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Sample records for a2 catalyzed acidolysis

  1. Synthesis of structured phospholipids by immobilized phospholipase A2 catalyzed acidolysis

    DEFF Research Database (Denmark)

    Vikbjerg, Anders Falk; Xu, Xuebing

    2007-01-01

    Acyl modification of the sn-2 position in phospholipids (PLs) was conducted by acidolysis reaction using immobilized phospholipase A2 (PLA2) as the catalyst. In the first stage we screened different carriers for their ability to immobilize PLA2. Several carriers were able to fix the enzyme...

  2. Quantitation of acyl migration during lipase-catalyzed acidolysis, and of the regioisomers of structured triacylglycerols formed

    DEFF Research Database (Denmark)

    Mu, Huiling; Kurvinen, J.P.; Kallio, H.;

    2001-01-01

    Various MLM-type (M, medium-chain fatty acids; L, long-chain fatty acids) structured triacylglycerols were produced in pilot- or small-scale packed-bed reactors by lipase-catalyzed acidolysis. The incorporation and acyl migration of octanoic acid were measured by gas chromatography and Grignard d...

  3. Lipase-catalyzed acidolysis of canola oil with caprylic acid to produce medium-, long- and medium-chain-type structured lipids

    DEFF Research Database (Denmark)

    Wang, Yingyao; Xia, Luan; Xu, Xuebing

    2012-01-01

    Lipase-catalyzed acidolysis of canola oil with caprylic acid was performed to produce structured lipids (SLs) containing medium-chain fatty acid (M) at position sn-1,3 and long-chain fatty acid (L) at the sn-2 position in a solvent-free system. Six commercial lipases from different sources were s...

  4. Effects of antioxidants on the lipase-catalyzed acidolysis during production of structured lipids

    DEFF Research Database (Denmark)

    Xu, Xuebing; Timm Heinrich, Maike; Nielsen, Nina Skall

    2005-01-01

    In the production process of structured lipids, the influence of the addition of antioxidants before enzymatic acidolysis was investigated. Eight different antioxidants were screened: butylated hydroxyanisole, butylated hydroxytoluene, propyl gallate, ascorbyl palmitate, citric acid, EDTA...... by the addition of antioxidants, neither in a batch process nor in a packed-bed reactor operation. a-Tocopherol concentrations remained stable for those mixtures where tocopherols were added. Primary oxidation products (measured as peroxide values) were reduced after acidolysis in the packed-bed reactor, likely...... due to the adsorption in the enzyme bed. The study shows that the addition of antioxidants before enzymatic reactions has no negative effects on the reaction progress. None of the antioxidants chosen had a significant positive effect on either the reaction process or the oxidative status...

  5. Parameters affecting incorporation and by-product formation during the production of structured phospholipids by lipase-catalyzed acidolysis in solvent free system

    DEFF Research Database (Denmark)

    Vikbjerg, Anders Falk; Mu, Huiling; Xu, Xuebing

    2005-01-01

    to minimize by-products during reaction. In the present study we examined the Lipozyme RM IM-catalyzed acidolysis for the production of structured phospholipids between phosphatidylcholine (PC) and caprylic acid in the solvent free system. A five-factor response surface design was used to evaluate...... at three levels with two star points. All parameters besides water addition had an effect on the incorporation of caprylic acid into PC and lysophosphatidylcholine (LPC). Reaction time and enzyme dosage showed increased effect on incorporation into PC, while substrate ratio and reaction temperature showed...... opposite effect. The PC content decreased with increase of all parameters except for substrate ratio. Optimal conditions are recommended as enzyme dosage 40%, reaction temperature 55°C, water addition 1%, reaction time 70h, and substrate ratio 6 mol/mol caprylic acid/PC. Under these conditions...

  6. Use of immobilized phospholipase A1-catalyzed acidolysis for the production of structured phosphatidylcholine with an elevated conjugated linoleic acid content

    Energy Technology Data Exchange (ETDEWEB)

    Baeza-Jimenez, R.; Gonzalez-Rodriguez, J.; Kim, I. H.; Gracia, H. S.; Otero, C.

    2012-11-01

    Structured phosphatidylcholine (SPC) was successfully produced via immobilized phospholipase A1 (PLA1) catalyzed acidolysis of phosphatidylcholine (PC) with conjugated linoleic acid (CLA). The effects of enzyme loading (2, 5, 10, 15 and 20%, with respect to the weight of substrates), temperature (20, 30, 40, 50 and 60 degree centigrade) and the molar ratio of substrates (1:2, 1:4, 1:6, 1:8 and 1:10, PC/CLA) were evaluated to maximize the incorporation of CLA into PC. The maximum incorporation of CLA achieved was ca. 90% for 24 h of reaction at 50 degree centigrade and 200 rpm, using a 1:4 substrate molar ratio and an enzyme loading of 15%. (Author) 30 refs.

  7. Characteristics of structured lipid prepared by lipase-catalyzed acidolysis of roasted sesame oil and caprylic acid in a bench-scale continuous packed bed reactor.

    Science.gov (United States)

    Kim, Byung Hee; Akoh, Casimir C

    2006-07-12

    Structured lipid (SL) was prepared from roasted sesame oil and caprylic acid (CA) by Rhizomucor miehei lipase-catalyzed acidolysis in a bench-scale continuous packed bed reactor. Total incorporation and acyl migration of CA in the SL were 42.5 and 3.1 mol %, respectively, and the half-life of the lipase was 19.2 days. The SL displayed different physical and chemical properties, less saturated dark brown color, lower viscosity, lower melting and crystallization temperature ranges, higher melting and crystallization enthalpies, higher smoke point, higher saponification value, and lower iodine value, in comparison to those of unmodified sesame oil. The oxidative stability of purified SL was lower than that of sesame oil. There were no differences in the contents of unsaponifiables including tocopherols and phytosterols. However, total sesame lignans content was decreased in SL due to the loss of sesamol when compared to sesame oil. Most of the 70 volatiles present in roasted sesame oil were removed from SL during short-path distillation of SL. These results indicate that the characteristics of SL are different from those of original sesame oil in several aspects except for the contents of tocopherols and phytosterols.

  8. Use of immobilized phospholipase A1-catalyzed acidolysis for the production of structured phosphatidylcholine with an elevated conjugated linoleic acid content

    Directory of Open Access Journals (Sweden)

    Baeza-Jiménez, R.

    2012-03-01

    Full Text Available Structured phosphatidylcholine (SPC was successfully produced via immobilized phospholipase A1 (PLA1catalyzed acidolysis of phosphatidylcholine (PC with conjugated linoleic acid (CLA. The effects of enzyme loading (2, 5, 10, 15 and 20%, with respect to the weight of substrates, temperature (20, 30, 40, 50 and 60 °C and the molar ratio of substrates (1:2, 1:4, 1:6, 1:8 and 1:10, PC/CLA were evaluated to maximize the incorporation of CLA into PC. The maximum incorporation of CLA achieved was ca. 90% for 24 h of reaction at 50 °C and 200 rpm, using a 1:4 substrate molar ratio and an enzyme loading of 15%.

    Fosfatidilcolina estructurada (SPC fue producida por acidólisis de fosfatidilcolina (PC y ácido linoleico conjugado (CLA usando fosfolipasa A1 (PLA1 inmovilizada. Los efectos de carga de enzima (2, 5, 10, 15 y 20%, respecto al peso de los sustratos, temperatura (20, 30, 40, 50 y 60 °C y la relación molar de sustratos (1:2, 1:4, 1:6, 1:8 y 1:10, PC/CLA fueron evaluados para alcanzar la más elevada incorporación de CLA en PC. La máxima incorporación de CLA obtenida fue de 90% a 50 °C y 200 rpm, para una relación molar 1:4 con una carga de enzima de 15% después de 24 h.

  9. Lipase-catalyzed acidolysis of palm mid fraction oil with palmitic and stearic Fatty Acid mixture for production of cocoa butter equivalent.

    Science.gov (United States)

    Mohamed, Ibrahim O

    2013-10-01

    Cocoa butter equivalent (CBE) was prepared by enzymatic acidolysis reaction of substrate consisting of refined palm mid fraction oil and palmitic-stearic fatty acid mixture. The reactions were performed in a batch reactor at a temperature of 60 °C in an orbital shaker operated at 160 RPM. Different mass ratios of substrates were explored, and the composition of the five major triacylglycerols (TAGs) of the structured lipids was identified and quantified using cocoa butter certified reference material IRMM-801. The reaction resulted in production of cocoa butter equivalent with the TAGs' composition (1,3-dipalmitoyl-2-oleoyl-glycerol 30.7%, 1-palmitoyl-2-oleoyl-3-stearoyl-rac-glycerol 40.1%, 1-palmitoy-2,3- dioleoyl glycerol 9.0%, 1,3-distearoyl-2-oleoyl-glycerol 14.5 %, and 1-stearoyl-2,3-dioleoyl glycerol 5.7%) and with onset melting temperature of 31.6 °C and peak temperature of 40.4 °C which are close to those of cocoa butter. The proposed kinetics model for the acidolysis reaction presented the experimental data very well. The results of this research showed that palm mid fraction oil TAGs could be restructured to produce value added product such as CBE.

  10. Lipozyme RM IM-catalyzed acidolysis of Cinnamomum camphora seed oil with oleic acid to produce human milk fat substitutes enriched in medium-chain fatty acids.

    Science.gov (United States)

    Zou, Xian-Guo; Hu, Jiang-Ning; Zhao, Man-Li; Zhu, Xue-Mei; Li, Hong-Yan; Liu, Xiao-Ru; Liu, Rong; Deng, Ze-Yuan

    2014-10-29

    In the present study, a human milk fat substitute (HMFS) enriched in medium-chain fatty acids (MCFAs) was synthesized through acidolysis reaction from Cinnamomum camphora seed oil (CCSO) with oleic acid in a solvent-free system. A commercial immobilized lipase, Lipozyme RM IM, from Rhizomucor miehei, was facilitated as a biocatalyst. Effects of different reaction conditions, including substrate molar ratio, enzyme concentration, reaction temperature, and reaction time were investigated using response surface methodology (RSM) to obtain the optimal oleic acid incorporation. After optimization, results showed that the maximal incorporation of oleic acid into HMFS was 59.68%. Compared with CCSO, medium-chain fatty acids at the sn-2 position of HMFS accounted for >70%, whereas oleic acid was occupied predominantly at the sn-1,3 position (78.69%). Meanwhile, triacylglycerol (TAG) components of OCO (23.93%), CCO (14.94%), LaCO (13.58%), OLaO (12.66%), and OOO (11.13%) were determined as the major TAG species in HMFS. The final optimal reaction conditions were carried out as follows: substrate molar ratio (oleic acid/CCSO), 5:1; enzyme concentration, 12.5% (w/w total reactants); reaction temperature, 60 °C; and reaction time, 28 h. The reusability of Lipozyme RM IM in the acidolysis reaction was also evaluated, and it was found that it could be reused up to 9 times without significant loss of activities. Urea inclusion method was used to separate and purify the synthetic product. As the ratio of HMFS/urea increased to 1:2, the acid value lowered to the minimum. In a scale-up experiment, the contents of TAG and total tocopherols in HMFS (modified CCSO) were 77.28% and 12.27 mg/100 g, respectively. All of the physicochemical indices of purified product were within food standards. Therefore, such a MCFA-enriched HMFS produced by using the acidolysis method might have potential application in the infant formula industry.

  11. Comparison of linoleic and conjugated linoleic acids in enzymatic acidolysis of tristearin

    DEFF Research Database (Denmark)

    Yang, Tiankui; Xu, Xuebing; Li, L.T.

    2001-01-01

    The acyl incorporation and migration of linoleic and conjugated linoleic acids in enzymatic acidolysis were compared in a solvent-free system. Two systems were used in the Lipozyme RM IM-catalyzed acidolysis at 60C temperature and 5% by weight enzyme load (based on substrates). One included...... with gas chromatography, pancreatic lipase hydrolysis, and high performance liquid chromatography. Both acyl incorporation and migration of linoleic acid were faster than those of conjugated linoleic acid. At 5 h reaction, there were 13.0% LLL, 46.5% LSL, 27.7% LSS, and 5.6% SSS in the product for a system...

  12. 非水相酶促酸解制备类可可脂的工艺研究%Preparation of cocoa butter equivalents with lipase -catalyzed acidolysis under non- aqueous condition

    Institute of Scientific and Technical Information of China (English)

    沈琪; 刘元法; 徐振波; 王风艳; 王兴国

    2011-01-01

    在非水相条件下,利用固定化脂肪酶催化棕榈油中熔点分提物(POMF)与硬脂酸(St)进行酸解反应制备类可可脂(CBE).考察了不同固定化酶、酶添加量、反应溶剂、酶的水分活度、底物质量比和反应温度对反应产率、速率以及产物中甘三酯组成的影响.结果表明:Lipozyme RM IM添加量8%(以底物质量计),环己烷为溶剂,酶水分活度0.54,St与POMF质量比2:1,反应温度60℃为最佳酸解条件;在此条件下反应150 min,产物中主要甘三酯POP、POS、SOS含量分别达到19.36%、44.17%和25.54%.这与天然可可脂组成(POP 18%、POS 42%、SOS 27%)较为相似,满足CBE指标要求.%Under non - aqueous conditions, the production of cocoa butter equivalents ( CBE ) through acidolysis of palm oil midfraction( POMF)with stearic acid using immobilized lipase as a catalyst was studied. Factors such as immobilized lipase, enzyme dosage, solvent, water activity of lipase, mass ratio of substrate and temperature were investigated to evaluate their influence on the yield and reaction rate together with triglyceride composition of the final product. The result showed that the optimal conditions were as follows:mass ratio of stearic acid to POMF 2:1 in the cyclohexane system ,60 ℃, Lipozyme RM IMIM dosage 8%, water activity of lipase 0.54. After reaction for 150 min under the conditions, the contents of the main triglycerides of POP,POS and SOS in the final product were 19.36% ,44.17% and 25.54% ,respectively,which were quite similar to natural cocoa butter( 18% ,42% and 27% ).

  13. Synthesis of cocoa butter triacylglycerols using a model acidolysis system

    Directory of Open Access Journals (Sweden)

    Göǧüş, Fahrettin

    2008-12-01

    Full Text Available The effects of reaction parameters such as substrate mole ratio, reaction temperature, enzyme load, water content and reaction time were studied in a model enzymatic acidolysis system. Palmitic and stearic acids were incorporated into triolein (OOO under the catalysis of sn-1,3 specific lipase to produce the three major triacylglycerols (TAGs in cocoa butter (CB, namely, 1,3-dipalmitoyl-2-oleoyl--glycerol (POP, 1(3-palmitoyl-3(1-stearoyl-2-oleoyl-glycerol (POS and 1,3distearoyl-2-oleoyl-glycerol (SOS. TAG contents of the reaction products were analyzed by High Performance Liquid Chromatograph (HPLC.The best results (15.2% POP, 30.4% POS, 15.2 % SOS were obtained at 1:3:3 (OOO:palmitic acid:stearic acid substrate mole ratio and reaction parameters: time 10 h, temperature 45 oC, enzyme load 20 %, water content 5 %. The results obtained in this model system might be used for the optimization and application of lipase catalyzed acidolysis reactions in natural systems to produce cocoa butter equivalents (CBEs.El efecto de parámetros de reacción como el ratio molar de sustratos, carga de enzima, contenido de agua o temperatura de reacción fueron estudiados en un sistema modelo de acidolisis para la síntesis de triglicéridos disaturados. Los ácidos grasos palmítico y esteárico se incorporaron a la molécula de trioleína (OOO mediante la catálisis con una li-pasa sn-1,3 específica para producir los tres triglicéridos (TAGs mayoritarios de la manteca de cacao (CB: 1,3-dipalmitil-2-oleoil glicerol (POP, 1(3-palmitil-3(1-estearil-2glicerol (POS and 1,3-diestearil-2-oleoil glicerol (SOS. Los TAGs producidos en cada reacción se analizaron por cromatografía líquida de alta eficacia (HPLC. Los mejores resultados (15.2 %, POP, 30.4 % POS, 15.2 % SOS se obtuvieron empleando la relación molar de sustratos 1:3:3 (OOO: ácido palmítico:ácido esteárico y los parámetros de reacción: tiempo 10h, temperatura 45 °C, carga de enzima 20

  14. Monitoring of monooctanoyl phosphatidylcholine synthesis by enzymatic acidolysis between soybean phosphatidylcholine and caprylic acid by thin-layer chromatography with a flame ionization detector

    DEFF Research Database (Denmark)

    Vikbjerg, Anders Falk; Mu, Huiling; Xu, Xuebing

    2005-01-01

    Thin-layer chromatography with flame ionization detector (TLC-FID) method was used for monitoring the production of structured phospholipids (ML-type: L-long chain fatty acids; M-medium chain fatty acids) by enzyme-catalyzed acidolysis between soybean phosphatidylcholine (PC) and caprylic acid....... It was found that the structured PC fractionated into 2-3 distinct bands on both plate thin layer chromatography (TLC) and Chromarod TLC. These 3 bands represented PC of LL-type, ML-type and MM-type, respectively. The TLC-FID method was applied in the present study to examine the influence of enzyme dosage...

  15. Lipase-Catalyzed Modification of Canola Oil with Caprylic Acid

    DEFF Research Database (Denmark)

    Wang, Yingyao; Luan, Xia; Xu, Xuebing

    Lipase-catalyzed acidolysis of canola oil with caprylic acid was performed to produce structured lipids. Six commercial lipases from different sources were screened for their ability to incorporate the caprylic acid into the canola oil. The positional distribution of FA on the glycerol backbone o...

  16. Prediction of a model enzymatic acidolysis system using neural networks

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    Güven, Aytaç

    2008-12-01

    Full Text Available A model for the acidolysis of trinolein and palmitic acid under the catalysis of immobilized sn-1,3 specific lipase was presented in this study. A neural networks (NN based model was developed for the prediction of the concentrations of the major reaction products of this reaction (1-palmitoyl-2,3-oleoyl-glycerol (POO 1,3-dipalmitoyl-2-oleoyl-glycerol (POP and triolein (OOO. Substrate ratio (SR, reaction temperature (T and reaction time (t were used as input parameters. The optimal architecture of the proposed NN model, which consists of one input layer with three inputs, one hidden layer with seven neurons and one output layer with three outputs, wass able to predict the reaction products concentration with a mean square error (MSE of less than 1.5 and R2 of 0.999. and explicit formulation of the proposed NN is presented. Considerable good performance is achieved in modeling the acidolysis reaction using neuronal networks.En este estudio se presenta un modelo para la acidólisis de la trilinoleina y el ácido palmítico mediante la catálisis con una lipasa específica sn-1,3 inmovilizada. Un modelo basado en redes neuronales (NN ha sido desarrollado para la predicción de la concentración de los principales productos de esta reacción (1-palmitoil-2,3-oleoil-glicerol (POO, 1,3-dipalmitoil-2-oleoil-glicerol (POP y trioleina (OOO. Se han usado como parámetros de entrada: la proporción del sustrato (SR, la temperatura de reacción (T y el tiempo de reacción (t. La arquitectura óptima del modelo de NN propuesto, que consiste en una capa de entrada con tres entradas, una capa oculta con siete neuronas y una capa de salida con tres salidas, fue capaz de predecir la concentración de los productos de reacción con un error cuadrático medio (MSE de menos de 1.5 y una R2 de 0.999 . Se presenta una formulación explícita del modelo NN propuesto. Se obtienen muy buenos resultados en la predicción de la reacciones de acidólisis mediante el uso de

  17. Lipase-catalyzed modification of lard to produce human milk fat substitutes

    DEFF Research Database (Denmark)

    Yang, Tiankui; Xu, Xuebing; He, C.;

    2003-01-01

    The objective of the present work was to modify lard into human milk fat substitutes (HMFS) by Lipozyme RM IM-catalyzed acidolysis. Lard and soybean fatty acids were esterified in a solvent-free system. The reaction substrates for HMFS production were specially chosen to mimic human milk fats.......7%, and time 1.0 h), were similar to the fat in Chinese mothers' milk. The results showed that it was possible to produce human milk fat substitutes from lard through enzymatic acidolysis with soybean fatty acids....

  18. Production of structured lipids by acidolysis of an EPA-enriched fish oil and caprylic acid in a packed bed reactor: analysis of three different operation modes.

    Science.gov (United States)

    González Moreno, P A; Robles Medina, A; Camacho Rubio, F; Camacho Páez, B; Molina Grima, E

    2004-01-01

    Structured triacylglycerols (ST) enriched in eicosapentaenoic acid (EPA) in position 2 of the triacylglycerol (TAG) backbone were synthesized by acidolysis of a commercially available EPA-rich oil (EPAX4510, 40% EPA) and caprylic acid (CA), catalyzed by the 1,3-specific immobilized lipase Lipozyme IM. The reaction was carried out in a packed bed reactor (PBR) operating in two ways: (1) by recirculating the reaction mixture from the exit of the bed to the substrate reservoir (discontinuous mode) and (2) in continuous mode, directing the product mixture leaving the PBR to a product reservoir. By operating in these two ways and using a simple kinetic model, representative values for the apparent kinetic constants (kX) for each fatty acid (native, Li or odd, M) were obtained. The kinetic model assumes that the rate of incorporation of a fatty acid into TAG per amount of enzyme, rX (mole/(h g lipase)) is proportional to the extent of the deviation from the equilibrium for each fatty acid (i.e., the difference of concentration between the fatty acid in the triacylglycerol and the concentration of the same fatty acid in the triacylglycerol once the equilibrium of the acidolysis reaction is reached). The model allows comparing the two operating modes through the processing intensity, defined as mLt/(V[TG]0) and mL/(q[TG]0), for the discontinuous and continuous operation modes, respectively. In discontinuous mode, ST with 59.5% CA and 9.6% EPA were obtained. In contrast, a ST with 51% CA and 19.6% EPA were obtained when using the continuous operation mode. To enhance the CA incorporation when operating in continuous mode, a two-step acidolysis reaction was performed (third operation mode). This continuous two-step process yields a ST with a 64% CA and a 15% EPA. Finally, after purifying the above ST in a preparative silica gel column, impregnated with boric acid, a ST with 66.9% CA and 19.6% EPA was obtained. The analysis by reverse phase and Ag+ liquid chromatography of

  19. Theoretical study on the N-demethylation mechanism of theobromine catalyzed by P450 isoenzyme 1A2.

    Science.gov (United States)

    Tao, Jing; Kang, Yuan; Xue, Zhiyu; Wang, Yongting; Zhang, Yan; Chen, Qiu; Chen, Zeqin; Xue, Ying

    2015-09-01

    Theobromine, a widely consumed pharmacological active substance, can cause undesirable muscle stiffness, nausea and anorexia in high doses ingestion. The main N-demethylation metabolic mechanism of theobromine catalyzed by P450 isoenzyme 1A2 (CYP1A2) has been explored in this work using the unrestricted hybrid density functional method UB3LYP in conjunction with the LACVP(Fe)/6-31G (H, C, N, O, S, Cl) basis set. Single-point calculations including empirical dispersion corrections were carried out at the higher 6-311++G** basis set. Two N-demethylation pathways were characterized, i.e., 3-N and 7-N demethylations, which involve the initial N-methyl hydroxylation to form carbinolamines and the subsequent carbinolamines decomposition to yield monomethylxanthines and formaldehydes. Our results have shown that the rate-limiting N-methyl hydroxylation occurs via a hydrogen atom transfer (HAT) mechanism, which proceeds in a spin-selective mechanism (SSM) in the gas phase. The carbinolamines generated are prone to decomposition via the contiguous heteroatom-assisted proton-transfer. Strikingly, 3-N demethylation is more favorable than 7-N demethylation due to its lower free energy barrier and 7-methylxanthine therefore is the optimum product reported for the demethylation of theobromine catalyzed by CYP1A2, which are in good agreement with the experimental observation. This work has first revealed the detail N-demethylation mechanisms of theobromine at the theoretical level. It can offer more significant information for the metabolism of purine alkaloid.

  20. Preparation of palm olein enriched with medium chain fatty acids by lipase acidolysis.

    Science.gov (United States)

    Chnadhapuram, Mounika; Sunkireddy, Yella Reddy

    2012-05-01

    Medium chain (MC) fatty acids, caprylic (C8:0) and capric (C10:0) were incorporated into palm olein by 1,3-specific lipase acidolysis, up to 36% and 43%, respectively, when added as mixtures or individually after 24h. It was found that these acids were incorporated into palm olein at the expense of palmitic and oleic acids, the former being larger in quantity and reduction of 18:2 was negligible. The modified palm olein products showed reduction in higher molecular weight triacylglycerols (TGs) and increase in concentration of lower molecular weight TGs compared to those of palm olein. Fatty acids at sn-2 position in modified products were: C10:0, 4%; C16:0, 13%; C18:1, 66%; and C18:2, 15.4%. DSC results showed that the onset of melting and solids fat content were considerably reduced in modified palm olein products and no solids were found even at and below 10°C and also the onset of crystallisation was considerably lowered. The cloud point was reduced and iodine value dropped from 55.4 to 38 in modified palm olein. Thus, nutritionally superior palm olein was prepared by introducing MC fatty acids with reduced palmitic acid through lipase acidolysis.

  1. Effect of Chemical Structure on Pyrolysis Behavior of Alcell Mild Acidolysis Lignin

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    Chao Liu

    2014-12-01

    Full Text Available In this study, two purified mild acidolysis lignins (MAL extracted from triploid poplar, i.e., Alcell MAL and Alkali MAL, were compared. Some properties, including elemental contents, higher heating value (HHV, functional hydroxyl group compositions, and molecular weights, were tested to characterize the structure of these two MALs. The releasing laws of gases and the distribution of products were also investigated through the use of thermogravimetric Fourier transform infrared (TG-FTIR and pyrolysis-gas chromatography combined with mass spectrometry (Py-GC/MS. The results showed that both MALs had pyrolytic advantages, largely because of their unique chemical structures. However, although the species of volatiles from Alkali MAL were similar to those from Alcell MAL, the releasing temperature range for Alcell MAL was relatively narrow and the volatiles from it were concentrated. Among the fast pyrolytic products, phenols were the most abundant. The yield of 2,6-dimethoxy-4-(2-propenylphenol, which was the dominant product, was 25.66% for Alcell MAL and 20.77% for Alkali MAL, respectively. Overall, pyrolytic products from Alcell MAL were more enriched.

  2. Synthesis of structured triacylglycerols containing caproic acid by lipase-catalyzed acidolysis: Optimization by response surface methodology

    DEFF Research Database (Denmark)

    Zhou, D.Q.; Xu, Xuebing; Mu, Huiling;

    2001-01-01

    -r = 2-6 mol/mol; and W-c = 2-12 wt %. The biocatalyst was Lipozyme RM IM, in which Rhizomucor miehei lipase is immobilized on a resin. The incorporation of caproic acid into rapeseed oil was the main monitoring response. In addition, the contents of mono-incorporated structured triacylglycerols and di...

  3. Cytochrome P450 102A2 Catalyzes Efficient Oxidation of Sodium Dodecyl Sulphate: A Molecular Tool for Remediation

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    Irene Axarli

    2010-01-01

    Full Text Available Bacterial cytochrome P450s (CYPs constitute an important family of monooxygenase enzymes that carry out essential roles in the metabolism of endogenous compounds and foreign chemicals. In the present work we report the characterization of CYP102A2 from B. subtilis with a focus on its substrate specificity. CYP102A2 is more active in oxidation of sodium dodecyl sulphate (SDS than any other characterized CYP. The effect of SDS and NADPH concentration on reaction rate showed nonhyperbolic and hyperbolic dependence, respectively. The enzyme was found to exhibit a bell-shaped curve for plots of activity versus pH, over pH values 5.9–8.5. The rate of SDS oxidation reached the maximum value approximately at pH 7.2 and the pH transition observed controlled by two pas in the acidic (pa=6.7±0.08 and basic (pa=7.3±0.06 pH range. The results are discussed in relation to the future biotechnology applications of CYPs.

  4. Acidolysis of terebinth fruit oil with palmitic and caprylic acids in a recirculating packed bed reactor: optimization using response surface methodology

    Directory of Open Access Journals (Sweden)

    Koçak Yanık, D.

    2016-06-01

    Full Text Available The acidolysis reaction of terebinth fruit oil with caprylic and palmitic acid has been investigated. The reaction was catalyzed by lipase (Lipozyme IM from Rhizomucormiehei and carried out in recirculating packed bed reactor. The effects of reaction parameters have been analyzed using response surface methodology. Reaction time (3.5–6.5 h, enzyme load (10–20%, substrate flow rate (4–8 mL·min-1 and substrate mole ratios (Terebinth oil : Palmitic acid : Caprylic acid, 1:1.83:1.22–1:3.07:2.05 were evaluated. The optimum reaction conditions were 5.9 h reaction time, 10% enzyme load, 4 mL·min-1 substrate flow rate and 1:3.10:2.07 substrate mole ratio. The structured lipid obtained at these optimum conditions had 52.23% desired triacylglycerols and a lower caloric value than that of terebinth fruit oil. The melting characteristics and microstructure of the structured lipid were similar to those of commercial margarine fat extracts. The results showed that the structured lipid had the highest oxidative stability among the studied fats.Se ha investigado la reacción de acidolisis del aceite de pistacho con los ácidoscaprílico y palmítico. La reacción fue catalizada por la lipasa Lipozyme IM de Rhizomucormiehei y realizada mediante recirculación del reactor de lecho compacto. Los efectos de los parámetros de la reacción han sido analizados mediante el uso de la metodología de superficie de respuesta. El tiempo de reacción (3.5 hasta 6.5 h, la carga de enzima (10–20%, el caudal de sustrato (4–8 mL·min-1 relaciones molares de los sustrato (aceite de pistacho: ácido palmítico: ácido caprílico, 1: 1,83: 1,22–1: 3,07: 2,05 fueron evaluados. Las condiciones óptimas de reacción fueron 5,9 h de tiempo de reacción, el 10% de carga de la enzima, 4 mL·min-1 de caudal de sustrato y 1: 3,10: 2,07 de relación molar de sustratos. Los lípidos estructurados obtenidos en las condiciones óptimas tenías 52,23% de triacilgliceroles

  5. Hydroxylation of aspartic acid in domains homologous to the epidermal growth factor precursor is catalyzed by a 2-oxoglutarate-dependent dioxygenase.

    Science.gov (United States)

    Stenflo, J; Holme, E; Lindstedt, S; Chandramouli, N; Huang, L H; Tam, J P; Merrifield, R B

    1989-01-01

    3-Hydroxyaspartic acid and 3-hydroxyasparagine are two rare amino acids that are present in domains homologous to the epidermal growth factor precursor in vitamin K-dependent plasma proteins as well as in proteins that do not require vitamin K for normal biosynthesis. They are formed by posttranslational hydroxylation of aspartic acid and asparagine, respectively. The first epidermal growth factor-like domain in factor IX (residues 45-87) was synthesized with aspartic acid in position 64, replacing 3-hydroxyaspartic acid. It was used as substrate in a hydroxylase assay with rat liver microsomes as the source of enzyme and reaction conditions that satisfy the requirements of 2-oxoglutarate-dependent dioxygenases. The synthetic peptide stimulated the 2-oxoglutarate decarboxylation in contrast to synthetic, modified epidermal growth factor (Met-21 and His-22 deleted and Glu-24 replaced by Asp) and synthetic peptides corresponding to residues 60-71 in human factor IX. This indicates that the hydroxylase is a 2-oxoglutarate-dependent dioxygenase with a selective substrate requirement. Images PMID:2492106

  6. Propylsulfonic and arenesulfonic functionalized SBA-15 silica as an efficient and reusable catalyst for the acidolysis of soybean oil with medium-chain fatty acids.

    Science.gov (United States)

    Xie, Wenlei; Zhang, Chi

    2016-11-15

    The objective of this work was to develop a feasible ecofriendly process to produce medium-chain fatty acid (MCFA)-enriched structured lipids (SLs) in heterogeneous manners. For this purpose, the propyl-SO3H or arene-SO3H-modified SBA-15 materials were prepared through a surface functionalization of SBA-15 silica with propyl-SO3H and arene-SO3H groups. The organosulfonic acid-functionalized SBA-15 materials were characterized by Brönsted acidity determination, elemental analysis, XRD, C(13) MAS NMR, FT-IR, SEM, TG, TEM, and N2 adsorption-desorption techniques. Results showed that the propyl-SO3H and arene-SO3H groups were successfully tethered on the SBA-15 support, and the ordered mesoporous structure of SBA-15 silica was well retained after the organofunctionalization. This organic-inorganic hybrid material displayed high surface acidities and high activities in the acidolysis of soybean oil with caprylic or capric acid to produce SLs containing MCFAs. The influences of processing parameters on the reaction were investigated. The two studied catalysts showed an excellent recyclability for the reaction.

  7. Ultrasonic Strengthening Low Grade Boric Magnesium Ore Acidolysis Reaction%超声强化低品位硼镁矿石酸解反应过程研究

    Institute of Scientific and Technical Information of China (English)

    王国胜; 杨鹤南; 齐广

    2016-01-01

    以辽宁花园沟低品位硼镁矿为原料,在搅拌和硫酸酸解过程基础上,引入超声辅助强化酸解过程,考察了超声功率与温度的影响,对比搅拌与超声辅助酸解过程得到,超声辅助可以降低反应温度,缩短反应时间,其产品收率增加,质量提高,硼酸晶体颗粒均匀且晶粒大。%Used low grade boric magnesium ore from Liaoning garden ditch as raw material, based on the condition of stirring, introduction of ultrasonic auxiliary have strengthened acidolysis process, the effect of ultrasonic power and temperature were investigated, and compared to stir and ultrasonic assisted acidolysis process, ultrasound assisted can reduce the reaction temperature, reaction time, the product yield increased, quality improved, borate crystals was uniform grain and grain size was big.

  8. Enzymatic acidolysis of lard to produce 1,3-dioleoyl-2-palmitoylglycerol by Candida sp.99-125 lipase%Candida sp.99-125脂肪酶催化猪油酸解合成1,3-二油酸-2-棕榈酸甘油三酯

    Institute of Scientific and Technical Information of China (English)

    李昕倩; 邓利; 叶贤春; 聂开立; 刘珞; 李玲

    2013-01-01

    The fat of human milk was ester with palmitic acid at the Sn-2 position.The analysis showed that palmitic acid of lard was distributed at the Sn-2 position and used as a raw material for the preparation of 1,3-dioleoyl-2-palmitoylglycerol(OPO).Candida sp.99-125 lipase-catalyzed acidolysis of lard with oleic acid was used to produce OPO in solvent-free systems by the orthogonal experiment design.The optimal conditions were as follows:the substrate mass ratio 1 ∶ 2.0 (the lard/oleic acid),enzyme load 10% (of total the substrate),reaction temperature 40 ℃,and reaction time 4 h.Under the conditions,the content of Sn-2C16∶0 was more than 70% and was more than 93% of palmitic acid content of total fatty acids,and the OPO content was more than 43%.%人乳脂是一种在甘油骨架Sn-2位上富含棕榈酸(C16∶0)的结构酯.经分析可知,猪油中棕榈酸主要分布在甘油酯的Sn-2位,可作为制备1,3-二油酸-2-棕榈酸甘油三酯(OPO)的原料.以Candida sp.99-125脂肪酶作催化剂,以猪油和油酸为原料,通过正交试验对无溶剂体系中酸解合成OPO的工艺条件进行研究,得到最适反应条件:猪油与油酸的质量比为1∶2.0,酶用量为总底物质量的10%,反应温度40℃,反应时间4h.在该反应条件下,经酸解合成的产物三甘酯中,Sn-2C16∶0的含量大于70%,占总脂肪酸中棕榈酸含量的93%以上,并含有43%以上的OPO.

  9. Catalyzing RE Project Development

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Kate; Elgqvist, Emma; Walker, Andy; Cutler, Dylan; Olis, Dan; DiOrio, Nick; Simpkins, Travis

    2016-09-01

    This poster details how screenings done with REopt - NREL's software modeling platform for energy systems integration and optimization - are helping to catalyze the development of hundreds of megawatts of renewable energy.

  10. Muon Catalyzed Fusion

    Science.gov (United States)

    Armour, Edward A.G.

    2007-01-01

    Muon catalyzed fusion is a process in which a negatively charged muon combines with two nuclei of isotopes of hydrogen, e.g, a proton and a deuteron or a deuteron and a triton, to form a muonic molecular ion in which the binding is so tight that nuclear fusion occurs. The muon is normally released after fusion has taken place and so can catalyze further fusions. As the muon has a mean lifetime of 2.2 microseconds, this is the maximum period over which a muon can participate in this process. This article gives an outline of the history of muon catalyzed fusion from 1947, when it was first realised that such a process might occur, to the present day. It includes a description of the contribution that Drachrnan has made to the theory of muon catalyzed fusion and the influence this has had on the author's research.

  11. Muon catalyzed fusion

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, K. [Advanced Meson Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Nagamine, K. [Muon Science Laboratory, IMSS-KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Matsuzaki, T. [Advanced Meson Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kawamura, N. [Muon Science Laboratory, IMSS-KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2005-12-15

    The latest progress of muon catalyzed fusion study at the RIKEN-RAL muon facility (and partly at TRIUMF) is reported. The topics covered are magnetic field effect, muon transfer to {sup 3}He in solid D/T and ortho-para effect in dd{mu} formation.

  12. Lipase catalyzed ester synthesis for food processing industries

    Directory of Open Access Journals (Sweden)

    Aravindan Rajendran

    2009-02-01

    Full Text Available Lipases are one of the most important industrial biocatalyst which catalyzes the hydrolysis of lipids. It can also reverse the reaction at minimum water activity. Because of this pliable nature, it is widely exploited to catalyze the diverse bioconversion reactions, such as hydrolysis, esterification, interesterification, alcoholysis, acidolysis and aminolysis. The property to synthesize the esters from the fatty acids and glycerol promotes its use in various ester synthesis. The esters synthesized by lipase finds applications in numerous fields such as biodiesel production, resolution of the recemic drugs, fat and lipid modification, flavour synthesis, synthesis of enantiopure pharmaceuticals and nutraceuticals. It plays a crucial role in the food processing industries since the process is unaffected by the unwanted side products. Lipase modifications such as the surfactant coating, molecular imprinting to suit for the non-aqueous ester synthesis have also been reported. This review deals with lipase catalyzed ester synthesis, esterification strategies, optimum conditions and their applications in food processing industries.Lipases são catalizadores industriais dos mais importantes, os quais catalizam a hidrólise de lipídeos. Também podem reverter a reação a um mínimo de atividade de água. Devido sua natureza flexível, é amplamente explorada para catalizar uma diversidade de reações de bioconversão como hidrólise, esterificação, interesterificação, alcoólise, acidólise e aminólise. A propriedade de síntese de esteres a partir de ácidos graxos e glicerol promoveu seu uso em várias sínteses de esteres. Os esteres sintetizados por lipases encontram aplicação em numerosos campos como a produção de biodiesel, resolução de drogas racêmicas, modificação de gorduras e lipídios, sintese de aromas, síntese de produtos farmacêuticos enantiopuro e nutracêuticos. As lipases possuem um papel crucial nas indústrias de

  13. Catalyzed Ceramic Burner Material

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Amy S., Dr.

    2012-06-29

    Catalyzed combustion offers the advantages of increased fuel efficiency, decreased emissions (both NOx and CO), and an expanded operating range. These performance improvements are related to the ability of the catalyst to stabilize a flame at or within the burner media and to combust fuel at much lower temperatures. This technology has a diverse set of applications in industrial and commercial heating, including boilers for the paper, food and chemical industries. However, wide spread adoption of catalyzed combustion has been limited by the high cost of precious metals needed for the catalyst materials. The primary objective of this project was the development of an innovative catalyzed burner media for commercial and small industrial boiler applications that drastically reduce the unit cost of the catalyzed media without sacrificing the benefits associated with catalyzed combustion. The scope of this program was to identify both the optimum substrate material as well as the best performing catalyst construction to meet or exceed industry standards for durability, cost, energy efficiency, and emissions. It was anticipated that commercial implementation of this technology would result in significant energy savings and reduced emissions. Based on demonstrated achievements, there is a potential to reduce NOx emissions by 40,000 TPY and natural gas consumption by 8.9 TBtu in industries that heavily utilize natural gas for process heating. These industries include food manufacturing, polymer processing, and pulp and paper manufacturing. Initial evaluation of commercial solutions and upcoming EPA regulations suggests that small to midsized boilers in industrial and commercial markets could possibly see the greatest benefit from this technology. While out of scope for the current program, an extension of this technology could also be applied to catalytic oxidation for volatile organic compounds (VOCs). Considerable progress has been made over the course of the grant

  14. Catalyzing alignment processes

    DEFF Research Database (Denmark)

    Lauridsen, Erik Hagelskjær; Jørgensen, Ulrik

    2004-01-01

    This paper describes how environmental management systems (EMS) spur the circulation of processes that support the constitution of environmental issues as specific environ¬mental objects and objectives. EMS catalyzes alignmentprocesses that produce coherence among the different elements involved......, the networks of environmental professionals that work in the environmental organisation, in consulting and regulatory enforcement, and dominating business cultures. These have previously been identified in the literature as individually significant in relation to the evolving environmental agendas....... They are here used to describe the context in which environmental management is implemented. Based on findings from contributions to a research program studying the implementation and impact of EMS in different settings, we highlight the diverse roles that these systems play in the Thai context. EMS may over...

  15. Iptycene synthesis: A new method for attaching a 2,3-anthracene moiety to the 9,10-positions of another anthracene moiety - Exceptional conditions for a Lewis acid catalyzed Diels-Alder reaction

    Science.gov (United States)

    Chen, Yong-Shing; Hart, Harold

    1989-01-01

    An efficient three-step method for appending a 2,3-anthracene moiety to the 9,10-positions of an existing anthracene moiety is described. The first step uses excess 1,4-anthraquinone (3 equiv) and aluminum chloride (6 equiv) to obtain the anthracene-quinone cycloadduct (omission of the AlCl3 resulted in no adduct). The resulting diketone was reduced to the corresponding diol (excess LiAlH4), which was dehydrated to the arene with phosphorus oxychloride and pyridine. Specific examples include the preparation of heptipycene 8 from pentiptycene 6 (66 percent overall yield) and a similar conversion of 8 to the noniptycene 13 (75 percent overall yield). The methodology led to a markedly improved synthesis of tritriptycene 9 and the first synthesis of undecaiptycene 14.

  16. Metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in human hepatocytes: 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid is a major detoxification pathway catalyzed by cytochrome P450 1A2.

    Science.gov (United States)

    Langouët, S; Welti, D H; Kerriguy, N; Fay, L B; Huynh-Ba, T; Markovic, J; Guengerich, F P; Guillouzo, A; Turesky, R J

    2001-02-01

    Metabolic pathways of the mutagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) remain incompletely characterized in humans. In this study, the metabolism of MeIQx was investigated in primary human hepatocytes. Six metabolites were characterized by UV and mass spectroscopy. Novel metabolites were additionally characterized by 1H NMR spectroscopy. The carcinogenic metabolite, 2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline, which is formed by cytochrome P450 1A2 (P450 1A2), was found to be transformed into the N(2)-glucuronide conjugate, N(2)-(beta-1-glucosiduronyl)-2-(hydroxyamino)-3,8-dimethylimidazo[4,5-f]quinoxaline. The phase II conjugates N(2)-(3,8-dimethylimidazo[4,5-f]quinoxalin-2-yl)sulfamic acid and N(2)-(beta-1-glucosiduronyl)-2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, as well as the 7-oxo derivatives of MeIQx and N-desmethyl-MeIQx, 2-amino-3,8-dimethyl-6-hydro-7H-imidazo[4,5-f]quinoxalin-7-one (7-oxo-MeIQx), and 2-amino-6-hydro-8-methyl-7H-imidazo[4,5-f]quinoxalin-7-one (N-desmethyl-7-oxo-MeIQx), thought to be formed exclusively by the intestinal flora, were also identified. A novel metabolite was characterized as 2-amino-3-methylimidazo[4,5-f]quinoxaline-8-carboxylic acid (IQx-8-COOH), and it was the predominant metabolite formed in hepatocytes exposed to MeIQx at levels approaching human exposure. IQx-8-COOH formation is catalyzed by P450 1A2. This metabolite is a detoxication product and does not induce umuC gene expression in Salmonella typhimurium strain NM2009. IQx-8-COOH is also the principal oxidation product of MeIQx excreted in human urine [Turesky, R., et al. (1998) Chem. Res. Toxicol. 11, 217-225]. Thus, P450 1A2 is involved in both the metabolic activation and detoxication of this procarcinogen in humans. Analogous metabolism experiments were conducted with hepatocytes of untreated rats and rats pretreated with the P450 inducer 3-methylcholanthrene. Unlike human hepatocytes, the rat cell preparations did not produce IQx-8

  17. Oxygenase-Catalyzed Desymmetrization of N,N-Dialkyl-piperidine-4-carboxylic Acids**

    Science.gov (United States)

    Rydzik, Anna M; Leung, Ivanhoe K H; Kochan, Grazyna T; McDonough, Michael A; Claridge, Timothy D W; Schofield, Christopher J

    2014-01-01

    γ-Butyrobetaine hydroxylase (BBOX) is a 2-oxoglutarate dependent oxygenase that catalyzes the final hydroxylation step in the biosynthesis of carnitine. BBOX was shown to catalyze the oxidative desymmetrization of achiral N,N-dialkyl piperidine-4-carboxylates to give products with two or three stereogenic centers. PMID:25164544

  18. 井中岩屑碳酸盐含量与酸解烃关系新认识%A new viewpoint about the relationship between carbonate content and acidolysis hydrocarbon

    Institute of Scientific and Technical Information of China (English)

    杨俊; 沈忠民; 王国建; 程同锦; 卢丽

    2015-01-01

    Using unary linear regression, the relationship between carbonate content and acidolysis hydrocarbon in a well was investigated, which was different in wells with long production history, dry wells or wells with short production history. The gradient in the mudstone and related coefficient were greater than that in the sandstone in the wells with long production history, but the reverse was true in the dry wells or the wells with short production history. Then the reasons for the characteristics were analyzed from the carbonate mineral formation and the dif⁃ferent lithology’ s adsorption property. According to the characteristics, a new method was developed for hydro⁃carbon prediction in exploration wells and the re⁃examination of old wells. This method was fast and with low cost, and could effectively improve the success rate of new and old wells re⁃examination.%用一元回归的方法探寻井中岩屑碳酸盐含量与酸解烃含量的关系,发现二者斜率和相关系数在长期稳产油(气)井、干井或产期短油(气)井中特征迥异。长期稳产油(气)井中泥岩的碳酸盐含量与酸解烃含量的斜率和相关系数大于砂岩,而干井或产期短油(气)井中恰好相反,并从碳酸盐矿物形成和不同岩性吸附性能的角度分析了这种特征的形成机理。据此特征提出一种新探井含油气性预测和老井复查的方法,具有快速、低成本的特点,可有效提高探井和老井复查成功率。

  19. Gold-Catalyzed Synthesis of Heterocycles

    Science.gov (United States)

    Arcadi, Antonio

    2014-04-01

    The following sections are included: * Introduction * Synthesis of Heterocycles via Gold-Catalyzed Heteroatom Addition to Unsaturated C-C Bonds * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Cyclization of Polyunsaturated Compounds * Synthesis of Heterocyclic Compounds via α-Oxo Gold Carbenoid * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Cycloaddition Reactions * Synthesis of Heterocyclic Derivatives through Gold-Catalyzed Activation of Carbonyl Groups and Alcohols * Synthesis of Heterocyclic Compounds through Gold-Mediated C-H Bond Functionalization * Gold-Catalyzed Domino Cyclization/Oxidative Coupling Reactions * Conclusions * References

  20. Phospholipase A2 Biochemistry

    OpenAIRE

    Burke, John E.; Dennis, Edward A.

    2008-01-01

    The phospholipase A2 (PLA2) superfamily consists of many different groups of enzymes that catalyze the hydrolysis of the sn-2 ester bond in a variety of different phospholipids. The products of this reaction, a free fatty acid, and lysophospholipid have many different important physiological roles. There are five main types of PLA2: the secreted sPLA2’s, the cytosolic cPLA2’s, the Ca2+ independent iPLA2’s, the PAF acetylhydrolases, and the lysosomal PLA2’s. This review focuses on the superfam...

  1. Photodegradation of Acidolysis Lignin from BCMP

    Directory of Open Access Journals (Sweden)

    Ahmad Jahan Latibari

    2008-12-01

    Full Text Available A mild acidic dioxane extraction method was employed to isolate lignin from hardwood bleached chemimechanical pulp (BCMP. The isolated lignin was then purified and undergone elemental analysis. To study the photodegradation behavior, the lignin samples were impregnated onto the Whatman filter papers and irradiated with UV light for various periods. The photolyzed lignin was then recovered and analyzed by 1H-NMR spectroscopy. Phenylpropane-based formula (C9 of CMP pulp lignin and the photolyzed samples were then established with elemental analysis and 1H-NMR spectroscopy data. The results indicated that the benzaldehyde and benzoic acid type compounds were the main photodegradation products of BCMP lignin. The lignin photodegradation probably involved the degradation of phenylcoumaran units. Irradiation also increased the phenolic hydroxyl group content and decreased that of methoxyl groups, due to demethoxylation. The degrees of aromatic ring condensation were increased upon continuing the irradiation time, which imples the formation of condensed structures in photolyzed lignin.

  2. Thermodynamics of Enzyme-Catalyzed Reactions Database

    Science.gov (United States)

    SRD 74 Thermodynamics of Enzyme-Catalyzed Reactions Database (Web, free access)   The Thermodynamics of Enzyme-Catalyzed Reactions Database contains thermodynamic data on enzyme-catalyzed reactions that have been recently published in the Journal of Physical and Chemical Reference Data (JPCRD). For each reaction the following information is provided: the reference for the data, the reaction studied, the name of the enzyme used and its Enzyme Commission number, the method of measurement, the data and an evaluation thereof.

  3. Iridium-Catalyzed Allylic Substitution

    Science.gov (United States)

    Hartwig, John F.; Pouy, Mark J.

    Iridium-catalyzed asymmetric allylic substitution has become a valuable method to prepare products from the addition of nucleophiles at the more substituted carbon of an allyl unit. The most active and selective catalysts contain a phosphoramidite ligand possessing at least one arylethyl substituent on the nitrogen atom of the ligand. In these systems, the active catalyst is generated by a base-induced cyclometalation at the methyl group of this substituent to generate an iridium metalacycle bound by the COD ligand of the [Ir(COD)Cl]2 precursor and one additional labile dative ligand. Such complexes catalyze the reactions of linear allylic esters with alkylamines, arylamines, phenols, alcohols, imides, carbamates, ammonia, enolates and enolate equivalents, as well as typical stabilized carbon nucleophiles generated from malonates and cyanoesters. Iridium catalysts for enantioselective allylic substitution have also been generated from phosphorus ligands with substituents bound by heteroatoms, and an account of the studies of such systems, along with a description of the development of iridium catalysts is included.

  4. Transition metal-catalyzed functionalization of pyrazines

    NARCIS (Netherlands)

    Nikishkin, Nicolai I.; Huskens, Jurriaan; Verboom, Willem

    2013-01-01

    Transition metal-catalyzed reactions are generally used for carbon–carbon bond formation on pyrazines and include, but are not limited to, classical palladium-catalyzed reactions like Sonogashira, Heck, Suzuki, and Stille reactions. Also a few examples of carbon–heteroatom bond formation in pyrazine

  5. Advances in lipase-catalyzed esterification reactions.

    Science.gov (United States)

    Stergiou, Panagiota-Yiolanda; Foukis, Athanasios; Filippou, Michalis; Koukouritaki, Maria; Parapouli, Maria; Theodorou, Leonidas G; Hatziloukas, Efstathios; Afendra, Amalia; Pandey, Ashok; Papamichael, Emmanuel M

    2013-12-01

    Lipase-catalyzed esterification reactions are among the most significant chemical and biochemical processes of industrial relevance. Lipases catalyze hydrolysis as well as esterification reactions. Enzyme-catalyzed esterification has acquired increasing attention in many applications, due to the significance of the derived products. More specifically, the lipase-catalyzed esterification reactions attracted research interest during the past decade, due to an increased use of organic esters in biotechnology and the chemical industry. Lipases, as hydrolyzing agents are active in environments, which contain a minimum of two distinct phases, where all reactants are partitioned between these phases, although their distribution is not fixed and changes as the reaction proceeds. The kinetics of the lipase-catalyzed reactions is governed by a number of factors. This article presents a thorough and descriptive evaluation of the applied trends and perspectives concerning the enzymatic esterification, mainly for biofuel production; an emphasis is given on essential factors, which affect the lipase-catalyzed esterification reaction. Moreover, the art of using bacterial and/or fungal strains for whole cell biocatalysis purposes, as well as carrying out catalysis by various forms of purified lipases from bacterial and fungal sources is also reviewed.

  6. Continuous Production of Structured Phospholipids in a Packed Red Reactor with Lipase from Thermomyces lanuginosa

    DEFF Research Database (Denmark)

    Vikbjerg, Anders Falk; Peng, Lifeng; Mu, Huiling;

    2005-01-01

    The possibilities of producing structured phospholipids by lipase-catalyzed acidolysis between soybean phospholipids and caprylic acid were examined in continuous packed bed enzyme reactors. Acidolysis reactions were performed in both a solvent system and a solvent-free system with the commercial...

  7. Attractor Explosions and Catalyzed Vacuum Decay

    Energy Technology Data Exchange (ETDEWEB)

    Green, Daniel; Silverstein, Eva; Starr, David

    2006-05-05

    We present a mechanism for catalyzed vacuum bubble production obtained by combining moduli stabilization with a generalized attractor phenomenon in which moduli are sourced by compact objects. This leads straightforwardly to a class of examples in which the Hawking decay process for black holes unveils a bubble of a different vacuum from the ambient one, generalizing the new endpoint for Hawking evaporation discovered recently by Horowitz. Catalyzed vacuum bubble production can occur for both charged and uncharged bodies, including Schwarzschild black holes for which massive particles produced in the Hawking process can trigger vacuum decay. We briefly discuss applications of this process to the population and stability of metastable vacua.

  8. Enantioselective, iridium-catalyzed monoallylation of ammonia.

    Science.gov (United States)

    Pouy, Mark J; Stanley, Levi M; Hartwig, John F

    2009-08-19

    Highly enantioselective, iridium-catalyzed monoallylations of ammonia are reported. These reactions occur with electron-neutral, -rich, and -poor cinnamyl carbonates, alkyl and trityloxy-substituted allylic carbonates, and dienyl carbonates in moderate to good yields and excellent enantioselectivities. This process is enabled by the use of an iridium catalyst that does not require a Lewis acid for activation and that is stable toward a large excess of ammonia. This selective formation of primary allylic amines allows for one-pot syntheses of heterodiallylamines and allylic amides that are not otherwise accessible via iridium-catalyzed allylic amination without the use of blocking groups and protective group manipulations.

