可重复使用CuO纳米粒子催化微波辅助的腈和NaN3环加成反应 合成5-取代1H-四唑类

将可重复使用的CuO纳米粒子成功用于催化微波辅助的腈和NaN3[3+2]环加成反应高效合成5-取代1H-四唑类化合物.该法突出特点为成本低、合成快、稳定性高、可重复使用、反应条件温和、无需任何添加物、官能团兼容性好和产率高.这种环境友好的微波辅助纳米粒子催化合成策略可望替代现有的涉及常规路易斯酸催化剂方法,以及作为一种简易的合成特殊化合物的方法.     

Vanadium–Manganese Redox Flow Battery: Study of MnIII Disproportionation in the Presence of Other Metallic Ions

The Mn^III/Mn^II redox couple with a standard potential of +1.51 V versus the standard hydrogen electrode (SHE) has attracted interest for the design of V/Mn redox flow batteries (RFBs). However, Mn^III disproportionation leads to a loss of capacity, an increase in pressure drop, and electrode passivation caused by the formation of MnO₂ particles during battery cycling. In this work, the influence of Ti^IV or/and V^V on Mn^III stability in acidic conditions is studied by formulating four different electrolytes in equimolar ratios (Mn, Mn/Ti, Mn/V, Mn/V/Ti). Voltammetry studies have revealed an EC_i process for Mn^II oxidation responsible for the electrode passivation. SEM and XPS analysis demonstrate that the nature and morphology of the passivating oxides layer depend strongly on the electrolyte composition. Spectroelectrochemistry highlights the stabilization effect of Ti^IV and V^V on Mn^III. At a comparable pH, the amount of Mn^III loss through disproportionation is decreased by a factor of 2.5 in the presence of Ti^IV or/and V^V. Therefore, V^V is an efficient substitute for Ti^IV to stabilize the Mn^III electrolyte for RFB applications.     

Real‐time monitoring of active ingredient dispersion in a pharmaceutical aqueous suspension using Raman spectroscopy

In a typical aqueous nasal suspension manufacturing process, the homogeneity of the active pharmaceutical ingredient (API) dispersion in a premix vessel is determined merely by visual observation. In this study, to better demonstrate in‐process control, Raman spectroscopy was developed as a process analytical tool (PAT) to monitor the real‐time API dispersion homogeneity in the active premix process. The end‐point variations of the API dispersion as a function of the surfactant type, surfactant concentration, and agitation speed were evaluated by dispersive Raman spectroscopy in combination with multivariate analysis for both lab‐scale and pilot‐scale batches. The optimal surfactant concentration and type were determined to be 0.2% surfactant A for the active dispersion based on a quantitative end‐point comparison. In addition, a chemometric model was developed successfully for the real‐time prediction of API concentration in the active premix, with a root mean squared error of prediction (RMSEP) of 5.4%. In conclusion, Raman spectroscopy has proven to be a viable PAT tool to qualitatively and quantitatively assess the active premix homogeneity in an aqueous nasal suspension manufacturing process. In the future, this method can potentially be used in the commercial manufacturing process for in‐process control of the dispersion homogeneity of the suspension. Copyright © 2011 John Wiley & Sons, Ltd.     

Simultaneous determination of 2‐arachidonoylglycerol, 1‐arachidonoylglycerol and arachidonic acid in mouse brain tissue using liquid chromatography/tandem mass spectrometry

