3-(2-Pyridyl)-[1,2,3]triazolo[1,5-a]pyridines. An experimental and theoretical (DFT) study of the ring-chain isomerization

An experimental ((1)H NMR) and theoretical (DFT) study of the ring-chain-ring isomerization of 3-(2-pyridyl)-[1,2,3]triazolo[1,5-a]pyrid-7-yl derivatives (A) into 6-{[1,2,3]triazolo[1,5-a]pyrid-3-yl}-2-pyridyl derivatives (B) has been carried out. Based on the calculations, a mechanism of several steps will be proposed. The experimental results as well as the calculations lead to the conclusion that the A-B ratio depends on the electronic properties of the substituents.     

Reductive Amination of Aldehydes and Ketones to Their Corresponding Amines with NaBH4 in Micellar Media

A variety of aliphatic and aromatic aldehydes and ketones were efficiently reduced to their corresponding amines when treated with primary and secondary amines and NaBH₄ in micellar media at room temperature under neutral conditions.     

Application of the ISM EoS for polymer melts

A method for predicting an analytical equation of state for polymer melts from surface tension and liquid state density at the freezing temperature (γ_f,ρ_f), as scaling constants, is presented. B₂(T) follows a promising corresponding-states principle. Calculation of α(T) and b(T), the two other temperature-dependent constants of the equation of state, are made possible by scaling. As a result, γ_f and ρ_f are sufficient for the calculation of thermophysical properties of polymer melts. We applied the procedure to predict specific volumes of polyethylene glycol (PEG), polypropylene glycol (PPG), polypropylene (PP) and polyvinylchloride (PVC) at compressed state with temperature range from 298.15 to 423.15 K and pressures up to 200 MPa. The experimental specific volumes were correlated satisfactorily with our procedure and the results are within 3%.     

Solventless synthesis of 2-aryl- 1-arylmethyl- 1H- 1, 3-benzimidazoles catalyzed by Fe（ClO4）3 at room temperature

A series of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles was synthesized expeditiously in good yields from o-phenylenediamines and aldehydes in the presence of Fe（ClO4）3 without solvent at room temperature.     

Amperometric Detection of Dopamine in the Presence of Ascorbic Acid Using a Nafion Coated Glassy Carbon Electrode Modified with Catechin Hydrate as a Natural Antioxidant

Catechin hydrate (trans-3,3,4,5,7-penta-hydroxyflavone) is a derivative of catechol, and it is one of the natural antioxidant and anticarcinogenic compounds found in many fruits and agricultural foods. A new electrode was prepared by electrodeposition of a catechin-hydrate film on the surface of an activated glassy carbon electrode, followed by coating with nafion layer. Cyclic voltammetry was used for the deposition process, and the resulting modified electrode was found to retain the activity of the quinone/hydroquinone group anticipated for a surface-immobilized redox couple. The cyclic voltammograms of the modified electrode indicated that the surface-confined catechin-hydrate was strongly dependent on the solution pH. The electrochemical behaviour and stability of the modified electrode were studied by cyclic voltammetry. The apparent charge transfer rate constant (k _s ) and electron transfer coefficient () between the electrode surface and adsorbed catechin hydrate were calculated as 0.41 and 0.31s^z–1 0.31, respectively. The modified electrode exhibits an electrocatalytic effect on dopamine oxidation in the pH range of 2 to 7. The modified electrode was used for the electrocatalytic oxidation of dopamine in the presence of ascorbic acid and the elimination of the interference by ascorbic acid (AA) when present in a 200-fold concentration excess. A very large decrease (400mV) in the overpotential for the oxidation of dopamine and current increase were observed on the surface of the modified electrode. Dopamine was determined amperometrically at the modified electrode in the concentration range of 100nM to 0.1mM. The detection limit (signal to noise is 3) and sensitivity are 11nM and 16nA/µM, respectively. The modified electrode was employed to determine DA in biological mediums.     

