A green protocol for chemoselective O-acylation in the presence of zinc oxide as a heterogeneous, reusable and eco-friendly catalyst

The solvent-free acylation of alcohols and phenols with acyl chlorides using ZnO as a catalyst is described. The remarkable selectivity under mild and neutral conditions, and recyclability of the catalyst, are advantages.     

An NMR study of the decomposition of a 2,2-disubstituted thiazolidine. Kinetic evidence for a schiff base intermediate

The pH-rate profile for the decomposition of 2,2,5,5-tetramethyl-4-thiazolidinecarboxylic acid is used to identify the presence of a Schiff base intermediate. Activation parameters for the reaction are reported at various pH's and in particular the negative values of entropy support the presence of a carbinolamine in the rate-determining step.     

Synthesis of trans-(3S,4S)-dibenzyloxycyclopentanone

The 1-cyano-1-thiophenylcyclopentone derivative $\text{1}$, obtained from (R,R)-(+)-tartaric acid, has been converted into a number of derivatives including the important $\text{trans}$-(3S,4S)-dibenzyloxycyclopentanone $\text{2}$ in 45% overall yield.     

高效和可重复使用的Zr-MCM-41催化剂催化Strecker反应合成氨基腈类化合物(英文)

The synthesis and characterization of Zr-MCM-41 nanoreactors and their catalytic activity in the synthesis of new amino nitrile derivatives by the Strecker reaction in high yields and in short reaction times is reported.     

Catalytic oxidation of urazoles and bis-urazoles to their corresponding triazolinediones using aluminium nitrate and a catalytic amount of silica sulfuric acid

Abstract  

A simple and efficient catalytic oxidation of urazoles and a bis-urazole to the corresponding triazolinediones by treatment with Al(NO₃)₃.9H₂O in the presence of a catalytic amount of silica sulfuric acid is described. A good range of urazole derivatives was selectively oxidized in CH₂Cl₂ at room temperature in good to excellent yields.     

H2SO4/Silicagel: Highly Efficient Catalyst for the Synthesis of α-Aminonitriles Using Trimethysilyl Cyanide

Summary. The multicomponent Strecker reaction using trimethylsilyl cyanide was performed at room temperature and α-aminonitriles were prepared in excellent yields in the presence of a catalytic amount of H₂SO₄ adsorbed on silica gel.     

Interaction of dimethyltin(IV) dichloride with 5′‐IMP and 5′‐UMP

The formation constants of the species formed in the systems H⁺ + dimethyltin(IV) + 5′‐IMP and 5′‐UMP, H⁺ + 5′‐IMP and H⁺ + 5′‐UMP have been determined in aqueous solution in the pH range 1.5–9.5 at constant temperature (25 °C) and constant ionic strength (0.1 mol dm⁻³ NaClO₄), using spectrophotometric and potentiometric techniques. ¹H and ³¹P NMR investigations in aqueous solution confirmed the species formation. The precipitated complexes of IMP and UMP by Me₂Sn(IV)²⁺ at low pH values were characterized by elemental analysis and FTIR spectroscopy methods, the bonding sites of the ligands were determined and ruled out purine and pyrimidine moieties (N‐7 and N‐1 in IMP and N‐3 in UMP, respectively) while a bidentated coordination of the phosphate group is concluded in both cases. Finally, the experiments revealed the existence of complexes with trigonal bipyramidal structures that is in agreement with similar systems resulted previously. Copyright © 2008 John Wiley & Sons, Ltd.     

Droplet retraction in the presence of nanoparticles with different surface modifications

We studied the influence of nanoparticles with different surface modifications on the interfacial tension and relaxation of model polymer blend after cessation of different strains. The droplet retraction experiments were carried out on a model system composed of polydimethylsiloxane (PDMS) as the suspending fluid and polyisobutylene (PIB) as droplet at room temperature in the presence of hydrophobic and hydrophilic nanosilica. Different weight fractions of particles were dispersed in the PIB droplet before forming a dispersed droplet by using a microsyringe in shear cell. We found that applied strain, nanoparticle concentration and their thermodynamically preferred localization affect both nominal interfacial tension and droplet retraction process. By addition of nanoparticles at a concentration as low as 0.2%wt, the nominal interfacial tension decreases from 3.12?±?0.15 mN/m for neat PIB-PDMS interface depending on the surface characteristics of nanosilica. Hydrophilic nanosilica has the most effect on nominal interfacial tension and decreases it as low as 0.2?±?0.21 mN/m at 1 wt.% loading under a strain of 7. The results show that the retraction process in this system is mainly controlled by interfacial phenomena rather than bulk rheological properties. Additionally, the shape evolution of droplets changes and the retraction rate slows down in the presence of nanoparticles.     

Exhaustive Classification of the Invariant Solutions for a Specific Nonlinear Model Describing Near Planar and Marginally Long-Wave Unstable Interfaces for Phase Transition

Problems of thermodynamic phase transition originate inherently in solidification, combustion and various other significant fields. If the transition region among two locally stable phases is adequately narrow, the dynamics can be modeled by an interface motion. This paper is devoted to exhaustive analysis of the invariant solutions for a modified Kuramoto-Sivashinsky equation in two spatial and one temporal dimensions is presented. This nonlinear partial differential equation asymptotically characterizes near planar interfaces, which are marginally long-wave unstable. For this purpose, by applying the classical symmetry method for this model the classical symmetry operators are attained.Moreover, the structure of the Lie algebra of symmetries is discussed and the optimal system of subalgebras, which yields the preliminary classification of group invariant solutions is constructed. Mainly, the Lie invariants corresponding to the infinitesimal symmetry generators as well as associated similarity reduced equations are also pointed out. Furthermore,the nonclassical symmetries of this nonlinear PDE are also comprehensively investigated.     

Simultaneous Expression of GUS and Actin Genes by Using the Multiplex RT-PCR and Multiplex Gold Nanoparticle Probes

Gene expression analysis is considered to be extremely important in many different biological researches. DNA-based diagnostic test, which contributes to DNA identification, has higher specificity, cost, and speed than some biochemical and molecular methods. In this study, we try to use the novel nano technology approach with Multiplex RT-PCR and Gold nano particular probes (GNPs-probes) in order to get gene expression in Curcumas melons. We used Agrobacterium tumefactions for gene transfer and GUS reporter gene as a reporter. After cDNA synthesis, Multiplex PCR and Multiplex RT-PCR techniques were used. Finally, probes were designed for RNA of GUS and Actin genes, and then the analysis of the gene expression using the probes attached to GNPs was carried out and the color changes in the GNPs were applied. In the following, probes hybridization was checked with DNA between 400 to 700 nm wavelengths and the highest rate was observed in the 550 to 650 nm. The results show that the simultaneous use of GNP-attached detectors and Multiplex RT-PCRcan reduce time and costmore considerably than somelaboratory methods for gene expiration investigation. Additionally, it can be seen thatthere is an increase in sensitivity and specificity of our investigation. Based on our findings, this can bea novel study doneusingMultiplex RT-PCRand unmodified AuNPs for gene transfer and expression detection to plants. We can claim that this assay has a remarkable advantage including rapid, cost-effectiveness, specificity and accuracy to detect transfer and expression genes in plants. Also,we can use this technique from other gene expressionsin many different biology samples.