Divergent total synthesis of aspinolides B,E and J

Stereoselective total synthesis of aspinolides B, E and J, naturally occurring 10-membered lactones, were accomplished by divergent strategies starting from the commercially available 2,3-O-isopropylidene-d-ribose and methyl d-lactate. The synthesis features rapid access to the both key fragments from chiral pool and the formation of 10-membered ring lactones containing trans double bond employing cross-metathesis reaction (CM) and intramolecular Shiina macrolactonization.     

基于积分渐进展开的气相色谱重叠峰快速解析法

论文提出用积分渐进展开解析气相色谱重叠峰,该方法有3个主要步骤：首先将谷峰或肩峰分成两个积分区域,得到一个子区域的积分方程和一个重叠峰面积的代数方程;然后用数值积分求出这两个方程计算中所需要的峰面积,再用积分渐进公式将积分方程展开成代数方程;最后,将这两个方程与峰高约束方程联立后,得到一个非线性代数方程组,用Gauss-Seidel迭代可以快速求解方程组,方程收敛的最大迭代次数不超过20次。仿真和实验结果表明,解析的峰高和峰面积误差均很小,峰面积最大误差低于6.44%,峰高的最大误差约为6.80%。由于该算法精度高,效率高,所以这个方法可以用于气相色谱重叠峰和一般色谱峰的实时在线解析。     

HL—1M装置欧姆等离子体实验的初步分析

从１９９４年１０月２４日开始，对ＨＬ－１Ｍ装置进行欧姆加热等离子体的调试实验，获得了Ｉｐ＝３１０ｋＡ，ｑｎ＜２．５，ｎｃ＝３×１０＾１３ｃｍ＾－３，Ｔｃ（０）＞１ｋｅＶ，Ｔｉ（０）＞０．５ｋｅＶ和τＥ≈１０ｍｓ的平衡稳定等离子体。本文简述了ＨＬ－１Ｍ装置及其诊断等的实验结果进行了初步分析和讨论。     

柱面光栅Talbot效应

本文在傍轴近似下,导出了柱面波照射下柱面光栅的Talbot自成象一般公式。它与在球面波照射下平面光栅的自成象规律类似。此一般公式在极限情况下,可退化出已知的平面光栅成象公式。     

十六烷基三甲基溴化铵相转移催化合成N,N—二乙基苯胺的研究

十六烷基三甲基溴化铵相转移催化合成Ｎ，Ｎ－二乙基苯胺的研究田庆伟（大连铁道学院应用化学系大连１１６０２８）关键词十六烷基三甲基溴化铵相转移催化Ｎ，Ｎ－二乙基苯胺中图分类号０６２５．６３１Ｎ，Ｎ－二乙基苯胺是制备染料、药物和彩色显影剂的重要中间体，用途...     

Direct observation of the evolving metal–support interaction of individual cobalt nanoparticles at the titania and silica interface

Understanding the metal–support interaction (MSI) is crucial to comprehend how the catalyst support affects performance and whether this interaction can be exploited in order to design new catalysts with enhanced properties. Spatially resolved soft X-ray absorption spectroscopy (XAS) in combination with Atomic Force Microscopy (AFM) and Scanning Helium Ion-Milling Microscopy (SHIM) has been applied to visualise and characterise the behaviour of individual cobalt nanoparticles (CoNPs) supported on two-dimensional substrates (SiO_xSi(100) (x < 2) and rutile TiO₂(110)) after undergoing reduction–oxidation–reduction (ROR). The behaviour of the Co species is observed to be strongly dependent on the type of support. For SiO_xSi a weaker MSI between Co and the support allows a complete reduction of CoNPs although they migrate and agglomerate. In contrast, a stronger MSI of CoNPs on TiO₂ leads to only a partial reduction under H₂ at 773 K (as observed from Co L₃-edge XAS data) due to enhanced TiO₂ binding of surface-exposed cobalt. SHIM data revealed that the interaction of the CoNPs is so strong on TiO₂, that they are seen to spread at and below the surface and even to migrate up to ∼40 nm away. These results allow us to better understand deactivation phenomena and additionally demonstrate a new understanding concerning the nature of the MSI for Co/TiO₂ and suggest that there is scope for careful control of the post-synthetic thermal treatment for the tuning of this interaction and ultimately the catalytic performance.

Understanding the metal–support interaction (MSI) is crucial to comprehend how the catalyst support affects performance and whether this interaction can be exploited in order to design new catalysts with enhanced properties.     

Poly(fluoroalkyl acrylate)-bound ruthenium carbene complex: a fluorous and recyclable catalyst for ring-closing olefin metathesis

The synthesis of a fluorous olefin metathesis catalyst derived from the Grubbs second-generation ruthenium carbene complex is described. The air stable fluorous polymer-bound ruthenium carbene complex 1 shows high reactivity in effecting the ring-closing metathesis of a broad spectrum of diene and enyne substrates leading to the formation of di-, tri-, and tetrasubstituted cyclic olefins in minimally fluorous solvent systems (PhCF3/CH2Cl2, 1:9-1:49 v/v). The catalyst can be readily separated from the reaction mixture by fluorous extraction with FC-72 and repeatedly reused. The practical advantage offered by the fluorous catalyst is demonstrated by its sequential use in up to five different metathesis reactions.     

Synthesis and mesomorphism of new aliphatic polycarbonates containing side cholesteryl groups

New cholesterol side-functionalised polycarbonate polymers were synthesised by the ring-opening homo- and copolymerisation reaction of the cyclic monomer cholesteryl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate and d,l-lactide using Sn(Oct)₂ as a catalyst. The chemical structures and average molecular weights of the cyclic monomer, homopolymer and block copolymers obtained in this study were characterised using FT-IR, ¹H NMR and gel permeation chromatographic measurement. The mesomorphism and mesophase structure were investigated with polarising optical microscopy, differential scanning calorimetry and X-ray diffraction measurement. As a result, the homopolymer and block copolymers showed an enantiotropic smectic A (SmA) phase. With the concentration of the lactide segment increasing, the glass transition temperature and isotropic temperature of the corresponding block copolymer all decreased. In addition, XRD suggested that the homopolymer and two block copolymers showed the SmA double-layer packing of side chains.     

One Fluorophore-Two Sensing Films: Hydrogen-Bond Directed Formation of a Quadruple Perylene Bisimide Stack

Elaborately designed π-stacked molecular aggregates are significant for modulation of photophysical properties of polycyclic aromatic hydrocarbons (PAHs). Herein, a double hydrogen-bonds trussed di(pyridyl)pyrrole-perylene bisimide (HDPP-PBI) was designed and its dimerization behavior was studied. HDPP-PBI tends to form a quadruple PBI stack with a dimerization constant of ∼5.56×10⁶ M⁻¹. The dimerization was ascribed to synergistic intramolecular double hydrogen-bonds formation and intermolecular π-π stacking. Addition of CF₃COOH, a hydrogen bond blocker, promotes the dimer to monomer transition. Accordingly, two distinct fluorescent films were prepared by drop-casting of the dimerized or the monomeric HDPP-PBI onto a substrate surface. Interestingly, the less-emissive PBI quadruple stack-based film showed a turn on response to acetone vapor, while the highly emissive HDPP-PBI-based film exhibited fluorescence quenching upon exposure to triethylamine vapor. We believe that the discovered synergistic effect in the PBI aggregates would enlighten the design of new PAHs aggregates with defined structures.