奎宁修饰的纳米铑簇合物催化丙酮酸乙酯对映选择性加氢反应研究

研究了奎宁作手性修饰剂修饰的负载型纳米铑簇合物催化剂 (Rh/ PVP-γ-Al2 O3)催化丙酮酸乙酯不对称氢化反应 ,在该反应中手性修饰剂奎宁不仅具有手性诱导作用 ,而且还有明显加速反应的作用 ;载体γ-Al2 O3在促进提高催化剂活性和对映选择性方面也有很重要的影响 .在优化的反应条件 [2 0℃ ,7.0 MPaH2 ,c(奎宁 ) =3 .86× 1 0 - 3mol/ L,四氢呋喃作溶剂 ]下 ,丙酮酸乙酯不对称加氢的转化频率 (TOF)为871 h- 1 ,对映选择性达到了 5 4.7% ;反应温度降低到 3℃时 ,对映选择性达到 5 9.2 % .     

奎宁修饰型Pt/Al2O3催化丙酮酸乙酯不对称加氢反应：乙酸溶剂与甲苯溶剂的比较

采用奎宁修饰型Pt/Al_2O_3作为加氢催化剂在常温常压下比较了乙酸和甲苯溶剂中丙酮酸乙酯的不对称加氢与一般的加氢反应的反应结果;研究了反应对映选择性与底物转化率的关系、丙酮酸乙酯用量对产物对映选择性的影响、三乙胺的作用以及乙酸-甲苯混合溶剂的使用. 实验结果表明, 乙酸作为反应溶剂的性能优于甲苯且溶剂化作用强于甲苯;两种溶剂中的不对称加氢反应均存在初始过渡期, 以乙酸为溶剂时, 催化反应速度较快;在乙酸溶剂中底物用量对产物对映纯度影响不大, 在甲苯溶剂中底物用量具有最佳值;在乙酸溶剂中加入三乙胺能显著提高反应的对映异构体选择性而在甲苯溶剂中则没有促进作用.     

L-氨基酸衍生物修饰的Ru/γ-Al_2O_3催化芳香酮不对称加氢研究

以系列L-氨基酸衍生物作为手性修饰剂,研究了三苯基膦(tpp)稳定的1.0%Ru/γ-Al2O3催化剂催化芳香酮多相不对称加氢,考察了稳定剂种类、修饰剂种类、金属负载量、底物浓度、温度、压力等因素对不对称加氢反应的影响。结果表明,L-氨基酸衍生物对1.0%Ru/γ-Al2O3/2tpp催化剂具有较好的修饰作用,在优化反应条件下芳香酮加氢反应的对映选择性达33%-81%,苯乙酮加氢反应的对映选择性可达70%。     

2-氧代-4-苯基丁酸乙酯不对称加氢反应的动力学和机理探讨

 采用 10,11-二氢辛可尼定修饰的Pt/γ-Al2O3 催化 2-氧代-4-苯基丁酸乙酯不对称加氢合成 (R)-2-羟基-4-苯基丁酸乙酯,考察了修饰剂用量、底物浓度、氢压和反应温度对加氢反应速率和光学选择性的影响. 结果表明,修饰剂用量和底物浓度在适中范围内对反应速率和光学选择性均较为有利;提高氢压和温度均能显著加快反应速率,但氢压对光学选择性影响不大,温度升高则不利于目标产物的生成. 根据反应动力学特征,认为修饰剂喹啉环平行吸附于Pt表面,被质子化后与以si面吸附在催化剂表面的底物作用,经过立体选择生成单一对映体. 用提出的反应机理推导出不对称加氢反应速率方程,可以较好地描述实验结果.     

