- Iron Catalyzed Double Bond Isomerization: Evidence for an FeI/FeIII Catalytic Cycle
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Iron-catalyzed isomerization of alkenes is reported using an iron(II) β-diketiminate pre-catalyst. The reaction proceeds with a catalytic amount of a hydride source, such as pinacol borane (HBpin) or ammonia borane (H3N?BH3). Reactivity with both allyl arenes and aliphatic alkenes has been studied. The catalytic mechanism was investigated by a variety of means, including deuteration studies, Density Functional Theory (DFT) and Electron Paramagnetic Resonance (EPR) spectroscopy. The data obtained support a pre-catalyst activation step that gives access to an η2-coordinated alkene FeI complex, followed by oxidative addition of the alkene to give an FeIII intermediate, which then undergoes reductive elimination to allow release of the isomerization product.
- Woof, Callum R.,Durand, Derek J.,Fey, Natalie,Richards, Emma,Webster, Ruth L.
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supporting information
p. 5972 - 5977
(2021/03/17)
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- Amphiphilic polymeric nanoreactors containing Rh(i)-NHC complexes for the aqueous biphasic hydrogenation of alkenes
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A rhodium(i) complex bearing a monodentate N-heterocyclic carbene ligand has been confined into the core of amphiphilic polymeric core-crosslinked micelles (CCMs). The Rh complex was covalently bound to the polymeric chains by incorporation of a polymerizable unit on the NHC ligand. Nanoreactor Rh-NHCmes@CCM5bhas been evaluated as a catalyst for the aqueous biphasic hydrogenation of styrene and other alkenes. It has shown a high activity with styrene at a low catalytic loading (10?000/1 substrate/Rh ratio), greater than that of an analogous molecular Rh(i) complex, and its evolution to Rh0is slower. This is attributed to several factors, among which the confinement effect and the favourable polyoxygenated environment of the nanoreactor core. Finally, the CCMs could be recycled up to four times with almost no loss of activity over 3 h cycles and the loss of rhodium per cycle was on average lower than 0.6 ppm.
- Allandrieu, Audrey,Coppel, Yannick,Daran, Jean-Claude,Gayet, Florence,Hromov, Roman,Labande, Agnès,Manoury, Eric,Poli, Rinaldo,Ruzhylo, Illia,Sabatier, Cassandra,Sambou, Sasaline Salomon,Wang, Hui
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p. 6811 - 6824
(2021/10/25)
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- Method and Means for Releasing a Terpene Mixture to a Cannabis Flower During Storage
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A method and means for releasing a terpene mixture to a Cannabis flower during storage with may be from a cotton pulp card or a two-way humidity pack with an additional terpene blend for keeping a Cannabis flower fresh while naturally increasing the desired terpene levels. The product is a blend of humidity regulating agents infused with terpenes (plant derived) which allows for the product to be paired with herbal material to increase and maintain the relative humidity, while transferring the flavor/aroma/taste terpenes from the package into the herbal material. There are two embodiments, the first is a Terp Pack+Humidity (“Terp Pack+RH”) which contains a herban material to increase and maintain relative humidity, while releasing the infused terenes, and the second is more simply a Terp Pack (“Terp Pack”) which contains no humidity enhancing material and is only a carrier for releasing the terpene mixture.
