Catalyzation of 1,4-additions of arylboronic acids to α,β-unsaturated substrates using nickel(I) complexes

Nickel(I) complexes were generated in situ from Ni (PPh₃)₂Cl₂ using activated iron and the complexes combined with N,N′-bis(4-fluorobenzylidene) ethane-1,2-diamine (BFBED) were then used as a catalyst for the 1,4-addition reaction of arylboronic acids to α,β-unsaturated substrates. The reaction proceeded to completion and did not require the addition of a base but the addition of potassium iodide is crucial to this cross-coupling reaction. Moreover, experimental observations suggested a possible Ni(I)–Ni(III) catalytic cycle mechanism.     

Synthesis of 1,6-dihydropyrimidines via copper-catalyzed multistep cascade reactions between O-propargylic aldoximes and isocyanates

Multi-step cascade reactions of O-propargylic oximes with isocyanates were carried out in the presence of copper catalysts to afford the corresponding 1,6-dihydropyrimidines in good yields. The multi-step reactions consisted of a 2,3-rearrangement, a [3+2] cycloaddition, decarboxylative ring opening involving a 1,4-hydrogen shift, and a 6π-electrocyclization.     

Valence state parameters of all transition metal atoms in metalloproteins—development of ABEEMσπ fluctuating charge force field

To promote accuracy of the atom‐bond electronegativity equalization method (ABEEMσπ) fluctuating charge polarizable force fields, and extend it to include all transition metal atoms, a new parameter, the reference charge is set up in the expression of the total energy potential function. We select over 700 model molecules most of which model metalloprotein molecules that come from Protein Data Bank. We set reference charges for different apparent valence states of transition metals and calibrate the parameters of reference charges, valence state electronegativities, and valence state hardnesses for ABEEMσπ through linear regression and least square method. These parameters can be used to calculate charge distributions of metalloproteins containing transition metal atoms (Sc‐Zn, Y‐Cd, and Lu‐Hg). Compared the results of ABEEMσπ charge distributions with those obtained by ab initio method, the quite good linear correlations of the two kinds of charge distributions are shown. The reason why the STO‐3G basis set in Mulliken population analysis for the parameter calibration is specially explained in detail. Furthermore, ABEEMσπ method can also quickly and quite accurately calculate dipole moments of molecules. Molecular dynamics optimizations of five metalloproteins as the examples show that their structures obtained by ABEEMσπ fluctuating charge polarizable force field are very close to the structures optimized by the ab initio MP2/6–311G method. This means that the ABEEMσπ/MM can now be applied to molecular dynamics simulations of systems that contain metalloproteins with good accuracy. © 2014 Wiley Periodicals, Inc.     

Effect of HAP on Stability and Plugging Property of LPFR Dispersion

To improve the stability and plugging property of low-solubility phenol formaldehyde resin (LPFR) in the injection water from Daqing Oilfield, hydrophobically associating polymers (HAP) as a stabilizing agent were used. The size and zeta potential of LPFR, LPFR/HAP molecule aggregates, and turbidity and plugging properties of LPFR dispersions were measured in deionized water, simulation water, and injection water, respectively. The results show that the hydrophobic grouping on the HAP molecule has a similar molecular structure as LPFR, and HAP and LPFR can form complex molecule aggregates in the injection water. The zeta potential of LPFR/HAP molecule aggregates is larger than that of LPFR molecule aggregates. Therefore, the repulsive force operating between LPFR/HAP complex molecule aggregates is increased. HAP enhances the stability of LPFR in the injection water and plugging property of LPFR dispersion in porous medium.     

Cloud point extraction and simultaneous spectrophotometric determination of V(V), Co(II) and Cu(II) ions in water samples by 5-Br-PADAP using partial least squares regression

In this work, a new method has been proposed to simultaneously determine V(V), Co(II) and Cu(II) ions from aqueous solution by spectrophotometry after cloud point extraction using partial least squares regression (PLS). The metal ions in 10 ml of aqueous solution (containing 0.2 M sodium acetate buffer solution, pH 3.5) were formed complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Then, Triton X-114 (2 %, v/v) was added to the solution. By increasing the temperature of the solution up to 55 °C, a phase separation occurred. After centrifugation at 3,000 rpm for 10 min, the surfactant-rich phase was dissolved and diluted to 0.5 mL with ethanol. The metal ions were then determined using spectrophotometry. At these optimal extraction and operating conditions, linearity was obeyed in the range 7–300, 3–100 and 15–700 ng mL^?1 of V(V), Co(II) and Cu(II), with the detection limit of 2.2, 1.0 and 4.5 ng mL^?1, respectively. The relative predictive error for the simultaneous determination of 15 test samples of different concentrations of V(V), Co(II) and Cu(II) was 3.28, 3.64 and 4.04 %, respectively. The root mean square error of prediction for applying the PLS method to 15 synthetic samples in the linear ranges of these metal ions was 3.4, 1.6 and 18.1 ng mL^?1. The interference effect of some anions and cations was also tested. The proposed method has been applied successfully to the simultaneous determination of V(V), Co(II) and Cu(II) ions in real matrix samples with the recoveries of 96.75–104.80 %.     

