- Aldol Condensation of Butan-2-one and Pentan-3-one on an Activated Alumina as Monotored via in-situ Carbon-13 Nuclear Magnetic Resonance Spectroscopy
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Conventional (13)C nuclear magnetic resonance spectroscopy is used to monitor the reactions of butan-2-one and pentan-3-one adsorbed on alumina.Both reaction sequences proceed via successive aldol condensations.The products observed for butan-2-one (5-methyl-4-hepten-3-one and 4-hydroxy-4-methylpentan-2-one) are those expected for homogeneous base catalysis.A J-modulated spin-echo sequence demonstrates that 5-ethyl-4-methyl-5-hepten-3-one, the β,γ condensation product, is obtained using pentan-3-one.The results demonstrate that conventional (13)C n.m.r. can be effectively used to distinguish reaction pathways and products for surface catalysed reactions.
- Bell, Valerie A.,Carver, Robert F.,Dybowski, Cecil,Gold, Harvey S.
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- Calcium oxide supported on monoclinic zirconia as a highly active solid base catalyst
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Calcium oxide supported on ZrO2 is a highly active catalyst for base-catalyzed reactions such as aldol-type reactions and transesterification reactions. The role of key parameters during preparation, that is, impregnation versus precipitation, heat treatment, and metal oxide loading on the basicity and catalytic activity were investigated for CaO supported on ZrO2. An impregnation of 10 wt % CaO on monoclinic zirconia followed by heat treatment at 600°C resulted in high activity for the self-condensation reaction of acetone. An evaluation of a series of CaO/ZrO2 samples with different loadings showed that the activity increased for impregnated amounts per gram catalyst of 0-10 wt % CaO, and at higher loading the activity decreased as a result of a decrease in dispersion. The number of strong base sites (calculated from CO2 desorbed at temperatures higher than 625°C) correlated with the activity. For MgO, CaO, SrO, and BaO on zirconia the catalytic activity increased as the ionic radius of the metal cation increased, suggesting the impact of base strength on catalytic performance. Look at the strong base! If prepared in an optimized way, CaO/ZrO2 is a highly active solid base catalyst. Calcination temperature and the preparation method (impregnation or deposition) have a strong influence on the number of strong base sites, which correlate positively with the activity of the material. Copyright
- Frey, Anne Mette,Van Haasterecht, Tomas,De Jong, Krijn P.,Bitter, Johannes Hendrik
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- Ozonolysis of enol ethers. Part 8. Ozonation of (1-methoxy-2-methylprop-1-enyl)-1,1′-biphenyl in comparison with related oxygenations
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The results of conversions of 4-(1-methoxy-2-methylprop-1-enyl)-1,1′-biphenyl (19) with ozone and with dimethyldioxirane (6b) under 'normal' and 'inverse' conditions are compared with oxygenations by dioxygen under thermal and sensitized photochemical conditions, as well as with the photooxygenation of epoxide 17, formally derived from 19. Ozone consumption varies between 0.7 and 1 mol-equiv. amounts, peroxidic species are not formed. Except for bicyclus 24, ali conversions lead to mixtures of the same [1,1′-biphenyl]-4-yl compounds which only differ by varying percentages. It is concluded that ozonolysis of C=C bonds only represents a special type of electron-transfer oxygenation.
- Schank, Kurt,Weiter, Matthias
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- Analysis of Minor Components by Ultrahigh Resolution NMR. 2. Detection of 0.01percent Diacetone Alcohol in "Pure" Acetone and Direct Measurement of the Rate of the Aldol Condensation of Acetone
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Ultrahigh resolution NMR methodology permits the detection of as little as 0.01percent CH3COCH2(OH)C(CH3)2 (2) in a sample of "pure" acetone (1) of natural isotopic composition, with the use of the methyl resonances in the proton-decoupled (13)C NMR spectrum, even though the resonances of 2 are very close to those of 1.Also, all three peaks of the triplet of the (13)CH2D carbon of (13)CH2D-(12)CO-(12)CH3 are fully resolved, even though their intensity is only 0.015percent of that of the main contributor to the spectrum, (13)CH3-(12)CO-(12)CH3, and one of the peaks of the triplet is only 7 Hz away from the main acetone peak.The intensities of the (13)CH2D triplet serve as a calibrator of dynamic range accuracy in (13)C NMR measurements of relative proportions of major and minor components.After addition of aqueous sodium hydroxide to the acetone sample, the growth of the methyl carbon resonances of 2 provides a direct measurement of the rate constant for the aldol dimerization of 1 and also the equilibrium constant for this reaction.This example demonstrates the ability of ultrahigh resolution NMR to study directly the kinetics of reactions that have equilibria highly displaced toward the reagents, instead of the traditional procedure of monitoring only the kinetics of the reverse reaction by starting with pure "products".Artifacts that may interfere with the study of minor components by ultrahigh resolution NMR are discussed.
- Maple, Steven R.,Allerhand, Adam
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- Kinetics by Thermometry: An Aldol Condensation Reaction
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The princilpes of 'thermokinetic' experiments have been described, whereby the initial rates of chemical reaction in solution are determined by following the temperature rise in an adiabatic system; data are obtained within the first few seconds of mixing, and at rates of the order of one measurement s-1.The procedure has been applied to the base-catalysed condensation reaction of acetone to form diacetone alcohol, an exceptionally difficult reaction to follow because of the small extent to which the reaction proceeds.At 26 deg C, the equilibrium constant for the base-catalysed ionisation of acetone has been established as having a value of 1.2(9) l mol-1 while the rate constant for the ionic dimerisation has the value 2.5(2)E-3 mol l-1 s-1.
- Eskendirov, Igor,Kabongo, Bukasa,Glasser, Leslie,Sokolovskii, Valery D.
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- Catalysis by cobalt compounds of aldol and retroaldol reactions
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Aldol condensation of acetone, butanone, and 2-pentanone, and retroaldol reaction of neat diacetone alcohol and 3-methyl-3-hydroxyheptan-5-one are catalyzed by (Ph3P)3CoCH3 and (Ph3P)3CoSi(CH3)3.The condensations are reversible and the retroaldol reaction is favoured.Several hindered or cyclic ketones, such as higher homologues, 3-pentanone, methyl isopropyl ketone or cyclohexanone do not condense.By comparison, aliphatic aldehydes react fast and irreversibly to yield products comprised of three aldehyde units. (Ph3P)3CoCH3 also catalyzes protium/deuterium scramblingbetween ketones and acetone-d6.This exchange takes place preferably at the C3 carbon whereas condensation takes place at the C1 carbon.The reactions take place at 20 deg C or below, and of the several organometallic compounds tested only the two mentioned above were found to be active.
- Tencer, Y.,Michman, M.,Goldenfeld, I.
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- Design and application of the recyclable poly(l-proline-co-piperidine) catalyst for the synthesis of mesityl oxide from acetone
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Unexpectedly, l-proline/piperidine was found to be a better recyclable catalyst system than l-proline or piperidine alone in the condensation of acetone to prepare mesityl oxide (MO), an important intermediate in the chemical industry. Binding the catalyst system onto polymer resin enhanced the MO selectivity and reduced the catalyst loss. The mechanism of the bi-component catalyst system was also studied through control reactions, as well as by dynamic calculations. The MO selectivity could reach 74.4% and its isolated yield could reach 73.9%, based on the consumed acetone. Although the result does not immediately meet the requirement of industrial production, this study provides a novel organocatalyst system, which might offer a potential alternative to traditional inorganic catalysts that can be used under mild and neutral conditions.
