- Bioconversion of ferulic acid to 4-vinylguaiacol and 4-ethylguaiacol and of 4-vinylguaiacol to 4-ethylguaiacol by halotolerant yeasts belonging to the genus Candida
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In order to examine the genesis of the characteristic flavors of soy sauce and miso, seven novel halotolerant yeast strains of two types, which showed convertibility of ferulic acid (FA) to 4-vinylguaiacol (4-VG) and to 4-ethylguaiacol (4-EG), were isolated from miso-koji and miso pastes. Two of these strains were identified as Candida guilliermondii (anamorph of Pichia guilliermondii), and Candida fermentati (anamorph of Pichia caribbica), based on sequence analyses of a partial 26S ribosomal RNA gene and the region of internal transcribed spacers 1 and 2, and the 5.8S ribosomal RNA gene. Moreover, we also found three Candida etchellsii strains which showed convertibility of FA to 4-VG, but not to 4-EG, and two atypical strains of Candida versatilis which showed no convertibility of FA to 4-VG, but did show convertibility of 4-VG to 4-EG from soy sauce mashes. The bioconversion pathway from FA to 4-EG via 4-VG in halotolerant yeasts and bacteria is discussed.
- Suezawa, Yasuhiko,Suzuki, Motofumi
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- Development and scaling-up of the fragrance compound 4-ethylguaiacol synthesis via a two-step chemo-enzymatic reaction sequence
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The transformation of (abundant) oxygenated biomass-derived building blocks via chemo-enzymatic methods is a valuable concept for accessing useful compounds, as it combines the high selectivity of enzymes and the versatility of chemical catalysts. In this work, we demonstrate a straightforward combination of a phenolic acid decarboxylase (PAD) and palladium on charcoal (Pd/C) that affords the flavor compound 4-ethylguaiacol from ferulic acid. The use of a two-phase system proved to be advantageous in terms of enzyme activity, stability, and volumetric productivity and allows us to carry out the hydrogenation step directly in the organic layer containing exclusively the intermediate, vinylguaiacol. The enzymatic decarboxylation step in the biphasic system afforded 89% conversion of 100 mM (19 g L-1) ferulic acid with an isolated yield of 75%. By extracting 4- vinylguaiacol continuously into the organic phase, conversion was enhanced to 92% using 170 mM (33 g L-1) ferulic acid, which was only possible in the continuous extraction and distillation setup developed. The reaction cascade (PAD-Pd/C) is demonstrated at gram scale, affording the target product 4-ethylguaiacol (1.1 g) in 70% isolated yield in a two-step two-pot process. The enzymatic step was characterized in detail to overcome major constraints, and the process favorably compares in terms of the environmental impact with traditional approaches.
- Pesci, Lorenzo,Baydar, Maik,Glueck, Silvia,Faber, Kurt,Liese, Andreas,Kara, Selin
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- Degradation of bisphenol A and acute toxicity reduction by different thermo-tolerant ascomycete strains isolated from arid soils
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Four different laccase-producing strains were isolated from arid soils and used for bisphenol A (BPA) degradation. These strains were identified as Chaetomium strumarium G5I, Thielavia arenaria CH9, Thielavia arenaria HJ22 and Thielavia arenaria SM1(III) by internal transcribed spacer 5.8 S rDNA analysis. Residual BPA was evaluated by HPLC analysis during 48 h of incubation. A complete removal of BPA was observed by the whole cell fungal cultures within different times, depending on each strain. C. strumarium G5I was the most efficient degrader, showing 100% of removal within 8 h of incubation. The degradation of BPA was accompanied by the production of laccase and dye decolorizing peroxidase (DyP) under degradation conditions. The presence of aminobenzotriazole (ABT) as an inhibitor of cytochrome P450s monooxygenases (CYP) demonstrated a slight decrease in BPA removal rate, suggesting the effective contribution of CYP in the conversion. The great involvement of laccase in BPA transformation together with cell-associated enzymes, such as CYP, was supported by the identification of hydroxylated metabolites by ultra-high performance liquid chromatography-mass spectroscopy (UHPLC-MS). The metabolic pathway of BPA transformation was proposed based on the detected metabolites. The acute toxicity of BPA and its products was investigated and showed a significant reduction, except for T. arenaria SM1(III) that did not caused reduction of toxicity (IC50 8%), possibly due to the presence of toxic metabolites. The results of the present study point out the potential application of the isolated ascomycetes in pollutant removal processes, especially C. strumarium G5I as an efficient degrader of BPA.
- Mtibaà, Rim,Olicón-Hernández, Dario Rafael,Pozo, Clementina,Nasri, Moncef,Mechichi, Tahar,González, Jesus,Aranda, Elisabet
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- Ceria-promoted Co@NC catalyst for biofuel upgrade: synergy between ceria and cobalt species
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Ceria-promoted Co@NC (NC, N doped carbon) catalysts are prepared by pyrolysis of biomass materials. Characterization results indicate that ceria and Co species facilitate the distribution of each other due to the formation of a Ce-O-Co solid solution. The specific surface area of the catalyst increased from 378.77 to 537.7 m2g?1viathe introduction of ceria. The electron transfer from Co to Ce further enhanced their interaction, and Co species facilitate the formation of more defective oxygen vacancies on ceria, which are beneficial to the activities of catalytic hydrogenation and catalytic transfer hydrogenation (CTH), respectively. Thus, Co/Ce@NC (0.99% Co loading) pyrolyzed at 850 °C exhibits excellent performance in the hydrodeoxygenation (HDO) of vanillin with high metal utilization. Catalytic hydrogenation and CTH coexisted in the presence of H2and ethanol, and >99% yield of creosol can be obtained in each of them. The reaction processes are monitored. No intermediate is found in aqueous media, while ethoxymethyl-4-methoxy-2-phenol is detected in ethanol. Moreover, Co/Ce@NC presents outstanding stability and general applicability. This work provides new insights into the construction of M@NC (M, metal) catalysts and the HDO process of biofuel upgrade.
