Alkyne Insertion Enabled Vinyl to Acyl 1,5-Palladium Migration: Rapid Access to Substituted 5-Membered-Dihydrobenzofurans and Indolines

“Through space” palladium/hydrogen shift is an efficient strategy to achieve selective functionalization of a specific remote C−H bond. Compared with relatively extensive exploited 1,4-palladium migration process, the relevant 1,5-Pd/H shift was far less investigated. We herein report a novel 1,5-Pd/H shift pattern between a vinyl and an acyl group. Through the pattern, rapid access to 5-membered-dihydrobenzofuran and indoline derivatives has been achieved. Further studies have unveiled an unprecedented trifunctionalization (vinylation, alkynylation and amination) of a phenyl ring through 1,5-palladium migration relayed decarbonylative Catellani type reaction. A series of mechanistic investigations and DFT calculations have provided insights into the reaction pathway. Notably, it was unveiled that the 1,5-palladium migration in our case prefers a stepwise mechanism involving a Pd^IV intermediate.     

Palladium-ytterbium bimetallic electrocatalysts supported on carbon black,titanium suboxide,or poly(diallyldimethylammonium chloride)-functionalized titanium suboxide towards methanol oxidation in alkaline media

Palladium-ytterbium (Pd-Yb) bimetallic catalysts with different Pd/Yb ratios supported on carbon black (20%Pd-x%Yb/C, x?=?0, 1, 5, 10, and 15) were prepared by a sodium borohydride reduction method. The 20%Pd-5%Yb/C catalyst exhibited the best electrocatalytic activity towards methanol oxidation in alkaline media. The improved electrocatalytic activity and stability of 20%Pd-5%Yb/C can be explained by a bi-functional mechanism. In addition, the higher content of metallic palladium caused by the addition of ytterbium also contributes to the better catalytic activity of the 20%Pd+5%Yb/C catalyst. In view of the good electrocatalytic performance of 20%Pd+5%Yb/C, the 20%Pd+5%Yb catalyst supported on titanium suboxide (20%Pd+5%Yb/Ti₄O₇) was prepared. However, the Pd-Yb particles supported on Ti₄O₇ were seriously agglomerated. To improve the dispersion status of alloy particles, the Ti₄O₇ was functionalized with poly(diallyldimethylammonium chloride) (Ti₄O₇-PDDA). Electrochemical characterizations showed that no matter Ti₄O₇ or Ti₄O₇-PDDA as supports, Pd-Yb catalysts exhibited better catalytic activity than 20%Pd-5%Yb/C. The improvement mainly results from the further increase of metallic Pd due to the presence of Ti₄O₇.     

混合态二能级原子双光子过程中的光子聚束与反聚束效应

本文采用时间演化算符方法和数值计算研究了相干光场与混合态二能级原子双光子过程中的光子聚束与反聚束效应,结果表明量子崩塌与复苏性质和原子初始的混合程度无关,当0.97≤|S|≤1时,辐射光子会周期性地呈现短时的反聚束性质,随着原子初始混合程度的增大,二阶相干函数g     

重组大肠杆菌固定床间歇生产β-葡聚糖酶

以多孔陶瓷为载体,吸附法固定化重组大肠杆菌并进行固定床间歇培养.在循环流速44.19mL/min,曝气量为0.6mL/min时,培养48h后发酵液的酶活力达100.3U/mL.固定化细胞具有良好的重复使用能力,在连续5批次实验中,培养48h后的酶活力均在100U/mL左右.     

酚醛树脂对B/KNO_3点火药的激光点火特性的影响

用光声-光电测试法,EMS方法和DSC热分析方法研究酚醛树脂对B／KNO3点火药的激光点火特性的影响。研究结果表明,在一定的入射激光能量下,当有酚醛树脂时,B／KNO3体系点火药的点火延迟期缩短,光声信号也减小,酚醛树脂的作用在于抑制样品的能量和物质量向环境流失。样品表面激光烧蚀斑的电子显微照相表明有无酚醛树酯,药剂的烧蚀情况无明显的差异,激光在药剂表面形成多个点火中心。     

基于波束空间的自适应波束形成算法

提出了一种稳健的波束形成算法。该算法利用干扰信号的导引向量和噪声向量对接收信号的协方差矩阵进行重构,经此处理后的协方差矩阵的信号子空间中不再包含期望信号成分,使得当期望信号功率较强时应用LCMV算法也不会对期望信号进行抑制。此外,算法还引入了锥形方差矩阵技术增强算法抑制干扰的能力。最后仿真证明了该算法的有效性。     

不同氧/燃比的硼-硝酸钾的激光点火特性

硼-硝酸钾是一种重要的含能材料,其氧/燃比与药剂的点火和燃烧性能有密切关系.为了掌握氧/燃比与激光点火性能的关系,对不同配比的硼-硝酸钾及其酚醛树脂掺杂物进行激光点火特性实验研究、热力学参数计算分析和热分析.结果表明,硼-硝酸钾的激光点火过程由激光烧蚀、热化学反应和自持燃烧等阶段构成;随着硼质量分数从30%增加到70%,50%发火的激光点火阈值存在一个最小值,分别为7.6 mJ(m(B)∶m(KNO3):50∶50)和4.05 mJ(m(B)∶m(KNO3)∶m(酚醛树脂):40∶50∶5);激光点火延迟时间与激光点火能量密度的关系近似为线性递减关系,并且具有较低激光点火能量阈值的配比也具有较短的激光点火延迟时间;酚醛树脂将B-KNO3的化学反应起始温度从556 ℃降低到548 ℃,化学反应放热量从1.86 kJ/g增大到2.21 kJ/g,提高了激光点火感度和缩短了点火延迟时间.     

光催化制氢的助催化剂

随着能源和环境问题的日益突出,构建可持续发展、绿色环保和新型高效的能源体系,成为当今世界关注的焦点.由于太阳能清洁、低成本和环境友好等特性,利用太阳能光催化制氢成为解决能源问题的有效策略.单一的半导体光催化剂由于光的利用率低、电荷空穴易复合和缺少充足的活性位点等缺点,很难满足光催化的所有要求,常引入助催化剂来解决这一问...     

LD抽运Cr4+,Nd3+:YAG晶体获得1.4W自调Q激光输出

用激光二极管(LD)抽运Cr4+,Nd3+∶YAG晶体获得了1.064 μm的自调Q激光输出.激光输出模式为稳定的单纵模,抽运阈值功率为3.5 W,脉冲宽度为50 ns,斜率效率高达20%.当输入的抽运功率为10.8 W时,获得了1.46 W的自调Q激光输出.随着抽运功率的变化,脉冲宽度基本上保持不变,而重复率则在变化.     

含有萘酰亚胺的菁染料太阳能电池敏化剂的合成

通过Click反应把萘酰亚胺化合物连接到含有醛基的吲哚上,再通过醛基和吲哚碘盐的Knoevenagel缩合反应合成出带有萘酰亚胺部分的菁染料,用NMR、MS、元素分析、UV-Vis等方法对其结构和性能进行了表征和测试。