Regioselective synthesis of polysubstituted pyrazoles and isoxazoles

A regioselective synthesis has been developed for the preparation of unsymmetrical 1,3,5-triaryl-4-alkylpyrazolines and -pyrazoles by treatment of alpha-benzotriazolyl-alpha,beta-unsaturated ketones with monosubstituted hydrazines followed by alkylation at the 4-position of the pyrazoline ring. Reaction of alpha-benzotriazolyl-alpha,beta-unsaturated ketones with hydroxylamine gives 3,5-disubstituted isoxazoles regioselectively.     

Analysis of combinatorial chemistry samples by micellar electrokinetic chromatography

A micellar electrokinetic chromatography (MEKC) method has been developed that can evaluate the purity of samples generated in combinatorial chemistry libraries. This method uses an open tube capillary (27 cm x 50 microm) along with a run buffer composed of sodium dodecyl sulfate (SDS), hydroxypropyl-beta-cyclodextrin, and sodium tetraborate coupled with UV detection. Neutral compounds and compounds that were insoluble in aqueous buffers could be analyzed under these conditions in approximately 3 min. The concentration of SDS and the concentration of hydroxypropyl-beta-cyclodextrin effected the separation. The affect on selectivity resulting from the addition of an organic modifier to the run buffer was examined. The low background absorbency of the run buffer made for easy detection of compounds that absorbed at low UV wavelengths. The quick analysis time made this suitable for analysis of combinatorial chemistry samples.     

Analysis of acyclovir by high performance capillary electrophoresis with on-column amperometric detection

The separation of acyclovir (ACV) by high performance capillary electrophoresis (HPCE) with on-column amperometric detection using alpha-amino-5-mercapto-3,4-dithiazole (AMD) as internal standard is described. The calibration line was linear in the range of 0.5-20 mg/L of ACV. The detection limit was 0.15 mg/L of ACV. Its recovery ranged from 98 to 101% with relative standard deviations (RSDs) from 1.9 to 3.2% (n = 5). This method was successfully used for determining ACV in some pharmaceuticals and human urine. Comparable results with HPCE with ultraviolet (UV) detection and amperometric detection were obtained.     

Effects of matrix-assisted laser desorption/ionization experimental conditions on quantitative compositional analysis of ethylene oxide/propylene oxide copolymers

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has the potential to become a valuable tool for the compositional analysis of copolymers. For a copolymer composed of structurally very similar building blocks with minor chain length changes, one would expect the relative peak intensities observed in the MALDI mass spectra to reflect its composition, at least within a narrow mass range. However, we show that variations in experimental conditions in MALDI can have a significant effect on the mass spectral appearance of a copolymer. The effects of concentration, laser power, type of matrices and solvents on mass spectra of an ethylene oxide/propylene oxide copolymer are illustrated. These somewhat surprising results show that great care needs to be exercised when interpreting copolymer spectra for compositional analysis, even for copolymers with structurally similar monomers. This work also points out that further studies are needed to better understand and optimize spectral acquisition conditions for reliable copolymer compositional analysis by MALDI.     

LIGHT-SCATTERING STUDY OF POLYELECTROLYTE HOLLOW CAPSULES

Silver halide (AgX) microcrystal was used as template to synthesize hollow polyelectrolyte capsules. These hollow capsules were characterized by laser light scattering (LLS) used to measure the size of the capsules in solution. The ratio of hydrodynamic radius (Rh) from dynamic LLS to the radius of gyration (Rg) from static LLS is almost unity, revealing that the entities are hollow in solution. The results suggest that the LLS method can be regarded as a good complement to the confocal laser scanning microscopy (CLSM) method for the characterization of small hollow capsules, and it possesses the advantage of not needing fluorescence labeling.     

Zn∶Er∶LiNbO_3单晶的坩埚下降法生长及光谱特性

报道了Zn∶Er∶LiNbO3单晶的坩埚下降法生长工艺。通过控制晶体生长固液界面的温度梯度(30~35℃.cm-1)、晶体的生长速度(0.8~1.5 mm.h-1)、密闭Pt坩埚等条件生长了宏观无缺陷的Zn2+(3%)和Er3+(0.6%)共掺的LiNbO3单晶。用X射线衍射(XRD)和差热分析(DTA)表征了获得的晶体,并测量了晶体不同部位的吸收光谱和荧光谱。从吸收光谱以及由XRD数据计算所得的晶胞参数推断,沿生长方向Er3+在晶体中的浓度分布逐步减少。光谱数据表明,晶体底部样品的吸收强度和荧光强度要比顶部大,而对应于Er3+上能级4S3/2和2H11/2跃迁至基态4I15/2的绿光发射,晶体底部却比顶部表现出更高的上转换效率。从晶体的内部结构、缺陷情况以及Er3+的分凝现象解释了产生上述现象的内在机制。     

Chiral separation of anticholinergic drug enantiomers in nonaqueous capillary electrophoresis

Nonaqueous capillary electrophoretic (NACE) method for the separation of nine structurally similar chiral anticholinergic drugs was developed. The eight drug enantiomers were separated on baseline within 18 min using 20mM phosphoric acid and 10 mM NaOH, containing 10 mM heptakis(2,3-dimethyl-6-sulfato)-4beta-cyclodextrin (HDMS-beta-CD) in methanol. The results were compared with those obtained in the high performance liquid chromatography system.     

Bridged bis-pyridinylimino dinickel(II) complexes: Syntheses, characterization, ethylene oligomerization and polymerization

A series of bridged bis(pyridinylimino) ligands were efficiently synthesized through the condensation reaction of 4,4′-methylene-bis(2,6-disubstituted aniline) with 2-pyridinecarboxaldehyde or 2-benzoylpyridine. They reacted with (DME)NiBr₂ to form dinuclear Ni(II) complexes. All resultant compounds were characterized by elemental analysis, IR spectra as well as the single-crystal X-ray diffraction to confirm the structures of ligands and complexes. Activated with methylaluminoxane (MAO), these nickel complexes showed considerably good activities for ethylene oligomerization and polymerization. Their catalytic activities and the properties of PEs obtained were depended on the arched environment of ligand and reaction conditions.     

ADSORPTION OF 2,4-DICHLOROBENZOXYACETIC ACID ONTO HYPERCROSSLINKED RESIN MODIFIED BY PHENOLIC HYDROXYL GROUP (AM-1)

INTRODUCTIONAdsorption has been considered to be the best available technology for removing organics from water in the USSafe Drinking Water Act[1]. Due to many drawbacks of activated carbon[2-7], the most widely used adsorbent,hypercrosslinked polymeric adsorbents developed by Tsyurupa and Davankov[8] have been increasingly viewedas an alternative to activated carbon for selective removal of specific organic substances from contaminatedwater[9-12], and series of researches have been do…