Racemic N-sulfonyloxaziridines as highly diastereoselective enolate hydroxylating agents: enantioselective synthesis of (2S,3S)-3-amino-N-cyclopropyl-2-hydroxyhexanamide

A new, highly enantioselective synthesis of (2S,3S)-3-amino-N-cyclopropyl-2-hydroxyhexanamide, a synthetic fragment of the experimental hepatitis C drug Telaprevir, has been described. Conjugate addition of the enantiomerically pure Davies lithium amide followed by hydroxylation of the in situ generated β-amino enolate was employed for the formation of the required stereogenic centres. Importantly, very high diastereoselectivities can still be achieved in the key-step when the relatively expensive and enantiopure (camphorsulfonyl)oxaziridine hydroxylating agent is replaced by racemic trans-N-sulfonyloxaziridines. Among the tested N-sulfonyloxaziridines the iso-propyl substituted analogue proved to be the ideal choice from an economic viewpoint.     

Infrared laser-produced carbon-phase shield to oxidation of nanosized titanium monoxide

Pulsed infrared laser-irradiation of titanium monoxide leads to ablation and when carried out in gaseous benzene (1-5 Torr) to simultaneous dielectric breakdown of benzene into low molecular carbonaceous species which allow carbothermal reduction of ablated TiO_x particles and their protection by carbonaceous shell. The deposited particles are characterized by Fourier transform infrared Raman and X-ray photoelectron spectroscopy and by electron microscopy and shown to be stable towards oxidation in air. The reported process can find use in protection of gas-phase produced reactive nanoparticles by carbon phase.     

Pervaporation for separating benzene/cyclohexane mixture by P(AA-MA) copolymer membranes

P(AA-MA)copolymers composed of acrylic acid and methyl acrylate with different molecular weights and sequence structures were synthesized by combination of ATRP and selective hydrolysis.These copolymers were used as membrane materials to separate benzene/cyclohexane mixture by pervaporation.The effects of molecular weight and sequence structure of the copolymers on the pervaporation performance were investigated in detail.For the random copolymers,the permeate flux decreased rapidly with the increasing of molecular weight.The separation factor was also influenced by the molecular weight,which was changed from no selectivity to cyclohexane selectivity with increasing the molecular weight.Contrarily,the block copolymer membrane showed good benzene selectivity with separation factor of 4.3 and permeate flux of 157 g/(m~2h)to 50 wt%benzene/cyclohexane mixture.     

纳米孔碳负载Fe3O4催化剂上苯直接羟基化制苯酚

Fe3O4/CMK-3 was prepared by impregnation and used as a catalyst for the direct hydroxylation of benzene to phenol with hydro-gen peroxide. The iron species in the prepared catalyst was Fe3O4 because of the partial reduction of iron(III) to iron(II) on the surface of CMK-3. The high catalytic activity of the catalyst arises from the formation of Fe3O4 on the surface of CMK-3 and the high selectivity for phenol is attributed to the consumption of excess hydroxyl radicals by CMK-3. The effect of temperature,re...     

A simplified Quick, Easy, Cheap, Effective, Rugged and Safe approach for the determination of trihalomethanes and benzene, toluene, ethylbenzene and xylenes in soil matrices by fast gas chromatography with mass spectrometry detection

A method based on simplified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) extraction followed by large-injection volume-fast gas chromatography and mass spectrometry detection has been developed for the determination of trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane and bromoform) and BTEX (benzene, toluene, ethylbenzene and xylenes) in soil samples.The simplified version of QuEChERS used meets the requirements of the “green chemistry” and provides reliable results with high sample throughput, low solvent consumption, little labour and the use of materials commonly employed in laboratories. The GC device used is equipped with a programmable temperature vaporizer (PTV), with a liner packed with Tenax-TA^®. Using the solvent-vent mode, the PTV allows the injection of large volumes of sample, affording an improvement in the sensitivity of the method. The chromatographic conditions used here allowed the separation of the compounds in less than 5.50 min. Good linearity was obtained for all the target compounds, with highly satisfactory repeatability and reproducibility values. The limits of detection were in the 0.2 to 15 μg kg⁻¹ range. The method was validated by the analysis of two certified reference materials.     

