Hydrogenation of cyclohexene and benzene over an amorphous pd-zr alloy

Amorphous Pd-Zr alloys, produced by a rapid solidification technique, were studied to determine their catalytic activity for the hydrogenation of cyclohexene and benzene. The activity of the amorphous alloy without pretreatment by air was lower than that of the corresponding crystalline alloy, but it was gradually increased with the pretreatment. The surface area and the hydrogen adsorption activity of the alloys were simultaneously increased with the pretreatment. It is found from X-ray diffraction pattern and SEM observation that palladium, which is an active species for hydrogenation in the amorphous alloys, is highly dispersed on the granulated ZrO₂ surface by the pretreatment.     

3-hydroxybenzene 1,2,4-trisphosphate, a novel second messenger mimic and unusual substrate for type-I myo-inositol 1,4,5-trisphosphate 5-phosphatase: Synthesis and physicochemistry

3-Hydroxybenzene 1,2,4-trisphosphate 4 is a new myo-inositol 1,4,5-trisphosphate analogue based on the core structure of benzene 1,2,4-trisphosphate 2 with an additional hydroxyl group at position-3, and is the first noninositol based compound to be a substrate for inositol 1,4,5-trisphosphate 5-phosphatase. In physicochemical studies on 2, when three equivalents of protons were added, the (31)P NMR spectrum displayed monophasic behaviour in which phosphate-1 and phosphate-2 behaved independently in most of the studied pH range. For compound 4, phosphate-2 and phosphate-4 interacted with the 3-OH group, which does not titrate at physiological pH, displaying complex biphasic behaviour which demonstrated co-operativity between these groups. Phosphate-1 and phosphate-2 strongly interacted with each other and phosphate-4 experienced repulsion because of the interaction of the 3-OH group. Benzene 1,2,4-trisphosphate 2 is resistant to inositol 1,4,5-trisphosphate type I 5-phosphatase catalysed dephosphorylation. However, surprisingly, 3-hydroxybenzene 1,2,4-trisphosphate 4 was dephosphorylated by this 5-phosphatase to give the symmetrical 2,3-dihydroxybenzene 1,4-bisphosphate 16. The extra hydroxyl group is shown to form a hydrogen bond with the vicinal phosphate groups at -15 degrees C, and (1)H NMR titration of the ring and hydroxyl protons in 4 shows the OH proton to be strongly stabilized as soon as the phosphate groups are deprotonated. The effect of the phenolic 3-OH group in compound 4 confirms a critical role for the 6-OH group of the natural messenger in the dephosphorylation mechanism that persists even in radically modified analogues.     

Surfactant‐Stabilized Aqueous Iridium(0) Colloidal Suspension: An Efficient Reusable Catalyst for Hydrogenation of Arenes in Biphasic Media

Aqueous suspensions of iridium nanoparticles produced by the chemical reduction of IrCl₃ assisted by sonication, in the presence of N,N‐dimethyl‐N‐cetyl‐N‐(2‐hydroxyethyl)ammonium chloride salt as surfactant, have shown an efficient activity for the catalytic hydrogenation of various aromatic derivatives in biphasic media under mild conditions. These nanocatalysts can be reused for further runs with a total conservation of activity and provided significant catalytic lifetime for anisole hydrogenation in pure water with 3000 total turn‐over (TTO).     

Rhodium‐Catalyzed Hydrogenation of Alkenes by Rhodium/Tris(fluoroalkoxy)phosphane Complexes in Fluorous Biphasic System

The reaction of [Ir(μ‐Cl)(COD)]₂ with various fluorous derivatives of triphenylphosphane containing a para‐, meta‐, or ortho‐(1H,1H‐perfluoroalkoxy)‐substituted fluorous phosphane P(C₆H₄‐ORf)₃ (Rf=CH₂C₇F₁₅, CH₂CH₂CH₂C₈F₁₇) and CO (1 atm) gives the corresponding trans‐[Ir(μ‐Cl)(CO){P(C₆H₄ORf)₃}₂]. The IR ν_CO values of these complexes give some information on the donor/acceptor properties of the phosphanes. These fluorous derivatives of triphenylphosphane, as well as a phosphane bearing two (1H,1H‐perfluoroalkyloxy) chains at the 3,5‐positions, were used in association with [Rh(μ‐Cl)(COD)]₂ or [Rh(COD)₂]PF₆ in the reduction of methyl cinnamate, 2‐cyclohexen‐1‐one, cinnamaldehyde, and methyl α‐acetamidocinnamate in a two‐phase system D‐100/ethanol under 1 bar hydrogen at room temperature. Some differences in catalytic activity were observed in the reduction of methyl cinnamate, the most active catalyst being the rhodium complex containing the phosphane with the p‐fluorous ponytail. Recycling of the fluorous catalyst was possible, particularly using the p‐substituted phosphane, where no significant loss of catalyst or activity was observed, and generally with very low leaching of rhodium or phosphane in the organic phase.     

