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311.
An efficient method for palladium-catalyzed homocoupling reaction of terminal alkynes in the synthesis of symmetric diynes is presented. The results showed that both Pd(OAc)(2) and CuI played crucial roles in the reaction. In the presence of 2 mol % Pd(OAc)(2), 2 mol % CuI, 3 equiv of Dabco, and air, homocoupling of various terminal alkynes afforded the corresponding symmetrical diynes in moderate to excellent yields, whereas low yields were obtained without either Pd(OAc)(2) or CuI. Moreover, high TONs (turnover numbers; up to 940 000 for the reaction of phenylacetylene) for the homocoupling reaction were observed. Under similar reaction conditions, cross-coupling of 1-iodo-4-nitrobenzene with phenylacetylene was also carried out smoothly in quantitative yield. However, the presence of CuI disfavored the palladium-catalyzed Sonogashira cross-coupling reactions of the less active aryl iodides and bromides. In the presence of 0.01-2 mol % Pd(OAc)(2), a number of aryl iodides and bromides were coupled with terminal alkynes in good to excellent yields. It is noteworthy that this protocol employs mild, efficient, aerobic, copper-free, and ligand-free conditions. 相似文献
312.
反相悬浮聚合法合成超强吸水剂 总被引:23,自引:0,他引:23
以两性高分子作悬浮稳定剂,用反相悬浮聚合法合成了聚(丙烯酸盐-丙烯酰胺)类超强吸水剂.研究了交联剂、稳定剂、引发剂等用量、中和程度、单体组成及链转移剂等聚合条件对吸水剂吸水性能的影响.得到了吸蒸馏水1050mL/g及吸0.9%NaCl溶液86mL/g的超强吸水剂.此外,还比较了含不同反离子的聚丙烯酸类吸水剂的吸水性能 相似文献
313.
314.
Yan Ping Wang Wen Fa Xie Bin Li Wen Lian Li 《中国化学快报》2007,18(12):1501-1504
A new 1,3,4-oxadiazole-contanining rhenium(I) complex,with the formula [Re(CO)_3(Bphen)(PTOP)],(Bphen=bathophe- nardine,PTOP=4-(5-p-tolyl-1,3,4-oxadiazd-2-yl)pyridine),is synthesized and characterized by elemental analysis,IR,~1H NMR, UV-vis and luminescence spectroscopy.The double-layer electroluminescence devices based on the Re(I) complex have been fabricated by spin-coating technique.The turn-on voltage,maximum efficiency,and brightness for green emission obtained from the devices are 9V,2.1cd/A and 165cd/m~2,respectively. 相似文献
315.
Zhi-min Zheng Cai-hong Xu Jian Jiang Chang-yu Ren Wei Gao Ze-min Xie Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing China 《高分子科学》2002,(6):559-564
Silicone rubber (SIR) shows superior performance when used outdoors, but its surface can be transformed frominherently hydrophobic to hydrophilic by the adsorption of contaminants. Al(OH)_3, Al_2O_3, quartz powder and active carbonwere selected as authentic contaminants. Hydrophobicity of the surface was determined using contact angle measurement.The results indicate that the adsorbability of the contaminants can strongly affect the hydrophobicity of contaminated SIRsurface. The increasing rate of contact angle of specimens contaminated by Al(OH)_3 was much faster than that by Al_2O_3 andquartz due to the adsorption of migrated low molecular weight (LMW) polydimethylsiloxanes. Specimens contaminated byactive carbon could achieve sunde hydrophobicity within 15 min because active carbon has high adsorbability. Surfaces ofcontaminated ultrapure SIR, polytetrafluoroethylene (PTFE) and glass remain hydrophilic because they contain no mobileLMW components. The addition of oligomeric polydimethylsiloxanes has little effect on the hydrophobicity of contaminantscovered on SIR surface. 相似文献
316.
混合三烃基锡衍生物的研究:X.甲基二环己基锡二硫代磷酸酯的合成及生… 总被引:4,自引:2,他引:4
合成了10种甲基二环己基锡-O,O-二烃基二硫代磷酸酯,利用IR,NMR,MS及元素分析确证了化合物的结构,生物活性测试结果表明,这类化合物具有较高的杀螨和除草活性。 相似文献
317.
从自模式曲线分辨到渐进类因子分析法 总被引:1,自引:1,他引:1
本文对自模式曲线分辨法的发展作了简要回顾,其中特别对近来来迅速发展的一类用于色谱波谱联用仪产生的二维分析数据的渐进类分析法作了详尽的讨论。这些新化学计量学方法的涌现,对复杂的未知分析体系的定性定量分析,将带来深刻的变化。 相似文献
318.
Cs2CO3 was found to efficiently catalyze the reaction of β-cyclodextrin and N-tosylimidazole. Stirring β-cyclodextrin and N-tosylimidazole in 1/1.2 molar ratio in DMF in the presence of catalytic amount of Cs2CO3 at rt for 1.5 h afforded 2A-mono(O-tosyl)-β-cyclodextrin in 32% yield. The 2A,2B-, 2A,2C- and 2A,2D-ditosylates were isolated in ca. 6-7% yields, respectively, when β-cyclodextrin and N-tosylimidazole were used in 1/2.5 molar ratio. The charge of excess (10 equiv) of N-tosylimidazole ensured a one-step direct (protection-free) synthesis of the per(2-O-tosyl)-β-cyclodextrin in 5% isolated yield. N-(m-Nitrobenzenesulfonyl)imidazole even allowed a much faster access to the corresponding persulfonate in only 1 h reaction. 相似文献
319.
用X光衍射(XRD)方法研究了CrO_3/SiO_2和CrO_3/γ-Al_2O_3体系。用相定量外推法测定活性组份在载体表面的最大分散量。在干燥气氛中将CrO_3与载体混合, 并在低于CrO_3熔点的温度下烘烤制备样品, 实验得到CrO_3在SiO_2或者γ-Al_2O_3表面的最大分散量都随温度的升高而增大。CrO_3在SiO_2表面的最大分散量由101 ℃的0.27gCrO_3/g SiO_2到170 ℃的0.38g CrO_3/g SiO_2; CrO_3在γ-Al_2O_3表面的最大分散量由120 ℃的0.22g CrO_3/g γ-Al_2O_3到171 ℃的0.42g CrO_3/g γ-Al_2O_3。CrO_3在SiO_2或γ-Al_2O_3表面的最大分散量超过密置单层量, 可由易聚合形成同多酸根来解释。 相似文献
320.
NH_3Ã(~1A_2~″)是一个快速预解离态, 以往的光谱研究从未得到它的转动分辨光谱。我们用两个脉冲染料激光器研究了NH_3C′→X的3+1多光子电离光谱和NH_3X→C′→Ã的折叠光学双共振多光子电离光谱, 称为“离子凹陷光谱”。对前者观察到了较高分辨的转动光谱, 得出C′v_2~′=O的高精度转动常数。通过谱线宽度, 得到了C′v_2~′=0,1,2能级的预解离寿命。从离子凹陷光谱上, 首次观察到了C′→Ã跃迁的0-0, 1-1, 2-2等带的转动分辨光谱。由双共振选择定则简化的光谱使漫散至~50 cm~(-1)线宽的转动线得以分开, 由此得到Ãv_2~″=0,1,2能级的转动常数和各谱带的带原点。在消除功率加宽的情况下, 测出Ãv_2~′=1能级的寿命。这种方法对研究分子的快速预解离态有一定的普遍意义。 相似文献