分子内环加成的甾体全合成

近年来,分子内环加成反应已广泛用于甾体化合物全合成,其主要一步是由取代的苯并环丁烯热裂而成的5,6-二亚甲基-1,3-环己二烯发生区域专一和立体选择性的环加成反应,构成甾体骨架。现在用此法已合成了一系列消旋和光学活性的甾体化合物。     

青蒿素及其一类物结构和合成的研究——Ⅸ.全合成青蒿素中若干关键化合物的合成

青蒿素是一个含有过氧基团的新型倍半萜内酯~([1]),它具有突出的抗疟作用~([2])。本文报道     

Improved electrochemical performance of LiNi0.5Mn1.5O4 as cathode of lithium ion battery by Co and Cr co-doping

Three samples, LiNi_0.5Mn_1.5O₄, LiNi_0.4Mn_1.4Co_0.2O₄, and LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄, were prepared by sol–gel method and characterized by powder X-ray diffraction, Fourier transformed infrared spectroscope, scanning electron microscopy, Brunauer–Emmett–Teller surface area, four-probe resistance, cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge test. It is found that the co-doped sample LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄ exhibits an improved performance compared with the Co-doped sample LiNi_0.4Mn_1.4Co_0.2O₄ and the undoped sample LiNi_0.5Mn_1.5O₄, especially at elevated temperature. At 25 °C, the discharge capacity of LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄ is 130 mAh g^?1 at 0.1 C and 103 mAh g^?1 at 10 C. At an elevated temperature (55 °C), its 1 C discharge capacity is 136 mAh g^?1 and maintains 95.6 % of its initial capacity after 100 cycles. Compared with the reported results of LiNi_0.4Mn_1.4Co_0.2O₄ and LiNi_0.475Mn_1.475Co_0.05O₄, the co-doped sample LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄, with least content of Co, 0.05, possesses not only the high C-rate capacity but also the structural stability. The mechanism on the electrochemical performance improvement of LiNi_0.5Mn_1.5O₄ by the co-doping was discussed.     

PEO/PVDF-based gel polymer electrolyte by incorporating nano-TiO2 for electrochromic glass

Journal of Sol-Gel Science and Technology - To develop high performance mixed matrix gel polymer electrolyte, the synergistic effect of blending PVDF (PEO/PVDF weigh ratio of 85:15) and adding...     

Phenylcarbamoylated β‐CD: π‐Acidic and π‐basic chiral selectors for HPLC

Two types of chiral stationary phases for HPLC based on π‐acidic or π‐basic perphenylcarbamoylated β‐CDs were synthesized. The relative structural features of the two effective chiral selectors are discussed and compared in both normal‐phase and RP modes. In addition, the nature and concentration of alcoholic modifiers were varied for optimal separation in normal phase and the structural variation of the analytes was also examined. The results showed that hydrogen bonding, steric effect and π‐acidic–π‐basic interaction contributed greatly to enantioseparation. Upon comparison, some of the differences in the separation behavior of the two types of chiral stationary phases might be due to the π‐acidic or π‐basic phenylcarbamate groups.     

Theoretic calculation for understanding the oxidation process of 1,4-dimethoxybenzene-based compounds as redox shuttles for overcharge protection of lithium ion batteries

The effect of substituents on the oxidation potential for the one-electron reaction of 1,4-dimethoxybenzene was understood with a theoretical calculation based on density functional theory (DFT) at the level of B3LYP/6-311+G(d). It is found that the oxidation potential for the one-electron reaction of 1,4-dimethoxybenzene is 4.13 V (vs Li/Li(+)) and can be changed from 3.8 to 5.9 V (vs Li/Li(+)) by substituting electron-donating or electron-withdrawing groups for the hydrogen atoms on the aromatic ring. These potentials are in the range of the limited potentials for the lithium ion batteries using different cathode materials, and thus the substituted compounds can be selected as the redox shuttles for the overcharge prevention of these batteries. The oxidation potential of 1,4-dimethoxybenzene decreases when the hydrogen atoms are replaced with electron-donating groups but increases when replaced with electron-withdrawing groups. The further oxidation of these substituted compounds was also analyzed on the basis of the theoretic calculation.     