- Xu, Lin,Huang, Jiejun,Liu, Yubing,Wang, Yining,Xu, Bolian,Ding, Kehong,Ding, Yuanhua,Xu, Qing,Yu, Lei,Fan, Yining
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- Continuous synthesis of triacetonamine over sulfonic acid-functionalized mesoporous silicas
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The continuous synthesis of triacetonamine from acetone and ammonia was realized over sulfonic acid-functionalized mesoporous silicas. These catalysts were characterized by TG, XPS, BET, elemental analysis and acid-base titration. The results indicated th
- Tian, Jun,Chen, Ligong,Zhang, Chao,Yan, Xilong,Li, Yang
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- The mechanism of catalyst deactivation and by-product formation in acetone ammoximation catalyzed by hollow titanium silicalite
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The deactivation mechanism of hollow titanium silicalite (HTS) in aqueous ammoximation of acetone was investigated. Amines and polynitro-compounds, formed by alkaline autocatalytic and oxidative coupling reaction respectively, were determined to be the ma
- Wang, Yi,Zhang, Shengjian,Zhao, Yingxian,Lin, Min
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- L-Proline and thiourea co-catalyzed condensation of acetone
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Amino acid and primary amine/amide co-catalyzed acetone condensation was investigated. It was found that L-proline had overwhelming catalytic activity over other amino acids as well as the analogues with similar structures. Surprisingly, thiourea, a very cheap and stable chemical, was found to be the favorable co-catalyst. Co-catalyzed by the recyclable L-proline and thiourea, condensation of acetone led to the useful products mesityl oxide (MO), diacetone alcohol (DAA) and isophorone (IP) in the excellent 96.3% total selectivity.
- Xu, Lin,Wang, Fang,Huang, Jiejun,Yang, Chenggen,Yu, Lei,Fan, Yining
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- Kinetics and products of the reactions of selected diols with the OH radical
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Using a relative rate method, rate constants been measured at 296 ± 2 K for the gas-phase reactions of OH radicals with 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, and 2-methyl-2,4-pentanediol, with rate constants (in units of 10-12 cm3 molecule-1 s-1) of 27.0 ± 5.6, 23.6 ± 6.3, 33.2 ± 6.8, and 27.7 ± 6.1, respectively, where the error limits include the estimated overall uncertainty of ±20% in the rate constant for the reference compound. Gas chromatographic analyses showed the formation of 1-hydroxy-2-butanone from 1,2-butanediol, 3-hydroxy-2-butanone from 2,3-butanediol, 1-hydroxy-3-butanone from 1,3-butanediol, and 4-hydroxy-4-methyl-2-pentanone from 2-methyl-2,4-pentanediol, with formation yields of 0.66 ± 0.11, 0.89 ± 0.09, 0.50 ± 0.09, and 0.47 ± 0.09, respectively, where the indicated errors are the estimated overall uncertainties. Pathways for the formation of these products are presented, together with a comparison of the measured and estimated rate constants and product yields.
- Bethel, Heidi L.,Atkinson, Roger,Arey, Janet
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- The OH-initiated oxidation of hexylene glycol and diacetone alcohol
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The OH-initiated oxidation of two VOCs directly emitted to the atmosphere through their use as industrial solvents, hexylene glycol (HG, (CH 3)2C(OH)CH2CH(OH)CH3) and diacetone alcohol (DA, (CH3)2C(OH)CH2C(O)CH3), has been studied in two photoreactors: a 140 L Teflon bag irradiated by lamps at CNRS-Orleans and the 200 m3 European photoreactor, EUPHORE, irradiated by sunlight. The rate constants for the reactions of HG and DA with OH radicals have been determined at (298 ± 3) K using a relative rate method: kHG = (1.5 ± 0.4) x 10-11 and k DA (3.6 ± 0.6) x 10-12 cm3 molecule -1 s-1 and have been found in good agreement with estimations from structure-reactivity relationships. The study at Orleans and EUPHORE of the OH-initiated oxidation of hexylene glycol showed the formation of diacetone alcohol, acetone, and PAN as the principal products. The branching ratio of the H-atom abstraction from the > CH- group of HG has been estimated to be (47 ± 4)% corresponding to the measured formation yield of DA. The formation yields of acetone and PAN lead to the determination of a lower limit of (33 ± 7)% for the branching ratio of the H-atom abstraction of the -CH2-group of HG. For diacetone alcohol, studies at EUPHORE have shown negligible photolysis under atmospheric conditions (J -6 s-1) and the formation of acetone, PAN, HCHO, and CO in the OH-initiated oxidation experiments. The molar yield of acetone, close to 100%, corresponds to the branching ratio of the H-atom abstraction from the -CH2- group of DA. The present study has allowed the identification of the nature and the fate of the oxy radicals as intermediates in the oxidation mechanism of both HG and DA. The atmospheric implication of these results, especially the ozone formation potential of HG and DA, is discussed.
- Magneron,Bossoutrot,Mellouki,Laverdet,Le Bras
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- The enthalpy of acetone
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Measurements of the specific enthalpy increment of acetone are reported; 206 measurements cover the range 373.2 to 623.2 K at pressures from 0.1 to 11.9 MPa.The overall accuracy is 0.6 per cent.The specific enthalpy of the saturated liquid and of the saturated vapour and the enthalpy of vaporization are derived from the measurements.Comparison with cubic equations of state shows that the Patel-Teja equation is the best of those tested.
- Yerlett, T. K.,Wormald, C. J.
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- Kinetics and Equilibrium Data of the Dehydration-Hydration Reaction between Diacetone Alcohol and Mesityl Oxide in Phosphoric Acid
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The velocities of dehydration of diacetone alcohol and hydration of mesityl oxide were studied in regions of 8.6-85.2percent phosphoric acid.Because the reactions are acid-catalyzed, the reaction velocities in both directions were increased as the acid concentration increased.The reaction kinetics fit the reversible first-order model with respect to the concentration of reactants, including the activity of water.These results are consisted with the mechanisms proposed by a previous investigator in which the rate-determining step is addition or removal of protons.Equilibrium constants were derived from solution composition and specific rate constants which agreed with each other.The equilibrium constant did not change with with acid concentration in the dilute range, but increased slightly at higher acid concentrations.The reaction velocities and the equilibrium constants increased with increasing temperature, and the activation energies were 18.8 and 12.7 kcal/mol for the dehydration and hydration reactions, respectively.
- Kim, Yong K.,Hatfield, John D.