  9. Palladium catalyzed hydrogenation of bio-oils and organic compounds

    Science.gov (United States)

    Elliott, Douglas C.; Hu, Jianli; Hart, Todd R.; Neuenschwander, Gary G.

    2008-09-16

    The invention provides palladium-catalyzed hydrogenations of bio-oils and certain organic compounds. Experimental results have shown unexpected and superior results for palladium-catalyzed hydrogenations of organic compounds typically found in bio-oils.

  10. Zeolite 5A Catalyzed Etherification of Diphenylmethanol

    Science.gov (United States)

    Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

    2009-01-01

    An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The…

  11. Catalyzing curriculum evolution in graduate science education.

    Science.gov (United States)

    Gutlerner, Johanna L; Van Vactor, David

    2013-05-09

    Strategies in life science graduate education must evolve in order to train a modern workforce capable of integrative solutions to challenging problems. Our institution has catalyzed such evolution through building a postdoctoral Curriculum Fellows Program that provides a collaborative and scholarly education laboratory for innovation in graduate training.

  12. Mechanochemical ruthenium-catalyzed olefin metathesis.

    Science.gov (United States)

    Do, Jean-Louis; Mottillo, Cristina; Tan, Davin; Štrukil, Vjekoslav; Friščić, Tomislav

    2015-02-25

    We describe the development of a mechanochemical approach for Ru-catalyzed olefin metathesis, including cross-metathesis and ring-closing metathesis. The method uses commercially available catalysts to achieve high-yielding, rapid, room-temperature metathesis of solid or liquid olefins on a multigram scale using either no or only a catalytic amount of a liquid.

  13. Pinacol Coupling Reactions Catalyzed by Active Zinc

    Institute of Scientific and Technical Information of China (English)

    Hui ZHAO; Wei DENG; Qing Xiang GUO

    2005-01-01

    Pinacol coupling reactions catalyzed by active zinc revealed high activity and extensive suitability. The efficiency of the reaction was improved apparently owing to decreasing reductive potential of zinc. In addition, the results indicated that the zinc activity has a direct relation to the coupling reactivity compared to untreated zinc or other general active zinc.

  14. Rhodium-catalyzed restructuring of carbon frameworks.

    Science.gov (United States)

    Murakami, Masahiro

    2010-10-01

    Metal-catalyzed reactions involving an elementary step which cleaves a carbon-carbon bond provide unique organic transformations. Restructuring reactions recently developed in our laboratory, through which the carbon framework of a starting substance is restructured into a totally different carbon framework, are discussed, with the possibility of applying such methods to the synthesis of natural products.

  15. Lysophosphatidylcholine synthesis by lipase-catalyzed ethanolysis.

    Science.gov (United States)

    Yang, Guolong; Yang, Ruoxi; Hu, Jingbo

    2015-01-01

    Lysophosphatidylcholine (LPC) is amphiphilic substance, and possesses excellent physiological functions. In this study, LPC was prepared through ethanolysis of phosphatidylcholine (PC) in n-hexane or solvent free media catalyzed by Novozym 435 (from Candida antarctica), Lipozyme TLIM (from Thermomcyces lanuginosus) and Lipozyme RMIM (from Rhizomucor miehei). The results showed that three immobilized lipases from Candida Antarctica, Thermomcyces lanuginosus and Rhizomucor miehei could catalyze ethanolysis of PC efficiently. In n-hexane, the LPC conversions of ethanolysis of PC catalyzed by Novozyme 435, Lipozyme TLIM and Lipozyme RMIM could reach to 98.5 ± 1.6%, 94.6 ± 1.4% and 93.7 ± 1.8%, respectively. In solvent free media, the highest LPC conversions of ethanolysis of PC catalyzed by Novozyme 435, Lipozyme TL IM and Lipozyme RM IM were 97.7 ± 1.7%, 93.5 ± 1.2% and 93.8 ± 1.9%, respectively. The catalytic efficiencies of the three lipases were in the order of Novozyme 435 > Lipozyme TLIM > Lipozyme RMIM. Furthermore, their catalytic efficiencies in n-hexane were better than those in solvent free media.

  16. Biodiesel production by enzyme-catalyzed transesterification

    Directory of Open Access Journals (Sweden)

    Stamenković Olivera S.

    2005-01-01

    Full Text Available The principles and kinetics of biodiesel production from vegetable oils using lipase-catalyzed transesterification are reviewed. The most important operating factors affecting the reaction and the yield of alkyl esters, such as: the type and form of lipase, the type of alcohol, the presence of organic solvents, the content of water in the oil, temperature and the presence of glycerol are discussed. In order to estimate the prospects of lipase-catalyzed transesterification for industrial application, the factors which influence the kinetics of chemically-catalysed transesterification are also considered. The advantages of lipase-catalyzed transesterification compared to the chemically-catalysed reaction, are pointed out. The cost of down-processing and ecological problems are significantly reduced by applying lipases. It was also emphasized that lipase-catalysed transesterification should be greatly improved in order to make it commercially applicable. The further optimization of lipase-catalyzed transesterification should include studies on the development of new reactor systems with immobilized biocatalysts and the addition of alcohol in several portions, and the use of extra cellular lipases tolerant to organic solvents, intracellular lipases (i.e. whole microbial cells and genetically-modified microorganisms ("intelligent" yeasts.

  17. Palladium-Catalyzed Intramolecular Aminofluorination of Styrenes%Palladium-Catalyzed Intramolecular Aminofluorination of Styrenes

    Institute of Scientific and Technical Information of China (English)

    徐涛; 邱水发; 刘国生

    2011-01-01

    A novel palladium-catalyzed intramolecular oxidative aminofluorination of styrenes has been developed by using NFSI as fluorinating reagent. This reaction represented an efficient method for the synthesis of 2-aryl-3-fluoropyrrolidine derivatives.

  18. Kinetics of aggregation growth with competition between catalyzed birth and catalyzed death

    Institute of Scientific and Technical Information of China (English)

    Wang Hai-Feng; Lin Zhen-Quan; Gao Yan

    2008-01-01

    An aggregation growth model of three species A, B and C with the competition between catalyzed birth and catalyzed death is proposed. Irreversible aggregation occurs between any two aggregates of the like species with the constant rate kernels In(n = 1, 2, 3). Meanwhile, a monomer birth of an A species aggregate of size k occurs under the catalysis of a B species aggregate of size j with the catalyzed birth rate kernel K(k,j) = Kkjv, and a monomer death of an A species aggregate of size k occurs under the catalysis of a C species aggregate of size j with the catalyzed death rate kernel L(k, j) = Lkjv, where v is a parameter reflecting the dependence of the catalysis reaction rates of birth and death on the size of catalyst aggregate. The kinetic evolution behaviours of the three species are investigated by the rate equation approach based on the mean-field theory. The form of the aggregate size distribution of A species ak(t) is found to be dependent crucially on the competition between the catalyzed birth and death of A species, as well as the irreversible aggregation processes of the three species: (1) In the v < 0 case, the irreversible aggregation dominates the process, and ak(t) satisfies the conventional scaling form; (2) In the v ≥ 0 case, the competition between the catalyzed birth and death dominates the process. When the catalyzed birth controls the process, ak(t) takes the conventional or generalized scaling form. While the catalyzed death controls the process, the scaling description of the aggregate size distribution breaks down completely.

  19. Palladium-Catalyzed Environmentally Benign Acylation.

    Science.gov (United States)

    Suchand, Basuli; Satyanarayana, Gedu

    2016-08-05

    Recent trends in research have gained an orientation toward developing efficient strategies using innocuous reagents. The earlier reported transition-metal-catalyzed carbonylations involved either toxic carbon monoxide (CO) gas as carbonylating agent or functional-group-assisted ortho sp(2) C-H activation (i.e., ortho acylation) or carbonylation by activation of the carbonyl group (i.e., via the formation of enamines). Contradicting these methods, here we describe an environmentally benign process, [Pd]-catalyzed direct carbonylation starting from simple and commercially available iodo arenes and aldehydes, for the synthesis of a wide variety of ketones. Moreover, this method comprises direct coupling of iodoarenes with aldehydes without activation of the carbonyl and also without directing group assistance. Significantly, the strategy was successfully applied to the synthesis n-butylphthalide and pitofenone.

  20. Chiral Diamine-catalyzed Asymmetric Aldol Reaction

    Institute of Scientific and Technical Information of China (English)

    LI Hui; XU Da-zhen; WU Lu-lu; WANG Yong-mei

    2012-01-01

    A highly efficient catalytic system composed of a simple and commercially available chiral primary diamine (1R,2R)-cyclohexane-1,2-diamine(6) and trifluoroacetic acid(TFA) was employed for asymmetric Aldol reaction in i-PrOH at room temperature.A loading of 10%(molar fraction) catalyst 6 with TFA as a cocatalyst could catalyze the Aldol reactions of various ketones or aldehydes with a series of aromatic aldehydes,furnishing Aldol products in moderate to high yields(up to >99%) with enantioselectivities of up to >99% and diastereoselectivities of up to 99:1.

  1. Biginelli reaction catalyzed by copper nanoparticles.

    Directory of Open Access Journals (Sweden)

    Manika Dewan

    Full Text Available We recently reported a novel synthesis of copper nanoparticles from copper sulphate utilizing the charge-compensatory effect of ionic liquid [bmim]BF(4 and ethylene glycol. The nanoparticles were characterized and found to be stable for one year. Here we hypothesize that the stabilized nanoparticles should be able to catalyze one-pot multicomponent organic reactions. We show that the nanoparticles catalyzed Biginelli reaction at room temperature to give the product 3,4-dihydopyrimidinone (>90% yield in ~15 minutes from aldehydes, β-diketoester (ethylacetoacetate and urea (or thiourea. . Remarkably, such high yields and rapid kinetics was found to be independent of the electronic density on the reactant aryl-aldehyde. This was probably because even the surface-active particles reacted faster in the presence of ionic liquid as compared to conventional methods. The heterocyclic dihydropyrimidinones (DHPMs and their derivatives are widely used in natural and synthetic organic chemistry due to their wide spectrum of biological and therapeutic properties (resulting from their antibacterial, antiviral, antitumor and anti-inflammatory activities. Our method has an easy work-up procedure and the nanoparticles could be recycled with minimal loss of efficiency.

  2. Synthetic applications of gold-catalyzed ring expansions

    Directory of Open Access Journals (Sweden)

    Cristina Nevado

    2011-06-01

    Full Text Available The development of new methodologies catalyzed by late transition metals involving cycloisomerizations of strained rings can open new venues for the synthesis of structurally complex molecules with interesting biological activities. Herein we summarize, from both a synthetic as well as a mechanistic point of view, the most recent developments in gold-catalyzed ring expansions.

  3. CO2碳酸化石灰岩酸解产物回收乙酸及副产沉淀碳酸钙%CO2 carbonation of calcium acetate derived from acidolysis of natural CaCO3 for recycling of acetic acid and production of precipitated calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    杨政; 岳海荣; 周向葛; 梁斌; 谢和平

    2014-01-01

    Acetic acid dissolution of limestone for formation of cavity is a kind of environmental approach to fabricating underground storage and preparing precipitated calcium carbonate. This process is an integrated technology consisting of acetic acid dissolution of limestone and CO2 carbonation of calcium acetate. The kinetics of limestone acidolysis with acetic acid was investigated. Orthogonal experiments were conducted with emphasis on operation conditions (i.e., concentration of calcium acetate, pressure of CO2, reaction temperature, and reaction time) of the carbonation reaction. The highest conversion of calcium acetate (23.13%) was achieved at the calcium acetate concentration of 0.631 mol·L-1, CO2 pressure of 5 MPa, reaction temperature of 80℃ and reaction for 50 min. The product of calcium carbonate was analyzed and could meet the requirements of Chinese national standard.%乙酸酸解石灰石造腔是一种建造地下储库同时环保地开采石灰岩制备沉淀碳酸钙的新方法。通过耦合乙酸酸解石灰石及酸解产物乙酸钙 CO2碳酸化的工艺过程,研究了乙酸酸解石灰岩的表面反应动力学和乙酸钙 CO2碳酸化的工艺技术条件。采用正交实验分析法,研究了CO2碳酸化反应中乙酸钙浓度、反应温度、CO2压力、反应时间对乙酸钙碳酸化反应制沉淀碳酸钙的影响,并通过正交实验确定了最优化操作条件。实验结果表明,乙酸酸解反应速率主要受乙酸浓度控制。CO2碳酸化反应在当乙酸钙溶液浓度为0.631 mol·L-1,CO2压力为5.0 MPa,温度为80℃,反应时间为50 min时CO2碳酸化效率达到最高(23.13%),生成的沉淀碳酸钙产品各项指标均符合中国国标优级要求。

  4. Diverse Functions of Secretory Phospholipases A2

    OpenAIRE

    Preetha Shridas; Webb, Nancy R

    2014-01-01

    Phospholipase A2 enzymes (PLA2s) catalyze the hydrolysis of glycerophospholipids at their sn-2 position releasing free fatty acids and lysophospholipids. Mammalian PLA2s are classified into several categories of which important groups include secreted PLA2s (sPLA2s) and cytosolic PLA2s (cPLA2s) that are calcium-dependent for their catalytic activity and calcium-independent cytosolic PLA2s (iPLA2s). Platelet-activating factor acetylhydrolases (PAF-AHs), lysosomal PLA2s, and adipose-specific ...

  5. 假丝酵母脂肪酶(Candida sp.99-125)催化合成人乳脂替代品及酶重复使用的研究%The synthesis of human milk fat substitutes catalyzed by Candida sp.99-125 lipase and resue of the lipase reuse

    Institute of Scientific and Technical Information of China (English)

    李玲; 叶贤春; 邓利; 聂开立; 刘珞; 李昕倩

    2012-01-01

    以三棕榈酸甘油酯(PPP)和油酸(O)为原料,假丝酵母脂肪酶(Candida sp.99-125)为催化剂合成人乳脂替代品1,3-二油酸2-棕榈酸甘油三酯(OPO).研究了Candida sp.99-125脂肪酶的催化机理、酶使用量以及Candi-da sp.99-125脂肪酶的重复使用.研究结果表明:Candida sp.99-125脂肪酶的催化机理是先酸解PPP sn-1位的棕榈酸,然后再与sn-3位的棕榈酸反应;当脂肪酶用量为37500U,反应温度为43℃,经过3h反应后,OPO的转化率可达41.24%;补加初次反应脂肪酶使用量50%的脂肪酶后,重新加入底物反应48 h,OPO的转化率可维持在40%左右,且平均反应速率保持稳定.%The human milk fat substitute ( HMFS) 1 ,3-oleic acid 2-palmitic acid triglyceride ( OPO) has been synthesized by Candida sp. 99-125 lipase-catalyzed acidolysis using palmitic acid triglyceride (PPP) and oleic acid (0) as reaction substrates. The catalytic mechanism for the action of Candida sp. 99-125 lipase and the reuse of the enzyme were studied. The results showed that; the Candida sp. 99-125 lipase initially catalyzes the palmitic acid at the sn-1 position, and subsequently at the sn-3 position; the OPO conversion rate approached 41. 24% at a temperature of 43 t , with a Candida sp. 99-125 lipase load of 37500U, and a time of 3h; it was possible to maintain the reaction rate close to the initial reaction rate, with the conversion ratio of the product OPO approaching 40% , by adding 50% new enzyme to recovered lipase and reacting for 48 h with new substrates.

  6. Particle growth by acid-catalyzed heterogeneous reactions of organic carbonyls on preexisting aerosols.

    Science.gov (United States)

    Jang, Myoseon; Carroll, Brian; Chandramouli, Bharadwaj; Kamens, Richard M

    2003-09-01

    Aerosol growth by the heterogeneous reactions of different aliphatic and alpha,beta-unsaturated carbonyls in the presence/absence of acidified seed aerosols was studied in a 2 m long flow reactor (2.5 cm i.d.) and a 0.5-m3 Teflon film bag under darkness. For the flow reactor experiments, 2,4-hexadienal, 5-methyl-3-hexen-2-one, 2-cyclohexenone, 3-methyl-2-cyclopentenone, 3-methyl-2-cyclohexenone, and octanal were studied. The carbonyls were selected based on their reactivity for acid-catalyzed reactions, their proton affinity, and their similarity to the ring-opening products from the atmospheric oxidation of aromatics. To facilitate acid-catalyzed heterogeneous hemiacetal/acetal formation, glycerol was injected along with inorganic seed aerosols into the flow reactor system. Carbonyl heterogeneous reactions were accelerated in the presence of acid catalysts (H2SO4), leading to higher aerosol yields than in their absence. Aldehydes were more reactive than ketones for acid-catalyzed reactions. The conjugated functionality also resulted in higher organic aerosol yieldsthan saturated aliphatic carbonyls because conjugation with the olefinic bond increases the basicity of the carbonyl leading to increased stability of the protonated carbonyl. Aerosol population was measured from a series of sampling ports along the length of the flow reactor using a scanning mobility particle sizer. Fourier transform infrared spectrometry of either an impacted liquid aerosol layer or direct reaction of carbonyls as a thin liquid layer on a zinc selenide FTIR disk was employed to demonstrate the direct transformation of chemical functional groups via the acid-catalyzed reactions. These results strongly indicate that atmospheric multifunctional organic carbonyls, which are created by atmospheric photooxidation reactions, can contribute significantly to secondary organic aerosol formation through acid-catalyzed heterogeneous reactions. Exploratory studies in 25- and 190-m3 outdoor chambers

  7. Mechanisms of bacterially catalyzed reductive dehalogenation

    Energy Technology Data Exchange (ETDEWEB)

    Picardal, F.W.

    1992-12-31

    Nine bacteria were tested for the ability to dehalogenate tetrachloromethane (CT), tetrachloroethene (PCE), and 1, 1, 1-trichloroethane (TCA) under anaerobic conditions. Three bacteria were able to reductively dehalogenate CT. Dehalogenation ability was not readily linked to a common metabolism or changes in culture redox potential. None of the bacteria tested were able to dehalogenate PCE or TCA. One of the bacteria capable of dehalogenating CT, Shewanella putrefaciens, was chosen as a model organism to study mechanisms of bacterially catalyzed reductive dehalogenation. The effect of a variety of alternate electron acceptors on CT dehalogenation ability by S. putrefaciens was determined. oxygen and nitrogen oxides were inhibitory but Fe (III), trimethylamine oxide, and fumarate were not. A model of the electron transport chain of S. putrefaciens was developed to explain inhibition patterns. A period of microaerobic growth prior to CT exposure increased the ability of S. putrefaciens to dehalogenate CT. A microaerobic growth period also increased cytochrome concentrations. A relationship between cytochrome content and dehalogenation ability was developed from studies in which cytochrome concentrations in S. putrefaciens were manipulated by changing growth conditions. Stoichiometry studies using {sup 14}C-CT suggested that CT was first reduced to form a trichloromethyl radical. Reduction of the radical to produce chloroform and reaction of the radical with cellular biochemicals explained observed product distributions. Carbon dioxide or other fully dehalogenated products were not found.

  8. Cyclopalladated Ferrocenylimine Catalyzed Chlorination of 2-Arylbenzoxazoles%Cyclopalladated Ferrocenylimine Catalyzed Chlorination of 2-Arylbenzoxazoles

    Institute of Scientific and Technical Information of China (English)

    冷瑜婷; 杨帆; 吴养洁; 李克

    2011-01-01

    An efficient and facile protocol for palladacycle-catalyzed chlorination of 2-arylbenzoxazoles was developed. The results represent the first examples involving the palladacycle as the catalyst for such chlorination. This chlori- nation was not a ligand-directed ortho-C--H activation, but an electrophilic substitution process at the para-position of the nitrogen atom in the benzo ring of benzoxazole moiety, the regiochemistry of which had been confirmed by HMBC spectral analysis. The catalytic system could tolerate various halogen atoms, such as F, Cl and Br, affording the corresponding products in moderate to excellent yields.

  9. Functioned Calix[4]arenes as Artificial Enzymes Catalyze Aldol Condensation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Aldolase models derived from calix[4]arene were designed and synthesized. The aldol condensation of p-nitrobenzaldehyde with acetone was catalyzed by the synthetic enzymes proceeded under mild conditions to offer chiefly aldol-type product in good yield.

  10. Diastereoselective Pt catalyzed cycloisomerization of polyenes to polycycles.

    Science.gov (United States)

    Geier, Michael J; Gagné, Michel R

    2014-02-26

    Application of a tridentate NHC containing pincer ligand to Pt catalyzed cascade cyclization reactions has allowed for the catalytic, diastereoselective cycloisomerization of biogenic alkene terminated substrates to the their polycyclic counterparts.

  11. Lipase catalyzed synthesis of epoxy-fatty acids

    Institute of Scientific and Technical Information of China (English)

    CHEN, Qian; LI, Zu-Yi

    2000-01-01

    Lipase catalyzed synthesis of epoxy-fatty acidas from unsaturated carboxylic acids was investigated.Under mild conditions unsaturated arboxylic acids were convcveed to peroxide,then the unsaturated peroxycarboxylic acids epoxidised the C=C bond of themselves

  12. Gold-Catalyzed Regioselective Dimerization of Aliphatic Terminal Alkynes.

    Science.gov (United States)

    Sun, Sheng; Kroll, Julien; Luo, Yingdong; Zhang, Liming

    2012-01-01

    A gold-catalyzed regioselective homodimerization of aliphatic terminal alkynes is described. Bulky and less Lewis acidic tBuXPhosAuNTf(2) is the preferred catalyst, and the additive, anhydrous NaOAc, substantially facilitates the reaction.

  13. Homocoupling of Aryl Bromides Catalyzed by Nickel Chloride in Pyridine

    Institute of Scientific and Technical Information of China (English)

    TAO, Xiao-Chun; ZHOU, Wei; ZHANG, Yue-Ping; DAI, Chun-ya; SHEN, Dong; HUANG, Mei

    2006-01-01

    Pyridine was used as a solvent for homocoupling of aryl bromides catalyzed by nickel chloride/triarylphosphine in the presence of zinc and recycled easily. Triphenylphosphine was the best ligand for nickel in this coupling reaction.

  14. Development and industrial application of catalyzer for low-temperature hydrogenation hydrolysis of Claus tail gas

    OpenAIRE

    Honggang Chang; Ronghai Zhu; Zongshe Liu; Jinlong He; Chongrong Wen; Sujuan Zhang; Yang Li

    2015-01-01

    With the implementation of more strict national environmental protection laws, energy conservation, emission reduction and clean production will present higher requirements for sulfur recovery tail gas processing techniques and catalyzers. As for Claus tail gas, conventional hydrogenation catalyzers are gradually being replaced by low-temperature hydrogenation catalyzers. This paper concentrates on the development of technologies for low-temperature hydrogenation hydrolysis catalyzers, prepar...

  15. LIPASE-CATALYZED TRANSESTERIFICATION OF PALM KERNEL OIL WITH DIALKYLCARBONATES

    OpenAIRE

    Tjahjono Herawan; M. Rüsch Gen. Klaas

    2014-01-01

    Lipase-catalyzed transesterifications-especially in a solvent-free medium-are important for industrial applications because such systems would have an enormous advantage by avoiding the problem of separation, toxicity and flammability of organic solvents. However, the organic solvent-free alcoholysis, especially methanolysis, does not give high conversions. The same problem also occurs when ethyl or methyl acetate are used as acyl acceptors. The main problems of lipase-catalyzed organic solve...

  16. Copper-Catalyzed Aerobic C–H Trifluoromethylation of Phenanthrolines

    Science.gov (United States)

    Zhu, Cheng-Liang; Zhang, Yong-Qiang; Yuan, Yong-An

    2016-01-01

    Direct C–H trifluoromethylation of heterocycles is a valuable transformation. In particular, nonprecious metal-catalyzed C–H trifluoromethylation processes, which do not proceed through CF3 radical species, have been less developed. In this cluster report, a new copper-catalyzed aerobic C–H trifluoromethylation of phenanthrolines is described. This transformation affords trifluoromethylated phenanthrolines that have not been synthesized and preliminary mechanistic studies suggest that the CF3 group transfer may occur through cooperative activation. PMID:26855477

  17. Conservation Kickstart- Catalyzing Conservation Initiatives Worldwide

    Science.gov (United States)

    Treinish, G.

    2014-12-01

    Adventurers and Scientists for Conservation (ASC) is a nonprofit organization that collects environmental data to catalyze conservation initiatives worldwide. Adventure athletes have the skills and motivation to reach the most remote corners of the world. ASC utilizes those skills to provide the scientific community with data while providing the outdoor community with purpose beyond the personal high of reaching a summit or rowing across an ocean. We carefully select projects, choosing partnerships that will maximize the impact of ASC volunteers. Each project must have a clear path to a tangible conservation outcome and demonstrate a clear need for our brand of volunteers. We partner with government agencies, universities, and independant reseachers to kickstart data collection efforts around the world. Last year, through a partnership with the Olympic National Forest, 20 volunteers from the Seattle area set up and monitored camera traps in an effort to survey for costal Pacific marten. Our work led to the species' listing as "critically imperiled" with NatureServe. A partnership with the inaugural Great Pacific Race, engaging trans-Pacific rowing teams, searched for microplastics in the Pacific Ocean as part of our ongoing microplastics campaign. In a multi-year partnership with the American Prairie Reserve (APR), ASC volunteer crews live and work on the Reserve collecting wildlife data year round. The data we obtain directly informs the Reserve's wildlife management decisions. On this project, our crews have safely and effectively navigated temperature extremes from -30 degrees to 100+ degrees while traveling in a remote location. We are currently scouting projects in the Okavango Delta of Botswana and the rainforest of Suriname where we will be able to cover large amounts of area in a short periord of time. ASC is at the crossroads of the adventure and coservation science communities. Our approach of answering specific questions by using highly skilled and

  18. Captan impairs CYP-catalyzed drug metabolism in the mouse.

    Science.gov (United States)

    Paolini, M; Barillari, J; Trespidi, S; Valgimigli, L; Pedulli, G F; Cantelli-Forti, G

    1999-11-30

    To investigate whether the fungicide captan impairs CYP-catalyzed drug metabolism in murine liver, kidney and lung, the modulation of the regio- and stereo-selective hydroxylation of testosterone, including 6beta-(CYP3A), 6alpha-(CYP2A1 and CYP2B1) and 16alpha-(CYP2B9) oxidations was studied. Specific substrates as probes for different CYP isoforms such as p-nitrophenol (CYP2E1), pentoxyresorufin (CYP2B1), ethoxyresorufin (CYP1A1), aminopyrine (CYP3A), phenacetin and methoxyresorufin (CYP1A2), and ethoxycoumarin (mixed) were also considered. Daily doses of captan (7.5 or 15 mg/kg b.w., i.p.) were administered to different groups of Swiss Albino CD1 mice of both sexes for 1 or 3 consecutive days. While a single dose of this fungicide did not affect CYP-machinery, repeated treatment significantly impaired the microsomal metabolism; in the liver, for example, a general inactivating effect was observed, with the sole exception of testosterone 2alpha-hydroxylase activity which was induced up to 8.6-fold in males. In vitro studies showed that the mechanism-based inhibition was related to captan metabolites rather than the parental compound. In the kidney, both CYP3A- and CYP1A2-linked monooxygenases were significantly induced (2-fold) by this pesticide. Accelerated phenacetin and methoxyresorufin metabolism (CYP1A2) was also observed in the lung. Data on CYP3A (kidney) and CYP1A2 (kidney and lung) induction were corroborated by Western immunoblotting using rabbit polyclonal anti-CYP3A1/2 and CYP1A1/2 antibodies. By means of electron spin resonance (EPR) spectrometry coupled to a spin-trapping technique, it was found that the recorded induction generates a large amounts of the anion radical superoxide (O*2-) either in kidney or lung microsomes. These findings suggest that alterations in CYP-associated activities by captan exposure may result in impaired (endogenous) metabolism as well as of coadministered drugs with significant implications for their disposition. The

  19. Homologation of α-aryl amino acids through quinone-catalyzed decarboxylation/Mukaiyama-Mannich addition.

    Science.gov (United States)

    Haugeberg, Benjamin J; Phan, Johnny H; Liu, Xinyun; O'Connor, Thomas J; Clift, Michael D

    2017-03-09

    A new method for amino acid homologation by way of formal C-C bond functionalization is reported. This method utilizes a 2-step/1-pot protocol to convert α-amino acids to their corresponding N-protected β-amino esters through quinone-catalyzed oxidative decarboxylation/in situ Mukaiyama-Mannich addition. The scope and limitations of this chemistry are presented. This methodology provides an alternative to the classical Arndt-Eistert homologation for accessing β-amino acid derivatives. The resulting N-protected amine products can be easily deprotected to afford the corresponding free amines.

  20. Palladium-Catalyzed Modification of Unprotected Nucleosides, Nucleotides, and Oligonucleotides

    Directory of Open Access Journals (Sweden)

    Kevin H. Shaughnessy

    2015-05-01

    Full Text Available Synthetic modification of nucleoside structures provides access to molecules of interest as pharmaceuticals, biochemical probes, and models to study diseases. Covalent modification of the purine and pyrimidine bases is an important strategy for the synthesis of these adducts. Palladium-catalyzed cross-coupling is a powerful method to attach groups to the base heterocycles through the formation of new carbon-carbon and carbon-heteroatom bonds. In this review, approaches to palladium-catalyzed modification of unprotected nucleosides, nucleotides, and oligonucleotides are reviewed. Polar reaction media, such as water or polar aprotic solvents, allow reactions to be performed directly on the hydrophilic nucleosides and nucleotides without the need to use protecting groups. Homogeneous aqueous-phase coupling reactions catalyzed by palladium complexes of water-soluble ligands provide a general approach to the synthesis of modified nucleosides, nucleotides, and oligonucleotides.

  1. The Structural Basis of Ribozyme-Catalyzed RNA Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, M.P.; Scott, W.G.; /UC, Santa Cruz

    2007-07-12

    Life originated, according to the RNA World hypothesis, from self-replicating ribozymes that catalyzed ligation of RNA fragments. We have solved the 2.6 angstrom crystal structure of a ligase ribozyme that catalyzes regiospecific formation of a 5' to 3' phosphodiester bond between the 5'-triphosphate and the 3'-hydroxyl termini of two RNA fragments. Invariant residues form tertiary contacts that stabilize a flexible stem of the ribozyme at the ligation site, where an essential magnesium ion coordinates three phosphates. The structure of the active site permits us to suggest how transition-state stabilization and a general base may catalyze the ligation reaction required for prebiotic RNA assembly.

  2. Highly efficient palladium-catalyzed hydrostannation of ethyl ethynyl ether.

    Science.gov (United States)

    Andrews, Ian P; Kwon, Ohyun

    2008-12-08

    The palladium-catalyzed hydrostannation of acetylenes is widely exploited in organic synthesis as a means of forming vinyl stannanes for use in palladium-catalyzed cross-coupling reactions. Application of this methodology to ethyl ethynyl ether results in an enol ether that is challenging to isolate from the crude reaction mixture because of incompatibility with typical silica gel chromatography. Reported here is a highly efficient procedure for the palladium-catalyzed hydrostannation of ethyl ethynyl ether using 0.1% palladium(0) catalyst and 1.0 equiv of tributyltin hydride. The product obtained is a mixture of regioisomers that can be carried forward with exclusive reaction of the beta-isomer. This method is highly reproducible; relative to previously reported procedures, it is more economical and involves a more facile purification procedure.

  3. Microbial-Catalyzed Biotransformation of Multifunctional Triterpenoids Derived from Phytonutrients

    Directory of Open Access Journals (Sweden)

    Syed Adnan Ali Shah

    2014-07-01

    Full Text Available Microbial-catalyzed biotransformations have considerable potential for the generation of an enormous variety of structurally diversified organic compounds, especially natural products with complex structures like triterpenoids. They offer efficient and economical ways to produce semi-synthetic analogues and novel lead molecules. Microorganisms such as bacteria and fungi could catalyze chemo-, regio- and stereospecific hydroxylations of diverse triterpenoid substrates that are extremely difficult to produce by chemical routes. During recent years, considerable research has been performed on the microbial transformation of bioactive triterpenoids, in order to obtain biologically active molecules with diverse structures features. This article reviews the microbial modifications of tetranortriterpenoids, tetracyclic triterpenoids and pentacyclic triterpenoids.

  4. Synthesis of heterocycles through transition-metal-catalyzed isomerization reactions

    DEFF Research Database (Denmark)

    Ishøy, Mette; Nielsen, Thomas Eiland

    2014-01-01

    of structurally complex and diverse heterocycles. In this Concept article, we attempt to cover this area of research through a selection of recent versatile examples. A sea of opportunities! Transition-metal-catalyzed isomerization of N- and O-allylic compounds provides a mild, selective and synthetically......Metal-catalyzed isomerization of N- and O-allylic systems is emerging as an effective method to form synthetically useful iminium and oxocarbenium intermediates. In the presence of tethered nucleophiles, several recent examples illuminate this approach as a powerful strategy for the synthesis...

  5. Graphene oxide catalyzed cis-trans isomerization of azobenzene

    Directory of Open Access Journals (Sweden)

    Dongha Shin

    2014-09-01

    Full Text Available We report the fast cis-trans isomerization of an amine-substituted azobenzene catalyzed by graphene oxide (GO, where the amine functionality facilitates the charge transfer from azobenzene to graphene oxide in contrast to non-substituted azobenzene. This catalytic effect was not observed in stilbene analogues, which strongly supports the existence of different isomerization pathways between azobenzene and stilbene. The graphene oxide catalyzed isomerization is expected to be useful as a new photoisomerization based sensing platform complementary to GO-based fluorescence quenching methods.

  6. The mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol

    Institute of Scientific and Technical Information of China (English)

    竹湘锋; 徐新华

    2004-01-01

    Fe (Ⅲ)-catalyzed ozonation yielded better degradation rate and extent of COD (Chemical Oxygen Demand) or oxalic acid as compared with oxidation by ozone alone. Two parameters with strong effects on the efficiency of ozonation are pH of the solution and the catalyst (Fe3+) dosage. The existence of a critical pH value determining the catalysis of Fe (Ⅲ) in acid conditions was observed in phenol and oxalic acid systems. The best efficiency of catalysis was obtained at a moderate concentration of the catalyst. A reasonable mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol was obtained based on the results and literature.

  7. New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qinhua [Iowa State Univ., Ames, IA (United States)

    2004-12-19

    The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I2, ICl, PhSeCl, PhSCl and p-O2NC6H4SCl to give the corresponding halogen-, selenium- and sulfur-containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. This methodology accommodates a variety of iminoalkynes and affords the anticipated heterocycles in moderate to excellent yields. The Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes provides an efficient way to synthesize a variety of 4-(1-alkenyl)-3-arylisoquinolines in moderate to excellent yields. The introduction of an ortho-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Highly substituted naphthalenes have been synthesized by the palladium-catalyzed annulation of a variety of internal alkynes, in which two new carbon-carbon bonds are formed in a single step under relatively mild reaction conditions. This method has also been used to synthesize carbazoles, although a higher reaction temperature is necessary. The process involves arylpalladation of the alkyne, followed by intramolecular Heck olefination and double bond isomerization. This method accommodates a variety of functional groups and affords the anticipated highly substituted naphthalenes and carbazoles in good to excellent yields. Novel palladium migratiodarylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement

  8. New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

    Energy Technology Data Exchange (ETDEWEB)

    Qinhua Huang

    2004-12-19

    The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I{sub 2}, ICl, PhSeCl, PhSCl and p-O{sub 2}NC{sub 6}H{sub 4}SCl to give the corresponding halogen-, selenium- and sulfur-containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. This methodology accommodates a variety of iminoalkynes and affords the anticipated heterocycles in moderate to excellent yields. The Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes provides an efficient way to synthesize a variety of 4-(1-alkenyl)-3-arylisoquinolines in moderate to excellent yields. The introduction of an ortho-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Highly substituted naphthalenes have been synthesized by the palladium-catalyzed annulation of a variety of internal alkynes, in which two new carbon-carbon bonds are formed in a single step under relatively mild reaction conditions. This method has also been used to synthesize carbazoles, although a higher reaction temperature is necessary. The process involves arylpalladation of the alkyne, followed by intramolecular Heck olefination and double bond isomerization. This method accommodates a variety of functional groups and affords the anticipated highly substituted naphthalenes and carbazoles in good to excellent yields. Novel palladium migratiodarylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement with the idea that

  9. Recent advances in copper-catalyzed asymmetric coupling reactions

    Directory of Open Access Journals (Sweden)

    Fengtao Zhou

    2015-12-01

    Full Text Available Copper-catalyzed (or -mediated asymmetric coupling reactions have received significant attention over the past few years. Especially the coupling reactions of aryl or alkyl halides with nucleophiles became a very powerful tool for the formation of C–C, C–N, C–O and other carbon–heteroatom bonds as well as for the construction of heteroatom-containing ring systems. This review summarizes the recent progress in copper-catalyzed asymmetric coupling reactions for the formation of C–C and carbon–heteroatom bonds.

  10. Esterification of phenolic acids catalyzed by lipases immobilized in organogels.

    Science.gov (United States)

    Zoumpanioti, M; Merianou, E; Karandreas, T; Stamatis, H; Xenakis, A

    2010-10-01

    Lipases from Rhizomucor miehei and Candida antarctica B were immobilized in hydroxypropylmethyl cellulose organogels based on surfactant-free microemulsions consisting of n-hexane, 1-propanol and water. Both lipases kept their catalytic activity, catalyzing the esterification reactions of various phenolic acids including cinnamic acid derivatives. High reaction rates and yields (up to 94%) were obtained when lipase from C. antarctica was used. Kinetic studies have been performed and apparent kinetic constants were determined showing that ester synthesis catalyzed by immobilized lipases occurs via the Michaelis-Menten mechanism.

  11. Rh-Catalyzed Asymmetric Hydrogenation of 1,2-Dicyanoalkenes.

    Science.gov (United States)

    Li, Meina; Kong, Duanyang; Zi, Guofu; Hou, Guohua

    2017-01-06

    A highly efficient enantioselective hydrogenation of 1,2-dicyanoalkenes catalyzed by the complex of rhodium and f-spiroPhos has been developed. A series of 1,2-dicyanoalkenes were successfully hydrogenated to the corresponding chiral 1,2-dicyanoalkanes under mild conditions with excellent enantioselectivities (up to 98% ee). This methodology provides efficient access to the asymmetric synthesis of chiral diamines.

  12. DNA strand exchange catalyzed by molecular crowding in PEG solutions

    KAUST Repository

    Feng, Bobo

    2010-01-01

    DNA strand exchange is catalyzed by molecular crowding and hydrophobic interactions in concentrated aqueous solutions of polyethylene glycol, a discovery of relevance for understanding the function of recombination enzymes and with potential applications to DNA nanotechnology. © 2010 The Royal Society of Chemistry.

  13. Rh-Catalyzed arylation of fluorinated ketones with arylboronic acids.

    Science.gov (United States)

    Dobson, Luca S; Pattison, Graham

    2016-09-25

    The Rh-catalyzed arylation of fluorinated ketones with boronic acids is reported. This efficient process allows access to fluorinated alcohols in high yields under mild conditions. Competition experiments suggest that difluoromethyl ketones are more reactive than trifluoromethyl ketones in this process, despite their decreased electronic activation, an effect we postulate to be steric in origin.

  14. ASYMMETRIC HYDROSILYLATION CATALYZED BY POLYMER—SUPPORTED THIAZOLIDINE RHODIUM CATALYSTS

    Institute of Scientific and Technical Information of China (English)

    LEIYanohui; LIHong; 等

    1999-01-01

    Asymmetric hydrisilylation catalyzed by polymeric thiazolidine rhodium catalysts was conducted.Almost the same optical yields have been obtained when comb-shaped polymeric ligands and their corresponding monomer complexed rhodium cataltysts were used to asymmetric hydrosilylation of acetophenone.Optical yield of chiral 1-methylbenzyl alcohol reaches as high as 71.5%.Temperature dependence of enantioselective hydrosilylation of acetophenone was discussed.

  15. Gal3 Catalyzed Tetrahydropyranylation of Alcohols and Phenols

    Institute of Scientific and Technical Information of China (English)

    SUN, Pei-Pei(孙培培); HU, Zhi-Xin(胡志新)

    2004-01-01

    In dichloromethane, the nucleophilic addition of alcohols or phenols to 3,4-dihydro-2H-pyran (DHP) was catalyzed effectively by gallium triiodide which was generated in situ by the reaction of gallium metal and iodine to give the corresponding tetrahydropyranyl acetals in good to excellent yields.

  16. Iron-Catalyzed Synthesis of Sulfur-Containing Heterocycles.

    Science.gov (United States)

    Bosset, Cyril; Lefebvre, Gauthier; Angibaud, Patrick; Stansfield, Ian; Meerpoel, Lieven; Berthelot, Didier; Guérinot, Amandine; Cossy, Janine

    2016-10-13

    An iron-catalyzed synthesis of sulfur- and sulfone-containing heterocycles is reported. The method is based on the cyclization of readily available substrates and proceeded with high efficiency and diastereoselectivity. A variety of sulfur-containing heterocycles bearing moieties suitable for subsequent functionalization are prepared. Illustrative examples of such postcyclization modifications are also presented.

  17. Catalyzing new product adoption at the base of the pyramid

    NARCIS (Netherlands)

    Marinakis, Y.D.; Walsh, S.T.; Harms, R.

    2016-01-01

    One of the more perplexing of the entrepreneurial issues at the Base of the Pyramid (BoP) is how to catalyze new product adoption by BoP consumers. Because S-shaped adoption dynamics are the result of cultural transmission bias, the question can be rephrased as, how can an entrepreneur overcome conf

  18. Kinetic Resolution of Aryl Alkenylcarbinols Catalyzed by Fc-PIP

    Institute of Scientific and Technical Information of China (English)

    胡斌; 孟萌; 姜山山; 邓卫平

    2012-01-01

    An effective kinetic resolution of a variety of aryl alkenylcarbinols catalyzed by nonenzymatic acyl transfer catalyst Fe-PIP was developed, affording corresponding unreacted alcohols in good to excellent ee value up to 99% and with selectivity factors up to 24.

  19. Recent developments in gold-catalyzed cycloaddition reactions

    Directory of Open Access Journals (Sweden)

    Fernando López

    2011-08-01

    Full Text Available In the last years there have been extraordinary advances in the development of gold-catalyzed cycloaddition processes. In this review we will summarize some of the most remarkable examples, and present the mechanistic rational underlying the transformations.

  20. Palladium-Catalyzed alpha-Arylation of Tetramic Acids

    DEFF Research Database (Denmark)

    Storgaard, Morten; Dorwald, F. Z.; Peschke, B.;

    2009-01-01

    A mild, racemization-free, palladium-Catalyzed alpha-arylation of tetramic acids (2,4-pyrrolidinediones) has been developed. Various amino acid-derived tetramic acids were cleanly arylated by treatment with 2 mol % of Pd(OAc)(2), 4 mol % of a sterically demanding biaryl phosphine, 2.3 equiv of K2CO...

  1. Asymmetric Catalytic Reactions Catalyzed by Chiral Titanium Complexes

    Institute of Scientific and Technical Information of China (English)

    FENG XiaoMing

    2001-01-01

    @@ Chiral titanium complexes is very importance catalyst to asymmetric catalytic reactions. A series of catalytic systems based on titanium-chiral ligands complexes has been reported. This presentation will discuss some of our recent progress on asymmetric catalytic reactions catalyzed by chiral titanium complexes.

  2. Asymmetric Catalytic Reactions Catalyzed by Chiral Titanium Complexes

    Institute of Scientific and Technical Information of China (English)

    FENG; XiaoMing

    2001-01-01

    Chiral titanium complexes is very importance catalyst to asymmetric catalytic reactions. A series of catalytic systems based on titanium-chiral ligands complexes has been reported. This presentation will discuss some of our recent progress on asymmetric catalytic reactions catalyzed by chiral titanium complexes.  ……

  3. Transfer Methane to Fragrant Hydrocarbon by Direct Catalyzed Dehydrogenation

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Sponsored by NSFC,a research project -"Transfer methane to fragrant hydrocarbon by direct catalyzed dehydrogenation",directed by Prof.Xin Bao from Dalian Institute of Chemical Physics of CAS,honored the 2nd class National Science & Technology Award in 2005.

  4. Solvent-free lipase-catalyzed preparation of diacylglycerols.

    Science.gov (United States)

    Weber, Nikolaus; Mukherjee, Kumar D

    2004-08-25

    Various methods have been applied for the enzymatic preparation of diacylglycerols that are used as dietary oils for weight reduction in obesity and related disorders. Interesterification of rapeseed oil triacylglycerols with commercial preparations of monoacylglycerols, such as Monomuls 90-O18, Mulgaprime 90, and Nutrisoft 55, catalyzed by immobilized lipase from Rhizomucor miehei (Lipozyme RM IM) in vacuo at 60 degrees C led to extensive (from 60 to 75%) formation of diacylglycerols. Esterification of rapeseed oil fatty acids with Nutrisoft, catalyzed by Lipozyme RM in vacuo at 60 degrees C, also led to extensive (from 60 to 70%) formation of diacylglycerols. Esterification of rapeseed oil fatty acids with glycerol in vacuo at 60 degrees C, catalyzed by Lipozyme RM and lipases from Thermomyces lanuginosus (Lipozyme TL IM) and Candida antarctica (lipase B, Novozym 435), also provided diacylglycerols, however, to a lower extent (40-45%). Glycerolysis of rapeseed oil triacylglycerols with glycerol in vacuo at 60 degrees C, catalyzed by Lipozyme TL and Novozym 435, led to diacylglycerols to the extent of

  5. Polyphosphorous acid catalyzed cyclization in the synthesis of cryptolepine derivatives

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline7-carboxylic acid was obtained specifically by polyphosphorous acid catalyzed cyclization with optimal reaction conditions. Biological assays showed that it potentially inhibits the proteasomal chymotrypsin-like activity in vitro and suppresses breast cancer cell growth.

  6. Phosphine-catalyzed [3+2] annulation of cyanoallenes

    NARCIS (Netherlands)

    Kinderman, S.S.; van Maarseveen, J.H.; Hiemstra, H.

    2011-01-01

    Cyanoallenes were successfully used in organophosphine-catalyzed [3+2]-type annulation to give cyano-substituted dihydropyrroles in good yield. Chiral phosphines were also screened, leading to some initial results in the asymmetric version of cyano­allene-based annulations.

  7. ReBr(CO)5-Catalyzed Knoevenagel Condensation

    Institute of Scientific and Technical Information of China (English)

    ZUO Wei-xiong; HUA Rui-mao; SUN Hong-bin

    2004-01-01

    Knoevenagel condensations are especially important reactions for the synthesis of alkene compounds having electron-withdrawing groups such as COR,CN,COOR,NO2 etc. Recently,transition metal hydride ruthenium1, hydride and polyhydride rhenium2, and polyhydride iridium complexes have been found to be the efficient catalysts for Knoevenagle condensation. However the mentioned-above transition metal hydride complexes are not easily prepared. In addition, all of them are oxygen and H2O-sensitive, unstable compands. Therefor the catalytic reactions are required to be carried out under an inert atmosphere, and using the prepurified reagent.In the paper, We wish to report the development of Knoevenagel condensation catalyzed by ReBr(CO)5 under an air atmosphere in the absence of solvent.All the experiments were carried out under 1atm, without solvent.The resuIts of the representative Knoevenagel condensations are summarized in Table 1.The Knoevenagel reaction with diethyl malonate can be catalyzed by ReBr(CO)5, while the present Knoevenagel reactions catalyzed by transition metal have at least one cyano group in active methylene compouds.A propose mechanism for present catalytic coupling dehydration reactions is also illustrated in the paper.Briefly, this paper reports the ReBr(CO)5-catalyzed Knoevenagel reaction. The reaction is a new method for the Konevenagel condensation.

  8. Enantioselective N-heterocyclic carbene-catalyzed synthesis of trifluoromethyldihydropyridinones.

    Science.gov (United States)

    Wang, Dong-Ling; Liang, Zhi-Qin; Chen, Kun-Quan; Sun, De-Qun; Ye, Song

    2015-06-05

    The enantioselective N-heterocyclic carbene-catalyzed [4 + 2] cyclocondensation of α-chloroaldehydes and trifluoromethyl N-Boc azadienes was developed, giving the corresponding 3,4-disubstituted-6-trifluoromethyldihydropyridin-2(1H)-ones in good yields with exclusive cis-selectivities and excellent enantioselectivities.

  9. Computational Studies on Cinchona Alkaloid-Catalyzed Asymmetric Organic Reactions.

    Science.gov (United States)

    Tanriver, Gamze; Dedeoglu, Burcu; Catak, Saron; Aviyente, Viktorya

    2016-06-21

    Remarkable progress in the area of asymmetric organocatalysis has been achieved in the last decades. Cinchona alkaloids and their derivatives have emerged as powerful organocatalysts owing to their reactivities leading to high enantioselectivities. The widespread usage of cinchona alkaloids has been attributed to their nontoxicity, ease of use, stability, cost effectiveness, recyclability, and practical utilization in industry. The presence of tunable functional groups enables cinchona alkaloids to catalyze a broad range of reactions. Excellent experimental studies have extensively contributed to this field, and highly selective reactions were catalyzed by cinchona alkaloids and their derivatives. Computational modeling has helped elucidate the mechanistic aspects of cinchona alkaloid catalyzed reactions as well as the origins of the selectivity they induce. These studies have complemented experimental work for the design of more efficient catalysts. This Account presents recent computational studies on cinchona alkaloid catalyzed organic reactions and the theoretical rationalizations behind their effectiveness and ability to induce selectivity. Valuable efforts to investigate the mechanisms of reactions catalyzed by cinchona alkaloids and the key aspects of the catalytic activity of cinchona alkaloids in reactions ranging from pharmaceutical to industrial applications are summarized. Quantum mechanics, particularly density functional theory (DFT), and molecular mechanics, including ONIOM, were used to rationalize experimental findings by providing mechanistic insights into reaction mechanisms. B3LYP with modest basis sets has been used in most of the studies; nonetheless, the energetics have been corrected with higher basis sets as well as functionals parametrized to include dispersion M05-2X, M06-2X, and M06-L and functionals with dispersion corrections. Since cinchona alkaloids catalyze reactions by forming complexes with substrates via hydrogen bonds and long

  10. Mechanism of horseradish peroxidase-catalyzed heme oxidation and polymerization (beta-hematin formation).

    Science.gov (United States)

    Trivedi, Vishal; Chand, Prem; Maulik, Prakas R; Bandyopadhyay, Uday

    2005-05-25

    Horseradish peroxidase (HRP) catalyzes the polymerization of free heme (beta-hematin formation) through its oxidation. Heme when added to HRP compound II (FeIV=O) causes spectral shift from 417 nm (Compound II) to 402 nm (native, FeIII) indicating that heme may be oxidized via one-electron transfer. Direct evidence for one-electron oxidation of heme by HRP intermediates is provided by the appearance of an E.s.r signal of a 5,5-dimethyl-1-pyrroline N-oxide (spin trap)-heme radical adduct (a1H=14.75 G, a2H=4.0 G) in E.s.r studies. Heme-polymerization by HRP is inhibited by spin trap indicating that one-electron oxidation product of heme ultimately leads to the formation of heme-polymer. HRP, when incubated with diethyl pyrocarbonate (DEPC), a histidine specific reagent, shows concentration dependent loss of heme-polymerization indicating the role of histidine residues in the process. We suggest that HRP catalyzes the formation of heme-polymer through one-electron oxidation of free heme.

  11. Microcalorimetric Study on Tyrosine Oxidation Catalyzed by Tyrosinase

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Through the method of initial heat release rate, the kinetic property of tyrosine oxidationcatalyzed by tyrosinase from Pseudomonas maltophilia was investigated using a LKB-2107 batchmicrocalorimeter. Tyrosine was catalyzed and oxidized into L-dopa, then into melanin catalyzed bytyrosinase. We found that the tyrosinase reaction obeyed the Michaelis-Menten kinetics, and at298.15K and pH 7.0, the initial exothermic rate (Ω0) are in the range of0.1567~0.5704 mJ@ s-1, themaximum exothermic rate (Ωmax) are in 0.4152 ~ 0.8143mol @ L-1, and mean value of the Michaelisconstant (Km) is 2.199±0.105×104 mol @ L-1.

  12. Silylation of Dinitrogen Catalyzed by Hydridodinitrogentris(TriphenylphosphineCobalt(I

    Directory of Open Access Journals (Sweden)

    Wojciech I. Dzik

    2016-07-01

    Full Text Available Recently, homogeneous cobalt systems were reported to catalyze the reductive silylation of dinitrogen. In this study the investigations on the silylation of dinitrogen catalyzed by CoH(PPh33N2 are presented. We show that in the presence of the title compound, the reaction of N2 with trimethylsilylchloride and sodium yields, on average, 6.7 equivalents of tris(trimethylsilylamine per Co atom in THF (tetrahydrofuran. The aim was to elucidate whether the active catalyst is: (a the [Co(PPh33N2]− anion formed after two-electron reduction of the title compound; or (b a species formed via decomposition of CoH(PPh33N2 in the presence of the highly reactive substrates. Time profile, and IR and EPR spectroscopic investigations show instability of the pre-catalyst under the applied conditions which suggests that the catalytically active species is formed through in situ modification of the pre-catalyst.

  13. Thermodynamics of Enzyme-Catalyzed Reactions. Part 3. Hydrolases

    Science.gov (United States)

    Goldberg, Robert N.; Tewari, Yadu B.

    1994-11-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by the hydrolase class of enzymes have been compiled. For each reaction the following information is given: The reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement [temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used]; the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it or any calculations for which the data have been used. The data from 145 references have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  14. Thermodynamics of Enzyme-Catalyzed Reactions: Part 4. Lyases

    Science.gov (United States)

    Goldberg, Robert N.; Tewari, Yadu B.

    1995-09-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by the lyase class of enzymes have been compiled. For each reaction the following information is given: the reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement (temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used); the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it or any calculations for which the data have been used. The data from 106 references have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  15. Thermodynamics of Enzyme-Catalyzed Reactions: Part 2. Transferases

    Science.gov (United States)

    Goldberg, Robert N.; Tewari, Yadu B.

    1994-07-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by the transferase class of enzymes have been compiled. For each reaction the following information is given: the reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement [temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used]; the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it or any calculations for which the data have been used. The data from 285 references have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  16. Mechanism of Intramolecular Rhodium- and Palladium-Catalyzed Alkene Alkoxyfunctionalizations

    KAUST Repository

    Vummaleti, Sai V. C.

