Dianions from the Cresols
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With n-BuLi/KO-t-Bu, protons are removed from the hydroxyl and methyl groups of cresols 5 to give dianions 6 in yields of 85percent (ortho), 95percent (meta), and 42percent (para).These dianions react with alkyl halides, Me3SiCl, Bu3SnCl, CO2, and oxidizing agents at carbon only and with dialkyl sulfates at both carbon and oxygen.Thus phenol derivatives bearing primary alkyl groups can be prepared from the corresponding methylphenols via dianions 6.
- Bates, Robert B.,Siahaan, Teruna J.
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p. 1432 - 1434
(2007/10/02)
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- SYNTHESIS AND MESOMORPHIC PROPERTIES OF THE HOMOLOGOUS SERIES OF DI-(4 ' -N-ALKYLPHENYL)-TRANS-CYCLOHEXANE-1,4-DICARBOXYLATES.
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THE HOMOLOGUOUS SERIES OF DI-(4 ' N-ALKYLPHENYL)-TRANS-CYCLOHEXANE-1,4-DICARBOXYLATES IN WHICH THE ALKYL GROUP IS C//1-C//1//2 WAS PREPARED BY ESTERIFICATION OF TRANS-1,4-CYCLOHEXANEDICARBOXYLIC ACID OR DICARBONYL CHLORIDE WITH 4-ALKYLPHENOLS. MESOMORPHIC PROPERTIES AND PHASE TRANSITIONS AS DETERMINED BY HOT-STAGE POLARIZING MICROSCOPY AND DSC ARE DISCUSSEDIN RELATIONSHIP TO VARIOUS STRUCTURAL FEATURES. COMPARISONSOF THESE PROPERTIES WITH THOSE FOR THE CORRESPONDING ALKOXYSERIES AND THE ANALOGOUS TEREPHTHALIC ACID DIESTERS ARE ALSO PRESENTED AND DISCUSSED.
- NEUBERT,STAHL,CLINE
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- REACTIONS RETRODIENIQUES-XI SYNTHESE DE COMPOSES POLYINSATURES REACTIFS PAR DOUBLE REACTION DE RETRO-DIELS-ALDER
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Double retro-Diels-Alder cleavage by flash thermolysis gave the new, unstable polyunsaturated ketones and hydrocarbons 1-5 for which NMR, IR and UV spectra at low temperature are reported.The Diels-Alder adducts of compounds 1-3 with various dienes, the 1,6-additions of several nucleophilic agents with 4, and the isomerisation of 5 in p-ethynylstyrene support the proposed structures.
- Lasne, M. C.,Ripoll, J. L.,Denis, J. M.
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p. 503 - 508
(2007/10/02)
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- Oxidations of Cyclopropane, Methylcyclopropane, and Arenes with the Mono-oxygenase System from Methylococcus capsulatus
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The mono-oxygenase system from Methylococcus capsulatus oxidises cyclopropane to cyclopropanol, methylcyclopropane to cyclopropylmethanol, and monosubstituted benzenes to para-substituted phenols (with accompanying NIH shift).
- Dalton, Howard,Golding, Bernard T.,Waters, Barry W.,Higgins, Raymond,Taylor, John A.
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p. 482 - 483
(2007/10/02)
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- Alumina-Catalyzed Reactions of Hydroxyarenes and Hydroaromatic Ketones. 9. Reaction of Phenol with 1-Propanol
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At 250-350 deg C in the presence of alumina, phenol (1) reacts with excess 1-propanol to give mainly (>90percent) C-alkylation to form mono- to penta-n-propylphenols plus some O-alkylations to form n-propyl aryl ethers. The principal component of the product mixture from 1 is 2,6-di-n-propylphenol (26-50 mol percent yield). With 4-n-propylphenol as substrate (instead of 1), tri-, tetra-, and penta-n-propylphenols are formed in 48-79percent combined yield. On the average, only 3percent of the total C3H7 groups in the product mixture are isopropyl ones. Deoxygenation is not observed. It is proposed that the principal products result from an SN2-type reaction mechanism which involves nucleophilic attack (variously by C-2, C-4, C-6, or O) of an adsorbed ambident phenoxide ion onto C-1 of an adsorbed n-propoxide group. n-Propylation at C-3 and C-5 of the phenol ring results from surface-catalyzed dienone-phenol rearrangement.Isopropylation may occur via a side reaction of SN1 type.
- Klemm, LeRoy H.,Taylor, Dennis R.
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p. 4320 - 4326
(2007/10/02)
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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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- Enzyme-activated oxidative process for coloring hair
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An enzyme-based oxidative process for coloring hair wherein the hair is exposed to a solution having a pH of about 4 to about 10 and containing hydrogen peroxide, soybean peroxidase enzyme and one or more oxidation dye precursors.
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