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- Exploring the Keggin-Type Heteropolyacid-Catalyzed Reaction Pathways of the Β-Pinene with Alkyl Alcohols
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Abstract: In this work, we investigated the activity of Keggin heteropolyacid catalysts (i.e., H3PW12O40, H3PMo12O40 and H4SiW12O40) in β-pinene reactions with alkyl alcohols (i.e. methyl, ethyl, propyl, sec-propyl, butyl and sec-butyl alcohols), and exploring the different aspects that drive the selectivity of this process. We have found that carbon skeletal rearrangements and isomerization providing intermediate carbocations that controlling the reaction selectivity. β-pinene was preferentially converted to α-terpinyl ion which undergoes a nucleophilic attack of alcohol providing alkyl alcohol. Bornyl ion was converted to bornyl and fenchyl ethers. The other secondary products were β-pinene isomers obtained from bornyl and α-terpinyl carbocations. Phosphotungstic acid (i.e., H3PW12O40) was the most active catalyst and selective toward the main product (α-terpinyl alkyl ether); the highest conversion (ca. 96%) and ether selectivity (ca. 61%) was achieved in the reactions with β-pinene. Although having also been alkoxylate, α-pinene was less reactive (ca. 40%), while camphene and limonene remained unreactive under reaction conditions studied. An increase of temperature resulted in an improvement on conversion of β-pinene and selectivity toward α-terpinyl methyl ether. Similarly, the H3PW12O40 concentration played a crucial role on reaction selectivity. This work presents positive features such as a short reaction time, high atom economy, mild reaction conditions (i.e., low temperature and room pressure). Even though soluble the catalyst was easily recovered by liquid -liquid extraction and efficiently reused. Graphical Abstract: [Figure not available: see fulltext.].
- Polo, Henrique Priori,Lopes, Neide Paloma Goncalves,da Silva, Márcio José
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p. 2844 - 2853
(2019/05/28)
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- Bifunctional catalyst Pd-Al-MCM-41 for efficient dimerization-hydrogenation of β-pinene in one pot
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A new type of bimetallic palladium and aluminum incorporated mobile crystalline materials (Pd-Al-MCM-41) as bifunctional catalysts has been hydrothermally synthesized. Characterization shows that these molecular materials exhibit an ordered mesoporous structure, high surface area and a good dispersion of palladium in the frame. The catalytic activity of the Pd-Al-MCM-41 for the dimerization-hydrogenation reaction system of β-pinene in one pot has been systematically studied. Pd0.5-Al30-MCM-41 (SiO2/Al2O3 = 30, 0.5 wt% palladium content) was found to be the best catalyst which gave a dimer yield of up to 64.7%. It is worth noting that palladium shows a good synergic catalytic effect with aluminum in the dimerization reaction and enhances the dimerization yield. Furthermore, the bifunctional catalyst displayed a good activity over 4 runs.
- Zhang, Song,Xu, Chao,Zhai, Guoqing,Zhao, Mingliang,Xian, Mo,Jia, Yuxiang,Yu, Zongjiang,Liu, Fusheng,Jian, Fangfang,Sun, Weizhi
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p. 47539 - 47546
(2017/10/19)
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- Converting S-limonene synthase to pinene or phellandrene synthases reveals the plasticity of the active site
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S-limonene synthase is a model monoterpene synthase that cyclizes geranyl pyrophosphate (GPP) to form S-limonene. It is a relatively specific enzyme as the majority of its products are composed of limonene. In this study, we converted it to pinene or phellandrene synthases after introducing N345A/L423A/S454A or N345I mutations. Further studies on N345 suggest the polarity of this residue plays a critical role in limonene production by stabilizing the terpinyl cation intermediate. If it is mutated to a non-polar residue, further cyclization or hydride shifts occurs so the carbocation migrates towards the pyrophosphate, leading to the production of pinene or phellandrene. On the other hand, mutant enzymes that still possess a polar residue at this position produce limonene as the major product. N345 is not the only polar residue that may stabilize the terpinyl cation because it is not strictly conserved among limonene synthases across species and there are also several other polar residues in this area. These residues could form a “polar pocket” that may collectively play this stabilizing role. Our study provides important insights into the catalytic mechanism of limonene synthases. Furthermore, it also has wider implications on the evolution of terpene synthases.