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- Synthesis of the 10-oxabicyclo[5.2.1]decane framework present in bioactive natural products
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The present work deals with the synthesis of the 10-oxabicyclo[5.2.1]decane framework present in bioactive natural products like physalins, with potential as antitumor agents. This synthetic methodology involves several key reactions: (a) synthesis of polyfunctionalized cycloheptenones by [4 + 3] cycloaddition reactions of furan precursors with oxyallyl cations; (b) Nicholas reaction with propargyl cations stabilized as dicobalt hexacarbonyl complexes; (c) demetallation and hydration of the resulting acetylenes; (d) stereoconvergent aldol cyclization to generate a key oxatricyclic intermediate and (e) a β-fragmentation process that affords, under hypoiodite photolysis, the desired product with moderate to good yield. The final compounds are the result of a radicalary β-fragmentation at the level of C2-C6 with respect to the tertiary hydroxyl group on C6, with an unexpected contraction from a ten- to a nine-membered ring system, via a radical addition to the carbonyl group on C4. The synthetic methodology has been scaled up to multigram level with good overall yield. Further biological, biochemical and biophysical studies are being carried out in our laboratory on these 1,7-epoxycyclononane derivatives to determine the potential of this kind of oxabicyclic compound as future hits and/or leads for the development of new anticancer drugs. The preliminary evaluation of the anticancer activity of the representative synthesized compounds, against the leukaemia cancer cell lines K-562 and SR, shows a promising activity with a GI50 = 0.01 μM and a LC50 = 7.4 μM for a conveniently functionalized 10-oxabicyclo[5.2.1]decane.
- Monta?a, ángel M.,Ponzano, Stefano,Sanasi, Maria-Filomena,Kociok-K?hn, Gabriele
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- Comparative study of the catalytic behaviour of Ru(III) and Ru(VI) on the oxidation of alcohols by hexacyanoferrate(III)
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The oxidation reactions of 2-methyl-2,4-pentanediol upon treatment with alkaline hexacyanoferrate(III) using Ru(III) or Ru(VI) as catalysts are governed by two quasi-identical experimental rate equations, which show that both catalysts are equally effective for the oxidation of alcohols by Fe(CN)63-. The reaction mechanism proposed involves the oxidation of 2-methyl-2,4-pentanediol by the catalyst, a process that occurs through the formation of a substrate-catalyst complex. The decomposition of this complex yields Ru(IV) and a protonated ketone (owing to a hydride transfer from the α-C - H bond of the alcohol to the oxoligand of ruthenium) in the case of Ru(VI), but a ketyl radical and Ru(II) (hydrogen transfer) for Ru(III). The role of the co-oxidant, Fe(CN)63-, is to regenerate the catalyst. For both oxidation reactions, the rate constants of complex decomposition and catalyst regeneration have been determined. Copyright
- Mucientes,Gabaldon,Poblete,Villarreal
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- On the Metal Cooperativity in a Dinuclear Copper–Guanidine Complex for Aliphatic C?H Bond Cleavage by Dioxygen
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Selective oxidation reactions of organic compounds with dioxygen using molecular copper complexes are of relevance to synthetic chemistry as well as enzymatic reactivity. In the enzyme peptidylglycine α-hydroxylating monooxygenase (PHM), the hydroxylating activity towards aliphatic substrates arises from the cooperative effect between two copper atoms, but the detailed mechanism has yet to be fully clarified. Herein, we report on a model complex showing hydroxylation of an aliphatic ligand initiated by dioxygen. According to DFT calculations, the proton-coupled electron-transfer (PCET) process leading to ligand hydroxylation in this complex benefits from cooperative effects between the two copper atoms. While one copper atom is responsible for dioxygen binding and activation, the other stabilizes the product of intramolecular PCET by copper–ligand charge transfer. The results of this work might pave the way for the directed utilization of cooperative effects in oxidation reactions.
- Sch?n, Florian,Biebl, Florian,Greb, Lutz,Leingang, Simone,Grimm-Lebsanft, Benjamin,Teubner, Melissa,Buchenau, S?ren,Kaifer, Elisabeth,Rübhausen, Michael A.,Himmel, Hans-J?rg
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- An active and stable multifunctional catalyst with defective UiO-66 as a support for Pd over the continuous catalytic conversion of acetone and hydrogen
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The one-pot synthesis of methyl isobutyl ketone (MIBK) and methyl isobutyl methanol (MIBC) from acetone and hydrogen is a typical cascade reaction comprised of aldol condensation-dehydration-hydrogenation. Pd loss and aggregation during long term operation are typical problems in industrial application. In this paper, an active and stable catalyst was achieved with defective UiO-66 as a support for Pd, which was synthesized with the ratio 15?:?1 of ZrOCl2·8H2O to ZrCl4as Zr-precursors. The resultant Pd catalyst remained active for at least 1000 h with a MIBK + MIBC selectivity of 84.87-93.09% and acetone conversion of 45.26-53.22% in a continuous trickle-bed reactor. Besides the increased Br?nsted acid amount generated by the defect sites was favorable for the activity, the cavity confinement in the UiO-66 (R= 15?:?1) structure also efficiently prevented Pd loss and aggregation during the long term run. The contrast of the characterization of the fresh and used Pd/UiO-66 (R= 15?:?1) indicated that the deactivation of the catalyst was attributed to carbonaceous accumulation on the catalyst surface, which could be easily regenerated by calcination. This work supplied a new alternative for the design and utilization of industrial catalysts for MIBK and MIBC synthesis.
- Hu, Yingjie,Mei, Yuxin,Lin, Baining,Du, Xuhong,Xu, Fan,Xie, Huasheng,Wang, Kang,Zhou, Yonghua
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- Method for preparing triacetone amine
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An improved method is used for preparing triacetone amine while recycling the by-products. This involves treating the crude product from triacetone amine preparation, which leads to an increase in the content of compounds which react readily with ammonia. This method enables efficient recycling of the by-products formed in the synthesis of triacetone amine.
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Paragraph 0133-0144
(2020/07/05)
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- New technology for co-production of dimethyl hexylenediol and diacetone alcohol
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The invention provides a new technology for co-production of dimethyl hexylenediol and diacetone alcohol, and belongs to the technical field of organic fine chemical preparation. According to the technology, methylbutynol and acetone serve as raw materials and are subjected to a reaction under the catalytic effect of alkali in a reaction solvent, then hydrolysis and layering are conducted, and theproducts dimethyl hexylenediol and diacetone alcoho are obtained after an upper-layer oil phase is washed for dealkalization, neutralized and rectified; lower-layer alkali liquor is recycled after catalyst regeneration, and water generated in the process is used for washing and hydrolysis. By means of the technology, co-production of the dimethyl hexylenediol and diacetone alcohol can be achieved, the total yield of the dimethyl hexylenediol and diacetone alcohol on the acetone is about 96%, the yield of the dimethyl hexylenediol on the methylbutynol is about 93%, and the mole ratio of the dimethyl hexylenediol to the diacetone alcohol is larger than 0.22 and is adjustable. By means of the technology, fixed investment and production cost can be effectively lowered, the added value of products, the utilization rate and the market resilience of devices are significantly increased, and the economic benefit increment is considerable.