    2015-11-13

    Density functional theory calculations have been used to investigate the reaction mechanism for the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-bis(diphenylphosphino)propane) and [Pd]/BPh3 dual catalytic system assisted intramolecular alkoxycyanation ([Pd] = Pd-Xantphos) using acylated and cyanated 2-allylphenol derivatives as substrates, respectively. Our results substantially confirm the proposed mechanism for both [Rh]- and [Pd]/ BPh3-mediated alkoxyfunctionalizations, offering a detailed geometrical and energetical understanding of all the elementary steps. Furthermore, for the [Rh]-mediated alkoxyacylation, our observations support the hypothesis that the quinoline group of the substrate is crucial to stabilize the acyl metal complex and prevent further decarbonylation. For [Pd]/BPh3-catalyzed alkoxycyanation, our findings clarify how the Lewis acid BPh3 cocatalyst accelerates the only slow step of the reaction, corresponding to the oxidative addition of the cyanate O-CN bond to the Pd center. © 2015 American Chemical Society.

  17. Polymerization of phenols catalyzed by peroxidase in nonaqueous media

    Energy Technology Data Exchange (ETDEWEB)

    Dordick, J.S.; Marletta, M.A.; Klibanov, A.M.

    1987-01-01

    Polymers produced by horseradish-peroxidase-catalyzed coupling of phenols have been explored as potential substitutes for phenol-formaldehyde resins. To overcome low substrate solubilities and product molecular weights in water, enzymatic polymerizations in aqueous-organic mixtures have been examined. Peroxidase vigorously polymerizes a number of phenols in mixtures of water with water-miscible solvents such as dioxane, acetone, dimethylformamide, and methyl formate with the solvent content up to 95%. As a result, various phenolic polymers with average molecular weights from 400 to 2.6 x 10/sup 4/ D were obtained depending on the reaction medium composition and the nature of the phenol. Peroxidase-catalyzed copolymerization of different phenols in 85% dioxane was demonstrated. Poly(p-phenylphenol) and poly(p-cresol) were enzymatically prepared on a gram scale. They had much higher melting points, and in addition, poly(p-phenylphenol) was found to have a much higher electrical conductivity than phenol-formaldehyde resins.

  18. Effect of urate on the lactoperoxidase catalyzed oxidation of adrenaline.

    Science.gov (United States)

    Løvstad, Rolf A

    2004-12-01

    Lactoperoxidase is an iron containing enzyme, which is an essential component of the defense system of mammalian secretary fluids. The enzyme readily oxidizes adrenaline and other catecholamines to coloured aminochrome products. A Km-value of 1.21 mM and a catalytic constant (k = Vmax/[Enz]) of 15.5 x 10(3) min(-1) characterized the reaction between lactoperoxidase and adrenaline at pH 7.4. Urate was found to activate the enzyme catalyzed oxidation of adrenaline in a competitive manner, the effect decreasing with increasing adrenaline concentration. Lactoperoxidase was able to catalyze the oxidation of urate. However, urate was a much poorer substrate than adrenaline, and it seems unlikely that urate activates by functioning as a free, redox cycling intermediate between enzyme and adrenaline. The activation mechanism probably involves an urate-lactoperoxidase complex.

  19. Synthesis of heterocycles through transition-metal-catalyzed isomerization reactions.

    Science.gov (United States)

    Ishoey, Mette; Nielsen, Thomas E

    2014-07-14

    Metal-catalyzed isomerization of N- and O-allylic systems is emerging as an effective method to form synthetically useful iminium and oxocarbenium intermediates. In the presence of tethered nucleophiles, several recent examples illuminate this approach as a powerful strategy for the synthesis of structurally complex and diverse heterocycles. In this Concept article, we attempt to cover this area of research through a selection of recent versatile examples.

  20. Silver-Catalyzed C(sp(3))-H Chlorination.

    Science.gov (United States)

    Ozawa, Jun; Kanai, Motomu

    2017-03-17

    A silver-catalyzed chlorination of benzylic, tertiary, and secondary C(sp(3))-H bonds was developed. The reaction proceeded with as low as 0.2 mol % catalyst loading at room temperature under air atmosphere with synthetically useful functional group compatibility. The regioselectivity and reactivity tendencies suggest that the chlorination proceeded through a radical pathway, but an intermediate alkylsilver species cannot be ruled out.

  1. Predictive Modeling of Metal-Catalyzed Polyolefin Processes

    OpenAIRE

    Khare, Neeraj Prasad

    2003-01-01

    This dissertation describes the essential modeling components and techniques for building comprehensive polymer process models for metal-catalyzed polyolefin processes. The significance of this work is that it presents a comprehensive approach to polymer process modeling applied to large-scale commercial processes. Most researchers focus only on polymerization mechanisms and reaction kinetics, and neglect physical properties and phase equilibrium. Both physical properties and phase equilib...

  2. Comparing Ru and Fe-catalyzed olefin metathesis.

    Science.gov (United States)

    Poater, Albert; Chaitanya Vummaleti, Sai Vikrama; Pump, Eva; Cavallo, Luigi

    2014-08-01

    Density functional theory calculations have been used to explore the potential of Fe-based complexes with an N-heterocyclic carbene ligand, as olefin metathesis catalysts. Apart from a less endothermic reaction energy profile, a small reduction in the predicted upper energy barriers (≈ 2 kcal mol(-1)) is calculated in the Fe catalyzed profile with respect to the Ru catalysed profile. Overall, this study indicates that Fe-based catalysts have the potential to be very effective olefin metathesis catalysts.

  3. Biodiesel by acid-catalyzed transesterification with butanol

    OpenAIRE

    Bynes, Adrian

    2012-01-01

    Jatropha oil and Rapeseed oil was transesterified with n-butanol by the use of H2SO4. Before conducting the experiments a review of the effect of alcohol type was preformed. Alcohols from methanol to butanol, branched and straight, were reviewed for the effect on the acid catalyzed transesterification reaction. From the review it was found that propanol and butanol were the best for the acidic transesterification reaction. Variables such as time, temperature, alcohol amount and catalyst c...

  4. Cell-surface acceleration of urokinase-catalyzed receptor cleavage

    DEFF Research Database (Denmark)

    Høyer-Hansen, G; Ploug, M; Behrendt, N;

    1997-01-01

    937 cell lysates, had the same amino termini as uPAR(2+3), generated by uPA in a purified system. In both cases cleavage had occurred at two positions in the hinge region connecting domain 1 and 2, between Arg83-Ala84 and Arg89-Ser90, respectively. The uPA-catalyzed cleavage of uPAR is a new negative...

  5. Synthesis of Optically Active Polystyrene Catalyzed by Monophosphine Pd Complexes.

    Science.gov (United States)

    Jouffroy, Matthieu; Armspach, Dominique; Matt, Dominique; Osakada, Kohtaro; Takeuchi, Daisuke

    2016-07-11

    Cationic Pd(II) monophosphine complexes derived from α- and β-cyclodextrins (CDs) promote the homopolymerization of styrene under carbon monoxide pressure. Although reversible CO coordination takes place under catalytic conditions according to (13) C NMR studies with (13) C-enriched CO, both complexes catalyze the formation of CO-free styrene polymers. These macromolecules display optical activity as a result of the presence of stereoregular sequences within the overall atactic polymer.

  6. Gold-catalyzed oxidative cycloadditions to activate a quinoline framework.

    Science.gov (United States)

    Huple, Deepak B; Ghorpade, Satish; Liu, Rai-Shung

    2013-09-23

    Going for gold! Gold-catalyzed reactions of 3,5- and 3,6-dienynes with 8-alkylquinoline oxides results in an oxidative cycloaddition with high stereospecificity (see scheme; EWG = electron-withdrawing group); this process involves a catalytic activation of a quinoline framework. The reaction mechanism involves the intermediacy of α-carbonyl pyridinium ylides (I) in a concerted [3+2]-cycloaddition with a tethered alkene.

  7. Lactoperoxidase-catalyzed activation of carcinogenic aromatic and heterocyclic amines.

    Science.gov (United States)

    Gorlewska-Roberts, Katarzyna M; Teitel, Candee H; Lay, Jackson O; Roberts, Dean W; Kadlubar, Fred F

    2004-12-01

    Lactoperoxidase, an enzyme secreted from the human mammary gland, plays a host defensive role through antimicrobial activity. It has been implicated in mutagenic and carcinogenic activation in the human mammary gland. The potential role of heterocyclic and aromatic amines in the etiology of breast cancer led us to examination of the lactoperoxidase-catalyzed activation of the most commonly studied arylamine carcinogens: 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP), benzidine, 4-aminobiphenyl (ABP), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). In vitro activation was performed with lactoperoxidase (partially purified from bovine milk or human milk) in the presence of hydrogen peroxide and calf thymus DNA. Products formed during enzymatic activation were monitored by HPLC with ultraviolet and radiometric detection. Two of these products were characterized as hydrazo and azo derivatives by means of mass spectrometry. The DNA binding level of 3H- and 14C-radiolabeled amines after peroxidase-catalyzed activation was dependent on the hydrogen peroxide concentration, and the highest levels of carcinogen binding to DNA were observed at 100 microM H2O2. Carcinogen activation and the level of binding to DNA were in the order of benzidine > ABP > IQ > MeIQx > PhIP. One of the ABP adducts was identified, and the level at which it is formed was estimated to be six adducts/10(5) nucleotides. The susceptibility of aromatic and heterocyclic amines for lactoperoxidase-catalyzed activation and the binding levels of activated products to DNA suggest a potential role of lactoperoxidase-catalyzed activation of carcinogens in the etiology of breast cancer.

  8. Asymmetric Aldol Reaction Catalyzed by Modularly Designed Organocatalysts

    Institute of Scientific and Technical Information of China (English)

    Sinha, Debarshi; Mandal, Tanmay; Gogoi, Sanjib; Goldman, Joshua J.; 赵从贵

    2012-01-01

    The self-assembly of the precatalyst modules, which are amino acids and cinchona alkaloid derivatives, leads to the direct formation of the desired organocatalysts without any synthesis. These modularly designed organocatalysts (MDOs) may be used for catalyzed asymmetric aldol reaction the corresponding aldol products may be obtained in mediocre diastereoselectivities (up to 79 : 21 dr). Depending on structure of the aldehyde substrates, to excellent ee values (up to 92% ee) with moderate

  9. Cobalt-catalyzed formation of symmetrical biaryls and its mechanism.

    Science.gov (United States)

    Moncomble, Aurélien; Le Floch, Pascal; Gosmini, Corinne

    2009-01-01

    Effective devotion: An efficient cobalt-catalyzed method devoted to the formation of symmetrical biaryls is described avoiding the preparation of organometallic reagents. Various aromatic halides functionalized by a variety of reactive group reagents are employed. Preliminary DFT calculations have shown that the involvement of a Co(I)/Co(III) couple is realistic at least in the case of 1,3-diazadienes as ligands (FG = functional group).

  10. Aluminum-catalyzed silicon nanowires: Growth methods, properties, and applications

    Science.gov (United States)

    Hainey, Mel F.; Redwing, Joan M.

    2016-12-01

    Metal-mediated vapor-liquid-solid (VLS) growth is a promising approach for the fabrication of silicon nanowires, although residual metal incorporation into the nanowires during growth can adversely impact electronic properties particularly when metals such as gold and copper are utilized. Aluminum, which acts as a shallow acceptor in silicon, is therefore of significant interest for the growth of p-type silicon nanowires but has presented challenges due to its propensity for oxidation. This paper summarizes the key aspects of aluminum-catalyzed nanowire growth along with wire properties and device results. In the first section, aluminum-catalyzed nanowire growth is discussed with a specific emphasis on methods to mitigate aluminum oxide formation. Next, the influence of growth parameters such as growth temperature, precursor partial pressure, and hydrogen partial pressure on nanowire morphology is discussed, followed by a brief review of the growth of templated and patterned arrays of nanowires. Aluminum incorporation into the nanowires is then discussed in detail, including measurements of the aluminum concentration within wires using atom probe tomography and assessment of electrical properties by four point resistance measurements. Finally, the use of aluminum-catalyzed VLS growth for device fabrication is reviewed including results on single-wire radial p-n junction solar cells and planar solar cells fabricated with nanowire/nanopyramid texturing.

  11. Protection of wood from microorganisms by laccase-catalyzed iodination.

    Science.gov (United States)

    Schubert, M; Engel, J; Thöny-Meyer, L; Schwarze, F W M R; Ihssen, J

    2012-10-01

    In the present work, Norway spruce wood (Picea abies L.) was reacted with a commercial Trametes versicolor laccase in the presence of potassium iodide salt or the phenolic compounds thymol and isoeugenol to impart an antimicrobial property to the wood surface. In order to assess the efficacy of the wood treatment, a leaching of the iodinated and polymerized wood and two biotests including bacteria, a yeast, blue stain fungi, and wood decay fungi were performed. After laccase-catalyzed oxidation of the phenols, the antimicrobial effect was significantly reduced. In contrast, the enzymatic oxidation of iodide (I(-)) to iodine (I(2)) in the presence of wood led to an enhanced resistance of the wood surface against all microorganisms, even after exposure to leaching. The efficiency of the enzymatic wood iodination was comparable to that of a chemical wood preservative, VP 7/260a. The modification of the lignocellulose by the laccase-catalyzed iodination was assessed by the Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique. The intensities of the selected lignin-associated bands and carbohydrate reference bands were analyzed, and the results indicated a structural change in the lignin matrix. The results suggest that the laccase-catalyzed iodination of the wood surface presents an efficient and ecofriendly method for wood protection.

  12. Enzyme-catalyzed biocathode in a photoelectrochemical biofuel cell

    Science.gov (United States)

    Yang, Jing; Hu, Donghua; Zhang, Xiaohuan; Wang, Kunqi; Wang, Bin; Sun, Bo; Qiu, Zhidong

    2014-12-01

    A novel double-enzyme photoelectrochemical biofuel cell (PEBFC) has been developed by taking glucose dehydrogenase (GDH) and horseradish peroxidase (HRP) as the enzyme of the photoanode and biocathode to catalyze the oxidation of glucose and the reduction of oxygen. A H2-mesoporphyrin IX is used as a dye for a TiO2 film electrode to fabricate a photoanode. The horseradish peroxidase (HRP) is immobilized on a glassy carbon (GC) electrode to construct a biocathode which is used to catalyze the reduction of oxygen in the PEBFC for the first time. The biocathode exhibits excellent electrocatalytic activity in the presence of O2. The performances of the PEBFC are obtained by current-voltage and power-voltage curves. The short-circuit current density (Isc), the open-circuit voltage (Voc), maximum power density (Pmax), fill factor (FF) and energy conversion efficiency (η) are 439 μA cm-2, 678 mV, 79 μW cm-2, 0.39 and 0.016%, respectively, and the incident photon-to-collected electron conversion efficiency (IPCE) is 32% at 350 nm. The Isc is higher than that of the PEBFC with Pt cathode, and the Voc is higher than that of the dye-sensitized solar cell or the enzyme-catalyzed biofuel cell operating individually, which demonstrates that the HRP is an efficient catalyst for the biocathode in the PEBFC.

  13. Anisotropic Morphological Changes in Goethite during Fe(2+)-Catalyzed Recrystallization.

    Science.gov (United States)

    Joshi, Prachi; Gorski, Christopher A

    2016-07-19

    When goethite is exposed to aqueous Fe(2+), rapid and extensive Fe atom exchange can occur between solid-phase Fe(3+) and aqueous Fe(2+) in a process referred to as Fe(2+)-catalyzed recrystallization. This process can lead to the structural incorporation or release of trace elements, which has important implications for contaminant remediation and nutrient biogeochemical cycling. Prior work found that the process did not cause major changes to the goethite structure or morphology. Here, we further investigated if and how goethite morphology and aggregation behavior changed temporally during Fe(2+)-catalyzed recrystallization. On the basis of existing literature, we hypothesized that Fe(2+)-catalyzed recrystallization of goethite would not result in changes to individual particle morphology or interparticle interactions. To test this, we reacted nanoparticulate goethite with aqueous Fe(2+) at pH 7.5 over 30 days and used transmission electron microscopy (TEM), cryogenic TEM, and (55)Fe as an isotope tracer to observe changes in particle dimensions, aggregation, and isotopic composition over time. Over the course of 30 days, the goethite particles substantially recrystallized, and the particle dimensions changed anisotropically, resulting in a preferential increase in the mean particle width. The temporal changes in goethite morphology could not be completely explained by a single mineral-transformation mechanism but rather indicated that multiple transformation mechanisms occurred concurrently. Collectively, these results demonstrate that the morphology of goethite nanoparticles does change during recrystallization, which is an important step toward identifying the driving force(s) of recrystallization.

  14. Asymmetric Stetter reactions catalyzed by thiamine diphosphate-dependent enzymes.

    Science.gov (United States)

    Kasparyan, Elena; Richter, Michael; Dresen, Carola; Walter, Lydia S; Fuchs, Georg; Leeper, Finian J; Wacker, Tobias; Andrade, Susana L A; Kolter, Geraldine; Pohl, Martina; Müller, Michael

    2014-12-01

    The intermolecular asymmetric Stetter reaction is an almost unexplored transformation for biocatalysts. Previously reported thiamine diphosphate (ThDP)-dependent PigD from Serratia marcescens is the first enzyme identified to catalyze the Stetter reaction of α,β-unsaturated ketones (Michael acceptor substrates) and α-keto acids. PigD is involved in the biosynthesis of the potent cytotoxic agent prodigiosin. Here, we describe the investigation of two new ThDP-dependent enzymes, SeAAS from Saccharopolyspora erythraea and HapD from Hahella chejuensis. Both show a high degree of homology to the amino acid sequence of PigD (39 and 51 %, respectively). The new enzymes were heterologously overproduced in Escherichia coli, and the yield of soluble protein was enhanced by co-expression of the chaperone genes groEL/ES. SeAAS and HapD catalyze intermolecular Stetter reactions in vitro with high enantioselectivity. The enzymes possess a characteristic substrate range with respect to Michael acceptor substrates. This provides support for a new type of ThDP-dependent enzymatic activity, which is abundant in various species and not restricted to prodigiosin biosynthesis in different strains. Moreover, PigD, SeAAS, and HapD are also able to catalyze asymmetric carbon-carbon bond formation reactions of aldehydes and α-keto acids, resulting in 2-hydroxy ketones.

  15. Reduction of nitrobenzene by the catalyzed Fe/Cu process

    Institute of Scientific and Technical Information of China (English)

    XU Wenying; LI Ping; FAN Jinhong

    2008-01-01

    The polarization behavior of the couple Fe/Cu in 100 mg/L nitrobenzene aqueous solution was studied using Evans coupling diagrams. The results indicated that the iron corrosion was limited by both anodic and cathodic half-cell reactions under the neutral conditions and cathodically controlled under the alkaline conditions. Batch experiments were performed to study the effect of solution pH, reaction duration, concentration, type of electrolyte and dissolved oxygen (DO) on the reduction of nitrobenzene by the catalyzed Fe/Cu process. This process proved effective in the pH range of 3 to 11. The conversion efficiency of nitrobenzene at pH ≈ 10.1 was almost the same as that under highly acid conditions (pH ≈ 3). The degradation of nitrobenzene fell into two phases: adsorption and surface reduction, and the influence of adsorption and mass transfer became more extensive with solution concentration. The reduction rate decreased in the presence of DO in the solution, indicating that a need for aeration was eliminated in the catalyzed Fe/Cu process. Accordingly, spending on energy consumption would be reduced. Economic analysis indicated that merely 0.05 kg was required for the treatment of a ton of nitrobenzene-containing water with pH from 3 to 11. The catalyzed Fe/Cu process is cost-effective and of practical value.

  16. Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

    2011-01-01

    This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

  17. The Acid Hydrolysis Mechanism of Acetals Catalyzed by a Supramolecular Assembly in Basic Solution

    Energy Technology Data Exchange (ETDEWEB)

    Pluth, Michael D.; Bergman, Robert G.; Raymond, Kenneth N.

    2008-09-24

    A self-assembled supramolecular host catalyzes the hydrolysis of acetals in basic aqueous solution. The mechanism of hydrolysis is consistent with the Michaelis-Menten kinetic model. Further investigation of the rate limiting step of the reaction revealed a negative entropy of activation ({Delta}S{double_dagger} = -9 cal mol{sup -1}K{sup -1}) and an inverse solvent isotope effect (k(H{sub 2}O)/k(D{sub 2}O) = 0.62). These data suggest that the mechanism of hydrolysis that takes place inside the assembly proceeds through an A-2 mechanism, in contrast to the A-1 mechanism operating in the uncatalyzed reaction. Comparison of the rates of acetal hydrolysis in the assembly with the rate of the reaction of unencapsulated substrates reveals rate accelerations of up to 980 over the background reaction for the substrate diethoxymethane.

  18. Synthetic Study of Dragmacidin E: Construction of the Core Structure Using Pd-Catalyzed Cascade Cyclization and Rh-Catalyzed Aminoacetoxylation.

    Science.gov (United States)

    Inoue, Naoya; Nakano, Shun-Ichi; Harada, Shingo; Hamada, Yasumasa; Nemoto, Tetsuhiro

    2017-03-03

    We developed a novel synthetic method of the core structure of dragmacidin E bearing a 7-membered ring-fused bis(indolyl)pyrazinone skeleton. Formation of the 7-membered ring-fused tricyclic indole skeleton was accomplished using a palladium-catalyzed Heck insertion-allylic amination cascade. Vicinal difunctionalization of the 7-membered ring was realized via a rhodium-catalyzed aminoacetoxylation.

  19. Development and industrial application of catalyzer for low-temperature hydrogenation hydrolysis of Claus tail gas

    Directory of Open Access Journals (Sweden)

    Honggang Chang

    2015-10-01

    Full Text Available With the implementation of more strict national environmental protection laws, energy conservation, emission reduction and clean production will present higher requirements for sulfur recovery tail gas processing techniques and catalyzers. As for Claus tail gas, conventional hydrogenation catalyzers are gradually being replaced by low-temperature hydrogenation catalyzers. This paper concentrates on the development of technologies for low-temperature hydrogenation hydrolysis catalyzers, preparation of such catalyzers and their industrial application. In view of the specific features of SO2 hydrogenation and organic sulfur hydrolysis during low-temperature hydrogenation, a new technical process involving joint application of hydrogenation catalyzers and hydrolysis catalyzers was proposed. In addition, low-temperature hydrogenation catalyzers and low-temperature hydrolysis catalyzers suitable for low-temperature conditions were developed. Joint application of these two kinds of catalyzers may reduce the inlet temperatures in the conventional hydrogenation reactors from 280 °C to 220 °C, at the same time, hydrogenation conversion rates of SO2 can be enhanced to over 99%. To further accelerate the hydrolysis rate of organic sulfur, the catalyzers for hydrolysis of low-temperature organic sulfur were developed. In lab tests, the volume ratio of the total sulfur content in tail gas can be as low as 131 × 10−6 when these two kinds of catalyzers were used in a proportion of 5:5 in volumes. Industrial application of these catalyzers was implemented in 17 sulfur recovery tail gas processing facilities of 15 companies. As a result, Sinopec Jinling Petrochemical Company had outstanding application performances with a tail gas discharging rate lower than 77.9 mg/m3 and a total sulfur recovery of 99.97%.

  20. Ammonia and hydrazine. Transition-metal-catalyzed hydroamination and metal-free catalyzed functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, Guy [Univ. of California, San Diego, CA (United States)

    2012-06-29

    high temperatures and long reaction times. To address this issue, we have developed several new families of carbon- and boron-based ligands, which are even better donors. The corresponding metal complexes (particularly gold, rhodium, iridium, and ruthenium) of all these species will be tested in the Markovnikov and anti-Markovnikov hydroamination of alkynes, allenes, and also alkenes with ammonia and hydrazine. We will also develop metal-free catalytic processes for the functionalization of ammonia and hydrazine. By possessing both a lone pair of electrons and an accessible vacant orbital, singlet carbenes resemble and can mimic the chemical behavior of transition metals. Our preliminary results demonstrate that specially designed carbenes can split the N–H bond of ammonia by an initial nucleophilic activation that prevents the formation of Lewis acid-base adducts, which is the major hurdle for the transition metal catalyzed functionalization of NH3. The use of purely organic compounds as catalysts will eliminate the major drawbacks of transition-metal-catalysis technology, which are the excessive cost of metal complexes (metal + ligands) and in many cases the toxicity of the metal.

  1. A SABATH Methyltransferase from the moss Physcomitrella patens catalyzes

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Nan [ORNL; Ferrer, Jean-Luc [Universite Joseph Fourier, France; Moon, Hong S [Department of Plant Sciences, University of Tennessee; Kapteyn, Jeremy [Institute of Biological Chemistry, Washington State University; Zhuang, Xiaofeng [Department of Plant Sciences, University of Tennessee; Hasebe, Mitsuyasu [Laboratory of Evolutionary Biology, National Institute for Biology, 38 Nishigounaka; Stewart, Neal C. [Department of Plant Sciences, University of Tennessee; Gang, David R. [Institute of Biological Chemistry, Washington State University; Chen, Feng [University of Tennessee, Knoxville (UTK)

    2012-01-01

    Known SABATH methyltransferases, all of which were identified from seed plants, catalyze methylation of either the carboxyl group of a variety of low molecular weight metabolites or the nitrogen moiety of precursors of caffeine. In this study, the SABATH family from the bryophyte Physcomitrella patens was identified and characterized. Four SABATH-like sequences (PpSABATH1, PpSABATH2, PpSABATH3, and PpSABATH4) were identified from the P. patens genome. Only PpSABATH1 and PpSABATH2 showed expression in the leafy gametophyte of P. patens. Full-length cDNAs of PpSABATH1 and PpSABATH2 were cloned and expressed in soluble form in Escherichia coli. Recombinant PpSABATH1 and PpSABATH2 were tested for methyltransferase activity with a total of 75 compounds. While showing no activity with carboxylic acids or nitrogen-containing compounds, PpSABATH1 displayed methyltransferase activity with a number of thiols. PpSABATH2 did not show activity with any of the compounds tested. Among the thiols analyzed, PpSABATH1 showed the highest level of activity with thiobenzoic acid with an apparent Km value of 95.5 lM, which is comparable to those of known SABATHs. Using thiobenzoic acid as substrate, GC MS analysis indicated that the methylation catalyzed by PpSABATH1 is on the sulfur atom. The mechanism for S-methylation of thiols catalyzed by PpSABATH1 was partially revealed by homology-based structural modeling. The expression of PpSABATH1 was induced by the treatment of thiobenzoic acid. Further transgenic studies showed that tobacco plants overexpressing PpSABATH1 exhibited enhanced tolerance to thiobenzoic acid, suggesting that PpSABATH1 have a role in the detoxification of xenobiotic thiols.

  2. Physio-pathological roles of transglutaminase-catalyzed reactions

    Institute of Scientific and Technical Information of China (English)

    Mariangela; Ricotta; Maura; Iannuzzi; Giulia; De; Vivo; Vittorio; Gentile

    2010-01-01

    Transglutaminases(TGs) are a large family of related and ubiquitous enzymes that catalyze post-translational modifications of proteins.The main activity of these enzymes is the cross-linking of a glutaminyl residue of a protein/peptide substrate to a lysyl residue of a protein/peptide co-substrate.In addition to lysyl residues,other second nucleophilic co-substrates may include monoamines or polyamines(to form mono-or bi-substituted/crosslinked adducts) or-OH groups(to form ester linkages) .In the absence of co-substrates,the nucleophile may be water,resulting in the net deamidation of the glutaminyl residue.The TG enzymes are also capable of catalyzing other reactions important for cell viability.The distribution and the physiological roles of TG enzymes have been widely studied in numerous cell types and tissues and their roles in several diseases have begun to be identified."Tissue" TG(TG2) ,a member of the TG family of enzymes,has definitely been shown to be involved in the molecular mechanisms responsible for a very widespread human pathology:i.e.celiac disease(CD) .TG activity has alsobeen hypothesized to be directly involved in the pathogenetic mechanisms responsible for several other human diseases,including neurodegenerative diseases,which are often associated with CD.Neurodegenerative diseases,such as Alzheimer’s disease,Parkinson’s disease,supranuclear palsy,Huntington’s disease and other recently identified polyglutamine diseases,are characterized,in part,by aberrant cerebral TG activity and by increased cross-linked proteins in affected brains.In this review,we discuss the physio-pathological role of TG-catalyzed reactions,with particular interest in the molecular mechanisms that could involve these enzymes in the physio-pathological processes responsible for human neurodegenerative diseases.

  3. On the Temperature Dependence of Enzyme-Catalyzed Rates.

    Science.gov (United States)

    Arcus, Vickery L; Prentice, Erica J; Hobbs, Joanne K; Mulholland, Adrian J; Van der Kamp, Marc W; Pudney, Christopher R; Parker, Emily J; Schipper, Louis A

    2016-03-29

    One of the critical variables that determine the rate of any reaction is temperature. For biological systems, the effects of temperature are convoluted with myriad (and often opposing) contributions from enzyme catalysis, protein stability, and temperature-dependent regulation, for example. We have coined the phrase "macromolecular rate theory (MMRT)" to describe the temperature dependence of enzyme-catalyzed rates independent of stability or regulatory processes. Central to MMRT is the observation that enzyme-catalyzed reactions occur with significant values of ΔCp(‡) that are in general negative. That is, the heat capacity (Cp) for the enzyme-substrate complex is generally larger than the Cp for the enzyme-transition state complex. Consistent with a classical description of enzyme catalysis, a negative value for ΔCp(‡) is the result of the enzyme binding relatively weakly to the substrate and very tightly to the transition state. This observation of negative ΔCp(‡) has important implications for the temperature dependence of enzyme-catalyzed rates. Here, we lay out the fundamentals of MMRT. We present a number of hypotheses that arise directly from MMRT including a theoretical justification for the large size of enzymes and the basis for their optimum temperatures. We rationalize the behavior of psychrophilic enzymes and describe a "psychrophilic trap" which places limits on the evolution of enzymes in low temperature environments. One of the defining characteristics of biology is catalysis of chemical reactions by enzymes, and enzymes drive much of metabolism. Therefore, we also expect to see characteristics of MMRT at the level of cells, whole organisms, and even ecosystems.

  4. Theoretical Study of the Effects of Di-Muonic Molecules on Muon-Catalyzed Fusion

    Science.gov (United States)

    2012-03-01

    MOLECULES ON MUON -CATALYZED FUSION DISSERTATION Eugene V. Sheely, Lieutenant Colonel, USA DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY...THEORETICAL STUDY OF THE EFFECTS OF DI-MUONIC MOLECULES ON MUON -CATALYZED FUSION DISSERTATION Presented to the Faculty...potential of enhancing the muon -catalyzed fusion reaction rate. In order to study these di-muonic molecules a method of non-adiabatic quantum mechanics

  5. Lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol

    OpenAIRE

    2000-01-01

    The influences of water activity and solvent hydrophobicity on the kinetics of the lipase-catalyzed enantioselective esterification of flurbiprofen with n-butanol were investigated. The solvent effect was not similar for lipases from Candida rugosa (Crl), Mucor javanicus (Mjl), and porcine pancreas (Ppl). The lipase-catalyzed reaction rates in different solvents across a wide range of water activities revealed that the Ppl-catalyzed reaction exhibited no enantioselectivity and no substantial ...

  6. Facile Rh(III)-Catalyzed Synthesis of Fluorinated Pyridines

    Science.gov (United States)

    Chen, Shuming; Bergman, Robert G.; Ellman, Jonathan A.

    2015-01-01

    A Rh(III)-catalyzed C–H functionalization approach was developed for the preparation of multi-substituted 3-fluoropyridines from α-fluoro-α,β-unsaturated oximes and alkynes. Oximes substituted with aryl, heteroaryl and alkyl β-substituents were effective coupling partners, as were symmetrical and unsymmetrical alkynes with aryl and alkyl substituents. The first examples of coupling α,β-unsaturated oximes with terminal alkynes was also demonstrated and proceeded with uniformly high regioselectivity to provide single 3-fluoropyridine regioisomers. Reactions were also conveniently set up in air on the bench top. PMID:25992591

  7. Rhodium catalyzed asymmetric Pauson-Khand reaction using SDP ligands

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The activity and enantiocontrol ability of the chiral catalysts prepared from spiro diphosphine ligands, SDP, and rhodium precursor were investigated in the asymmetric catalytic Pauson-Khand reaction. The results showed that SDP ligands were very effective in Rh-catalyzed Pauson-Khand reaction, and their complexes with rhodium could convert a variety of 1,6-enyne compounds into bicyclopentone derivatives under CO atmosphere in high yields with good enantioselectivities. The SbF6- was found to be a suitable counter anion of the catalyst, and 1,2-dichloroethane was the best choice of the solvent for Pauson-Khand reaction.

  8. Kinetics of acid-catalyzed cleavage of cumene hydroperoxide.

    Science.gov (United States)

    Levin, M E; Gonzales, N O; Zimmerman, L W; Yang, J

    2006-03-17

    The cleavage of cumene hydroperoxide, in the presence of sulfuric acid, to form phenol and acetone has been examined by adiabatic calorimetry. As expected, acid can catalyze cumene hydroperoxide reaction at temperatures below that of thermally-induced decomposition. At elevated acid concentrations, reactivity is also observed at or below room temperature. The exhibited reactivity behavior is complex and is significantly affected by the presence of other species (including the products). Several reaction models have been explored to explain the behavior and these are discussed.

  9. FBH1 Catalyzes Regression of Stalled Replication Forks

    DEFF Research Database (Denmark)

    Fugger, Kasper; Mistrik, Martin; Neelsen, Kai J;

    2015-01-01

    DNA replication fork perturbation is a major challenge to the maintenance of genome integrity. It has been suggested that processing of stalled forks might involve fork regression, in which the fork reverses and the two nascent DNA strands anneal. Here, we show that FBH1 catalyzes regression...... a model whereby FBH1 promotes early checkpoint signaling by remodeling of stalled DNA replication forks....... of a model replication fork in vitro and promotes fork regression in vivo in response to replication perturbation. Cells respond to fork stalling by activating checkpoint responses requiring signaling through stress-activated protein kinases. Importantly, we show that FBH1, through its helicase activity...

  10. Catalyzing new product adoption at the base of the pyramid

    OpenAIRE

    Marinakis, Y.D.; Walsh, S. T.; Harms, R.

    2016-01-01

    One of the more perplexing of the entrepreneurial issues at the Base of the Pyramid (BoP) is how to catalyze new product adoption by BoP consumers. Because S-shaped adoption dynamics are the result of cultural transmission bias, the question can be rephrased as, how can an entrepreneur overcome conformity bias. We modified the Technology Acceptance Model (TAM) to include conformity bias. We then qualitatively applied the model to three examples from the literature, namely fuel stoves in Darfu...

  11. Comparing Ru and Fe-catalyzed olefin metathesis

    KAUST Repository

    Poater, Albert

    2014-01-01

    Density functional theory calculations have been used to explore the potential of Fe-based complexes with an N-heterocyclic carbene ligand, as olefin metathesis catalysts. Apart from a less endothermic reaction energy profile, a small reduction in the predicted upper energy barriers (≈ 2 kcal mol -1) is calculated in the Fe catalyzed profile with respect to the Ru catalysed profile. Overall, this study indicates that Fe-based catalysts have the potential to be very effective olefin metathesis catalysts. This journal is © the Partner Organisations 2014.

  12. Synthesis of Dihydrobenzofurans via Palladium-Catalyzed Heteroannulations

    Energy Technology Data Exchange (ETDEWEB)

    Rozhkov, Roman Vladimirovich [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    Palladium-catalyzed heteroannulation of 1,3-dienes with 3-iodo-2-alkenols, and 2-iodo-2-alkenols, as well as their amino analogs, affords the corresponding cyclic ethers and amines respectively. The presence of a β-hydrogen in the vinylic halide results in β-hydride elimination giving the corresponding alkyne. The presence of a bulky group in the α-position of the vinylic halide results in failure or reduced amounts of annulation products. A chloride source, pyridine base and electron-rich phosphine are essential for this reaction.

  13. Lipase-catalyzed synthesis of monoacylglycerol in a homogeneous system.

    Science.gov (United States)

    Monteiro, Julieta B; Nascimento, Maria G; Ninow, Jorge L

    2003-04-01

    The 1,3-regiospecifique lipase, Lipozyme IM, catalyzed the esterification of lauric acid and glycerol in a homogeneous system. To overcome the drawback of the insolubility of glycerol in hexane, which is extensively used in enzymatic synthesis, a mixture of n-hexane/tert-butanol (1:1, v/v) was used leading to a monophasic system. The conversion of lauric acid into monolaurin was 65% in 8 h, when a molar ratio of glycerol to fatty acid (5:1) was used with the fatty acid at 0.1 M, and the phenomenon of acyl migration was minimized.

  14. Urea- and Thiourea-Catalyzed Aminolysis of Carbonates.

    Science.gov (United States)

    Blain, Marine; Yau, Honman; Jean-Gérard, Ludivine; Auvergne, Rémi; Benazet, Dominique; Schreiner, Peter R; Caillol, Sylvain; Andrioletti, Bruno

    2016-08-23

    The aminolysis of (poly)carbonates by (poly)amines provides access to non-isocyanate polyurethanes (NIPUs) that are toxic-reagent-free analogues of polyurethanes (PUs). Owing to their low reactivity, the ring opening of cyclic carbonates requires the use of a catalyst. Herein, we report that the more available and cheaper ureas could advantageously be used for catalyzing the formation of NIPUs at the expense of the thiourea analogues. In addition, we demonstrate a medium-range pKa of the (thio)urea and an unqeual substitution pattern is critical for controlling the efficiency of the carbonate opening.

  15. Iodine - catalyzed prins cyclization of aliphatic and aromatic ketones

    Energy Technology Data Exchange (ETDEWEB)

    Kishore, K.R.; Reddy, K.; Silva Junior, Luiz F., E-mail: luizfsjr@iq.usp.br [Universidade de Sao Paulo (IQ/USP), SP (Brazil). Inst. de Quimica. Dept. de Quimica Fundamental

    2013-09-15

    Iodine-catalyzed Prins cyclization of homoallylic alcohols and ketones was investigated. Anhydrous conditions and inert atmosphere are not required in this metal-free protocol. The reaction of 2-(3,4-dihydronaphthalene-1-yl)propan-1-ol with six aliphatic symmetric ketones gave the desired products in 67-77% yield. Cyclization was performed with four aliphatic unsymmetric ketones, leading to corresponding pyrans in 66-76% yield. Prins cyclization was also accomplished with four aromatic ketones in 37-66% yield. Finally, Prins cyclization of the monoterpene isopulegol and acetone was successfully achieved. (author)

  16. Production of Chemoenzymatic Catalyzed Monoepoxide Biolubricant: Optimization and Physicochemical Characteristics

    OpenAIRE

    Jumat Salimon; Nadia Salih; Bashar Mudhaffar Abdullah

    2012-01-01

    Linoleic acid (LA) is converted to per-carboxylic acid catalyzed by an immobilized lipase from Candida antarctica (Novozym 435). This per-carboxylic acid is only intermediate and epoxidized itself in good yields and almost without consecutive reactions. Monoepoxide linoleic acid 9(12)-10(13)-monoepoxy 12(9)-octadecanoic acid (MEOA) was optimized using D-optimal design. At optimum conditions, higher yield% (82.14) and medium oxirane oxygen content (OOC) (4.91%) of MEOA were predicted at 15 μL ...

  17. Synthesis of Dihydrobenzofurans via Palladium-Catalyzed Heteroannulations

    Energy Technology Data Exchange (ETDEWEB)

    Roman Vladimirovich Rozhkov

    2004-12-19

    Palladium-catalyzed heteroannulation of 1,3-dienes with 3-iodo-2-alkenols, and 2-iodo-2-alkenols, as well as their amino analogs, affords the corresponding cyclic ethers and amines respectively. The presence of a {beta}-hydrogen in the vinylic halide results in {beta}-hydride elimination giving the corresponding alkyne. The presence of a bulky group in the {alpha}-position of the vinylic halide results in failure or reduced amounts of annulation products. A chloride source, pyridine base and electron-rich phosphine are essential for this reaction.

  18. Triphenylphosphine-Catalyzed Michael Addition of Alcohols to Acrylic Compounds

    Institute of Scientific and Technical Information of China (English)

    LIU, Hai-Ling; JIANG, Huan-Feng; WANG, Yu-Gang

    2007-01-01

    A facile triphenylphosphine-catalyzed Michael addition of alcohols to acrylic compounds was described. The reaction was carried out in open air at refluxing temperature in the presence of 10 mol% PPh3. Michael addition of saturated and unsaturated alcohols to acrylonitrile or acrylates has been examined. The reaction gaveβ-alkoxy derivatives with isolated yields of 5%-79%. PPh3 is cheaper and more stable than those trialkylphosphines previously used for the similar reactions, and the products can be easily separated from the reaction mixture via distillation.

  19. Deoxyribonucleoside kinases: two enzyme families catalyze the same reaction

    DEFF Research Database (Denmark)

    Sandrini, Michael; Piskur, Jure

    2005-01-01

    Mammals have four deoxyribonucleoside kinases, the cytoplasmic (TK1) and mitochondrial (TK2) thymidine kinases, and the deoxycytidine (dCK) and deoxyguanosine (dGK) kinases, which salvage the precursors for nucleic acids synthesis. In addition to the native deoxyribonucleoside substrates, the kin......, the kinases can phosphorylate and thereby activate a variety of anti-cancer and antiviral prodrugs. Recently, the crystal structure of human TK1 has been solved and has revealed that enzymes with fundamentally different origins and folds catalyze similar, crucial cellular reactions....

  20. Study of microwave effects on the lipase-catalyzed hydrolysis.

    Science.gov (United States)

    Chen, Chia-Chen; Reddy, P Muralidhar; Devi, C Shobha; Chang, Po-Chi; Ho, Yen-Peng

    2016-01-01

    The effect of microwave heating on lipase-catalyzed reaction remains controversial. It is not clear whether the reaction rate enhancements are purely due to thermal/heating effects or to non-thermal effects. Therefore, quantitative mass spectrometry was used to conduct accurate kinetic analysis of lipase-catalyzed hydrolysis of triolein by microwave and conventional heating. Commercial lipases from Candida rugosa (CRL), Porcine Pancreas (PPL), and Burkholderia cepacia (BCL) were used. Hydrolysis reactions were performed at various temperatures and pH levels, along with various amounts of buffer and enzymes. Hydrolysis product yields at each time point using an internal-standard method showed no significant difference between microwave and conventional heating conditions when the reaction was carried out at the same temperature. CRL showed optimum catalytic activity at 37 °C, while PPL and BCL had better activities at 50 °C. The phosphate buffer was found to give a better hydrolysis yield than the Tris-HCl buffer. Overall results prove that a non-thermal effect does not exist in microwave-assisted lipase hydrolysis of triolein. Therefore, conventional heating at high temperatures (e.g., 50 °C) can be also used to accelerate hydrolysis reactions.

  1. Acid base catalyzed transesterification kinetics of waste cooking oil

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Siddharth; Sharma, M.P.; Rajvanshi, Shalini [Alternate Hydro Energy Centre, Indian Institute of Technology, Roorkee (India)

    2011-01-15

    The present study reports the results of kinetics study of acid base catalyzed two step transesterification process of waste cooking oil, carried out at pre-determined optimum temperature of 65 C and 50 C for esterification and transesterification process respectively under the optimum condition of methanol to oil ratio of 3:7 (v/v), catalyst concentration 1%(w/w) for H{sub 2}SO{sub 4} and NaOH and 400 rpm of stirring. The optimum temperature was determined based on the yield of ME at different temperature. Simply, the optimum concentration of H{sub 2}SO{sub 4} and NaOH was determined with respect to ME Yield. The results indicated that both esterification and transesterification reaction are of first order rate reaction with reaction rate constant of 0.0031 min{sup -1} and 0.0078 min{sup -1} respectively showing that the former is a slower process than the later. The maximum yield of 21.50% of ME during esterification and 90.6% from transesterification of pretreated WCO has been obtained. This is the first study of its kind which deals with simplified kinetics of two step acid-base catalyzed transesterification process carried under the above optimum conditions and took about 6 h for complete conversion of TG to ME with least amount of activation energy. Also various parameters related to experiments are optimized with respect to ME yield. (author)

  2. Metalloporphyrin solubility: a trigger for catalyzing reductive dechlorination of tetrachloroethylene.

    Science.gov (United States)

    Dror, Ishai; Schlautman, Mark A

    2004-02-01

    Metalloporphyrins are well known for their electron-transfer roles in many natural redox systems. In addition, several metalloporphyrins and related tetrapyrrole macrocycles complexed with various core metals have been shown to catalyze the reductive dechlorination of certain organic compounds, thus demonstrating the potential for using naturally occurring metalloporphyrins to attenuate toxic and persistent chlorinated organic pollutants in the environment. However, despite the great interest in reductive dechlorination reactions and the wide variety of natural and synthetic porphyrins currently available, only soluble porphyrins, which comprise a small fraction of this particular family of organic macrocycles, have been used as electron-transfer shuttles in these reactions. Results from the present study clearly demonstrate that metalloporphyrin solubility is a key factor in their ability to catalyze the reductive dechlorination of tetrachloroethylene and its daughter compounds. Additionally, we show that certain insoluble and nonreactive metalloporphyrins can be activated as catalysts merely by changing solution conditions to bring about their dissolution. Furthermore, once a metalloporphyrin is fully dissolved and activated, tetrachloroethylene transformation proceeds rapidly, giving nonchlorinated and less toxic alkenes as the major reaction products. Results from the present study suggest that if the right environmental conditions exist or can be created, specific metalloporphyrins may provide a solution for cleaning up sites that are contaminated with chlorinated organic pollutants.

  3. Enzyme catalyzed electricity-driven water softening system.

    Science.gov (United States)

    Arugula, Mary A; Brastad, Kristen S; Minteer, Shelley D; He, Zhen

    2012-12-10

    Hardness in water, which is caused by divalent cations such as calcium and magnesium ions, presents a major water quality problem. Because hard water must be softened before use in residential applications, there is great interest in the saltless water softening process because, unlike ion exchange softeners, it does not introduce additional ions into water. In this study, a saltless hardness removal driven by bioelectrochemical energy produced through enzymatic oxidation of glucose was proposed and investigated. Glucose dehydrogenase was coated on a carbon electrode to catalyze glucose oxidation in the presence of NAD⁺ as a cofactor/mediator and methylene green as an electrocatalyst. The results showed that electricity generation stimulated hardness removal compared with non-electricity conditions. The enzymatic water softener worked upon a 6h batch operation per day for eight days, and achieved an average hardness removal of 46% at a high initial concentration of 800 mg/L as CaCO₃. More hardness was removed at a lower initial concentration. For instance, at 200mg/L as CaCO₃ the enzymatic water softener removed 76.4±4.6% of total hardness. The presence of magnesium ions decreased hardness removal because of its larger hydrated radius than calcium ions. The enzymatic water softener removed 70-80% of total hardness from three actual hard water samples. These results demonstrated a proof-of-concept that enzyme catalyzed electricity generation can be used to soften hard water.

  4. Ozonation of Indigo Carmine Catalyzed with Fe-Pillared Clay

    Directory of Open Access Journals (Sweden)

    Miriam Bernal

    2013-01-01

    Full Text Available The ozonation catalyzed by iron-pillared clays was studied. The degradation of dye indigo carmine (IC was elected as test reaction. Fe-pillared clays were synthesized by employing hydrolyzed FeCl3 solutions and bentonite. The pillared structure was verified by XRD and by XPS the oxidation state of iron in the synthesized material was established to be +2. By atomic absorption the weight percentage of iron was determined to be 16. The reaction was conducted in a laboratory scale up-flow bubble column reactor. From the studied variables the best results were obtained with a particle size of 60 microns, pH=3, ozone flow of 0.045 L/min, and catalyst concentration of 100 mg/L. IC was completely degraded and degradation rate was found to be double when using Fe-PILCS than with ozone alone. DQO reduction was also significantly higher with catalyzed than with noncatalyzed ozonation.

  5. Thermodynamics of Enzyme-Catalyzed Reactions: Part 1. Oxidoreductases

    Science.gov (United States)

    Goldberg, Robert N.; Tewari, Yadu B.; Bell, Donna; Fazio, Kari; Anderson, Ellen

    1993-03-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by oxidoreductases have been compiled. For each reaction the following information is given: the reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement (temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used); the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it. The thermodynamic conventions pertinent to the tabulation of equilibrium data are discussed. A distinction is made between those thermodynamic quantities which pertain to the overall biochemical reaction and those which pertain to a reference reaction that involves specific species. The data from 205 references have been examined and evaluated. Chemical Abstract Service Registry Numbers have been assigned to the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participated.

  6. IRC analysis of methanol carbonylation reaction catalyzed by rhodium complex

    Institute of Scientific and Technical Information of China (English)

    HAO Maorong; FENG Wenlin; JI Yongqiang; LEI Ming

    2004-01-01

    In the reaction cycle for methanol carbonylation catalyzed by Rh complex, the structure geometries of the reactant, intermediates, transition states and product of each elemental reaction have been studied by using the energy gradient method at HF/LANL2DZ level, and the changes of their potential profiles have also been calculated. Through IRC analyses of the transition states for each elemental reaction, it is confirmed that the various structure geometries obtained are stationary points on the cycle reaction pathway of methanol carbonylation catalyzed by Rh complex, and the changes are given in energies and structure geometries of the reactant molecules along the reaction pathway of lowest energy. It has been proposed that the geometrical conversions of intermediates play an important role during the cycle reaction. Through analyses of structure geometries, it has been suggested that, in addition to cis- and trans- structure exchange linkage of catalysis reactive species, the two pathways, cis- and trans-cata- lyzed cycle reactions, can also be linked through geometrical conversion of intermediates, of which the activation energy is 49.79 kJ/mol. Moreover, the reductive elimination elemental reaction may be neither cis-cycle nor trans- one, showing that the cycle reaction can be achieved through various pathways. However different the pathway, the oxidative addition elemental reaction of CH3I is the rate-controlling step.

  7. Lipase-catalyzed polyester synthesis – A green polymer chemistry

    Science.gov (United States)

    Kobayashi, Shiro

    2010-01-01

    This article is a short comprehensive review describing in vitro polyester synthesis catalyzed by a hydrolysis enzyme of lipase, most of which has been developed for these two decades. Polyesters are prepared by repeated ester bond-formation reactions; they include two major modes, ring-opening polymerization (ROP) of cyclic monomers such as cyclic esters (lactones) and condensation polymerization via the reaction between a carboxylic acid or its ester group and an alcohol group. Polyester synthesis is, therefore, a reaction in reverse way of in vivo lipase catalysis of ester bond-cleavage with hydrolysis. The lipase-catalyzed polymerizations show very high chemo-, regio-, and enantio-selectivities and involve various advantageous characteristics. Lipase is robust and compatible with other chemical catalysts, which allows novel chemo-enzymatic processes. New syntheses of a variety of functional polyesters and a plausible reaction mechanism of lipase catalysis are mentioned. The polymerization characteristics are of green nature currently demanded for sustainable society, and hence, desirable for conducting ‘green polymer chemistry’. PMID:20431260

  8. Lipase-catalyzed polyester synthesis--a green polymer chemistry.

    Science.gov (United States)

    Kobayashi, Shiro

    2010-01-01

    This article is a short comprehensive review describing in vitro polyester synthesis catalyzed by a hydrolysis enzyme of lipase, most of which has been developed for these two decades. Polyesters are prepared by repeated ester bond-formation reactions; they include two major modes, ring-opening polymerization (ROP) of cyclic monomers such as cyclic esters (lactones) and condensation polymerization via the reaction between a carboxylic acid or its ester group and an alcohol group. Polyester synthesis is, therefore, a reaction in reverse way of in vivo lipase catalysis of ester bond-cleavage with hydrolysis. The lipase-catalyzed polymerizations show very high chemo-, regio-, and enantio-selectivities and involve various advantageous characteristics. Lipase is robust and compatible with other chemical catalysts, which allows novel chemoenzymatic processes. New syntheses of a variety of functional polyesters and a plausible reaction mechanism of lipase catalysis are mentioned. The polymerization characteristics are of green nature currently demanded for sustainable society, and hence, desirable for conducting 'green polymer chemistry'.

  9. Solution-solid-solid mechanism: superionic conductors catalyze nanowire growth.

    Science.gov (United States)

    Wang, Junli; Chen, Kangmin; Gong, Ming; Xu, Bin; Yang, Qing

    2013-09-11

    The catalytic mechanism offers an efficient tool to produce crystalline semiconductor nanowires, in which the choice, state, and structure of catalysts are active research issues of much interest. Here we report a novel solution-solid-solid (SSS) mechanism for nanowire growth catalyzed by solid-phase superionic conductor nanocrystals in low-temperature solution. The preparation of Ag2Se-catalyzed ZnSe nanowires at 100-210 °C is exampled to elucidate the SSS model, which can be extendable to grow other II-VI semiconductor (e.g., CdSe, ZnS, and CdS) nanowires by the catalysis of nanoscale superionic-phase silver or copper(I) chalcogenides (Ag2Se, Ag2S, and Cu2S). The exceptional catalytic ability of these superionic conductors originates from their structure characteristics, known for high-density vacancies and fast mobility of silver or copper(I) cations in the rigid sublattice of Se(2-) or S(2-) ions. Insights into the SSS mechanism are provided based on the formation of solid solution and the solid-state ion diffusion/transport at solid-solid interface between catalyst and nanowire.

  10. Drosophila melanogaster CYP6A8, an insect P450 that catalyzes lauric acid (omega-1)-hydroxylation.

    Science.gov (United States)

    Helvig, Christian; Tijet, Nathalie; Feyereisen, René; Walker, F Ann; Restifo, Linda L

    2004-12-24

    Only a handful of P450 genes have been functionally characterized from the approximately 90 recently identified in the genome of Drosophila melanogaster. Cyp6a8 encodes a 506-amino acid protein with 53.6% amino acid identity with CYP6A2. CYP6A2 has been shown to catalyze the metabolism of several insecticides including aldrin and heptachlor. CYP6A8 is expressed at many developmental stages as well as in adult life. CYP6A8 was produced in Saccharomyces cerevisiae and enzymatically characterized after catalytic activity was reconstituted with D. melanogaster P450 reductase and NADPH. Although several saturated or non-saturated fatty acids were not metabolized by CYP6A8, lauric acid (C12:0), a short-chain unsaturated fatty acid, was oxidized by CYP6A8 to produce 11-hydroxylauric acid with an apparent V(max) of 25 nmol/min/nmol P450. This is the first report showing that a member of the CYP6 family catalyzes the hydroxylation of lauric acid. Our data open new prospects for the CYP6 P450 enzymes, which could be involved in important physiological functions through fatty acid metabolism.