- Wang, Bowei,Gao, Ruixiao,Zhang, Dan,Zeng, Yuyao,Zhang, Fangying,Yan, Xilong,Li, Yang,Chen, Ligong
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supporting information
p. 8541 - 8553
(2021/04/12)
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- Selective upgrading of biomass-derived benzylic ketones by (formic acid)–Pd/HPC–NH2 system with high efficiency under ambient conditions
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Upgrading biomass-derived phenolic compounds provides a valuable approach for the production of higher-value-added fuels and chemicals. However, most established catalytic systems display low hydrodeoxygenation (HDO) activities even under harsh reaction conditions. Here, we found that Pd supported on –NH2-modified hierarchically porous carbon (Pd/HPC–NH2) with formic acid (FA) as hydrogen source exhibits unprecedented performance for the selective HDO of benzylic ketones from crude lignin-derived oxygenates. Designed experiments and theoretical calculations reveal that the H+/H? species generated from FA decomposition accelerates nucleophilic attack on carbonyl carbon in benzylic ketones and the formate species formed via the esterification of intermediate alcohol with FA expedites the cleavage of C–O bonds, achieving a TOF of 152.5 h?1 at 30°C for vanillin upgrading, 15 times higher than that in traditional HDO processes (~10 h?1, 100°C–300°C). This work provides an intriguing green route to produce transportation fuels or valuable chemicals from only biomass under mild conditions.
- Chen, Yuzhuo,Chen, Zhirong,Gong, Yutong,Mao, Shanjun,Ning, Honghui,Wang, Yong,Wang, Zhenzhen
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p. 3069 - 3084
(2021/11/16)
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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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- Method for hydrolyzing diarylether compound to generate aryl phenol compound
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The invention discloses a method for hydrolyzing a diarylether compound to generate an arylphenol compound. According to the method, visible light is utilized to excite a photosensitizer for catalysis. In a reaction solvent, the raw material in the formula (1) breaks a C (sp2)-O bond under the auxiliary action of acid, and hydrolysis is performed to obtain the bimolecular aryl phenol compounds in the formula (3) and the formula (4). The method can catalyze the reaction at room temperature, is green and environment-friendly, and is easy to operate; the universality is wide, the reaction yield is relatively high, and the tolerance of functional groups is strong; the synthesis method not only can realize small-scale hydrolysis conversion of various diarylether compounds, but also can realize hydrolysis of herbicidal ether, triclosan and a lignin template substrate, and even can realize large-scale hydrolysis of triclosan and the lignin template substrate to realize gram-level degradation. A new strategy is provided for recovering phenol derivatives through lignin hydrolysis, degrading pesticides and purifying wastewater containing a degerming agent or herbicide. The method has wide application prospect and use value.
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Paragraph 0162-0166
(2021/09/29)
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- Thiols Act as Methyl Traps in the Biocatalytic Demethylation of Guaiacol Derivatives
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Demethylating methyl phenyl ethers is challenging, especially when the products are catechol derivatives prone to follow-up reactions. For biocatalytic demethylation, monooxygenases have previously been described requiring molecular oxygen which may cause oxidative side reactions. Here we show that such compounds can be demethylated anaerobically by using cobalamin-dependent methyltransferases exploiting thiols like ethyl 3-mercaptopropionate as a methyl trap. Using just two equivalents of this reagent, a broad spectrum of substituted guaiacol derivatives were demethylated, with conversions mostly above 90 %. This strategy was used to prepare the highly valuable antioxidant hydroxytyrosol on a one-gram scale in 97 % isolated yield.
- Grimm, Christopher,Kroutil, Wolfgang,Pompei, Simona,Schiller, Christine,Schober, Lukas
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supporting information
p. 16906 - 16910
(2021/07/02)
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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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- Atomically Dispersed Co Catalyst for Efficient Hydrodeoxygenation of Lignin-Derived Species and Hydrogenation of Nitroaromatics
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Single-atom catalysts (SACs) have attracted much attention due to their outstanding catalytic performance in heterogeneous catalysis. Here, we report a template sacrificial method to fabricate an atomically dispersed Co catalyst; three kinds of silica templates with different microstructures (MCM-41, SBA-15, and FDU-12) were employed and the effect of pore structure of the templates on the dispersity of Co was investigated. The catalysts fabricated with different templates presented different Co dispersities, leading to distinguishing catalytic performance. The optimized Co1?NC-(SBA) catalyst with atomically dispersed Co displayed outstanding catalytic activity for the hydrodeoxygenation (HDO) of lignin-derived species as well as the hydrogenation of various nitroaromatics. The reaction mechanism of the HDO of vanillin was investigated by using density functional theory calculations as well.
- Du, Congcong,Gao, Shutao,Gao, Yongjun,Huang, Jianyu,Meng, Tao,Qiao, Yuqing,Shang, Ningzhao,Shen, Tongde,Wang, Chun,Wang, Haijun,Wang, Junmin,Wang, Zhi,Wu, Qiuhua,Zhang, Longkang
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p. 8672 - 8682
(2020/09/18)
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- Structural features and antioxidant activities of Chinese quince (Chaenomeles sinensis) fruits lignin during auto-catalyzed ethanol organosolv pretreatment
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Chinese quince fruits (Chaenomeles sinensis) have an abundance of lignins with antioxidant activities. To facilitate the utilization of Chinese quince fruits, lignin was isolated from it by auto-catalyzed ethanol organosolv pretreatment. The effects of three processing conditions (temperature, time, and ethanol concentration) on yield, structural features and antioxidant activities of the auto-catalyzed ethanol organosolv lignin samples were assessed individually. Results showed the pretreatment temperature was the most significant factor; it affected the molecular weight, S/G ratio, number of β-O-4′ linkages, thermal stability, and antioxidant activities of lignin samples. According to the GPC analyses, the molecular weight of lignin samples had a negative correlation with pretreatment temperature. 2D-HSQC NMR and Py-GC/MS results revealed that the S/G ratios of lignin samples increased with temperature, while total phenolic hydroxyl content of lignin samples decreased. The structural characterization clearly indicated that the various pretreatment conditions affected the structures of organosolv lignin, which further resulted in differences in the antioxidant activities of the lignin samples. These results can be helpful for controlling and optimizing delignification during auto-catalyzed ethanol organosolv pretreatment, and they provide theoretical support for the potential applications of Chinese quince fruits lignin as a natural antioxidant in the food industry.