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Paragraph 0026-0038
(2019/07/01)
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- Complete Switch of Reaction Specificity of an Aldolase by Directed Evolution In Vitro: Synthesis of Generic Aliphatic Aldol Products
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A structure-guided engineering of fructose-6-phosphate aldolase was performed to expand its substrate promiscuity toward aliphatic nucleophiles, that is, unsubstituted alkanones and alkanals. A “smart” combinatorial library was created targeting residues D6, T26, and N28, which form a binding pocket around the nucleophilic carbon atom. Double-selectivity screening was executed by high-performance TLC that allowed simultaneous determination of total activity as well as a preference for acetone versus propanal as competing nucleophiles. D6 turned out to be the key residue that enabled activity with non-hydroxylated nucleophiles. Altogether 25 single- and double-site variants (D6X and D6X/T26X) were discovered that show useful synthetic activity and a varying preference for ketone or aldehyde as the aldol nucleophiles. Remarkably, all of the novel variants had completely lost their native activity for cleavage of fructose 6-phosphate.
- Junker, Sebastian,Roldan, Raquel,Joosten, Henk-Jan,Clapés, Pere,Fessner, Wolf-Dieter
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supporting information
p. 10153 - 10157
(2018/07/31)
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- Why is cis/trans stereoinversion with Li+(THF)4 migration across the phenyl ring of α-lithiostyrene accelerated by two ortho-methyl groups?
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Common wisdom might anticipate that two methyl groups placed on a molecular migration route should act as an impediment. However, the “conducted tour” migration of Li+(THF)4 across the aryl ring (“π-route”) during the cis/trans stereoinversion of α-arylvinyllithiums had been found to occur with practically equal velocities in the presence of either one or two ortho-alkyl substituents. We now report that the omission of both ortho-methyl groups retards the stereoinversion process. In order to arrive at an answer to the title question, we investigate the aggregation equilibria and microsolvation states of ortho, ortho′-unsubstituted α-lithiostyrenes by means of approved secondary NMR criteria. Beyond such necessary knowledge about the ground-state properties, we provide kinetic evidence showing that the retarded cis/trans stereoinversion of α-lithiostyrene proceeds by the pseudomonomolecular, ionic mechanism with Li+(THF)4 migration.
- Knorr, Rudolf,Lattke, Ernst,Ruhdorfer, Jakob,Ferchland, Kathrin,von Roman, Ulrich
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supporting information
p. 1621 - 1631
(2018/02/28)
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- Fabrication of Pd-based metal-acid-alkali multifunctional catalysts for one-pot synthesis of MIBK
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The one-pot synthesis of methyl isobutyl ketone (MIBK) from acetone using multifunctional catalysts is an important sustainable organic synthesis method with high atom and energy efficiency. Herein. we report a series of Pd supported on mixed metal oxide (MMO) catalysts with controllable acidic/basic/metallic sites on the surface. We study the relationship between the nature, synergy, and proximity of active sites and the catalytic performance of the multifunctional catalyst in the tandem reaction, in detail. In the existence of Lewis acid and base sites, the catalysts with medium-strength acidic/basic sites show preferred activity and/or MIBK selectivity. For multifunctional catalysts, the catalytic properties are more than just a collection of active sites, and the Pd/Mg3Al-MMO catalyst possessing 0.1% Pd loading and ~0.4 acid/base molar ratio exhibits the optimal 42.1% acetone conversion and 37.2% MIBK yield, which is among the best reported so far for this tandem reaction under similar conditions. Moreover, the proximity test indicates that the intimate distance between acidic/basic/metallic sites can greatly shorten the diffusion time of the intermediate species from each active site, leading to an enhancement in the catalytic performance.
- Ma, Rui,Li, Yunpeng,Wu, Guandong,He, Yufei,Feng, Junting,Zhao, Yingying,Li, Dianqing
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p. 1384 - 1394
(2018/07/14)
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- CXCR4 INHIBITORS AND USES THEREOF
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The present invention provides compounds, compositions thereof, and methods of using the same.
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Paragraph 00424; 00425
(2018/04/11)
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- A continuous method for producing two acetol method
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The invention discloses a method for producing diacetone alcohol through a continuous method. The method comprises the following steps: continuously feeding acetone into a continuous reactor through a pump, continuously conveying material liquid after reaction to a distillation tower, continuously distilling in the distillation tower for removing most unreacted acetone, continuously conveying material liquid to a secondary distillation tower, distilling for removing residual acetone so as to obtain a diacetone alcohol crude product, continuously conveying acetone distilled out from the distillation tower and the secondary distillation tower to the continuous reactor for continuous reaction, continuously conveying the diacetone alcohol crude product obtained through distillation to a product distillation tower and continuously separating a diacetone alcohol finished product from the distillation tower. The method for producing diacetone alcohol through the continuous method, provided by the invention, has the characteristics that equipment investment is less, high productivity, low energy consumption in the production process, and no three waste emission are realized, and the product diacetone alcohol is stable in quality, 99.5-99.9% in the content and high in quality.
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Paragraph 0024-0026
(2017/08/04)
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- Towards understanding the hydrodeoxygenation pathways of furfural-acetone aldol condensation products over supported Pt catalysts
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Aiming at the valorisation of furfural-derived compounds, the hydrodeoxygenation of furfural-acetone condensation products has been studied using supported platinum catalysts. The influence of the catalytic properties of different supports, such as SiO2, Al2O3, TiO2, hydrotalcite (HTC), Beta zeolite, Al-SBA-15 and WO3-ZrO2, was evaluated in a batch reactor for 480 min at 200 °C and 50 bar of H2. The used feed consisted of a mixture of furfural-acetone adducts (C8-C19), obtained in previous experiments using a continuous flow reactor and hydrotalcite as a catalyst. Except for Pt/SiO2, all catalysts showed high conversion of the reactants, especially due to the hydrogenation of all the aliphatic CC bonds. However, the extent of further hydrogenation (furan CC and ketone CO bonds) was limited, particularly when HTC and Al2O3 were used as supports. The higher accessibility of Pt/TiO2 and the smaller Pt particle size shown by Pt/Al-SBA-15, Pt/WO3-ZrO2 and Pt/Beta in comparison with the other catalysts led to an improvement in the hydrogenation of furanic and ketonic groups, likely due to lower adsorption constraints. The higher acid character of the latter group of catalysts promotes dehydration and ring opening steps, thus enhancing the selectivity towards linear alcohols. Likewise, a significant increase in the extent of aldol condensation reactions was also observed with these catalysts, yielding longer carbon chain compounds. Based on this study, a reaction scheme for the transformation of 4-(2-furyl)-3-buten-2-one (C8) into octane has been proposed in order to establish a valuable correlation between the main conversion pathways and the catalytic properties of the employed heterogeneous catalyst, thus contributing to further development of efficient deoxygenation catalysts.
- Ramos,Ti?ler,Kikhtyanin,Kubi?ka
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p. 1829 - 1841
(2016/04/05)
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- Acceptorless Dehydrogenative Oxidation of Secondary Alcohols Catalysed by Cp*IrIII–NHC Complexes
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A series of new IrIIIcomplexes with carbene ligands that contain a range of benzyl wingtip groups have been prepared and fully characterised by NMR spectroscopy, HRMS, elemental analysis and X-ray diffraction. All the complexes were active in the acceptorless dehydrogenation of alcohol substrates in 2,2,2-trifluoroethanol to give the corresponding carbonyl compounds. The most active complex bore an electron-rich carbene ligand; this complex was used to catalyse the highly efficient and chemoselective dehydrogenation of a wide range of secondary alcohols to their respective ketones, with turnover numbers up to 1660. Mechanistic studies suggested that the turnover of the dehydrogenation reaction is limited by the H2-formation step.