  11. Immobilization of Chiral Ferrocenyl Ligands on Silica Gel and their Testing in Pd-catalyzed Allylic Substitution and Rh-catalyzed Hydrogenation

    Directory of Open Access Journals (Sweden)

    Duncan J. Macquarrie

    2005-07-01

    Full Text Available Five different silica gels containing two chiral ferrocenyl ligands were prepared by various synthetic routes and tested in an enantioselective Pd(0-catalyzed allylic substitution and Rh-catalyzed hydrogenation. All the prepared anchored ligands were characterized by porosimetry data, DRIFTS spectra, thermal data and AAS. The aim of the work was to compare the influence of the carrier, surface properties and immobilization strategy on the performance of the catalyst.

  12. ROLE OF COPPER,ZINC-SUPEROXIDE DISMUTASE IN CATALYZING NITROTYROSINE FORMATION IN MURINE LIVER

    Science.gov (United States)

    The solely known function of Cu,Zn-superoxide dismutase (SOD1) is to catalyze the dismutation of superoxide anion into hydrogen peroxide. Our objective was to determine if SOD1 catalyzed murine liver protein nitration induced by acetaminophen (APAP) and lipopolysaccharide (LPS). Liver and plasma ...

  13. LIPASE-CATALYZED TRANSESTERIFICATION OF PALM KERNEL OIL WITH DIALKYLCARBONATES

    Directory of Open Access Journals (Sweden)

    Tjahjono Herawan

    2014-01-01

    Full Text Available Lipase-catalyzed transesterifications-especially in a solvent-free medium-are important for industrial applications because such systems would have an enormous advantage by avoiding the problem of separation, toxicity and flammability of organic solvents. However, the organic solvent-free alcoholysis, especially methanolysis, does not give high conversions. The same problem also occurs when ethyl or methyl acetate are used as acyl acceptors. The main problems of lipase-catalyzed organic solvent-free alcoholysis are first, the solubility of the plant oil in the substrate or solvent and second, the fact that transesterification is an equilibrium reaction. Dialkyl carbonates, versatile compounds due to their chemical reactivity and physical properties, may provide an alternative to solve both problems. Using dialkyl carbonates transesterification is not an equilibrium reaction, because the intermediate compound immediately decomposes to carbon dioxide and an alcohol. Moreover, dialkyl carbonates (especially dimethyl carbonate are cheap and widely available. For single step lipase-catalyzed transesterification of palm kernel oil, diakyl carbonates (in this case dimethyl and diethyl carbonate gave better yields compared to those of short chain alcohols. The rate of ester formation with dialkyl carbonates as substrate was about 6-7 times higher than that obtained with short chain alcohols. The formation of esters was gradually increased by a higher enzyme amount from 5-20% (w/w of oil for 8 h reaction time. However from the economic point of view, an enzyme amount of 10% on the weight base of oil was proposed for further reaction. Generally, the highest ester formation was observed when a temperature of 60°C was used. However, in the case of dimethyl carbonate little difference was observed at reaction temperatures of 60 and 70oC and the reactions proceeded nearly identically. The esters formation increased drastically up to more than 70% when water

  14. Degradation and transformation of atrazine under catalyzed ozonation process with TiO2 as catalyst.

    Science.gov (United States)

    Yang, Yixin; Cao, Hongbin; Peng, Pai; Bo, Hongmiao

    2014-08-30

    Degradation of atrazine by heterogeneously catalyzed ozonation was carried out with TiO2 in the form of rutile as the catalyst. Some experimental factors such as catalyst dose, ozone dose and initial concentration of atrazine were investigated for their influence on catalyzed ozonation process. Although atrazine was effectively removed from aqueous solution by catalyzed ozonation process, the mineralization degree only reached 56% at the experimental conditions. Five transformation products were identified by GC/MS analysis. The degradation of atrazine involved de-alkylation, de-chlorination and de-amination. Diaminotriazine and 5-azauracil were the de-chlorinated and de-aminated products, respectively. The evolution of concentration of transformation products during catalyzed ozonation process was compared with uncatalyzed ozonation to show the degradation pathway. Toxicity tests based on the inhibition of the luminescence emitted by Vibrio fisheri indicated the detoxification of atrazine by catalyzed ozonation.

  15. Rh(II)-catalyzed Reactions of Diazoesters with Organozinc Reagents

    Science.gov (United States)

    Panish, Robert; Selvaraj, Ramajeyam; Fox, Joseph M.

    2015-01-01

    Rh(II)-catalyzed reactions of diazoesters with organozinc reagents are described. Diorganozinc reagents participate in reactions with diazo compounds by two distinct, catalyst-dependent mechanisms. With bulky diisopropylethylacetate ligands, the reaction mechanism is proposed to involve initial formation of a Rh-carbene and subsequent carbozincation to give a zinc enolate. With Rh2(OAc)4, it is proposed that initial formation of an azine precedes 1,2-addition by an organozinc reagent. This straightforward route to the hydrazone products provides a useful method for preparing chiral quaternary α-aminoesters or pyrazoles via the Paul-Knorr condensation with 1,3-diketones. Crossover and deuterium labeling experiments provide evidence for the mechanisms proposed. PMID:26241081

  16. Muon Catalyzed Fusion in 3 K Solid Deuterium

    CERN Document Server

    Knowles, P E; Bailey, J M; Beer, G A; Beveridge, J L; Fujiwara, M C; Huber, T M; Jacot-Guillarmod, R; Kammel, P; Kim, S K; Kunselman, A R; Marshall, G M; Martoff, C J; Mason, G R; Mulhauser, F; Olin, A; Petitjean, C; Porcelli, T A; Zmeskal, J; Zmeskal, and J.

    1997-01-01

    Muon catalyzed fusion in deuterium has traditionally been studied in gaseous and liquid targets. The TRIUMF solid-hydrogen-layer target system has been used to study the fusion reaction rates in the solid phase of D_2 at a target temperature of 3 K. Products of two distinct branches of the reaction were observed; neutrons by a liquid organic scintillator, and protons by a silicon detector located inside the target system. The effective molecular formation rate from the upper hyperfine state of $\\mu d$ and the hyperfine transition rate have been measured: $\\tilde{\\lambda}_(3/2)=2.71(7)_{stat.}(32)_{syst.} The molecular formation rate is consistent with other recent measurements, but not with the theory for isolated molecules. The discrepancy may be due to incomplete thermalization, an effect which was investigated by Monte Carlo calculations. Information on branching ratio parameters for the s and p wave d+d nuclear interaction has been extracted.

  17. Chemical and genomic evolution of enzyme-catalyzed reaction networks.

    Science.gov (United States)

    Kanehisa, Minoru

    2013-09-02

    There is a tendency that a unit of enzyme genes in an operon-like structure in the prokaryotic genome encodes enzymes that catalyze a series of consecutive reactions in a metabolic pathway. Our recent analysis shows that this and other genomic units correspond to chemical units reflecting chemical logic of organic reactions. From all known metabolic pathways in the KEGG database we identified chemical units, called reaction modules, as the conserved sequences of chemical structure transformation patterns of small molecules. The extracted patterns suggest co-evolution of genomic units and chemical units. While the core of the metabolic network may have evolved with mechanisms involving individual enzymes and reactions, its extension may have been driven by modular units of enzymes and reactions.

  18. Lactam hydrolysis catalyzed by mononuclear metallo-ß-bactamases

    DEFF Research Database (Denmark)

    Olsen, Lars; Antony, J; Ryde, U

    2003-01-01

    . For most studied systems, the tetrahedral structure is a stable intermediate. Moreover, the C-N bond in the lactam ring is intact in this intermediate, as well as in the following transition state-its cleavage is induced by proton transfer to the nitrogen atom in the lactam ring. However, for the model...... with Asp as a proton shuttle, attack of the zinc-bond hydroxide ion seems to be concerted with the proton transfer. We have also studied the effect of replacing one of the histidine ligands by an asparagine or glutamine residue, giving a zinc site representative of other subclasses of metallo......Two central steps in the hydrolysis of lactam antibiotics catalyzed by mononuclear metallo-beta-lactamases, formation of the tetrahedral intermediate and its breakdown by proton transfer, are studied for model systems using the density functional B3LYP method. Metallo-beta-lactamases have two metal...

  19. Mg-catalyzed autoclave synthesis of aligned silicon carbide nanostructures.

    Science.gov (United States)

    Xi, Guangcheng; Liu, Yankuan; Liu, Xiaoyan; Wang, Xiaoqing; Qian, Yitai

    2006-07-27

    In this article, a novel magnesium-catalyzed co-reduction route was developed for the large-scale synthesis of aligned beta-SiC one-dimensional (1D) nanostructures at relative lower temperature (600 degrees C). By carefully controlling the reagent concentrations, we could synthesize beta-SiC rodlike and needlelike nanostructures. The possible growth mechanism of the as-synthesized beta-SiC 1D nanostructures has been investigated. The structure and morphology of the as-synthesized beta-SiC nanostructures are characterized using X-ray diffraction, Fourier transform infrared absorption, and scanning and transmission electron microscopes. Raman and photoluminescence properties are also investigated at room temperature. The as-synthesized beta-SiC nanostructures exhibit strong shape-dependent field emission properties. Corresponding to their shapes, the as-synthesized nanorods and nanoneedles display the turn-on fields of 12, 8.4, and 1.8 V/microm, respectively.

  20. Silica nanospheres formation induced by peroxidase-catalyzed phenol polymerization

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    To examine whether lignin-like compound is correlated with silica precipitation in grass, a series of simulated chemical experiments were carried out at ambient temperature and pressure, close to cell wall pH, with phenol polymerization catalyzed by peroxidase in silicon solution. The experiments showed that phenol polymer (a kind of lignin-like substance) caused silica nanosphere precipitation similar to those caused by protein in diatom cell wall previously reported by other authors. The sphere diameter varied with different kinds of phenol and the concentrations of phenol and silicon. Silicon precipitation had phenol and silicon saturation effect, meaning that when the concentration ratio of soluble silicon to phenol exceeded a certain value, the amount of silicon precipitation would decrease.

  1. Synthesis of Rosin Acid Starch Catalyzed by Lipase

    Directory of Open Access Journals (Sweden)

    Rihui Lin

    2014-01-01

    Full Text Available Rosin, an abundant raw material from pine trees, was used as a starting material directly for the synthesis of rosin acid starch. The esterification reaction was catalyzed by lipase (Novozym 435 under mild conditions. Based on single factor experimentation, the optimal esterification conditions were obtained as follows: rosin acid/anhydrous glucose unit in the molar ratio 2 : 1, reaction time 4 h at 45°C, and 15% of lipase dosage. The degree of substitution (DS reaches 0.098. Product from esterification of cassava starch with rosin acid was confirmed by FTIR spectroscopy and iodine coloration analysis. Scanning electron microscopy and X-ray diffraction analysis showed that the morphology and crystallinity of the cassava starch were largely destroyed. Thermogravimetric analysis indicated that thermal stability of rosin acid starch decreased compared with native starch.

  2. CRYSTAL DEFECTS IN PLASMA NITRIDED LAYER CATALYZED BY RARE EARTH

    Institute of Scientific and Technical Information of China (English)

    F.S. Chen; Y.X. Liu; D.K. Liang; L.M. Xiao

    2002-01-01

    The microstructure of plasma nitrided layer catalyzed by rare-earth elements has beenstudied with TEM. The results show that the grains of γ'-Fe4N phase are refinedby rare-earth elements and the plane defects in boundary are increased by rare-earthelements. The addition of rare-earth element increases the bombardment effect andthe number of crystal defects such as vacancies, dislocation loops, twins and stackingfaults in γ'-Fe4N phase and can produce the high-density dislocations in the ferrite ofdiffusion layer at a distance 0. 08mm from the surface. The production of a numberof crystal defects is one of important reasons why rare-earth element accelerates thediffusion of nitrogen atoms during plasma-nitridiug.

  3. FBH1 Catalyzes Regression of Stalled Replication Forks

    Directory of Open Access Journals (Sweden)

    Kasper Fugger

    2015-03-01

    Full Text Available DNA replication fork perturbation is a major challenge to the maintenance of genome integrity. It has been suggested that processing of stalled forks might involve fork regression, in which the fork reverses and the two nascent DNA strands anneal. Here, we show that FBH1 catalyzes regression of a model replication fork in vitro and promotes fork regression in vivo in response to replication perturbation. Cells respond to fork stalling by activating checkpoint responses requiring signaling through stress-activated protein kinases. Importantly, we show that FBH1, through its helicase activity, is required for early phosphorylation of ATM substrates such as CHK2 and CtIP as well as hyperphosphorylation of RPA. These phosphorylations occur prior to apparent DNA double-strand break formation. Furthermore, FBH1-dependent signaling promotes checkpoint control and preserves genome integrity. We propose a model whereby FBH1 promotes early checkpoint signaling by remodeling of stalled DNA replication forks.

  4. Recent developments in lipase-catalyzed synthesis of polyesters.

    Science.gov (United States)

    Kobayashi, Shiro

    2009-02-18

    Polyester synthesis by lipase catalyst involves two major polymerization modes: i) ring-opening polymerization of lactones, and, ii) polycondensation. Ring-opening polymerization includes the finding of lipase catalyst; scope of reactions; polymerization mechanism; ring-opening polymerization reactivity of lactones; enantio-, chemo- and regio-selective polymerizations; and, chemoenzymatic polymerizations. Polycondensation includes polymerizations involving condensation reactions between carboxylic acid and alcohol functional groups to form an ester bond. In most cases, a carboxylic acid group is activated as an ester form, such as a vinyl ester. Many recently developed polymerizations demonstrate lipase catalysis specific to enzymatic polymerization and appear very useful. Also, since lipase-catalyzed polyester synthesis provides a good opportunity for conducting "green polymer chemistry", the importance of this is described.

  5. Cobalt catalyzed hydroesterification of a wide range of olefins

    Energy Technology Data Exchange (ETDEWEB)

    Van Rensburg, H.; Hanton, M.; Tooze, R.P.; Foster, D.F. [Sasol Technology UK, St Andrews (United Kingdom)

    2011-07-01

    Petrochemical raw materials are an essential raw material for the production of detergents with a substantial portion of synthetic fatty alcohols being produced via hydroformylation of oil or coal derived olefins. Carbonylation processes other than hydroformylation have to date not been commercially employed for the production of fatty esters or alcohols. In this document we highlight the opportunities of converting olefins to esters using cobalt catalyzed alkoxycarbonylation. This process is highly versatile and applicable to a wide range of olefins, linear or branched, alpha or internal in combination with virtually any chain length primary or secondary alcohol allowing the synthesis of a diverse array of compounds such as ester ethoxylated surfactants, methyl branched detergents, lubricants and alkyl propanoates. Furthermore, alkoxycarbonylation of a broad olefin/paraffin hydrocarbon range could be used to produce the corresponding broad cut detergent alcohols. (orig.)

  6. WILDCAT: a catalyzed D-D tokamak reactor

    Energy Technology Data Exchange (ETDEWEB)

    Evans, K. Jr.; Baker, C.C.; Brooks, J.N.

    1981-11-01

    WILDCAT is a conceptual design of a catalyzed D-D, tokamak, commercial, fusion reactor. WILDCAT utilizes the beneficial features of no tritium breeding, while not extrapolating unnecessarily from existing D-T designs. The reactor is larger and has higher magnetic fields and plasma pressures than typical D-T devices. It is more costly, but eliminates problems associated with tritium breeding and has tritium inventories and throughputs approximately two orders of magnitude less than typical D-T reactors. There are both a steady-state version with Alfven-wave current drive and a pulsed version. Extensive comparison with D-T devices has been made, and cost and safety analyses have been included. All of the major reactor systems have been worked out to a level of detail appropriate to a complete, conceptual design.

  7. The general base in the thymidylate synthase catalyzed proton abstraction.

    Science.gov (United States)

    Ghosh, Ananda K; Islam, Zahidul; Krueger, Jonathan; Abeysinghe, Thelma; Kohen, Amnon

    2015-12-14

    The enzyme thymidylate synthase (TSase), an important chemotherapeutic drug target, catalyzes the formation of 2'-deoxythymidine-5'-monophosphate (dTMP), a precursor of one of the DNA building blocks. TSase catalyzes a multi-step mechanism that includes the abstraction of a proton from the C5 of the substrate 2'-deoxyuridine-5'-monophosphate (dUMP). Previous studies on ecTSase proposed that an active-site residue, Y94 serves the role of the general base abstracting this proton. However, since Y94 is neither very basic, nor connected to basic residues, nor located close enough to the pyrimidine proton to be abstracted, the actual identity of this base remains enigmatic. Based on crystal structures, an alternative hypothesis is that the nearest potential proton-acceptor of C5 of dUMP is a water molecule that is part of a hydrogen bond (H-bond) network comprised of several water molecules and several protein residues including H147, E58, N177, and Y94. Here, we examine the role of the residue Y94 in the proton abstraction step by removing its hydroxyl group (Y94F mutant). We investigated the effect of the mutation on the temperature dependence of intrinsic kinetic isotope effects (KIEs) and found that these KIEs are more temperature dependent than those of the wild-type enzyme (WT). These results suggest that the phenolic -OH of Y94 is a component of the transition state for the proton abstraction step. The findings further support the hypothesis that no single functional group is the general base, but a network of bases and hydroxyls (from water molecules and tyrosine) sharing H-bonds across the active site can serve the role of the general base to remove the pyrimidine proton.

  8. Purification and deodorization of structured lipids by short path distillation

    DEFF Research Database (Denmark)

    Xu, Xuebing; Jacobsen, Charlotte; Nielsen, Nina Skall;

    2002-01-01

    Purification of structured lipids (SL), produced from lipase- catalyzed acidolysis of rapeseed oil and capric acid, and deodorization of randomized SL, produced from chemical randomization of fish oil and tricaprin, were studied in a bench-scale short path distillation (SPD). SL obtained from...

  9. Differential inhibition of CYP1-catalyzed regioselective hydroxylation of estradiol by berberine and its oxidative metabolites.

    Science.gov (United States)

    Chang, Yu-Ping; Huang, Chiung-Chiao; Shen, Chien-Chang; Tsai, Keng-Chang; Ueng, Yune-Fang

    2015-10-01

    Berberine is a pharmacologically active alkaloid present in widely used medicinal plants, such as Coptis chinensis (Huang-Lian). The hormone estradiol is oxidized by cytochrome P450 (CYP) 1B1 to primarily form the genotoxic metabolite 4-hydroxyestradiol, whereas CYP1A1 and CYP1A2 predominantly generate 2-hydroxyestradiol. To illustrate the effect of berberine on the regioselective oxidation of estradiol, effects of berberine and its metabolites on CYP1 activities were studied. Among CYP1s, CYP1B1.1, 1.3 (L432V), and 1.4 (N453S)-catalyzed 4-hydroxylation were preferentially inhibited by berberine. Differing from the competitive inhibition of CYP1B1.1 and 1.3, N453S substitution in CYP1B1 allowed a non-competitive or mixed-type pattern. An N228T in CYP1B1 highly decreased its activity and preference to 4-hydroxylation. A reverse mutation of T223N in CYP1A2 retained its 2-hydroxylation preference, but enhanced its inhibition susceptibility to berberine. Compared with berberine, metabolites demethyleneberberine and thalifendine caused weaker inhibition of CYP1A1 and CYP1B1 activities. Unexpectedly, thalifendine was more potent than berberine in the inhibition of CYP1A2, in which case an enhanced interaction through polar hydrogen-π bond was predicted from the docking analysis. These results demonstrate that berberine preferentially inhibits the estradiol 4-hydroxylation activity of CYP1B1 variants, suggesting that 4-hydroxyestradiol-mediated toxicity might be reduced by berberine, especially in tissues/tumors highly expressing CYP1B1.

  10. Recent advances in osmium-catalyzed hydrogenation and dehydrogenation reactions.

    Science.gov (United States)

    Chelucci, Giorgio; Baldino, Salvatore; Baratta, Walter

    2015-02-17

    CONSPECTUS: A current issue in metal-catalyzed reactions is the search for highly efficient transition-metal complexes affording high productivity and selectivity in a variety of processes. Moreover, there is also a great interest in multitasking catalysts that are able to efficiently promote different organic transformations by careful switching of the reaction parameters, such as temperature, solvent, and cocatalyst. In this context, osmium complexes have shown the ability to catalyze efficiently different types of reactions involving hydrogen, proving at the same time high thermal stability and simple synthesis. In the catalytic reduction of C═X (X = O, N) bonds by both hydrogenation (HY) and transfer hydrogenation (TH) reactions, the most interest has been focused on homogeneous systems based on rhodium, iridium, and in particular ruthenium catalysts, which have proved to catalyze chemo- and stereoselective hydrogenations with remarkable efficiency. By contrast, osmium catalysts have received much less attention because they are considered less active on account of their slower ligand exchange kinetics. Thus, this area remained almost neglected until recent studies refuted these prejudices. The aim of this Account is to highlight the impressive developments achieved over the past few years by our and other groups on the design of new classes of osmium complexes and their applications in homogeneous catalytic reactions involving the hydrogenation of carbon-oxygen and carbon-nitrogen bonds by both HY and TH reactions as well as in alcohol deydrogenation (DHY) reactions. The work described in this Account demonstrates that osmium complexes are emerging as powerful catalysts for asymmetric and non-asymmetric syntheses, showing a remarkably high catalytic activity in HY and TH reactions of ketones, aldehydes, imines, and esters as well in DHY reactions of alcohols. Thus, for instance, the introduction of ligands with an NH function, possibly in combination with a

  11. High power density yeast catalyzed microbial fuel cells

    Science.gov (United States)

    Ganguli, Rahul

    Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density

  12. Isotopic study of ceria-catalyzed soot oxidation in the presence of NOx

    OpenAIRE

    Guillén Hurtado, Noelia; García García, Avelina; Bueno López, Agustín

    2013-01-01

    The ceria-catalyzed soot oxidation mechanism has been studied by a pulse technique with labeled O2 in the absence and presence of NO, using ceria–soot mixtures prepared in the loose contact mode. In the absence of soot, the ceria-catalyzed oxidation of NO to NO2 takes place with ceria oxygen and not with gas-phase O2. However, the oxygen exchange process between gas-phase O2 and ceria oxygen (to yield back O2, but with oxygen atoms coming from ceria) prevailed with regard to the ceria-catalyz...

  13. DFT Study of the Molybdenum-Catalyzed Deoxydehydration of Vicinal Diols

    DEFF Research Database (Denmark)

    Lupp, Daniel; Christensen, Niels Johan; Dethlefsen, Johannes Rytter

    2015-01-01

    The mechanism of the molybdenum-catalyzed deoxydehydration (DODH) of vicinal diols has been investigated using density functional theory. The proposed catalytic cycle involves condensation of the diol with an MoVI oxo complex, oxidative cleavage of the diol resulting in an MoIV complex......, and extrusion of the alkene. We have compared the proposed pathway with several alternatives, and the results have been corroborated by comparison with the molybdenum- catalyzed sulfoxide reduction recently published by Sanz et al. and with experimental observations for the DODH itself. Improved understanding...... of the mechanism should expedite future optimization of molybdenum-catalyzed biomass transformations....

  14. Exploring chain length selectivity in HIC-catalyzed polycondensation reactions.

    Science.gov (United States)

    Feder, David; Gross, Richard A

    2010-03-08

    Polyester synthesis activity of immobilized Humicola insolens (HiC) was systematically studied with three-series of substrates varying in (i) omega-hydroxyalkanoic acid (omegaHA), (ii) alpha,omega-n-alkane diol, and (iii) alpha,omega-n-alkane diacid chain length. Covalent immobilization of HiC on Amberzyme oxirane (AO) resin (i.e., AO-HiC) was prepared. HiC-AO's activity for omegaHA substrates with 6, 10, 12, and 16 carbons was C16 > C12, where C10-omegaHA and C6-omegaHA were not polymerized. In contrast, N435's activity for omegaHA substrates was C16 = C12 > C10, where C6-omegaHA was not polymerized. HiC-AO activity for copolymerization of sebacic acid (C10-diacid) with alpha,omega-n-alkane diols with 3-, 4-, 5-, 6-, and 8-carbon chain lengths was C8 > C6, where C3, C4, and C5 diols were not polymerized. N435's relative activity for diol substrates was C8 = C6 = C5 > C4 > C3. HiC-AO activity for copolymerizations of 1,8-octanediol with alpha,omega-n-alkane diacids with 6-, 8-, 9-, 10-, and 13-carbon chain lengths was C13 = C10, where HiC showed little activity for C6, C8, and C9 diacid copolymerization. N435 displayed similar activity for all these diacid chain lengths. Thus, N435 has a broader substrate promiscuity than HiC-AO. This is most apparent for shorter chain length omegaHA, diol, and diacid monomers. These trends were similarly observed for a series of small molecule esterification reactions. Comparison of HiC-AO- and N435-catalyzed C16-HA homopolymerization at 8 h gave polymers with M(n) 40.4 and 25.5 kg/mol, respectively. Furthermore, HiC-AO- and N435-catalyzed copolymerization of 1,8-octanediol/C13-diacid polymerizations at 8 h gave polymers with M(n) of 11.0 and 9.6 kg/mol, respectively.

  15. Acetic Acid Catalyzed Steam Explosion for Improving the Sugar Recovery of Wheat Straw

    Directory of Open Access Journals (Sweden)

    Mengru Liu

    2014-06-01

    Full Text Available Acetic acid-catalyzed steam explosion pretreatment was applied to wheat straw at temperatures of 190 and 210 °C for 2, 6, and 10 min of residence time. The effects of pretreatment conditions on the total gravimetric recovery, hemicellulose sugars, glucose content, and yield of the enzymatic hydrolysis of cellulose were studied. The results indicated that the total gravimetric recovery decreases while the solubility of hemicellulose and the yield of cellulose enzymatic hydrolysis increase as the pretreatment severity increases. Pretreatment at 190 °C with a 2-min residence time resulted in the highest total gravimetric recovery, 58.9%. The optimum defiberation, glucose content, and enzymatic hydrolysis yields of 70.4 and 79.6%, respectively, occurred following pretreatment at 210 °C with a 10-min residence time. The optimal pretreatment condition was determined to be 190 °C for 10 min. Under the optimum conditions, the recovery yield of all sugars reached 42.7%. This pretreatment resulted in the highest recovery yield of all sugars.

  16. Cobalt-Catalyzed Vinylation of Organozinc Reagents with Aldehydes

    Institute of Scientific and Technical Information of China (English)

    WANG; JinXian

    2001-01-01

    Transtion metal catalyzed vinylation of organic halides are known to be a very convenient method for forming carbon-carbon bonds at unsubstituted vinylic position. The versatility of stilbenes is well known because of its various biological active components, the variety of its reactions in organic syntheses, and its ability to function as a bonding partner for metals in complexes.  Many methods have been described for the synthesis of stilbenes. The reduction, dehydrogenation, and elimination reactions leading to stilbenes without formation of new carbon-carbon bonds are known to be a very convenient methods. Synthetically more important are the dimerization reactions: oxidative or eleminative dimerization of a suitable methylarene often constitutes the method of choice for the preparation of a symmetric stilbene. Meerwein arylation and Heck reaction are prominent examples for the synthesis of stilbenes from arenes and styrenes. Moreover, condensation reactions of a nucleophilic with an electrophilic arylmethyl compound include Knoevenagel type reactions and the very general Wittig and Wittig-Horner reactions are also known methods.  ……

  17. Alkylation of Benzene with Propylene Catalyzed by Ionic Liquids

    Institute of Scientific and Technical Information of China (English)

    Sun Xuewen; Zhao Suoqi

    2006-01-01

    The alkylation of benzene with propylene catalyzed by ionic liquids to obtain cumene was investigated. Propylene conversion and cumene selectivity under mild reaction conditions were improved greatly after the ionic liquid was modified with HCl. Under the conditions of 20 oC, 0.1MPa, 5 min of reaction time, and a molar ratio of benzene to propylene of 10:1, propylene conversion increased from 83.6% to 100%, and cumene selectivity increased from 90.86% to 98.47%. In addition, it was found that the reaction could be carried out in two different stages so as to obtain a better result. At the first stage, the key reaction was alkylation and a higher propylene conversion was obtained at a lower temperature;At the second stage, the key reaction was transalkylation and a higher temperature was used to improve cumene selectivity. The reaction temperature, pressure and the amount of catalyst used in this work were lower than those used in traditional alkylation processes.

  18. Kinetics of acid base catalyzed transesterification of Jatropha curcas oil.

    Science.gov (United States)

    Jain, Siddharth; Sharma, M P

    2010-10-01

    Out of various non-edible oil resources, Jatropha curcas oil (JCO) is considered as future feedstock for biodiesel production in India. Limited work is reported on the kinetics of transesterification of high free fatty acids containing oil. The present study reports the results of kinetic study of two-step acid base catalyzed transesterification process carried out at an optimum temperature of 65 °C and 50 °C for esterification and transesterification respectively under the optimum methanol to oil ratio of 3:7 (v/v), catalyst concentration 1% (w/w) for H₂SO₄ and NaOH. The yield of methyl ester (ME) has been used to study the effect of different parameters. The results indicate that both esterification and transesterification reaction are of first order with reaction rate constant of 0.0031 min⁻¹ and 0.008 min⁻¹ respectively. The maximum yield of 21.2% of ME during esterification and 90.1% from transesterification of pretreated JCO has been obtained.

  19. Acid-catalyzed production of biodiesel from waste frying oil

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, S.; Dube, M.A.; McLean, D.D. [Department of Chemical Engineering, University of Ottawa, Ottawa, ON (Canada); Kates, M. [Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON (Canada)

    2006-03-15

    The reaction kinetics of acid-catalyzed transesterification of waste frying oil in excess methanol to form fatty acid methyl esters (FAME), for possible use as biodiesel, was studied. Rate of mixing, feed composition (molar ratio oil:methanol:acid) and temperature were independent variables. There was no significant difference in the yield of FAME when the rate of mixing was in the turbulent range 100 to 600rpm. The oil:methanol:acid molar ratios and the temperature were the most significant factors affecting the yield of FAME. At 70{sup o}C with oil:methanol:acid molar ratios of 1:245:3.8, and at 80{sup o}C with oil:methanol:acid molar ratios in the range 1:74:1.9-1:245:3.8, the transesterification was essentially a pseudo-first-order reaction as a result of the large excess of methanol which drove the reaction to completion (99+/-1% at 4h). In the presence of the large excess of methanol, free fatty acids present in the waste oil were very rapidly converted to methyl esters in the first few minutes under the above conditions. Little or no monoglycerides were detected during the course of the reaction, and diglycerides present in the initial waste oil were rapidly converted to FAME. (author)

  20. Enzyme-catalyzed Sequential Reduction of Carbon Dioxide to Formaldehyde☆

    Institute of Scientific and Technical Information of China (English)

    Wenfang Liu; Yanhui Hou; Benxiang Hou; Zhiping Zhao

    2014-01-01

    It has been reported that enzymatic-catalyzed reduction of CO2 is feasible. Most of literature focuses on the con-version of CO2 to methanol. Herein we put emphasis on the sequential conversion of CO2 to formaldehyde and its single reactions. It appears that CO2 pressure plays a critical role and higher pressure is greatly helpful to form more HCOOH as well as HCHO. The reverse reaction became severe in the reduction of CO2 to formaldehyde after 10 h, decreasing HCHO production. Increasing the mass ratio of formate dehydrogenase to formaldehyde dehydrogenase could promote the sequential reaction. At concentrations of nicotinamide adenine dinucleotide lower than 100 mmol·L−1, the reduction of CO2 was accelerated by increasing cofactor concentration. The opti-mum pH value and concentration of phosphate buffer were determined as 6.0 and 0.05 mol·L−1, respectively, for the overall reaction. It seems that thermodynamic factor such as pH is restrictive to the sequential reaction due to distinct divergence in appropriate pH range between its single reactions.

  1. On Transition Metal Catalyzed Reduction of N-nitrosodimethlamine

    CERN Document Server

    Zhou, Jun; Tian, Junhua; Zhao, Zhun

    2014-01-01

    This report provides a critical review on "Metal-Catalyzed Reduction of N-Nitrosodimethylamine with Hydrogen in Water", by Davie et al. N-nitrosodimethlamine (NDMA) is a contaminant in drinking and ground water which is difficult to remove by conventional physical methods, such as air stripping. Based on the reported robust capability of metal based powder shaped catalysts in hydrogen reduction, several monometallic and bimetallic catalyst are studied in this paper on the reduction of NDMA with hydrogen. Two kinds of kinetics, metal weight normalized and surface area normalized, are compared between each catalyst in terms of pseudo-first order reaction rate. Palladium, copper enhanced palladium and nickel are found to be very efficient in NDMA reduction, with half-lives on the order of hours per 10 mg/l catalyst metal. Preliminary LC-MS data and carbon balance showed no intermediates. Finally, a simple hydrogen and NMDA surface activated reaction mechanism is proposed by the author for palladium and nickel.

  2. Base-catalyzed depolymerization of lignin : separation of monomers

    Energy Technology Data Exchange (ETDEWEB)

    Vigneault, A. [Sherbrooke Univ., PQ (Canada). Dept. of Chemical Engineering; Johnson, D.K. [National Renewable Energy Laboratory, Golden, CO (United States); Chornet, E. [Sherbrooke Univ., PQ (Canada). Dept. of Chemical Engineering; National Renewable Energy Laboratory, Golden, CO (United States)

    2007-12-15

    Biofuels produced from residual lignocellulosic biomass range from ethanol to biodiesel. The use of lignin for the production of alternate biofuels and green chemicals has been studied with particular emphasis on the structure of lignin and its oxyaromatic nature. In an effort to fractionate lignocellulosic biomass and valorize specific constitutive fractions, the authors developed a strategy for the separation of 12 added value monomers produced during the hydrolytic base catalyzed depolymerization (BCD) of a Steam Exploded Aspen Lignin. The separation strategy was similar to vanillin purification to obtain pure monomers, but combining more steps after the lignin depolymerization such as acidification, batch liquid-liquid-extraction (LLE), followed by vacuum distillation, liquid chromatography (LC) and crystallization. The purpose was to develop basic data for an industrial size process flow diagram, and to evaluate both the monomer losses during the separation and the energy requirements. Experimentally testing of LLE, vacuum distillation and flash LC in the laboratory showed that batch vacuum distillation produced up to 4 fractions. Process simulation revealed that a series of 4 vacuum distillation columns could produce 5 distinct monomer streams, of which 3 require further chromatography and crystallization operations for purification. 22 refs., 4 tabs., 8 figs.

  3. Production of chemoenzymatic catalyzed monoepoxide biolubricant: optimization and physicochemical characteristics.

    Science.gov (United States)

    Salimon, Jumat; Salih, Nadia; Abdullah, Bashar Mudhaffar

    2012-01-01

    Linoleic acid (LA) is converted to per-carboxylic acid catalyzed by an immobilized lipase from Candida antarctica (Novozym 435). This per-carboxylic acid is only intermediate and epoxidized itself in good yields and almost without consecutive reactions. Monoepoxide linoleic acid 9(12)-10(13)-monoepoxy 12(9)-octadecanoic acid (MEOA) was optimized using D-optimal design. At optimum conditions, higher yield% (82.14) and medium oxirane oxygen content (OOC) (4.91%) of MEOA were predicted at 15 μL of H(2)O(2), 120 mg of Novozym 435, and 7 h of reaction time. In order to develop better-quality biolubricants, pour point (PP), flash point (FP), viscosity index (VI), and oxidative stability (OT) were determined for LA and MEOA. The results showed that MEOA exhibited good low-temperature behavior with PP of -41(°)C. FP of MEOA increased to 128(°)C comparing with 115(°)C of LA. In a similar fashion, VI for LA was 224 generally several hundred centistokes (cSt) more viscous than MEOA 130.8. The ability of a substance to resist oxidative degradation is another important property for biolubricants. Therefore, LA and MEOA were screened to measure their OT which was observed at 189 and 168(°)C, respectively.

  4. Production of Chemoenzymatic Catalyzed Monoepoxide Biolubricant: Optimization and Physicochemical Characteristics

    Directory of Open Access Journals (Sweden)

    Jumat Salimon

    2012-01-01

    Full Text Available Linoleic acid (LA is converted to per-carboxylic acid catalyzed by an immobilized lipase from Candida antarctica (Novozym 435. This per-carboxylic acid is only intermediate and epoxidized itself in good yields and almost without consecutive reactions. Monoepoxide linoleic acid 9(12-10(13-monoepoxy 12(9-octadecanoic acid (MEOA was optimized using D-optimal design. At optimum conditions, higher yield% (82.14 and medium oxirane oxygen content (OOC (4.91% of MEOA were predicted at 15 μL of H2O2, 120 mg of Novozym 435, and 7 h of reaction time. In order to develop better-quality biolubricants, pour point (PP, flash point (FP, viscosity index (VI, and oxidative stability (OT were determined for LA and MEOA. The results showed that MEOA exhibited good low-temperature behavior with PP of −41°C. FP of MEOA increased to 128°C comparing with 115°C of LA. In a similar fashion, VI for LA was 224 generally several hundred centistokes (cSt more viscous than MEOA 130.8. The ability of a substance to resist oxidative degradation is another important property for biolubricants. Therefore, LA and MEOA were screened to measure their OT which was observed at 189 and 168°C, respectively.

  5. Lipase catalyzed esterification of glycidol in organic solvents.

    Science.gov (United States)

    Martins, J F; Da Ponte, M N; Barreiros, S

    1993-08-05

    We studied the resolution of racemic glycidol through esterification with butyric acid catalyzed by porcine pancreatic lipase in organic media. A screening of seven solvents (log P values between 0.49 and 3.0, P being the n-octanol-water partition coefficient of the solvent) showed that neither log P nor the logarithm of the molar solubility of water in the solvent provides good correlations between enantioselectivity and the properties of the organic media. Chloroform was one of the best solvents as regards the enantiomeric purity (e. p.) of the ester produced. In this solvent, the optimum temperature for the reaction was determined to be 35 degrees C. The enzyme exhibited maximum activity at a water content of 13 +/- 2% (w/w). The enantiomeric purity obtained was 83 +/- 2% of (S)-glycidyl butyrate and did not depend on the alcohol concentration or the enzyme water content for values of these parameters up to 200 mM and 25% (w/w), respectively. The reaction was found to follow a BiBi mechanism.

  6. Kinetics of phenolic polymerization catalyzed by peroxidase in organic media

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y.P.; Huang, G.L; Yu, Y.T. [Nankai Univ., Tianjin (China). Inst. for Molecular Biology

    1995-07-05

    Phenolic polymerization was carried out by enzymatic catalysis in organic media, and its kinetics was studied by using high-pressure liquid chromatography (HPLC). Phenols and aromatic amines with electron-withdrawing groups could hardly be polymerized by HRP catalysis, but phenols and aromatic amines with electron-donating groups could easily by polymerized. The reaction rate of either the para-substituted substrate or meta-substituted substrate was higher than that of ortho-substituted substrate. When ortho-position of hydroxy group of phenols was occupied by an electron-donating group and if another electron-donating group occupied para-position of hydroxy group, the reaction rate increased. Horseradish peroxidase and lactoperoxidase could easily catalyze the polymerization, but chloroperoxidase and laccase failed to yield polymers. Metallic ions such as Mn{sup 2+}, Fe{sup 2+}, or Fe{sup 3+}, and Cu{sup 2+} could poison horseradish peroxidase to various extents, but ions such as Co{sup 2+}, Cd{sup 2+}, Zn{sup 2+}, and K{sup +} were not found to inhibit the reaction.

  7. Self-catalyzed Effect and Cracking Risk in Mass Concrete Containing Micro-slag

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The main results obtained from the experimental and engineering investigation on the heat evolution and cracking risk of a furnace concrete block were presented. The heat evolution of experimental mortars containing micro-slag under different environmental temperatures was instrumented in order to investigate the self-catalyzed effect, which was discovered in engineering. Moreover, the thermal stress of the furnace concrete due to heat temperature rise was calculated to evaluate the cracking risk of mass concrete containing micro-slag due to self-catalyzed effect. The experimental results illustrate that with the development of hydration and initial temperature of mixture, the hydration can be also accelerated and temperature of concrete will be continued to rise, which was the self-catalyzed effect. And the thermal stress due to self-catalyzed effect could not result in the cracking of furnace concrete.

  8. PALLADIUM-CATALYZED OXIDATION OF STYRENE AND ALKENES IN PRESENCE OF IONIC LIQUIDS (WACKER REACTION)

    Science.gov (United States)

    The use of ionic liquids in various synthetic transformations is gaining significance due to the enhanced reaction rates, potential for recycling and compatibility with various organic compounds and organometallic catalysts. Palladium-catalyzed oxidation of styrene and other alk...

  9. Regiospecific Addition of Uracil to Acrylates Catalyzed by Alkaline Protease from Bacillus subtilis

    Institute of Scientific and Technical Information of China (English)

    Ying CAI; Jian Yi WU; Na WANG; Xiao Feng SUN; Xian Fu LIN

    2004-01-01

    Michael addition reactions of uracil to acrylates were catalyzed by an alkaline protease from Bacillus subtilis in dimethyl sulfoxide at 55 ℃ for 72 h. The adducts were determined by TLC, IR and 1H NMR.

  10. The applications of Schiff bases in Ti-catalyzed asymmetric alkynylation of aldehydes

    Institute of Scientific and Technical Information of China (English)

    Xian Jia; Lu Yin; Xuan Zhao; Xing Shu Li

    2007-01-01

    Sciff bases 1 and 2, which were derived from chiral aminoalcohols, were used as ligands in Ti-catalyzed asymmetric alkynylation of aldehydes. Good enantioselectivities (up to 88% ee) and high chemical yields (80-90 %) were obtained.

  11. Highly Efficient Synthesis of Bis(indolyl)methanes Catalyzed by Sodium Tetrafluoroborate

    Institute of Scientific and Technical Information of China (English)

    KAMBLE,Vinod Tribhuvannathji; BANDGAR,Babasaheb Pandurang; BAVIKAR,Sudhir Narayanrao

    2007-01-01

    Sodium tetrafluoroborate (NaBF4) was found to catalyze the electrophilic substitution reactions of indoles with aldehydes and ketones under solvent-free conditions to afford the corresponding bis(indolyl)methanes in high yields.

  12. Hydroaminomethylation of 1-Dodecene Catalyzed by Water-soluble Rhodium Complex

    Institute of Scientific and Technical Information of China (English)

    Ying Yong WANG; Mei Ming LUO; Yao Zhong LI; Hua CHEN; Xian Jun LI

    2004-01-01

    The hydroaminomethylation of 1-dodecene catalyzed by water soluble rhodium complex RhCl(CO)(TPPTS)2 in the presence of surfactant CTAB was investigated. High reactivity and selectivity for tertiary amine were achieved under relatively mild conditions.

  13. Palladium-catalyzed Cascade Cyclization-Coupling Reaction of Benzyl Halides with N,N-Diallylbenzoylamide

    Institute of Scientific and Technical Information of China (English)

    Yi Min HU; Yu ZHANG; Jian Lin HAN; Cheng Jian ZHU; Yi PAN

    2003-01-01

    A novel type of palladium-catalyzed cascade cyclization-coupling reaction has been found. Reaction of N, N-diallylbenzoylamide 1 with benzyl halides 2 afforded the corresponding dihydropyrroles 3 in moderate to excellent yields.

  14. The mechanism for the rhodium-catalyzed decarbonylation of aldehydes: A combined experimental and theoretical study

    DEFF Research Database (Denmark)

    Fristrup, Peter; Kreis, Michael; Palmelund, Anders;

    2008-01-01

    The mechanism for the rhodium-catalyzed decarbonylation of aldehydes was investigated by experimental techniques (Hammett studies and kinetic isotope effects) and extended by a computational study (DFT calculations). For both benzaldehyde and phenyl acetaldehyde derivatives, linear Hammett plots ...

  15. NOx-Catalyzed Gas-Phase Activation of Methane:the Formation of Hydrogen

    Institute of Scientific and Technical Information of China (English)

    Chaoxian Xiao; Zhen Yan; Yuan Kou

    2003-01-01

    NOx-catalyzed oxidation of methane without a solid catalyst was investigated, and a hydrogen selectivity of 27% was obtained with an overall methane conversion of 34% and a free O2 concentration of 1.7% at 700 ℃.

  16. Iridium-catalyzed annulation of salicylimines with 1,3-dienes.

    Science.gov (United States)

    Ebe, Yusuke; Nishimura, Takahiro

    2014-07-01

    Iridium-catalyzed annulation of salicylimines with 1,3-dienes gave high yields of the corresponding 4-aminochromanes with high stereoselectivity. The use of a chiral diene ligand enabled the asymmetric reaction to give 4-aminochromanes with high enantioselectivity.

  17. Three-component synthesis of amidoalkyl naphthols catalyzed by bismuth(Ⅲ) nitrate pentahydrate

    Institute of Scientific and Technical Information of China (English)

    Min Wang; Yan Liang; Ting Ting Zhang; Jing Jing Gao

    2012-01-01

    Bismuth(Ⅲ) nitrate pentahydrate catalyzed the three-component condensation of β-naphthol,aldehydes and amines/urea under solvent-free conditions to afford the corresponding amidoalkyl naphthols in excellent yields.

  18. Regioselective Palladium-Catalyzed Cross-Coupling Reactions of 2,4,7-Trichloroquinazoline.

    Science.gov (United States)

    Wipf, Peter; George, Kara M

    2010-03-01

    The regioselective palladium-catalyzed cross-coupling reactions of 2,4,7-trichloroquinazoline with various aryl- and heteroarylboronic acids are reported. An efficient, sequential strategy was developed that provides access to novel, functionalized heterocycles.

  19. GREEN CATALYZED OXIDATION OF HYDROCARBONS IN ALTERNATIVE SOLVENT SYSTEMS GENERATED BY PARIS II

    Science.gov (United States)

    Green Catalyzed Oxidation of Hydrocarbons in Alternative Solvent Systems Generated by PARIS IIMichael A. Gonzalez*, Thomas M. Becker, and Paul F. Harten; Sustainable Technology Division, Office of Research and Development; United States Environmental Protection Agency, 26...

  20. Highly enantioselective [4 + 2] cyclization of chloroaldehydes and 1-azadienes catalyzed by N-heterocyclic carbenes.

    Science.gov (United States)

    Jian, Teng-Yue; Sun, Li-Hui; Ye, Song

    2012-11-14

    Highly functionalized dihydropyridinones were synthesized via the N-heterocyclic carbene-catalyzed enantioselective [4 + 2] annulation of α-chloroaldehydes and azadienes. Hydrogenation of the resulted dihydropyridinones afforded the corresponding piperidinones with high enantiopurity.

  1. Horseradish peroxidase catalyzed free radical cannot free move in reaction solution

    OpenAIRE

    2009-01-01

    Mechanism of Horseradish Peroxidase -catalyzed phenol compound oxidizing reaction is a radical polymerization. Many polymer preparation are also carry on through the radical polymerization mechanism We deduce if free radical produced by peroxidasecatalyzed phenol polymerization could apply on polymer preparation? Could the phenol–oxygen free radical leave off the peroxidase and catalyze other compounds polymerization? The free radical in phenol oxidation process was investigated in homo...

  2. Ready Access to the Echinopines Skeleton via Gold(I)-Catalyzed Alkoxycyclizations of Enynes.

    Science.gov (United States)

    Dorel, Ruth; Echavarren, Antonio M

    2016-09-16

    The [3,5,5,7] tetracyclic skeleton of echinopines has been stereoselectively accessed through a gold(I)-catalyzed alkoxycyclization of cyclopropyl-tethered 1,6-enynes. The key bicyclo[4.2.1]nonane core of the enyne precursors was readily assembled by means of a Co-catalyzed [6 + 2] cycloaddition. Furthermore, the attempted alkoxycyclization of 1,5-enyne substrates revealed an uncovered cyclopropyl rearrangement that gives rise to [3,6,5,7] tetracyclic structures.

  3. Modeling Lipase-Catalyzed Biodiesel Production in [BMIM][PF6

    OpenAIRE

    JianJun Yang; MingYan Yang

    2016-01-01

    Lipase-catalyzed biodiesel production models in room temperature ionic liquids (RTILs) reaction medium available in the literature are valid especially for mixing intensity. In this paper, a preliminary model is established in order to try to describe the lipase-catalyzed biodiesel production process in RTILs in a stirring type bioreactor. Mixing intensity and time delay were inspected for the reaction model in [BMIM][PF6] medium. As a result, this model is a good explanation for these actual...

  4. NMR spectroscopic investigations on copper-catalyzed reactions and zintl anions

    OpenAIRE

    Koch, Carina

    2016-01-01

    The copper-catalyzed asymmetric conjugated 1,4-addition reaction of organozinc reagents to a,b-unsaturated compounds is a very effective and widely used method for the enantioselective carbon-carbon bond formation. By the use of phosphoramidite ligands it is possible to reach ee-values and conversion up to > 99 %. Furthermore, this outstanding reaction provides lower costs in comparison to other transition-metal catalyzed reactions and compatibility to many functional groups. Despite the grea...

  5. Biodiesel Production from Spent Fish Frying Oil Through Acid-Base Catalyzed Transesterification

    OpenAIRE

    Abdalrahman B. Fadhil; Mohammed M. Dheyab; Kareem M. Ahmed; Marwa H. Yahya

    2012-01-01

    Biodiesel fuels were prepared from a special type of frying oil namely spent fish frying oil through two step transesterification viz. acid-base catalyzed transesterification. Hydrochloric acid and potassium hydroxide with methanol were used for this purpose. The oil was pre-treated with (1.0 wt% HCl) and methanol to reduce free fatty acids content of the oil. Then, conditions of the base catalyzed step such as base concentration, reaction temperature, methanol to oil molar ratio and reaction...

  6. Mo-catalyzed asymmetric olefin metathesis in target-oriented synthesis: Enantioselective synthesis of (+)-africanol

    Science.gov (United States)

    Weatherhead, Gabriel S.; Cortez, G. A.; Schrock, Richard R.; Hoveyda, Amir H.

    2004-01-01

    Catalytic asymmetric ring-opening metathesis (AROM) provides an efficient method for the synthesis of a variety of optically enriched small organic molecules that cannot be easily prepared by alternative methods. The development of Mo-catalyzed AROM transformations that occur in tandem with ring-closing metathesis are described. The utility of the Mo-catalyzed AROM/ring-closing metathesis is demonstrated through an enantioselective approach to the synthesis of (+)-africanol. PMID:15056762

  7. Direct Evidence of a Dinuclear Copper Intermediate in Cu(I)-Catalyzed Azide–Alkyne Cycloadditions

    OpenAIRE

    Worrell, B. T.; Malik, J.A.; FOKIN, V.V.

    2013-01-01

    The copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) has become a commonly employed method for the synthesis of complex molecular architectures under challenging conditions. Despite the widespread use of copper-catalyzed cycloaddition reactions, the mechanism of these processes has remained difficult to establish due to the involvement of multiple equilibria between several reactive intermediates. Real-time monitoring of a representative cycloaddition process via heat flow reaction calo...

  8. Palladium-Catalyzed Nucleophilic Substitution of Alcohols : Mechanistic Studies and Synthetic Applications

    OpenAIRE

    Sawadjoon, Supaporn

    2013-01-01

    This thesis deals with the palladium-catalyzed nucleophilic substitution of π-activated alcohols in which the C–O bond of a non-manipulated hydroxyl group is cleaved. The thesis is divided in two chapters describing two different catalytic systems. Chapter 2 describes a heterogeneous palladium-catalyzed transfer hydrogenolysis of primary, secondary, and tertiary benzylic alcohols to generate the corresponding aromatic hydrocarbons using formic acid as the hydrogen donor. A detailed mechanisti...

  9. Use of a palladium(II)-catalyzed oxidative kinetic resolution in synthetic efforts toward bielschowskysin.

    Science.gov (United States)

    Meyer, Michael E; Phillips, John H; Ferreira, Eric M; Stoltz, Brian M

    2013-09-09

    Progress toward the cyclobutane core of bielshowskysin is reported. The core was thought to arise from a cyclopropane intermediate via a furan-mediated cyclopropane fragmentation, followed by a 1,4-Michael addition. The synthesis of the cyclopropane intermediate utilizes a Suzuki coupling reaction, an esterification with 2-diazoacetoacetic acid, and a copper catalyzed cyclopropanation. An alcohol intermediate within the synthetic route was obtained in high enantiopurity via a highly selective palladium(II)-catalyzed oxidative kinetic resolution (OKR).

  10. Cyclization strategies to polyenes using Pd(II)-catalyzed couplings of pinacol vinylboronates.

    Science.gov (United States)

    Iafe, Robert G; Chan, Daniel G; Kuo, Jonathan L; Boon, Byron A; Faizi, Darius J; Saga, Tomomi; Turner, Jonathan W; Merlic, Craig A

    2012-08-17

    As a complement to Pd(0)-catalyzed cyclizations, seven Pd(II)-catalyzed cyclization strategies are reported. α,ω-Diynes are selectively hydroborated to bis(boronate esters), which cyclize under Pd(II)-catalysis producing a diverse array of small, medium, and macrocyclic polyenes with controlled E,E, Z,Z, or E,Z stereochemistry. Various functional groups are tolerated including aryl bromides, and applications are illustrated.

  11. Silver-Catalyzed Decarboxylative Addition/Cyclization of Activated Alkenes with Aliphatic Carboxylic Acids.

    Science.gov (United States)

    Xia, Xiao-Feng; Zhu, Su-Li; Chen, Chao; Wang, Haijun; Liang, Yong-Min

    2016-02-05

    A silver-catalyzed decarboxylative addition/aryl migration/desulfonylation of N-phenyl-N-(phenylsulfonyl)methacrylamide with primary, secondary, and tertiary carboxylic acids was described. The protocol provides an efficient approach for the synthesis of α-all-carbon quaternary stereocenters amides and isoquinolinediones. It was proposed that the radical generated from the silver-catalyzed decarboxylation was involved in the sequence reaction.

  12. Horseradish Peroxidase-Mediated, Iodide-Catalyzed Cascade Reaction for Plasmonic Immunoassays.

    Science.gov (United States)

    Xianyu, Yunlei; Chen, Yiping; Jiang, Xingyu

    2015-11-01

    This report outlines an enzymatic cascade reaction for signal transduction and amplification for plasmonic immunoassays by using horseradish peroxidase (HRP)-mediated aggregation of gold nanoparticles (AuNPs). HRP-catalyzed oxidation of iodide and iodide-catalyzed oxidation of cysteine is employed to modulate the plasmonic signals of AuNPs. It agrees well with the current immunoassay platforms and allows naked-eye readout with enhanced sensitivity, which holds great promise for applications in resource-constrained settings.