- Cheng, Xi-Chuang,Guo, Xin-Ran,Liu, Hua-Min,Liu, Yu-Lan,Qin, Zhao,Wang, Xue-De
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p. 4348 - 4358
(2020/09/22)
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- Regioselectivity of Cobalamin-Dependent Methyltransferase Can Be Tuned by Reaction Conditions and Substrate
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Regioselective reactions represent a significant challenge for organic chemistry. Here the regioselective methylation of a single hydroxy group of 4-substituted catechols was investigated employing the cobalamin-dependent methyltransferase from Desulfitobacterium hafniense. Catechols substituted in position four were methylated either in meta- or para-position to the substituent depending whether the substituent was polar or apolar. While the biocatalytic cobalamin dependent methylation was meta-selective with 4-substituted catechols bearing hydrophilic groups, it was para-selective for hydrophobic substituents. Furthermore, the presence of water miscible co-solvents had a clear improving influence, whereby THF turned out to enable the formation of a single regioisomer in selected cases. Finally, it was found that also the pH led to an enhancement of regioselectivity for the cases investigated.
- Pompei, Simona,Grimm, Christopher,Farnberger, Judith E.,Schober, Lukas,Kroutil, Wolfgang
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p. 5977 - 5983
(2020/10/06)
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- Selective hydrodeoxygenation of hydroxyacetophenones to ethyl-substituted phenol derivatives using a FeRu?SILP catalyst
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The selective hydrodeoxygenation of hydroxyacetophenone derivatives is achieved opening a versatile pathway for the production of valuable substituted ethylphenols from readily available substrates. Bimetallic iron ruthenium nanoparticles immobilized on an imidazolium-based supported ionic liquid phase (Fe25Ru75?SILP) show high activity and stability for a broad range of substrates without acidic co-catalysts. This journal is
- Bordet, Alexis,Goclik, Lisa,Leitner, Walter,Offner-Marko, Lisa
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supporting information
p. 9509 - 9512
(2020/09/02)
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- Combined lignin defunctionalisation and synthesis gas formation by acceptorless dehydrogenative decarbonylation
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The valorization of lignin, consisting of various phenylpropanoids building blocks, is hampered by its highly functionalized nature. The absence of the γ-carbinol group in an unnatural C2 β-O-4 motif compared to the native lignin C3 β-O-4 motif provides great opportunities for developing new valorization routes. Thus efficient defunctionalisation approaches that transform the C3 β-O-4 motif into a simplified C2 β-O-4 motif are of interest. Based on a study with a series of model compounds, we established a feasible application of an iridium-catalysed acceptorless dehydrogenative decarbonylation method to efficiently remove the γ-carbinol group in a single step. This defunctionalisation generates valuable synthesis gas, which can be collected as a reaction product. By this direct catalytic transformation, a yield of ~70percent could be achieved for a C3 β-O-4 model compound that was protected from undergoing retro-aldol cleavage by alkoxylation of the benzylic secondary alcohol in the α position. A phenylcoumaran model compound containing a γ-carbinol group as well as a benzylic primary alcohol also proved to be reactive under dehydrogenative decarbonylation conditions, which can further contribute to the reduction of the structural complexity of lignin. Notably, the liberation of synthesis gas was confirmed and the signals for the defunctionalized C2 β-O-4 motif were observed when this dehydrogenative decarbonylation approach was applied on organosolv lignins. This selective defunctionalized lignin in conjunction with the formation of synthesis gas has the potential to enhance the development of profitable and sustainable biorefineries.
- Deuss, Peter. J.,Lahive, Ciaran W.,Zhang, Zhenlei,Zijlstra, Douwe S.
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p. 3791 - 3801
(2020/07/14)
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- Selective catalytic transformation of lignin with guaiacol as the only liquid product
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Guaiacol is an important feedstock for producing various high-value chemicals. However, the current production route of guaiacol relies heavily on fossil resources. Using lignin as a cheap and renewable feedstock to selectively produce guaiacol has great potential, but it is a challenge because of its heterogeneity and inert reactivity. Herein, we discovered that La(OTf)3 could catalyze the transformation of lignin with guaiacol as the only liquid product. In the reaction, La(OTf)3 catalyzed the hydrolysis of lignin ether linkages to form alkyl-syringol and alkyl-guaiacol, which further underwent decarbonization and demethoxylation to produce guaiacol with a yield of up to 25.5 wt%, and the remaining residue was solid. In the scale-up experiment, the isolated yield of guaiacol reached up to 21.2 wt%. To our knowledge, this is the first work to produce pure guaiacol selectively from lignin. The bio-guaiacol may be considered as a platform to promote lignin utilization.