Endocannabinoids (ECs), such as anandamide (AEA) and 2‐arachidonoylglycerol (2‐AG), modulate a number of physiological processes, including pain, appetite and emotional state. Levels of ECs are tightly controlled by enzymatic biosynthesis and degradation in vivo. However, there is limited knowledge about the enzymes that terminate signaling of the major brain EC, 2‐AG. Identification and quantification of 2‐AG, 1‐AG and arachidonic acid (AA) is important for studying the enzymatic hydrolysis of 2‐AG. We have developed a sensitive and specific quantification method for simultaneous determination of 2‐AG, 1‐AG and AA from mouse brain and adipose tissues by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using a simple brain sample preparation method. The separations were carried out based on reversed phase chromatography. Optimization of electrospray ionization conditions established the limits of detection (S/N = 3) at 50, 25 and 65 fmol for 2‐AG, 1‐AG and AA, respectively. The methods were selective, precise (%R.S.D. < 10%) and sensitive over a range of 0.02–20, 0.01–10 and 0.05–50 ng/mg tissue for 2‐AG, 1‐AG and AA, respectively. The quantification method was validated with consideration of the matrix effects and the mass spectrometry (MS) responses of the analytes and the deuterium labeled internal standard (IS). The developed methods were applied to study the hydrolysis of 2‐AG from mouse brain extracts containing membrane bound monoacylglycerol lipase (MAGL), and to measure the basal levels of 2‐AG, 1‐AG and AA in mouse brain and adipose tissues. Copyright © 2009 John Wiley & Sons, Ltd.     

Stability analysis of a thin-walled cylinder in turning operation using the semi-discretization method

In this work, the stability of a flexible thin cylindrical workpiece in turning is analyzed. A process model is derived based on a finite element representation of the workpiece flexibility and a nonlinear cutting force law. Repeated cutting of the same surface due to overlapping cuts is modeled with the help of a time delay. The stability of the so obtained system of periodic delay differential equations is then determined using an approximation as a time-discrete system and Floquet theory. The time-discrete system is obtained using the semi-discretization method. The method is implemented to analyze the stability of two different workpiece models of different thicknesses for different tool positions with respect to the jaw end. It is shown that the stability chart depends on the tool position as well as on the thickness.     

Overriding effect of temperature over reagent and substrate size for boron-mediated aldol reaction of methyl phenylacetate

The enolization temperature overrides all other aspects, including the sterics of the alkyl group of the boron reagent and the alkoxy group of the ester during the enolboration–aldolization of phenylacetates. This study has led to the first n-Bu₂BOTf-mediated anti-selective aldol reaction of an ester.     

Fluorescence Properties of Donor Acceptor Chromophores on Newly Synthesized Pyridine-3-Carbonitriles

A convenient route was successfully developed for the synthesis of novel heterocycles such as pyridine-3-carbonitriles 4 from chalcone 3 in good yields. The pyridine-3-carbonitrile derivatives synthesized were further studied for their photophysical properties and observed that absorption and emission was changed, due to the chromospheres at C₄-position in phenyl ring and C₂-position in pyridine-3-carbonitrile derivatives.     

Bromamine-T mediated aziridination of olefins with a new polymer supported Manganese(II) complex as catalyst

Chloromethylated styrene-divinyl benzene of 8% cross-link was functionalized using o-phenylene diamine and finally it was treated with Mn(II) for the formation of metal complex on the surface. The metal content was estimated using atomic absorption spectroscopy. The thermal stability of the catalyst was seen by the use of DTA-TG analyses and the catalyst was found to be stable up to ˜125°C. The modern spectroscopic methods such as FT-IR, ESR were used in order to confirm the probable structure of the catalyst. The catalytic activity of this supported Mn(II)-complex was investigated for aziridination of olefins with bromamine-T as the source of nitrogen. The catalyst was found to be effective in this reaction and could be reused with no substantial loss of activity for up to three cycles.     

Aerobic ligand-free Suzuki coupling catalyzed by in situ-generated palladium nanoparticles in water

A simple and efficient procedure for Suzuki coupling of aryl bromides/iodides with aryl- and alkylboronic acids catalyzed by in situ-generated palladium(0) nanoparticles in water without any ligand in open air to produce a variety of functionalized biaryls and alkyl-aryls has been developed. The boronic acids act here as the reducing agent for the formation of Pd nanoparticles. The reactions are remarkably fast (5 min) and high yielding. The catalyst is recyclable up to three runs without loss of efficiency.