金鸡纳碱衍生物和三苯基膦修饰的铱催化芳香酮不对称加氢反应

多相不对称催化反应因为它的应用前景而受到广泛关注,但由于在这类反应中催化剂和底物之间匹配的高度专一性,发掘新催化剂的难度等诸多因素极大地限制了多相不对称催化反应的开发.到目前为止,对于广泛关注的简单芳香酮的多相不对称加氢反应人们还无能为力.四川大学化学学院陈华等研究了以三苯基膦稳定地负载在Si02上的铱催化剂(3%Ir/SiOd2PPh3),在以金鸡纳碱衍生物为修饰剂催化简单芳香酮的不对称氢化反应中,在优化反应条件下,获得了高达96%ee的对映选择性.此工作为首例简单芳香酮经多相催化加氢获得高对映选择性的报道.为简单芳香酮的多相不对称氢化指出了新的方向.同时该工作也是首例以氢气为氢源、金属铱为催化剂的简单芳香酮高选择性不对称加氢的报道.     

离子液中金鸡纳碱稳定的Pt纳米粒子催化α-酮酸酯不对称加氢

在金鸡纳生物碱稳定剂存在下,通过简便的H_2还原PtO_2可以高效的在咪唑鎓盐离子液体中制备铂纳米颗粒(Pt NPs).TEM表明获得了平均粒径约1.78 nm且分散良好的Pt NPs.在金鸡纳生物碱的修饰下, Pt NPs催化剂在α-酮酸酯的不对称氢化中表现出优异的活性和对映选择性.在辛可尼定稳定和修饰作用下,丙酮酸乙酯催化不对称加氢TOF可达4640 h~(-1),α-酮酸酯的多相对映选择性氢化中ee值可达70.0%～80.1%.研究表明稳定剂和修饰剂手性中心、立体构型及空间位阻等特性协同影响不对称催化诱导能力.BMIMPF_6与乙酸的溶剂组合也是实现高活性及对映选择性的必要条件.催化剂可以重复使用多次,且活性和对映选择性没有明显降低.     

金鸡纳碱衍生物修饰的负载钌-铑双金属催化剂催化芳香酮不对称加氢

以金鸡纳碱衍生物作为手性修饰剂,研究了三苯基膦稳定的1.0%Ru+0.2%Rh/γ-Al2O3催化剂催化芳香酮多相不对称加氢,考察了修饰剂种类及浓度、碱添加剂种类及浓度、溶剂、氢气压力等因素对不对称加氢反应的影响.结果表明,金鸡纳碱衍生物对1.0%Ru+0.2%Rh/γ-Al2O3-tpp催化剂具有较好的修饰作用,在优化反应条件下苯乙酮加氢反应的对映选择性高达84%.     

Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by Cinchona-and PPh3-Modified RuRh/y-Al2O3

以金鸡纳碱衍生物作为手性修饰剂,研究了三苯基膦稳定的1.0%Ru＋0.2%Rh/γ-Al2O3催化剂催化芳香酮多相不对称加氢,考察了修饰剂种类及浓度、碱添加剂种类及浓度、溶剂、氢气压力等因素对不对称加氢反应的影响.结果表明,金鸡纳碱衍生物对1.0%Ru＋0.2%Rh/γ-Al2O3-tpp催化剂具有较好的修饰作用,在优化反应条件下苯乙酮加氢反应的对映选择性高达84%.     

金鸡纳碱衍生物修饰的负载钌催化剂催化芳香酮不对称加氢

以金鸡纳碱衍生物作为手性修饰剂,研究了三苯基膦(tpp)稳定的1.0%Ru/γ-Al2O3催化剂催化芳香酮多相不对称加氢,考察了稳定剂种类、修饰剂种类、金属负载量、溶剂、碱添加剂种类等因素对不对称加氢反应的影响.结果表明,金鸡纳碱衍生物对1.0%Ru/γ-Al2O3/2tpp催化剂具有较好的修饰作用,在优化的反应条件下苯乙酮及其衍生物加氢反应的对映选择性达78%～98%,2-乙酰基噻吩加氢反应的对映选择性可达80%,2-乙酰基呋喃加氢反应的对映选择性可达75%.     