- Shen, Xiaojun,Meng, Qinglei,Mei, Qingqing,Liu, Huizhen,Yan, Jiang,Song, Jinliang,Tan, Dongxing,Chen, Bingfeng,Zhang, Zhanrong,Yang, Guanying,Han, Buxing
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p. 1347 - 1352
(2020/02/15)
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- Guaiacol demethoxylation catalyzed by Re2O7 in ethanol
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Re2O7 is used to convert guaiacol in alcohols at 280–320 °C. In ethanol, guaiacol is deoxygenated and alkylated, and the major products are phenol and alkylphenols (including ethylphenol, diethylphenol, diisopropylphenol, di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol), accounting for 97 mol% of all products after 6 hour reaction at 320 °C. Both catechol and phenol are the intermediates of guaiacol demethoxylation. Among the substituents, ethyl is directly provided by ethanol while isopropyl and tert-butyl are formed by the addition of methyl to ethyl step by step. In addition, Re2O7 has negligible activity for the saturation of benzene ring so it does not cause considerable over-consumption of reductant. The actual catalyst for guaiacol demethoxylation is likely a ReIV?VI species.
- Yan, Fei,Sang, Yushuai,Bai, Yunfei,Wu, Kai,Cui, Kai,Wen, Zhe,Mai, Fuhang,Ma, Zewei,Yu, Linhao,Chen, Hong,Li, Yongdan
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p. 231 - 237
(2019/08/12)
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- Chemodivergent hydrogenolysis of eucalyptus lignin with Ni@ZIF-8 catalyst
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Reductive catalytic fractionation (RCF) of lignocellulosic biomass, that is depolymerization of the native lignin component into well-defined monomeric phenols in the first step, offers an opportunity to utilize entire biomass components. Herein, we report that Ni@ZIF-8 can serve as a chemodivergent catalyst in RCF of eucalyptus sawdust, thus selectively producing phenolic compounds having either a propyl or propanol end-chain under different reaction conditions. In both cases, high yields of lignin monomers and a high degree of delignification were achieved, next to well-preserved carbohydrate pulp suitable for further processing. A mechanistic study using model compounds indicated that the dehydroxylation at the γ-position of the β-O-4 structure may be involved in the selectivity-controlling step.
- Liu, Xue,Li, Helong,Xiao, Ling-Ping,Sun, Run-Cang,Song, Guoyong
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supporting information
p. 1498 - 1504
(2019/03/26)
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- Catalytic activation of unstrained C(aryl)–C(aryl) bonds in 2,2′-biphenols
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Transition metal catalysis has emerged as an important means for C–C activation that allows mild and selective transformations. However, the current scope of C–C bonds that can be activated is primarily restricted to either highly strained systems or more polarized C–C bonds. In contrast, the catalytic activation of non-polar and unstrained C–C moieties remains an unmet challenge. Here we report a general approach for the catalytic activation of the unstrained C(aryl)–C(aryl) bonds in 2,2′-biphenols. The key is to utilize the phenol moiety as a handle to install phosphinites as a recyclable directing group. Using hydrogen gas as the reductant, monophenols are obtained with a low catalyst loading and high functional group tolerance. This approach is also applied to the synthesis of 2,3,4-trisubstituted phenols. A further mechanistic study suggests that the C–C activation step is mediated by a rhodium(i) monohydride species. Finally, a preliminary study on breaking the inert biphenolic moieties in lignin models is illustrated.
- Zhu, Jun,Wang, Jianchun,Dong, Guangbin
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- Effects of Sugars, Furans, and their Derivatives on Hydrodeoxygenation of Biorefinery Lignin-Rich Wastes to Hydrocarbons
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Hydrodeoxygenation of biorefinery lignin-rich wastes to jet fuel hydrocarbons offers a significant opportunity for enhancing the overall operational efficiency, carbon conversion efficiency, economic viability, and sustainability of biofuels production. However, these wastes usually mainly contain lignin with sugars, furans, and their derivatives as “impurities”. Although several factors, including reactant structure, solvents, or the decreased ratio of catalyst to reactant, could be responsible for the jet fuel hydrocarbons yield loss, we found evidence that glucose, xylose, and 5-hydroxymethylfurfural dramatically decreased conversion yields. For example, xylose and glucose lowered the final hydrocarbon yield by 78 and 63 %, respectively. The results revealed that these compounds could suppress metal catalysts and inhibit lignin depolymerization and hydrodeoxygenation (HDO) reactions thus decrease yields of jet fuel range hydrocarbons from biomass-derived lignin. The first-principles calculations and TGA results from spent catalysts validated these findings.
- Wang, Hongliang,Duan, Yuhua,Zhang, Qian,Yang, Bin
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p. 2562 - 2568
(2018/08/01)
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- Highly selective hydrogenation and hydrogenolysis using a copper-doped porous metal oxide catalyst
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A copper-doped porous metal oxide catalyst in combination with hydrogen shows selective and quantitative hydrogenolysis of benzyl ketones and aldehydes, and hydrogenation of alkenes. The approach provides an alternative to noble-metal catalysed reductions and stoichiometric Wolff-Kishner and Clemmensen methods.
- Petitjean, Laurene,Gagne, Raphael,Beach, Evan S.,Xiao, Dequan,Anastas, Paul T.
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p. 150 - 156
(2015/12/31)
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- Chemo- and Regioselective Hydrogenolysis of Diaryl Ether C-O Bonds by a Robust Heterogeneous Ni/C Catalyst: Applications to the Cleavage of Complex Lignin-Related Fragments
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We report the chemo- and regioselective hydrogenolysis of the C-O bonds in di-ortho-substituted diaryl ethers under the catalysis of a supported nickel catalyst. The catalyst comprises heterogeneous nickel particles supported on activated carbon and furnishes arenes and phenols in high yields without hydrogenation. The high thermal stability of the embedded metal particles allows C-O bond cleavage to occur in highly substituted diaryl ether units akin to those in lignin. Preliminary mechanistic experiments show that this catalyst undergoes sintering less readily than previously reported catalyst particles that form from a solution of [Ni(cod)2].
- Gao, Fang,Webb, Jonathan D.,Hartwig, John F.
