Gold Supported on Hydroxyapatite as a Versatile Multifunctional Catalyst for the Direct Tandem Synthesis of Imines and Oximes

Two birds with one auric stone : The title system acts as a highly efficient heterogeneous catalyst for the one‐pot tandem synthesis of imines or oximes from alcohols and the corresponding amines under mild conditions (see scheme; HAP= hydroxyapatite).

     

Electrochemical Studies on the Interaction of Heparin with Phenosafranine and Its Analytical Application

The interaction of phenosafranine (PSF) with a glycosaminoglycan of heparin (Hep) in aqueous solution was characterized by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in this paper and further used for Hep detection. In pH 1.5 Britton‐Robinson (B‐R) buffer solution PSF had a well‐defined voltammetric reductive peak at ?0.256 V (vs SCE), and the electrochemical response was faded by the addition of Hep. Cyclic voltammetric experiments indicated that the electrochemical behaviors of free PSF didn't change no matter whether Hep was presented in PSF solution or not. Based on the decrease of the peak current, a second order derivative linear sweep voltammetry was used to establish a sensitive electroanalytical method for Hep. The peak current was proportional to the concentration of Hep in the range of 0.7～20.0 mg L^?1, demonstrating that this method was suitable for routine Hep detection. Under optimal conditions, the linear regression equation for the Hep determination was ΔIp”(nA) = 46.30 C (mg L^?1) + 343.31 (n = 11, γ = 0.991) with a detection limit of 0.08 mg L^?1 (3σ). The established method was further successfully applied to heparin sodium injection samples determination. The interaction mechanism was discussed based on the electrostatic attraction of the negatively charged Hep with the positively charged PSF, and the stoichiometry of Hep‐PSF was calculated by the voltammetric method.     

关于GL(3,2)的两个反例

指出GL(3,2)的两个不共轭的{2,3}-Hall子群都和S_4同构.由此,进一步给出两个不同构的S_4-模提供相同2-Brauer特征标的例子.     

求解单变量无约束优化问题的一类新割线法

本文基于分式逼近提出了一类求解单变量无约束优化问题的新割线法,给出并证明了该方法的收敛阶是(√2+1).并进一步对新方法的性能进行了分析,给出了新方法、经典的牛顿法和其他修正的割线类方法解单变量无约束优化问题的数值实验.理论和数值结果均表明新的割线法是有效的.     

Displacement of Cu(II) by Ag(I) in solvated metal sulfides. A DFT and AIM computational study

The substitution of Cu2+ by Ag+ in hydrated CuIIS and (CuII)3S3 was modeled computationally by density functional theory quantum theory of atoms in molecules, and solvent field methods. The coordination, first-shell and partly second-shell molecular structures, and thermochemical data for solvated Cu2+, Ag+, CuIIS, (CuII)3S3, AgCu2S3 and their reactions were obtained. The thermochemical data showed that displacement of Cu2+ and Cu+ from CuIIS and (CuII)3S3 by Ag+, while unfavorable in the gas phase, is facilitated in an aqueous environment. Several covalently bonded species were examined as intermediates in the substitution reactions.     

Determination of vertilmicin sulfate and its related substances by HPLC-ELSD and HPLC-MS2

A new and simple high-performance liquid chromatography (HPLC)-evaporative light scattering detection (ELSD) method for the determination of vertilmicin sulfate and its related substances is developed. The column is an Agilent SB-C(18) (250 x 4.6 mm, 5 microm). The mobile phase is 0.05 mol/L trifluoroacetic acid-methanol (85:15). Good separation of vertilmicin from the main related substances is achieved. The standard curve is rectilinear in the range of 270-1350 microg/mL (r = 0.9998). The average recovery is 99.8%. The limit of detection is 10 microg/mL. The HPLC-mass spectrometry-mass spectrometry (MS(2)) method is used to characterize the structures of vertilmicin sulfate and its related substances. In positive mode, vertilmicin sulfate and its related substances are elucidated by use of electrospray ion trap MS in the multi-stage MS full scan mode. The possible structure of an unknown impurity in vertilmicin is deduced based on the HPLC-MS(2) data.     