辛可尼定修饰的铂纳米簇合物催化丙酮酸甲酯不对称加氢反应的研究

研究了辛可尼定(cinchonidine)作手性修饰剂修饰的氧化铝负载铂纳米簇合物(Pt-PVP-γ-Al2O3)催化丙酮酸甲酯不对称氢化反应,采用甲醇的碱溶液做溶剂,着重考察了低温条件下催化剂的活性和对映选择性的变化.优化的反应条件为0℃,5.0MPaH2,[cinchonidine]=3.24×10-3mol/L,[KOH]=0.02mol/L,1h内丙酮酸甲酯不对称加氢的转化率为32.2%,对映选择性达到52.2%;     

Synthesis and chiral micellization behavior of optically active amphiphilic diblock copolymer bearing quinine pendants

A novel optically active amphiphilic diblock copolymer bearing quinine pendants poly(ethylene oxide)‐b‐poly(glycidyl triazolyl‐L ‐quinine) (MPEO‐b‐PGTQ) was synthesized by “click” reaction of alkyne‐modified diblock copolymer poly(ethylene oxide)‐b‐poly(glycidyl propargyl ether) (MPEO‐b‐PGPE) and 9‐N₃‐quinine. The structure and composition of copolymers were characterized by gel permeation chromatography, ¹H nuclear magnetic resonance spectroscopy (¹H NMR), elemental analysis and optical rotation measurements, which showed that the synthetic route could provide the copolymer with well‐defined composition and with similar optical activity compared to its parent quinine. The micellization behavior of this chiral copolymer was investigated in different solvent systems. The results from fluorescence spectroscopy, UV spectroscopy, dynamic light scattering, transmission electron microscopy, ¹H NMR and circular dichroism (CD) spectroscopy indicated that the MPEO‐b‐PGTQ could form regular chiral spherical micelles in H₂O and Tetrahydrofuran‐H₂O (10:90, V/V) systems, and the state of aggregated chiral micelles depended on the nature of the medium. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3640–3650, 2009     

Chemoselective Vinylation of the Quinine Hydroxy Group with the System Electron-Deficient Acetylene/Diphenylphosphine Oxide: an Alternative to SNHAr Reaction

Russian Journal of Organic Chemistry - Three-component SNHAr reaction of quinine, diphenylphosphine oxide, and furoylacetylene chemoselectively afforded the corresponding quinine vinyl ether and 2:...     

On‐line coupled capillary isotachophoresis‐capillary zone electrophoresis in hydrodynamically closed separation system hyphenated with laser induced fluorescence detection

An analytical method, based on a column coupling capillary ITP and CZE in a hydrodynamically closed separation mode hyphenated with the detection in the modular arrangement, was developed in this work. Analytical possibilities of this approach are demonstrated on the direct and ultrasensitive quantitative determination of quinine (QUI) in diluted real multicomponent ionic matrices (beverages, urine). The detection cell interface, with the rectangular arrangement of the optical channels inside, connected the separation capillary with the LIF detector via optical fibers in the on‐column detection arrangement. ITP enabled the direct large volume (30 μL) injections of the diluted real matrices with an on‐line sample pretreatment (preseparation, preconcentration) so that no external sample preparation (except for the dilution) was necessary for the separation of the analyte in the multicomponent ionic matrices. Due to the ITP sample preconcentration and intrinsic sensitivity of the LIF detection, very low concentration LOD (as low as 77 pg/mL), were reached at the same time. This was ca. two orders lower than the corresponding LOD achieved by the same 2D separation system with UV absorbance detection. Compared to the single column CE‐LIF methods applied for this model analyte and matrix, this method was found to be superior in terms of concentration LOD, with acceptable selectivity and benefits of the on‐line sample preparation. A food control and bioanalytical application clearly illustrates great practical possibilities and routine use of the proposed modular ITP–CZE–LIF technique.     

