Novel Chiral Aminophosphine Ligand:Synthesis and Application in Saymmetric Catalytic Hydrogenation Reaction

A new chiral aminophosphine ligand 6,6′-dimethoxy-2,2′-bis(diphenylphosphinoamino)biphenyl(DMBDPPABP) was prepared and its rhodium complex was found to be an effective catalyst for the asymmetric hydrogenation of amidoacrylic acid and its dervatives.The effects of solvent and reaction temperature on enantioselectivity were also studied.     

A New Glycoside and a Novel‐Type Diterpene from Hemerocallis fulva (L.) L.

The CHCl₃ extract of dried roots of Hemerocallis fulva (L.) L. afforded a novel diterpene named hemerocallal A ( 1 ), which is the second reported naturally occurring diterpene with a trans‐bicyclo[5.1.0]octane system. The BuOH extract afforded a new glycoside named hemerocalloside ( 2 ). Their structures were established on the basis of spectroscopic and chemical studies.     

CURING KINETICS AND PROPERTIES OF ACRYLIC RESIN CURED WITH AZIRIDINE CROSSLINKER

A kind of aziridine crosslinkers was synthesized and used to crosslink acrylate copolymers. The crosslinkingproperties and curing kinetics of the resin were studied. It was found that with the increase of the content of crosslinker in theemulsion, the mechanical properties and solvent resistance of the resin will be apparently improved, but its glass transitiontemperature (T_g) is very low. The lowest amount of crosslinker used in the acrylic resin emulsion is 0.25%. Curing kineticsstudied by DSC show that this curing reaction occurs readily because the apparent activation energy of the reaction is low(65.1 kJ/mol). These results demonstrate that the aziridine crosslinker is indeed a low temperature crosslinking agent and canbe used at room temperature.     

量子点PbS修饰纳米结构TiO2复合膜的光电化学研究

用光电流作用谱、光电流-电势图等光电化学方法研究了ITO(铟锡氧化物导电玻璃)/TiO₂ /Q-PbS(量子点PbS)膜电极的光电转换性质。结果表明，由于量子尺寸的效应，在膜电极制备中，随着ITO/TiO₂电极在饱和Pb(CH₃COO)₂溶液中浸泡时间的不同，所制备的Q-PbS颗粒大小不同，禁带宽度随着浸泡时间的增大而减小，浸泡时间为40 s、在80 ℃烘干下制备的Q-PbS的禁带宽度为1.68 eV，其价带位置为-5.072 eV。Q-PbS修饰ITO/TiO₂电极可使光电流发生明显的红移，从而提高宽禁带半导体的光电转换效率。     

Reduction of 4-nitrophenol catalyzed by nitroreductase

The reduction of 4-nitrophenol catalyzed by nitroreductase in the presence of NADH was investigated in this paper.4-Amino- phenol and 4-bydroxylamino-phenol were found in the reductive products.The relationship between reaction time and the reductive ratio were studied.The similar reducing ratios of 4-nitrophenol were obtained under aerobic and anaerobic conditions.The results indicated that an oxygen-insensitive reaction was proceeded in the reduction of 4-nitrophenol and nitroreductase was an oxygen- insensitive enzyme.The reductive products of 4-nitrophenol were determined by HPLC and MS.     

Influence of the preparation procedure on the properties of polyaniline based magnetic composites

A versatile process for the preparation of composite films consisting of magnetite (Fe₃O₄) nanoparticles embedded in a polyaniline (PANI) matrix is reported. Spectroscopic properties of polyaniline matrix (PANI-EB), polyaniline protonated with camphor sulfonic acid (PANI-CSA_0.5) PANI-ES and PANI/Fe₃O₄-CSA_0.5 composites were studied, both in the state of the solutions of m-cresol and in thin films processed from the same solvents. The results of these studies indicate that m-cresol can be used for PANI/Fe₃O₄ composite preparation. Such films show both reasonably high electrical conductivity and magnetic permeability. A controlled application of a magnetic field during the casting process resulted in the formation of the materials with an unusual combination of magnetic and transport properties. The obtained films show the behavior that can be explained by the presence of both ferromagnetic and paramagnetic phases. The superparamagnetic contribution, if any, is very small. Application of the external magnetic field during fabrication of the composites stimulates creation of the aggregates of magnetic particles which, although keeps conductivity at a relatively high level, leads to a small decrease of the conductivity value.     

The Baylis-Hillman condensation of alpha,beta-conjugate cycloketones with aldehydes using diethylaluminum iodide alone as the promoter

The Baylis-Hillman condensation of three types of alpha,beta-conjugate cycloketones with aldehydes was successfully performed by using diethylaluminum iodide as the Lewis acid promoter alone without the direct use of a Lewis base. The reaction proceeded to completion at 0 degree C in CH2Cl2 within 24 h to give modest to good yields (53-72%).     

Detailed Structural Characterizations of SBA‐15 and MCM‐41 Mesoporous Silicas on a High‐Resolution Transmission Electron Microscope

Using high‐resolution transmission electronic micrograph (HR‐TEM) observation, one can clearly see the pore geometry of the MCM‐41 and SBA‐15 mesoporous silicas to determine that their pore shapes are hexagonal and round, respectively. With the perpendicular orientations of the nanochannels to the electron beam, parallel line images of the (100) and (110) repeating spacings were observed. In the SBA‐15 mesoporous silicas, there are byproducts of the granular silica and disordered mesostructures, attributed to the weak hydrogen interactions between Pluronic 123 blockcopolymer and the silica species. There are also many different and significant +π disclination defects in SBA‐15 and MCM‐41 surfactant‐silica composites. The SBA‐15 with a thicker silica wall is more stable under irradiation by high‐energy electron beams compared to MCM‐41, which has thinner wall thickness. Some carbon nanostructure impurities were found in some carbon films on the metal grids.     

Synthesis of imidazoles as novel emivirine and S‐DABO analogues

5‐Alkyl‐4‐benzyl‐1,3‐dihydroimidazol‐2‐ones ( 3a‐d ) and 5‐alkyl‐4‐benzyl‐1,3‐dihydroimidazole‐2‐thiones (7a‐d) were prepared via Dakin West reaction on DL‐phenylalanine with the appropriate aliphatic acid anhydrides followed by hydrolysis and reaction with potassium cyanate or potassium thiocyanate. Compounds 3a‐d were alkylated with ethoxymethyl chloride to give the alkylated imidazoles 5a‐d which were considered analogues of Emivirine with deletion of carbonyl group at the 4‐position. Alkylation of 7a‐d afforded the corresponding S‐alkylated derivatives 8a‐p which in a similar way were considered analogues of S‐DABO. However all the imidazole derivatives were devoid of activity against HIV.