- Xu, Jinkun,Ai, Ying,Wang, Jianhui,Xu, Jingwei,Zhang, Yongkang,Yang, Dong
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- Support Functionalization with a Phosphine-Containing Hyperbranched Polymer: A Strategy to Enhance Phosphine Grafting and Metal Loading in a Hydroformylation Catalyst
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We present the design of a hydroformylation catalyst through the immobilization of air-stable Rh nanoparticles (NPs) on a magnetic support functionalized with a hyperbranched polymer that bears terminal phosphine groups. The catalyst modification with the hyperbranched polymer improved the metal–support interaction, the metal loading, and the catalytic activity. The catalyst was active for the hydroformylation of natural products, such as estragole, and could be used in successive reactions with negligible metal leaching. The phosphine grafting played a key role in the recyclability of Rh NPs under hydroformylation conditions. The catalytic activity was maintained in successive reactions, even if the catalyst was exposed to air during each recovery procedure. The modification of the support with hyperbranched polyester allowed us either to increase the number of Rh active species or to obtain more active Rh species on the catalyst surface.
- Garcia, Marco A. S.,Heyder, Rodrigo S.,Oliveira, Kelley C. B.,Costa, Jean C. S.,Corio, Paola,Gusevskaya, Elena V.,dos Santos, Eduardo N.,Bazito, Reinaldo C.,Rossi, Liane M.
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p. 1951 - 1960
(2016/07/06)
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- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
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The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- Unique catalysis of gold nanoparticles in the chemoselective hydrogenolysis with H2: Cooperative effect between small gold nanoparticles and a basic support
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Gold nanoparticles on hydrotalcite act as a heterogeneous catalyst for the chemoselective hydrogenolysis of various allylic carbonates to the corresponding terminal alkenes using H2 as a clean reductant. The combination of gold nanoparticles and basic supports elicited significantly unique and selective catalysis in the hydrogenolysis.
- Noujima, Akifumi,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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p. 6723 - 6725
(2012/07/28)
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- Photocatalytic removal of monoterpenes in the gas phase. Activity and regeneration
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We show the photocatalytic removal of various monoterpenes such as β-pinene, α-pinene, camphene and limonene in the gas phase as a function of the reaction temperature, from room temperature to 80°C, taking also into account the thermal catalytic isomeriz
- Salem, Ibtissam,Keller, Nicolas,Keller, Valerie
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experimental part
p. 966 - 973
(2010/04/23)
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- Catalytic activity of the VIII group metals in the hydrogenation and isomerization of α- And β-pinenes
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The kinetic regularities of the liquid-phase hydrogenation and isomerization of α- and β-pinenes over the Pd/C, Ru/C, Rh/C, Pt/C, and Ir/C catalysts were studied at temperatures ranging from 20 to 100 °C and at hydrogen pressures of 1-11 bar using n-octane as the solvent. The hydrogenation and isomerization of α- and β-pinenes occur simultaneously on the Ru/C, Rh/C, Pt/C, and Ir/C catalysts, and the reaction mixture contains the products of double bond hydrogenation, viz., cis- and trans-pinanes. The Ru, Rh, and Pd metals have a higher catalytic activity in β-pinene isomerization than Ir and Pt. Among the VIII Group metals studied, the Pd-based catalyst has the highest catalytic activity in double bond isomerization of α- and β-pinenes. The general scheme of the mechanism of hydrogenation and isomerization of α- and β-pinenes on the Pd/C catalyst was proposed.