Radiosynthesis of 10-(2-[18F]fluoroethoxy)-20(S)-camptothecin as a potential positron emission tomography tracer for the imaging of topoisomerase I in cancers

The preparation of 10-(2-[¹⁸F]fluoroethoxy)-20(S)-camptothecin, a potential positron emission tomography tracer for the imaging of topoisomerase I in cancers, is described. 10-(2-[¹⁸F]Fluoroethoxy)-20(S)-camptothecin was synthesized by the [¹⁸F]fluoroalkylation of the corresponding hydroxy precursor molecule with 2-[¹⁸F]fluoroethyl bromide ([¹⁸F]FEtBr) in dimethylsulfoxide (DMSO) at 55 °C for 20 min; this was followed by purification using high performance liquid chromatography (HPLC) with a total preparation time of 60 min. The overall radiochemical yield was approximately 5.4–12 % (uncorrected), and the radiochemical purity was above 96 %.     

采用反应挤出三次加料法合成苯乙烯/异戊二烯/苯乙烯

以同向啮合双螺杆挤出机为反应器,采用苯乙烯和异戊二烯为聚合单体,以正丁基锂为引发剂,采用三次加料法合成苯乙烯/异戊二烯/苯乙烯(SIS)三嵌段热塑性弹性体.氢核磁共振(1H NMR)谱分析结果表明,共聚物中聚异戊二烯嵌段以1,4-结构为主.采用四氧化锇催化双氧水氧化降解聚合物分子链,利用凝胶渗透色谱对氧化降解后的聚苯乙烯碎片进行分析,证明共聚物分子为(聚苯乙烯-聚异戊二烯-聚苯乙烯)(PS-PI-PS)三嵌段结构.动态力学分析(DMA)及透射电子显微镜(TEM)分析结果表明,SIS具有两相分离结构.拉伸试验结果表明,共聚物拉伸强度与苯乙烯含量有关.     

增压O_2/CO_2气氛下煤燃烧特性实验研究

增压O2/CO2燃烧是一种可高效分离回收CO2的新兴燃烧技术,其燃烧机理与常压空气、常压O2/CO2燃烧存在较大差异。在加压热重分析仪上研究了增压条件下总压、氧浓度、气氛及粒径等反应参数对美国烟煤和淮北无烟煤燃烧特性的影响,确定了煤的着火温度,并对其进行燃烧动力学分析。结果表明,增压O2/CO2气氛下,随着压力或氧浓度的增加,DTG曲线向低温区移动,煤样整体燃烧速率加快。压力提升、氧浓度增加及煤粉细化均可改善O2/CO2气氛下煤样的着火特性。常压O2/CO2气氛下煤粉燃烧基本属于一级反应;增压O2/CO2气氛下,低温区属于0.5级反应,而高温区属于1.5级反应。     

基于柱[n]芳烃(准)轮烷的研究进展

柱芳烃作为一类新型的大环主体分子,自2008年首次报道以来,引起了人们,特别是化学家的广泛关注.目前,它已在分子识别、(准)轮烷、超分子聚合物、分子弹簧、智能跨膜离子通道、囊泡、金属有机骨架结构等众多研究领域作为重要模块得到初步的应用.主要将以柱芳烃作为主体大环分子来构筑(准)轮烷的研究进展进行简要的综述,同时还介绍了基于柱芳烃的(准)聚轮烷的研究概况,并对未来的发展作了进一步展望.     

Cu催化的单电子转移活性自由基聚合制备石墨烯/聚N,N-二甲基丙烯酰胺复合体系

以天然石墨为起始原料,采用改进的Hummer方法,通过强酸氧化水解和超声分散制备了氧化石墨烯,然后通过肼还原和重氮化反应得到含有羟基的石墨烯(G-OH),再通过酯化反应在石墨烯表面上引入了α-氯代羰基,从而得到了含有单电子转移活性自由基聚合(SET-LRP)引发基团的石墨烯(G-Cl).最后,在石墨烯表面原位引发N,N-二甲基丙烯酰胺(DMAA)单体的SET-LRP聚合,得到了G-PDMAA复合材料,G-PDMAA在常规的有机溶剂和水中具有良好的分散性.