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1.
Recyclable and reusable Pd(OAc)2/PPh3/PEG‐2000 system for homocoupling reaction of arylboronic acids under air without base
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A stable and efficient Pd(OAc)2/PPh3/PEG‐2000 catalytic system for homocoupling of arylboronic acids has been developed. In the presence of Pd(OAc)2 and PPh3, the homocoupling reaction of arylboronic acids was carried out smoothly in PEG‐2000 at 70 °C under air without base to afford a variety of symmetric biaryls in good to excellent yields. The isolation of the products was readily performed by extraction with diethyl ether, and the Pd(OAc)2/PPh3/PEG‐2000 system could be easily recycled and reused six times without significant loss of catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
2.
ChujiangCai ZhigangShen MingzhuWang ShulinMa YushanXing 《中国颗粒学报》2003,1(4):156-161
This paper reports the use of a colloidal Pd^0 catalysis system to metallize the surface of precipitators separated from coal fly-ash, and metals such as Cu, Ni etc. are deposited on the precipitators surface. Alternatively, according to the characteristic surface of cenospheres, an Ag coating catalysis system is adopted to first deposit Ag on the cenospheres surface, followed, if necessary, by the deposition of other metals such as Cu, Ni, etc. on the Ag coating to produce monolayer and multilayer metal-coated cenospheres. The surface characteristics and the morphologies of the metal coatings are examined in detail with scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) techniques. It can be shown that the quality of metal coatings derived from the Aa coatina catalysis system, is better than that of the colloidal Pd^0 catalysis system. 相似文献
3.
Fabrication of tunable colloid crystals from amine-terminated polyamidoamine dendrimers 总被引:1,自引:0,他引:1
Mingzhu Li Jingxia Wang Lin Feng Bingbing Wang Xinru Jia Lei Jiang Yanlin Song Daoben Zhu 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,290(1-3):233-238
A pH-responsive colloidal crystal was assembled using core-shell composite spheres, poly(styrene-methyl methacrylate-acrylic acid) (P(St-MMA-AA)) spheres covered by generation 4 amine-terminated polyamidoamine dendrimers. The light reflection of the colloidal crystal film can be tuned at different pH due to different protonation level of the dendrimers. The method shows a facile way to fabricate diffraction-based chemical and biological sensors by exploiting the effect of photonic crystal cooperated with tunable nanoparticles. 相似文献
4.
将40只雄性SD大鼠随机分成两组,采用猪油(L)或玉粮米油(M)加胆固醇饲料诱导出大高血脂模型后,再分出两组、分别加入亚硒酸钠(L-Se,M-Se),观察大鼠补硒后血清中锌铜、锌、钙、镁等元素的变化。结果表明,高血脂大鼠补硒后血 锌的含量明显下降,铜/锌比值长高。相关分析显示:血硒水平与血清锌含量呈负相关,各组大鼠血清铜、钙、镁的浓度未观察到显著性差异。 相似文献
5.
Mingzhu Liu Rongshi Cheng Jingjia Wu Cheng Ma 《Journal of polymer science. Part A, Polymer chemistry》1993,31(13):3181-3186
A study was made of the ceric ammonium nitrate (CAN) initiated graft copolymerization of methyl acrylate (MA) onto potato starch. The variables affecting the graft were investigated. The optimums have been obtained; they are the concentrations of MA, CAN, and nitric acid (HNO3) (1.08, 5.0 × 10?3, and 0.081 mol/L, respectively). The reaction temperature is ca. 50°C and the reaction time is 2 h. The molecular weight of grafted poly(methylacrylate) has been determined. On the basis of experimental results, the mechanism of grafting has been explored, a new kinetic equation of the graft copolymerization is established: Rp = Kkd [STOH] [Ce4+] + Kkpkd/kt[STOH][M], where K, kd, kp, and kt are constants. The equation fits the results of experiments. © 1993 John Wiley & Sons, Inc. 相似文献
6.