  13. Multidirectional Synthesis of Substituted Indazoles via Iridium-Catalyzed C-H Borylation.

    Science.gov (United States)

    Sadler, Scott A; Hones, Andrew C; Roberts, Bryan; Blakemore, David; Marder, Todd B; Steel, Patrick G

    2015-05-15

    In the absence of a steric directing group, iridium-catalyzed C-H borylation of N-protected indazoles occurs rapidly and selectively at C-3 and the resulting boronate esters can be utilized in a range of downstream conversions. The functional group tolerance of the iridium-catalyzed C-H borylation reaction enables simple and efficient multidirectional syntheses of substituted indazoles to be realized.

  14. Ready Access to the Echinopines Skeleton via Gold(I)-Catalyzed Alkoxycyclizations of Enynes

    Science.gov (United States)

    2016-01-01

    The [3,5,5,7] tetracyclic skeleton of echinopines has been stereoselectively accessed through a gold(I)-catalyzed alkoxycyclization of cyclopropyl-tethered 1,6-enynes. The key bicyclo[4.2.1]nonane core of the enyne precursors was readily assembled by means of a Co-catalyzed [6 + 2] cycloaddition. Furthermore, the attempted alkoxycyclization of 1,5-enyne substrates revealed an uncovered cyclopropyl rearrangement that gives rise to [3,6,5,7] tetracyclic structures. PMID:27529429

  15. The application of rational design on phospholipase A(2) inhibitors.

    Science.gov (United States)

    Mouchlis, V D; Barbayianni, E; Mavromoustakos, T M; Kokotos, G

    2011-01-01

    The phospholipase A(2) (PLA(2)) superfamily consists of different groups of enzymes which are characterized by their ability to catalyze the hydrolysis of the sn-2 ester bond in a variety of phospholipid molecules. The products of PLA(2s) activity play divergent roles in a variety of physiological processes. There are four main types of PLA(2s): the secreted PLA(2s) (sPLA(2s)), the cytosolic PLA(2s) (cPLA(2s)), the calcium-independent PLA(2s) (iPLA(2)) and the lipoprotein-associated PLA(2s) (LpPLA(2s)). Various potent and selective PLA2 inhibitors have been reported up to date and have provided outstanding support in understanding the mechanism of action and elucidating the function of these enzymes. The current review focuses on the implementation of rational design through computer-aided drug design (CADD) on the discovery and development of new PLA(2) inhibitors.

  16. A review on biodiesel production using catalyzed transesterification

    Energy Technology Data Exchange (ETDEWEB)

    Leung, Dennis Y.C.; Wu, Xuan; Leung, M.K.H. [Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong (China)

    2010-04-15

    Biodiesel is a low-emissions diesel substitute fuel made from renewable resources and waste lipid. The most common way to produce biodiesel is through transesterification, especially alkali-catalyzed transesterification. When the raw materials (oils or fats) have a high percentage of free fatty acids or water, the alkali catalyst will react with the free fatty acids to form soaps. The water can hydrolyze the triglycerides into diglycerides and form more free fatty acids. Both of the above reactions are undesirable and reduce the yield of the biodiesel product. In this situation, the acidic materials should be pre-treated to inhibit the saponification reaction. This paper reviews the different approaches of reducing free fatty acids in the raw oil and refinement of crude biodiesel that are adopted in the industry. The main factors affecting the yield of biodiesel, i.e. alcohol quantity, reaction time, reaction temperature and catalyst concentration, are discussed. This paper also described other new processes of biodiesel production. For instance, the Biox co-solvent process converts triglycerides to esters through the selection of inert co-solvents that generates a one-phase oil-rich system. The non-catalytic supercritical methanol process is advantageous in terms of shorter reaction time and lesser purification steps but requires high temperature and pressure. For the in situ biodiesel process, the oilseeds are treated directly with methanol in which the catalyst has been preciously dissolved at ambient temperatures and pressure to perform the transesterification of oils in the oilseeds. This process, however, cannot handle waste cooking oils and animal fats. (author)

  17. The mechanism for iron-catalyzed alkene isomerization in solution

    Energy Technology Data Exchange (ETDEWEB)

    Sawyer, Karma R.; Glascoe, Elizabeth A.; Cahoon, James F.; Schlegel, Jacob P.; Harris, Charles B.

    2008-05-27

    Here we report nano- through microsecond time-resolved IR experiments of iron-catalyzed alkene isomerization in room-temperature solution. We have monitored the photochemistry of a model system, Fe(CO){sub 4}({eta}{sup 2}-1-hexene), in neat 1-hexene solution. UV-photolysis of the starting material leads to the dissociation of a single CO to form Fe(CO){sub 3}({eta}{sup 2}-1-hexene), in a singlet spin state. This CO loss complex shows a dramatic selectivity to form an allyl hydride, HFe(CO){sub 3}({eta}{sup 3}-C{sub 6}H{sub 11}), via an internal C-H bond-cleavage reaction in 5-25 ns. We find no evidence for the coordination of an alkene molecule from the bath to the CO loss complex, but do observe coordination to the allyl hydride, indicating that it is the key intermediate in the isomerization mechanism. Coordination of the alkene ligand to the allyl hydride leads to the formation of the bis-alkene isomers, Fe(CO){sub 3}({eta}{sup 2}-1-hexene)({eta}{sup 2}-2-hexene) and Fe(CO){sub 3}({eta}{sup 2}-1-hexene){sub 2}. Because of the thermodynamic stability of Fe(CO){sub 3}({eta}{sup 2}-1-hexene)({eta}{sup 2}-2-hexene) over Fe(CO){sub 3}({eta}{sup 2}-1-hexene){sub 2} (ca. 12 kcal/mol), nearly 100% of the alkene population will be 2-alkene. The results presented herein provide the first direct evidence for this mechanism in solution and suggest modifications to the currently accepted mechanism.

  18. Electrochemically protected copper(I)-catalyzed azide-alkyne cycloaddition.

    Science.gov (United States)

    Hong, Vu; Udit, Andrew K; Evans, Richard A; Finn, M G

    2008-06-16

    The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has found broad application in myriad fields. For the most demanding applications that require high yields at low substrate concentrations, highly active but air-sensitive copper complexes must be used. We describe here the use of an electrochemical potential to maintain catalysts in the active Cu(I) oxidation state in the presence of air. This simple procedure efficiently achieves excellent yields of CuAAC products from both small-molecule and protein substrates without the use of potentially damaging chemical reducing agents. A new water-soluble carboxylated version of the popular tris(benzyltriazolylmethyl)amine (TBTA) ligand is also described. Cyclic voltammetry revealed reversible or quasi-reversible electrochemical redox behavior of copper complexes of the TBTA derivative (2; E(1/2)=60 mV vs. Ag/AgCl), sulfonated bathophenanthroline (3; E(1/2)=-60 mV), and sulfonated tris(benzimidazoylmethyl)amine (4; E(1/2) approximately -70 mV), and showed catalytic turnover to be rapid relative to the voltammetry time scale. Under the influence of a -200 mV potential that was established by using a reticulated vitreous carbon working electrode, CuSO4 and 3 formed a superior catalyst. Electrochemically protected bioconjugations in air were performed by using bacteriophage Qbeta that was derivatized with azide moieties at surface lysine residues. Complete derivatization of more than 600 reactive sites per particle was demonstrated within 12 h of electrolysis with substoichiometric quantities of Cu3.

  19. Trinucleotide repeat expansions catalyzed by human cell-free extracts

    Institute of Scientific and Technical Information of China (English)

    Jennifer R Stevens; Elaine E Lahue; Guo-Min Li; Robert S Lahue

    2013-01-01

    Trinucleotide repeat expansions cause 17 heritable human neurological disorders.In some diseases,somatic expansions occur in non-proliferating tissues such as brain where DNA replication is limited.This finding stimulated significant interest in replication-independent expansion mechanisms.Aberrant DNA repair is a likely source,based in part on mouse studies showing that somatic expansions are provoked by the DNA repair protein MutSβ (Msh2-Msh3complex).Biochemical studies to date used cell-free extracts or purified DNA repair proteins to yield partial reactions at triplet repeats.The findings included expansions on one strand but not the other,or processing of DNA hairpin structures thought to be important intermediates in the expansion process.However,it has been difficult to recapitulate complete expansions in vitro,and the biochemical role of MutSβ remains controversial.Here,we use a novel in vitro assay to show that human cell-free extracts catalyze expansions and contractions of trinucleotide repeats without the requirement for DNA replication.The extract promotes a size range of expansions that is similar to certain diseases,and triplet repeat length and sequence govern expansions in vitro as in vivo.MutSβ stimulates expansions in the extract,consistent with aberrant repair of endogenous DNA damage as a source of expansions.Overall,this biochemical system retains the key characteristics of somatic expansions in humans and mice,suggesting that this important mutagenic process can be restored in the test tube.

  20. Copper-catalyzed azide alkyne cycloaddition polymer networks

    Science.gov (United States)

    Alzahrani, Abeer Ahmed

    The click reaction concept, introduced in 2001, has since spurred the rapid development and reexamination of efficient, high yield reactions which proceed rapidly under mild conditions. Prior to the discovery of facile copper catalysis in 2002, the thermally activated azide-alkyne or Huisgen cycloaddition reaction was largely ignored following its discovery in large part due to its slow kinetics, requirement for elevated temperature and limited selectivity. Now, arguably, the most prolific and capable of the click reactions, the copper-catalyzed azide alkyne cycloaddition (CuAAC) reaction is extremely efficient and affords exquisite control of the reaction. The orthogonally and chemoselectivity of this reaction enable its wide utility across varied scientific fields. Despite numerous inherent advantages and widespread use for small molecule synthesis and solution-based polymer chemistry, it has only recently and rarely been utilized to form polymer networks. This work focuses on the synthesis, mechanisms, and unique attributes of the CuAAC reaction for the fabrication of functional polymer networks. The photo-reduction of a series of copper(II)/amine complexes via ligand metal charge transfer was examined to determine their relative efficiency and selectivity in catalyzing the CuAAC reaction. The aliphatic amine ligands were used as an electron transfer species to reduce Cu(II) upon irradiation with 365 nm light while also functioning as an accelerating agent and as protecting ligands for the Cu(I) that was formed. Among the aliphatic amines studied, tertiary amines such as triethylamine (TEA), tetramethyldiamine (TMDA), N,N,N',N",N"-pentamethyldiethylenetriamine (PMDTA), and hexamethylenetetramine (HMTETA) were found to be the most effective. The reaction kinetics were accelerated by increasing the PMDETA : Cu(II) ratio with a ratio of ligand to Cu(II) of 4:1 yielding the maximum conversion in the shortest time. The sequential and orthogonal nature of the photo

  1. The mechanism of the NHC catalyzed aza-Morita-Baylis-Hillman reaction: insights into a new substrate-catalyzed bimolecular pathway.

    Science.gov (United States)

    Verma, Pritha; Verma, Pragya; Sunoj, Raghavan B

    2014-04-14

    The first mechanistic study on the NHC-catalyzed aza-MBH reaction between cyclopentenone and N-mesylbenzaldimine using density functional theory reveals that a bimolecular mechanism, involving two molecules of benzaldimine in the proton transfer, is energetically more preferred over the conventional direct proton transfer.

  2. Growth and characterization of gold catalyzed SiGe nanowires and alternative metal-catalyzed Si nanowires

    Directory of Open Access Journals (Sweden)

    Gentile Pascal

    2011-01-01

    Full Text Available Abstract The growth of semiconductor (SC nanowires (NW by CVD using Au-catalyzed VLS process has been widely studied over the past few years. Among others SC, it is possible to grow pure Si or SiGe NW thanks to these techniques. Nevertheless, Au could deteriorate the electric properties of SC and the use of other metal catalysts will be mandatory if NW are to be designed for innovating electronic. First, this article's focus will be on SiGe NW's growth using Au catalyst. The authors managed to grow SiGe NW between 350 and 400°C. Ge concentration (x in Si1- x Ge x NW has been successfully varied by modifying the gas flow ratio: R = GeH4/(SiH4 + GeH4. Characterization (by Raman spectroscopy and XRD revealed concentrations varying from 0.2 to 0.46 on NW grown at 375°C, with R varying from 0.05 to 0.15. Second, the results of Si NW growths by CVD using alternatives catalysts such as platinum-, palladium- and nickel-silicides are presented. This study, carried out on a LPCVD furnace, aimed at defining Si NW growth conditions when using such catalysts. Since the growth temperatures investigated are lower than the eutectic temperatures of these Si-metal alloys, VSS growth is expected and observed. Different temperatures and HCl flow rates have been tested with the aim of minimizing 2D growth which induces an important tapering of the NW. Finally, mechanical characterization of single NW has been carried out using an AFM method developed at the LTM. It consists in measuring the deflection of an AFM tip while performing approach-retract curves at various positions along the length of a cantilevered NW. This approach allows the measurement of as-grown single NW's Young modulus and spring constant, and alleviates uncertainties inherent in single point measurement.

  3. Ruthenium-Catalyzed Ammonia Borane Dehydrogenation: Mechanism and Utility.

    Science.gov (United States)

    Zhang, Xingyue; Kam, Lisa; Trerise, Ryan; Williams, Travis J

    2017-01-17

    One of the greatest challenges in using H2 as a fuel source is finding a safe, efficient, and inexpensive method for its storage. Ammonia borane (AB) is a solid hydrogen storage material that has garnered attention for its high hydrogen weight density (19.6 wt %) and ease of handling and transport. Hydrogen release from ammonia borane is mediated by either hydrolysis, thus giving borate products that are difficult to rereduce, or direct dehydrogenation. Catalytic AB dehydrogenation has thus been a popular topic in recent years, motivated both by applications in hydrogen storage and main group synthetic chemistry. This Account is a complete description of work from our laboratory in ruthenium-catalyzed ammonia borane dehydrogenation over the last 6 years, beginning with the Shvo catalyst and resulting ultimately in the development of optimized, leading catalysts for efficient hydrogen release. We have studied AB dehydrogenation with Shvo's catalyst extensively and generated a detailed understanding of the role that borazine, a dehydrogenation product, plays in the reaction: it is a poison for both Shvo's catalyst and PEM fuel cells. Through independent syntheses of Shvo derivatives, we found a protective mechanism wherein catalyst deactivation by borazine is prevented by coordination of a ligand that might otherwise be a catalytic poison. These studies showed how a bidentate N-N ligand can transform the Shvo into a more reactive species for AB dehydrogenation that minimizes accumulation of borazine. Simultaneously, we designed novel ruthenium catalysts that contain a Lewis acidic boron to replace the Shvo -OH proton, thus offering more flexibility to optimize hydrogen release and take on more general problems in hydride abstraction. Our scorpionate-ligated ruthenium species (12) is a best-of-class catalyst for homogeneous dehydrogenation of ammonia borane in terms of its extent of hydrogen release (4.6 wt %), air tolerance, and reusability. Moreover, a synthetically

  4. Polymer multilayer films obtained by electrochemically catalyzed click chemistry.

    Science.gov (United States)

    Rydzek, Gaulthier; Thomann, Jean-Sébastien; Ben Ameur, Nejla; Jierry, Loïc; Mésini, Philippe; Ponche, Arnaud; Contal, Christophe; El Haitami, Alae E; Voegel, Jean-Claude; Senger, Bernard; Schaaf, Pierre; Frisch, Benoît; Boulmedais, Fouzia

    2010-02-16

    We report the covalent layer-by-layer construction of polyelectrolyte multilayer (PEM) films by using an efficient electrochemically triggered Sharpless click reaction. The click reaction is catalyzed by Cu(I) which is generated in situ from Cu(II) (originating from the dissolution of CuSO(4)) at the electrode constituting the substrate of the film. The film buildup can be controlled by the application of a mild potential inducing the reduction of Cu(II) to Cu(I) in the absence of any reducing agent or any ligand. The experiments were carried out in an electrochemical quartz crystal microbalance cell which allows both to apply a controlled potential on a gold electrode and to follow the mass deposited on the electrode through the quartz crystal microbalance. Poly(acrylic acid) (PAA) modified with either alkyne (PAA(Alk)) or azide (PAA(Az)) functions grafted onto the PAA backbone through ethylene glycol arms were used to build the PEM films. Construction takes place on gold electrodes whose potentials are more negative than a critical value, which lies between -70 and -150 mV vs Ag/AgCl (KCl sat.) reference electrode. The film thickness increment per bilayer appears independent of the applied voltage as long as it is more negative than the critical potential, but it depends upon Cu(II) and polyelectrolyte concentrations in solution and upon the reduction time of Cu(II) during each deposition step. An increase of any of these latter parameters leads to an increase of the mass deposited per layer. For given buildup conditions, the construction levels off after a given number of deposition steps which increases with the Cu(II) concentration and/or the Cu(II) reduction time. A model based on the diffusion of Cu(II) and Cu(I) ions through the film and the dynamics of the polyelectrolyte anchoring on the film, during the reduction period of Cu(II), is proposed to explain the major buildup features.

  5. Ru(ii)-Catalyzed C-H activation and annulation of salicylaldehydes with monosubstituted and disubstituted alkynes.

    Science.gov (United States)

    Baruah, Swagata; Kaishap, Partha Pratim; Gogoi, Sanjib

    2016-10-27

    The Ru(ii)-catalyzed C-H activation and annulation reaction of salicylaldehydes and disubstituted alkynes affords chromones in high yields. This reaction also works with terminal alkynes and tolerates a wide range of sensitive functional groups. The selectivity pattern of this Ru(ii)-catalyzed annulation reaction is different from the known Au(i), Rh(iii)-catalyzed annulation reactions of salicylaldehydes and terminal alkynes.

  6. A coumarin-specific prenyltransferase catalyzes the crucial biosynthetic reaction for furanocoumarin formation in parsley.

    Science.gov (United States)

    Karamat, Fazeelat; Olry, Alexandre; Munakata, Ryosuke; Koeduka, Takao; Sugiyama, Akifumi; Paris, Cedric; Hehn, Alain; Bourgaud, Frédéric; Yazaki, Kazufumi

    2014-02-01

    Furanocoumarins constitute a sub-family of coumarin compounds with important defense properties against pathogens and insects, as well as allelopathic functions in plants. Furanocoumarins are divided into two sub-groups according to the alignment of the furan ring with the lactone structure: linear psoralen and angular angelicin derivatives. Determination of furanocoumarin type is based on the prenylation position of the common precursor of all furanocoumarins, umbelliferone, at C6 or C8, which gives rise to the psoralen or angelicin derivatives, respectively. Here, we identified a membrane-bound prenyltransferase PcPT from parsley (Petroselinum crispum), and characterized the properties of the gene product. PcPT expression in various parsley tissues is increased by UV irradiation, with a concomitant increase in furanocoumarin production. This enzyme has strict substrate specificity towards umbelliferone and dimethylallyl diphosphate, and a strong preference for the C6 position of the prenylated product (demethylsuberosin), leading to linear furanocoumarins. The C8-prenylated derivative (osthenol) is also formed, but to a much lesser extent. The PcPT protein is targeted to the plastids in planta. Introduction of this PcPT into the coumarin-producing plant Ruta graveolens showed increased consumption of endogenous umbelliferone. Expression of PcPT and a 4-coumaroyl CoA 2'-hydroxylase gene in Nicotiana benthamiana, which does not produce furanocoumarins, resulted in formation of demethylsuberosin, indicating that furanocoumarin production may be reconstructed by a metabolic engineering approach. The results demonstrate that a single prenyltransferase, such as PcPT, opens the pathway to linear furanocoumarins in parsley, but may also catalyze the synthesis of osthenol, the first intermediate committed to the angular furanocoumarin pathway, in other plants.

  7. Room temperature polymerization of alkyl isocyanates catalyzed by rare earth Schiff base complexes

    Institute of Scientific and Technical Information of China (English)

    YANG XiongFa; NI XuFeng; SHEN ZhiQuan

    2009-01-01

    The polymerization of alkyl isocyanates catalyzed by rare earth chloride salen complexes/triisobutyl aluminum (Ln(H_2salen)_2Cl_3·2C_2H_7OH/Al(i-Bu)_3) at room temperature was investigated.The influences of ligand structure,catalyst composition,polymerization temperature,polymerization time,the concentration of catalyst and monomer,and the polymerization solvent on the polymerization of isocyanates were studied.It was found that under the polymerization conditions,examined La(H_2salen_A)_2Cl_3·2C_(2-)H_7OH/Al(i-Bu)_3 (H_2salen_A=N,N'-disalicylideneethylene diamine) is a fairly high efficient catalyst for the polymerization of n-hexyl isocyanate (n-HexNCO) to prepare high molecular weight poly(n-hexyl isocyanate) (PHNCO) with narrower molecular weight distribution at room temperature.PHNCO could be prepared with yield of 74.0%,number-average molecular weight (M_n) of 40.20×10~4 and MWD of 1.79 under the following optimum conditions:[Al]/[La]=30 (molar ratio),[n-HexNCO]/[La]=100 (molar ratio),[n-HexNCO]=3.43 mol/L polymerization at 20℃ for 12 h in toluene.In the same polymerization conditions,poly (n-octyl isocyanate) (PONCO) with yield of 67.3%,and poly(n-butyl isocyanate) (PBNCO) with yield of 45.5%,could be prepared respectively.The kinetics of the polymerization of n-HexNCO was also investigated and found to be first-order with respect to both monomer and catalyst concentrations.

  8. Removal of SU-8 resists using hydrogen radicals generated by tungsten hot-wire catalyzer

    Science.gov (United States)

    Kono, Akihiko; Arai, Yu; Goto, Yousuke; Horibe, Hideo

    2012-03-01

    We investigated removal of chemically amplified negative-tone i-line resist SU-8 using hydrogen radicals, which was generated by the catalytic decomposition of H2/N2 mixed gas (H2:N2 = 10:90vol.%) using tungsten hot-wire catalyzer. SU-8 with exposure dose from 7 (Dg100×0.5) to 280mJ/cm2 (Dg100×20) were removed by hydrogen radicals without a residual layer. When the distance between the catalyzer and the substrate was 100mm, the catalyzer temperature was 2400°C, and the initial substrate temperature was 50°C, removal rate of SU-8 was 0.17μm/min independent of exposure dose to the SU-8. Finally, we obtained high removal rate for SU-8 (exposure dose = 14mJ/cm2 (Dg100)) of approximately 4μm/min when the distance between the catalyzer and the substrate was 20mm, the catalyzer temperature was 2400°C, and the initial substrate temperature was 165°C.

  9. [Degradation of nitrobenzene in aqueous solution by modified ceramic honeycomb-catalyzed ozonation].

    Science.gov (United States)

    Sun, Zhi-Zhong; Zhao, Lei; Ma, Jun

    2005-11-01

    Comparative experiments of modified ceramic honeycomb, ceramic honeycomb-catalyzed ozonation and ozonation alone were conducted with nitrobenzene as the model organic pollutant. It was found that the processes of modified ceramic honeycomb and ceramic honeycomb-catalyzed ozonation could increase the removal efficiency of nitrobenzene by 38.35% and 15.46%, respectively, compared with that achieved by ozonation alone. Under the conditions of this experiment, the degradation rate of modified ceramic honeycomb-catalyzed ozonation increased by 30.55% with the increase of amount of catalyst to 5 blocks. The degradation rate of three process all increased greatly with the increase of temperature and value of pH in the solution. But when raising the pH value of the solution to 10.00, the advantage of modified ceramic honeycomb-catalyzed ozonation processes lost. The experimental results indicate that in modified ceramic honeycomb-catalyzed ozonation, nitrobenzene is primarily oxidized by *OH free radical in aqueous solution. The adsorption of nitrobenzene is too limited to have any influence on the degradation efficiency of nitrobenzene. With the same total dosage of applied ozone, the multiple steps addition of ozone showed a much higher removal efficiency than that obtained by one step in three processes. Modified ceramic honeycomb had a relative longer lifetime.

  10. Enzyme-catalyzed reaction of voltammetric enzyme-linked immunoassay system based on OAP as substrate

    Institute of Scientific and Technical Information of China (English)

    张书圣; 陈洪渊; 焦奎

    1999-01-01

    The o-aminophenol (OAP)-H2O2-horseradish peroxidase (HRP) voltammetric enzyme-linked immunoassay new system has extremely high sensitivity. HRP can be measured with a detection limit of 6.0×10-(10) g/L and a linear range of 1.0×10-9—4.0×10-6 g/L. The pure product of H2O2 oxidizing OAP catalyzed by HRP was prepared with chemical method. The enzyme-catalyzed reaction has been investigated with electroanalytical chemistry, UV/Vis spectrum, IR spectrum, 13C NMR, 1H NMR, mass spectrum, elemental analysis, etc. Under the selected enzyme-catalyzed reaction conditions, the oxidation product of OAP with H2O2 catalyzed by HRP is 2-aminophe-noxazine-3-one. The processes of the enzyme-catalyzed reaction and the electroreduction of the product of the enzymecatalyzed reaction have been described.

  11. Nanostructured Ti-catalyzed MgH2 for hydrogen storage.

    Science.gov (United States)

    Shao, H; Felderhoff, M; Schüth, F; Weidenthaler, C

    2011-06-10

    Nanocrystalline Ti-catalyzed MgH(2) can be prepared by a homogeneously catalyzed synthesis method. Comprehensive characterization of this sample and measurements of hydrogen storage properties are discussed and compared to a commercial MgH(2) sample. The catalyzed MgH(2) nanocrystalline sample consists of two MgH(2) phases-a tetrahedral β-MgH(2) phase and an orthorhombic high-pressure modification γ-MgH(2). Transmission electron microscopy was used for the observation of the morphology of the samples and to confirm the nanostructure. N(2) adsorption measurement shows a BET surface area of 108 m(2) g(-1) of the nanostructured material. This sample exhibits a hydrogen desorption temperature more than 130 °C lower compared to commercial MgH(2). After desorption, the catalyzed nanocrystalline sample absorbs hydrogen 40 times faster than commercial MgH(2) at 300 °C. Both the Ti catalyst and the nanocrystalline structure with correspondingly high surface area are thought to play important roles in the improvement of hydrogen storage properties. The desorption enthalpy and entropy values of the catalyzed MgH(2) nanocrystalline sample are 77.7 kJ mol(-1) H(2) and 138.3 J K(-1) mol(-1) H(2), respectively. Thermodynamic properties do not change with the nanostructure.

  12. Revised Safety Code A2

    CERN Multimedia

    SC Secretariat

    2005-01-01

    Please note that the revised Safety Code A2 (Code A2 rev.) entitled "REPORTING OF ACCIDENTS AND NEAR MISSES" is available on the web at the following url: https://edms.cern.ch/document/335502/LAST_RELEASED Paper copies can also be obtained from the SC Unit Secretariat, e-mail: sc.secretariat@cern.ch SC Secretariat

  13. Horseradish peroxidase catalyzed free radical cannot free move in reaction solution

    Directory of Open Access Journals (Sweden)

    Cai Xialing

    2009-08-01

    Full Text Available Mechanism of Horseradish Peroxidase -catalyzed phenol compound oxidizing reaction is a radical polymerization. Many polymer preparation are also carry on through the radical polymerization mechanism We deduce if free radical produced by peroxidasecatalyzed phenol polymerization could apply on polymer preparation? Could the phenol–oxygen free radical leave off the peroxidase and catalyze other compounds polymerization? The free radical in phenol oxidation process was investigated in homogeneous reaction and in immobilized HRP catalyzed reaction. The results showed the free radical produced by peroxidase only move on the surface of enzyme, can’t free move in solution in both experiment. Evidence showed the phenol polymerization is enzyme reaction process, different from general chemistry free radical chain reaction.Keywords: Horseradish Peroxidase, free radical polymerization, mechanismReceived: 17 March 2008 / Received in revised form: 5 February 2009, Accepted: 31 April 2009 Published online: 14 May 2009

  14. Theoretical Studies on the Iodine-catalyzed Nucleophilic Addition of Acetone with Five-membered Heterocycles

    Institute of Scientific and Technical Information of China (English)

    WANG Yan-hua; LI Li; CHEN Xue-song

    2008-01-01

    The iodine-catalyzed nucleophilic addition reactions of pyrrole,furan,or thiophene with acetone were studied in gas and solvent by the density functional theory at the level of Lan12DZ*,It was seen that the halogen bond between iodine and carbonyl oxygen appeared to have an important catalytic effect on such reactions,and the first iodine molecule maximally diminished the barrier height by 41 kJ/mol,while the second iodine molecule could not improve such reactions largely,It was concluded that the C2-addition was generally more favorable than the C3-addition for the three heterocycles;however,iodine considerably more effectively catalyzed the C3-addition than the C2-addition for pyrrole,It was also revealed by PCM calculation that the iodine-catalyzed nucleophilic additions occurred more easily in solvent than in gas,which explained the experiment performed by Bandgar et al..

  15. Investigation of the effect of organic solvents on kinetic parameters in metal catalyzed reactions

    Directory of Open Access Journals (Sweden)

    GORDANA A. MILOVANOVIC

    2000-03-01

    Full Text Available The effects of acetone and acetonitrile on the kinetic parameters of azorubin S oxidation by hydrogen peroxide catalyzed by manganese(II, pyrocatechol violet oxidation by hydrogen peroxide catalyzed by copper(II, and carminic acid oxidation by hydrogen peroxide catalyzed by copper(II and activated by bifenox, were examined. It was established that the examined solvents exhibit various effects on the kinetic parameters of the above said reactions. In a11 instances a change in the solvent concentration effects both the anthalpy and the entropy contributions to the free activation energy during the transition of the system into the active state, as well as the constant of the active complex formed at this point.

  16. Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts

    Directory of Open Access Journals (Sweden)

    Kayla M. Fisher

    2016-06-01

    Full Text Available Metal-free transformations of organotrifluoroborates are advantageous since they avoid the use of frequently expensive and sensitive transition metals. Lewis acid-catalyzed reactions involving potassium trifluoroborate salts have emerged as an alternative to metal-catalyzed protocols. However, the drawbacks to these methods are that they rely on the generation of unstable boron dihalide species, thereby resulting in low functional group tolerance. Recently, we discovered that in the presence of a Brønsted acid, trifluoroborate salts react rapidly with in situ generated oxocarbenium ions. Here, we report Brønsted acid-catalyzed direct substitution of 2-ethoxytetrahydrofuran using potassium trifluoroborate salts. The reaction occurs when tetrafluoroboric acid is used as a catalyst to afford functionalized furans in moderate to excellent yields. A variety of alkenyl- and alkynyltrifluoroborate salts readily participate in this transformation.

  17. Enzyme catalyzed oxidative cross-linking of feruloylated pectic polysaccharides from sugar beet

    DEFF Research Database (Denmark)

    Abang Zaidel, Dayang Norulfairuz

    -linking and consequently the properties of the gels formed. The kinetics of oxidative gelation of SBP, taking place via enzyme catalyzed cross-linking of FA, was evaluated by small angle oscillatory measurements. The result indicates a significant difference between the SBP gels produced from the catalysis of HRP...... and laccase, that is, laccase catalysis produced stronger SBP gels albeit slower rates of gelation than the HRP catalysis. Statistically design experiment has been constructed to investigate the effect of several reaction factors which might influence the rates of gelation of SBP catalyzed by HRP or laccase......, particularly the pectin level, temperature, enzyme dosage, pH and, for HRP, the H2O2 concentration. The result reveals that these reaction factors could be tuned in order to adjust the enzyme catalyzed gelation and the properties of the gels produced. Moreover, positive correlation between the rates...

  18. Heterogeneous oxidation of cyclohexanone catalyzed by TS-1:Combined experimental and DFT studies

    Institute of Scientific and Technical Information of China (English)

    Changjiu Xia; Xingtian Shu; Long Ju; Yi Zhao; Hongyi Xu; Bin Zhu; Feifei Gao; Min Lin; Zhenyu Dai; Xiaodong Zou

    2015-01-01

    The reaction mechanism of the oxidation of cyclohexanone catalyzed by titanium silicate zeolite TS-1 using aqueous H2O2 as the oxidant was investigated by combining density function theory (DFT) calculations with experimental studies. DFT calculations showed that H2O2 was adsorbed and activated at the tetrahedral Ti sites. By taking into account the adsorption energy, molecular size, steric hindrance and structural information, a reaction mechanism of Baeyer-Villiger oxidation catalyzed by TS-1 that involves the activation of H2O2 was proposed. Experimental studies showed that the major products of cyclohexanone oxidation by H2O2 catalyzed by a hollow TS-1 zeolite wereε-carprolactone, 6-hydroxyhexanoic acid, and adipic acid. These products were analyzed by GC-MS and were in good agreement with the proposed mechanism. Our studies showed that the reaction mechanism on TS-1 zeolite was different from that on Sn-beta zeolite.

  19. Constitutive modeling of the viscoelastic and viscoplastic responses of metallocene catalyzed polypropylene

    DEFF Research Database (Denmark)

    Drozdov, Aleksey; Christiansen, Jesper de Claville; Sanporean, Catalina-Gabriela

    2012-01-01

    Purpose – The purpose of this paper is to perform experimental investigation and constitutive modeling of the viscoelastic and viscoplastic behavior of metallocene catalyzed polypropylene (mPP) with application to lifetime assessment under conditions of creep rupture. Design/methodology/approach ...... in long-term creep tests. Keywords Metallocene catalyzed polypropylene, Viscoelasticity, Viscoplasticity, Creep rupture, Constitutive modeling, Elastoplastic analysis, Viscosity, Creep, Physical properties of materials Paper type Research paper....../methodology/approach – Three series of experiments are conducted where the mechanical response of mPP is analyzed in tensile tests with various strain rates, relaxation tests with various strains, and creep tests with various stresses at room temperature. A constitutive model is derived for semicrystalline polymers under......Purpose – The purpose of this paper is to perform experimental investigation and constitutive modeling of the viscoelastic and viscoplastic behavior of metallocene catalyzed polypropylene (mPP) with application to lifetime assessment under conditions of creep rupture. Design...

  20. Iridium and ruthenium catalyzed syntheses, hydroborations, and metathesis reactions of alkenyl-decaboranes.

    Science.gov (United States)

    Chatterjee, Shahana; Carroll, Patrick J; Sneddon, Larry G

    2013-08-05

    The selective syntheses of new classes of 6,9-dialkenyl- and 6-alkenyl-decaboranes and 6-alkyl-9-alkenyl-decaboranes have been achieved via iridium and ruthenium catalyzed decaborane and 6-alkyl-decaborane alkyne-hydroborations. Reactions employing [Cp*IrCl2]2 and [RuCl2(p-cymene)]2 precatalysts gave β-E-alkenyl-decaboranes, while the corresponding reactions with [RuI2(p-cymene)]2 gave the α-alkenyl-decaborane isomers, with the differences in product selectivity suggesting quite different mechanistic steps for the catalysts. The alkenyl-decaboranes were easily converted to other useful derivatives, including coupled-cage and functionally substituted compounds, via iridium-catalyzed hydroborations and ruthenium-catalyzed homo and cross olefin-metathesis reactions.

  1. Iron-Catalyzed C-C Cross-Couplings Using Organometallics.

    Science.gov (United States)

    Guérinot, Amandine; Cossy, Janine

    2016-08-01

    Over the last decades, iron-catalyzed cross-couplings have emerged as an important tool for the formation of C-C bonds. A wide variety of alkenyl, aryl, and alkyl (pseudo)halides have been coupled to organometallic reagents, the most currently used being Grignard reagents. Particular attention has been devoted to the development of iron catalysts for the functionalization of alkyl halides that are generally challenging substrates in classical cross-couplings. The high functional group tolerance of iron-catalyzed cross-couplings has encouraged organic chemists to use them in the synthesis of bioactive compounds. Even if some points remain obscure, numerous studies have been carried out to investigate the mechanism of iron-catalyzed cross-coupling and several hypotheses have been proposed.

  2. Polymerization of o-Phenylenediamine Catalyzed by Hemeproteins Encapsulated in Reversed Micelle

    Institute of Scientific and Technical Information of China (English)

    YANG Yong; MAO Lu-yuan; LI Liu-zhu; LIU Xiao-guang; SHI Jun; CAO Shao-kui

    2004-01-01

    Hemeproteins encapsulated in reversed micelle formulated with di-2-ethylhexyl sulfosuccinate (AOT)was found to catalyze the polymerization of o-phenylenediamine (o-PDA) with hydrogen peroxide, whereas o-PDA catalyzed by hemeproteins dissolved in water could only form its trimers. As the nanostructural environment in reversed micelle acts as a certain orientation surrounding medium, it offers a strong electrostatic field that alters the reductive potential of Fe3+/Fe2+ (Em7) in the heme of hemeproteins and thus increases the catalytic activity of peroxidase accordingly. According to the results of UV-Vis, 1H NMR and FTIR, the polymer catalyzed by hemoglobin(Hb) in reversed micelle was presumed to be constructed of lines and trapeziforms alternatively.

  3. First Novozym 435 lipase-catalyzed Morita-Baylis-Hillman reaction in the presence of amides.

    Science.gov (United States)

    Tian, Xuemei; Zhang, Suoqin; Zheng, Liangyu

    2016-03-01

    The first Novozym 435 lipase-catalyzed Morita-Baylis-Hillman (MBH) reaction with amides as co-catalyst was realized. Results showed that neither Novozym 435 nor amide can independently catalyze the reaction. This co-catalytic system that used a catalytic amount of Novozym 435 with a corresponding amount of amide was established and optimized. The MBH reaction strongly depended on the structure of aldehyde substrate, amide co-catalyst, and reaction additives. The optimized reaction yield (43.4%) was achieved in the Novozym 435-catalyzed MBH reaction of 2, 4-dinitrobenzaldehyde and cyclohexenone with isonicotinamide as co-catalyst and β-cyclodextrin as additive only in 2 days. Although enantioselectivity of Novozym 435 was not found, the results were still significant because an MBH reaction using lipase as biocatalyst was realized for the first time.

  4. Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase.

    Science.gov (United States)

    Yang, Zhi-Yong; Moure, Vivian R; Dean, Dennis R; Seefeldt, Lance C

    2012-11-27

    A doubly substituted form of the nitrogenase MoFe protein (α-70(Val)(→Ala), α-195(His→Gln)) has the capacity to catalyze the reduction of carbon dioxide (CO(2)) to yield methane (CH(4)). Under optimized conditions, 1 nmol of the substituted MoFe protein catalyzes the formation of 21 nmol of CH(4) within 20 min. The catalytic rate depends on the partial pressure of CO(2) (or concentration of HCO(3)(-)) and the electron flux through nitrogenase. The doubly substituted MoFe protein also has the capacity to catalyze the unprecedented formation of propylene (H(2)C = CH-CH(3)) through the reductive coupling of CO(2) and acetylene (HC≡CH). In light of these observations, we suggest that an emerging understanding of the mechanistic features of nitrogenase could be relevant to the design of synthetic catalysts for CO(2) sequestration and formation of olefins.

  5. Rhodium-catalyzed acyloxy migration of propargylic esters in cycloadditions, inspiration from the recent "gold rush".

    Science.gov (United States)

    Shu, Xing-Zhong; Shu, Dongxu; Schienebeck, Casi M; Tang, Weiping

    2012-12-07

    Transition metal-catalyzed acyloxy migration of propargylic esters offers versatile entries to allene and vinyl carbene intermediates for various fascinating subsequent transformations. Most π-acidic metals (e.g. gold and platinum) are capable of facilitating these acyloxy migration events. However, very few of these processes involve redox chemistry, which are well-known for most other transition metals such as rhodium. The coupling of acyloxy migration of propargylic esters with oxidative addition, migratory insertion, and reductive elimination may lead to ample new opportunities for the design of new reactions. This tutorial review summarizes recent developments in Rh-catalyzed 1,3- and 1,2-acyloxy migration of propargylic esters in a number of cycloaddition reactions. Related Au- and Pt-catalyzed cycloadditions involving acyloxy migration are also discussed.

  6. Dechlorination of carbon tetrachloride by the catalyzed Fe-Cu process

    Institute of Scientific and Technical Information of China (English)

    XU Wen-ying; GAO Ting-yao

    2007-01-01

    The electrochemical reduction characteristics of carbon tetrachloride (CT) were investigated using cyclic voltammetry in this study. In addition, the difference in reduction mechanisms of CT between Master Builders' iron and the catalyzed Fe-Cu process was discussed. The results showed that CT was reduced directly on the surface of copper rather than by atomic hydrogen produced at the cathode in the catalyzed Fe-Cu process. The reduction was realized largely by atomic hydrogen in Master Builders' iron. The entire CT in 350 ml aqueous solution with 320 mg/L was reduced to trichloromethane and dichloromethane in 2.25 h when 100 g of scrap iron with Fe/Cu ratio of 10:1 (w/w) were used. Moreover, the reduction rate slowed with time. CT could be reduced at acidic, neutral and alkaline pH from solution by Fe-Cu bimetallic media, but the mechanisms were different. The degradation rate was not significantly influenced by pH in the catalyzed Fe-Cu process; in Master Builders' iron it clearly increased with decreasing pH. The kinetics of the reductions followed pseudo-first order in both cases. Furthermore, the reductions under acidic conditions proceeded faster than that under the neutral and alkaline conditions. The catalyzed Fe-Cu process was superior to Master Builders' iron in treating CT-containing water and this advantage was particularly noticeable under alkaline conditions. The reduction was investigated in the cathode (Cu) and anode (Fe) compartments respectively, the results showed that the direct reduction pathway played an important role in the reduction by the catalyzed Fe-Cu process. The catalyzed Fe-Cu process is of practical value.

  7. Kinetic Behavior of Aggregation-Exchange Growth Process with Catalyzed-Birth

    Institute of Scientific and Technical Information of China (English)

    HAN An-Jia; CHEN Yu; LIN Zhen-Quan; KE Jian-Hong

    2007-01-01

    We propose an aggregation model of a two-species system to mimic the growth of cities' population and assets,in which irreversible coagulation reactions and exchange reactions occur between any two aggregates of the same species,and the monomer-birth reactions of one species occur by the catalysis of the other species.In the case with population-catalyzed birth of assets,the rate kernel of an asset aggregate Bκ of size k grows to become an aggregate Bκ+ 1through a monomer-birth catalyzed by a population aggregate Aj of size j is J(k,j) = Jkjλ.And in mutually catalyzed birth model,the birth rate kernels of population and assets are H(k,j) = Hkjη and J(k,j) = Jkjλ,respectively.The kinetics of the system is investigated based on the mean-field theory.In the model of population-catalyzed birth of assets,the long-time asymptotic behavior of the assets aggregate size distribution obeys the conventional or modified scaling form.In mutually catalyzed birth system,the asymptotic behaviors of population and assets obey the conventional scaling form in the case ofη =λ= 0,and they obey the modified scalingform in the case of η = 0,λ= 1.In the case of η = λ = 1,the total mass of population aggregates and that of asset aggregates both grow much faster than those in population-catalyzed birth of assets model,and they approaches to infinite values in finite time.

  8. Biofuel-Promoted Polychlorinated Dibenzodioxin/furan Formation in an Iron-Catalyzed Diesel Particle Filter.

    Science.gov (United States)

    Heeb, Norbert V; Rey, Maria Dolores; Zennegg, Markus; Haag, Regula; Wichser, Adrian; Schmid, Peter; Seiler, Cornelia; Honegger, Peter; Zeyer, Kerstin; Mohn, Joachim; Bürki, Samuel; Zimmerli, Yan; Czerwinski, Jan; Mayer, Andreas

    2015-08-04

    Iron-catalyzed diesel particle filters (DPFs) are widely used for particle abatement. Active catalyst particles, so-called fuel-borne catalysts (FBCs), are formed in situ, in the engine, when combusting precursors, which were premixed with the fuel. The obtained iron oxide particles catalyze soot oxidation in filters. Iron-catalyzed DPFs are considered as safe with respect to their potential to form polychlorinated dibenzodioxins/furans (PCDD/Fs). We reported that a bimetallic potassium/iron FBC supported an intense PCDD/F formation in a DPF. Here, we discuss the impact of fatty acid methyl ester (FAME) biofuel on PCDD/F emissions. The iron-catalyzed DPF indeed supported a PCDD/F formation with biofuel but remained inactive with petroleum-derived diesel fuel. PCDD/F emissions (I-TEQ) increased 23-fold when comparing biofuel and diesel data. Emissions of 2,3,7,8-TCDD, the most toxic congener [toxicity equivalence factor (TEF) = 1.0], increased 90-fold, and those of 2,3,7,8-TCDF (TEF = 0.1) increased 170-fold. Congener patterns also changed, indicating a preferential formation of tetra- and penta-chlorodibenzofurans. Thus, an inactive iron-catalyzed DPF becomes active, supporting a PCDD/F formation, when operated with biofuel containing impurities of potassium. Alkali metals are inherent constituents of biofuels. According to the current European Union (EU) legislation, levels of 5 μg/g are accepted. We conclude that risks for a secondary PCDD/F formation in iron-catalyzed DPFs increase when combusting potassium-containing biofuels.

  9. Acid-catalyzed hydrogenation of olefins. A theoretical study of the HF- and H/sub 3/O/sup +/-catalyzed hydrogenation of ethylene

    Energy Technology Data Exchange (ETDEWEB)

    Siria, J.C.; Duran, M.; Lledos, A.; Bertran, J.

    1987-12-09

    The HF- and H/sub 3/O/sup +/-catalyzed hydrogenation of ethylene and the direct addition of molecular hydrogen to ethylene have been studied theoretically by means of ab initio MO calculations using different levels of theory. The main results are that catalysis by HF lowers the potential energy barrier to a large extent, while catalysis by H/sub 3/O/sup +/ diminishes dramatically the barrier for the reaction. Entropic contributions leave these results unchanged. The mechanisms of the two acid-catalyzed hydrogenations are somewhat different. While catalysis by HF exhibits bifunctional characteristics, catalysis by H/sub 3/O/sup +/ proceeds via an initial formation of a carbocation. It is shown that catalysis by strong acids may be an alternate way for olefin hydrogenation.

  10. Rh(III)-Catalyzed meta-C-H Olefination Directed by a Nitrile Template.

    Science.gov (United States)

    Xu, Hua-Jin; Lu, Yi; Farmer, Marcus E; Wang, Huai-Wei; Zhao, Dan; Kang, Yan-Shang; Sun, Wei-Yin; Yu, Jin-Quan

    2017-02-15

    A range of Rh(III)-catalyzed ortho-C-H functionalizations have been developed; however, extension of this reactivity to remote C-H functionalizations through large-ring rhodacyclic intermediates has yet to be demonstrated. Herein we report the first example of the use of a U-shaped nitrile template to direct Rh(III)-catalyzed remote meta-C-H activation via a postulated 12-membered macrocyclic intermediate. Because the ligands used for Rh(III) catalysts are significantly different from those of Pd(II) catalysts, this offers new opportunities for future development of ligand-promoted meta-C-H activation reactions.

  11. Lipase-catalyzed process for biodiesel production: protein engineering and lipase production.

    Science.gov (United States)

    Hwang, Hyun Tae; Qi, Feng; Yuan, Chongli; Zhao, Xuebing; Ramkrishna, Doraiswami; Liu, Dehua; Varma, Arvind

    2014-04-01

    Biodiesel is an environment-friendly and renewable fuel produced by transesterification of various feedstocks. Although the lipase-catalyzed biodiesel production has many advantages over the conventional alkali catalyzed process, its industrial applications have been limited by high-cost and low-stability of lipase enzymes. This review provides a general overview of the recent advances in lipase engineering, including both protein modification and production. Recent advances in biotechnology such as in protein engineering, recombinant methods and metabolic engineering have been employed but are yet to impact lipase engineering for cost-effective production of biodiesel. A summary of the current challenges and perspectives for potential solutions are also provided.

  12. Modeling Lipase-Catalyzed Biodiesel Production in [BMIM][PF6

    Directory of Open Access Journals (Sweden)

    JianJun Yang

    2016-01-01

    Full Text Available Lipase-catalyzed biodiesel production models in room temperature ionic liquids (RTILs reaction medium available in the literature are valid especially for mixing intensity. In this paper, a preliminary model is established in order to try to describe the lipase-catalyzed biodiesel production process in RTILs in a stirring type bioreactor. Mixing intensity and time delay were inspected for the reaction model in [BMIM][PF6] medium. As a result, this model is a good explanation for these actual reaction conditions in RTILs. The model prediction curves well describe the experimental data indicating this bioenzymatic reaction model is effective and reliable in certain conditions.

  13. The mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol

    Institute of Scientific and Technical Information of China (English)

    竹湘锋; 徐新华

    2004-01-01

    Fe (Ⅲ)-catalyzed ozonation yielded better degradation rate and extent of COD (Chemical Oxygen Demand) or oxalic acid as compared with oxidation by ozone alone. Two parameters with strong effects on the efficiency of ozonation are pH of the solution and the catalyst (Fe3+) dosage. The existence of a critical pH value determining the catalysis ofFe (Ⅲ) in acid conditions was observed in phenol and oxalic acid systems. The best efficiency of catalysis was obtained at a moderate concentration of the catalyst. A reasonable mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol was obtained based on the results and literature.

  14. FeCl3 -Catalyzed Ring-Closing Carbonyl-Olefin Metathesis.

    Science.gov (United States)

    Ma, Lina; Li, Wenjuan; Xi, Hui; Bai, Xiaohui; Ma, Enlu; Yan, Xiaoyu; Li, Zhiping

    2016-08-22

    Exploiting catalytic carbonyl-olefin metathesis is an ongoing challenge in organic synthesis. Reported herein is an FeCl3 -catalyzed ring-closing carbonyl-olefin metathesis. The protocol allows access to a range of carbo-/heterocyclic alkenes with good efficiency and excellent trans diastereoselectivity. The methodology presents one of the rare examples of catalytic ring-closing carbonyl-olefin metathesis. This process is proposed to take place by FeCl3 -catalyzed oxetane formation followed by retro-ring-opening to deliver metathesis products.

  15. ORGANIC CHEMISTRY. Iron-catalyzed intermolecular [2+2] cycloadditions of unactivated alkenes.

    Science.gov (United States)

    Hoyt, Jordan M; Schmidt, Valerie A; Tondreau, Aaron M; Chirik, Paul J

    2015-08-28

    Cycloadditions, such as the [4+2] Diels-Alder reaction to form six-membered rings, are among the most powerful and widely used methods in synthetic chemistry. The analogous [2+2] alkene cycloaddition to synthesize cyclobutanes is kinetically accessible by photochemical methods, but the substrate scope and functional group tolerance are limited. Here, we report iron-catalyzed intermolecular [2+2] cycloaddition of unactivated alkenes and cross cycloaddition of alkenes and dienes as regio- and stereoselective routes to cyclobutanes. Through rational ligand design, development of this base metal-catalyzed method expands the chemical space accessible from abundant hydrocarbon feedstocks.

  16. Additive-Free Pd-Catalyzed α-Allylation of Imine-Containing Heterocycles.

    Science.gov (United States)

    Kljajic, Marko; Puschnig, Johannes G; Weber, Hansjörg; Breinbauer, Rolf

    2017-01-06

    An additive-free Pd-catalyzed α-allylation of different imino-group-ontaining heterocycles is reported. The activation of α-CH pronucleophiles (pKa (DMSO) > 25) occurs without the addition of strong bases or Lewis acids using only the Pd/Xantphos catalyst system. The reaction scope has been studied for various 5- and 6-membered nitrogen-containing heterocycles (yields up to 96%). Mechanistic investigations suggest an initial allylation of the imine-N followed by a Pd-catalyzed formal aza-Claisen rearrangement.

  17. Cu-catalyzed trifluoromethylation of aryl iodides with trifluoromethylzinc reagent prepared in situ from trifluoromethyl iodide

    Directory of Open Access Journals (Sweden)

    Yuzo Nakamura

    2013-11-01

    Full Text Available The trifluoromethylation of aryl iodides catalyzed by copper(I salt with trifluoromethylzinc reagent prepared in situ from trifluoromethyl iodide and Zn dust was accomplished. The catalytic reactions proceeded under mild reaction conditions, providing the corresponding aromatic trifluoromethylated products in moderate to high yields. The advantage of this method is that additives such as metal fluoride (MF, which are indispensable to activate silyl groups for transmetallation in the corresponding reactions catalyzed by copper salt by using the Ruppert–Prakash reagents (CF3SiR3, are not required.

  18. Metal-catalyzed decaborane-alkyne hydroboration reactions: efficient routes to alkenyldecaboranes.

    Science.gov (United States)

    Chatterjee, Shahana; Carroll, Patrick J; Sneddon, Larry G

    2010-04-05

    Transition-metal-catalyzed decaborane-alkyne hydroboration reactions have been developed that provide high-yield routes to the previously unknown di- and monoalkenyldecaboranes. These alkenyl derivatives should be easily modified starting materials for many biomedical and/or materials applications. Unusual catalyst product selectivity was observed that suggests quite different mechanistic steps, with the reactions catalyzed by the [RuCl(2)(p-cymene)](2) and [Cp*IrCl(2)](2) complexes giving the beta-E alkenyldecaboranes and the corresponding reactions with the [RuI(2)(p-cymene)](2) complex giving the alpha-alkenyldecaborane isomers.

  19. Glycerol Dehydration to Acrolein Catalyzed by ZSM‐5 Zeolite in Supercritical Carbon Dioxide Medium

    Science.gov (United States)

    Zou, Bin; Ren, Shoujie

    2016-01-01

    Abstract Supercritical carbon dioxide (SC‐CO2) has been used for the first time as a reaction medium for the dehydration of glycerol to acrolein catalyzed by a solid acid. Unprecedented catalyst stability over 528 hours of time‐on‐stream was achieved and the rate of coke deposition on the zeolite catalyst was the lowest among extensive previous studies, showing potential for industrial application. Coking pathways in SC‐CO2 were also elucidated for future development. The results have potential implications for other dehydration reactions catalyzed by solid acids. PMID:27796088

  20. Synthesis of Fluoroalkoxy Substituted Arylboronic Esters by Iridium-Catalyzed Aromatic C–H Borylation

    KAUST Repository

    Batool, Farhat

    2015-08-17

    The preparation of fluoroalkoxy arylboronic esters by iridium-catalyzed aromatic C–H borylation is described. The fluoroalkoxy groups employed include trifluoromethoxy, difluoromethoxy, 1,1,2,2-tetrafluoroethoxy, and 2,2-difluoro-1,3-benzodioxole. The borylation reactions were carried out neat without the use of a glovebox or Schlenk line. The regioselectivities available through the iridium-catalyzed C–H borylation are complementary to those obtained by the electrophilic aromatic substitution reactions of fluoroalkoxy arenes. Fluoroalkoxy arylboronic esters can serve as versatile building blocks.