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p. 1474 - 1478
(2016/02/12)
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- A ligand-free, powerful, and practical method for methoxylation of unactivated aryl bromides by use of the CuCl/HCOOMe/MeONa/MeOH system
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A ligand-free, powerful, and practical method for mono and polymethoxylation of unactivated aryl bromides has been developed; CuCl was used as catalyst, HCOOMe as cocatalyst, and methanolic MeONa as both nucleophile and solvent. This eco-friendly procedure is characterized by operational simplicity, inexpensive substrates (unactivated mono to polybromoarenes), full conversion, and direct recovery of pure MeOH.
- Guo, Ying,Ji, Si-Zhe,Chen, Cheng,Liu, Hong-Wei,Zhao, Jian-Hong,Zheng, Yu-Lin,Ji, Ya-Fei
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p. 8651 - 8664
(2015/03/05)
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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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- A green approach for the decoration of Pd nanoparticles on graphene nanosheets: An in situ process for the reduction of C-C double bonds and a reusable catalyst for the Suzuki cross-coupling reaction
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A new strategy for in situ synthesis of palladium nanoparticles (Pd NPs) decorated on reduced graphene oxide (rGO) nanosheets with controlled size and shape is reported. This strategy was designed as three processes in one pot, namely, (a) reduction of graphene oxide, (b) formation of Pd NPs on the rGO nanosheets and (c) simultaneous reduction of olefin. In this synthesis process, a hydrogen atmosphere was used to develop the Pd NPs-rGO nanocatalyst, which is reusable and easily separable. The influence of the size and morphology of the Pd-rGO-H2 catalyst on the catalytic activity in the Suzuki cross-coupling reaction was investigated by comparing with other catalysts, Pd-rGO-As and Pd-rGO-Gl, and they were synthesized by different reducing agents, ascorbic acid and glucose, respectively. The catalysts were characterized by electron microscopy (HRTEM, SEM), FT-IR, XRD and XPS. The Pd-rGO-H2 catalyst was found to possess excellent catalytic activity and recyclability in the Suzuki cross-coupling reaction under mild reaction conditions.
- Hussain, Najrul,Borah, Ashwini,Darabdhara, Gitashree,Gogoi, Pranjal,Azhagan, Vedi Kuyil,Shelke, Manjusha V.,Das, Manash R.
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p. 6631 - 6641
(2015/08/06)
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- Access to 3-arylindoles through a tandem one-pot protocol involving dearomatization, a regioselective michael addition reaction, and rearomatization
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A facile, general and rapid protocol for the introduction of oxygenated aryls at the 3-position of indoles is described. This approach consists of a tandem dearomatization, a regioselective Michael addition reaction, and rearomatization in a one-pot three-step sequence to obtain 3-arylindoles in good yields. A non-metal mediated detour method for installing oxygenated aryls at the 3-position of indoles is described. Copyright
- Chittimalla, Santhosh Kumar,Bandi, Chennakesavulu,Putturu, Sireesha,Kuppusamy, Rajesh,Boellaard, Kevin Christopher,Tan, David Chu Aan,Lum, Demi Ming Jie
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p. 2565 - 2575
(2014/05/06)
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- Catalytic depolymerization of alkali lignin in subcritical water: Influence of formic acid and Pd/C catalyst on the yields of liquid monomeric aromatic products
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Alkali lignin was subjected to depolymerization in subcritical water at 265 °C, 6.5 MPa for reaction times between 1-6 h in a batch reactor and in the presence of formic acid (FA) and Pd/C catalyst. The oil products were extracted into diethyl ether and contained >90% of single-ring phenolic compounds. The reaction of lignin in subcritical water alone yielded 22.3 wt% oil containing 56% guaiacol as the main product. A maximum oil yield of 33.1 wt% was obtained when the lignin was reacted in the presence of formic acid alone. In the presence of FA, catechol became the predominant compound, with more than 80% of the ether extract after 6 h. The conversion of guaiacol to catechol in the presence of formic acid suggested the hydrolysis of O-CH3 ether bonds. In addition, the yields of alkyl guaiacols increased in the presence of FA. The use of 5 wt% Pd/C catalyst with FA slightly decreased the yields of oil products but led to compounds indicative of hydrogenolysis of aryl-O ether bonds as well as hydrogenation of CC bonds.
- Onwudili, Jude A.,Williams, Paul T.
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p. 4740 - 4748
(2014/12/11)
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- Correlating lignin structural features to phase partitioning behavior in a novel aqueous fractionation of softwood Kraft black liquor
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In this work, a set of softwood lignins were recovered from a Kraft black liquor using a novel pH-based fractionation process involving sequential CO 2 acidification and separation of the solvated aqueous lignin fraction. These recovered lignin fractions were characterized with respect to properties that may be responsible for their phase partitioning behavior as well as properties that may render the lignins more suitable for materials applications. Lignin fractions were recovered between a pH range of 12.8 and 9.5 with the bulk of the lignin (90%) recovered between a pH of 11.1 and 10.0. While all the fractions were found to consist primarily of lignin as validated by sample methoxyl content, the first fractions to phase separated were found to be especially enriched in aliphatic extractives and polysaccharides. From the bulk of the lignin that was recovered between a pH of 11.1 and 10.0 a number of noteworthy trends were discernible from the data. Specifically, the phenolic hydroxyl content was found to exhibit a strong negative correlation to the fractionation pH and exhibited a nearly 50% increase with recovery at decreasing pH, while the GPC-estimated molecular weights and 13C NMR-estimated β-O-4 content showed strong positive correlations to the pH at recovery. The aliphatic hydroxyl content exhibited minimal differences between recovery conditions. Overall, these results suggest that this fractionation approach can generate lignin fractions enriched in select physical or structural properties that may be important for their application as feedstocks for renewable chemicals or materials.
- Stoklosa, Ryan J.,Velez, Julian,Kelkar, Shantanu,Saffron, Christopher M.,Thies, Mark C.,Hodge, David B.