Increasing Hybridization Rate and Sensitivity of Bead‐Based Assays Using Isotachophoresis

We present an electrokinetic technique to increase the reaction rate and sensitivity of bead‐based assays. We use isotachophoresis (ITP) to preconcentrate and co‐focus target molecules and beads into a single ITP zone. The process achieves rapid mixing, stirring, and strongly increases the binding reaction rate. We demonstrate our assay with quantitative detection of 24 nt single‐stranded DNA over a dynamic range of three orders of magnitude and multiplexed detection of ten target species per sample. We show that ITP can achieve approximately the same sensitivity as a well‐stirred standard reaction in 60‐fold reduced reaction time (20 min versus 20 h). Alternately, compared to standard reaction times of 30 min, we show that 20 min ITP hybridization can achieve 5.3‐fold higher sensitivity.     

Preconcentration and detection of the phosphorylated forms of cardiac troponin I in a cascade microchip by cationic isotachophoresis

This paper describes the detection of a cardiac biomarker, cardiac troponin I (cTnI), spiked into depleted human serum using cationic isotachophoresis (ITP) in a 3.9 cm long poly(methyl methacrylate) (PMMA) microfluidic channel. The microfluidic chip incorporates a 100× cross-sectional area reduction, including a 10× depth reduction and a 10× width reduction, to increase sensitivity during ITP. The cross-sectional area reductions in combination with ITP allowed visualization of lower concentrations of fluorescently labeled cTnI. ITP was performed in both "peak mode" and "plateau mode" and the final concentrations obtained were linear with initial cTnI concentration. We were able to detect and quantify cTnI at initial concentrations as low as 46 ng mL(-1) in the presence of human serum proteins and obtain cTnI concentrations factors as high as ~ 9000. In addition, preliminary ITP experiments including both labeled cTnI and labeled protein kinase A (PKA) phosphorylated cTnI were performed to visualize ITP migration of different phosphorylated forms of cTnI. The different phosphorylated states of cTnI formed distinct ITP zones between the leading and terminating electrolytes. To our knowledge, this is the first attempt at using ITP in a cascade microchip to quantify cTnI in human serum and detect different phosphorylated forms.     

Formation of a Criegee intermediate in the low-temperature oxidation of dimethyl sulfoxide

Dimethyl sulfoxide (DMSO) is the major sulfur-containing constituent of the Marine Boundary Layer. It is a significant source of H2SO4 aerosol/particles and methane sulfonic acid via atmospheric oxidation processes, where the mechanism is not established. In this study, several new, low-temperature pathways are revealed in the oxidation of DMSO using CBS-QB3 and G3MP2 multilevel and B3LYP hybrid density functional quantum chemical methods. Unlike analogous hydrocarbon peroxy radicals the chemically activated DMSO peroxy radical, [CH3S(=O)CH2OO*]*, predominantly undergoes simple dissociation to a methylsulfinyl radical CH3S*(=O) and a Criegee intermediate, CH2OO, with the barrier to dissociation 11.3 kcal mol(-1) below the energy of the CH3S(=O)CH2* + O2 reactants. The well depth for addition of O2 to the CH3S(=O)CH2 precursor radical is 29.6 kcal mol(-1) at the CBS-QB3 level of theory. We believe that this reaction may serve an important role in atmospheric photochemical and irradiated biological (oxygen-rich) media where formation of initial radicals is facilitated even at lower temperatures. The Criegee intermediate (carbonyl oxide, peroxymethylene) and sulfinyl radical can further decompose, resulting in additional chain branching. A second reaction channel important for oxidation processes includes formation (via intramolecular H atom transfer) and further decomposition of hydroperoxide methylsulfoxide radical, *CH2S(=O)CH2OOH over a low barrier of activation. The initial H-transfer reaction is similar and common in analogous hydrocarbon radical + O2 reactions; but the subsequent very low (3-6 kcal mol(-1)) barrier (14 kcal mol(-1) below the initial reagents) to beta-scission products is not common in HC systems. The low energy reaction of the hydroperoxide radical is a beta-scission elimination of *CH2S(=O)CH2OOH into the CH2=S=O + CH2O + *OH product set. This beta-scission barrier is low, because of the delocalization of the *CH2 radical center through the -S(=O) group, to the -CH2OOH fragment in the transition state structure. The hydroperoxide methylsulfoxide radical can also decompose via a second reaction channel of intramolecular OH migration, yielding formaldehyde and a sulfur-centered hydroxymethylsulfinyl radical HOCH2S*(=O). The barrier of activation relative to initial reagents is 4.2 kcal mol(-1). Heats of formation for DMSO, DMSO carbon-centered radical and Criegee intermediate are evaluated at 298 K as -35.97 +/- 0.05, 13.0 +/- 0.2 and 25.3 +/- 0.7 kcal mol(-1) respectively using isodesmic reaction analysis. The [CH3S*(=O) + CH2OO] product set is shown to form a van der Waals complex that results in O-atom transfer reaction and the formation of new products CH3SO2* radical and CH2O. Proper orientation of the Criegee intermediate and methylsulfinyl radical, as a pre-stabilized pre-reaction complex, assist the process. The DMSO radical reaction is also compared to that of acetonyl radical.     

