基于双重碳氢活化的γ,δ-不饱和酰胺与炔烃的脱氢环化反应

吡啶酮是一类重要的含氮杂环骨架,广泛存在于天然产物和药物分子中,是重要的化学转化中间体,其合成与修饰是现代医药学及化学领域的研究热点之一。杂环母核的官能团化修饰是该类化合物较为常见的衍生方式,但要求特定位点的反应基团预组装。相较而言,两个片段分子的直接偶联环化,是更为直接且具备较高实用性的合成类似杂环分子库的方式。近年来,过渡金属催化的丙烯酰胺与炔烃的氧化偶联制备吡啶酮类化合物取得了长足进展,关键活化步骤为过金属催化剂对酰胺β位sp2碳氢键的活化。然而,通过对更加易得的烷基酰胺进行sp3碳氢键活化制备杂环骨架依然具有较高的挑战性。其原因主要在于较低的α-酸性使得酰胺的脱氢反应变得异常困难。本课题组最近报道了温和条件下,铱催化的酰胺、酸及酮的空气脱氢反应。反应中产生的烯丙基-铱中间体被认为提高了酰胺的α-酸性,从而加速了脱氢过程。在此基础上,我们报道一种铑(Ⅲ)催化的γ,δ-不饱和酰胺与炔烃类化合物的脱氢环化新方法,制备一系列多取代的吡啶酮类化合物。催化循环历经酰胺导向铑(Ⅲ)对底物β位点的sp3碳氢活化,进而脱氢生成共轭的双烯酰胺中间体,随后酰胺基团再次导向铑(Ⅲ)对β位的sp2碳氢活化,进而与炔烃进行插入,环化获得吡啶酮。该反应对各种官能团具有较好的容忍性。γ-烯基结构不但促进第一步的酰胺脱氢,而且是杂环产物后修饰的重要位点。机理实验表明双烯酰胺的确为反应中间体之一。核磁实验显示酰胺脱氢迅速,而控制实验则表明炔烃的插入过程的选择性与其电性有密切的关系,有可能参与了该反应的速控步。     

Invariant Einstein metrics on generalized Wallach spaces

Invariant Einstein metrics on generalized Wallach spaces have been classified except SO(k + l+ m)/SO(k) × SO(l) × SO(m). In this paper, we first give a survey on the study of invariant Einstein metrics on generalized Wallach spaces, and prove that there are infinitely many spaces of the type SO(k + l + m)/SO(k)× SO(l) × SO(m) admitting exactly two, three, or four invariant Einstein metrics up to a homothety.     

Non-trivial m-quasi-Einstein metrics on quadratic Lie groups

We call a metric m-quasi-Einstein if \({Ric_X^m}\) (a modification of the m-Bakry–Emery Ricci tensor in terms of a suitable vector field X) is a constant multiple of the metric tensor. It is a generalization of Einstein metrics which contain Ricci solitons. In this paper, we focus on left-invariant vector fields and left-invariant Riemannian metrics on quadratic Lie groups. First we prove that any left-invariant vector field X such that the left-invariant Riemannian metric on a quadratic Lie group is m-quasi-Einstein is a Killing vector field. Then we construct infinitely many non-trivial m-quasi-Einstein metrics on solvable quadratic Lie groups G(n) for m finite.     

二次李超三系的分解定理

讨论了二次李超三系的唯一分解,得到了二次李超三系分解为非退化不可约阶化理想的分解定理.     

Semisimple weakly symmetric pseudo-Riemannian manifolds

We develop the classification of weakly symmetric pseudo-Riemannian manifolds G / H where G is a semisimple Lie group and H is a reductive subgroup. We derive the classification from the cases where G is compact, and then we discuss the (isotropy) representation of H on the tangent space of G / H and the signature of the invariant pseudo-Riemannian metric. As a consequence we obtain the classification of semisimple weakly symmetric manifolds of Lorentz signature \((n-1,1)\) and trans-Lorentzian signature \((n-2,2)\).     