  1. Kinetics of enzyme-catalyzed cross-linking of feruloylated arabinan from sugar beet

    DEFF Research Database (Denmark)

    Abang Zaidel, Dayang Norulfairuz; Arnous, Anis; Holck, Jesper

    2011-01-01

    the kinetics of HRP catalyzed cross-linking of FA esterified to α-(1,5)-linked arabinans are affected by the length of the arabinan chains carrying the feruloyl substitutions. The kinetics of the HRP-catalyzed cross-linking of four sets of arabinan samples from sugar beet pulp, having different molecular...... weights and hence different degrees of polymerization, were monitored by the disappearance of FA absorbance at 316 nm. MALDI-TOF/TOF-MS analysis confirmed that the sugar beet arabinans were feruloyl-substituted, and HPLC analysis verified that the amounts of diFAs increased when FA levels decreased...

  2. Monitoring lipase-catalyzed butterfat interesterification with rapesee oil by Fourier transform near-infrared spectroscopy

    DEFF Research Database (Denmark)

    Zhang, Hong; Mu, Huiling; Xu, Xuebing

    2006-01-01

    This work demonstrates the application of FT-NIR spectroscopy to monitor the enzymatic interesterification process for butterfat modification. The reactions were catalyzed by Lipozyme TL IM at 70 C for the blend of butterfat/rapeseed oil (70/30, w/w) in a packed-bed reactor. The blend and intere......This work demonstrates the application of FT-NIR spectroscopy to monitor the enzymatic interesterification process for butterfat modification. The reactions were catalyzed by Lipozyme TL IM at 70 C for the blend of butterfat/rapeseed oil (70/30, w/w) in a packed-bed reactor. The blend...

  3. Enrichment of lecithin with n-3 fatty acids by acidolysis using immobilized phospholipase A1

    Directory of Open Access Journals (Sweden)

    Hill, Jr, Charles G.

    2008-12-01

    Full Text Available A commercial phospholipase A1 (Lecitase® Ultra was immobilized by physical adsorption on Duolite® and then used to mediate the incorporation of omega-3 fatty acids into lecithin. Adsorption isotherms showed that 12 h of contact were sufficient to deposit most of the enzyme onto the carrier. A pH of 7 and 50°C were the best conditions for adsorption. Reaction mixtures consisting of lecithin and a saponified fish oil concentrate (78.4 mol % EPA+DPA+DHA were prepared at molar ratios ranging from 1:2 to 1:10. Typically 2 g of total substrates and 200 mg of enzyme preparation were employed in batch reactor trials. The fastest reaction rates were observed when a substrate mole ratio of 1:8 (lecithin:total fatty acids was employed. Use of the enzyme preparation dried at pH 8 and reaction temperatures of 50 and 60°C produced the greatest extent of incorporation of the indicated n-3 fatty acids into the phospholipid after 24h of reaction.Una preparación comercial de fosfolipasa A1 (Lecitase® Ultra fue inmovilizada por adsorción sobre Duolite® y empleada para catalizar la incorporación de ácidos grasos n-3 en lecitina. Las isotermas de adsorción mostraron que en 12 horas de contacto se depositó la mayor cantidad de enzima sobre el soporte. Las mejores condiciones para la adsorción se encontraron a un valor de pH de 7 y 50°C. Las mezclas de reacción consistieron en lecitina y un saponificado de concentrado de aceite de pescado (78.4 mol % EPA+DPA+DHA a relaciones molares de 1:2 a 1:10. Una mezcla de reacción típica consistió de 2 g de sustratos y 200 mg del preparado enzimático en un reactor en lotes. Las velocidades de reacción mas altas se encontraron cuando se empleó una relación molar de sustratos de 1:8 (lecitina:ácidos grasos totales. El preparado enzimático secado a pH de 8.0 a 50 o 60°C produjo las más altas incorporaciones de ácidos grasos n-3 en el fosfolípido después de 24 h de reacción.

  4. PYROLYTIC PRODUCTS FROM RICE STRAW AND ENZYMATIC/MILD ACIDOLYSIS LIGNIN (EMAL

    Directory of Open Access Journals (Sweden)

    Rui Lou

    2010-08-01

    Full Text Available A pyrolysis tube furnace system was designed to assess the impact of different components on pyrolysis characteristics under nitrogen atmosphere, and pyrolysis temperature (400 to 900oC as important factors acting on the samples during pyrolysis. The obtained pyrolysate was classified into three groups, i.e. the condensed liquid product (bio-oil, solid product (bio-char, and light gas. Gas chromatography (GC was used to analyze ingredients of the light gas released during pyrolysis, and a gas chromatography/mass spectrometer (GC/MS was used to analyze bio-oil. The results revealed that the volatiles from rice straw pyrolysis exceeded that from lignin at temperatures below 700oC as a result of the higher char generation from lignin pyrolysis. With an increase of pyrolysis temperature, the yield of char decreased and light gas persistently increased, and the yield of bio-tar was maximized at 500oC. In the gas product, H2, CO, CO2 and some light hydrocarbons (CH4, C2H4 and C2H6 could be found, and H2 and CO were abundant. Compounds of bio-oil derived from lignin were simple and consisted of aromatic hydrocarbons, chain hydrocarbon, monoaromatics, and a minor amount of ketones. Phenolic compounds, which comprised 50 to 60%, can be converted easily to obtain high-value chemicals and high quality biofuels.

  5. Reactivity and Chemoselectivity of Allenes in Rh(I)-Catalyzed Intermolecular (5 + 2) Cycloadditions with Vinylcyclopropanes: Allene-Mediated Rhodacycle Formation Can Poison Rh(I)-Catalyzed Cycloadditions

    Science.gov (United States)

    2015-01-01

    Allenes are important 2π building blocks in organic synthesis and engage as 2-carbon components in many metal-catalyzed reactions. Wender and co-workers discovered that methyl substituents on the terminal allene double bond counterintuitively change the reactivities of allenes in [Rh(CO)2Cl]2-catalyzed intermolecular (5 + 2) cycloadditions with vinylcyclopropanes (VCPs). More sterically encumbered allenes afford higher cycloadduct yields, and such effects are also observed in other Rh(I)-catalyzed intermolecular cycloadditions. Through density functional theory calculations (B3LYP and M06) and experiment, we explored this enigmatic reactivity and selectivity of allenes in [Rh(CO)2Cl]2-catalyzed intermolecular (5 + 2) cycloadditions with VCPs. The apparent low reactivity of terminally unsubstituted allenes is associated with a competing allene dimerization that irreversibly sequesters rhodium. With terminally substituted allenes, steric repulsion between the terminal substituents significantly increases the barrier of allene dimerization while the barrier of the (5 + 2) cycloaddition is not affected, and thus the cycloaddition prevails. Computation has also revealed the origin of chemoselectivity in (5 + 2) cycloadditions with allene-ynes. Although simple allene and acetylene have similar reaction barriers, intermolecular (5 + 2) cycloadditions of allene-ynes occur exclusively at the terminal allene double bond. The terminal double bond is more reactive due to the enhanced d−π* backdonation. At the same time, insertion of the internal double bond of an allene-yne has a higher barrier as it would break π conjugation. Substituted alkynes are more difficult to insert compared with acetylene, because of the steric repulsion from the additional substituents. This leads to the greater reactivity of the allene double bond relative to the alkynyl group in allene-ynes. PMID:25379606

  6. A 11-Steps Total Synthesis of Magellanine through a Gold(I)-Catalyzed Dehydro Diels-Alder Reaction.

    Science.gov (United States)

    McGee, Philippe; Bétournay, Geneviève; Barabé, Francis; Barriault, Louis

    2017-01-12

    We have developed an innovative strategy for the formation of angular carbocycles via a gold(I)-catalyzed dehydro Diels-Alder reaction. This transformation provides rapid access to a variety of complex angular cores in excellent diastereoselectivities and high yields. The usefulness of this Au(I) -catalyzed cycloaddition was further demonstrated by accomplishing a 11-steps total synthesis of (±)-magellanine.

  7. Redox-Neutral Rh(III)-Catalyzed Olefination of Carboxamides with Trifluoromethyl Allylic Carbonate.

    Science.gov (United States)

    Park, Jihye; Han, Sangil; Jeon, Mijin; Mishra, Neeraj Kumar; Lee, Seok-Yong; Lee, Jong Suk; Kwak, Jong Hwan; Um, Sung Hee; Kim, In Su

    2016-11-18

    The rhodium(III)-catalyzed olefination of various carboxamides with α-CF3-substituted allylic carbonate is described. This reaction provides direct access to linear CF3-allyl frameworks with complete trans-selectivity. In particular, a rhodium catalyst provided Heck-type γ-CF3-allylation products via the β-O-elimination of rhodacycle intermediate and subsequent olefin migration process.

  8. Rh(III-catalyzed directed C–H bond amidation of ferrocenes with isocyanates

    Directory of Open Access Journals (Sweden)

    Satoshi Takebayashi

    2012-10-01

    Full Text Available [RhCp*(OAc2(H2O] [Cp* = pentamethylcyclopentadienyl] catalyzed the C–H bond amidation of ferrocenes possessing directing groups with isocyanates in the presence of 2 equiv/Rh of HBF4·OEt2. A variety of disubstituted ferrocenes were prepared in high yields, or excellent diastereoselectivities.

  9. MINERALIZATION OF A SORBED POLYCYCLIC AROMATIC HYDROCARBON IN TWO SOILS USING CATALYZED HYDROGEN PEROXIDE. (R826163)

    Science.gov (United States)

    Hydrogen peroxide (H2O2) catalyzed by soluble iron or naturally occurring soil minerals, (i.e., modified Fenton's reagent) was investigated as a basis for mineralizing sorbed and NAPL-phase benzo[a]pyrene (BaP), a hydrophobic and toxic polycyclic a...

  10. Synthesis of a Crushed Fullerene C60H24 through Sixfold Palladium-Catalyzed Arylation.

    Science.gov (United States)

    Dorel, Ruth; de Mendoza, Paula; Calleja, Pilar; Pascual, Sergio; González-Cantalapiedra, Esther; Cabello, Noemí; Echavarren, Antonio M

    2016-07-01

    The synthesis of a new C3v -symmetric crushed fullerene C60H24 (5) has been accomplished in three steps from truxene through sixfold palladium-catalyzed intramolecular arylation of a syn-trialkylated truxene precursor. Laser irradiation of 5 induces cyclodehydrogenation processes that result in the formation of C60, as detected by LDI-MS.

  11. Synthesis of a Crushed Fullerene C60H24 through Sixfold Palladium‐Catalyzed Arylation

    Science.gov (United States)

    Dorel, Ruth; de Mendoza, Paula; Calleja, Pilar; Pascual, Sergio; González‐Cantalapiedra, Esther; Cabello, Noemí

    2016-01-01

    The synthesis of a new C 3v‐symmetric crushed fullerene C60H24 (5) has been accomplished in three steps from truxene through sixfold palladium‐catalyzed intramolecular arylation of a syn‐trialkylated truxene precursor. Laser irradiation of 5 induces cyclodehydrogenation processes that result in the formation of C60, as detected by LDI‐MS. PMID:27774038

  12. Kinetic Behavior of Exchange-Driven Growth with Catalyzed-Birth Processes

    Institute of Scientific and Technical Information of China (English)

    WANG Hai-Feng; LIN Zhen-Quan; KONG Xiang-Mu

    2006-01-01

    Two catalyzed-birth models of n-species (n≥2) aggregates with exchange-driven growth processes are proposed and compared. In the first one, the exchange reaction occurs between any two aggregates Amk and Amj of the same species with the rate kernels Km (k,j)=Kmkj (m=1, 2,..., n, n≥2), and aggregates of An species catalyze a monomer-birth of Al species (l=1,2,..., n-1) with the catalysis rate kernel Jl(k,j)=Jlkjυ. The kinetic behaviors are investigated by means of the mean-field theory. We find that the evolution behavior of aggregate-size distribution alk(t) of Al species depends crucially on the value of the catalysis rate parameter v: (i) alk(t) obeys the conventional scaling law in the case of υ≤0, (ii) alk (t) satisfies a modified scaling form in the case of υ>0. In the second model,the mechanism of monomer-birth of An-species catalyzed by Al species is added on the basis of the first model, that is,the aggregates of Al and An species catalyze each other to cause monomer-birth. The kinetic behaviors of Al and Anspecies are found to fall into two categories for the different υ: (i) growth obeying conventional scaling form with υ≤0,(ii) gelling at finite time withυ>0.

  13. Palladium-Catalyzed Carbonylation of Primary Amines in Supercritical Carbon Dioxide

    Institute of Scientific and Technical Information of China (English)

    李金恒; 江焕峰; 陈鸣才

    2001-01-01

    The chemoselectity of the palladimm-catalyzed carbonylation of amines was affected by the addition of MeOH in supercritical carbon dioxide. The results show different selectivity in supercritical carbon dioxide CO2(sc) from that in alcohol.Methyl carbamate and its derivatives were obtained in high yields in CO2(sc).

  14. Palladium-catalyzed homo-coupling of boronic acids with supported reagents in supercritical carbon dioxide

    Institute of Scientific and Technical Information of China (English)

    Lei Zhou; Qiu Xiang Xu; Huan Feng Jiang

    2007-01-01

    Palladium-catalyzed homo-coupling of arylboronic acids could proceed smoothly with a commercially available resin functionlised by phosphino or amino group as the ligand in supercritical carbon dioxide thereby offering a simple and efficient protocol for the synthesis of symmetrical bi-aryl molecules and their higher homologues.

  15. Organocatalytic Asymmetric α-Chlorination of 1,3-Dicarbonyl Compounds Catalyzed by 2-Aminobenzimidazole Derivatives

    Directory of Open Access Journals (Sweden)

    Daniel Serrano Sánchez

    2016-01-01

    Full Text Available Bifunctional chiral 2-aminobenzimidazole derivatives 1 and 2 catalyze the enantioselective stereodivergent α-chlorination of β-ketoesters and 1,3-diketone derivatives with up to 50% ee using N-chlorosuccinimide (NCS or 2,3,4,4,5,6-hexachloro-2,5-cyclohexadien-1-one as electrophilic chlorine sources.

  16. A General and Efficient CuBr2-Catalyzed N-Arylation of Secondary Acyclic Amides

    Institute of Scientific and Technical Information of China (English)

    王满刚; 于华; 尤心稳; 吴军; 商志才

    2012-01-01

    A general and efficient Cu(II)-catalyzed cross-coupling method is reported for the preparation of acyclic tertiary amides. Generally moderate to excellent yields and functional group tolerance were obtained with secondary acyclic amides and aryl halides as substrates in toluene.

  17. Ammonium Chloride Promoted Palladium-Catalyzed Ullmann Coupling of Aryl Bromide

    Institute of Scientific and Technical Information of China (English)

    李金恒; 梁云; 刘文杰; 唐石; 谢叶香

    2004-01-01

    In water, ammonium chloride was found to promote palladium-catalyzed Ullmann coupling reactions of aryl bromides. In the presence of Pd/C, zinc, NH4Cl, and water, coupling of various aryl bromides was carried out smoothly to afford the corresponding homocoupling products in moderate yields.

  18. Synthesis of substituted benzoxazoles by the iron(Ⅲ)-catalyzed aerobic oxidation process

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The FeCl3-catalyzed aerobic oxidation process for the synthesis of benzoxazoles,benzothiazole and benzimidazole has been discovered.This method has proved to be effective to a wide range of substrates,and it has been applied for the synthesis of JTP-426467.

  19. The Isomerization of (-)-Menthone to (+)-Isomenthone Catalyzed by an Ion-Exchange Resin

    Science.gov (United States)

    Ginzburg, Aurora L.; Baca, Nicholas A.; Hampton, Philip D.

    2014-01-01

    A traditional organic chemistry laboratory experiment involves the acid-catalyzed isomerization of (-)-menthone to (+)-isomenthone. This experiment generates large quantities of organic and aqueous waste, and only allows the final ratio of isomers to be determined. A "green" modification has been developed that replaces the mineral acid…

  20. A Step into an eco-Compatible Future: Iron- and Cobalt-catalyzed Borrowing Hydrogen Transformation.

    Science.gov (United States)

    Quintard, Adrien; Rodriguez, Jean

    2016-01-01

    Living on borrowed hydrogen: Recent developments in iron- and cobalt-catalyzed borrowing hydrogen have shown that economically reliable catalysts can be used in this type of waste-free reactions. By using well-defined inexpensive catalysts, known reactions can now be run efficiently without the necessary use of noble metals; however, in addition new types of reactivity can also be discovered.

  1. N-heterocyclic carbene-catalyzed internal redox reaction of alkynals: an efficient synthesis of allenoates.

    Science.gov (United States)

    Zhao, Yu-Ming; Tam, Yik; Wang, Yu-Jie; Li, Zigang; Sun, Jianwei

    2012-03-16

    An efficient N-heterocyclic carbene (NHC)-catalyzed internal redox reaction of alkynals that bear a γ leaving group has been developed. This process provides a new access to a range of allenoates in good yields. Preliminary results demonstrate that the enantioselective variant can also be achieved.

  2. Experimental study on oxidative decomposition of nitrobenzene in aqueous solution by honeycomb ceramic-catalyzed ozonation

    Institute of Scientific and Technical Information of China (English)

    Lei ZHAO; Jun MA; Zhizhong SUN; Zhengqian LIU; Yixin YANG

    2008-01-01

    The ozonation of nitrobenzene in aqueous solu-tion was carried out in a semi-batch reactor to investigate the degradation efficiency, the effect factors, and the reaction mechanism, where honeycomb ceramic was used as a cata-lyst. The presence of honeycomb ceramic could improve the degradation rate of nitrobenzene by 15.46% compared to the results ofozonation alone. Under the conditions of this exper-iment, the degradation rate of honeycomb ceramic-catalyzed ozonation increased by 12.94% with the increase of the amount of catalyst from 1 to 5 blocks. The degradation rates all increased greatly with the increase of temperature and pH of the solution in the processes of honeycomb ceramic-catalyzed ozonation and ozonation alone. But, when the pH of the solution increased to 9.50, the advantage of the honey-comb ceramic-catalyzed ozonation process would be lost. The experimental findings indicated that in the processes of ozonation alone and honeycomb ceramic-catalyzed ozona-tion, nitrobenzene was primarily oxidized by·OH free radical in aqueous solution. The adsorption of nitrobenzene was too limited to have an important influence on the degradation rate of nitrobenzene. With the same total dosage of applied ozone, the multiple step addition of ozone showed much higher removal efficiency than that obtained by one step in the two processes.

  3. Optimization of H2SO4-catalyzed hydrothermal pretreatment of rapeseed straw for bioconversion to ethanol

    DEFF Research Database (Denmark)

    Xuebin, Lu; Zhang, Y.; Angelidaki, Irini

    2009-01-01

    A central composite design of response surface method was used to optimize H2SO4-catalyzed hydrothermal pretreatment of rapeseed straw, in respect to acid concentration (0.5-2%), treatment time (5-20 min) and solid content (10-20%) at 180 degrees C. Enzymatic hydrolysis and fermentation were also...

  4. Multitechnique approach to reveal the mechanism of copper(II)-catalyzed arylation reactions

    NARCIS (Netherlands)

    Tromp, M.; van Strijdonck, G.P.F.; van Berkel, S.S.; van den Hoogenband, A.; Feiters, M.C.; de Bruin, B.; Fiddy, S.G.; van der Eerden, A.M.J.; van Bokhoven, J.A.; van Leeuwen, P.W.N.M.; Koningsberger, D.C.

    2010-01-01

    Multiple in situ and time-resolved spectroscopic techniques (EDXAFS, UV−vis, EPR, and NMR), with a focus on simultaneously acquired EDXAFS and time-resolved UV−vis, are described to reveal detailed structural and electronic information on reaction intermediates of an important Cu(II)-catalyzed N-ary

  5. Palladium Catalyzed Suzuki Cross-coupling Reaction in Molten Tetra-n-butylammonium Bromide

    Institute of Scientific and Technical Information of China (English)

    ZOU, Yue(邹岳); WANG, Quan-Rui(王全瑞); TAO, Feng-Gang(陶凤岗); DING, Zong-Biao(丁宗彪)

    2004-01-01

    A practical procedure for palladium catalyzed Suzuki cross-coupling reaction of arylboronic acids with aryl halides, including aryl chlorides in molten tetra-n-butylammonium bromide (TBAB) was developed. The reaction exhibits high efficiency and functional group tolerance. The recovery of the catalyst and molten n-Bu4NBr was also investigated.

  6. Rationalizing Ring-Size Selectivity in Intramolecular Pd-Catalyzed Allylations of Resonance-Stabilized Carbanions

    DEFF Research Database (Denmark)

    Norrby, Per-Ola; Mader, Mary M.; Vitale, Maxime

    2003-01-01

    Computational methods were applied to the Pd-catalyzed intramolecular allylations of resonance-stabilized carbanions obtained from amide and ketone substrates, with the aim of rationalizing the endo- vs. exo-selectivity in the cyclizations. In addition, ester substrates were prepared and subjecte...

  7. Iridium‐Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols with the Liberation of Syngas

    DEFF Research Database (Denmark)

    Olsen, Esben Paul Krogh; Madsen, Robert

    2012-01-01

    to excellent yields. Ethers, esters, imides, and aryl halides are stable under the reaction conditions, whereas olefins are partially saturated. The reaction is believed to proceed by two consecutive organometallic transformations that are catalyzed by the same iridium(I)–BINAP species. First, dehydrogenation...

  8. Enantioselective Conjugate Addition of Grignard Reagents to Enones Catalyzed by Chiral Zinc(II) Complexes

    NARCIS (Netherlands)

    Jansen, Johan F.G.A.; Feringa, Bernard

    1990-01-01

    Various chiral zinc(II) complexes catalyze the asymmetric 1,4-addition of Grignard reagents to α,β-unsaturated ketones with high chemoselectivities (yields of 1,4-adducts, 83-99%), high regioselectivities (1,4/1,2 ratios up to 499) and modest enantioselectivities (ee up to 33%). A study of several f

  9. ESR ST study of hydroxyl radical generation in wet peroxide system catalyzed by heterogeneous ruthenium

    NARCIS (Netherlands)

    Rokhina, E.V.; Golovina, E.A.; As, van H.; Virkutyte, J.

    2009-01-01

    Ru-based catalysts gained popularity because of their applicability for a variety of processes, including carbon monoxide oxidation, wet air catalytic oxidation and wastewater treatment. The focus of a current study was generation of hydroxyl radicals in the wet peroxide system catalyzed by heteroge

  10. Monitoring the Hydrolysis of Olive Oil Catalyzed by Lipase via Acid Value Detection

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Hydrolysis of olive oil catalyzed by Candida lipolytica lipase was investigated. The relative concentration of the components in the product was determined by using high performance liquid chromatography(HPLC). Furthermore, a novel rapid method to detect the hydrolytic process of olive oil was developed based on the relationship between the acid value and the relative concentration of the different components.

  11. Diastereoselective Hydrogenation and Kinetic Resolution of Imines Using Rhodium/Diphosphine Catalyzed Hydrogenation.

    NARCIS (Netherlands)

    Lensink, Cornelis; Vries, Johannes G. de

    1993-01-01

    Kinetic resolution of racemic α-methylbenzyl amine can be achieved with 98% ee. of the remaining amine at 70% conversion using the Rhodium/2S,4S-BDPP catalyzed asymmetric hydrogenation of imines. The same catalyst will hydrogenate optically pure α-methylbenzyl amines with a diastereoselectivity of u

  12. Copper-Catalyzed SN2'-Selective Allylic Substitution Reaction of gem-Diborylalkanes.

    Science.gov (United States)

    Zhang, Zhen-Qi; Zhang, Ben; Lu, Xi; Liu, Jing-Hui; Lu, Xiao-Yu; Xiao, Bin; Fu, Yao

    2016-03-04

    A Cu/(NHC)-catalyzed SN2'-selective substitution reaction of allylic electrophiles with gem-diborylalkanes is reported. Different substituted gem-diborylalkanes and allylic electrophiles can be employed in this reaction, and various synthetic valuable functional groups can be tolerated. The asymmetric version of this reaction was initially researched with chiral N-heterocyclic carbene (NHC) ligands.

  13. Gold(III)-catalyzed three-component coupling reaction (TCC) selective toward furans.

    Science.gov (United States)

    Li, Jian; Liu, Li; Ding, Dong; Sun, Jiangtao; Ji, Yangxuan; Dong, Jialing

    2013-06-01

    An efficient three-component coupling reaction toward a variety of furan derivatives has been developed. This cascade transformation proceeds via the gold-catalyzed coupling reaction of phenylglyoxal derivatives, secondary amines, and terminal alkynes, under the reaction conditions, that undergoes cyclization into the furan core.

  14. Fe-Catalyzed Olefin Hydroamination with Diazo Compounds for Hydrazone Synthesis.

    Science.gov (United States)

    Zheng, Jing; Qi, Jifeng; Cui, Sunliang

    2016-01-01

    A novel Fe-catalyzed olefin hydroamination with diazo compounds for accessing hydrazones has been developed. Diazo compounds are used as radical acceptors and can be trapped by the in situ generated alkyl radical toward C-N bond formation. The reaction conditions are mild, and the substrate scope is broad. Additionally, this hydroamination protocol is applicable for intramolecular reactions to construct diverse heterocycles.

  15. Mechanistic investigation of the gold-catalyzed aerobic oxidation of alcohols

    DEFF Research Database (Denmark)

    Fristrup, Peter; Johansen, Louise Bahn; Christensen, Claus Hviid

    2008-01-01

    The mechanism for the gold-catalyzed aerobic oxidation of alcohols was studied using a series of para-substituted benzyl alcohols (Hammett methodology). The competition experiments clearly show that the rate-determining step of the reaction involves the generation of a partial positive charge in ...

  16. Catalyzing Mass Production of Solar Photovoltaic Cells Using University Driven Green Purchasing

    Science.gov (United States)

    Pearce, Joshua M.

    2006-01-01

    Purpose: The purpose of this paper is to explore the use of the purchase power of the higher education system to catalyze the economy of scale necessary to ensure market competitiveness for solar photovoltaic electricity. Design/methodology/approach: The approach used here was to first determine the demand necessary to construct "Solar City…

  17. Synthesis of quinolones by nickel-catalyzed cycloaddition via elimination of nitrile.

    Science.gov (United States)

    Nakai, Kenichiro; Kurahashi, Takuya; Matsubara, Seijiro

    2013-02-15

    Substituted quinolones were efficiently synthesized via the nickel-catalyzed cycloaddition of o-cyanophenylbenzamide derivatives with alkynes. The reaction involves elimination of a nitrile group by cleavage of the two independent aryl-cyano and aryl-carbonyl C-C bonds of the amides.

  18. EVALUATION OF THE FULL-SCALE BASE CATALYZED DECOMPOSITION PROCESS (BCDP) UNIT LOCATED IN GUAM

    Science.gov (United States)

    This report summarizes performance data collected in February 1997 on the removal of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) from soil fed to a first-stage rotary kiln reactor of the Base Catalyzed Dec...

  19. Mechanistic study on the ruthenium-catalyzed direct amination of alcohols

    NARCIS (Netherlands)

    Pingen, Dennis; Lutz, Martin; Vogt, Dieter

    2014-01-01

    The Ru-catalyzed direct amination of alcohols with ammonia was investigated for the RuHCl(CO)(PPh3)3/Xantphos system in order to gain mechanistic insight. For several Ru(II) precursor complexes the influence of different additives on catalytic performance was investigated. NMR studies revealed that

  20. Experimental and Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols

    DEFF Research Database (Denmark)

    Olsen, Esben Paul Krogh; Singh, Thishana; Harris, Pernille;

    2015-01-01

    The mechanism for the iridium-BINAP catalyzed dehydrogenative decarbonylation of primary alcohols with the liberation of molecular hydrogen and carbon monoxide was studied experimentally and computationally. The reaction takes place by tandem catalysis through two catalytic cycles involving dehyd...... a rate-determining phosphine dissociation for the decarbonylation of aldehydes....

  1. The mechanism of the phosphine-free palladium-catalyzed hydroarylation of alkynes

    DEFF Research Database (Denmark)

    Ahlquist, Mårten Sten Gösta; Fabrizi, G.; Cacchi, S.;

    2006-01-01

    The mechanism of the Pd-catalyzed hydroarylation and hydrovinylation reaction of alkynes has been studied by a combination of experimental and theoretical methods (B3LYP), with an emphasis on the phosphine-free version. The regioselectivity of the hydroarylation and hydrovinylation shows unexpected...

  2. Memory effects in palladium-catalyzed allylic Alkylations of 2-cyclohexen-1-yl acetate

    DEFF Research Database (Denmark)

    Svensen, Nina; Fristrup, Peter; Tanner, David Ackland;

    2007-01-01

    The objective of this work was to characterize the enantiospecificity of the allylic alkylation of enantioenriched 2-cyclohexen-1-yl acetate with the enolate ion of dimethyl malonate catalyzed by unsymmetrical palladium catalysts. The precatalysts employed were (eta(3)-allyl)PdLCl, where L is a m...

  3. Structural Formation Studies of UV-Catalyzed Gels and Aerogels byLight Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, Arlon J.; Ayers, Michael R.

    1998-04-01

    The skeletal structure of aerogel is determined before, during, and after the gel is formed. Supercritical drying of aerogel largely preserves the pore structure that is determined near the time of gelation. To better understand these gel formation mechanisms we carried out measurements of the time evolution of light scattering in a series of gels prepared without conventional acid or base catalysis. Instead, ultraviolet light was used to catalyze the formation of silica gels made from the hydrolysis of tetraethylorthosilicate and partly prehydrolyzed tetraethylorthosilicate in ethanol. Time evolution of light scattering provides information regarding the rate and geometrical nature of the assembly of the primary silica particles formed in the sol. UV-catalyzed gels show volumetric growth typical of acid-catalyzed gels, except when UV exposure is discontinued at the gel point, where gels then show linear chain formation typical of base-catalyzed gels. Long term UV exposure leads to coarsening of the pore network, a decrease in the clarity of the aerogel, and an increase in the surface area of the aerogel. Additionally, UV exposure up to the gel point leads to increased crystallinity in the final aerogel.

  4. Alloying Au surface with Pd reduces the intrinsic activity in catalyzing CO oxidation

    KAUST Repository

    Qian, Kun

    2016-03-30

    © 2016. Various Au-Pd/SiO2 catalysts with a fixed Au loading but different Au:Pd molar ratios were prepared via deposition-precipitation method followed by H2 reduction. The structures were characterized and the catalytic activities in CO oxidation were evaluated. The formation of Au-Pd alloy particles was identified. The Au-Pd alloy particles exhibit enhanced dispersions on SiO2 than Au particles. Charge transfer from Pd to Au within Au-Pd alloy particles. Isolated Pd atoms dominate the surface of Au-Pd alloy particles with large Au:Pd molar ratios while contiguous Pd atoms dominate the surface of Au-Pd alloy particles with small Au:Pd molar ratios. Few synergetic effect of Au-Pd alloy occurs on catalyzing CO oxidation under employed reaction conditions. Alloying Au with Pd reduces the intrinsic activity in catalyzing CO oxidation, and contiguous Pd atoms on the Au-Pd alloy particles are capable of catalyzing CO oxidation while isolated Pd atoms are not. These results advance the fundamental understandings of Au-Pd alloy surfaces in catalyzing CO oxidation.

  5. Synthesis of 5-hydroxymethylfurfural (HMF) by acid catalyzed dehydration of glucose-fructose mixtures

    DEFF Research Database (Denmark)

    Pedersen, Asbjørn Toftgaard; Ringborg, Rolf Hoffmeyer; Grotkjær, Thomas

    2015-01-01

    allowing the use of the cheapest available source of fructose: high fructose corn syrup. The dehydration was catalyzed by hydrochloric acid and conducted in acetone-water mixtures, which ensured good selectivity towards HMF and eliminated precipitation of polymer by-products (insoluble humins). Through...

  6. Hydrazone as the directing group for Ir-catalyzed arene diborylations and sequential functionalizations.

    Science.gov (United States)

    Ros, Abel; López-Rodríguez, Rocío; Estepa, Beatriz; Álvarez, Eleuterio; Fernández, Rosario; Lassaletta, José M

    2012-03-14

    The use of hemilabile pyridine-hydrazone N,N-ligands allows the highly selective Ir-catalyzed ortho,ortho'-directed diborylation of aromatic N,N-dimethylhydrazones in near-quantitative yields. One-pot sequential Suzuki-Miyaura cross-coupling with different aryl bromides provides a short entry to unsymmetrically substituted 2,6-diarylbenzaldehyde derivatives.

  7. A Meldrum's Acid Catalyzed Synthesis of Bis (indolyl) methanes in Water under Ultrasonic Condition

    Institute of Scientific and Technical Information of China (English)

    WANG,Shun-Yi; JI,Shun-Jun; SU,Xiao-Ming

    2008-01-01

    A highly effective Meldrum's acid catalyzed synthesis of bis(indol-3-yl)methanes has been developed. This reaction provides the corresponding bis(indol-3-yl)methanes in high yields after short reaction time in the presence of 2 mol% catalyst in water under ultrasonic condition.

  8. Monooxygenation of small hydrocarbons catalyzed by bacterial cytochrome p450s.

    Science.gov (United States)

    Shoji, Osami; Watanabe, Yoshihito

    2015-01-01

    Cytochrome P450s (P450s) catalyze the NAD(P)H/O2-dependent monooxygenation of less reactive organic molecules under mild conditions. The catalytic activity of bacterial P450s is very high compared with P450s isolated from animals and plants, and the substrate specificity of bacterial P450s is also very high. Accordingly, their catalytic activities toward nonnative substrates are generally low especially toward small hydrocarbons. However, mutagenesis approaches have been very successful for engineering bacterial P450s for the hydroxylation of small hydrocarbons. On the other hand, "decoy" molecules, whose structures are very similar to natural substrates, can be used to trick the substrate recognition of bacterial P450s, allowing the P450s to catalyze oxidation reactions of nonnative substrates without any substitution of amino acid residues in the presence of decoy molecules. Thus, the hydroxylation of small hydrocarbons such as ethane, propane, butane and benzene can be catalyzed by P450BM3, a long-alkyl-chain hydroxylase, using substrate misrecognition of P450s induced by decoy molecules. Furthermore, a number of H2O2-dependent bacterial P450s can catalyze the peroxygenation of a variety of nonnative substrates through a simple substrate-misrecognition trick, in which catalytic activities and enantioselectivity are dependent on the structure of decoy molecules.

  9. Synthesis of Symmetrical Biaryls via Rhodium Catalyzed Dimerization of Arylmercurials and Mechanism of the Dimerization

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A series of symmetrical biaryls was synthesized from arylmercuric chlorides and biarylmercurials in the presence of [ClRh(CO)2]2 in hexamethylphosphoramide(HMPA). The mechanism of the [ClRh(CO)2]2 catalyzed dimerization of biarylmercurials was studied, and shown to be mainly intermolecular reaction.

  10. Investigation of acetic acid-catalyzed hydrothermal pretreatment on corn stover

    DEFF Research Database (Denmark)

    Xu, Jian; Thomsen, Mette Hedegaard; Thomsen, Anne Belinda

    2010-01-01

    Acetic acid (AA)-catalyzed liquid hot water (LHW) pretreatments on raw corn stover (RCS) were carried out at 195 °C at 15 min with the acetic acid concentrations between 0 and 400 g/kg RCS. After pretreatment, the liquor fractions and water-insoluble solids (WIS) were collected separately...

  11. Directing-group-assisted copper-catalyzed oxidative esterification of phenols with aldehydes.

    Science.gov (United States)

    Zheng, Yong; Song, Wei-Bin; Xuan, Li-Jiang

    2015-11-28

    A directing-group-assisted copper-catalyzed oxidative esterification of phenols with aldehydes using TBHP as an oxidant was described. This methodology which showed the advantages of base, ligand free, short routes and functional group tolerance could be used as an alternative protocol for the classical esterification reactions.

  12. Cu(OAc)2 catalyzed Sonogashira cross-coupling reaction in amines

    Institute of Scientific and Technical Information of China (English)

    Sheng Mei Guo; Chen Liang Deng; Jin Heng Li

    2007-01-01

    A simple Cu(OAc)2 catalyzed Sonogashira coupling protocol is presented. It was found that the couplings of a variety of aryl halides with terminal alkynes were conducted smoothly to afford the corresponding desired products in moderate to excellent yields, using Cu(OAc)2 as the catalyst and Et3N as the solvent.

  13. Large acceleration of α-chymotrypsin-catalyzed dipeptide formation by 18-crown-6 in organic solvents

    NARCIS (Netherlands)

    Unen, van Dirk-Jan; Engbersen, Johan F.J.; Reinhoudt, David N.

    1998-01-01

    The effects of 18-crown-6 on the synthesis of peptides catalyzed by α-chymotrypsin are reported. Lyophilization of the enzyme in the presence of 50 equivalents of 18-crown-6 results in a 425-fold enhanced activity when the reaction between the 2-chloroethylester of N-acetyl-L-phenylalanine and L-phe

  14. GSTP1-1 stereospecifically catalyzes glutathione conjugation of ethacrynic acid

    NARCIS (Netherlands)

    Iersel, M.L.P.S. van; Lipzig, M.M.H. van; Rietjens, I.M.C.M.; Vervoort, J.; Bladeren, P.J. van

    1998-01-01

    Using 1H NMR two diastereoisomers of the ethacrynic acid glutathione conjugate (EASG) as well as ethacrynic acid (EA) could be distinguished and quantified individually. Chemically prepared EASG consists of equal amounts of both diastereoisomers. GSTP1-1 stereospecifically catalyzes formation of one

  15. A Novel Metal-free and Highly Efficient Hydroarylation of Styrenes Catalyzed by Molecular Iodine

    Institute of Scientific and Technical Information of China (English)

    SUN Gao-Jun; ZHANG Tai-Chang; SHENG Liu-Si; QI Fei; WANG Zhi-Yong

    2008-01-01

    A molecular iodine catalyzed hydroarylation of styrenes by arenes has been developed.This reaction could be carried out at 25 ℃ under a solvent-free condition, giving rise to the corresponding products with yields up to 93%.A series of 1,1-diarylalkane derivatives were easily prepared without any involvement of metal catalysts.

  16. Homocoupling of benzyl halides catalyzed by POCOP-nickel pincer complexes

    KAUST Repository

    Chen, Tao

    2012-08-01

    Two types of POCOP-nickel(II) pincer complexes were prepared by mixing POCOP pincer ligands and NiX 2 in toluene at reflux. The resulting nickel complexes efficiently catalyze the homocoupling reactions of benzyl halides in the presence of zinc. The coupled products were obtained in excellent to quantitative yields. © 2012 Elsevier Ltd. All rights reserved.

  17. Practical and General Palladium-Catalyzed Synthesis of Ketones from Internal Olefins

    KAUST Repository

    Morandi, Bill

    2013-01-16

    Make it simple! A convenient and general palladium-catalyzed oxidation of internal olefins to ketones is reported. The transformation occurs at room temperature and shows wide substrate scope. Applications to the oxidation of seed-oil derivatives and a bioactive natural product (see scheme) are described, as well as intriguing mechanistic features.

  18. Copper and amine free Sonogashira cross-coupling reaction catalyzed by efficient diphosphane-palladium catalyst

    Institute of Scientific and Technical Information of China (English)

    Ting He; Lei Lei Wu; Xing Li Fu; Hai Yan Fu; Hua Chen; Rui Xiang Li

    2011-01-01

    The commercially available diphosphane ligand MeO-BIPHEP was first investigated in the palladium-catalyzed Sonogashira reaction in the absence of copper and amine. The coupling of various aryl bromides and aryl chlorides with phenylacetylene gave moderate to excellent yields.

  19. Palladium-catalyzed Coupling between Aryl Halides and Trimethylsilylacetylene Assisted by Dimethylaminotrimethyltin

    Institute of Scientific and Technical Information of China (English)

    Cai Liangzhen; Yang Dujuan; Sun Zhonghua; Tao Xiaochun; Cai Lisheng; Pike Victor W

    2011-01-01

    Palladium-catalyzed coupling between aryl halides, especially less reactive ones or N-heteroaryls, and trimethylsilylacetylene in the presence of dimethylaminotrimethyltin generated the coupled products in high yields. The reaction does not need CuI and base as auxiliary agents.

  20. Enzyme catalyzed oxidative gelation of sugar beet pectin: Kinetics and rheology

    DEFF Research Database (Denmark)

    Abang Zaidel, Dayang Norulfairuz; Chronakis, Ioannis S.; Meyer, Anne S.

    2012-01-01

    Sugar beet pectin (SBP) is a marginally utilized co-processing product from sugar production from sugar beets. In this study, the kinetics of oxidative gelation of SBP, taking place via enzyme catalyzed cross-linking of ferulic acid moieties (FA), was studied using small angle oscillatory measure...

  1. Synthesis of Flurbiprofen via Suzuki Reaction Catalyzed by Palladium Charcoal in Water

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Flurbiprofen 1, an excellent nonsteroidal an tiinflammatory drug, was synthesized in 5steps in 69% overall yield. The key step of constructing the biaryl fragment was successfully achieved via Pd/C-catalyzed Suzuki coupling reaction in water using sodium tetraphenylborate as phenylation reagent.

  2. A Palladium-Catalyzed Vinylcyclopropane (3 + 2) Cycloaddition Approach to the Melodinus Alkaloids

    KAUST Repository

    Goldberg, Alexander F. G.

    2011-08-19

    A palladium-catalyzed (3+2) cycloaddition of a vinylcyclopropane and a β-nitrostyrene is employed to rapidly assemble the cyclopentane core of the Melodinus alkaloids. The ABCD ring system of the natural product family is prepared in six steps from commercially available materials.

  3. Ligand-guided pathway selection in nickel-catalyzed couplings of enals and alkynes.

    Science.gov (United States)

    Li, Wei; Montgomery, John

    2012-01-28

    Nickel-catalyzed couplings of enals and alkynes utilizing triethylborane as the reducing agent illustrate a significant dependence on ligand structure. Simple variation of monodentate phosphines allows selective access to alkylative couplings or reductive cycloadditions, while further variation of reaction conditions provides clean access to reductive couplings and redox-neutral couplings.

  4. Room-Temperature Palladium-Catalyzed Direct 2-Arylation of Benzoxazoles with Aryl and Heteroaryl Bromides†

    Science.gov (United States)

    Gao, Feng; Kim, Byeong-Seon; Walsh, Patrick J.

    2014-01-01

    An efficient room-temperature palladium-catalyzed direct 2-arylation of benzoxazoles with aryl bromides is presented. The Pd(OAc)2/NiXantphos-based catalyst enables the introduction of various aryl and heteroaryl groups, via a deprotonative cross-coupling process (DCCP) in good to excellent yields (75–99%). PMID:25078988

  5. Regio- and Diasteroselectivity of Rhodium-catalyzed Ring Opening Reaction of Oxabenzonorbornadienes with Heteroatom Nucleophiles

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new rhodium catalyzed ring opening reaction of oxabenzonorbornadienes and its derivatives was described. This reaction forms a new carbon-nitrogen bond via an intermolecular allylic displacement of the bridgehead oxygen with a piperazine's derivatives, which proceeds with very high regioselectivity.

  6. Synthesis of 2-substituted tetraphenylenes via transition-metal-catalyzed derivatization of tetraphenylene

    Directory of Open Access Journals (Sweden)

    Shulei Pan

    2016-06-01

    Full Text Available A new strategy for the synthesis of 2-substituted tetraphenylenes through a transition-metal-catalyzed derivatization has been developed. Three types of functionalities, including OAc, X (Cl, Br, I and carbonyl, were introduced onto tetraphenylene, which allows the easy access to a variety of monosubstituted tetraphenylenes. These reactions could accelerate research on the properties and application of tetraphenylene derivatives.

  7. Direct synthesis of diaryl sulfides by copper-catalyzed coupling of aryl halides with aminothiourea

    Institute of Scientific and Technical Information of China (English)

    Xiang Mei Wu; Wei Ya Hu

    2012-01-01

    An efficient and simple protocol of copper-catalyzed C-S bond formation between aryl halides and inexpensive and commercially available aminothiourea is reported.A variety of symmetrical diaryl sulfides can be synthesized in good to excellent yields up to 94% with the advantage of avoiding foul-smelling thiols.

  8. Mukaiyama Aldol Reaction of 1, 2-Bis(trimethylsiloxy) Cyclobutene Catalyzed by Magnesium(II) Iodide

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Efficient Mukaiyama-type aldol reaction of 1, 2-bis(trimethylsiloxy)cyclobutene with aromatic aldehydes catalyzed by MgI2 is reported. The resulting succinoylation product of aldehyde was converted into the synthetic useful γ-lactone and butenolide derivatives.

  9. Palladium-catalyzed regioselective decarboxylative alkylation of arenes and heteroarenes with aliphatic carboxylic acids.

    Science.gov (United States)

    Premi, Chanchal; Dixit, Ankit; Jain, Nidhi

    2015-06-05

    An unprecedented Pd(OAc)2-catalyzed decarboxylative alkylation of unactivated arenes, with aliphatic carboxylic acids as inexpensive alkyl sources, is reported. The alkylation, controlled by the directing group, is regioselective, shows high functional group tolerance, and provides mild access to alkylated indolines, 2-phenylpyridines, and azobenzenes under solvent-free conditions in moderate to high yields.

  10. Preparation of fluorinated biaryls through direct palladium-catalyzed coupling of polyfluoroarenes with aryltrifluoroborates

    KAUST Repository

    Fang, Xin

    2013-07-01

    The direct palladium-catalyzed coupling of polyfluoroarenes with aryltrifluoroborates gave the desired products of fluorinated biaryls in good to excellent yields. A diverse set of important functional groups including methoxy, aldehyde, ester, nitro and halide can be well tolerated in the protocol. © 2013 Elsevier B.V. All rights reserved.

  11. Iodine-catalyzed thiolation of electron-rich aromatics using sulfonyl hydrazides as sulfenylation reagents.

    Science.gov (United States)

    Zhao, Xia; Li, Tianjiao; Zhang, Lipeng; Lu, Kui

    2016-01-21

    Iodine-catalyzed thiolation of electron-rich aromatics, including substituted anisole, thioanisole, phenol, toluene, and naphthalene, using sulfonyl hydrazides as sulfenylation reagents was carried out. Sulfonothioates, the products of decomposition of sulfonyl hydrazides in the presence of iodine, are proposed as the major sulfenylation species in this transformation.

  12. Cobalt-catalyzed C-H olefination of aromatics with unactivated alkenes.

    Science.gov (United States)

    Manoharan, Ramasamy; Sivakumar, Ganesan; Jeganmohan, Masilamani

    2016-08-18

    A cobalt-catalyzed C-H olefination of aromatic and heteroaromatic amides with unactivated alkenes, allyl acetates and allyl alcohols is described. This method offers an efficient route for the synthesis of vinyl and allyl benzamides in a highly stereoselective manner. It is observed that the ortho substituent on the benzamide moiety is crucial for the observation of allylated products in unactivated alkenes.

  13. Stabilization of oil-in-water emulsions by enzyme catalyzed oxidative gelation of sugar beet pectin

    DEFF Research Database (Denmark)

    Abang Zaidel, Dayang Norulfairuz; Chronakis, Ioannis S.; Meyer, Anne S.

    2013-01-01

    Enzyme catalyzed oxidative cross-linking of feruloyl groups can promote gelation of sugar beet pectin (SBP). It is uncertain how the enzyme kinetics of this cross-linking reaction are affected in emulsion systems and whether the gelation affects emulsion stability. In this study, SBP (2.5% w...

  14. Facile Synthesis of Symmetrical Triindolylmethanes Catalyzed by Iodine under Solvent-free Condition

    Institute of Scientific and Technical Information of China (English)

    ZENG Xiao-Fei; JI Shun-Jun; SU Xiao-Ming

    2008-01-01

    The reaction of various indoles (1a-1k, 3 equiv.) with triethyl orthoformate (1.2 equiv.) catalyzed by I2 (5mol%) at room temperature in 2-15 min under a solvent-free condition afforded the respective symmetrical triindolylmethanes (3a-3k) in good to excellent yields without any side products.

  15. Preparation of polyfunctional zinc organometallics using an Fe- or Co-catalyzed Cl/Zn-exchange.

    Science.gov (United States)

    Melzig, Laurin; Diène, Coura R; Rohbogner, Christoph J; Knochel, Paul

    2011-06-17

    A new Fe- or Co-catalyzed Cl/Zn-exchange reaction allows the direct transformation of aryl, heteroaryl, and also alkyl chlorides into the corresponding zinc reagents. The method tolerates functional groups such as a nitrile or an ester. Remarkably, secondary and tertiary alkyl chlorides are suitable substrates for the Cl/Zn exchange.

  16. Palladium-catalyzed cross-coupling reactions of allylic halides and acetates with indium organometallics.

    Science.gov (United States)

    Rodríguez, David; Pérez Sestelo, José; Sarandeses, Luis A

    2004-11-12

    The palladium(0)-catalyzed cross-coupling reaction of allylic halides and acetates with indium organometallics is reported. In this synthetic transformation, triorganoindium compounds and tetraorganoindates (aryl, alkenyl, and methyl) react with cinnamyl and geranyl halides and acetates to afford the S(N)2 product regioselectively and in good yield. The reaction proceeds with net inversion of the stereochemical configuration.

  17. Specifically Grafting Hematin on MPTS-Coated Carbon Nanotubes for Catalyzing the Oxidation of Aniline

    Directory of Open Access Journals (Sweden)

    Kunkun Zheng

    2016-08-01

    Full Text Available Catalysts supported on nanomaterials have been widely investigated for the treatment of hazardous materials. This work has developed a novel method for grafting hematin on nanomaterials for catalyzing the oxidation of aniline in order to remove aniline from wastewater. Magnetic multi-walled carbon nanotubes (M-MWCNTs were coated with a layer formed through the hydrolysis and condensation of 3-mercaptopropyltriethoxysilane (MPTS. Hematin was specifically grafted on the MPTS-coated M-MWCNTs through thiol-alkene reaction. Hematin-MPTS-M-MWCNTs were used to catalyze the oxidation of aniline, and a high efficiency has been obtained. Consecutive use of the conjugate of hematin-MPTS-M-MWCNTs has been investigated, and the activity has been retained to a significant extent after five reaction/cleaning cycles. The result demonstrates that hematin-MPTS-M-MWCNTs are efficient for catalyzing the oxidation of aniline. The methodology for the specific grafting of hematin is of general utility, it is an easy-to-operate method and can be extended to other supports. Potentially, hematin-MPTS-based conjugates have a widespread application in catalyzing the removal of aniline from wastewater.

  18. DFT Investigation of the Palladium-Catalyzed Ene-Yne Coupling

    DEFF Research Database (Denmark)

    Henriksen, Signe Teuber; Tanner, David Ackland; Skrydstrup, T.;

    2010-01-01

    The mechanism of the recently developed palladium-catalyzed ene-yne coupling has been evaluated by DFT methods. The calculations validate the previously proposed reaction mechanism and explain the stereoselectivity of the reaction (exclusive formation of the E isomer of the disubstituted alkene...

  19. Direct 2-acetoxylation of quinoline N-oxides via copper catalyzed C-H bond activation.

    Science.gov (United States)

    Chen, Xuan; Zhu, Chongwei; Cui, Xiuling; Wu, Yangjie

    2013-08-07

    An efficient and direct 2-acetoxylation of quinoline N-oxides via copper(I) catalyzed C-H bond activation has been developed. This transformation was achieved using TBHP as an oxidant in the cross-dehydrogenative coupling (CDC) reaction of quinoline N-oxides with aldehydes, and provided a practical pathway to 2-acyloxyl quinolines.

  20. Copper(II)-catalyzed electrophilic amination of quinoline N-oxides with O-benzoyl hydroxylamines.

    Science.gov (United States)

    Li, Gang; Jia, Chunqi; Sun, Kai; Lv, Yunhe; Zhao, Feng; Zhou, Kexiao; Wu, Hankui

    2015-03-21

    Copper acetate-catalyzed C-H bond functionalization amination of quinoline N-oxides was achieved using O-benzoyl hydroxylamine as an electrophilic amination reagent, thereby affording the desired products in moderate to excellent yields. Electrophilic amination can also be performed in good yield on a gram scale.

  1. Enantioconvergent synthesis by sequential asymmetric Horner-Wadsworth-Emmons and palladium-catalyzed allylic substitution reactions

    DEFF Research Database (Denmark)

    Pedersen, Torben Møller; Hansen, E. Louise; Kane, John

    2001-01-01

    A new method for enantioconvergent synthesis has been developed. The strategy relies on the combination of an asymmetric Horner-Wadsworth-Emmons (HWE) reaction and a palladium-catalyzed allylic substitution. Different $alpha@-oxygen-substituted, racemic aldehydes were initially transformed...

  2. Cross-linking proteins by laccase-catalyzed oxidation: importance relative to other modifications.

    Science.gov (United States)

    Steffensen, Charlotte L; Andersen, Mogens L; Degn, Peter E; Nielsen, Jacob H

    2008-12-24

    Laccase-catalyzed oxidation was able to induce intermolecular cross-links in beta-lactoglobulin, and ferulic acid-mediated laccase-catalyzed oxidation was able to induce intermolecular cross-links in alpha-casein, whereas transglutaminase cross-linked only alpha-casein. In addition, different patterns of laccase-induced oxidative modifications were detected, including dityrosine formation, formation of fluorescent tryptophan oxidation products, and carbonyls derived from histidine, tryptophan, and methionine. Laccase-catalyzed oxidation as well as transglutaminase induced only minor changes in surface tension of the proteins, and the changes could not be correlated to protein cross-linking. The presence of ferulic acid was found to influence the effect of laccase, allowing laccase to form irreducible intermolecular cross-links in beta-lactoglobulin and resulting in proteins exercising higher surface tensions due to cross-linking as well as other oxidative modifications. The outcome of using ferulic acid-mediated laccase-catalyzed oxidation to modify the functional properties of proteinaceous food components or other biosystems is expected to be highly dependent on the protein composition, resulting in different changes of the functional properties.

  3. A Novel Palladium-Catalyzed Reaction and Its Application in Preparation of Derivatives of Stilbazols

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel palladium-catalyzed coupling reaction for the preparation of derivatives of stilbazoles was presented.A series of stilbazoles were synthesized firstly by this highly efficient method.From this reaction it was found that reaction solvent is one of important factors in this catalytic system.

  4. A novel reactor for determination of kinetics for solid catalyzed gas reactions

    NARCIS (Netherlands)

    Borman, P.C.; Bos, A.N.R.; Westerterp, K.R.

