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81.
《Tetrahedron letters》2014,55(50):6861-6863
The reaction of t-butyldiphenylsilyl (TBDPS) chloride with secondary alcohols was catalyzed by pyrrolidinopyridine N-oxide (PPYO) in the presence of diisopropylethylamine (DIPEA) at room temperature, giving the corresponding TBDPS ethers in high yields. 相似文献
82.
《Tetrahedron》2014,70(32):4738-4744
Gram-scale total synthesis of (±)-8-[1-(4′-hydroxy-3′-methoxyphenyl)prop-2-en-1-yl]-galangin (1) and -chrysin (2) has been accomplished in eight steps from commercially available phloroglucinol and three steps from commercially available chrysin, respectively, featuring an efficient introduction of C(8) (1-prop-2-en-1-yl)phenyl moiety in the natural products through chemo- and regioselective cinnamylation and regioselective aromatic Claisen rearrangement. 相似文献
83.
A general and efficient P(V)–N activation method for the preparation of symmetrical and asymmetrical dinucleoside polyphosphates (NpnN′s, n=2–4) and P2,P3-CX2-dinucleoside tetraphosphates (X=H, F, and Cl) has been established. Twenty-two dinucleoside polyphosphates and their phosphonate analogs were synthesized from nucleoside 5′-phosphoropiperidates with 4,5-dicyanoimidazole as the activator in good to high yields. 相似文献
84.
Direct anodic oxidation of 1,5-dihydroxynaphthalene (DHN), an important derivative of naphthalene, led to the formation of high-quality semiconducting poly(1,5-dihydroxynaphthalene) (PDHN) on stainless steel sheets in boron trifluoride diethyl etherate (BFEE). The onset oxidation potential of DHN in this medium was measured to be only 0.78 V vs. SCE, which was lower than that determined in traditional acetonitrile containing 0.1 mol/L tetrabutylammonium tetrafluoroborate (0.98 V vs. SCE). As-formed PDHN films showed good redox activity and stability, together with interesting electrochromic property from brown (doped) to yellow-green (dedoped). Structural characterization, including FTIR, 1H NMR, and quantum chemistry calculations, indicated that the polymerization of DHN probably occurred at C4 and C8 positions. Moreover, thermal analysis revealed that PDHN displayed better thermal stability than that synthesized by chemical method. The fluorescence spectral studies, together with the electrical tests, showed that PDHN was a good blue light-emitter (fluorescence quantum yield higher than 0.1) with an electrical conductivity of as high as 0.46 S/cm. 相似文献
85.
This letter does some further researches on a newly proposed hyper-chaos found in [Gao TG, Chen ZQ, Chen G. A hyper-chaos Generated from Chen’s system, Int J Mod Phys C 2006;17(4):471–8], and gets some new results with some parameters of the system are definite and the other one varies. The basic dynamical behavior of the system under various conditions is analyzed, and the new findings is not only demonstrated by computer simulations but also verified with bifurcation analysis. 相似文献
86.
87.
A complex [Cu2Br2(L)2]n(1) (L=bis(2-pyrimidinylthio)methane) has been synthesized and structurally characterized. Complex 1 contains dinuclear Cu2Br2 units, which are linked by ditopic L to form a 2D layer structure with a 36-membered macrometallocycle. The adjacent layers are further connected through interpyrimidyl rings C-H…N and π-π interactions to give rise to a three-dimensional supramolecular structure. Complex 1 also displays strong green solid-state photoluminescence, due to metal-to-ligand charge-transfer (MLCT) at room temperature. CCDC: 711434. 相似文献
88.
重构核插值法是近年来提出的一种新型无网格方法.该方法的形函数具有点插值性和高阶光滑性,不仅能够直接施加本质边界条件,而且能保证较高的计算精度.为了更有效地求解三维轴对称弹性动力学问题,对重构核插值法(reproducing kernel interpolation method, RKIM)应用于此类问题进行了研究,并发展了相应的数值模拟方法.由于几何形状和边界条件的轴对称性,计算时只需要横截面上离散节点的信息,因而前处理变得简单.采用Newmark-β法进行了时域积分.数值算例表明,轴对称弹性动力学分析的重构核插值法既有无网格方法的优势,又有较高的计算精度. 相似文献
89.
90.
基于相对熵的不完全信息群体专家权重的集结 总被引:2,自引:1,他引:1
万树平 《应用数学与计算数学学报》2009,23(1):66-70
针对属性权重信息和属性效用信息都不完全的群体多属性决策问题,运用相对熵理论提出了一种专家权重的确定方法.该方法通过集结各方案的综合评价值向量,客观地得到专家的权重,避免系统聚类方法中由给定相似度水平归类而产生的主观性问题.应用实例表明了方法的有效性和实用性. 相似文献