磁耦合谐振式超导无线电能传输线圈错动对传输效率的影响仿真

超导以其低阻抗的特性,受到了广泛关注和应用.将超导线圈引入无线电能传输系统中,能够提升其传输性能.本文通过有限元仿真软件COMSOL Multiphysics对超导线圈错动对无线电能传输系统传输性能的影响进行了仿真,得出超导无线电能传输性能较之传统的在线圈错动时性能更好,在大功率的使用场合中能更好的适应实际情况,减少损耗,提升传输质量,为超导无线电能传输技术的应用提供了一定的参考依据.     

BaCe1—xRExO3—0.5x的溶胶—凝胶法合成及离子导电性

用溶胶－凝胶法合成了系列钙钛矿结构的ＢａＣｅ１－ｘＲＥｘＯ３－０．５ｘ（ＲＥ＝Ｌａ，Ｎｄ，Ｓｍ，Ｅｕ，Ｇｄ，Ｄｙ，Ｈｏ，Ｅｒ和Ｙ）复合氧化物，通过ＸＲＤ和热分析对样品结构及生成过程进行了研究．测定了不同温度下样品的交流阻抗谱，讨论了稀土离子掺杂对ＢａＣｅＯ３电性质的影响．溶胶－凝胶法比固相反应法合成温度降低了６００～８００℃，稀土掺杂使ＢａＣｅＯ３离子导电率提高了１０～４０倍．     

有机可溶性高折射率聚酰胺酰亚胺的合成与性能

采用含硫二胺1,4-双(4-氨基苯硫基)苯(2SPDA)与偏苯三酸酐反应制备了一种含硫二酸化合物1,4-双(4-三甲酰亚胺基苯硫基)苯(BTPB).以此二酸为原料与两种高硫含量二胺单体,4,4′-双(4-氨基苯硫基)二苯硫醚(3SDA)以及2,7-双(4-氨基苯硫基)噻蒽(APTT)通过高温缩聚法制备了两种聚酰胺酰亚胺(PAI).制备的PAI在室温下可溶解于N-甲基-2-吡咯烷酮(NMP)中.PAI薄膜的起始热分解温度(T5%)超过440℃,玻璃化转变温度(Tg)大于190℃.PAI薄膜在波长大于500nm的可见光区具有良好的透明性.此外,PAI薄膜的折射率大于1.73,双折射小于0.04.     

螯合吸附材料ASA-PGMA/SiO2对稀土离子的吸附性能研究

采用静态吸附法研究了ASA-PGMA/SiO2对稀土离子的螯合吸附性能、吸附动力学和热力学。实验结果表明,其对稀土离子的吸附能力分别为:La3+:38.6 mg.g-1,Pr3+:39.6 mg.g-1,Nd3+:41.8 mg.g-1,Sm3+:42.8 mg.g-1,Tb3+:46.2 mg.g-1。吸附等温模型符合Lang-muir型单分子层吸附。介质pH值对材料的吸附能力有很大影响,pH值为6时吸附量最大。以盐酸为洗脱剂,当酸度为0.1 mol.L-1时,洗脱率为99.8%。连续吸附-脱附实验表明,ASA-PGMA/SiO2重复使用10次后,吸附能力变化很小。     

Saturation ratio of poly(ethylene oxide) to silicate in melt intercalated nanocomposites

Melt intercalation has been found to be a very successful approach for preparation of polymer-clay nanocomposites. An aspect of this area that has been little investigated is the amount of polymer required to fill the interlayer galleries of the clay. This paper reports experiments which determine the amount of poly(ethylene oxide) (PEO) required to saturate the spacing between montmorillonite (MMT) or organically-modified bentonite (B34) layers. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to determine the saturation ratios of PEO to silicates, which are then compared to theoretical calculations. The deduced saturation ratio of PEO to MMT is 28:72, and PEO to B34 15:85 by XRD and DSC, whilst ratios of PEO to MMT of 21:79 and PEO to B34 10:90 were obtained via TGA. The density of intercalated PEO in the silicate galleries is estimated to be 0.82 g/cm³, which suggests that PEO in the silicate galleries is far less efficiently packed than in the amorphous region of the bulk polymer.