- Deliy,Simakova
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body text
p. 2056 - 2064
(2010/05/02)
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- Biochemistry and molecular genetics of the biosynthesis of the earthy odorant methylisoborneol in Streptomyces coelicolor
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Methylisoborneol (2) is a volatile organic compound produced by a wide variety of Actinomycete soil organisms, myxobacteria, and cyanobacteria. It has an unusually low odor threshold and, together with geosmin, is responsible for the characteristic smell of moist soil as well as unpleasant taste and odor episodes associated with public water supplies and contamination of various foodstuffs, including fish, wine, and beer. Despite considerable interest in detection and remediation of methylisoborneol, the biosynthesis of this methylated monoterpene has been obscure. In Streptomyces coelicolor, the sco7700 and sco7701 genes are shown to correspond to a two-gene operon responsible for methylisoborneol biosynthesis. Both genes have been amplified by PCR and the resulting DNA has been cloned and expressed in Escherichia coli. Incubation of recombinant SCO7701 protein, annotated as a possible C-methyltransferase, with geranyl diphosphate (1) and S-adenosylmethionine gave the previously unknown compound, (E)-2-methylgeranyl diphosphate (3). Incubation of 3 in the presence of Mg2+ with recombinant SCO7700, previously annotated only as a possible metal-binding protein or terpenoid synthase, resulted in the formation of 2-methylisoborneol (2). The steady-state kinetic parameters for both biochemical reactions have been determined. Incubation of geranyl diphosphate and S-adenosylmethionine with a mixture of both SCO7700 and SCO7701 resulted in formation of methylisoborneol (2). Cyclization of 2-methylgeranyl diphosphate (3) to methylisoborneol (2) likely involves the intermediacy of 2-methyllinalyl diphosphate. Copyright
- Wang, Chieh-Mei,Cane, David E.
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supporting information; experimental part
p. 8908 - 8909
(2009/02/03)
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- Cationic rhodium(I) complexes containing 4,4′-disubstituted 2,2′-bipyridines: A systematic variation on electron density over the metal centre
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A series of [Rh(COD)(X2-bipy)]BF4 complexes (COD = 1,5-cyclooctadiene; X2-bipy = 4,4′-disubstituted 2,2′-bipyridines; X = OCH3, CH3, H, Cl or NO 2) has been prepared from [Rh(COD)Cl]2. The complexes for X = OCH3, Cl and NO2 have not been described previously in the literature. All complexes have been characterised by elemental analysis, IR, 1H NMR and UV-Vis spectrometry. This series of complexes presents a wide variation on electron density over the metal centre with virtually no variation on its steric environment which discloses interesting possibilities for catalytic and electro-catalytic studies. A preliminary evaluation of these complexes on the hydroformylation of camphene and β-pinene showed that under the rather drastic conditions employed the complexes acted as a precursor for [Rh(CO)3H], which accounts for most of the catalytic activity.
- Ribeiro, Paulo E.A.,Donnici, Claudio L.,Dos Santos, Eduardo N.
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p. 2037 - 2043
(2007/10/03)
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- Thermolysis of α-pinene in supercritical lower alcohols
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Thermal isomerization of α-pinene in supercritical solvents, viz., ethanol, methanol, and propan-1-ol, was carried out, and differences in the rate and selectivity of the process were revealed. In supercritical ethanol the reaction rate increases sharply and the selectivity remains unchanged with an increase in the temperature (from 290 to 390°C) or pressure (from 90 to 270 atm). The main reaction products are limonene, isomeric alloocimenes, and pyronenes. The selectivity for limonene in propan-1-ol is higher than in other alcohols when the conversion of α-pinene not higher than 50%. In supercritical ethanol (430°C, 120 atm, 140 s) limonene is more stable than α-pinene (conversion 8%).
- Chibiryaev,Anikeev,Yermakova,Mikenin,Kozhevnikov,Sal'nikova
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p. 987 - 992
(2008/02/01)
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- Solvent extraction process
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A process for extracting a compound or composition of matter from a raw material containing that compound or composition as a constituent part is described. The process comprises the steps of (1) contacting the raw material with an extraction solvent comprising a heptafluoropropane so as to extract the compound or composition from the raw material into the solvent, and (2) separating the solvent containing the extracted compound or composition from raw material. The process is particularly adapted for extracting flavours, fragrances and neutraceuticals from materials of plant origin.