Density functional theory study of the role of anions on the oxidative decomposition reaction of propylene carbonate

The oxidative decomposition mechanism of the lithium battery electrolyte solvent propylene carbonate (PC) with and without PF(6)(-) and ClO(4)(-) anions has been investigated using the density functional theory at the B3LYP/6-311++G(d) level. Calculations were performed in the gas phase (dielectric constant ε = 1) and employing the polarized continuum model with a dielectric constant ε = 20.5 to implicitly account for solvent effects. It has been found that the presence of PF(6)(-) and ClO(4)(-) anions significantly reduces PC oxidation stability, stabilizes the PC-anion oxidation decomposition products, and changes the order of the oxidation decomposition paths. The primary oxidative decomposition products of PC-PF(6)(-) and PC-ClO(4)(-) were CO(2) and acetone radical. Formation of HF and PF(5) was observed upon the initial step of PC-PF(6)(-) oxidation while HClO(4) formed during initial oxidation of PC-ClO(4)(-). The products from the less likely reaction paths included propanal, a polymer with fluorine and fluoro-alkanols for PC-PF(6)(-) decomposition, while acetic acid, carboxylic acid anhydrides, and Cl(-) were found among the decomposition products of PC-ClO(4)(-). The decomposition pathways with the lowest barrier for the oxidized PC-PF(6)(-) and PC-ClO(4)(-) complexes did not result in the incorporation of the fluorine from PF(6)(-) or ClO(4)(-) into the most probable reaction products despite anions and HF being involved in the decomposition mechanism; however, the pathway with the second lowest barrier for the PC-PF(6)(-) oxidative ring-opening resulted in a formation of fluoro-organic compounds, suggesting that these toxic compounds could form at elevated temperatures under oxidizing conditions.     

Hydrazone-based ligands for micro-solid phase extraction-high performance liquid chromatographic determination of biogenic amines in orange juice

Eight hydrazone-based ligands were synthesized, trapped in a silica sol-gel matrix, and were subsequently used in the micro-solid phase extraction (μ-SPE) of biogenic amines (BAs). The BAs investigated were tryptamine, phenylethylamine, putrescine, histamine, tyramine and spermidine. Prior to the extraction, dansyl chloride was added to the samples which were heated to 70°C for 10 min. The samples were extracted with μ-SPE, after which analytes were desorbed using acetonitrile via ultrasonication. The extracts were analysed by high performance liquid chromatography (HPLC) with ultraviolet detection. Of the eight ligands investigated as sorbents, benzophenone 2,4-dinitrophenylhydrazone was found to be the most promising. The enhanced π-π interaction between the analytes and the ligand facilitated the adsorption process. Under the most suitable extraction conditions, the method demonstrated good linearity with correlation coefficient of more than 0.985 over a concentration range of 1-50 μg L(-1). Satisfactory repeatability with relative standard deviations of 7.43-11.30% (n=3) were obtained. Detection limits ranged from 3.8 to 31.3 ng L(-1). The μ-SPE method exhibited lower recoveries (71.5-87.4%) when compared to the solid phase extraction technique (79.7-95.0%), but enrichment factors of 94-460 were obtained. The proposed μ-SPE-HPLC method was applied to the determination of BAs in orange juice purchased from local supermarkets, with satisfactory results. The orange juices were characterized by the presence of relatively high levels of putrescine (range, 550-2210 μg L(-1)) but tryptamine and phenylethylamine were not detected in any of the tested samples.     

1α,2α-次甲基氯地孕酮醋酸酯合成方法的改进

本文报道了合成1α,2α-次甲基氯地孕酮醋酸酯5的改良法,即以17α-羟基黄体酮1为原料,用节杆菌和NBS-碳酸钙代替了有毒试剂四氯苯醌和二氯二氰苯醌脱氢,制得基关键中间体△~(1,4,6)-化合物3。从3经五步反应即得目的物5。