    1994-01-01

    A novel perfectly mixed laboratory reactor for determining kinetics of heterogeneously catalyzed gas-phase reactions has been developed. Perfect mixing is achieved by circulating the gas in the reactor using an axial flow impeller in a well streamlined enclosure. Pellets are fixed in a rectangular o

  5. Surprisingly Mild Enolate-Counterion-Free Pd(0)-Catalyzed Intramolecular Allylic Alkylations

    DEFF Research Database (Denmark)

    Madec, David; Prestat, Guillaume; Martini, Elisabetta;

    2005-01-01

    Palladium-catalyzed intramolecular allylic alkylations of unsaturated EWG-activated amides can take place under phase-transfer conditions or in the presence of a crown ether. These new reaction conditions are milder and higher yielding than those previously reported. A rationalization for such an...

  6. The Extension Storyteller: Using Stories to Enhance Meaning and Catalyze Change

    Science.gov (United States)

    Franz, Nancy

    2016-01-01

    Many cultures share and pass on norms through storytelling. Extension as a culture also creates and shares stories to pass on history, provide information about Extension work and experiences, and develop the organization. However, Extension as a culture less frequently uses storytelling to enhance meaning and catalyze related change. This article…

  7. Optimizing the Acid Catalyzed Synthesis of Hyperbranched Poly(Glycerol-diacids) Oligomers

    Science.gov (United States)

    Oligomeric pre-polymers were synthesized by the acid-catalyzed condensation of glycerol with succinic acid, glutaric acid and azelaic acid in dimethylsulfoxide (DMSO) or dimethylformamide (DMF). The prepolymers were obtained, on average in 84% yield, and were characterized by proton NMR, MALDI-TOF ...

  8. KF-Montmorillonite-catalyzed Michael Addition Reaction of Malononitrile to α,β-Unsaturated Ketones

    Institute of Scientific and Technical Information of China (English)

    SHI Daqing; WU Nan; ZHUANG Qiya

    2009-01-01

    The Michael addition reaction of α,β-unsaturated ketones with malononitrile catalyzed by KF-montmorillonite was investigated. It was interesting to note that at different reaction temperatures the addition and cycloaddition re-action products were obtained. This method has the advantages of good yields, mild reaction conditions, easy work-up and inexpensive reagents over the existing procedures.

  9. Enzyme-catalyzed ring-opening polymerization of unsubstituted beta-lactam

    NARCIS (Netherlands)

    Schwab, Leendert W.; Kroon, Renee; Schouten, Arend Jan; Loos, Katja

    2008-01-01

    The synthesis of poly(beta-alanine) by Candida antarctica lipase B immobilized as novozyme 435 catalyzed ring-opening of 2-azetidinone is reported. After removal of cyclic side products and low molecular weight species pure linear poly(beta-alanine) is obtained. The formation of the polymer is confi

  10. Atomistic Model for the Polyamide Formation from beta-Lactam Catalyzed by Candida antarctica Lipase B

    NARCIS (Netherlands)

    Baum, Iris; Elsaesser, Brigitta; Schwab, Leendert W.; Loos, Katja; Fels, Gregor; Elsässer, Brigitta

    2011-01-01

    Candida antarctica lipase B (CALB) is an established biocatalyst for a variety of transesterification, amidation, and polymerization. reactions. In contrast to polyesters, poly amides are not yet generally accessible via enzymatic polymerization. In this regard, an enzyme-catalyzed ring-opening poly

  11. Beta-D-xylosidase from Selenomonas ruminantium: thermodynamics of enzyme-catalyzed and noncatalyzed reactions

    Science.gov (United States)

    Beta-D-xylosidase/alpha-L-arabinofuranosidase from Selenomonas ruminantium (SXA) is the most active enzyme known for catalyzing hydrolysis of 1,4-beta-D-xylooligosaccharides to D-xylose. Temperature dependence for hydrolysis of 4-nitrophenyl-beta-D-xylopyranoside (4NPX), 4-nitrophenyl-alpha-L-arabi...

  12. Enantioselective Evans-Tishchenko Reduction of b-Hydroxyketone Catalyzed by Lithium Binaphtholate

    Directory of Open Access Journals (Sweden)

    Makoto Nakajima

    2011-06-01

    Full Text Available Lithium diphenylbinaphtholate catalyzed the enantioselective Evans-Tishchenko reduction of achiral b-hydroxyketones to afford monoacyl-protected 1,3-diols with high stereoselectivities. In the reaction of racemic b-hydroxyketones, kinetic optical resolution occurred in a highly stereoselective manner.

  13. Palladium-Catalyzed Cross-Coupling Reactions of Perfluoro Organic Compounds

    Directory of Open Access Journals (Sweden)

    Masato Ohashi

    2014-09-01

    Full Text Available In this review, we summarize our recent development of palladium(0-catalyzed cross-coupling reactions of perfluoro organic compounds with organometallic reagents. The oxidative addition of a C–F bond of tetrafluoroethylene (TFE to palladium(0 was promoted by the addition of lithium iodide, affording a trifluorovinyl palladium(II iodide. Based on this finding, the first palladium-catalyzed cross-coupling reaction of TFE with diarylzinc was developed in the presence of lithium iodide, affording α,β,β-trifluorostyrene derivatives in excellent yield. This coupling reaction was expanded to the novel Pd(0/PR3-catalyzed cross-coupling reaction of TFE with arylboronates. In this reaction, the trifluorovinyl palladium(II fluoride was a key reaction intermediate that required neither an extraneous base to enhance the reactivity of organoboronates nor a Lewis acid additive to promote the oxidative addition of a C–F bond. In addition, our strategy utilizing the synergetic effect of Pd(0 and lithium iodide could be applied to the C–F bond cleavage of unreactive hexafluorobenzene (C6F6, leading to the first Pd(0-catalyzed cross-coupling reaction of C6F6 with diarylzinc compounds.

  14. Cobalt-catalyzed hydrogenation of esters to alcohols: unexpected reactivity trend indicates ester enolate intermediacy.

    Science.gov (United States)

    Srimani, Dipankar; Mukherjee, Arup; Goldberg, Alexander F G; Leitus, Gregory; Diskin-Posner, Yael; Shimon, Linda J W; Ben David, Yehoshoa; Milstein, David

    2015-10-12

    The atom-efficient and environmentally benign catalytic hydrogenation of carboxylic acid esters to alcohols has been accomplished in recent years mainly with precious-metal-based catalysts, with few exceptions. Presented here is the first cobalt-catalyzed hydrogenation of esters to the corresponding alcohols. Unexpectedly, the evidence indicates the unprecedented involvement of ester enolate intermediates.

  15. Synthesis of 2-substituted tetraphenylenes via transition-metal-catalyzed derivatization of tetraphenylene

    Science.gov (United States)

    Pan, Shulei; Jiang, Hang; Zhang, Yu; Chen, Dushen

    2016-01-01

    Summary A new strategy for the synthesis of 2-substituted tetraphenylenes through a transition-metal-catalyzed derivatization has been developed. Three types of functionalities, including OAc, X (Cl, Br, I) and carbonyl, were introduced onto tetraphenylene, which allows the easy access to a variety of monosubstituted tetraphenylenes. These reactions could accelerate research on the properties and application of tetraphenylene derivatives. PMID:27559378

  16. Enantioselective addition of diphenyl phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified organocatalysts

    Science.gov (United States)

    Jang, Hee Seung; Kim, Yubin

    2016-01-01

    Summary Chiral binaphthyl-modified squaramide-catalyzed enantioselective addition of diphenyl phosphonate to ketimines derived from isatins has been achieved. This method affords practical and efficient access to chiral 3-amino-3-phosphonyl-substituted oxindole derivatives in high yields with excellent enantioselectivities (up to 99% ee). PMID:27559405

  17. Synthesis of a novel chemotype via sequential metal-catalyzed cycloisomerizations

    Directory of Open Access Journals (Sweden)

    Bo Leng

    2012-08-01

    Full Text Available Sequential cycloisomerizations of diynyl o-benzaldehyde substrates to access novel polycyclic cyclopropanes are reported. The reaction sequence involves initial Cu(I-mediated cycloisomerization/nucleophilic addition to an isochromene followed by diastereoselective Pt(II-catalyzed enyne cycloisomerization.

  18. NHC-Catalyzed/Titanium(IV);#8722;Mediated Highly Diastereo- and Enantioselective Dimerization of Enals

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Daniel T.; Cardinal-David, Benoit; Roberts, John M.; Sarjeant, Amy A.; Scheidt, Karl A. (NWU)

    2012-05-09

    An NHC-catalyzed, diastereo- and enantioselective dimerization of enals has been developed. The use of Ti(Oi-Pr){sub 4} is a key element for the reactivity and selectivity of this process. The cyclopentenes are obtained with high levels of diastereo- and enantioselectivity and their synthetic utility is demonstrated by functionalization of the product alkene.

  19. Palladium-Catalyzed Polyfluorophenylation of Porphyrins with Bis(polyfluorophenylzinc Reagents

    Directory of Open Access Journals (Sweden)

    Toshikatsu Takanami

    2013-10-01

    Full Text Available A facile and efficient method for the synthesis of pentafluorophenyl- and related polyfluorophenyl-substituted porphyrins has been achieved via palladium-catalyzed cross-coupling reactions of brominated porphyrins with bis(polyfluorophenylzinc reagents. The reaction is applicable to a variety of free-base bromoporphyrins, their metal complexes, and a number of bis(polyfluorophenylzinc reagents.

  20. Gold(I)-Catalyzed Dearomative Rautenstrauch Rearrangement: Enantioselective Access to Cyclopenta[b]indoles

    Science.gov (United States)

    Zi, Weiwei; Wu, Hongmiao; Toste, F. Dean

    2016-01-01

    A highly enantioselective dearomative Rautenstrauch rearrangement catalyzed by cationic (S)-DTBM-Segphosgold(I) is reported. This reaction provides a straightforward method to prepare enantioenriched cyclopenta[b]indoles. These studies show vast difference in enantioselectivity in the reactions of propargyl acetates and propargyl acetals in the chiral ligand-controlled Rautenstrauch reaction. PMID:25710515

  1. Phosphoramidite accelerated copper(I)-catalyzed [3+2] cycloadditions of azides and alkynes

    NARCIS (Netherlands)

    Campbell-Verduyn, Lachlan S.; Mirfeizi, Leila; Dierckx, Rudi A.; Elsinga, Philip H.; Feringa, Ben L.

    2009-01-01

    Monodentate phosphoramidite ligands are used to accelerate the copper(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes (CuAAC) rapidly yielding a wide variety of functionalized 1,4-disubstituted-1,2,3-triazoles; Cu(I) and Cu(II) salts both function as the copper source in aqueous solutio

  2. Sn-free Ni-catalyzed reductive coupling of glycosyl bromides with activated alkenes.

    Science.gov (United States)

    Gong, Hegui; Andrews, R Stephen; Zuccarello, Joseph L; Lee, Stephen J; Gagné, Michel R

    2009-02-19

    A mild, stereoselective method for the Ni-catalyzed synthesis of alpha-C-alkylglycosides is reported. This approach entails the reductive coupling of glycosyl bromides with activated alkenes at room temperature, with low alkene loading as an important feature. Diastereoselective coupling with 2-substituted acrylate derivatives was made possible through the use of 2,4-dimethyl-3-pentanol as a proton source.

  3. Palladium-catalyzed reductive homocoupling of aromatic halides and oxidation of alcohols.

    Science.gov (United States)

    Zeng, Minfeng; Du, Yijun; Shao, Linjun; Qi, Chenze; Zhang, Xian-Man

    2010-04-16

    Palladium-catalyzed reductive homocoupling of aromatic halides can be performed in alcohol solutions without any auxiliary reducing reagents. Pd(dppf)Cl(2) [dppf = 1,1'-bis(diphenylphosphino)ferrocene] has been shown as the most effective catalyst among the palladium catalysts screened for the model reductive homocoupling of iodobenzene in alcoholic solutions. The reduction of iodobenzene is stoichiometrically coupled with the oxidation of solvent alcohol (3-pentanol). The X-ray photoelectron spectroscopic (XPS) studies clearly indicate that the oxidation of solvent alcohol molecules is involved with the in situ regeneration of the reductive Pd(0)(dppf) active species, indicating that the solvent alcohol also reacts as a reducing reagent for the reductive homocoupling of aromatic halides. Elimination of the external reducing reagents will simplify the product separation and purification. Base is essential for the success of the Pd(dppf)Cl(2)-catalyzed redox reaction as 2 molar equiv of base is needed to neutralize the acid byproduct formed. Biaryls are the predominant products for the Pd(dppf)Cl(2)-catalyzed reductions of the unsubstituted aromatic halides in 3-pentanol solution, whereas the dehalogenation products are predominant for the Pd(dppf)Cl(2)-catalyzed reductions of the substituted aromatic halides. The reaction mechanisms have been discussed for the palladium-mediated concomitant reduction of aromatic halides and oxidation of alcohols without any auxiliary reductants and oxidants.

  4. Room-temperature base-free copper-catalyzed trifluoromethylation of organotrifluoroborates to trifluoromethylarenes

    KAUST Repository

    Huang, Yuanyuan

    2012-12-01

    An efficient room temperature copper-catalyzed trifluoromethylation of organotrifluoroborates under the base free condition using an electrophilic trifluoromethylating reagent is demonstrated. The corresponding trifluoromethylarenes were obtained in good to excellent yields and the reaction tolerates a wide range of functional groups. © 2012 Elsevier Ltd. All rights reserved.

  5. Copper-catalyzed trifluoromethylation of arylsulfinate salts using an electrophilic trifluoromethylation reagent

    KAUST Repository

    Lin, Xiaoxi

    2013-03-01

    A copper-catalyzed method for the trifluoromethylation of arylsulfinates with Togni\\'s reagent has been developed, affording aryltrifluoromethylsulfones in moderate to good yields. A wide range of functional groups in arylsulfinates are compatible with the reaction conditions. © 2013 Elsevier Ltd. All rights reserved.

  6. Enantioselective addition of diphenyl phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified organocatalysts

    Directory of Open Access Journals (Sweden)

    Hee Seung Jang

    2016-07-01

    Full Text Available Chiral binaphthyl-modified squaramide-catalyzed enantioselective addition of diphenyl phosphonate to ketimines derived from isatins has been achieved. This method affords practical and efficient access to chiral 3-amino-3-phosphonyl-substituted oxindole derivatives in high yields with excellent enantioselectivities (up to 99% ee.

  7. Heteroaromatic sulfonates and phosphates as electrophiles in iron-catalyzed cross-couplings.

    Science.gov (United States)

    Gøgsig, Thomas M; Lindhardt, Anders T; Skrydstrup, Troels

    2009-11-01

    Employment of heteroaromatic tosylates and phosphates as suitable electrophiles in iron-catalyzed cross-coupling reactions with alkyl Grignard reagents is reported. These reactions are performed at low temperature allowing good functional group tolerance and full conversion is achieved within minutes. In addition, an aryl-aryl cross-coupling utilizing a heteroaryl sulfamate electrophile is reported.

  8. Enantioselective epoxidation and carbon-carbon bond cleavage catalyzed by Coprinus cinereus peroxidase and myeloperoxidase

    NARCIS (Netherlands)

    Tuynman, A; Lutje Spelberg, Jeffrey; Kooter, IM; Schoemaker, HE; Wever, R

    2000-01-01

    We demonstrate that myeloperoxidase (MPO) and Coprinus cinereus peroxidase (CiP) catalyze the enantioselective epoxidation of styrene and a number of substituted derivatives with a reasonable enantiomeric excess (up to 80%) and in a moderate yield. Three major differences with respect to the chlorop

  9. A new manganese-mediated, cobalt-catalyzed three-component synthesis of (diarylmethylsulfonamides

    Directory of Open Access Journals (Sweden)

    Antoine Pignon

    2014-02-01

    Full Text Available The synthesis of (diarylmethylsulfonamides and related compounds by a new manganese-mediated, cobalt-catalyzed three-component reaction between sulfonamides, carbonyl compounds and organic bromides is described. This organometallic Mannich-like process allows the formation of the coupling products within minutes at room temperature. A possible mechanism, emphasizing the crucial role of manganese is proposed.

  10. Rhodium(III)-Catalyzed C-H Activation Mediated Synthesis of Isoquinolones from Amides and Cyclopropenes.

    Science.gov (United States)

    Hyster, Todd K; Rovis, Tomislav

    2013-01-01

    We have developed a synthesis of 4-substituted isoquinolones from the Rh(III)-catalyzed, C-H activation mediated, coupling of O-pivaloyl benzhydroxamic acids and 3,3-disubstituted cyclopropenes. Experiments suggest the formation of a [4.1.0] bicyclic-system, which can open under acidic conditions to generate the desired isoquinolone.

  11. The Use of Tertiary Alkylmagnesium Nucleophiles in Ni-Catalyzed Cross-Coupling Reactions.

    Science.gov (United States)

    Joshi-Pangu, Amruta; Biscoe, Mark R

    2012-05-14

    Nickel-catalyzed cross-coupling reactions of unactivated tertiary alkyl nucleophiles and aryl bromides have been developed using N-heterocyclic carbene ligands. These processes are reviewed alongside earlier attempts to employ unactivated tertiary alkyl nucleophiles in cross-coupling reactions. Potential mechanisms for the transformations, and future challenges in this field are discussed.

  12. Synthesis of Unsymmetrical Heterobiaryls Using palladium-catalyzed cross-coupling reactions of lithium organozincates

    OpenAIRE

    Seggio, Anne; Jutand, Anny; Priem, Ghislaine; Mongin, Florence

    2008-01-01

    International audience; Several unsymmetrical heterobiaryls have been synthesized through palladium-catalyzed cross-coupling reactions of lithium triorganozincates. The latter have been prepared by deprotonative lithiation followed by transmetalation using non hygroscopic ZnCl2*TMEDA (1/3 equiv).

  13. Rhodium(III)-Catalyzed C–H Activation Mediated Synthesis of Isoquinolones from Amides and Cyclopropenes

    Science.gov (United States)

    Hyster, Todd K.; Rovis, Tomislav

    2014-01-01

    We have developed a synthesis of 4-substituted isoquinolones from the Rh(III)-catalyzed, C–H activation mediated, coupling of O-pivaloyl benzhydroxamic acids and 3,3-disubstituted cyclopropenes. Experiments suggest the formation of a [4.1.0] bicyclic-system, which can open under acidic conditions to generate the desired isoquinolone. PMID:25346576

  14. Bifunctional Asymmetric Catalysis with Hydrogen Chloride: Enantioselective Ring-Opening of Aziridines Catalyzed by a Phosphinothiourea.

    Science.gov (United States)

    Mita, Tsuyoshi; Jacobsen, Eric N

    2009-06-01

    Ring-opening of aziridines with hydrogen chloride to form β-chloroamine derivatives is catalyzed by a chiral phosphinothiourea derivative in high yields and with high enantioselectivities. On the basis of (31)P NMR studies, activation of HCl appears to proceed via quantitative protonation of the catalyst to afford a phosphonium chloride complex.

  15. Palladium-Catalyzed Carbonylation of Aryl Bromides with N-Substituted Cyanamides

    DEFF Research Database (Denmark)

    Lian, Zhong; Friis, Stig D.; Lindhardt, Anders T.;

    2014-01-01

    The palladium(0)-catalyzed three-component coupling reaction of aryl bromides, carbon monoxide, and N-alkyl cyan­amides has been developed employing a two-chamber system with ex situ generation of carbon monoxide from a silacarboxylic acid. The reactions proceeded well and were complete with a re...

  16. Hydrogen-peroxide epoxidation of natural olefins catalyzed by a dinuclear manganese complex

    NARCIS (Netherlands)

    Mandelli, D; Voitiski, KB; Schuchardt, U; Shul'pin, GB

    2002-01-01

    The complex of Mn(IV) with the macrocyclic N-containing ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (L) [L2Mn2O3](PF6)(2) catalyzes epoxidation of (+)-limonene in CH3CN solution at room temperature. Adding CH3COOH accelerates the reaction. The products are isomers of limonene epoxide with predomi

  17. Unprecedentedly mild direct Pd-catalyzed arylation of oxazolo[4,5-b]pyridine

    DEFF Research Database (Denmark)

    Zhuravlev, Fedor

    2006-01-01

    Pd-catalyzed C-2 arylation of oxazolo[4,5-b]pyridine proceeds efficiently at 30 degrees C and tolerates a variety of aryl halides, including derivatized amino acids for which no racemization was observed during the reaction. Experimental evidence for facile deprotonation of oxazolo[4,5-b]pyridine...

  18. Microwave-Assisted Olefination Reaction of Alkylzinc with Aromatic Aldehyde Catalyzed by Nickel Complex

    Institute of Scientific and Technical Information of China (English)

    MEN Xiu-Qin; WANG Jin-Xian; SHI Xiao-Ning; WANG Ke-Hu

    2003-01-01

    @@ Carbon-carbon double bond-forming reactions have always been great importance in organic synthesis. Manymethods have been described for C =C bond formation. We[1] have reported the new method of C =C bond formation of nickel catalyzed organozinc with aromatic aldehydes in the presence of Me3SiC1.

  19. Synthesis of trifluoromethylated acetylenes via copper-catalyzed trifluoromethylation of alkynyltrifluoroborates

    KAUST Repository

    Zheng, Huidong

    2012-12-01

    A new method for the synthesis of trifluoromethylated acetylenes is developed which involves the copper-catalyzed trifluoromethylation of alkynyltrifluoroborates with an electrophilic trifluoromethylating reagent. This method offers significant advantages such as efficiency and mild and base-free reaction conditions. A plausible mechanism is proposed. © 2012 Elsevier Ltd. All rights reserved.

  20. An Efficient and Green Procedure for the Knoevenagel Condensation Catalyzed by Urea

    Institute of Scientific and Technical Information of China (English)

    孙崎; 史兰香; 葛泽梅; 程铁明; 李润涛

    2005-01-01

    An efficient and green procedure for the urea catalyzed Knoevenagel condensation was developed. In the presence of a catalytic ammount of urea, stoichiometric aldehyde and active methylene compound reacted under sol-vent-free conditions at 100℃ for 5-60 min to give nearly quantitative yield of product.

  1. Facile synthesis of small crystal ZSM-5 zeolite by acid-catalyzed hydrolysis of tetraethylorthosilicate

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Small crystal zeolites ZSM-5 with sizes of 150-300 nm were synthesized using the colloidal silicate precursors as the silica source created by the acid-catalyzed hydrolysis of tetraethylorthosilicate with tetrapropylammonium bromide as the structure-directing agent within a short crystallization time of 20-35 h. The precursors and final products were detected by XRD, SEM, ICP and DLS.

  2. Copper-catalyzed asymmetric allylic substitution reactions with organozinc and Grignard reagents

    NARCIS (Netherlands)

    Geurts, Koen; Fletcher, Stephen P.; van Zijl, Anthoni W.; Minnaard, Adriaan J.; Feringa, Ben L.; Bignall, H. E.; Jauncey, D. L.; Lovell, J. E. J.; Tzioumis, A. K.; Kedziora-Chudczer, L. L.; MacQuart, J. P.; Tingay, S. J.; Rayner, D. P.; Clay, R. W.

    2008-01-01

    Asymmetric allylic alkylations (AAAs) are among the most powerful C-C bond-forming reactions. We present a brief overview of copper-catalyzed AAAs with organometallic reagents and discuss our own contributions to this field. Work with zinc reagents and phosphoramidite ligands provided a framework fo

  3. Copper-catalyzed oxidative alkynylation of diaryl imines with terminal alkynes: a facile synthesis of ynimines.

    Science.gov (United States)

    Laouiti, Anouar; Rammah, Mohamed M; Rammah, Mohamed B; Marrot, Jérome; Couty, François; Evano, Gwilherm

    2012-01-06

    An efficient copper-mediated method for the oxidative alkynylation of diaryl imines with terminal alkynes is reported. This reaction provides the first catalytic and general synthesis of ynimines and allows for an easy preparation of these useful building blocks. An improved copper-catalyzed oxidative dimerization of imines to azines and the synthesis of dienes and azadienes from ynimines are also described.

  4. An efficient synthesis of isocoumarins via a CuI catalyzed cascade reaction process

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    3-Alkyl isocoumarins are provided by CuI/amino acid-catalyzed Sonogashira coupling reaction of o-bromo benzoic acids and terminal alkynes and the subsequent additive cyclization. This cascade process allows synthesis of diverse isocoumarins by varying both coupling partners bearing a wide range of functional groups.

  5. Enantioselective BINOL-phosphoric acid catalyzed Pictet-Spengler reactions of N-benzyltryptamine

    NARCIS (Netherlands)

    Sewgobind, N.V.; Wanner, M.J.; Ingemann, S.; de Gelder, R.; van Maarseveen, J.H.; Hiemstra, H.

    2008-01-01

    Optically active tetrahydro-beta-carbolines were synthesized via an (R)-BINOL-phosphoric acid-catalyzed asynunetric Pictet-Spengler reaction of N-benzyltryptamine with a series of aromatic and aliphatic aldehydes. The tetrahydro-beta-carbolines were obtained in yields ranging from 77% to 97% and wit

  6. Lipase-catalyzed synthesis of cocoa butter equivalent from palm olein and saturated fatty acid distillate from palm oil physical refinery.

    Science.gov (United States)

    Mohamed, Ibrahim O

    2012-11-01

    Cocoa butter equivalent was prepared by enzymatic acidolysis reaction of substrate consisting of refined palm olein oil and palmitic-stearic fatty acid mixture. The reactions were performed in a batch reactor at a temperature of 60 °C in an orbital shaker operated at 160 RPM. Different mass ratios of substrates were explored and the compositions of the five major triacylglycerol (TAG) of the structured lipids were identified and quantified using cocoa butter-certified reference material IRMM-801. The reaction resulted in production of cococa butter equivent with TAG compostion (POP 26.6 %, POS 42.1, POO 7.5, SOS 18.0 %, and SOO 5.8 %) and melting temperature between 34.7 and 39.6 °C which is close to that of the cocoa butter. The result of this research demonstrated the potential use of saturated fatty acid distillate (palmitic and stearic fatty acids) obtained from palm oil physical refining process into a value-added product.

  7. Inhibition of lactoperoxidase-catalyzed oxidation by imidazole-based thiones and selones: a mechanistic study.

    Science.gov (United States)

    Roy, Gouriprasanna; Jayaram, P N; Mugesh, Govindasamy

    2013-08-01

    Herein, we describe the synthesis and biomimetic activity of a series of N,N-disubstituted thiones and selones that contain an imidazole pharmacophore. The N,N-disubstituted thiones do not show any inhibitory activity towards LPO-catalyzed oxidation reactions, but their corresponding N,N-disubstituted selones exhibit inhibitory activity towards LPO-catalyzed oxidation reactions. Substituents on the N atom of the imidazole ring appear to have a significant effect on the inhibition of LPO-catalyzed oxidation and iodination reactions. Selones 16, 17, and 19, which contain methyl, ethyl, and benzyl substituents, exhibit similar inhibition activities towards LPO-catalyzed oxidation reactions with IC50 values of 24.4, 22.5, and 22.5 μM, respectively. However, their activities are almost three-fold lower than that of the commonly used anti-thyroid drug methimazole (MMI). In contrast, selone 21, which contains a N-CH2CH2OH substituent, exhibits high inhibitory activity, with an IC50 value of 7.2 μM, which is similar to that of MMI. The inhibitory activity of these selones towards LPO-catalyzed oxidation/iodination reactions is due to their ability to decrease the concentrations of the co-substrates (H2O2 and I2), either by catalytically reducing H2O2 (anti-oxidant activity) or by forming stable charge-transfer complexes with oxidized iodide species. The inhibition of LPO-catalyzed oxidation/iodination reactions by N,N-disubstituted selones can be reversed by increasing the concentration of H2O2. Interestingly, all of the N,N-disubstituted selones exhibit high anti-oxidant activities and their glutathione peroxidase (GPx)-like activity is 4-12-fold higher than that of the well-known GPx-mimic ebselen. These experimental and theoretical studies suggest that the selones exist as zwitterions, in which the imidazole ring contains a positive charge and the selenium atom carries a large negative charge. Therefore, the selenium moieties of these selones possess highly

  8. Enzyme catalyzed production of biodiesel from olive oil.

    Science.gov (United States)

    Sanchez, Fernando; Vasudevan, Palligarnai T

    2006-10-01

    Biodiesel (fatty acid methyl esters) was produced by transesterification of triglycerides (triolein) present in olive oil with methanol and Novozym435. The effect of the molar ratio of methanol to triolein, semibatch (stepwise addition of methanol) vs batch operation, enzyme activity, and reaction temperature on overall conversion was determined. Stepwise methanolysis with a 3:1 methanol to triolein molar ratio and an overall ratio of 8:1 gave the best results. The final conversion and yield of biodiesel were unaffected by initial enzyme concentrations greater than 500 U/mL olive oil. The optimum reaction temperature was 60 degrees C. Comparison of conversion data between a test-tube scale reactor and a 2-L batch reactor revealed that the difference in conversion was within 10%. Experiments were also carried out with used cooking oil; the conversion with used cooking oil was slightly lower but no major differences were observed. The efficacy of Novozym435 was determined by reusing the enzyme; although the enzyme's relative activity decreased with reuse, it still retained 95% of its activity after five batches and more than 70% after as many as eight batches.

  9. IMPACT PROPERTIES OF METALLOCENE-CATALYZED ETHYLENE-α-OLEFIN COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Xu-rong Xu; Jun-ting Xua; Lin-xian Feng

    2002-01-01

    The impact properties of two selected metallocene-catalyzed ethylene-butene copolymers and one conventional copolymer were evaluated using Izod impact test. It is found that the metallocene-catalyzed copolymer shows superior impact properties. This result was explained on the basis of the more homogeneous inter-molecular composition distribution and narrower molecular weight distribution, which leads to more homogeneous morphology with fewer defects. Stepwise crystallization improves the impact properties, especially in the crack propagation process, to a large extent. This is due to the decrease of entanglements by stepwise crystallization, which is advantageous for the chain slip and shear. The polymer with heterogeneous intra-molecular composition distribution exhibits a more evident improvement of impact properties under stepwise crystallization.

  10. Biodiesel production from Jatropha oil catalyzed by immobilized Burkholderia cepacia lipase on modified attapulgite.

    Science.gov (United States)

    You, Qinghong; Yin, Xiulian; Zhao, Yuping; Zhang, Yan

    2013-11-01

    Lipase from Burkholderia cepacia was immobilized on modified attapulgite by cross-linking reaction for biodiesel production with jatropha oil as feedstock. Effects of various factors on biodiesel production were studied by single-factor experiment. Results indicated that the best conditions for biodiesel preparation were: 10 g jatropha oil, 2.4 g methanol (molar ratio of oil to methanol is 1:6.6) being added at 3h intervals, 7 wt% water, 10 wt% immobilized lipase, temperature 35°C, and time 24h. Under these conditions, the maximum biodiesel yield reached 94%. The immobilized lipase retained 95% of its relative activity during the ten repeated batch reactions. The half-life time of the immobilized lipase is 731 h. Kinetics was studied and the Vmax of the immobilized lipases were 6.823 mmol L(-1). This immobilized lipase catalyzed process has potential industrial use for biodiesel production to replace chemical-catalyzed method.

  11. NOx Catalyzed Pathway of Stratospheric Ozone Depletion: A Coupled Cluster Investigation.

    Science.gov (United States)

    Dutta, Achintya Kumar; Vaval, Nayana; Pal, Sourav

    2012-06-12

    We report a theoretical investigation on the NOx catalyzed pathways of stratospheric ozone depletion using highly accurate coupled cluster methods. These catalytic reactions represent a great challenge to state-of-the-art ab initio methods, while their mechanisms remain unclear to both experimentalists and theoreticians. In this work, we have used the so-called "gold standard of quantum chemistry," the CCSD(T) method, to identify the saddle points on NOx-based reaction pathways of ozone hole formation. Energies of the saddle points are calculated using the multireference variants of coupled cluster methods. The calculated activation energies and rate constants show good agreement with available experimental results. Tropospheric precursors to stratospheric NOx radicals have been identified, and their potential importance in stratospheric chemistry has been discussed. Our calculations resolve previous conflicts between ab initio and experimental results for a trans nitro peroxide intermediate, in the NOx catalyzed pathway of ozone depletion.

  12. Synthesis of phenanthridines via palladium-catalyzed picolinamide-directed sequential C–H functionalization

    Directory of Open Access Journals (Sweden)

    Ryan Pearson

    2013-05-01

    Full Text Available We report a new synthesis of phenanthridines based on palladium-catalyzed picolinamide-directed sequential C–H functionalization reactions starting from readily available benzylamine and aryl iodide precursors. Under the catalysis of Pd(OAc2, the ortho-C–H bond of benzylpicolinamides is first arylated with an aryl iodide. The resulting biaryl compound is then subjected to palladium-catalyzed picolinamide-directed intramolecular dehydrogenative C–H amination with PhI(OAc2 oxidant to form the corresponding cyclized dihydrophenanthridines. The benzylic position of these dihydrophenanthridines could be further oxidized with Cu(OAc2, removing the picolinamide group and providing phenathridine products. The cyclization and oxidation could be carried out in a single step and afford phenathridines in moderate to good yields.

  13. Tris(pentafluorophenyl)borane-Catalyzed Acceptorless Dehydrogenation of N-Heterocycles.

    Science.gov (United States)

    Kojima, Masahiro; Kanai, Motomu

    2016-09-26

    Catalytic acceptorless dehydrogenation is an environmentally benign way to desaturate organic compounds. This process is traditionally accomplished with transition-metal-based catalysts. Herein, a borane-catalyzed, metal-free acceptorless dehydrogenation of saturated N-heterocycles is disclosed. Tris(pentafluorophenyl)borane was identified as a versatile catalyst, which afforded several synthetically important N-heteroarenes in up to quantitative yield. Specifically, the present metal-free catalytic system exhibited a uniquely high tolerance toward sulfur functionalities, and demonstrated superior reactivity in the synthesis of benzothiazoles compared to conventional metal-catalyzed systems. This protocol can thus be regarded as the first example of metal-free acceptorless dehydrogenation in synthetic organic chemistry.

  14. Large-scale ruthenium- and enzyme-catalyzed dynamic kinetic resolution of (rac-1-phenylethanol

    Directory of Open Access Journals (Sweden)

    Bäckvall Jan-E

    2007-12-01

    Full Text Available Abstract The scale-up of the ruthenium- and enzyme-catalyzed dynamic kinetic resolution (DKR of (rac-1-phenylethanol (2 is addressed. The immobilized lipase Candida antarctica lipase B (CALB was employed for the resolution, which shows high enantioselectivity in the transesterification. The ruthenium catalyst used, (η 5-C5Ph5RuCl(CO2 1, was shown to possess very high reactivity in the "in situ" redox racemization of 1-phenylethanol (2 in the presence of the immobilized enzyme, and could be used in 0.05 mol% with high efficiency. Commercially available isopropenyl acetate was employed as acylating agent in the lipase-catalyzed transesterifications, which makes the purification of the product very easy. In a successful large-scale DKR of 2, with 0.05 mol% of 1, (R-1-phenylethanol acetate (3 was obtained in 159 g (97% yield in excellent enantiomeric excess (99.8% ee.

  15. Recent advances in the gold-catalyzed additions to C–C multiple bonds

    Directory of Open Access Journals (Sweden)

    He Huang

    2011-07-01

    Full Text Available C–O, C–N and C–C bonds are the most widespread types of bonds in nature, and are the cornerstone of most organic compounds, ranging from pharmaceuticals and agrochemicals to advanced materials and polymers. Cationic gold acts as a soft and carbophilic Lewis acid and is considered one of the most powerful activators of C–C multiple bonds. Consequently, gold-catalysis plays an important role in the development of new strategies to form these bonds in more convenient ways. In this review, we highlight recent advances in the gold-catalyzed chemistry of addition of X–H (X = O, N, C bonds to C–C multiple bonds, tandem reactions, and asymmetric additions. This review covers gold-catalyzed organic reactions published from 2008 to the present.

  16. Efficient Hydration of Olefins Catalyzed by Wool-Supported Palladium Complex

    Institute of Scientific and Technical Information of China (English)

    Dan-Ni SUI; Si-Qian WANG; Xin WANG; Mei-Yu HUANG; Ying-Yan JIANG

    2005-01-01

    @@ 1Introduction The hydration of olefins is one of the most important prxesses for the production of alcohols[1]. Both transition metal complexes[2] and enzymes[3] have been reported to catalyze the hydration of alkenes, but their catalysts are usually tither unstable or difficult to prepare, expensive and sometimes can not be easily recovered.In our previous papers, some natural biopolymer-metal complexes[4-6] have been used as effective catalysts in hydration to overcome above disadvantages. Recently, wool-Palladium complex(Wool-Pd) has been prepared and found to be able to effficiently catalyze the hydration of olefins to alcohols, such as cinnamyl alcohol(1a) to 1-phenyl-1,3-propanediol(1b), acrylic acid(2a) to lactic acid(2b), 4-vinyl pyridine(3a) to α-methyl-4-pyridinemethanol (3b) and acrylamide(4a) to 1-hydroxyethylamide(4b) respectively in high yields under mild conditions. See scheme 1.

  17. Aza Cope Rearrangement of Propargyl Enammonium Cations Catalyzed By a Self-Assembled `Nanozyme

    Energy Technology Data Exchange (ETDEWEB)

    Hastings, Courntey J.; Fiedler, Dorothea; Bergman, Robert G.; Raymond, Kenneth N.

    2008-02-27

    The tetrahedral [Ga{sub 4}L{sub 6}]{sup 12-} assembly (L = N,N-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene) encapsulates a variety of cations, including propargyl enammonium cations capable of undergoing the aza Cope rearrangement. For propargyl enammonium substrates that are encapsulated in the [Ga{sub 4}L{sub 6}]{sup 12-} assembly, rate accelerations of up to 184 are observed when compared to the background reaction. After rearrangement, the product iminium ion is released into solution and hydrolyzed allowing for catalytic turnover. The activation parameters for the catalyzed and uncatalyzed reaction were determined, revealing that a lowered entropy of activation is responsible for the observed rate enhancements. The catalyzed reaction exhibits saturation kinetics; the rate data obey the Michaelis-Menten model of enzyme kinetics, and competitive inhibition using a non-reactive guest has been demonstrated.

  18. Stem cells catalyze cartilage formation by neonatal articular chondrocytes in 3D biomimetic hydrogels

    Science.gov (United States)

    Lai, Janice H.; Kajiyama, Glen; Smith, Robert Lane; Maloney, William; Yang, Fan

    2013-12-01

    Cartilage loss is a leading cause of disability among adults and effective therapy remains elusive. Neonatal chondrocytes (NChons) are an attractive allogeneic cell source for cartilage repair, but their clinical translation has been hindered by scarce donor availability. Here we examine the potential for catalyzing cartilage tissue formation using a minimal number of NChons by co-culturing them with adipose-derived stem cells (ADSCs) in 3D hydrogels. Using three different co-culture models, we demonstrated that the effects of co-culture on cartilage tissue formation are dependent on the intercellular distance and cell distribution in 3D. Unexpectedly, increasing ADSC ratio in mixed co-culture led to increased synergy between NChons and ADSCs, and resulted in the formation of large neocartilage nodules. This work raises the potential of utilizing stem cells to catalyze tissue formation by neonatal chondrocytes via paracrine signaling, and highlights the importance of controlling cell distribution in 3D matrices to achieve optimal synergy.

  19. Thermodynamics of Enzyme-Catalyzed Reactions: Part 7-2007 Update

    Science.gov (United States)

    Goldberg, Robert N.; Tewari, Yadu B.; Bhat, Talapady N.

    2007-12-01

    This review serves to update previously published evaluations of equilibrium constants and enthalpy changes for enzyme-catalyzed reactions. For each reaction, the following information is given: the reference for the data, the reaction studied, the name of the enzyme used and its Enzyme Commission number, the method of measurement, the conditions of measurement [temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used], the data and their evaluation, and, sometimes, commentary on the data and on any corrections which have been applied to the data or any calculations for which the data have been used. The review contains data from 119 references which have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is also a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  20. Thermodynamics of Enzyme-Catalyzed Reactions: Part 6--1999 Update

    Science.gov (United States)

    Goldberg, Robert N.

    1999-07-01

    This review serves to update previously published evaluations of equilibrium constants and enthalpy changes for enzyme-catalyzed reactions. For each reaction the following information is given: the reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement [temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used]; the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it or any calculations for which the data have been used. The data from 96 references have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is also a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  1. Thermodynamics of Enzyme-Catalyzed Reactions: Part 5. Isomerases and Ligases

    Science.gov (United States)

    Goldberg, Robert N.; Tewari, Yadu B.

    1995-11-01

    Equilibrium constants and enthalpy changes for reactions catalyzed by the isomerase and ligase classes of enzymes have been compiled. For each reaction the following information is given: the reference for the data; the reaction studied; the name of the enzyme used and its Enzyme Commission number; the method of measurement; the conditions of measurement (temperature, pH, ionic strength, and the buffer(s) and cofactor(s) used); the data and an evaluation of it; and, sometimes, commentary on the data and on any corrections which have been applied to it or any calculations for which the data have been used. The data from 176 references have been examined and evaluated. Chemical Abstract Service registry numbers are given for the substances involved in these various reactions. There is a cross reference between the substances and the Enzyme Commission numbers of the enzymes used to catalyze the reactions in which the substances participate.

  2. Single wire radial junction photovoltaic devices fabricated using aluminum catalyzed silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ke, Y; Weng, X J; Kendrick, C E; Eichfeld, S M; Redwing, J M [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park, PA 16802 (United States); Wang, X; Yu, Y A; Yoon, H P; Mayer, T S [Department of Electrical Engineering, Materials Research Institute, Pennsylvania State University, University Park, PA 16802 (United States); Habib, Y M, E-mail: jmr31@psu.edu, E-mail: tsm2@psu.edu [Illuminex Corp., Lancaster, PA 17601 (United States)

    2011-11-04

    Single nanowire radial junction solar cell devices were fabricated using Si nanowires synthesized by Al-catalyzed vapor-liquid-solid growth of the p{sup +} core (Al auto-doping) and thin film deposition of the n{sup +}-shell at temperatures below 650 deg. C. Short circuit current densities of {approx} 11.7 mA cm{sup -2} were measured under 1-sun AM1.5G illumination, showing enhanced optical absorption. The power conversion efficiencies were limited to < 1% by the low open circuit voltage and fill factor of the devices, which was attributed to junction shunt leakage promoted by the high p{sup +}/n{sup +} doping. This demonstration of a radial junction device represents an important advance in the use of Al-catalyzed Si nanowire growth for low cost photovoltaics.

  3. CF₃I synthesis catalyzed by activated carbon: a density functional theory study.

    Science.gov (United States)

    Hu, Yingjie; Wu, Taiping; Liu, Weizhou; Zhang, Liyang; Pan, Renming

    2014-03-13

    A revised reaction mechanism of CF3I synthesis catalyzed by activated carbon is investigated with quantum chemistry methods using density functional theory (DFT). The adsorption configurations of possible intermediates are carefully examined. The reaction pathway and related transition states are also analyzed. According to our calculations, first, the dehydrofluorination of CHF3 is catalyzed by -COOH groups, which possesses the highest barrier and is accordingly identified as the rate-determining step. Second, the difluorocarbene disproportionation over graphite (001) surface proceeds instead of dimerization. The next reaction steps involving the association of fluoromethine and trifluoromethyl, the fluorine abstractions between intermediates and the iodine abstractions by the desorbed CF3 and CF2CF3 from molecular iodine are also feasible over graphite (001) surfaces. It is also found that the coke deposition in experiments is due to the fluorine abstraction from fluoromethine. This revised mechanism is in agreement with available experimental data and our theoretical computations.

  4. Kinetics of non-catalyzed hydrolysis of tannin in high temperature liquid water

    Institute of Scientific and Technical Information of China (English)

    Li-li LU; Xiu-yang LU; Nan MA

    2008-01-01

    High temperature liquid water (HTLW) has drawn increasing attention as an environmentally benign medium for organic chemical reactions,especially acid-/base-catalyzed reactions.Non-catalyzed hydrolyses of gallotannin and tara tannin in HTLW for the simultaneous preparation of gallic acid (GA) and pyrogallol (PY) are under investigation in our laboratory.In this study,the hydrolysis kinetics of gallotannin and tara tannin were determined.The reaction is indicated to be a typical consecutive first-order one in which GA has formed as a main intermediate and PY as the final product.Selective decomposition of tannin in HTLW was proved to be possible by adjusting reaction temperature and time.The present results provide an important basic data and reference for the green preparation of GA and PY.

  5. Three enzymatic activities catalyze the oxidation of sulfide to thiosulfate in mammalian and invertebrate mitochondria.

    Science.gov (United States)

    Hildebrandt, Tatjana M; Grieshaber, Manfred K

    2008-07-01

    Hydrogen sulfide is a potent toxin of aerobic respiration, but also has physiological functions as a signalling molecule and as a substrate for ATP production. A mitochondrial pathway catalyzing sulfide oxidation to thiosulfate in three consecutive reactions has been identified in rat liver as well as in the body-wall tissue of the lugworm, Arenicola marina. A membrane-bound sulfide : quinone oxidoreductase converts sulfide to persulfides and transfers the electrons to the ubiquinone pool. Subsequently, a putative sulfur dioxygenase in the mitochondrial matrix oxidizes one persulfide molecule to sulfite, consuming molecular oxygen. The final reaction is catalyzed by a sulfur transferase, which adds a second persulfide from the sulfide : quinone oxidoreductase to sulfite, resulting in the final product thiosulfate. This role in sulfide oxidation is an additional physiological function of the mitochondrial sulfur transferase, rhodanese.

  6. CLAY CATALYZED SYNTHESIS OF BIO-DEGRADABLE POLY(GLYCOLIC ACID)

    Institute of Scientific and Technical Information of China (English)

    K. Durai Murugan; S. Radhika; I. Baskaran; R. Anbarasan

    2008-01-01

    Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay. The added clay catalyzed the condensation polymerization which can be confirmed by recording FT1R spectroscopy and intrinsic viscosity (Ⅳ) values. The relative intensity of C =O/CH is increased while increasing the amount of clay. DSC showed the appearance of multiple endotherms of poly(glycolic acid). TGA showed the percentage weight residue remain above 750℃ for polymer-nano composite system was 21% and hence proved the flame retardancy (char forming) nature. TEM confirmed the nano size of the clay used to catalyze the condensation reaction. The intrinsic viscosity value was increased with the increase of percentage weight of Hectorite type clay.

  7. Autoinduced catalysis and inverse equilibrium isotope effect in the frustrated Lewis pair catalyzed hydrogenation of imines.

    Science.gov (United States)

    Tussing, Sebastian; Greb, Lutz; Tamke, Sergej; Schirmer, Birgitta; Muhle-Goll, Claudia; Luy, Burkhard; Paradies, Jan

    2015-05-26

    The frustrated Lewis pair (FLP)-catalyzed hydrogenation and deuteration of N-benzylidene-tert-butylamine (2) was kinetically investigated by using the three boranes B(C6F5)3 (1), B(2,4,6-F3-C6H2)3 (4), and B(2,6-F2-C6H3)3 (5) and the free activation energies for the H2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol(-1)) for the H2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect.

  8. Nucleation and initial radius of self-catalyzed III-V nanowires

    Science.gov (United States)

    Dubrovskii, V. G.; Borie, S.; Dagnet, T.; Reynes, L.; André, Y.; Gil, E.

    2017-02-01

    We treat theoretically the initial nucleation step of self-catalyzed III-V nanowires under simultaneously deposited group III and V vapor fluxes and with surface diffusion of a group III element. Our model is capable of describing the droplet size at which the very first nanowire monolayer nucleates depending on the element fluxes and surface temperature. This size determines the initial nanowire radius in growth techniques without pre-deposition of gallium. We show that useful self-catalyzed III-V nanowires can form only under the appropriately balanced V/III flux ratios and temperatures. Such balance is required to obtain nucleation from reasonably sized droplets that are neither too small under excessive arsenic flux nor too large in the arsenic-poor conditions.

  9. A General Palladium-Catalyzed Hiyama Cross-Coupling Reaction of Aryl and Heteroaryl Chlorides.

    Science.gov (United States)

    Yuen, On Ying; So, Chau Ming; Man, Ho Wing; Kwong, Fuk Yee

    2016-05-01

    A general palladium-catalyzed Hiyama cross-coupling reaction of aryl and heteroaryl chlorides with aryl and heteroaryl trialkoxysilanes by a Pd(OAc)2 /L2 catalytic system is presented. A newly developed water addition protocol can dramatically improve the product yields. The conjugation of the Pd/L2 system and the water addition protocol can efficiently catalyze a broad range of electron-rich, -neutral, -deficient, and sterically hindered aryl chlorides and heteroaryl chlorides with excellent yields within three hours and the catalyst loading can be down to 0.05 mol % Pd for the first time. Hiyama coupling of heteroaryl chlorides with heteroaryl silanes is also reported for the first time. The reaction can be easily scaled up 200 times (100 mmol) without any degasification and purification of reactants; this facilitates the practical application in routine synthesis.

  10. Using Thin Film Targets for Muonic Atoms and Muon Catalyzed Fusion Studies

    CERN Document Server

    Fujiwara, M C; Bailey, J M; Beer, G A; Beveridge, J L; Faifman, M P; Huber, T M; Kammel, P; Kim, S K; Knowles, P E; Kunselman, A R; Markushin, V E; Marshall, G M; Martoff, C J; Mason, G R; Mulhauser, F; Olin, A; Petitjean, C; Porcelli, T A; Zmeskal, J

    2000-01-01

    Studies of muonic atoms and muon catalyzed fusion have been conventionally done in a bulk target of gas, liquid or solid hydrogen isotopes. The use of thin film targets developed at TRIUMF have notable advantages in tackling some of the most important questions in the field, which could be further exploited at future high intensity muon sources. We review the technique of the thin film method with emphasis on recent results and a future proposal.

  11. Novel Role of Carbon Dioxide as a Selective Agent in Palladium-Catalyzed Cyclotrimerization of Alkynes

    Institute of Scientific and Technical Information of China (English)

    李金恒; 谢叶香

    2004-01-01

    Carbon dioxide was found as a selective agent to promote the palladium-catalyzed cyclotrimerization of alkynes in water. Both aryl and alkylacetylenes afforded the corresponding cyclotrimerization products regioselectively in high yields using PdCl2, CuCl2, and CO2 as the catalytic system. However, tert-butylacetylene bearing a bulky group gave a dimerization product. Mechanism of this reaction was also discussed.

  12. Cu(II)-catalyzed transformation of benzylpenicillin revisited: the overlooked oxidation.

    Science.gov (United States)

    Chen, Jiabin; Sun, Peizhe; Zhou, Xuefei; Zhang, Yalei; Huang, Ching-Hua

    2015-04-07

    Penicillins, a class of widely used β-lactam antibiotics, are known to be susceptible to catalyzed hydrolysis by metal ions such as Cu(II). However, new results in this study strongly indicate that the role of Cu(II) is not merely a hydrolysis catalyst but also an oxidant. When benzylpenicillin (i.e., penicillin G (PG)) was exposed to Cu(II) ion at an equal molar ratio and pH 7, degradation of PG occurred rapidly in the oxygen-rich solution but gradually slowed down to a halt in the oxygen-limited solution. In-depth studies revealed that Cu(II) catalyzed hydrolysis of PG to benzylpenicilloic acid (PA) and oxidized PA to yield phenylacetamide and other products. The availability of oxygen played the role in reoxidizing Cu(I) back to Cu(II), which sustained fast degradation of PG over time. The overall reaction was also influenced by pH, with Cu(II)-catalyzed hydrolysis of PG occurring throughout pH 5, 7 and 9, while Cu(II) oxidation of PA occurring at pH 7 and 9. Note that the potential of Cu(II) to oxidize penicillins was largely overlooked in the previous literature, and catalyzed hydrolysis was frequently assumed as the only reaction. This study is among the first to identify the dual roles of Cu(II) in the entire degradation process of PG and systematically investigate the overlooked oxidation reaction to elucidate the mechanism. The new mechanistic knowledge has important implications for many other β-lactam antibiotics for their interactions with Cu(II), and significantly improves the ability to predict the environmental fate and transformation products of PG and related penicillins in systems where Cu(II) species are also present.

  13. Secologanin synthase which catalyzes the oxidative cleavage of loganin into secologanin is a cytochrome P450.

    Science.gov (United States)

    Yamamoto, H; Katano, N; Ooi, A; Inoue, K

    2000-01-01

    Secologanin synthase, an enzyme catalyzing the oxidative cleavage of the cyclopentane ring in loganin to form secologanin, was detected in microsomal preparations from cell suspension cultures of Lonicera japonica. The reaction required NADPH and molecular oxygen, and was blocked by carbon monoxide as well as by several other cytochrome P450 inhibitors, indicating that the reaction was mediated by cytochrome P450. Of the substrates examined, only specificity for loganin was demonstrated. A possible reaction mechanism is described.

  14. Palladium-Catalyzed Suzuki-Miyaura Type Coupling Reaction of Aryl Halides with Triphenylborane-Pyridine

    Institute of Scientific and Technical Information of China (English)

    杨明华; 顾勇冰; 王艳; 赵玺玉; 严国兵

    2012-01-01

    The Suzuki-Miyaura type coupling reaction of aryl halides with triphenylborane-pyridine was described. The reaction can be catalyzed by Pd(OAc)2 (5 mol%) in presence of Cs2CO3 at 50 ℃ or 80 ℃, and functionalized biaryls were obtained in good to excellent yields. This protocol is general and can tolerate a wide range of func- tional groups.

  15. Rhodium-catalyzed intramolecular hydroarylation of 1-halo-1-alkynes: regioselective synthesis of semihydrogenated aromatic heterocycles.

    Science.gov (United States)

    Murase, Hirohiko; Senda, Kousuke; Senoo, Masato; Hata, Takeshi; Urabe, Hirokazu

    2014-01-03

    The regioselective intramolecular hydroarylation of (3-halo-2-propynyl)anilines, (3-halo-2-propynyl) aryl ethers, or (4-halo-3-butynyl) aryl ethers was efficiently catalyzed by Rh2(OCOCF3)4 to give semihydrogenated aromatic heterocycles, such as 4-halo-1,2-dihydroquinolines, 4-halo-3-chromenes, or 4-(halomethylene)chromans, in good to excellent yields. Some synthetic applications taking advantage of the halo-substituents of the products are also illustrated.