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- Rhodium catalyzed hydroformylation of β-pinene and camphene: effect of phosphorous ligands and reaction conditions on stereoselectivity
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The effect of phosphorous ligands on the rhodium catalyzed hydroformylation of β-pinene and camphene has been studied. In unmodified systems, β-pinene undergoes a fast isomerization to α-pinene. At longer reaction times and higher temperatures, the isomerization equilibrium is shifted resulting in the 80 percent chemoselectivity for β-pinene hydrofromylation products (97 percent trans). The addition of various diphosphines or phosphites improves the chemoselectivity and shifts the hydroformylation towards cis aldehyde 3a. Both the rate and diastereoselectivity of the hydroformylation of β-pinene are largely influenced by the basicity of auxiliary ligands, but surprisingly no correlation between their steric characteristics and the diastereoselectivity of the catalytic system has been revealed for the ligands with cone angles 128-165 deg. The systems with more basic ligands show lower activities, higher diastereoselectivities and usually higher chemoselectivities in the β-pinene hydroformylation. Camphene gives linear aldehyde 6, with virtually 100 percent regio- and chemoselectivity in both modified and unmodified systems. The addition of phosphorous ligands favors the formation of endo isomer 6b:6a/6b ca. 1/1.5 , whereas the ratio ca. 1/1 unmodified systems. Neither steric nor electronic parameters of the ligands have been found to influence significantly the diastereoselectivity of the camphene hydroformylation.
- Barros, Humberto J. V.,Ospina, Maria L.,Arguello, Eduardo,Rocha, William R.,Gusevskaya, Elena V.,Santos, Eduardo N. dos
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p. 150 - 157
(2007/10/03)
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- Thrombin receptor antagonists
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Heterocyclic-substituted tricyclics of the formula or a pharmaceutically acceptable salts thereof, wherein: n1 and n2 are independently 0-2; Het is an optionally substituted mono-, bi- or tricyclic heteroaromatic group; B is alkyl or optionally substituted alkenyl; R22 is —COR23 or a carboxy, sulfinyl, sulfonyl, sulfonamide or amino acid derivative; R23 is haloalkyl; alkenyl; haloalkenyl; alkynyl; optionally substituted cycloalkyl; cycloalkyl-alkyl; aryl; arylalkyl; heteroaryl; heterocycloalkyl; or —COOH and/or —SO3H substituted alkyl; R1, R2, R3, R9, R10 and R11 are as defined in the specification; are disclosed, as well as pharmaceutical compositions containing them and a method of treating diseases associated with thrombosis, atherosclerosis, restenosis, hypertension, angina pectoris, arrhythmia, heart failure, and cancer by administering said compounds.
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- Rhodium and palladium complexes from 1,1′ and 1,2 ferrocenylphosphine as bidentate ligands. Versatile coordination
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The complexation of the mixed bidentate ligands 1-diphenylphosphino-1′-diphenylthiophosphinoferrocenyl and 1,2-bis-(diphenylphosphino)ferrocenyl with rhodium(I) and palladium(II) species yield a range of mono- and dirhodium or palladium complexes. Their interest as possible catalysts for alkene hydroformylation and alkoxycarbonylation and Heck coupling reactions has been assessed. Fe[C5Me4P(S)Ph2][C5Me 4PPh2]PdCl2 and Fe[C5H2-1,2-(PPh2)2-4- tBu][C5H5]PdCl2 have been characterized by single-crystal X-ray diffraction studies.
- Broussier, Roland,Bentabet, Emmanuelle,Laly, Myriam,Richard, Philippe,Kuz'mina, Lyudmila G.,Serp, Philippe,Wheatley, Nigel,Kalck, Philippe,Gautheron, Bernard
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- Monoterpene synthase activities in leaves of Picea abies (L.) Karst. and Quercus ilex L.