- Gülcemal, Süleyman,Gülcemal, Derya,Whitehead, George F. S.,Xiao, Jianliang
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supporting information
p. 10513 - 10522
(2016/07/21)
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- SYNTHESIS OF DIACETONE ALCOHOL AND MESITYL OXIDE
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Processes for synthesizing diacetone alcohol from acetone are provided. An exemplary process includes contacting acetone with a heterogeneous catalyst at a temperature of less than 100 °C, to provide diacetone alcohol. The heterogeneous catalyst can include molecular sieves. Processes for synthesizing mesityl oxide from acetone are also provided.
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Paragraph 0046
(2016/02/26)
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- Studies on the low-temp oxidation of coal containing organic sulfur and the corresponding model compounds
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This paper selects two typical compounds containing organic sulfur as model compounds. Then, by analyzing the chromatograms of gaseous low-temp oxidation products and GC/MS of the extractable matter of the oxidation residue, we summarizing the mechanism of low-temp sulfur model compound oxidation. The results show that between 30 °C to 80 °C, the interaction between diphenyl sulfide and oxygen is mainly one of physical adsorption. After 80 °C, chemical adsorption and chemical reactions begin. The main reaction mechanism in the low-temp oxidation of the model compound diphenyl sulfide is diphenyl sulfide generates diphenyl sulfoxide, and then this sulfoxide is further oxidized to diphenyl sulphone. A small amount of free radicals is generated in the process. The model compound cysteine behaves differently from diphenyl sulfide. The main reaction low-temp oxidation mechanism involves the thiol being oxidized into a disulphide and finally evolving to sulfonic acid, along with SO2 being released at 130 °C and also a small amount of free radicals. We also conducted an experiment on coal from Xingcheng using X-ray photoelectron spectroscopy (XPS). The results show that the major forms of organic sulfur in the original coal sample are thiophene and sulfone. Therefore, it can be inferred that there is none or little mercaptan and thiophenol in the original coal. After low-temp oxidation, the form of organic sulfur changes. The sulfide sulfur is oxidized to the sulfoxide, and then the sulfoxide is further oxidized to a sulfone, and these steps can be easily carried out under experimental conditions. What's more, the results illustrate that oxidation promotes sulfur element enrichment on the surface of coal.
- Zhang, Lanjun,Li, Zenghua,Li, Jinhu,Zhou, Yinbo,Yang, Yongliang,Tang, Yibo,McPhee, Derek J.
-
p. 22241 - 22256
(2016/01/25)
-
- Effect of Alkali Treatment of HY Zeolite on Continuous Synthesis of Triacetonamine
-
The continuous synthesis of triacetonamine from acetone and ammonia over HY was realized. Meanwhile, alkali-treated HY with different structure and acidities were prepared and examined. The results indicated that the acid sites, especially Br?nsted acid sites, played a vital role on the selectivity of triacetonamine and the conversion of acetone. It was further confirmed by X-ray diffraction (XRD), N2 adsorption and desorption experiments, IR spectra of adsorbed pyridine, and NH3 temperature-programmed desorption. Meanwhile, the generation mechanisms of triacetonamine and impurities were speculated.
- Tian, Jun,Chen, Ligong,Zhang, Chao,Yan, Xilong,Li, Yang
-
p. 1377 - 1381
(2015/02/19)
-
- Catalyst for aldol condensation
-
In one embodiment, the invention is to a catalyst composition comprising lime and cement. Preferably, the catalyst composition comprises the lime and the cement in a weight ratio of at least 3.5:1 respectively.
- -
-
Page/Page column 11
(2015/12/25)
-
- A new peroxo-route for the synthesis of Mg-Zr mixed oxides catalysts: Application in the gas phase acetone self-condensation
-
We propose in this manuscript a new peroxo-mediated procedure for preparing magnesia-zirconia mixed oxides, with Mg/Zr molar ratio between 1 and 3, with enhanced distribution of basic sites. The mixed magnesia-zirconia oxides have been prepared from the gelled complex by Pechini-type method. The MgO-ZrO 2 materials have been characterized and used as catalysts for acetone aldol condensation. The proposed preparation method provides a high degree of molecular homogeneity and favours the formation of magnesia-stabilized zirconia phase. Acetone gas-phase self-condensation was carried out over these catalysts as model reaction requiring the presence of basic sites. The condensation yields diacetone alcohol and mesityl oxide as mean C6 products, and phorones, isophorones and mesitylene as C9 products. In comparison to Mg-Zr oxide prepared by co-precipitation, these new materials present better conversions and higher selectivity to linear dimers and trimers (as mesitylene), whereas the selectivity for isophorones is significantly lower.
- Krivtsov, Igor,Faba, Laura,Díaz, Eva,Ordó?ez, Salvador,Avdin, Viacheslav,Khainakov, Sergei,Garcia, Jose R.
-
-
- Thermal and photochemical oxidation of 2-acetylcyclopentanone with atmospheric oxygen
-
The major products of thermal (acetone, CaCl2 excess, reflux) and photochemical (acetone or CCl4, room temperature) oxidation of 2-acetylcyclopentanone with atmospheric oxygen are 2-acetyl-2- hydroxycyclopentanone, 2-acetyl-2-hydroxy
- Novikov,Shestak
-
p. 1099 - 1110
(2013/07/26)
-
- Molecular probes of the mechanism of cytochrome P450. Oxygen traps a substrate radical intermediate
-
The diagnostic substrate tetramethylcyclopropane (TMCP) has been reexamined as a substrate with three drug- and xenobiotic-metabolizing cytochrome P450 enzymes, human CYP2E1, CYP3A4 and rat CYP2B1. The major hydroxylation product in all cases was the unrearranged primary alcohol along with smaller amounts of a rearranged tertiary alcohol. Significantly, another ring-opened product, diacetone alcohol, was also observed. With CYP2E1 this product accounted for 20% of the total turnover. Diacetone alcohol also was detected as a product from TMCP with a biomimetic model catalyst, FeTMPyP, but not with a ruthenium porphyrin catalyst. Lifetimes of the intermediate radicals were determined from the ratios of rearranged and unrearranged products to be 120, 13 and 1 ps for CYP2E1, CYP3A4 and CYP2B1, respectively, corresponding to rebound rates of 0.9 × 1010 s-1, 7.2 × 1010 s -1 and 1.0 × 1012 s-1. For the model iron porphyrin, FeTMPyP, a radical lifetime of 81 ps and a rebound rate of 1.2 × 1010 s-1 were determined. These apparent radical lifetimes are consistent with earlier reports with a variety of CYP enzymes and radical clock substrates, however, the large amounts of diacetone alcohol with CYP2E1 and the iron porphyrin suggest that for these systems a considerable amount of the intermediate carbon radical is trapped by molecular oxygen. These results add to the view that cage escape of the intermediate carbon radical in [FeIV-OH -R] can compete with cage collapse to form a C-O bond. The results could be significant with regard to our understanding of iron-catalyzed C-H hydroxylation, the observation of P450-dependent peroxidation and the development of oxidative stress, especially for CYP2E1.