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supporting information
p. 2904 - 2912
(2013/10/08)
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- CONTINUOUS PROCESS FOR CONVERSION OF LIGNIN TO USEFUL COMPOUNDS
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This specification discloses an operational continuous process to convert lignin as found in ligno-cellulosic biomass before or after converting at least some of the carbohydrates. The continuous process has been demonstrated to create a slurry comprised of lignin, raise the slurry comprised of lignin to ultra-high pressure, deoxygenate the lignin in a lignin conversion reactor over a catalyst which is not a fixed bed without producing char. The conversion products of the carbohydrates or lignin can be further processed into polyester intermediates for use in polyester preforms and bottles.
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Paragraph 0287-0293
(2013/09/12)
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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.
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Paragraph 0153-0168
(2013/03/26)
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- Transetherification of guaiacol to o-ethoxyphenol with gamma Al 2O3 as a catalyst in supercritical ethanol
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The production of chemicals from lignin and lignin depolymerisation products is a promising alternative route to replace fossil fuels. Transetherification of guaiacol, a lignin derived model compound, to o-ethoxyphenol with γ-Al2O3 as the catalyst in supercritical ethanol has been investigated. The best reaction condition is 280°C for 3 h, giving a yield of 42% with a selectivity of 86%. A reaction pathway is also proposed. Besides, this work provides an example for producing a longer chain ether from a short chain ether.
- Yang, Le,Seshan,Li, Yongdan
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- REDUCTION OF C-0 BONDS BY CATALYTIC TRANSFER HYDROGENOLYSIS
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The present invention relates to a method of reducing a C-O bond to the corresponding C-H bond in a substrate which could be a benzylic alcohol, allylic alcohol, ester,or ether or an ether bond beta to a hydroxyl group or alpha to a carbonyl group.
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Page/Page column 14
(2012/09/22)
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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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- Deoxygenation of aromatic ketones using transfer hydrogenolysis with Raney nickel in 2-propanol
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Aryl ketones are readily deoxygenated to their corresponding aryl alkanes upon treatment with Raney nickel catalyst in boiling 2-propanol. Taylor & Francis Group, LLC.
- Zuidema, Daniel R.,Williams, Sarah L.,Wert, Katherine J.,Bosma, Karin J.,Smith, Abigail L.,Mebane, Robert C.
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experimental part
p. 2927 - 2931
(2011/09/12)
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- A highly active heterogeneous palladium catalyst supported on a synthetic adsorbent
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A method to prepare heterogeneous palladium catalyst highly dispersed in a synthetic adsorbent DIAION HP20, has been demonstrated. Heterogeneous palladium catalyst are suitable for organic synthetic chemistry due to their high air-stability, reconverability, reusability, and non-residual property. The catalyst was obtained by adding DIAION HP20 into a rust-colored solution of Pd(OAc)2 in MeOH at room temperature. The resulting products was collected by filtration, washed with H2O and MeOH, and dried in vacuo to give a palladium-DIAION HP20 complex as a grey powder. The products was made from a physical interaction between the orbitals of the palladium species and π-electrons of the benzene rings of the adsorbents. The thermogravimetry- differential thermal analysis of the complex showed that the complex has no volatiles.
- Monguchi, Yasunari,Fujita, Yuki,Endo, Koichi,Takao, Shinobu,Yoshimura, Masatoshi,Takagi, Yukio,Maegawa, Tomohiro,Sajiki, Hironao
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scheme or table
p. 834 - 837
(2009/06/25)
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- Fine particle and gaseous emission rates from residential wood combustion
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Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning-communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter(a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and se mivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8- C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and forts were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography. Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter (a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and semivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8-C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence, and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and ions were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography.
- Mcdonald, Jacob D.,Zielinska, Barbara,Fujita, Eric M.,Sagebiel, John C.,Chow, Judith C.,Watson, John G.
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p. 2080 - 2091
(2007/10/03)
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- Methoxyphenols from burning of Scandinavian forest plant materials
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Semivolatile compounds in smoke from gram-scale incomplete burning of plant materials were assessed by gas chromatography and mass spectrometry. Gas syringe sampling was shown to be adequate by comparison with adsorbent sampling. Methoxyphenols as well as 1,6-anhydroglucose were released in amounts as large as 10 mg kg-1 of dry biomass at 90% combustion efficiency. Wood, twigs, bark and needles from the conifers Norway spruce and Scots pine emitted 12 reported 2-methoxyphenols in similar proportions. Grass, heather and birchwood released the same 2-methoxyphenols but also the corresponding 2,6-dimethoxyphenols which are characteristic of angiosperms. The methoxyphenols are formed from lignin and differ in structure by the group in para position relative to the phenolic OH group. Prominent phenols were those with trans-l-propenyl and ethenyl groups in that position. Vanillin, 4- hydroxy-3-methoxybenzaldehyde, was a prominent carbonyl compound from the conifer materials. (C) 2000 Elsevier Science Ltd.
