Chemical and electrochemical procedures for the synthesis of diisopropyltetrahydroquinoxalinedione derivatives

Diisopropyltetrahydroquinoxalinedione derivatives are synthesized from the reaction of various catechols with N,N′-diisopropylethylenediamine. Both chemical and electrochemical methods give the same products. While the chemical synthesis is faster, the electrochemical synthesis provides higher yields.     

Efficient One-Step Conversion of Tetrahydropyranyl Ethers into Acetates and Formates in the Presence of Potassium Dodecatungstocobaltate K<Subscript>5</Subscript>CoW<Subscript>12</Subscript>O<Subscript>40</Subscript> · 3H<Subscript>2</Subscript>O

Tetrahydropyranyl ethers derived from primary alcohols were directly and efficiently converted into the corresponding acetates and formates by the action of ethyl acetate, acetic acid, acetic anhydride, and ethyl formate in the presence of a catalytic amount of potassium dodecatungstocobaltate K₅CoW₁₂O₄₀ · 3H₂O. Tetrahydropyranyl ethers derived from secondary alcohols and phenols can also be transformed into the corresponding acetates with the use of acetic anhydride, but K₅CoW₁₂O₄₀ · 3H₂O was ineffective for esterification with ethyl acetate, acetic acid, and ethyl formate.__________From Zhurnal Organicheskoi Khimii, Vol. 41, No. 3, 2005, pp. 403–405.Original English Text Copyright © 2005 by Rafiee, Tangestaninejad, Habibi, Mohammadpoor-Baltork, Mirkhani.The original article was submitted in English.     

Synthesis of arylaminotetrazoles by ZnCl2/AlCl3/silica as an efficient heterogeneous catalyst

Abstract  

Arylaminotetrazoles were efficiently synthesized from secondary arylcyanamides by application of ZnCl₂/AlCl₃/silica as a reusable heterogeneous Lewis acid catalyst. 5-Arylamino-1H-tetrazoles can be obtained from arylcyanamides carrying electron-withdrawing substituents on the aryl ring, while with electron-releasing groups 1-aryl-5-amino-1H-tetrazoles will be produced. The former isomer is also produced within longer reaction times (~20 h) even with electron-releasing groups.     

Dependence of nonlinear elasticity on filler size in composite polymer systems

Nanosized filler particles enhance the mechanical properties of polymer composites in a size-dependent fashion. This is puzzling, because classical elasticity is inherently scale-free, and models for the elasticity of composite systems never predict a filler-size dependence. Here, we study the industrially important system of silica-filled rubbers, together with a well-characterized model-filled crosslinked gel and show that at high filler content both the linear and nonlinear elastic properties of these systems exhibit a unique scaling proportional to the cube of the volume fraction divided by the particle size. This remarkable behavior makes it possible to predict the full mechanical response of particle-filled rubbers for small but finite deformations based solely on the rheology of the matrix and the size and modulus of the filler particles.     

Ueber die Identit?t des H?matoidins und Bilifulvins

Ohne Zusammenfassung     

Crystal structure of 1-methyl-3-([2,2-dimethyl-4,6-dioxo-1,3-dioxane-5-ylidene]methyl)urea

The crystal structure of 1-Methyl-3-([2,2-dimethyl-4,6-dioxo-1,3-dioxane-5-ylidene]methyl)urea (C₉H₁₂N₂O₅) has been determined by single crystal X-ray diffraction analysis. The crystals are monoclinic, a = 5.3179(2), b = 18.6394(6), c =10.8124(3) Å, β = 100.015(2)°, Z = 4, sp. gr. P2₁/c, R = 0.0381 for 2537 reflections with I > 2σ(I). Except for C(CH₃)₂ group, the molecule is planar. The structure is stabilized by inter- and intramolecular N-H...O hydrogen bonds and weak C-H...O interactions.     

Laccase-catalyzed,aerobic oxidative coupling of 4-substituted urazoles with sodium arylsulfinates: Green and mild procedure for the synthesis of arylsulfonyl triazolidinediones

The direct aerobic oxidation of 4-substituted urazoles using the laccase enzyme from Trametes versicolor in a phosphate buffer solution at ambient temperature, and subsequent cross-coupling with sodium benzenesulfinates was investigated to afford arylsulfonyl-1,2,4-triazolidine-3,5-dione derivatives in good to high yields.     

Electrospinning of Nanofibers Based on Chitosan/Gelatin Blend for Antibacterial Uses

Chitosan/gelatin blend nanofibers were electrospun and the focus of this study was on the chitosan and gelatin concretions and on morphology of resulting nanofibers. The morphology of electrospun chitosan/gelatin blend nanofibers were characterized using scanning electron microscope (SEM). The miscibility of blend was determined using a SEM and Fourier transform infrared spectrometer/attenuated total reflectance (FTIR/ATR). Antibacterial property and stability of samples was also investigated. Water contact angle measurement (WCA) was employed to investigate the wettability of nanofibers.     

Stereoselective synthesis of helical dihydrodipyrrolophenanthroline and hindrance hexa tert‐butyl carboxylatodipyrrolophenanthroline from reaction between 1,10‐phenanthroline and dialkyl acetylenedicarboxylates

High hindrance Hexa tert‐butoxy carbonyl dipyrrolophenanthroline and helical dihydropyrrolophen‐anthroline compounds were prepared from reactions between di tert‐butyl acetylenedicarboxylate and 1,10‐phenanthroline in polar solvents media.     

Reduction in the Resonance Error in Numerical Homogenization II: Correctors and Extrapolation

This paper is the follow-up of Gloria (Math Models Methods Appl Sci 21(8):1601–1630, 2011). One common drawback among numerical homogenization methods is the presence of the so-called resonance error, which roughly speaking is a function of the ratio \(\frac{\varepsilon }{\rho }\), where \(\rho \) is a typical macroscopic lengthscale and \(\varepsilon \) is the typical size of the heterogeneities. In the present work, we make a systematic use of regularization and extrapolation to reduce this resonance error at the level of the approximation of homogenized coefficients and correctors for general non-necessarily symmetric stationary ergodic coefficients. We quantify this reduction for the class of periodic coefficients, for the Kozlov subclass of almost-periodic coefficients, and for the subclass of random coefficients that satisfy a spectral gap estimate (e.g., Poisson random inclusions). We also report on a systematic numerical study in dimension 2, which demonstrates the efficiency of the method and the sharpness of the analysis. Last, we combine this approach to numerical homogenization methods, prove the asymptotic consistency in the case of locally stationary ergodic coefficients, and give quantitative estimates in the case of periodic coefficients.