- Cooper, Harriet L.R.,Groves, John T.
-
experimental part
p. 111 - 118
(2012/02/14)
-
- PROCESS INCLUDING HYDROGENOLYSIS OF BIOMASS FOLLOWED BY DEHYDROGENATION AND ALDOL CONDENSATION FOR PRODUCING ALKANES
-
A method comprises providing a bio-based feedstock; contacting the bio-based feedstock with a solvent in a hydrolysis reaction to form an intermediate stream comprising carbohydrates; contacting the intermediate stream with an aqueous phase reforming catalyst to form a plurality of oxygenated intermediates, wherein a first portion of the oxygenated intermediates are recycled to form the solvent; and contacting at least a second portion of the oxygenated intermediates with a condensation catalyst comprising a base functionality to form a fuel blend.
- -
-
Page/Page column 42-43
(2011/12/02)
-
- Synthesizing and utilizing novel nano crystalline zinc chromate supported nano palladium catalyst
-
Several metal-supported catalyst compositions based on nano-crystalline zinc oxide were synthesized and characterized by X-ray powder diffraction (XRD), Carbon dioxide temperature programmed desorption (CO2 TPD), and nitrogen adsorption at ?196° C. The Pd-supported nano-ZnO mixed with different oxides such as Cr2O3, CrO3, MgO, and γ-Al2O3 showed high catalytic activity in acetone condensation in gas-phase process under hydrogen flow. This reaction involves the base-acid coupling of acetone to form mesityl oxide, followed by its hydrogenation to methyl isobutyl ketone (MIBK). The novel catalyst 1% wt. n-Pd/n-ZnCr2O4 was utilized during gas-phase reaction during production of MIBK. MIBK selectivity was 70-72% at 66-77% acetone conversion at 300-350° C. Diisobutyl ketone (DIBK) was the main by-product, with a total MIBK+DIBK selectivity up to 88%. The prepared catalysts showed stable activity and may be used repeatedly and for a longer period of time.
- -
-
Page/Page column 6-7
(2011/06/23)
-
- Oxidation of butane-1,3-, butane-1,4-, 2-methyl pentane-2,4- and 3-methyl pentane-2,4-diols by cerium(IV) in aqueous acidic medium catalyzed by rhodium(III)
-
The oxidation kinetics of butane-1,3-diol, butane-1,4-diol, 2-methyl pentane-2,4-diol and 3-methyl pentane-2,4-diol with cerium(IV) catalyzed by rhodium(III) in aqueous sulfuric acid showed a peculiar nature with respect to the variation in oxidant concentration, such that the reaction follows first-order kinetics in [Ce(IV)] at low [Ce(IV)] and then reaches a maximum with increasing [Ce(IV)], beyond which further increase in the oxidant concentration retards the rate. The rate shows direct proportionality with respect to [diol] at low concentrations, becoming independent of [diol] at higher concentrations. The rate is first order in catalyst. Retarding effects are observed when [H +] and [Ce(III)] are increased, while [Cl-] and hence ionic strength have a positive effect on the rate. Spectroscopic studies confirmed that the primary hydroxyl groups in butane-1,3-diol and butane-1,4-diol resulted in the formation of 3-hydroxy butanal and 4-hydroxy butanal, respectively. In the case of oxidation of the secondary hydroxyl groups in 2-methyl pentane-2,4-diol and 3-methyl pentane-2,4-diol, the products of oxidation were 4-hydroxy-4-methyl pentan-2-one and 4-hydroxy-3-methyl pentan-2-one, respectively.
- Tandon, Praveen K.,Khanam, Shaista Z.,Yadav, Suresh C.,Shukla, Ritesh C.
-
scheme or table
p. 739 - 746
(2012/07/01)
-
- Synthesis of methyl acetoacetate from acetone and dimethyl carbonate with alkali-promoted MgO catalysts
-
The synthesis of methyl acetoacetate (MAA) by methoxycarbonylation of acetone with dimethyl carbonate (DMC) was carried out in the presence of MgO and alkali-promoted MgO catalysts. From among Li, Na, K, and Cs, potassium was found to be the most effective promoter to improve the activity of MgO. The effect of K/MgO with variable content of K was also investigated, and the individual catalysts were characterised by the XRD, BET, SEM, CO2-TPD, and in situ CO2 IR techniques. The results showed that the addition of a small amount of K (1.97 mass %) could promote MAA formation, but a higher K loading caused a decrease in the yield of MAA, which might result from particle agglomeration and the presence of stable potassium carbonates. In situ FTIR experiments of co-adsorbed reactants indicated that the reaction probably proceeded via abstraction of Hα from acetone by base sites.
- Wu, Dudu,Chen, Zhi
-
experimental part
p. 758 - 766
(2011/11/29)
-
- Alcohol oxidation catalysed by Ru(VI) in the presence of alkaline hexacyanoferrate(III)
-
The oxidation of sodium lactate, 2-methyl-2,4-pentanediol, 2,4-butanediol, 2-butanol and 2-propanol upon treatment with alkaline hexacyanoferrate(III) using a Ru(VI) catalyst is highly effective for the oxidation of alcohols by Fe(CN)63-. The reaction mechanism proposed involves the oxidation of the alcohol by the catalyst, a process that occurs through the formation of a substrate-catalyst complex. The decomposition of this complex yields Ru(IV) and a carbocation (owing to a hydride transfer from the α-C-H bond of the alcohol to the oxoligand of ruthenium). The role of the co-oxidant, hexacyanoferrate(III), is to regenerate the catalyst. In the oxidation reactions, the rate constants for complex decomposition and catalyst regeneration have been determined and a comparative study of the structure versus reactivity has been carried out. Copyright
- Poblete, Francisco J.,Corrochano, Pablo
-
experimental part
p. 1088 - 1092
(2011/07/06)
-
- Generation and stereoselective transformations of 3-phenylcyclopropene
-
A convenient and inexpensive approach to the generation of 3-phenylcyclopropenes is described. Reaction of these compounds with a range of dienophiles and dipolarophiles led to the stereoselective formation of [4+2]- and [3+2]-cycloadducts, which were exclusively exo-3-phenyl-cis-1,2-disubstituted cyclopropanes. Efficient trapping of 1-lithio-3-phenylcyclopropene with different electrophiles is also discussed. Ab initio calculations suggest that the lowest energy conformation of 3-phenylcyclopropene has the plane of the benzene ring perpendicular to the cyclopropene π-bond but with a low rotation barrier.
- Sheshenev, Andrey E.,Baird, Mark S.,Croft, Anna K.,Bolesov, Ivan G.
-
experimental part
p. 10036 - 10046
(2010/02/27)
-
- Oxidation of diols by cetyltrimethylammonium dichromate
-
The oxidation kinetics of some diols have been investigated using cetyltrimethylammonium dichromate as the oxidant in dichloromethane in the presence of acetic acid and a cationic surfactant. A tentative mechanism has been proposed on the basis of (i) observed rate constant dependencies on the reactants, (ii) high negative entropy change and (iii) the kobs dependencies on surfactant concentration.