Synthesis of Bipyridine‐Stabilized Rhodium Nanoparticles in Non‐Aqueous Ionic Liquids: A New Efficient Approach for Arene Hydrogenation with Nanocatalysts

A new approach to stabilize metal nanoparticles with polynitrogen ligands in ionic liquids (ILs) is described. Zerovalent metal nanospecies in the size range of 2.0 nm were easily prepared in various ionic liquids by chemical reduction of a rhodium salt with an excess amount of sodium borohydride (NaBH₄) and efficiently stabilized by 2,2′‐bipyridine. The influence of the bipyridine ratio in various ILs according to the nature of the cation‐anion association was investigated. These nanocatalysts were evaluated in the hydrogenation of aromatic compounds in ILs under various catalytic conditions (P=1–40 bar, T=20–80 °C).     

Catalytic performance of chiral rhodium complex with water-soluble sulfonated (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl for enantioseletive hydrogenation in ionic liquid biphasic system

Asymmetric hydrogenation of dimethyl itaconate by the chiral rhodium complex ligated with water-soluble sulfonated (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (labeled as (R)-BINAPS) was performed in ionic liquid-isopropanol biphasic catalytic system. A moderate enantiomeric excess (ee) of 64% and initial turnover frequency (TOF_max) as high as 1234 h⁻¹ could be obtained at 303 K and 2.0 MPa when the molar ration of substrate to rhodium was set at 1000. Application of imidazolium ionic liquid [bmim]BF₄ (bmim = 1-butyl-3-methyl imidazolium cation) made it possible to reuse the catalyst several times, showing rather good stability in the catalyst performance. According to the ICP-OES analyses, the total extraction of rhodium species by the reactants from the ionic liquid phase was about 3.24 wt% after the catalyst for four runs, which was about three times lower than that of total loss of phosphorous species. The slight decreases in the ee value and TOF_max during the catalyst reuse could be recovered essentially to the pristine levels by replenishing certain amount of the fresh ligand into the used catalyst.     

Kinase in Motion: Insights into the Dynamic Nature of p38α by High‐Pressure NMR Spectroscopic Studies

Protein kinases are highly dynamic and complex molecules. Here we present high‐pressure and relaxation studies of the activated p38α mitogen‐activated protein kinase (MAPK). p38α plays a central role in inflammatory diseases such as rheumatoid arthritis and is therefore a highly attractive pharmaceutical target. The combination of high pressure and NMR spectroscopy allowed for a detailed per‐residue based assessment of the structural plasticity of p38α and the accessibility of low‐lying excited‐energy conformations throughout the kinase structure. Such information is uniquely accessible through the combination of liquid‐state NMR and high pressure and is of considerable value for the drug discovery process. The interactions of p38α and DFG‐in and DFG‐out ligands were studied under the application of high pressure, and we demonstrate how we can alter kinase dynamics by pressure in a similar way to what has previously only been observed by ligand binding. Pressure is shown to be a mild and efficient tool for manipulation of intermediate‐timescale dynamics.     

DYNAMICS OF IMINE AND ACETOPHENONE DERIVATIVES IN SOLUTION STUDIED BY ONE-DIMENSIONAL DIFFUSION-ORDERED NMR SPECTROSCOPY (DOSY)