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In addition to direct ecological functions in the interaction of plants with the environment, the emission of monoterpenes, especially from the foliage of evergreen trees, is of great importance for the production of ozone and photochemical oxidants in the troposphere. In the present work, we established a reproducible non-radioactive standard enzyme assay and characterized monoterpene synthase activities in needles of Norway spruce (Picea abies (L.) Karst.) and in leaves of holm oak (Quercus ilex L.). In Norway spruce, the dominant monoterpenes formed were α-pinene, camphene, and to a lesser extent β-pinene and limonene. In holm oak, α-pinene, sabinene, and β-pinene were the main products, while limonene was a minor component. Under optimum conditions, in both Norway spruce and holm oak, monoterpene formation remained constant up to 180 min and 90 min, respectively, and varied with the buffer and Mg2+ and Mn2+ concentrations used. Optimum temperature for monoterpene synthase activity was 40°C in both species; optimal pH ranged between 6.5 and 7.5 in both species. Apparent Michaelis- constants for the substrate GDP were ca. 17.9 ± 5.1 μM for Norway spruce and ca. 69.4 ± 22.1 μM for holm oak. Molecular weight determination by FPLC indicated that the monoterpene synthases in Norway spruce and holm oak have native molecular weights of ca. 59 and 50 kDa, respectively. (C) 2000 Elsevier Science Ltd.
- Fischbach, Robert J.,Zimmer, Ina,Steinbrecher, Rainer,Pfichner, Andreas,Schnitzler, Joerg-Peter
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p. 257 - 265
(2007/10/03)
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- Fine particle and gaseous emission rates from residential wood combustion
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Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning-communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter(a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and se mivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8- C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and forts were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography. Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter (a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and semivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8-C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence, and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and ions were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography.
- Mcdonald, Jacob D.,Zielinska, Barbara,Fujita, Eric M.,Sagebiel, John C.,Chow, Judith C.,Watson, John G.
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p. 2080 - 2091
(2007/10/03)
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- HAPs release from wood drying
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Hazardous Air Pollutant (HAP) profiles from drying softwood and hardwood flakes (for the manufacture of oriented strand board) are very similar, indicating that they originate through a common mechanism, the breakdown of wood tissue. Hence, the strategies employed to reduce VOC (volatile organic compound) emissions from hardwood can also be extended to decreasing HAPs from softwood. Drying aspen flakes in the field and in the laboratory gives rise to different VOC species, and direct extension of laboratory data to the field may prove difficult. Formaldehyde emissions from drying fresh aspen flakes are lower than those from stored material; the opposite effect occurs for methanol and the other aldehydes. HAPs evolved from drying pine flakes surge sharply at 5-10% moisture content during drying at 130-160 °C. Emissions of methanol, formaldehyde, pentanal, and hexanal all begin simultaneously, with the release of methanol and formaldehyde being the most sensitive to dryer temperature. Hence, the nature of the VOC mix is partly governed by the dryer temperature. Pine and aspen give rise to similar HAPs profiles during either drying or pressing flakes that are already dried.
- Otwell, Lawrence P.,Hittmeier, Michael E.,Hooda, Usha,Yan, Hui,Su, Wei,Banerjee, Sujit
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p. 2280 - 2283
(2007/10/03)
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- Chemoselective removal of allylic formyloxy group using SmI2
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A variety of allylic formates are chemoselectively transformed into th corresponding olefins in excellent yields on treatment with SmI2 in THF-HMPA-H2O (20:5:1), even though allylic acetate and allylic ether groups are present in the same molecule.
- Shibuya,Shiratsuchi
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p. 431 - 449
(2007/10/02)
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- Isomerization of 1-alkenes using the Na2Fe(CO)4/CuCl and Na2Fe(CO)4/BrCH2CH2Br reagent systems
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The reagent Na2Fe(CO)4 prepared in situ in THF by the reduction of Fe(CO)5 with sodium naphthalenide reacts with certain alkenes in the presence of CuCl to bring about isomerization of the alkenes.Thus the 1-alkenes (1-dodecene, 1-decene, safrole and allyl benzene) are isomerized to trans-2-alkenes, and β-pinene is isomerized to α-pinene.Reactions involving BrCH2CH2Br in place of CuCl give similar results.Keywords: Isomerization; Supernucleophile; Iron tetracarbonyl; Iron-copper bonds; Iron pentacarbonyl; Copper(I) chloride
- Reddy, Malladi Rama,Periasamy, Mariappan
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p. 263 - 266
(2007/10/02)
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Reaction of alkyl hydroperoxides (1(ary), 2(ary) or 3(ary)) upon tertiary alkyl trichloroacetimidates under acidic catalysis yielded unsymmetrical dialkyl peroxides with yields in the range 30-70%.
