Pt-Catalyzed sp C-H bond activation of o-alkyl substituted aromatic carboxylic acid derivatives for the formation of aryl lactones

Synthesis of aryl lactones from ortho-alkyl substituted aromatic carboxylic acids is described on the basis of sp³ C-H bond activation using either palladium or platinum catalysts. Kinetic isotope studies reveal that the reaction takes place presumably by the chelation assistance of metal catalyst to the carboxylic group followed by the C-H bond activation.     

The Ephemeral 10β-OH Trifluoromethanesulfonates of 7-Epi Paclitaxel Analogs─A New Example for Anchimeric Assistance

Paclitaxelffexol@)la.aneffectiveanhcanceragentoriginallyisolatedfromthebarkofPacthcyewTaxusbrevghlia,'hasbeenextensivelystUdiedduetoitspiquemechbosmofactionandcomplexityofitschemicalsboctllfe.DifferentoxygenatCdgroupsinthiscomplexmoleculeprovideatafgetforthechemisttoexplorestereoselectivereactions.Numerousmodificationsonthismoleculeandrelatedtaxoidswereexemplifiedbyhydrolysis,'deoxygenatioll,'substitution,#elindnatioll,'oxidahon,'reducholl,'cleavage,'andrearrangement.'Manyreactionsinvolveanc…     

Mechanistic insights into phospha–Michael reaction of tertiary phosphines with electron-deficient alkenes

ABSTRACT

The Michael-type addition of tertiary phosphines to electron-deficient alkenes is a convenient way to generate reactive phosphonium zwitterionic intermediates, which participate readily in many synthetically useful transformations. Although the synthetic usefulness of the phospha–Michael addition has been largely demonstrated, knowledge on the kinetics and mechanism of this reaction is sparse. This paper briefly summarizes the contribution of our research group to find out the mechanism of this reaction.     

Silicon- and germanium-substituted propynals as ambident electrophiles for the design of new heterocycles and polyfunctional acetylenes

Research results on the reactivity of silicon- and germanium-substituted propynals as ambident electrophiles in the reactions with mono- and binucleophiles were summarized. Chemo- and regioselectivity of the nucleophilic addition and cycloaddition depending on the structure of propynals, the nature of a reagent, catalyst, and the reaction conditions was studied. Wide synthetic potentialities of substituted propynals in the synthesis of new heterocyclic systems and polyfunctional acetylenes were demonstrated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–930, May, 2008.     

超声辅助制备表面修饰纳米Ca2B6O11及表征

纳米材料的制备及其应用于润滑油摩擦性能研究,对于改善油品的性能和延长设备的使用寿命具有重要的意义。首次采用超声辅助法合成了球型、粒径分布均匀的纳米硼酸钙润滑油添加剂并对其进行了表征。XRD结合热分析发现样品在室温下为非晶态,750℃结晶,且原料配比对晶态没有影响。SEM和TEM分析证明在超声波辅助下可以得到50 nm的超微粒子,而不用超声波的样品粒径为200~300 nm。在超声和搅拌下将2%的添加剂均匀分散在润滑油中,得到成品油。静置观察评价了润滑油的分散性和稳定性。在重负荷车辆与工业齿轮油中试验检验了润滑油的的润滑性能。结果表明,纳米硼酸钙添加剂具有良好的分散性、稳定性和抗磨减摩性能。     

一种新型球形聚丙烯腈螯合吸附剂的制备及性能

以腈纶废丝为原料,通过相转换法制得聚丙烯腈珠体,通过皂化和微波辐射下的偕胺肟化改性,制得一种新型球形聚丙烯腈螯合吸附剂SPHA,并对SPHA进行理化性能表征。研究表明,SPHA含有羧基和偕胺肟基等多种特征官能团,改性的最佳条件为：无水碳酸钠与盐酸羟胺的摩尔比0.01∶1,浴比20∶1,盐酸羟胺和Na OH的浓度分别为2.5 mol/L和1.5 mol/L,皂化时间10 min,微波功率240 W,辐射时间2 min,此时制得的SPHA对Cr（Ⅵ）的去除率最高。采用静态吸附法研究SPHA对Cr（Ⅵ）的吸附效果,当p H值为2,Cr（Ⅵ）的初始质量浓度为100 mg/L,吸附时间为120 min,吸附温度为30℃时,去除率可达99.8%,平衡吸附容量为33.3 mg/g。     

Development of a Sensitive Methodology for the Analysis of Chlorobenzenes in Water Samples by Combination of Homogeneous Liquid‐liquid Microextraction via Flotation Assistance and Gas Chromatography‐flame Ionization Detection

In this study, a simple, rapid and efficient method, homogeneous liquid‐liquid microextraction via flotation assistance (HLLME‐FA) combined with gas chromatography – flame ionization detection (GC‐FID), for the determination of chlorobenzenes (CBs) in water samples, has been described. In this research, a special extraction cell was designed to facilitate collection of the low‐density solvent extraction. No centrifugation was required in this procedure. The water sample solution was added into the extraction cell which contained an appropriate mixture of extraction and homogeneous solvents. By using air flotation, the organic solvent was collected at the conical part of the designed cell. Parameters affecting extraction efficiency were investigated and optimized. Under the optimum conditions, the detection limits, the precisions and the linearity of the method were found in the range of 0.2 to 1.5 µg L^‐1, 5.7–9.3% (RSD, n =5) and 0.5–200 µg L^‐1, respectively.     

Nonsingularity of some classes of matrices, and minimal solutions of Silverman''s game on discrete sets

We establish the irreducibility of each game in four infinite three-parameter families of even order Silverman games, and the major step in doing so is to prove that certain matrices A, related in a simple way to the payoff matrices, are nonsingular for all relevant values of the parameters. This nonsingularity is established by, in effect, producing a matrix D such that AD is known to be nonsingular. The elements of D are polynomials from six interrelated sequences of polynomials closely related to the Chebyshev polynomials of the second kind. Each of these sequences satisfies a second order recursion, and consequently has many Fibonacci-like properties, which play an essential role in proving that the product AD is what we claim it is. The matrices D were found experimentally, by discovering patterns in low order cases worked out with the help of some computer algebra systems. The corresponding results for four families of odd order games were reported in an earlier paper.