Diversity synthesis using the complimentary reactivity of rhodium(II)- and palladium(II)-catalyzed reactions

Rhodium(II)-catalyzed reactions of aryldiazoacetates can be conducted in the presence of iodide, triflate, organoboron, and organostannane functionality, resulting in the formation of a variety of cyclopropanes or C-H insertion products with high stereoselectivity. The combination of the rhodium(II)-catalyzed reaction with a subsequent palladium(II)-catalyzed Suzuki coupling offers a novel strategy for diversity synthesis.     

Photodissociation and photoisomerization of alpha-fluorotoluene and 4-fluorotoluene in a molecular beam

The photodissociation of jet-cooled alpha-fluorotoluene and 4-fluorotoluene at 193 and 248 nm was studied using vacuum ultraviolet (vuv) photoionization/multimass ion imaging techniques as well as electron impact ionization/photofragment translational spectroscopy. Four dissociation channels were observed for alpha-fluorotoluene at both 193 and 248 nm, including two major channels C6H5CH2F-->C6H5CH2 (or C7H7)+F and C6H5CH2F-->C6H5CH (or C7H6)+HF and two minor channels C6H5CH2F-->C6H5CHF+H and C6H5CH2F-->C6H5+CH2F. The vuv wavelength dependence of the C7H7 fragment photoionization spectra indicates that at least part of the F atom elimination channel results from the isomerization of alpha-fluorotoluene to a seven-membered ring prior to dissociation. Dissociation channels of 4-fluorotoluene at 193 nm include two major channels C6H4FCH3-->C6H4FCH2+H and C6H4FCH3-->C6H4F+CH3 and two minor channels C6H4FCH3-->C6H5CH2 (or C7H7)+F and C6H4FCH3-->C6H5CH (or C7H6)+HF. The dissociation rates for alpha-fluorotoluene at 193 and 248 nm are 3.3 x 10(7) and 5.6 x 10(5) s(-1), respectively. The dissociation rate for 4-fluorotoluene at 193 nm is 1.0 x 10(6) s(-1). An ab initio calculation demonstrates that the barrier height for isomerization from alpha-fluorotoluene to a seven-membered ring isomer is much lower than that from 4-fluorotoluene to a seven-membered ring isomer. The experimental observed differences of dissociation rates and relative branching ratios between alpha-fluorotoluene and 4-fluorotoluene may be explained by the differences in the six-membered ring to seven-membered ring isomerization barrier heights, F atom elimination threshold, and HF elimination threshold between alpha-fluorotoluene and 4-fluorotoluene.     

EPR studies on regio-selective H-abstraction by “magic blue” reagent from polymers

The radical reactions of polyolefin and olefin copolymers (4-9), polydienes and diene coplymers (10-15), and polysiloxane (16) with “magic blue” reagent containing H-abstracting agent-bis{perfluoro-1-[1-(2-fluorosulfonyl)ethoxy]ethyl}nitroxide [FSO₂CF₂CF₂OCF(CF₃)]₂N(O) (2)and spin trap-perfluoro-1-nitroso-[1-(2-fluoro-sulfonyl)ethoxy]ethane FSO₂CF₂CF₂OCF(CF₃)NO (3) were studied by EPR detection of the spin adducts of the corresponding polymeric radicals generated in the H-abstraction step to the spin trap 3, namely, the nitroxides FSO₂CF₂CF₂OCF(CF₃)N(O) (polymer-H) 17-29. EPR studies have provided information about the regio-selectivity of H-abstraction, the subsequent radical steps followed H-abstraction and grounded a possibility of employing “magic blue” reagent in polymer modification via H-abstraction-initiated grafting polymerization.     

Nucleophilic fluoroalkylation of epoxides with fluorinated sulfones

The unprecedented nucleophilic fluoroalkylation of simple epoxides with fluorinated sulfones was achieved to give the beta-fluoroalkyl alcohols in one step. The negative "fluorine effect" in the nucleophilic fluoroalkylation of epoxides with fluorinated carbanions was probed by the reactivity comparison between carbanions PhSO2CF2- (3) and PhSO2CCl2- (4) and between carbanions PhSO2CHF- (7) and PhSO2CHCl- (13). The mediation of this fluorine effect by introducing another electron-withdrawing benzenesulfonyl group was found to be an effective way to significantly increase the nucleophilicity of the fluorinated carbanions, with the reactivity order [(PhSO2)2CF-] (16) > PhSO2CFH- (7) > PhSO2CF2- (3).