- Bourgeois,Montaudon,Maillard
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p. 2477 - 2484
(2007/10/02)
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- Palatable solid pesticidal compositions of ethylene and vinyl acetate copolymer
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The invention comprises compositions in solid form of ethylene/vinyl acetate copolymer with an effective amount of bioactive agent, a protein/carbohydrate-lipid source, 0 to 20% of an edible oil and optionally an attractant, dye, preservative, adversive agent and biomarker and the use, thereof, to control pests.
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- CHEMOSELECTIVE REDUCTIONS WITH SODIUM BOROHYDRIDE. ALDEHYDES VS. KETONES
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Aldehydes can be reduced in the presence of ketones by sodium borohydride in 30percent ethanol in dichloromethane at -78 deg C.The selectivity is generally greater than 95percent.
- Ward, Dale E.,Rhee, Chung K.
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p. 1927 - 1934
(2007/10/02)
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- Hydrogenation of Conjugated Olefins by Dichlorobis(benzylcyano)palladium(II)
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A homogeneous solution of trans-dichlorobis(benzylcyano)palladium(II) in benzene has been used for the hydrogenation of conjugated double bonds and nitro groups at room temperature and atmospheric pressure.Isomerization of exocyclic double bond in β-pinene to endocyclic double bond to afford α-pinene is also catalysed.
- Choudhary, B. M.
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- CHIRAL SYNTHESIS VIA ORGANOBORANES. 2. RAPID REACTION OF BORONIC ESTERS OF VERY HIGH OPTICAL PURITY WITH LITHIUM ALUMINUM HYDRIDE. FACILE REACTION OF ESSENTIALLY OPTICALLY PURE BORINIC ESTERS WITH LITHIUM MONOETHOXYALUMINOHYDRIDE. A NOVEL AND QUANTITATIVE SYNTHESIS OF LITHIUM MONOALKYL- AND DIALKYLBOROHYDRIDES OF ESSENTIALLY 100% OPTICAL PURITY.
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Boronic esters of very high optical purity readily react with lithium aluminum hydride in diethyl ether-pentane at 0 degree C to form the corresponding lithium monoalkylborohydrides of very high optical purity and dialkoxyalane. Under these reaction conditions the dialkoxyalane generally precipitates quantitatively from solution. The reaction is essentially quantitative and is broadly applicable to a representative variety of essentially optically pure boronic esters. Addition of 1 mol equiv of very high optically pure borinic esters to lithium monoethoxyaluminohydride in diethyl ether at 0 degree C results in a facile and rapid precipitation of the dialkoxyalane as a solid, producing the corresponding lithium dialkylborohydride of very high optical purity in quantitative yield. The reaction is quite general, proceeds without detectable racemization, and is applicable to essentially optically pure borinic esters of widely varied structural requirements.
- Brown,Singaram,Cole
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p. 460 - 464
(2007/10/02)
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- Dehydrogenation of β-Pinene to p-Cymene over Platinum-Alumina Catalyst in the Presence of Nitrogen, Hydrogen and Pyridine
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Dehydrogenation of β-pinene has been carried out over platinum-alumina (0.6percent Pt) catalyst at 300 deg C in the presence of nitrogen, hydrogen and pyridine.Nitrogen acts as a diluent while hydrogen acts both as a diulent and as a promoter.Pyridine on the other hand functions as a diluent and as a poison.As a result, it affects the formation of different products to different extent.The optimum conditions such as platinum concentration, temperature and contact time for dehydrogenation, hydrogenation and disproportionation reactions were established using cyclohexane, p-cymene and cyclohexene, respectively before actually studying the d ehydrogenation of β-pinene.