This paper describes the usefulness of one-dimensional diffusion-ordered NMR spectroscopy (1D-DOSY) in investigating dynamics and interactions of molecules in solution as well as in analyzing the structure of molecules. We synthesized the three imines, N-benzylidene-4-methylbenzene-Sulfonamide (1 Kondo, K., Kazuta, K., Saitoh, A. and Murakami, Y. 2003. Heterocycles, 59: 97–100.  [Google Scholar]), N-(4-chloro-benzylidene)4-methyl-benzene-sulfonamide (2 Horibe, H., Kazuta, K., Kotoku, M., Kondo, K., Okuno, H., Murakami, Y. and Aoyama, T. 2003. Synlett, : 2047–2051. [Web of Science ®] , [Google Scholar]), and N- (4-methoxybenzylidene)-4-methyl-benzene sulfonamide (3 Horibe, H., Fukuda, Y., Kondo, K., Okuno, H., Murakami, Y. and Aoyama, T. 2004. Tetrahedron, 60: 10701–10709. [Crossref], [Web of Science ®] , [Google Scholar]), and acetophenone (4 Sakamoto, Y., Kondo, K., Tokunaga, M., Kazuta, K., Fujita, H., Murakami, Y. and Aoyama, T. 2004. Heterocycles, 63: 1345–1357. [Crossref], [Web of Science ®] , [Google Scholar]) and its three derivatives, 4-chloroacetophenone (5 Sakamoto, Y., Kondo, K., Onozato, M. and Aoyama, T. 2006. Polycycl. Aromat. Comp., 26: 59–68. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]), 4-nitro-acetophenone (6 Kondo, K., Kazuta, K., Fujita, H., Sakamoto, Y. and Murakami, Y. 2002. Tetrahedron, 58: 5209–5214. [Crossref], [Web of Science ®] , [Google Scholar]), and 4-methoxyaceto -phenone (7 Gostam, T., Morean, C., Jutean, A., Guichard, E. and Delsuc, M. A. 2004. Magn. Reson. Chem., 42: 496–499.  [Google Scholar]). 1D-DOSY was applied to a mixture of compounds (1 Kondo, K., Kazuta, K., Saitoh, A. and Murakami, Y. 2003. Heterocycles, 59: 97–100.  [Google Scholar]), (2 Horibe, H., Kazuta, K., Kotoku, M., Kondo, K., Okuno, H., Murakami, Y. and Aoyama, T. 2003. Synlett, : 2047–2051. [Web of Science ®] , [Google Scholar]), and (3 Horibe, H., Fukuda, Y., Kondo, K., Okuno, H., Murakami, Y. and Aoyama, T. 2004. Tetrahedron, 60: 10701–10709. [Crossref], [Web of Science ®] , [Google Scholar]) and to a mixture of compounds (4 Sakamoto, Y., Kondo, K., Tokunaga, M., Kazuta, K., Fujita, H., Murakami, Y. and Aoyama, T. 2004. Heterocycles, 63: 1345–1357. [Crossref], [Web of Science ®] , [Google Scholar]), (5 Sakamoto, Y., Kondo, K., Onozato, M. and Aoyama, T. 2006. Polycycl. Aromat. Comp., 26: 59–68. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]), (6 Kondo, K., Kazuta, K., Fujita, H., Sakamoto, Y. and Murakami, Y. 2002. Tetrahedron, 58: 5209–5214. [Crossref], [Web of Science ®] , [Google Scholar]), and (7 Gostam, T., Morean, C., Jutean, A., Guichard, E. and Delsuc, M. A. 2004. Magn. Reson. Chem., 42: 496–499.  [Google Scholar]). Although ¹ H NMR chemical shifts of the molecules in the mixtures resembled one another in the surrounding, we could distinguish signals of the individual molecules in each mixture on the basis of the NMR data and the values of the diffusion coefficient. Also, we could found the correlation of the measured diffusion coefficients and the calculated molecular volumes.     

焦化粗苯催化加氢精制纯苯的研究与开发

焦化粗苯低温(<390℃)、低压(<3.5MPa)加氢精制过程与溶剂萃取技术相结合,可获得高纯度的苯、甲苯和二甲苯,芳烃收率比酸洗法提高8%～10%,并解决了环境污染问题。立足国内技术建设粗苯加氢精制工厂是可行的。     

液相法苯选择加氢制环己烯反应条件的探讨

采用化学还原法制备负载型钌催化剂,进行了苯选择加氢制环己烯。研究了反应温度、氢气压力、搅拌速率、反应时间对苯转化率、环己烯选择性及收率的影响。结果表明:在最佳反应条件下,反应温度为140℃、氢气压力为6.0MPa、搅拌速率为900r/min、反应时间为20min时,苯转化率为76.27%,环己烯选择性为68.33%,环己烯收率为52.12%。     

Propensity for cis‐Proline Formation in Unfolded Proteins

In unfolded proteins, peptide bonds involving Pro residues exist in equilibrium between the minor cis and major trans conformations. Folded proteins predominantly contain trans‐Pro bonds, and slow cis–trans Pro isomerization in the unfolded state is often found to be a rate‐limiting step in protein folding. Moreover, kinases and phosphatases that act upon Ser/Thr?Pro motifs exhibit preferential recognition of either the cis‐ or trans‐Pro conformer. Here, NMR spectra obtained at both atmospheric and high pressures indicate that the population of cis‐Pro falls well below previous estimates, an effect attributed to the use of short peptides with charged termini in most prior model studies. For the intrinsically disordered protein α‐synuclein, cis‐Pro populations at all of its five X?Pro bonds are less than 5 %, with only modest ionic strength dependence and no detectable effect of the previously demonstrated interaction between the N‐ and C‐terminal halves of the protein. Comparison to small peptides with the same amino‐acid sequence indicates that peptides, particularly those with unblocked, oppositely charged amino and carboxyl end groups, strongly overestimate the amount of cis‐Pro.