- Patel, Sabita,Sung, Dae Dong,Mishra
-
scheme or table
p. 1218 - 1221
(2009/03/11)
-
- Direct addition of supercritical alcohols, acetone or acetonitrile to the alkenes without catalysts
-
The reactions of the alkenes with supercritical organic compounds under non-catalytic conditions were investigated. The H and CR2OH, CH2C{double bond, long}OCH3 or CH2C{triple bond, long}N of supercritical alcohols (CHR2OH), acetone (CH3C{double bond, long}OCH3) or acetonitrile (CH3C{triple bond, long}N) added to the C{double bond, long}C bonds of alkenes form C-C bonds between the α-carbons of the supercritical organic compounds and the sp2 carbons of the alkenes.
- Kamitanaka, Takashi,Hikida, Tatsuyoshi,Hayashi, Satoshi,Kishida, Nobuhiro,Matsuda, Tomoko,Harada, Tadao
-
p. 8460 - 8463
(2008/03/13)
-
- NOVEL SUPPORTED PHOSPHAZENE CATALYSTS, NOVEL COMPOUNDS FOR THE CATALYSTS, AND USE THEREOF
-
There is provided a phosphazene-supported catalyst in which a support is bonded to a group represented by the general formula (1): (wherein n is an integer of 1 to 8 and represents the number of phosphazenium cations, and Z n- is an anion of an active hydrogen compound in a form derived by releasing n protons from an active hydrogen compound having a maximum of 8 active hydrogen atoms. a, b, c and d are each a positive integer of 3 or less. R's represent the same or different hydrocarbon groups having 1 to 10 carbon atoms and two R's located on each common nitrogen atom may be bonded to each other to form a ring structure. R 1 is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. D is a direct bond or a divalent group capable of bonding N to a support.). The phosphazene-supported catalyst according to the present invention is highly effective to proceed various organic reactions, and further has no reduction of activity even after recovery and reuse of the catalyst, thus it being economically advantageous. Further, according to the method of the invention, polymerization of cyclic monomers, substitution of substituents, carbon-carbon bond forming reactions and the like can be conducted with extremely high efficiency.
- -
-
Page/Page column 34-35
(2008/06/13)
-
- METHOD FOR THE PRODUCTION OF TETRAHYDROGERANYLACETONE
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The invention relates to a method for the production of tetrahydrogeranylacetone (tetrahydropseudoionone) by means of aldolcondensation of citral with acetone and subsequent hydrogenation. The invention also relates to the utilization of the tetrahydrogeranylacetone thus obtained for the production of phytol, isophytol, tocopherol and/or tocopherol derivatives. The invention further relates to methods for the production of tocopherols and/or tocopherol derivatives.
- -
-
Page/Page column 12; 13
(2008/06/13)
-
- Mechanistic studies on reaction of [ReH4(η2- H2)(Cyttp)]+ with ketones to give the hydrido-oxo complex [ReH2(O)(Cyttp)]+ (Cyttp = PhP(CH2CH 2CH2PCy2)2)
-
Mechanistic studies were conducted on reaction of [ReH4(η 2-H2)(Cyttp)]OTf (1(OTf); Cyttp = PhP(CH 2CH2CH2PCy2)2, OTf = O3SCF3) with ketones, both neat and in solution. Treatment of 1(OTf) with excess acetone at 60-65°C affords [ReH2(O)(Cyttp) ]OTf (2(OTf)) in high yield, nearly 1 equiv. of H2, 2 equiv. of 2-propanol, 1 equiv. of each of 4-hydroxy-4-methyl-2-pentanone (B) and 4-methylpent-3-en-2-one (C), and smaller amounts of other organic products derived by condensation or related reactions of acetone. The presence of C, apparently arising by dehydration of B, points to the formation of 1 equiv. of H2O in the reaction system. Use of acetone-d6 in conjunction with 1(OTf) gives 2(OTf) containing no deuterium, as well as 1 equiv. of each of (CD3)2CHOH/OD and (CD3) 2CDOD/OH. Reactions of 1(OTf) with cyclohexanone, including cyclohexanone-2,2,6,6-d4, under comparable conditions, give analogous results. The ketones cyclopentanone, 2-butanone, and 3-pentanone also convert 1(OTf) to 2(OTf) upon heating, as does isobutyraldehyde, but only in the presence of the stabilizer BHT. In contrast, the more robust ketones 2,4-dimethyl-3-pentanone, 2,6-dimethylcyclohexanone, and 2-adamantanone, which do not undergo condensation, failed to effect this transformation. Other organooxygen compounds, i.e., methanol, cyclohexanol, 1,2-butene oxide, cyclohexene oxide, DMSO, and Me3NO, also are ineffective. A mechanism is proposed which begins with loss of H2 by 2 to give a 16-electron [ReH4(Cyttp)]+ which, depending on the experimental conditions, binds a solvent or ligand molecule. A [ReH 4(R2CO)(Cyttp)]+ intermediate generated in this manner reacts spontaneously by elimination of R2CHOH (containing methine hydrogen even when deuteriated ketone is used), which results from transfer of two hydride ligands to coordinated ketone. Continued reaction leads to the formation of 2 and another molecule of R2CHOH (containing methine deuterium when deuteriated ketone is employed), with the added hydrogens coming from H2O, which derives from solvent/reactant ketone.
- Rende, Dean E.,Wojcicki, Andrew
-
p. 862 - 873
(2007/10/03)
-
- Aldol condensations over reconstructed Mg-Al hydrotalcites: Structure-activity relationships related to the rehydration method
-
Two different rehydration procedures in the liquid or gas phase have been applied to reconstruct mixed oxides derived from calcined hydrotalcite-like materials to be used as catalysts for aldol condensation reactions. The as-synthesized hydrotalcite, its decomposition product, as well as the reconstructed solids upon rehydration were characterized by XRD, N2 adsorption, He pycnometry, FTIR, SEM, TEM, 27Al MAS-NMR and CO 2-TPD (TPD = temperature-programmed desorption). Compared to the Mg-Al mixed oxide rehydrated in the gas phase (HT-rg), that rehydrated in the liquid phase (HT-r1) exhibits a superior catalytic performance with respect to the aldol condensation of citral with ketones to yield pseudoionones and in the self-aldolization of acetone. The textural properties of HT-r1 and HT-rg differ strongly and determine the catalytic behavior. A memory effect led to a higher degree of reconstruction of the lamellar structure when the mixed oxide was rehydrated in the gas phase rather than in the liquid phase, although liquid-phase rehydration under fast stirring produced a surface area that was 26 times greater. This contrasts to typical statements in the literature claiming a higher degree of reconstruction in the presence of large amounts of water in the medium. CO2-TPD shows that the number of OH- groups and their nature are very similar in HT-rg and HT-r1, and cannot explain the markedly different catalytic behavior. Accordingly, only a small fraction of the available basic sites in the rehydrated samples is active in liquid-phase aldol condensations. Our results support the model in which only basic sites near the edges of the hydrotalcite platelets are partaking in aldol reactions. Based on this, reconstructed materials with small crystallites (produced by exfoliation during mechanical stirring), that is, possessing a high external surface area, are beneficial in the reactions compared to larger crystals with a high degree of intraplatelet porosity.