In Process Citation

Oxidation of 6-methoxyquinoline with vanadate shows the possibility of initial complex formation between the dioxovanadium(V) ion VO⁺₂ and the ethereal oxygen atom. The opening of the homocycle yields mainly 2-pyridone-3-carboxylic acid. In the case of quinine or mefloquine, the VO⁺₂ ion preferentially forms a pentagonal chelate with the secondary alcohol function. Oxidation of this complex initially produces quinoline-4-carboxylic acids. The acid that results from mefloquine is stable in the reaction solution and this property allows a reproducible consumption of reagent and a quantitative determination of this new antimalarial drug.     

Reactive scattering of a neon seeded oxygen atom beam

A high pressure microwave discharge source operating with a dilute mixture of O₂ in Ne has been used to produce a supersonic nozzle beam of O atoms seeded in Ne. This low energy supersonic O atom beam has been used to study the reactive scattering of O atoms with Cl₂ and CS₂ molecules at an initial translational energy E = 13 kJ mol^?1. The results are compared with rective scattering from the same reactions using a high energy O atom beam formed by seeding O atoms in He. The O + Cl₂ reaction proceeds via a short-lived collision complex where the lifetime of the collision complex depends upon the initial translational energy. However the O + CS₂ reaction follows a stripping mechanism which is unaffected by initial translational energy.     

Photoreactions of quinine in aqueous citric acid solution. part 2, some end-products

A novel spiro-compound derived from 2',4'-b1s-(1,3-dicarboxy-2-hydroxyprop-2-y1) -1',4'-dihydroquinine has been identified as a major end-product of the irradiation of quinine in aqueous citric acid solution. 7'-(1,3-Dicarboxy-2-hydroxyprop-2-yl)deoxyquinine and products arising from the cleavage of quinine at C-9 were also detected in the reaction mixture.     

葡萄糖还原氢氧化铜制备球形氧化亚铜及其粒度控制研究

以Cu(OH)2为前躯体,用葡萄糖还原制备了不同粒径的单分散球形氧化亚铜粉末。利用扫描电镜和smileview软件对Cu2O粉末进行了表征分析,并通过上述分析考察了反应温度和反应物浓度等因素对Cu2O粉末粒径的影响。结果表明,随着反应温度与葡萄糖投加浓度的提高,颗粒粒径减小;而随着氢氧化钠投加浓度的提高,颗粒粒径增大;体系内最终颗粒密度n+∞或颗粒个数n与各影响因素的变化呈直线关系。最后根据晶体成核生长模型初步分析了反应条件对Cu2O颗粒粒径的影响机理。