Fast and Efficient Reductive Amination of Aldehydes by NaBH4/B(OH)3 and NaBH4/Al(OH)3

Reductive amination a variety of aldehydes and anilines to their corresponding secondary amines were carried out with NaBH₄/B(OH)₃ and NaBH₄/Al(OH)₃ as new reducing systems in CH₃CN at room temperature in high to excellent yields of products (90‐96%).     

ZnO as an Effective and Reusable Heterogeneous Catalyst for the Synthesis of Arylaminotetrazoles

ZnO is an effective heterogeneous catalyst for the reaction between arylcyanamides with sodium azide to synthesize the arylaminotetrazoles in good yields. This method has advantages of good yields, simple methodology, short reaction times, and easy workup. Furthermore, the catalyst can subsequently be reused for several times without any significant loss of activity.     

Electrochemical Oxidation of Iodide in the Presence of Benzenesulfinic Acids and Its Application to the Quasi-Catalytic Determination of Benzenesulfinic Acids

The mechanism of the electrochemical oxidation of iodide in the presence of 4-toluenesulfinic acid was studied in an aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results indicate that the anodically generated iodine reacts with 4-toluenesulfinic acid through a quasi-catalytic process. In addition, the results indicate the suitability of iodide as a mediator for the determination of 4-toluene-sulfinic acid in aqueous solutions. The quasi-catalytic peak currents are linearly dependent on the 4-toluene-sulfinic acid concentrations in the range 6.0 ×10⁻³ − 8.0 × 10⁻⁶ M.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 598–602.Original English Text Copyright © 2005 by Davood Nematollahi, Zinat Forooghi, Esmail Tammari.This article was submitted by the authors in English.     

Application of a Bayesian algorithm for the Statistical Energy model updating of a railway coach

The classical statistical energy analysis (SEA) theory is a common approach for vibroacoustic analysis of coupled complex structures, being efficient to predict high-frequency noise and vibration of engineering systems. There are however some limitations in applying the conventional SEA. The presence of possible strong coupling between subsystems and the lack of diffuseness result in a significant uncertainty. This is the main motivation for the present study, where a procedure to update SEA models is proposed. The proposed procedure is the combination of the classical SEA method and a Bayesian technique. Due to reasons such as finding a limited number of important parameters, using a limited search range, avoiding matrix inversion and taking the effect of noise into account, the proposed strategy can be considered as a proper alternative to the experimental SEA approach. To investigate the performance of the proposed strategy, the SEA model updating of a railway passenger coach is carried out. First, a sensitivity analysis is carried out to select the most sensitive parameters of the SEA model. For the selected parameters of the model, prior probability density functions are then taken into account based on published data on comparison between experimental and theoretical results, so that the variance of the theory is estimated. The Monte Carlo Metropolis Hastings algorithm is employed to estimate the modified values of the parameters. It is shown that the algorithm can be efficiently used to update the SEA models with a high number of unknown parameters.     

Efficient synthesis and metal cations complexation of some novel dinaphthosulfide-substituted macrocyclic diamides

Some dinaphthosulfide aza macrocycles (3–9) were synthesized based on the conventional route from the reaction of corresponding dinaphthosulfide diester and aliphathic diamines in refluxing methanol in good yields. Dinaphthosulfide diester were synthesized from the reaction of 1,1′-thiobis (2-hydroxy naphthalene) and methyl chloroacetate. The structures of these compounds were confirmed using IR, ¹H NMR, ¹³C NMR, MASS spectroscopy and elemental analysis. Conductometric studies of the complexation of some metal ions with aza derivative 8 (TDN) in methanol as solvent implied the formation of 1:1 complexes. The stability of the 1:1 complexes of TDN decreases in the order Hg²⁺ >> Pb²⁺ > Cu²⁺ > Zn²⁺ > Ca²⁺ > Mg²⁺ > Cd²⁺ > Sr²⁺ > Ag⁺ > Ba²⁺.     

Microwave-Induced Solvent-free Synthesis of β-Keto Esters Using Montmorillonite KSF and K10 Clays as Efficient and Recyclable Heterogeneous Solid Acids

Montmorillonite KSF and K10 clays catalyzed effectively the reaction of methyl diazoacetate with various aldehydes using microwave irradiation under solvent-free conditions affording the corresponding β-keto esters in good yields and short reaction time. The present method is an improvement for the previous known synthetic methods and has many obvious advantages compared to them including the high efficiency, generality, high yields, operational simplicity, environmental benignity, and possibility of recycling the natural solid clays.     

Module Arens regularity for semigroup algebras

We extend the concept of Arens regularity of a Banach algebra to the case that there is an -module structure on , and show that when S is an inverse semigroup with totally ordered subsemigroup E of idempotents, then A=ℓ ¹(S) is module Arens regular if and only if an appropriate group homomorphic image of S is finite. When S is a discrete group, this is just Young’s theorem which asserts that ℓ ¹(S) is Arens regular if and only if S is finite. An erratum to this article can be found at     

Mechanistic study of electrochemical oxidation of 2,5-dihydroxybenzoic acid and 3,4-dihydroxybenzaldehyde in the presence of 3-hydroxy-1H-phenalene-1-one

The mechanism of the electrochemical oxidation of 2,5-dihydroxybenzoic acid and 3,4-dihydroxybenzaldehyde in the presence of 3-hydroxy-1H-phenalene-1-one as a nucleophile has been studied in water/acetonitrile (80/20 v/v) solution using cyclic voltammetry and controlled-potential coulometry methods. The results indicate that the quinones derived from oxidation of 2,5-dihydroxybenzoic acid and 3,4-dihydroxybenzaldehyde participate in Michael addition reactions with 3-hydroxy-1H-phenalene-1-one and via ECE and ECEC mechanisms convert to the different products, with good yield under controlled potential conditions, at carbon electrode.     

Synthesis and Characterization of Al(OH)<Subscript>3</Subscript>, Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanoparticles and Polymeric Nanocomposites

Applying of the most toxic halogenated and aromatic flame retardants is limited with respect to the environmental requirements. Nontoxic Al(OH)₃ nanoparticles were synthesized via a simple surfactant-free precipitation reaction at room temperature. The effect of various precipitation-agents on the morphology of the products was investigated. Al(OH)₃ nanoparticles were added to the polysulfone and poly styrene (PS) matrices. Electron microscope images show excellent dispersion of aluminium hydroxide in PS matrix. Nanoparticles appropriately enhanced both thermal stability and flame retardant property of the polymeric matrices. The enhancement of flame retardancy is due to endothermic decomposition of Al(OH)₃ that absorbs heat and simultaneously releases of water (makes combustible gases diluted and cold). Dispersed nanoparticles play the role of a barrier layer against flame, oxygen and polymer volatilization. Al(OH)₃ was converted to Al₂O₃ and its photo-catalyst property in degradation three different organic dyes as pollutants was investigated.     

Electrosynthesis of symmetric and highly conjugated benzofuran via a unique ECECCC electrochemical mechanism: evidence for predominance of electrochemical oxidation versus intramolecular cyclization

Electrochemical oxidation of hydroquinone, catechol, and some of their monosubstituted derivatives has been studied in the presence of 3-hydroxy-1H-phenalen-1-one (2) as a nucleophile in water/acetonitrile (80/20) solutions using cyclic voltammetry and controlled-potential coulometry methods. The results revealed that quinones derived from oxidation of hydroquinones and catechols participate in Michael addition reactions with 2. The formed adducts convert to the corresponding benzofuran derivatives via different mechanisms. In this work, we derived a variety of products with good yields using controlled potential electrochemical oxidation at a graphite electrode in an undivided cell.