- Krishnasamy, V.,Mathur, Pravin,Chandrasekharan, K.
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- Rearrangement of Pinane Derivatives. Part 8. Deamination of 2αH-Pinan-3α-ylamine
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Solvolysis of 2αH-pinan-3α-yl toluene-p-sulphonate has been shown to proceed with concomitant 1,2-hydride shift to give the pinan-2-yl carbocation.Contrary to earlier reports, this species reacts normally to give, in good yield, pinan-2-yl substitution products.In contrast the pinan-3-ylamines react via a similar route, but give much smaller amounts of pinan-2-yl products.The usual reasons for differences between solvolysis and deamination (i.e. the intermediacy of diazonium ions and/or high-energy ions) can be discounted, and possible reasons for the differences in behaviour are discussed.
- Giddings, Rodney M.,Jones-Parry, Richard,Salmon, J. Roger,Whittaker, David
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p. 725 - 728
(2007/10/02)
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- Transformations of β-Pinene over Platinum-Alumina Catalyst. Part-I: Influence of Contact Time, Temperature and Platinum Concentration
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The catalytic transformations of β-pinene have been investigated over platinum-alumina dual function catalyst containing varying amounts of platinum in the temperature range 200 to 400 deg C.In addition, the influence of contact time on the rate and distribution of products has been studied over 0.6percent platinum-alumina at 300 deg C.The performance of the catalyst remains unchanged by its pretreatment either in hydrogen or in oxygen prior to catalytic run.The dehydrogenation activity of the catalyst increases upto 350 deg C beyond it declines. β-Pinene isomerizes via two parallel paths: one giving rise to bi- and tricyclic products such as camphene, α-pinene, bornylene and tricyclene and the other giving monocyclic compounds such as dipentene, terpinolene, α- and γ-terpinenes.The terpinenes have been identified as the immediate precursors of cymene.Apart from this, the terpinenes undergo disproportionation to menthenes and menthanes.At higher values of contact time and temperature, menthenes and menthanes get dehydrogenated to cymenes.Increase of platinum concentration inhibits both isomerization and dehydrogenation activities of the catalyst.This decrease is ascribed to reduction of the acid sites and enhancement of platinum crystallite size.Disproportionation reaction is favoured by strong acid sites and small well dispersed platinum crystallites.
- Mathur, P.,Krishnasamy, V.,Chandrasekharan, K.
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p. 970 - 974
(2007/10/02)
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- Isomerization of β-pinene in the Vapour Phase over Alumina Catalyst: Influence of Partial Pressure of Nitrogen and Pyridine
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The isomerization of β-pinene in the vapour phase over alumina catalyst has been studied in the presence of nitrogen and pyridine.The isomerization proceeds via two parallel paths, one giving bicyclic products such as α-pinene and camphene and the other giving rise to monocyclic menthadienes such as dipentene, terpinolene, α-terpinene and γ-terpinene.Nitrogen acts as a diluent while pyridine functions as a diluent and as a poison.As a result, it affects the formation of different products to different extent.The isomerization of β-pinene over alumina follows a second order kinetics.Based on the experimental facts a tentative mechanism, in terms of carbonium ion intermediates, has been proposed.
- Krishnasamy, V.,Ratansamy, P.
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p. 1151 - 1154
(2007/10/02)
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- REACTIONS OF TERPENES IN DIPOLAR APROTIC SOLVENTS. PART III. ISOMERIZATION OF SOME MONOTERPENE HYDROCARBONS
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Acyclic (myrcene, ocimene, alloocimene), monocyclic (limonene) and bicyclic (α-pinene, β-pinene, (+)-3-carene) terpene hydrocarbons heated in dipolar aprotic solvents (DMF, DMSO, TMS) undergo complex conversions where isomerization processes prevail.The isomerization degree of particular hydrocarbons depends both on the structure of initial compound and the type of solvent used.
- Matawowski, Aleksander
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p. 469 - 479
(2007/10/02)
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