单层分散CuOx对甲苯催化燃烧作用的研究

考察了一系列在不同温度下制备的Cu/Al2O3催化剂对苯催化燃烧的性能,并利用X-射线粉末衍射（XRD）、X-射线光电子能谱（XPS）、程序升温还原（TPR）对催化剂进行了表征．结果表明：低于单层分散的CuO具有可在低温还原的特性．在低于单层分散阈值的范围内,随着CuO负载量的增加催化剂活性加．超过单层分散阈值,催化剂...     

Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels

The diffusion behavior of fluid water in nanochannels with hydroxylation of silica gel and silanization of different modified chain lengths was simulated by the equilibrium molecular dynamics method. The diffusion coefficient of fluid water was calculated by the Einstein method and the Green–Kubo method, so as to analyze the change rule between the modification degree of nanochannels and the diffusion coefficient of fluid water. The results showed that the diffusion coefficient of fluid water increased with the length of the modified chain. The average diffusion coefficient of fluid water in the hydroxylated nanochannels was 8.01% of the bulk water diffusion coefficient, and the diffusion coefficients of fluid water in the –(CH₂)₃CH₃, –(CH₂)₇CH₃, and –(CH₂)₁₁CH₃ nanochannels were 44.10%, 49.72%, and 53.80% of the diffusion coefficients of bulk water, respectively. In the above four wall characteristic models, the diffusion coefficients in the z direction were smaller than those in the other directions. However, with an increase in the silylation degree, the increased self-diffusion coefficient due to the surface effect could basically offset the decreased self-diffusion coefficient owing to the scale effect. In the four nanochannels, when the local diffusion coefficient of fluid water was in the range of 8 Å close to the wall, Dz was greater than Dxy, and beyond the range of 8 Å of the wall, the Dz was smaller than Dxy.     

First total synthesis of (−)-8-epi-9-deoxygoniopypyrone

The structure and absolute configuration of natural 8-epi-9-deoxygoniopypyrone have been confirmed by an efficient and highly diastereoselective synthesis in 15 steps from (S)-mandelic acid with an overall yield of 43%.     

Gallery-templated Synthesis of Titanium／Silicon -containing Mesoporous Montmorillonite-based Catalytic Materials

A mesoporous titanium/silicon -containing montmorillonite-based catalytic materials has been synthesized by novel gallery-templated techniques. XRD, SEM, framework IR, and N2 adsorption-desorption isotherms provided evidence of the formation of Si/Ti pillars. The synthetic materials show potential catalytic application for hydroxylation of phenol with peroxide.     

Azeotropic behaviour of (benzene + cyclohexane + chlorobenzene) ternary mixture using chlorobenzene as entrainer at 101.3 kPa

In this paper, the azeotropic behaviour of the (benzene + cyclohexane + chlorobenzene) ternary mixture was experimentally investigated with the aim of enhancing the knowledge for the feasible use of chlorobenzene as an entrainer for the azeotropic distillation of the binary azeotrope. Such a study has not been reported in the literature to the best of the authors’ knowledge. (Vapour + liquid) equilibria data for (benzene + cyclohexane + chlorobenzene) at 101.3 kPa were obtained with a Othmer-type ebulliometer. Data were tested and considered thermodynamically consistent. The experimental results showed that this ternary mixture is completely miscible and exhibits an unique binary homogeneous azeotrope, an unstable node at the conditions studied, and the propitious topological characteristics (residual curve map and relative volatility) to be separated. Satisfactory results were obtained for the correlation of equilibrium compositions with the UNIQUAC activity coefficients model and also for prediction with the UNIFAC method. In both cases, low root mean square deviations of the vapour mole fraction and temperature were calculated. The capability of chlorobenzene as a modified distillation agent at atmospheric condition is discussed in terms of the thermodynamic topological analysis. A conceptual distillation scheme with reversed volatility is proposed to separate the azeotropic mixture. In order to reduce the operational cost requirements of the sequence of columns proposed, the range for optimal reflux and the ratio for feed flow conditions were studied.