  16. Gold-catalyzed formation of heterocycles - an enabling new technology for medicinal chemistry.

    Science.gov (United States)

    Shen, Hong C; Graham, Thomas H

    2013-01-01

    Gold-catalyzed transformations allow efficient access to a wide scope of heterocyclic structures that serve as building blocks and pharmacophores in medicinal chemistry. Compared with other transition metal and Lewis acid catalysis, gold catalysis presents mechanistic divergence, excellent functional group tolerance and/or operational advantages. Emergent applications of gold catalysis have played a key role in the synthesis of biologically active molecules including a drug candidate.

  17. Biocatalysts for cascade reaction: porcine pancreas lipase (PPL)-catalyzed synthesis of bis(indolyl)alkanes.

    Science.gov (United States)

    Xiang, Ziwei; Liu, Zhiqiang; Chen, Xiang; Wu, Qi; Lin, XianFu

    2013-10-01

    A cascade reaction between aldehydes and indole catalyzed by lipase from porcine pancreas Type II (PPL) in solvent mixture at 50 °C was reported for the first time. Some control experiments had been designed to demonstrate that the PPL was responsible for the cascade reaction. After the optimization of the stepwise process, a series of bis(indolyl)alkanes were prepared in moderate to excellent yields under the catalysis of PPL.

  18. Asymmetric Michael Addition of Activated Alkenes to Nitro Alkenes Catalyzed by Organic Catalyst

    Institute of Scientific and Technical Information of China (English)

    XUE Dong; CHEN Yong-Chun; CUI Xin; WANG Qi-Wei; ZHU Jin; DENG Jin-Gen

    2003-01-01

    @@ Enantioselective Michael addition is one of the most powerfulbond-forming reaction in organic synthesis. [1] A mong the Michael acceptors, nitro alkenes are very attractive, because the nitro group is the most electron-withdrawing group known and it can serve as masked functionality to be further transformed after the addition has taken place. [2] Recently, asymmetric Michael reactions catalyzed by organic catalyst have draw much attention.[3

  19. Small Peptides Catalyzed Direct Aldol Reactions of Aldehydes with Hydroxyacetone with Regiocontrol in Aqueous Media

    Institute of Scientific and Technical Information of China (English)

    TANG,Zhuo; YANG,Zhi-Hua; CUN,Lin-Feng; GONG,Liu-Zhu; MI,Ai-Qiao; JIANG,Yao-Zhong

    2004-01-01

    @@ Very recently, we[1] found that L-proline amides and dipeptides acted as efficient catalysts for the asymmetric direct aldol reaction. We report here that L-proline-based peptides 1~5 can catalyze the aldol reactions of hydroxyacetone with aldehydes 6 in aqueous media, to give 1,4-diols (7), the disfavored products with either aldolase or L-proline. Both peptides 3 and 4 give good results.

  20. Ruthenium(III Chloride Catalyzed Acylation of Alcohols, Phenols, and Thiols in Room Temperature Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Mingzhong Cai

    2009-09-01

    Full Text Available Ruthenium(III chloride-catalyzed acylation of a variety of alcohols, phenols, and thiols was achieved in high yields under mild conditions (room temperature in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]. The ionic liquid and ruthenium catalyst can be recycled at least 10 times. Our system not only solves the basic problem of ruthenium catalyst reuse, but also avoids the use of volatile acetonitrile as solvent.

  1. Rhodium-Catalyzed Linear Codimerization and Cycloaddition of Ketenes with Alkynes

    Directory of Open Access Journals (Sweden)

    Teruyuki Kondo

    2010-06-01

    Full Text Available A novel rhodium-catalyzed linear codimerization of alkyl phenyl ketenes with internal alkynes to dienones and a novel synthesis of furans by an unusual cycloaddition of diaryl ketenes with internal alkynes have been developed. These reactions proceed smoothly with the same rhodium catalyst, RhCl(PPh33, and are highly dependent on the structure and reactivity of the starting ketenes.

  2. Papain-Catalyzed Synthesis of Polyglutamate Containing a Nylon Monomer Unit

    OpenAIRE

    Kenjiro Yazawa; Keiji Numata

    2016-01-01

    Peptides have the potential to serve as an alternative for petroleum-based polymers to support a sustainable society. However, they lack thermoplasticity, owing to their strong intermolecular interactions. In contrast, nylon is famous for its thermoplasticity and chemical resistance. Here, we synthesized peptides containing a nylon unit to modify their thermal properties by using papain-catalyzed chemoenzymatic polymerization. We used l-glutamic acid alkyl ester as the amino acid monomer and ...

  3. Oxidation of chlorophenols catalyzed by Coprinus cinereus peroxidase with in situ production of hydrogen peroxide.

    Science.gov (United States)

    Pezzotti, Fabio; Okrasa, Krzysztof; Therisod, Michel

    2004-01-01

    Degradation of 2,6-dichlorophenol (2,6-DCP) was accomplished by oxidation catalyzed by Coprinus cinereus peroxidase. Immobilization of the enzyme in a polyacrylamide matrix enhanced DCP oxidation. Hydrogen peroxide, peroxidase's natural substrate, was produced enzymatically in situ to avoid peroxidase inactivation by its too high concentration. In the case of larger scale utilization, the method would also avoid direct handling of this hazardous reagent.

  4. The intriguing modeling of cis–trans selectivity in ruthenium-catalyzed olefin metathesis

    Directory of Open Access Journals (Sweden)

    Luigi Cavallo

    2011-01-01

    Full Text Available In this study we have investigated computationally the origin of the cis–trans selectivity in the Ru-catalyzed cross metathesis (CM of a prototype monosubstituted olefin, i.e., propene. Our calculations suggest that the origin of the preferential formation of trans-olefins is in the product release step, which prevents the initially formed cis-olefin from escaping the metal, and returns it to the reaction pool until the trans-olefin is formed.

  5. The intriguing modeling of cis–trans selectivity in ruthenium-catalyzed olefin metathesis

    Science.gov (United States)

    Bahri-Laleh, Naeimeh; Credendino, Raffaele

    2011-01-01

    Summary In this study we have investigated computationally the origin of the cis–trans selectivity in the Ru-catalyzed cross metathesis (CM) of a prototype monosubstituted olefin, i.e., propene. Our calculations suggest that the origin of the preferential formation of trans-olefins is in the product release step, which prevents the initially formed cis-olefin from escaping the metal, and returns it to the reaction pool until the trans-olefin is formed. PMID:21286393

  6. Ruthenium-Catalyzed Olefin Metathesis after Tetra-n-butylammonium Fluoride-Mediated Desilylation

    Science.gov (United States)

    Osman, Sami

    2012-01-01

    One-pot procedures expedite organic synthesis but pose challenges in that many reagents must be compatible with each other. We discovered that the presence of nBu4NF hindered rutheniumcatalyzed olefin metathesis when nBu4NF-mediated desilylation and olefin metathesis were performed in one pot. This problem could be solved by the addition of (TMS)2O to remove fluoride anions in order to facilitate the ruthenium-catalyzed olefin metathesis. PMID:23269856

  7. Copper-catalyzed intermolecular oxyamination of olefins using carboxylic acids and O-benzoylhydroxylamines

    Directory of Open Access Journals (Sweden)

    Brett N. Hemric

    2016-01-01

    Full Text Available This paper reports a novel approach for the direct and facile synthesis of 1,2-oxyamino moieties via an intermolecular copper-catalyzed oxyamination of olefins. This strategy utilizes O-benzoylhydroxylamines as an electrophilic amine source and carboxylic acids as a nucleophilic oxygen source to achieve a modular difunctionalization of olefins. The reaction proceeded in a regioselective manner with moderate to good yields, exhibiting a broad scope of carboxylic acid, amine, and olefin substrates.

  8. Highly Efficient and Versatile Acetalization of Glycol Catalyzed by Cupric p-Toluenesulfonate

    Institute of Scientific and Technical Information of China (English)

    LIU,Cai-Hua; YU,Xin-Yu; LIANG,Xue-Zheng; WANG,Wen-Juan; YANG,Jian-Guo; HE,Ming-Yuan

    2007-01-01

    Acetalization of glycol with carbonyl compounds was carried out catalyzed by cupric p-toluenesulfonate. These carbonyl compounds included cyclohexanone, propionoaldehyde, n-butyraldehyde, iso-butyraldehyde, n-valeraldehyde, benzaldehyde and butanone. Satisfactory results were obtained: the conversions of these carbonyl compounds were more than 90%, the selectivities were higher than 99.1%, only 0.1% mole ratio of catalyst to substrate and 90 min were sufficient in most cases. The catalyst and products were separated easily by phase separation.

  9. Enantioselective aldol reaction between isatins and cyclohexanone catalyzed by amino acid sulphonamides.

    Science.gov (United States)

    Wang, Jun; Liu, Qi; Hao, Qing; Sun, Yanhua; Luo, Yiming; Yang, Hua

    2015-04-01

    Sulphonamides derived from primary α-amino acid were successfully applied to catalyze the aldol reaction between isatin and cyclohexanone under neat conditions. More interestingly, molecular sieves, as privileged additives, were found to play a vital role in achieving high enantioselectivity. Consequently, high yields (up to 99%) along with good enantioselectivities (up to 92% ee) and diastereoselectivities (up to 95:5 dr) were obtained. In addition, this reaction was also conveniently scaled up, demonstrating the applicability of this protocol.

  10. Novel chiral ionic liquid (CIL) assisted selectivity enhancement to (L)-proline catalyzed asymmetric aldol reactions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Long; Zhang, Haibo; Luo, Huadong; Zhou, Xiaohai; Cheng, Gongzhen [College of Chemistry, Wuhan University (China)

    2011-09-15

    A significant improvement of the chemical yields (up to 88%), stereoselectivity (> 99:1) and enantiomeric excesses (up to 98%) of (L)-proline catalyzed direct asymmetric aldol reaction was found when proline based chiral ionic liquids (CILs) were added as additives. Different ratios of DMSO/H{sub 2}O as solvent and chiral ionic liquids (CILs) with chiral cations of different chain length were investigated. (author)

  11. Precision Synthesis of Functional Polysaccharide Materials by Phosphorylase-Catalyzed Enzymatic Reactions

    Directory of Open Access Journals (Sweden)

    Jun-ichi Kadokawa

    2016-04-01

    Full Text Available In this review article, the precise synthesis of functional polysaccharide materials using phosphorylase-catalyzed enzymatic reactions is presented. This particular enzymatic approach has been identified as a powerful tool in preparing well-defined polysaccharide materials. Phosphorylase is an enzyme that has been employed in the synthesis of pure amylose with a precisely controlled structure. Similarly, using a phosphorylase-catalyzed enzymatic polymerization, the chemoenzymatic synthesis of amylose-grafted heteropolysaccharides containing different main-chain polysaccharide structures (e.g., chitin/chitosan, cellulose, alginate, xanthan gum, and carboxymethyl cellulose was achieved. Amylose-based block, star, and branched polymeric materials have also been prepared using this enzymatic polymerization. Since phosphorylase shows a loose specificity for the recognition of substrates, different sugar residues have been introduced to the non-reducing ends of maltooligosaccharides by phosphorylase-catalyzed glycosylations using analog substrates such as α-d-glucuronic acid and α-d-glucosamine 1-phosphates. By means of such reactions, an amphoteric glycogen and its corresponding hydrogel were successfully prepared. Thermostable phosphorylase was able to tolerate a greater variance in the substrate structures with respect to recognition than potato phosphorylase, and as a result, the enzymatic polymerization of α-d-glucosamine 1-phosphate to produce a chitosan stereoisomer was carried out using this enzyme catalyst, which was then subsequently converted to the chitin stereoisomer by N-acetylation. Amylose supramolecular inclusion complexes with polymeric guests were obtained when the phosphorylase-catalyzed enzymatic polymerization was conducted in the presence of the guest polymers. Since the structure of this polymeric system is similar to the way that a plant vine twines around a rod, this polymerization system has been named

  12. Diastereoselective B(C6F5)3-Catalyzed Reductive Carbocyclization of Unsaturated Carbohydrates.

    Science.gov (United States)

    Bender, Trandon A; Dabrowski, Jennifer A; Zhong, Hongyu; Gagné, Michel R

    2016-08-19

    A B(C6F5)3-catalyzed method for the selective conversion of unsaturated carbohydrates to cyclopentanes and cyclopropanes is disclosed. Catalyst activation of tertiary silanes generates the ion pair [(C6F5)3B-H][ROSi2] whose components synergistically activate C-O bonds for diastereoselective C-C bond formation. Sila-THF cations are invoked as key intermediates facilitating carbocyclizations. Complex chiral synthons are thereby obtained in a single pot.

  13. Recyclable Polystyrene-Supported Siloxane-Transfer Agent for Palladium-Catalyzed Cross-Coupling Reactions

    Science.gov (United States)

    2015-01-01

    The rational design, synthesis, and validation of a significantly improved insoluble polymer-supported siloxane-transfer agent has been achieved that permits efficient palladium-catalyzed cross-coupling reactions. The cross-linked polystyrene support facilitates product purification with excellent siloxane recycling. Drawbacks of a previous polymer-supported siloxane-transfer agent, relating to reaction efficiency and polymer stability after repeated cycles, have been addressed. PMID:24661113

  14. Microwave-enhanced transition metal-catalyzed decoration of 2(1H)-pyrazinone scaffolds.

    Science.gov (United States)

    Kaval, Nadya; Bisztray, Katalin; Dehaen, Wim; Kappe, C Oliver; Van der Eycken, Erik

    2003-01-01

    The 2(1H)-pyrazinones have been demonstrated to be versatile building blocks for the synthesis of biologically active compounds. Here, an efficient method is described for the decoration of these interesting scaffolds. Microwave-assisted palladium catalyzed reactions allow the easy introduction of different substituents at the C3- and even at the rather unreactive C5-position of the pyrazinones. Stille, Suzuki, Heck, Sonogashira reactions, in addition to reductive dechlorinations, and cyanation reactions are investigated.

  15. Why You Really Should Consider Using Palladium-Catalyzed Cross-Coupling of Silanols and Silanolates

    OpenAIRE

    Denmark, Scott E; Ambrosi, Andrea

    2015-01-01

    The transition metal-catalyzed cross-coupling of organometallic nucleophiles derived from tin, boron, and zinc with organic electrophiles enjoys a preeminent status among modern synthetic methods for the formation of carbon-carbon bonds. In recent years, organosilanes have emerged as viable alternatives to the conventional reagents, with the added benefits of low cost, low toxicity and high chemical stability. However, silicon-based cross-coupling reactions often require heating in the presen...

  16. Iridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with secondary amine nucleophiles

    Directory of Open Access Journals (Sweden)

    Dingqiao Yang

    2009-10-01

    Full Text Available Iridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with various aliphatic and aromatic secondary amines are reported for the first time. The reaction gave the corresponding trans-1,2-dihydronaphthalenol derivatives in good yields with moderate enantioselectivities in the presence of 2.5 mol % [Ir(CODCl]2 and 5 mol % bisphosphine ligand (S-p-Tol-BINAP. The trans-configuration of 3f was confirmed by X-ray crystallography.

  17. Cu2+-Catalyzed Oscillatory Oxidation of Ascorbic Acid by O2 Flow

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel heterogeneous oscillator, the Cu2+-catalyzed oscillatory oxidation of ascorbic acid (Vitamin C) in aqueous solution by O2 flow was reported. Both the potential oscillations on Pt-electrode corresponding to [Cu2+] and the absorbance oscillations at l=260 nm corresponding to [ascorbic acid] were observed. Oscillations in the completely homogeneous system were also observed. Effects of several factors on the oscillations were investigated.

  18. On the Brønsted acid-catalyzed homogeneous hydrolysis of furans.

    Science.gov (United States)

    Nikbin, Nima; Caratzoulas, Stavros; Vlachos, Dionisios G

    2013-11-01

    Furan affairs: Electronic structure calculations of the homogeneous Brønsted acid-catalyzed hydrolysis of 2,5-dimethylfuran show that proton transfer to the β-position is rate-limiting and provides support that the hydrolysis follows general acid catalysis. By means of projected Fukui indices, we show this to be the case for unsubstituted, 2-, and 2,5-substituted furans with electron-donating groups.

  19. Rh(Ⅰ)-Catalyzed Reaction of Trifluoromethylketone N-Tosylhydrazones and Arylboronates

    Institute of Scientific and Technical Information of China (English)

    Zhikun Zhang; Weizhi Yu; Qi Zhou; Tianjiao Li; Yan Zhang; Jianbo Wang

    2016-01-01

    Rh(Ⅰ)-Catalyzed synthesis of l,l-difluoro-2,2-diarylalkenes from trifluoromethylketone N-tosylhydrazones and arylboronates is presented in this communication.This new synthetic method is based on the Rh(Ⅰ)-carbene migratory insertion followed by β-fluoride elimination.In one particular case the protonation occurs instead ofβ-fluoride elimination,affording 2,2-diaryl trifluoroethane product.

  20. Photoredox-Catalyzed Ketyl–Olefin Coupling for the Synthesis of Substituted Chromanols

    KAUST Repository

    Fava, Eleonora

    2016-07-21

    A visible light photoredox-catalyzed aldehyde olefin cyclization is reported. The method represents a formal hydroacylation of alkenes and alkynes and provides chromanol derivatives in good yields. The protocol takes advantage of the double role played by trialkylamines (NR3) which act as (i) electron donors for reducing the catalyst and (ii) proton donors to activate the substrate via a proton-coupled electron transfer. © 2016 American Chemical Society.

  1. Iron-Catalyzed Regioselective Transfer Hydrogenative Couplings of Unactivated Aldehydes with Simple Alkenes.

    Science.gov (United States)

    Zheng, Yan-Long; Liu, Yan-Yao; Wu, Yi-Mei; Wang, Yin-Xia; Lin, Yu-Tong; Ye, Mengchun

    2016-05-17

    An FeBr3 -catalyzed reductive coupling of various aldehydes with alkenes that proceeds through a direct hydride transfer pathway has been developed. With (i) PrOH as the hydrogen donor under mild conditions, previously challenging coupling reactions of unactivated alkyl and aryl aldehydes with simple alkenes, such as styrene derivatives and α-olefins, proceeded smoothly to furnish a diverse range of functionalized alcohols with complete linear regioselectivity.

  2. Advances in Metal-Catalyzed Cross-Coupling Reactions of Halogenated Quinazolinones and Their Quinazoline Derivatives

    Directory of Open Access Journals (Sweden)

    Malose Jack Mphahlele

    2014-10-01

    Full Text Available Halogenated quinazolinones and quinazolines are versatile synthetic intermediates for the metal-catalyzed carbon–carbon bond formation reactions such as the Kumada, Stille, Negishi, Sonogashira, Suzuki-Miyaura and Heck cross-coupling reactions or carbon-heteroatom bond formation via the Buchwald-Hartwig cross-coupling to yield novel polysubstituted derivatives. This review presents an overview of the application of these methods on halogenated quinazolin-4-ones and their quinazolines to generate novel polysubstituted derivatives.

  3. Formation of Linear Polyenes in Thermal Dehydration of Polyvinyl Alcohol, Catalyzed by Phosphotungstic Acid

    Science.gov (United States)

    Tretinnikov, O. N.; Sushko, N. I.

    2015-01-01

    In order to obtain linear polyenes in polyvinyl alcohol films via acid-catalyzed thermal dehydration of the polyvinyl alcohol, we used phosphotungstic acid as the catalyst: a safe and heat-stable solid chemical compound. We established that phosphotungstic acid, introduced as solid nanoparticles into polyvinyl alcohol films, is a more effective dehydration catalyst than hydrochloric acid, since in contrast to HCl it does not evaporate from the film during heat treatment.

  4. Palladium-catalyzed 1,4-difunctionalization of butadiene to form skipped polyenes.

    Science.gov (United States)

    McCammant, Matthew S; Liao, Longyan; Sigman, Matthew S

    2013-03-20

    A palladium-catalyzed 1,4-addition across the commodity chemical 1,3-butadiene to afford skipped polyene products is reported. Through a palladium σ → π → σ allyl isomerization, two new carbon-carbon bonds are formed with high regioselectivity and trans stereoselectivity of the newly formed alkene. The utility of this method is highlighted by the successful synthesis of the ripostatin A skipped triene core.

  5. Heterogeneous Palladium Chloride Catalyzed Ligand-free Suzuki-Miyaura Coupling Reactions at Ambient Temperature

    Institute of Scientific and Technical Information of China (English)

    WANG Min; WANG Lei

    2008-01-01

    A mild and efficient ligand-free Suzuki-Miyaura coupling reaction catalyzed by heterogeneous palladium chloride was developed at room temperature in a short reaction time under air atmosphere.Various phenyl iodides,bromides and activated chlorides were coupled with sodium tetraphenylborate or phenylboronic acids efficiently to afford the corresponding cross-coupled products in good to excellent yields.Furthermore,the catalyst could be recycled up to four times without loss of its activity.

  6. Reversibility of Noble Metal-Catalyzed Aprotic Li-O₂ Batteries.

    Science.gov (United States)

    Ma, Shunchao; Wu, Yang; Wang, Jiawei; Zhang, Yelong; Zhang, Yantao; Yan, Xinxiu; Wei, Yang; Liu, Peng; Wang, Jiaping; Jiang, Kaili; Fan, Shoushan; Xu, Ye; Peng, Zhangquan

    2015-12-01

    The aprotic Li-O2 battery has attracted a great deal of interest because, theoretically, it can store far more energy than today's batteries. Toward unlocking the energy capabilities of this neotype energy storage system, noble metal-catalyzed high surface area carbon materials have been widely used as the O2 cathodes, and some of them exhibit excellent electrochemical performances in terms of round-trip efficiency and cycle life. However, whether these outstanding electrochemical performances are backed by the reversible formation/decomposition of Li2O2, i.e., the desired Li-O2 electrochemistry, remains unclear due to a lack of quantitative assays for the Li-O2 cells. Here, noble metal (Ru and Pd)-catalyzed carbon nanotube (CNT) fabrics, prepared by magnetron sputtering, have been used as the O2 cathode in aprotic Li-O2 batteries. The catalyzed Li-O2 cells exhibited considerably high round-trip efficiency and prolonged cycle life, which could match or even surpass some of the best literature results. However, a combined analysis using differential electrochemical mass spectrometry and Fourier transform infrared spectroscopy, revealed that these catalyzed Li-O2 cells (particularly those based on Pd-CNT cathodes) did not work according to the desired Li-O2 electrochemistry. Instead the presence of noble metal catalysts impaired the cells' reversibility, as evidenced by the decreased O2 recovery efficiency (the ratio of the amount of O2 evolved during recharge/that consumed in the preceding discharge) coupled with increased CO2 evolution during charging. The results reported here provide new insights into the O2 electrochemistry in the aprotic Li-O2 batteries containing noble metal catalysts and exemplified the importance of the quantitative assays for the Li-O2 reactions in the course of pursuing truly rechargeable Li-O2 batteries.

  7. A novel copper-catalyzed reductive coupling of N-tosylhydrazones with H-phosphorus oxides.

    Science.gov (United States)

    Wu, Lei; Zhang, Xio; Chen, Qing-Qing; Zhou, An-Kun

    2012-10-21

    We report here a novel C(sp(3))-P bonds formation via copper-catalyzed reductive coupling of N-tosylhydrazones with H-phosphorus oxides. A variety of aliphatic and aromatic substrates bearing electron-rich and electron-deficient substituents affords phosphine oxide derivatives with moderate to good yields. This work suggests a new transformation of aldehydes/ketones via N-tosylhydrazones to organophosphorus compounds.

  8. A Copper-Assisted Palladium(II)-catalyzed Direct Arylation of Cyclic Enaminones with Arylboronic Acids

    OpenAIRE

    Kim, Yong Wook; Niphakis, Micah J.; Georg, Gunda I.

    2012-01-01

    Described herein is a palladium(II)-catalyzed direct arylation of cyclic enaminones with arylboronic acids. The versatility of this method is that both electron-rich and electron-poor boronic acids can be coupled in high yields. A mixture of two Cu(II) additives was crucial for efficient cross-coupling. The role of each Cu(II) reagent appears to be distinct and complementary serving to assist catalyst reoxidation and transmetallation through a putative arylcopper intermediate.

  9. Palladium-catalyzed, asymmetric Baeyer–Villiger oxidation of prochiral cyclobutanones with PHOX ligands

    KAUST Repository

    Petersen, Kimberly S.

    2011-06-01

    Described in this report is a general method for the conversion of prochiral 3-substituted cyclobutanones to enantioenriched γ-lactones through a palladium-catalyzed Baeyer-Villiger oxidation using phosphinooxazoline ligands in up to 99% yield and 81% ee. Lactones of enantiopurity ≥93% could be obtained through a single recrystallization step. Importantly, 3,3-disubtituted cyclobutanones produced enantioenriched lactones containing a β-quaternary center. © 2011 Elsevier Ltd. All rights reserved.

  10. Copper-catalyzed formic acid synthesis from CO2 with hydrosilanes and H2O.

    Science.gov (United States)

    Motokura, Ken; Kashiwame, Daiki; Miyaji, Akimitsu; Baba, Toshihide

    2012-05-18

    A copper-catalyzed formic acid synthesis from CO2 with hydrosilanes has been accomplished. The Cu(OAc)2·H2O-1,2-bis(diphenylphosphino)benzene system is highly effective for the formic acid synthesis under 1 atm of CO2. The TON value approached 8100 in 6 h. The reaction pathway was revealed by in situ NMR analysis and isotopic experiments.

  11. Recoverable Palladium(0) on Poly(vinylpyrrolidone) Catalyzed Ligand-free Suzuki Reaction in Water

    Institute of Scientific and Technical Information of China (English)

    WANG Lei; LI Pin-Hua

    2006-01-01

    In the absence of any ligand, a recoverable palladium(O) on poly(vinylpyrrolidone) (PVP) catalyzed Suzuki reaction of aryl iodide and bromide with potassium aryltrifluoroborate was developed. The reaction conditions involved the use of water as the solvent, potassium carbonate as the base, and PVP supported palladium metal colloids as the catalyst. The palladium metal could be recovered and recycled for eight consecutive trials without significant loss of its activity.

  12. Palladium(II)-catalyzed direct alkoxylation of arenes: evidence for solvent-assisted concerted metalation deprotonation.

    Science.gov (United States)

    Anand, Megha; Sunoj, Raghavan B

    2011-09-16

    Density functional theory investigations on the mechanism of palladium acetate catalyzed direct alkoxylation of N-methoxybenzamide in methanol reveal that the key steps involve solvent-assisted N-H as well as C-H bond activations. The transition state for the critical palladium-carbon bond formation through a concerted metalation deprotonation (CMD) process leading to a palladacycle intermediate has been found to be more stable in the methanol-assisted pathway as compared to an unassisted route.

  13. A novel DNA joining activity catalyzed by T4 DNA ligase

    OpenAIRE

    Western, L M; Rose, S..J.

    1991-01-01

    The use of T4 and E. coli DNA ligases in genetic engineering technology is usually associated with nick-closing activity in double stranded DNA or ligation of 'sticky-ends' to produce recombinant DNA molecules. We describe in this communication the ability of T4 DNA ligase to catalyze intramolecular loop formation between annealed oligodeoxyribonucleotides wherein Watson-Crick base pairing is absent on one side of the ligation site. Enzyme concentration, loop size, substrate specificity, and ...

  14. Copper-catalyzed [3 + 2] cycloaddition of (phenylethynyl)di-p-tolylstibane with organic azides

    Science.gov (United States)

    Yamada, Mizuki; Matsumura, Mio; Uchida, Yuki; Kawahata, Masatoshi; Murata, Yuki; Kakusawa, Naoki; Yamaguchi, Kentaro

    2016-01-01

    Summary Trisubstituted 5-stibano-1H-1,2,3-triazoles were synthesized in moderate to excellent yields by the Cu-catalyzed [3 + 2] cycloaddition of a ethynylstibane with organic azides in the presence of CuBr (5 mol %) under aerobic conditions. The reaction of 5-stibanotriazole with HCl, I2, and NOBF4 afforded 1-benzyl-4-phenyltriazole, 1-benzyl-5-iodo-4-phenyltriazole, and a pentavalent organoantimony compound, respectively. PMID:27559379

  15. Photoredox-Catalyzed Ketyl–Olefin Coupling for the Synthesis of Substituted Chromanols

    Science.gov (United States)

    2016-01-01

    A visible light photoredox-catalyzed aldehyde olefin cyclization is reported. The method represents a formal hydroacylation of alkenes and alkynes and provides chromanol derivatives in good yields. The protocol takes advantage of the double role played by trialkylamines (NR3) which act as (i) electron donors for reducing the catalyst and (ii) proton donors to activate the substrate via a proton-coupled electron transfer. PMID:27442851

  16. Chelation-assisted palladium-catalyzed direct cyanation of 2-arylpyridine C-H bonds.

    Science.gov (United States)

    Jia, Xiaofei; Yang, Dongpeng; Zhang, Shouhui; Cheng, Jiang

    2009-10-15

    A chelation-assisted palladium-catalyzed ortho-cyanation of the sp2 C-H bond by CuCN provided aromatic nitriles in moderate to good yields. Notably, the reaction could be conducted on a 10 mmol scale. The key intermediate of the natural product of Menispermum dauricum DC was concisely synthesized by the procedure. This new approach represents an exceedingly practical method for the synthesis of aromatic nitriles and offers an attractive alternative to the traditional Sandmeyer reaction.

  17. Lewis base catalyzed enantioselective allylic hydroxylation of Morita-Baylis-Hillman carbonates with water

    KAUST Repository

    Zhu, Bo

    2011-08-19

    A Lewis base catalyzed allylic hydroxylation of Morita-Baylis-Hillman (MBH) carbonates has been developed. Various chiral MBH alcohols can be synthesized in high yields (up to 99%) and excellent enantioselectivities (up to 94% ee). This is the first report using water as a nucleophile in asymmetric organocatalysis. The nucleophilic role of water has been verified using 18O-labeling experiments. © 2011 American Chemical Society.

  18. Nickel-catalyzed cross-electrophile coupling of 2-chloropyridines with alkyl bromides.

    Science.gov (United States)

    Everson, Daniel A; Buonomo, Joseph A; Weix, Daniel J

    2014-01-01

    The synthesis of 2-alkylated pyridines by the nickel-catalyzed cross-coupling of two different electrophiles, 2-chloropyridines with alkyl bromides, is described. Compared to our previously published conditions for aryl halides, this method uses the different, more rigid bathophenanthroline ligand and is conducted at high concentration in DMF solvent. The method displays promising functional group compatibility and the conditions are orthogonal to the Stille coupling.

  19. Enantioselective palladium-catalyzed dearomative cyclization for the efficient synthesis of terpenes and steroids.

    Science.gov (United States)

    Du, Kang; Guo, Pan; Chen, Yuan; Cao, Zhen; Wang, Zheng; Tang, Wenjun

    2015-03-02

    A novel enantioselective palladium-catalyzed dearomative cyclization has been developed for the efficient construction of a series of chiral phenanthrenone derivatives bearing an all-carbon quaternary center. The effectiveness of this method in the synthesis of terpenes and steroids was demonstrated by a highly efficient synthesis of a kaurene intermediate, the facile construction of the skeleton of the anabolic steroid boldenone, and the enantioselective total synthesis of the antimicrobial diterpene natural product (-)-totaradiol.

  20. The first characterization of free radicals formed from cellular COX-catalyzed peroxidation.

    Science.gov (United States)

    Gu, Yan; Xu, Yi; Law, Benedict; Qian, Steven Y

    2013-04-01

    Through free radical-mediated peroxidation, cyclooxygenase (COX) can metabolize dihomo-γ-linolenic acid (DGLA) and arachidonic acid (AA) to form well-known bioactive metabolites, namely, the 1-series of prostaglandins (PGs1) and the 2-series of prostaglandins (PGs2), respectively. Unlike PGs2, which are generally viewed as proinflammatory and procarcinogenic PGs, PGs1 may possess anti-inflammatory and anti-cancer activity. Previous studies using ovine COX along with spin trapping and the LC/ESR/MS technique have shown that certain exclusive free radicals are generated from different free radical reactions in DGLA and AA peroxidation. However, it has been unclear whether the differences were associated with the contrasting bioactivity of DGLA vs AA. The aim of this study was to refine the LC/MS and spin trapping technique to make it possible for the association between free radicals and cancer cell growth to be directly tested. Using a colon cancer cell line, HCA-7 colony 29, and LC/MS along with a solid-phase extraction, we were able to characterize the reduced forms of radical adducts (hydroxylamines) as the free radicals generated from cellular COX-catalyzed peroxidation. For the first time, free radicals formed in the COX-catalyzed peroxidation of AA vs DGLA and their association with cancer cell growth were assessed (cell proliferation via MTS and cell cycle distribution via propidium iodide staining) in the same experimental setting. The exclusive free radicals formed from the COX-catalyzed peroxidation of AA and DGLA were shown to be correlated with the cell growth response. Our results indicate that free radicals generated from the distinct radical reactions in COX-catalyzed peroxidation may represent the novel metabolites of AA and DGLA that correspond to their contrasting bioactivity.

  1. Yttrium (III chloride catalyzed Mannich reaction: An efficient procedure for the synthesis of β-amino carbonyl compounds

    Directory of Open Access Journals (Sweden)

    Venkateswarlu Yekkirala

    2014-12-01

    Full Text Available Yttrium (III chloride catalyzed Mannich reaction of aldehydes with ketones and amines in acetonitrile at reflux temperature to give various β-amino carbonyl compounds in very good yields.

  2. Cisplatin inhibits the formation of a reactive intermediate during copper-catalyzed oxidation of amyloid β peptide.

    Science.gov (United States)

    Walke, Gulshan R; Rapole, Srikanth; Kulkarni, Prasad P

    2014-10-06

    Cisplatin was studied for its effect on the copper-catalyzed oxidation of amyloid β (Aβ) peptide. The interaction of cisplatin with Aβ1-16 in the presence of Cu(II) was investigated using cyclic voltammetry and mass spectrometry. The positive shift in the E1/2 value of Aβ1-16-Cu(II) suggests that the interaction of cisplatin alters the copper-binding properties of Aβ1-16. The mass spectrometry data show complete inhibition of copper-catalyzed decarboxylation/deamination of the Asp1 residue of Aβ1-16, while there is a significant decrease in copper-catalyzed oxidation of Aβ1-16 in the presence of cisplatin. Overall, our results provide a novel mode by which cisplatin inhibits copper-catalyzed oxidation of Aβ. These findings may lead to the design of better platinum complexes to treat oxidative stress in Alzheimer's disease and other related neurological disorders.

  3. The three transglycosylation reactions catalyzed by cyclodextrin glycosyltransferase from Bacillus circulans (strain 251) proceed via different kinetic mechanisms

    NARCIS (Netherlands)

    Veen, Bart A. van der; Alebeek, Gert-Jan W.M. van; Uitdehaag, Joost C.M.; Dijkstra, Bauke W.; Dijkhuizen, Lubbert

    2000-01-01

    Cyclodextrin glycosyltransferase (CGTase) catalyzes three transglycosylation reactions via a double displacement mechanism involving a covalent enzyme-intermediate complex (substituted-enzyme intermediate). Characterization of the three transglycosylation reactions, however, revealed that they diffe

  4. The Synthesis of 2,4,6-Triisopropyl-1,3,5-trioxane Catalyzed by Ionic Liquids

    Institute of Scientific and Technical Information of China (English)

    Jian Guo YANG; Xin Yu YU; Hai Hong WU; Zhi Lin CHENG; Yue Ming LIU; Ming Yuan HE

    2005-01-01

    The synthesis of 2, 4, 6-triisopropyl- 1, 3, 5-trioxane with high yield and desirable selectivity from solvent-free cyclotrimerization of isobutyraldehyde catalyzed by ionic liquids was reported in this work.

  5. Synthesis of Novel C2-Symmetrical Bidentate Phosphoramidite Ligands for Rh-catalyzed Asymmetric Hydrogenation of β-(Acylamino)acrylates

    Institute of Scientific and Technical Information of China (English)

    Qing Heng ZENG; Xiang Ping HU; Xin Miao LIANG; Zhuo ZHENG

    2006-01-01

    Two new C2-symmetrical bidentate phosphoramidite ligands were synthesized and employed in the Rh-catalyzed asymmetric hydrogenation of β-(acylamino)acrylates, up to 89% ee with full conversions was obtained.

  6. Palladium-catalyzed picolinamide-directed iodination of remote ortho-C−H bonds of arenes: Synthesis of tetrahydroquinolines

    Science.gov (United States)

    Nack, William A; Wang, Xinmou; Wang, Bo

    2016-01-01

    Summary A new palladium-catalyzed picolinamide (PA)-directed ortho-iodination reaction of ε-C(sp2)−H bonds of γ-arylpropylamine substrates is reported. This reaction proceeds selectively with a variety of γ-arylpropylamines bearing strongly electron-donating or withdrawing substituents, complementing our previously reported PA-directed electrophilic aromatic substitution approach to this transformation. As demonstrated herein, a three step sequence of Pd-catalyzed γ-C(sp3)−H arylation, Pd-catalyzed ε-C(sp2)−H iodination, and Cu-catalyzed C−N cyclization enables a streamlined synthesis of tetrahydroquinolines bearing diverse substitution patterns. PMID:27559375

  7. Ruthenium-catalyzed decarbonylative addition reaction of anhydrides with alkynes: a facile synthesis of isocoumarins and α-pyrones.

    Science.gov (United States)

    Prakash, Rashmi; Shekarrao, Kommuri; Gogoi, Sanjib; Boruah, Romesh C

    2015-06-21

    A novel ruthenium catalyzed straightforward and efficient synthesis of isocoumarin and α-pyrone derivatives has been accomplished by the decarbonylative addition reaction of anhydrides with alkynes under thermal conditions.

  8. A green and efficient deoximation using H2O2 catalyzed by montmorillonite-K10 supported COCl2

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Oximes were oxidized to the corresponding carbonyl compounds in good to high yields by environmentally friendly and green oxidant, H2O2 catalyzed by montmorillonite K310 supported cobalt(Ⅱ) chloride.

  9. Celecoxib influences steroid sulfonation catalyzed by human recombinant sulfotransferase 2A1.

    Science.gov (United States)

    Ambadapadi, Sriram; Wang, Peter L; Palii, Sergiu P; James, Margaret O

    2015-08-01

    Celecoxib has been reported to switch the human SULT2A1-catalyzed sulfonation of 17β-estradiol (17β-E2) from the 3- to the 17-position. The effects of celecoxib on the sulfonation of selected steroids catalyzed by human SULT2A1 were assessed through in vitro and in silico studies. Celecoxib inhibited SULT2A1-catalyzed sulfonation of dehydroepiandrosterone (DHEA), androst-5-ene-3β, 17β-diol (AD), testosterone (T) and epitestosterone (Epi-T) in a concentration-dependent manner. Low μM concentrations of celecoxib strikingly enhanced the formation of the 17-sulfates of 6-dehydroestradiol (6D-E2), 17β-dihydroequilenin (17β-Eqn), 17β-dihydroequilin (17β-Eq), and 9-dehydroestradiol (9D-E2) as well as the overall rate of sulfonation. For 6D-E2, 9D-E2 and 17β-Eqn, celecoxib inhibited 3-sulfonation, however 3-sulfonation of 17β-Eq was stimulated at celecoxib concentrations below 40 μM. Ligand docking studies in silico suggest that celecoxib binds in the substrate-binding site of SULT2A1 in a manner that prohibits the usual binding of substrates but facilitates, for appropriately shaped substrates, a binding mode that favors 17-sulfonation.

  10. Fullerene-catalyzed reduction of azo derivatives in water under UV irradiation

    KAUST Repository

    Guo, Yong

    2012-09-27

    Metal-free fullerene (C60) was found to be an effective catalyst for the reduction of azo groups in basic aqueous solution under UV irradiation in the presence of NaBH4. Use of NaBH4 by itself is not sufficient to reduce the azo dyes without the assistance of a metal catalyst such as Pd and Ag. Experimental and theoretical results suggest that C 60 catalyzes this reaction by using its vacant orbital to accept the electron in the bonding orbital of azo dyes, which leads to the activation of the N=N bond. UV irradiation increases the ability of C60 to interact with electron-donor moieties in azo dyes. Filling a vacancy: Experimental and theoretical methods have been combined to show that C60-catalyzed reductions of azo compounds form aromatic amines under UV irradiation (see scheme). The obtained results show that C60 acts as an electron acceptor to catalyze the reduction of azo compounds, and the role of UV irradiation is to increase the ability of C60 to interact with electron-donor moieties in azo compounds. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Structural Determinants of Alkyne Reactivity in Copper-Catalyzed Azide-Alkyne Cycloadditions

    Directory of Open Access Journals (Sweden)

    Xiaoguang Zhang

    2016-12-01

    Full Text Available This work represents our initial effort in identifying azide/alkyne pairs for optimal reactivity in copper-catalyzed azide-alkyne cycloaddition (CuAAC reactions. In previous works, we have identified chelating azides, in particular 2-picolyl azide, as “privileged” azide substrates with high CuAAC reactivity. In the current work, two types of alkynes are shown to undergo rapid CuAAC reactions under both copper(II- (via an induction period and copper(I-catalyzed conditions. The first type of the alkynes bears relatively acidic ethynyl C-H bonds, while the second type contains an N-(triazolylmethylpropargylic moiety that produces a self-accelerating effect. The rankings of reactivity under both copper(II- and copper(I-catalyzed conditions are provided. The observations on how other reaction parameters such as accelerating ligand, reducing agent, or identity of azide alter the relative reactivity of alkynes are described and, to the best of our ability, explained.

  12. Biodiesel synthesis combining pre-esterification with alkali catalyzed process from rapeseed oil deodorizer distillate

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yun; Wang, Ling; Yan, Yunjun [College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074 (China)

    2009-07-15

    A two-step technique combining pre-esterification catalyzed by cation exchange resin with transesterification catalyzed by base alkali was developed to produce biodiesel from rapeseed oil deodorizer distillate (RDOD). The free fatty acids (FFAs) in the feedstock were converted to methyl esters in the pre-esterification step using a column reactor packed with cation exchange resin. The acid value of oil was reduced from the initial 97.60 mg-KOH g{sup -1} oil to 1.12 mg-KOH g{sup -1} oil under the conditions of cation exchange resin D002 catalyst packed dosage 18 wt.% (based on oil weight), oil to methanol molar ratio 1:9, reaction temperature 60 C, and reaction time 4 h. The biodiesel yield by transesterification was 97.4% in 1.5 h using 0.8 wt.% KOH as catalyst and a molar ratio of oil to methanol 1:4 at 60 C. The properties of RDOD biodiesel production in a packed column reactor followed by KOH catalyzed transesterification were measured up the standards of EN14214 and ASTM6751-03. (author)

  13. Enantioselective epoxidation and carbon-carbon bond cleavage catalyzed by Coprinus cinereus peroxidase and myeloperoxidase.

    Science.gov (United States)

    Tuynman, A; Spelberg, J L; Kooter, I M; Schoemaker, H E; Wever, R

    2000-02-01

    We demonstrate that myeloperoxidase (MPO) and Coprinus cinereus peroxidase (CiP) catalyze the enantioselective epoxidation of styrene and a number of substituted derivatives with a reasonable enantiomeric excess (up to 80%) and in a moderate yield. Three major differences with respect to the chloroperoxidase from Caldariomyces fumago (CPO) are observed in the reactivity of MPO and CiP toward styrene derivatives. First, in contrast to CPO, MPO and CiP produced the (S)-isomers of the epoxides in enantiomeric excess. Second, for MPO and CiP the H(2)O(2) had to be added very slowly (10 eq in 16 h) to prevent accumulation of catalytically inactive enzyme intermediates. Under these conditions, CPO hardly showed any epoxidizing activity; only with a high influx of H(2)O(2) (300 eq in 1.6 h) was epoxidation observed. Third, both MPO and CiP formed significant amounts of (substituted) benzaldehydes as side products as a consequence of C-alpha-C-beta bond cleavage of the styrene derivatives, whereas for CPO and cytochrome c peroxidase this activity is not observed. C-alpha-C-beta cleavage was the most prominent reaction catalyzed by CiP, whereas with MPO the relative amount of epoxide formed was higher. This is the first report of peroxidases catalyzing both epoxidation reactions and carbon-carbon bond cleavage. The results are discussed in terms of mechanisms involving ferryl oxygen transfer and electron transfer, respectively.

  14. Integrated Production of Xylonic Acid and Bioethanol from Acid-Catalyzed Steam-Exploded Corn Stover.

    Science.gov (United States)

    Zhu, Junjun; Rong, Yayun; Yang, Jinlong; Zhou, Xin; Xu, Yong; Zhang, Lingling; Chen, Jiahui; Yong, Qiang; Yu, Shiyuan

    2015-07-01

    High-efficiency xylose utilization is one of the restrictive factors of bioethanol industrialization. However, xylonic acid (XA) as a new bio-based platform chemical can be produced by oxidation of xylose with microbial. So, an applicable technology of XA bioconversion was integrated into the process of bioethanol production. After corn stover was pretreated with acid-catalyzed steam-explosion, solid and liquid fractions were obtained. The liquid fraction, also named as acid-catalyzed steam-exploded corn stover (ASC) prehydrolyzate (mainly containing xylose), was catalyzed with Gluconobacter oxydans NL71 to prepare XA. After 72 h of bioconversion of concentrated ASC prehydrolyzate (containing 55.0 g/L of xylose), the XA concentration reached a peak value of 54.97 g/L, the sugar utilization ratio and XA yield were 94.08 and 95.45 %, respectively. The solid fraction was hydrolyzed to produce glucose with cellulase and then fermented with Saccharomyces cerevisiae NL22 to produce ethanol. After 18 h of fermentation of concentrated enzymatic hydrolyzate (containing 86.22 g/L of glucose), the ethanol concentration reached its highest value of 41.48 g/L, the sugar utilization ratio and ethanol yield were 98.72 and 95.25 %, respectively. The mass balance showed that 1 t ethanol and 1.3 t XA were produced from 7.8 t oven dry corn stover.

  15. Effects of Ni catalyzer on growth velocity and morphology of SiC nano-fibers

    Institute of Scientific and Technical Information of China (English)

    XU Xian-feng; XIAO Peng; XIONG Xiang; HUANG Bai-yun

    2009-01-01

    Composite felts reinforced by both SiC nano-fibers (SiC-NFs) and carbon fibers were prepared at 1 273 K using Ni granules as catalyzers with different deposition time. SiC-NFs were deposited on the surface of the carbon fibers in situ by catalytic chemical vapor deposition(CCVD). The phase, microstructure and morphology of the fibers after electroplating and deposition were characterized by XRD, SEM and TEM. The results show that the SiC-NFs produced by CCVD are composed of single crystal of β-SiC. It is found that smaller nano-granules are more active as catalyzers. The resulting SiC-NFs appear more spindle-like and have a more homogeneous dispersion. The mass change of the samples before and after deposition shows that using more Ni granules results in a faster growth velocity of SiC-NFs. With the same electroplating time, the growth velocity of the SiC-NFs first increases and then decreases. At around 4 h, it reaches the maximum growth velocity, and it becomes nearly constant at around 8 h. After 8 h, the stable growth velocity of the electroplated Ni samples is faster than that of the conventional sample produced without catalyzers, because the SiC-NFs can improve the specific surface area and the activity of the surface.

  16. Discoloration of Rhodamine B dyeing wastewater by schorl-catalyzed Fenton-like reaction

    Institute of Scientific and Technical Information of China (English)

    Murari; PRASAD

    2009-01-01

    As other natural iron-bearing minerals, schorl could be taken as an effective iron source for degradation of organic pollutants by mineral-catalyzed Fenton-like system. In our present study, the schorl-catalyzed Fenton-like system has been successfully developed for discoloration of an active commercial dye, Rhodamine B (RhB), in an aqueous solution. Through a number of batch discoloration experiments under various conditions, it was found that the reactivity of the system increased by, respectively, increasing schorl dosage, temperature, hydrogen peroxide starting concentration and by decreasing the pH. Over 90% of discoloration ratio could be gained in less than 30 min, and nearly 70% of total organic carbon (TOC) could be removed in less than 200 min. And, the schorl catalyst could be repeatedly used at least ten times, still with high catalytic activity. Comparative studies indicated that the RhB discoloration ratios were much higher in presence of schorl and H2O2 than those in presence of schorl or H2O2 only, which suggested that the schorl-catalyzed Fenton-like reaction governed the RhB discoloration process. The content of Fe ion leaching in the solution was also measured using inductively coupling plasma-atomic emission spectra (ICP-AES). A mechanism proposed herein suggested that adsorption and Fenton-like reaction (heterogeneous and homogeneous) were responsible for the discoloration of RhB.

  17. The kinetics and QSAR of abiotic reduction of mononitro aromatic compounds catalyzed by activated carbon.

    Science.gov (United States)

    Gong, Wenwen; Liu, Xinhui; Gao, Ding; Yu, Yanjun; Fu, Wenjun; Cheng, Dengmiao; Cui, Baoshan; Bai, Junhong

    2015-01-01

    The kinetics of abiotic reduction of mono-nitro aromatic compounds (mono-NACs) catalyzed by activated carbon (AC) in an anaerobic system were examined. There were 6 types of substituent groups on nitrobenzene, including methyl, chlorine, amino, carboxyl, hydroxyl and cyanogen groups, at the ortho, meta or para positions. Our results showed that reduction followed pseudo-first order reaction kinetics, and that the rate constant (logkSA) varied widely, ranging between -4.77 and -2.82, depending upon the type and position of the substituent. A quantitative structure-activity relationship (QSAR) model using 15 theoretical molecular descriptors and partial-least-squares (PLS) regression was developed for the reduction rates of mono-NACs catalyzed by AC. The cross-validated regression coefficient (Qcum(2), 0.861) and correlation coefficient (R(2), 0.898) indicated significantly high robustness of the model. The VIP (variable importance in the projection) values of energy of the lowest unoccupied molecular orbital (ELUMO) and the maximum net atomic charge on the aromatic carbon bound to the nitro group (QC(-)) were 1.15 and 1.01, respectively. These values indicated that the molecular orbital energies and the atomic net charges might play important roles in the reduction of mono-NACs catalyzed by AC in anaerobic systems.

  18. Simultaneous reduction of particulate matter and NO(x) emissions using 4-way catalyzed filtration systems.

    Science.gov (United States)

    Swanson, Jacob J; Watts, Winthrop F; Newman, Robert A; Ziebarth, Robin R; Kittelson, David B

    2013-05-07

    The next generation of diesel emission control devices includes 4-way catalyzed filtration systems (4WCFS) consisting of both NOx and diesel particulate matter (DPM) control. A methodology was developed to simultaneously evaluate the NOx and DPM control performance of miniature 4WCFS made from acicular mullite, an advanced ceramic material (ACM), that were challenged with diesel exhaust. The impact of catalyst loading and substrate porosity on catalytic performance of the NOx trap was evaluated. Simultaneously with NOx measurements, the real-time solid particle filtration performance of catalyst-coated standard and high porosity filters was determined for steady-state and regenerative conditions. The use of high porosity ACM 4-way catalyzed filtration systems reduced NOx by 99% and solid and total particulate matter by 95% when averaged over 10 regeneration cycles. A "regeneration cycle" refers to an oxidizing ("lean") exhaust condition followed by a reducing ("rich") exhaust condition resulting in NOx storage and NOx reduction (i.e., trap "regeneration"), respectively. Standard porosity ACM 4-way catalyzed filtration systems reduced NOx by 60-75% and exhibited 99.9% filtration efficiency. The rich/lean cycling used to regenerate the filter had almost no impact on solid particle filtration efficiency but impacted NOx control. Cycling resulted in the formation of very low concentrations of semivolatile nucleation mode particles for some 4WCFS formulations. Overall, 4WCFS show promise for significantly reducing diesel emissions into the atmosphere in a single control device.

  19. Peroxidase-catalyzed S-oxygenation: Mechanism of oxygen transfer for lactoperoxidase

    Energy Technology Data Exchange (ETDEWEB)

    Doerge, D.R.; Cooray, N.M. (Univ. of Hawaii, Honolulu (United States)); Brewster, M.E. (Pharmatec Inc., Alachua, FL (United States))

    1991-09-17

    The mechanism of organosulfur oxygenation by peroxidases (lactoperoxidase (LPX), chloroperoxidase, thyroid peroxidase, and horseradish peroxidase) and hydrogen peroxide was investigated by use of para-substituted thiobenzamides and thioanisoles. The rate constants for thiobenzamide oxygenation by LPX/H{sub 2}O{sub 2} were found to correlate with calculated vertical ionization potentials, suggesting rate-limiting single-electron transfer between LPX compound I and the organosulfur substrate. The incorporation of oxygen from {sup 18}O-labeled hydrogen peroxide, water, and molecular oxygen into sulfoxides during peroxidase-catalyzed S-oxygenation reactions was determined by LC- and GC-MS. All peroxidases tested catalyzed essentially quantitative oxygen transfer from {sup 18}O-labeled hydrogen peroxide into thiobenzamide S-oxide, suggesting that oxygen rebound from the oxoferryl heme is tightly coupled with the initial electron transfer in the active site. Experiments using H{sub 2}{sup 18}O{sub 2}, and H{sub 2}{sup 18}O showed the LPX catalyzed approximately 85,22, and 0% {sup 18}O-incorporation into thioanisole sulfoxide oxygen, respectively. These results are consistent with an active site controlled mechanism in which the protein radical form of LPX compound I is an intermediate in LPX-mediated sulfoxidation reactions.

  20. Effect of Ozone Produced from Antibody-catalyzed Water Oxidation on Pathogenesis of Atherosclerosis

    Institute of Scientific and Technical Information of China (English)

    Ke-Jun PENG; Yu-Shan HUANG; Li-Na AN; Xiao-Qun HAN; Jing-Ge ZHANG; Qiu-Lin WANG; Jing SUN; Shu-Ren WANG

    2006-01-01

    Recent studies have suggested that antibodies can catalyze the generation of unknown oxidants including hydrogen peroxide (H2O2) and ozone (O3) from singlet oxygen (1O2) and water. This study is aimedto detect the effect of antibody-catalyzed water oxidation on atherosclerosis. Our results showed that both H2O2 and O3 were produced in human leukemia THP- 1 monocytes incubated with human immunoglobulin G and phorbol myristate acetate. In the THP-1 monocytes incubated with human immunoglobulin G, phorbol myristate acetate and low density lipoprotein, the intracellular total cholesterol, free cholesterol, cholesteryl ester and lipid peroxides clearly increased, and a larger number of foam cells were observed by oil red O staining. The accumulation of all intracellular lipids was significantly inhibited by vinylbenzoic acid, and only slightly affected by catalase. These findings suggested that the production of O3, rather than H2O2, might be involved in the pathogenesis of atherosclerosis through the antibody-catalyzed water oxidation pathway.