Silica iodide catalyzed,ultrasound-promoted,one-pot four-component synthesis of novel 1,4,5,6-tetrahydropyridine-3-carboxylate derivatives

Silica iodide catalyzed, competent synthesis of 15 novel substituted-1,4,5,6-tetrahydropyridine-3-carboxylate derivatives was achieved by a one-pot four-component cyclocondensation of Meldrum's acid, aryl aldehydes, aromatic amines and ethyl acetoacetate under ultrasonic irradiation. In comparison to the conventional methods, our protocol is convenient, eco-friendly and offers several benefits such as: mild conditions, high yields, shorter reaction time and ease in product isolation.     

Zinc‐containing ionic liquid as a dual solvent‐catalyst in base‐free condensations under ultrasonic irradiation

In this study, natural‐based ionic liquid (IL) using caffeine (Caff), trietahnolamine (TEA) and ZnBr₂, [Caff‐TEA]⁺[ZnBr₃]^?, which features high catalytic activity and environmentally‐friendly nature was synthesized with melting point of 76 °C by a facile method. The synthesized [Caff‐TEA]⁺[ZnBr₃]^? has high catalytic activity as both of catalyst and solvent in condensation reactions for the synthesis of benzylidenes, bis‐hydroxyenones and xanthenes. Synthesized IL was characterized by proton nuclear magnetic resonance (¹HNMR), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD) and Energy‐dispersive X‐ray spectroscopy (EDX) analysis. Also synthesized heterocycles were characterized by FT‐IR, proton nuclear magnetic resonance (¹HNMR) and carbon nuclear magnetic resonance (¹³CNMR).     

Hydrolytic polycondensation of trimethoxymethylsilane under ultrasonic irradiation

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Variations of the elastic constants of InSb near the covalent-metallic transition

Abstract

The pulse-echo-overlap method was used to measure the longitudinal and transverse wave velocities in single-crystal (100) and (111) samples of InSb up to 3 GPa at room temperature. The peculiar variations of the elastic constants were observed near the covalent-metallic transition.     

Weak coupling of a Reynolds model and a Stokes model for hydrodynamic lubrication

The Reynolds model is a reduced Stokes model, valid for narrow lubrication regions. In order to be able to handle locally non‐narrow regions such as pits or grooves, often displaying rapid geometrical variations, there is a need to be able to transit to the more accurate Stokes model. A fundamental problem is how to couple the two models in a numerical simulation, preferably allowing for different meshes in the different domains. In this paper, we present a weak coupling method for Reynolds and Stokes models for lubrication computations, including the possibility of cavitation in the different regions. The paper concludes with a numerical example. Copyright © 2010 John Wiley & Sons, Ltd.     

Functions of Acyclic Poly(ethylene Oxide) Homologs: Acceleration of Nucleophilic Reactions and Selective Ion Transport through Membranes

The acceleration effect of poly(ethylene oxide) on nucleophilic reactions was investigated. The enhancement of the reaction rate was interpreted by the cooperative solvation of alkali metal ions with ethereal oxygens of PEO resulting in active nucleophilic anions. In relation to the complex formation of alkali metal ions with PEO, the oligo(ethylene oxide) derivatives were prepared as the synthetic ionophores, which were able to transport alkali metal ions selectively through a liquid membrane against the alkali metal ion concentration.     

Miscibility Studies of Dextran/Poly(vinyl pyrrolidone) Blend in Solution

The miscibility of dextran (Dex)/poly(vinyl pyrrolidone) (PVP) in solution has been investigated in different percentages of the blend components by employing viscosity, density, refractive index and ultrasonic velocity methods at 30 and 50°C, respectively. Ultrasonic velocity and adiabatic compressibility against blend compositions were plotted and found to be linear. The interaction parameters μ and α have been obtained by using the viscosity data. The results indicated that the Dex/PVP blends are miscible in the entire composition range and it was further confirmed by ultrasonic velocity, density, refractive index studies. In addition, the results revealed that the change in temperature has no significant effect on the miscibility of Dex/PVP polymer blend.     

Synthesis of Novel Organosilicon Compounds Possessing Fully Substituted Imidazole Nucleus Sonocatalyzed by Fe-Cu/ZSM-5 Bimetallic Oxides

An efficient four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles is described by one-step condensation of an aldehyde, benzil, ammonium acetate, and primary aromatic amine with nanostructure Fe-Cu/ZSM-5 bimetallic oxides in water under ultrasonic irradiation. The short reaction time, good yields, environmental friendly procedure, mild reaction conditions, and convenient operation are important advantage of this protocol. The products generated during the study have been utilized as substrates for synthesis of organosilicon-containing imidazoles. Synthesis of tris(triorganosilyl)methylimidazole derivatives were carried out using organolithium reagent (Me₃Si)₃CLi, prepared via metalation of (Me₃Si)₃CH with methyllithium in tetrahydrofuran, in excellent yields.     

Sonochemical Formation of Iodohydrin and Epoxide from Cyclohexene

Ultrasonic irradiation substantially improves the reaction of cyclohexene with I₂ in aqueous dioxane in the presence of Cu(OAc)₂ · H₂O to generate the expected iodohydrin in high yield. The product undergoes cyclization to the epoxide by biphasic treatment with either Na₂CO₃ or KOH in a sonication‐sensitive step.     

Nondestructive damage assessment in fiber reinforced composites with the pulsed ultrasonic polar scan

This study investigates the use of both amplitude and time-of-flight based pulsed ultrasonic polar scan (P-UPS) as a sophisticated non-destructive damage sensor for fiber reinforced composites. Focus is put on stiffness related damage phenomena, which are in general difficult to monitor nondestructively, and their associated signature in the P-UPS image. Various composite samples, with different damage states, have been inspected at multiple material spots with the P-UPS technique. The results demonstrate the capability of the P-UPS method to obtain a unique signature of the local material damage characteristics. Several indicators in the acquired P-UPS images have been identified from which the type and level of material degradation can be obtained. The P-UPS extracted characteristics are fully supported by simulations, conventional tests as well as visual inspection.