A super-absorbent polymer is prepared by graft polymerizing acrylamide (AM) ontopotato starch using ceric ammonium nitrate (CAN) and N, N′-methylene-bis-acrylamide(bisAM) as an initiator and cross-linking agent respectively, and then subjecting the potatostarch-poly(acrylamide) (PAM) graft copolymer (SPAM ) to alkaline saponification. Thewater absorbency (WA) of the sample is nearly 5000 g H_2O/g for dry sample in 24 hat room temperature and is far larger than that of reported in the literature. Thevariables affecting the WA were investigated and optimized, they were: concentrations ofpotato starch, AM, CAN and bisAM were 26.3 g/L, 1.14 mol/L, 10.3 mmol/L and 0.53mmol/L, respectively. The amount of sodium hydroxide was 15 g and the temperatures ofgraft copolymerization and saponification reactions were 60℃ and 95℃. The time of graftcopolymerization and saponification reactions was 2 h, respectively. 相似文献
7.
Mingzhu Du Shuanghong Yang Tong Jiang Tingting Liang Ying Li Shuzhen Cai Qingping Wu Jumei Zhang Wei Chen Xinqiang Xie 《Molecules (Basel, Switzerland)》2022,27(14)
Expression and purification of β-galactosidases derived from Bifidobacterium provide a new resource for efficient lactose hydrolysis and lactose intolerance alleviation. Here, we cloned and expressed two β-galactosidases derived from Bifidobacterium. The optimal pH for BLGLB1 was 5.5, and the optimal temperature was 45 °C, at which the enzyme activity of BLGLB1 was higher than that of commercial enzyme E (300 ± 3.6 U/mg) under its optimal conditions, reaching 2200 ± 15 U/mg. The optimal pH and temperature for BPGLB1 were 6.0 and 45 °C, respectively, and the enzyme activity (0.58 ± 0.03 U/mg) under optimum conditions was significantly lower than that of BLGLB1. The structures of the two β-galactosidase were similar, with all known key sites conserved. When o-nitrophenyl-β-D-galactoside (oNPG) was used as an enzyme reaction substrate, the maximum reaction velocity (Vmax) for BLGLB1 and BPGLB1 was 3700 ± 100 U/mg and 1.1 ± 0.1 U/mg, respectively. The kinetic constant (Km) of BLGLB1 and BPGLB1 was 1.9 ± 0.1 and 1.3 ± 0.3 mmol/L, respectively. The respective catalytic constant (kcat) of BLGLB1 and BPGLB1 was 1700 ± 40 s−1 and 0.5 ± 0.02 s−1, respectively; the respective kcat/Km value of BLGLB1 and BPGLB1 was 870 L/(mmol∙s) and 0.36 L/(mmol∙s), respectively. The Km, kcat and Vmax values of BLGLB1 were superior to those of earlier reported β-galactosidase derived from Bifidobacterium. Overall, BLGLB1 has potential application in the food industry. 相似文献
8.
9.
Dr. Huizeng Li Wei Fang Zhipeng Zhao An Li Dr. Zheng Li Prof. Mingzhu Li Prof. Qunyang Li Prof. Xiqiao Feng Prof. Yanlin Song 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10622-10626
Precise separation and localization of microdroplets are fundamental for various fields, such as high-throughput screening, combinatorial chemistry, and the recognition of complex analytes. We have developed a droplet self-splitting strategy to divide an impacting droplet into predictable microdroplets and deposit them at preset spots for simultaneous multidetection. No matter exchange was observed between these microdroplets, so they could be manipulated independently. Droplet self-splitting was attributed to anisotropic liquid recoiling on the patterned adhesive surface, as influenced by the droplet Weber number and the width of the low-adhesive stripe. A quantitative criterion was also developed to judge the droplet self-splitting capability. The precise separation and distribution of microdroplets enabled simultaneous arrayed reactions and multiple analyte detection using one droplet of sample. 相似文献
10.
设计合成了一种新的具有D-π-A体系的有机分子:3-(4,5-二苄硫基-1,3-二硫杂环戊烯-2-亚基)萘吡喃酮,通过UV-vis,1H NMR,13C NMR,TOFMS和IR确定了其结构.初步研究了该化合物的电子光谱、荧光光谱和热稳定性.运用Gaussian 03量子化学程序包,采用密度泛函(DFT)B3PW91的方法优化了其基态几何结构,得到的几何参数与实验结果吻合得很好.研究结果表明,体系中存在着分子内的电荷转移,有较好的荧光性质,为寻找新的发光材料具有一定的实际意义. 相似文献