- Abello, Sonia,Medina, Francesc,Tichit, Didier,Perez-Ramirez, Javier,Groen, Johan C.,Sueiras, Jesus E.,Salagre, Pilar,Cesteros, Yolanda
-
p. 728 - 739
(2007/10/03)
-
- Process for the hydrogenation of acetone
-
Acetone is hydrogenated by a process comprising, conducting the liquid-phase hydrogenation of acetone in at least two hydrogenation process stages, thereby preparing isopropanol product with a high selectivity and in high purity.
- -
-
Page/Page column 1-2
(2008/06/13)
-
- The role of potassium cation in the Favorskii ethynylation of acetone: Effekt of dibenzo-18-crown-6
-
Macrocyclic polyether dibenzo-18-crown-6 possessing a specific affinity for potassium cation inhibits ethynylation of acetone with acetylene in the presence of KOH according to Favorskii. The inhibition becomes stronger in the presence of the complex dibenzo-18-crown-6·KOH·MeOH as catalyst (both in excess acetone and in DMSO). The effect does not originate from deactivation of acetone, for its aldol-like condensation is accelerated in the presence of both dibenzo-18-crown-6 and its complex (the selectivity of ethynylation sharply falls down). Thus, apart from the high basicity of the medium, activation of acetylene due to complex formation with potassium cation plays an important role in the Favorskii ethynylation of ketones.
- Trofimov,Nosyreva,Mal'kina
-
p. 1254 - 1259
(2007/10/03)
-
- Heterogeneously catalyzed reactive distillation in the suspension mode
-
Process for carrying out a reactive distillation in the presence of a heterogeneous catalyst which is suspended as disperse phase in the liquid, wherein part of the catalyst-containing suspension is continuously discharged from the column and is treated in a work-up stage and at least part of the work-up catalyst is returned to the column.
- -
-
-
- Rate constants for the gas-phase reactions of OH radicals with a series of hydroxyaldehydes at 296 ± 2 K
-
Using a relative rate method with in situ generation of the hydroxyaldehydes, rate constants for the reactions of the OH radical with 2-hydroxybutanal [CH3CH2CH(OH)CHO], 3-hydroxybutanal [CH3CH(OH)CH2CHO], 2-hydroxypropanal [CH 3CH(OH)CHO], 2-hydroxy-2-methylpropanal [(CH3) 2C(OH)CHO], and 3-hydroxy-propanal [HOCH2CH 2CHO] have been measured at atmospheric pressure and 296 ± 2 K. The hydroxy-aldehydes were generated in situ from the OH radical-initiated reactions of precursor compounds (1,2- and 1,3-butanediol, 2-methyl-2,4-pentanediol, 2-methyl-3-buten-2-ol, and cis-3-hexen-1-ol) and the rate constants for the reaction of OH radicals with the hydroxyaldehydes were determined relative to those for reaction of OH radicals with the precursor compound. The rate constants obtained (in units of 10-11 cm 3 molecule-1 s-1) were CH3CH 2CH(OH)CHO, 2.37 ± 0.23; CH3CH(OH)CH 2CHO, 2.95 ± 0.24; CH3CH(OH)CHO, 1.70 ± 0.20; (CH3)2C(OH)CHO, 1.40 ± 0.25; and HOCH 2CH2CHO, 1.99 ± 0.29.
- Baker, Jillian,Arey, Janet,Atkinson, Roger
-
p. 7032 - 7037
(2007/10/03)
-
- Generation and stereocontrolled trapping of 3-phenylcyclopropene and its derivatives
-
Selective methods for the preparation of 3-phenylcyclopropene and its 1-substituted derivatives are provided. The parent cyclopropene is readily trapped in (3+2)- and (4+2)-cycloadditions that lead to exo-3-phenyl-1,2- disubstituted cyclopropanes. Ab initio calculations suggest that the lowest energy conformation has the plane of the benzene ring perpendicular to the cyclopropene π-bond but with a low rotation barrier.
- Sheshenev, Andrey E.,Baird, Mark S.,Croft, Anna K.,Bolesov, Ivan G.
-
p. 299 - 301
(2007/10/03)
-
- Access to diversely α-substituted cyclopentenones from α-chlorocyclopentenones
-
α-Chlorocyclopentenones can readily be transformed into a variety of I?±-substituted cyclopentenones via their dimethyltrimethylene acetals.
- Giannini, Audrey,Coquerel, Yoann,Greene, Andrew E.,Deprés, Jean-Pierre
-
p. 6749 - 6751
(2007/10/03)
-
- Supported choline hydroxide (ionic liquid) as heterogeneous catalyst for aldol condensation reactions
-
Choline hydroxide was used as a basic catalyst for aldol condensation reactions to produce new C-C bonds between several ketones and aldehydes. Choline supported on MgO exhibits higher TOF values than other well known basic catalysts in these reactions.
- Abello, Sonia,Medina, Francisco,Rodriguez, Xavier,Cesteros, Yolanda,Salagre, Pilar,Sueiras, Jesus E.,Tichit, Didier,Coq, Bernard
-
p. 1096 - 1097
(2007/10/03)
-
- The photodecarboxylative addition of carboxylates to phthalimides: Scope and limitations
-
Intermolecular photoinduced decarboxylative additions of a series of alkylcarboxylates to N-substituted phthalimides gave the corresponding hydroxyphthalimidines in moderate to high yields of 39-89%. The potassium salt of 1-adamantanecarboxylic acid predominately underwent simple decarboxylation when irradiated in the presence of N-methylphthalimide. In case of phthalimides carrying suitable leaving groups within the N-side chain, decarboxylation, retro-Aldol cleavage or decarbonylation preceded the intermolecular addition step.
- Oelgemoeller, Michael,Cygon, Peter,Lex, Johann,Griesbeck, Axel G.
-
p. 669 - 684
(2007/10/03)
-
- Bromine-magnesium exchange in gem-dibromocyclopropanes using Grignard reagents
-
Reaction of gem-dibromocyclopropanes with ethylmagnesium bromide at ambient temperature leads to very high yields of allenes; when cyclopropylidene-allene ring opening is suppressed, alternative carbenic products are observed, although other reactions compete. When the reactions are carried out at -60°C, a 1-bromo-1-(bromomagnesio)-cyclopropane is formed which may be trapped by a number of electrophiles.
- Baird, Mark S,Nizovtsev, Alexey V,Bolesov, Ivan G
-
p. 1581 - 1593
(2007/10/03)
-
- Acetonyltriphenylphosphonium bromide and its polymer-supported analogues as catalysts in protection and deprotection of alcohols as alkyl vinyl ethers
-
Both acetonyltriphenylphosphonium bromide (ATPB, 1) and poly-p-styryldiphenylacetonylphosphonium bromide (A) were effective catalysts in the protection of alcohols as THP, THF, and EE ethers as well as the cleavage of THP, THF, and EE ethers to the corresponding alcohols. They could be applied to 1°, 2° and 3° alcohols, phenol and acid-labile alcohols. Both ATPB and catalyst A are excellent catalysts in the present study. It needed only 1×10-2-1.25×10-2 mol equiv. of the polymer-supported catalyst A in the reactions.
- Hon, Yung-Son,Lee, Chia-Fu,Chen, Rong-Jiunn,Szu, Ping-Hui
-
p. 5991 - 6001
(2007/10/03)
-