γ‐Spiroiminolactone Synthesis by Reaction of Acetylenic Esters and α‐Dicarbonyl Compounds in the Presence of Aryl Isocyanide

The highly reactive 1∶1 intermediate produced in the reaction of aryl isocyanides and acetylenic esters was trapped by the α‐dicarbonyl compounds to yield γ‐spiroiminolactone derivatives in good yields.     

Reaction of Alkyl and Aryl Isocyanides with Floren‐9‐ones in the Presence of Acetylenic Esters: Preparation of γ‐Spiroiminolactones

The reactive 1∶1 intermediate generated by the addition of alkyl and aryl isocyanides to dialkyl acetylenedicarboxylate was trapped by 2,7‐dinitrofloren‐9‐one and floren‐9‐one to yield iminolactones in good yields.     

KF/Al2O3‐Mediated N‐Alkylation of Amines and Nitrogen Heterocycles and S‐Alkylation of Thiols

KF/Al₂O₃ efficiently catalyzes N‐alkylation of heterocyclic, primary, and secondary amines and S‐alkylation of thiols with a variety of alkyl halides. The N‐alkylation and S‐alkylation adducts were produced in good to excellent yields and in short times.     

Catalyst-Free,Direct, High Regio- and Chemoselective Conversion of Epoxides to Vicinal Haloesters Under Mild,Neutral, and Solvent-Free Conditions

Abstract

A catalyst-free, high regio- and chemoselective method is described for the mild conversion of wide varieties of epoxides directly to their corresponding vicinal haloesters using quaternary ammonium halides R₄N⁺X^- (X equals; Cl, Br, I; R = n-butyl, n-pentyl, n-hexyl) in the presence of an aliphatic or aromatic carboxylic anhydride at room temperature under neutral and solvent-free conditions.     

Facile Conversion of Aldehydes and Ketones to gem-Dichlorides Using Chlorodiphenylphosphine/N-Chlorosuccinimide as a New and Neutral System

Aldehydes and ketones are easily converted to their corresponding gem-dichlorides using a mixture of chlorodiphenylphosphine and N-chlorosuccinimide (ClPPh₂/NCS) in dichloromethane under neutral conditions and at room temperature.     

ZrOCl2·8H2O in water: An efficient catalyst for rapid one-pot synthesis of pyridopyrazines,pyrazines and 2,3-disubstituted quinoxalines

Zirconium(IV) oxide chloride was found to be a rapid and efficient catalyst for the synthesis of pyrazines and 2,3-disubstituted quinoxalines in water. A variety of pyridopyrazine and 2,3-disubstituted quinoxaline derivatives are readily prepared in high yields under green conditions by cyclocondensation of the desired 1,2-diamine and 1,2-diketone using a catalytic amount of zirconium(IV) oxide chloride in water. Less active diamines, such as 2,3- and 3,4-diaminopyridines took part in this protocol to provide the desired products in good to excellent yields.     

Existence results for a class of degenerate quasilinear elliptic systems

We establish existence results for weak solutions of degenerate quasilinear elliptic systems. By using the variational method we obtain the existence of a solution for an elliptic system with Dirichlet boundary condition under some restriction on λ.     

Fabrication of Au‐Nanoparticle/TiO2‐Nanotubes Electrodes Using Electrochemical Methods and Their Application for Electrocatalytic Oxidation of Hydroquinone

Gold nanoparticle (Au‐NPs)‐Titanium oxide nanotube (TiO₂‐NTs) electrodes are prepared by using galvanic deposition of gold nanoparticles on TiO₂‐NTs electrodes as support. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy results indicate that nanotubular TiO₂ layers consist of individual tubes of about 60–90 nm diameters and gold nanoparticles are well‐dispersed on the surface of TiO₂‐NTs support. The electrooxidation of hydroquinone of Au‐NPs/TiO₂‐NTs electrodes is investigated by different electrochemical methods. Au‐NPs/TiO₂‐NTs electrode can be used repeatedly and exhibits stable electrocatalytic activity for the hydroquinone oxidation. Also, determination of hydroquinone in skin cream using this electrode was evaluated. Results were found to be satisfactory and no matrix effects are observed during the determination of hydroquinone content of the “skin cream” samples.     

Polyelectrolyte Nanocomposite Membranes,Based on Chitosan-phosphotungstic Acid Complex and Montmorillonite for Fuel Cells Applications

A polyelectrolyte complex (PEC) of chitosan and phosphotungstic acid (PWA) was prepared and characterized as a proton-conducting membrane for direct methanol fuel cell (DMFC) applications. Fourier transform infrared spectroscopy showed the presence of stable PWA in PEC. To reduce the methanol permeability, several amounts of montmorilonite (MMT) nanoclays (trade name: Cloisite Na) were introduced to the system. The X-ray diffraction patterns of nanocomposite membranes proved the nanoclay layers were exfoliated in the membranes at loading weights of MMT lower than 3 wt%. Proton conductivity and methanol permeability were measured. According to the selectivity parameter—ratio of proton conductivity to methanol permeability—PEC containing 2 wt% MMT (PEC/2 wt% MMT) was identified as the optimum composition. Finally, DMFC performance tests were investigated at 70°C and 5 M methanol feed and the optimum membrane showed higher maximum power density in comparison with Nafion 117. The results indicated the optimum nanocomposite membrane is a promising polyelectrolyte membrane (PEM) for DMFC applications.