Solvent-free Knoevenagel Condensations over TiO2

A study involving the scope of substrates in the Knoevenagel reaction under SFC has been conducted. Reactivity trends favored formation of the condensation product using both electron deficient and rich aryl aldehydes. A recycling study confirmed that the reaction medium could be used multiple times affording, with each run, the desired condensation product in excess of 95% conversion.     

Lead ion-selective membrane electrodes based on some recently synthesized 9,10-anthraquinone derivatives

Four different 9,10-anthraquinone derivatives were studied to characterize their abilities as lead ion carrier in PVC membrane electrodes. The electrode based on 1,8-dihydroxy-2,7-bis(prop-2′-enyl)-9,10-anthraquinone exhibits a Nernstian response for Pb²⁺ ions over a wide concentration range (2.0×10⁻³–2.0×10⁻⁶ M). The response time of the sensor is 30 s and the membrane can be used for more than four months without observing any deviation. The electrode revealed comparatively good selectivities with respect to alkali, alkaline earth and some transition and heavy metal ions. It was used as an indicator electrode in potentiometric titration of sulfate ions with a lead ion solution.     

Electrocatalytic Reduction of Dioxygen at Carbon Paste Electrode Modified with a Novel Cobalt(III) Schiff's Base Complex

A carbon paste modified electrode with a new cobalt(III) Schiff's base complex (CPME) and its application to electrocatalytic activity for dioxygen reduction is developed. The electrochemical behavior and stability of the CPME as well as the two‐electron reduction of O₂ at the electrode were investigated using cyclic voltammetry, chronoamperometry and rotating disk electrode methods. At the CPME, the reduction of dioxygen to hydrogen peroxide occurs at potentials where it is not observed at a bare carbon paste electrode. The CPME exhibited potent and persistent electrocatalysis for O₂ reduction in acetate buffer solutions of pH 4.0 with an overpotential of about 800 mV lower than unmodified CPE and drastic increase in the peak current. The heterogeneous rate constant for the reduction of O₂ at the surface of CPME was determined by hydrodynamic voltammetry using the Koutecky–Levich plot. A possible catalytic mechanism is proposed and discussed.     

Synthesis of new di‐ and tetraazadibenzosulfoxide macrocycolic compounds

Novel macrocyclic di and tetraamide compounds have been synthesized by the reaction of 2‐2′‐sulfoxide‐bis‐(4‐methyl phenoxy) aceticester or aceticacid chloride) (obtained from corresponding bisphenol) with appropriate diamines. Also the results of the presence of base as template are discussed and compared.     

Electron Transfer Behavior through Densely Packed Self‐Assembled Monolayers of a Novel Heteroaromatic Thiol Derivative onto the Gold Surface

This article is describing the electrical characteristics of the self‐assembled monolayers (SAMs) formed during spontaneous chemical adsorption of a recently synthesized heteroaromatic thiol 2‐(2‐mercaptophenylnitrilomethylidyne)‐phenol ( L ). Some surfactants were used to regulate the electron transfer through the resulting SAMs, as investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results revealed that the surface structure is approximately complete and fractional coverage is very close to unity. The use of surfactants clearly improved the electron transfer properties. Furthermore, complementary experiments were carried out to investigate the electron transfer from modified surface to cytochrome C (cyt‐C), as a biological iron containing protein, which exists in living cells with important life roles. It was found that cyt‐C is able to interact with the modified surface so that it can be used as a scaffold to study the electrochemical characteristics of sensitive biological compounds like proteins. The voltammetric behavior of the redox protein on the resulting SAMs was found to be highly reproducible, emphasizing the fact that the protein denaturation is greatly suppressed.     

Solvent-free synthesis of highly functionalized indole-based 4,5-dihydrofurans and evaluation of their antioxidant activity

Facile and efficient diastereoselective synthesis of trans-indolyldihydrofurans by three-component reaction of 3-cyanoacetyl indoles with various aromatic aldehydes and N-phenacylpyridinium bromides in presence of 1,1,3,3-N,N,N′,N′-tetramethylguanidine under solvent-free conditions is described. This ecofriendly protocol offers several advantages such as a cost-effective procedure with excellent yield, short reaction time, ease workup and product isolation, good functional group tolerance, and broad scope of usable substrates. The synthesized compounds were also evaluated for their antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay.     

Utilization of 2(3H)‐Furanone Bearing a Pyrazolyl Side Chain for the Construction of a Variety of Thiazolidinone Derivatives

2(3H)‐Furanone 1 was utilized for the construction of thiazolidinone derivatives. Thus, upon treatment the cyano derivatives 5 with thioglycolic acid afforded the thiazolidinone derivatives 6 . Reaction of the Schiff base derivative 9 with thioglycolic acid gave the thiazolidinone derivative 10 . Decomposition of the azides 11 in dry benzene in the presence of thioglycolic acid gave the thiazolidindione derivative 12 . Antimicrobial activities of synthesized compounds were tested. Some of the tested compounds showed promising activities.     

Torsional buckling of generally laminated conical shell

Meccanica - Buckling of generally laminated conical shells under uniform torsion with simply-supported boundary conditions is investigated. The Donnel type strain displacement relations are used to...