Synthesis and catalytic activity of a novel ionic liquid-functionalized metal–organic framework

In this research, a new heterogeneous catalyst is fabricated through covalent modification of iron-based metal–organic framework with ionic liquid. In more detail, using 2-aminoterephthalic acid and iron (III) chloride hexahydrate, amino-functionalized metal–organic framework has been synthesized and then reacted with 2,4,6-trichloro-1,3,5-triazine and 1,4-diazabicyclo[2.2.2]octane successively to furnish ionic liquid on metal–organic framework. The as-prepared catalyst was characterized by FTIR, TGA, BET, SEM/EDS, XRD and elemental mapping analysis and then employed for catalyzing synthesis of pyrano [2,3‐d]pyrimidines (with yields of 80–100%) from one-pot three-component reaction of aldehydes, barbituric acid and malononitrile in aqueous media. The catalytic test inferred high catalytic activity of the catalyst, superior to that of IL and metal–organic framework. Furthermore, the catalyst could be recovered and recycled for five reaction runs with preserving its morphology.

Graphic abstract

     

Nitration of Aromatic Compounds Catalyzed by Divanadium-Substituted Molybdophosphoric Acid,H<Subscript>5</Subscript>[PMo<Subscript>10</Subscript>V<Subscript>2</Subscript>O<Subscript>40</Subscript>]

Summary. The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H₅PMo₁₀V₂O₄₀, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions.     

Enhancement of the analytical properties and catalytic activity of a nickel hexacyanoferrate modified carbon ceramic electrode prepared by two-step sol-gel technique: application to amperometric detection of hydrazine and hydroxyl amine

The electroless sol-gel technique was used for the construction of nickel hexacyanoferrat (NiHCF) modified carbon composite electrodes (CCEs).This involves two steps: formation of a carbon ceramic electrode fabricated by nickel powder and then immersing the electrode into a sodium- hexacyanoferate solution for the immobilization of NiHCF films. The cyclic voltammety of the resulting modified CCEs prepared under optimum conditions, shows a well defined surface redox couple due to the [Ni^IIFe^III/II(CN)₆]^−2/−1 system. The effect of different alkali metal cations in supporting electrolyte on the behavior of the modified electrode were studied. The charge transfer coefficient (α) and charge transfer rate constant (k_s) for modified films were calculated. Hydrazine and hydroxylamine have been chosen as a model to elucidate the electocatalytic ability and analytical parameters of NiHCF modified CCE prepared by one and two-step sol-gel techniques and these compounds determined amperometically at the surface of modified electrodes. The latter shows a good electocatalytic activity towards the oxidation of hydrazine and hydroxylamine in the pH range 3-8 in comparison with CCEs modified by homogeneous mixture of graphite powder, Ni(NO₃)₂ and Na₂[Fe(CN)₆], (one-step sol-gel technique). Furthermore, the catalytic rate constant, linear dynamic range, limit of detection, and sensitivity for hydrazine and hydroxylamine detections were evaluated and compared with CCEs prepared with one-step sol-gel method. The modified CCEs containing NiHCF shows good repeatability, short response time, t 90%<3 s, long term stability (3 months) and excellent catalytic activity. Furthermore, the method of preparation is rapid and simple and the modified electrodes are renewed by simple mechanical polishing and immersing in [Na₃Fe(CN]₆] solution.     

Modified Merrifield resin-supported PCP pincer palladium nanoparticles as a new polymeric catalyst for cyanation of aryl iodides

A new tridentate PCP pincer palladium (Pd) complex based on cross-linked Merrifield resin containing phosphinite ligand was synthesized and characterized. This polymeric catalyst was used in preparation of benzonitriles from different aryl iodides using potassium hexacyanoferrate (II) as a cyanide source. The presence of active metallic Pd in the catalyst was verified by X-ray power diffraction and X-ray photoelectron spectroscopy techniques. Transmission electron microscopy showed good dispersion of catalytic sites in the range of 30–50 nm. The catalyst is easily separated from reaction mixture and can be used for several times in repeating cycles without considerable loss of activity. The leaching of Pd from the support is negligible, which was confirmed by inductively coupled plasma–optical emission spectrometry and hot filtration test.