- Kjaellstrand, Jennica,Ramnaes, Olle,Petersson, Goeran
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p. 735 - 741
(2007/10/03)
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- Evaluation of acute toxicity and genotoxicity of liquid products from pyrolysis of Eucalyptus grandis wood
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Slow pyrolysis of Eucalyptus grandis wood was performed in an oven laboratory, and smoke was trapped and condensed to yield liquid products. Polycyclic aromatic hydrocarbons (PAHs) and phenolic fractions were isolated from the former liquid products using adsorption column chromatography (ACC) and identified by GC/MS. Concentrations of PAH and phenolic fractions in total pyrolysis liquids were respectively 48.9 μg/g and 8.59% (w/w). Acute toxicity of total samples of pyrolysis liquids and the phenolic fraction was evaluated by means of two bioassays, namely, 24-h immobilization bioassay with Daphnia magna and Microtox(TM) bioassays, the latter employing the luminescent bacteria Photobacterium phosphoreum. Total pyrolysis liquids and the PAH fraction were evaluated for genotoxicity by the Microtox(TM) bioassay conducted using rehydrated freeze-dried dark mutant of the luminescent bacteria Vibrio fisheri strain M169. Total pyrolysis liquids and the phenolic fraction, respectively, in concentrations of 170 and 68 mg/L were able to immobilize 50% (EC50) of the D. magna population following 24-h exposure. Concentrations of 19 and 6 mg/L, respectively, for total pyrolysis liquids and phenolic fraction were the effective concentrations that resulted in a 50% (EC50) reduction in light produced by bacteria in the Microtox(TM) bioassay. Accordingly, the Microtox(TM) bioassay was more sensitive to toxic effects of both kind of samples than the D. magna bioassay, particularly for the phenolic fraction. Regarding to the genotoxicity evaluation, the results achieved by Microtox(TM) bioassay showed that total pyrolysis liquids had no genotoxic effects with and without exogenous metabolic activation using rat liver homogenate (S9). However, the PAH fraction showed toxic effects with rat liver activation and had a dose-response number (DRN) equal to 1.6, being in this way suspected genotoxic. The lowest detected concentration (LDC) of the PAH fraction able to cause genotoxic effects was 375 μg/L.
- Pimenta,Bayona,Garcia,Solanas
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p. 169 - 175
(2007/10/03)
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- Fine particulate matter (PM) and organic speciation of fireplace emissions
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This paper presents a summary of fireplace particle size and organic speciation data gathered to date in an ongoing project. Tests are being conducted in a residential wood combustion (RWC) laboratory on three factory- built fireplaces. RWC wood smoke particles 10 μm (PM10) consist primarily of a mixture of organic compounds that have condensed into droplets; therefore, the size distribution and total mass are influenced by temperature of the sample during its collection. During the series 1 tests (15 tests), the dilution tunnel used to cool and dilute the stack gases gave an average mixed gas temperature of 47.3 °C and an average dilution ratio of 4.3. Averages for the PM2.5 (particles 2.5 μm) and PM10 fractions were 74 and 84%, respectively. For the series 2 tests, the dilution tunnel was modified, reducing the average mixed gas temperatures to 33.8 °C and increasing the average dilution ratio to 11.0 in tests completed to date. PM2.5 and PM10 fractions were 83 and 91%, respectively. Since typical winter time mixed gas temperatures would usually be less than 10 °C, these size fraction results (even from the series 2 tests) probably represent the lower bound; the PM10 and PM2.5 size fractions might be higher at typical winter temperatures. The particles collected on the first stage (cutpoint ? 11.7 μm) were light gray and appeared to include inorganic ash. Particles collected on the remainder of the stages were black and appeared to be condensed organics because there was noticeable lateral bleeding of the collected materials into the filter substrate. Total particulate emission rates ranged from 10.3 to 58.4 g/h; corresponding emission factors ranged from 3.3 to 14.9 g/kg of dry wood burned. A wide range of Environmental Protection Agency (EPA) Method 8270 semivolatile organic compounds were found in the emissions; of the 17 target compounds quantified, major constituents are phenol, 2-methylphenol, 4- methylphenol, 2,4-dimethylphenol, and naphthalene. An account is given on fireplace particle size and organic speciation data gathered to date in an ongoing project. Total particulate matter emission rates and the results of analyses for semivolatile organics in the emissions are discussed.
- Purvis, Carol R.,Mccrillis, Robert C.,Kariher, Peter H.
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p. 1653 - 1658
(2007/10/03)
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- 3-(heteroaryl)-1-?(2,3-dihydro-1h-isoindol-2-yl)alkyl!pyrrolidines and 3-(heteroaryl)-1-?(2,3-dihydro-1h-indol-1-yl)alkyl!pyrrolidines and related compounds and their therapeutic untility
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Heteroarylpiperidines, pyrrolidines, and piperazines are useful as antipsychotic and analgesic agents. The compounds are especially useful for treating psychoses by administering to a mammal a psychoses-treating effective amount of one of the compounds. Depot derivatives of the compounds are useful for providing long acting effects of the compounds. The compounds are also useful as analgesics by administering a pain-relieving effective amount of one of the compounds to a mammal.
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- Sodium Bis(trimethylsily)amide and Lithium Diisopropylamide in Deprotection of Alkyl Aryl Ethers: α-Effect of Silicon
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Removal of methyl, benzyl, and methylene groups from alkyl aryl ethers is among the most popular deprotecting methods in organic synthesis. Alkali organoamides NaN(SiMe3)2 and LiN(i-Pr)2, often used as organic bases, have been developed as efficient deprotecting agents. Treatment of aryl methyl ethers with 1.5 equiv of NaN(SiMe3)2 or LiN(i-Pr)2 in THF and 1,3-dimethyl-2-imidazolidinone in a sealed tube at 185 °C produced the corresponding phenol derivatives in good to excellent yields (80-97percent). Removal of the methylene unit from benzodioxole derivatives was also accomplished by use of 2.5 equiv of these alkali organoamides. The corresponding catechols were obtained in 93-99percent yields. The activity of NaN(SiMe3)2 was proven lower than that of LiN(i-Pr)2; it is due to the steric congestion and the α-stabilizing effect of the silyl groups. Thus selective mono-O-demethylation of o-dimethoxybenzenes can be achieved by the use of NaN(SiMe3)2 but not LiN(i-Pr)2. O-Debenzylation of aryl benzyl ethers, however, can be accomplished by the use of LiN(i-Pr)2.
- Hwu, Jih Ru,Wong, Fung Fuh,Huang, Jiann-Jyh,Tsay, Shwu-Chen
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p. 4097 - 4104
(2007/10/03)
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- 1-(arylthioalkyl, arylaminoalkyl or arylmethylenealkyl)-4-(heteroaryl) piperidines and related compounds useful as antipsychotics and analgesics
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Heteroarylpiperidines, pyrrolidines, and piperazines are useful as antipsychotic and analgesic agents. the compounds are especially useful for treating psychoses by administering to a mammal a psychoses-treating effective amount of one of the compounds. Depot derivatives of the compounds are useful for providing long acting effects of the compounds. The compounds are also useful as analgesics by administering a pain-relieving effective amount of one of the compounds to a mammal.
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- Calcium metal in liquid ammonia for selective reduction of organic compounds
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Selective reduction of functional groups by use of dissolving calcium metal was performed, and the results are in comparison with those by lithium and sodium metals. Reduction with 2.0-2.2 equiv of calcium led chromone (1) to 4-chromanone (2, 75% yield), coumarin (4) to dihydrocoumarin (5, 76% yield) and 3-(2-hydroxyphenyl)-1-propanol (6, 6% yield), α-tetralone (7) to 1,2,3,4-tetrahydro-1-naphthol (8, 81% yield), and β-methoxystyrene (12) to methyl phenethyl ether (13, 85% yield). Performance of reductions on the same substrates by use of 4.0 equiv of lithium or sodium metal gave over-reduced products. Reduction of indole-3-carboxaldehyde (15) to 3-indolemethanol (16), 1-acetylnaphthalene (17) to 1-acetyl-3,4-dihydronaphthalene (18), and trans-4-phenyl-3-buten-2-one (19) to 4-phenyl-2-butanone (20) were accomplished by use of calcium, lithium, and sodium metals, among which calcium gave the highest yields (80-90%). Being a milder reducing agent than lithium and sodium, calcium metal in liquid ammonia offered a better selectivity.
- Hwu, Jih Ru,Wein,Leu, Yi-Jing
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p. 1493 - 1498
(2007/10/03)
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- Heteroarylpiperidines, pyrrolidines and piperazines and their use as antipsychotics and analetics
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Heteroarylpiperidines, pyrrolidines, and piperazines are useful as antipsychotic and analgesic agents. The compounds are especially useful for treating psychoses by administering to a mammal a psychoses-treating effective amount of one of the compounds. The compounds are also useful as analgesics by administering a pain-relieving effective amount of one of the compounds to a mammal.
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- Arylalkylheterocyclic amines,N-substituted by aryloxyalkyl group in a method for allergy treatment
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A method of inhibiting Type 1 allergic responses in a living animal body with substituted heterocyclic amines is disclosed wherein the active agents are expressed generally by the formula which includes certain known and certain known compounds: STR1 wherein P is zero, one or two; m is one to six inclusive; A is selected from hydrogen, hydroxy or cyano; d is zero or one; Q is --CH--, CH2 -- or STR2 n is zero or one and when Q is --CH-- and n is one, a double bond is formed with one of the adjacent carbons but not both at the same time, and when n and d are zero at the same time, a double bond is formed between the α carbon and a carbon of the central heterocyclic amine ring; Ar, D and R are selected from phenyl, substituted phenyl, pyridinyl, thienyl, furanyl or naphthyl and in addition, R may have the values benzyl, substituted benzyl, cycloalkyl or loweralkyl and D may additionally have the values: 2H-1-benzopyran-2-one,4-oxo-4H-1-benzopyran-2-carboxylic acid loweralkyl ester, 2,3-dihydro-4H-1-benzopyran-4-one, 1,4-benzodioxanloweralkyl-2-yl or 1,1'-biphenyl-4-yl and the pharmaceutically acceptable salts thereof.
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- DEOXYGENATION OF ALDEHYDES AND KETONES WITH SODIUM CYANOBOROHYDRIDE
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Treatment of hydroxy-substituted aromatic aldehydes and ketones with sodium cyanoborohydride yields the corresponding methylene compounds under conditions which favor intermediate carbonium ion formation.
- Elliger, Carl A.
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p. 1315 - 1324
(2007/10/02)
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- Catalytic transfer hydrogenation of benzylic and styryl compounds with palladium/carbon and 2-propanol. Selective removal of O-benzyl groups from carbohydrate derivatives
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2-Propanol is shown to be an effective hydrogen donor, in the presence of palladium/carbon, for catalytic transfer hydrogenation reactions of benzylic and styryl compounds, e.g., for the quantitative conversion of cinnamyl alcohol into 3-phenylpropanol.In the reduction of derivatives of cinnamic acid, decarboxylation also occurs.During the latter reaction, the phenyl group appears to function as an anchoring group for the palladium atom, because derivatives of phenylpropanoic acid are decarboxylated more readily than are those of phenylacetic acid.In hydrogenolysis reactions, aryl alcohols undergo disproportionation whereas benzyl ethers, represented by O-benzyl and related derivatives of carbohydrates, are smoothly cleaved.Although 2-propanol is less reactive as a hydrogen donor than formic acid, it exhibits greater selectivity, as illustrated by relative rates of hydrogenolysis of O-benzyl and O-benzylidene substituents.The use of alumina-supported palladium is more effective than palladium/carbon for promoting stepwise removal of O-benzyl substituents, as shown by the preparation of methyl 2-O-benzyl- and -3-O-benzyl-α-D-glucopyranoside from the 2,3-di-O-benzyl derivative.A possible relationship between the orientation of O-benzyl groups and the chemical shift differences between the diastereotopic benzylic protons is decribed.
- Rao, Vanga S.,Perlin, Arthur S.
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p. 652 - 657
(2007/10/02)
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- HYDROGENOLYSIS OF LIGNINS: NICKEL BORIDE CATALYST
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Nickel boride generated within the wood structure allows the selective hydrogenolysis of wood meals. 4-n-Ethylguajacol and 4-n-Ethylsyringol are prepared with interesting yields.
- Loubinoux, B.,Heitz, M.,Coudert, G.,Guillaumet, G.
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p. 4991 - 4994
(2007/10/02)
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