In this work, 1,4-disulfopiperazine-1,4-diium chloride ([Piper-(SO3H)2]·2Cl), as a novel Brönsted acidic ionic catalyst is synthesized and characterized using a series of techniques including FT-IR, TGA, DTA, SEM, pH analysis and Hammett acidity function. This substance can significantly catalyze the N-Boc protection of amines without solvent interference at room temperature. The advantages of this manner are chemoselectivity, short reaction times, suitable yields, excellent yields of the products, without solvent interference and ease of preparation as well as reusability of the catalyst. 相似文献
BiVO4-NPs can be used as an efficient and reusable nano-catalyst for the promotion of the synthesis of biscoumarins, bis(indolyl)methanes and 3,4-dihydropyrimidin-2(1H)-ones (thiones) derivatives. The structures of the products were characterized by IR, 1H NMR and 13C NMR spectroscopy and comparison with the authentic samples. Easy work-up procedure, excellent yields, short reaction times and reusability of the catalyst are some advantages of this work. In addition, in this article and for the first time, the preparation of 3,4-dihydropyrimidin-2(1H)-ones and -thiones from the protected derivatives of aldehydes including oximes, semicarbazones and 1,1-diacetates is reported. 相似文献
In the crystal structure of the title compound, 2C22H24P+·I82−, the I82− anion is located on a crystallographic inversion centre and consists of two tri‐iodide anions linked by di‐iodine at angles of 89.92 (4)° to form a planar `Z'‐shaped dianion. The octaiodides are linked via long‐range interactions [3.877 (11) Å] into infinite polyiodide ribbons. This is the first example of a structure containing an [(o‐tolyl)3PMe]+ cation, and the CMe—P—C—CMe torsion angles of −54.0 (11), −51.3 (11) and −48.2 (11)° indicate that the configuration is exo3. 相似文献
In this study, aeroelastic analysis of a truncated conical shell subjected to the external supersonic airflow is carried out. The structural model is based on a combination of linear Sanders thin shell theory and the classic finite element method. Linearized first-order potential (piston) theory with the curvature correction term is coupled with the structural model to account for pressure loading. The influence of stress stiffening due to internal or external pressure and axial compression is also taken into account. The fluid-filled effect is considered as a velocity potential variable at each node of the shell elements at the fluid-structure interface in terms of nodal elastic displacements. Aeroelastic equations using the hybrid finite element formulation are derived and solved numerically. The results are validated using numerical and theoretical data available in the literature. The analysis is accomplished for conical shells of different boundary conditions and cone angles. In all cases the conical shell loses its stability through coupled-mode flutter. This proposed hybrid finite element method can be used efficiently for design and analysis of conical shells employed in high speed aircraft structures. 相似文献
In this paper we give a classification of plane symmetric static space-times using symmetry method. For this purpose we consider the Lagrangian corresponding to the general plane symmetric static metric in the Noether symmetry equation. This provides a system of determining equations. Solutions of this system give us classification of the plane symmetric static space-times according to their Noether symmetries. During this classification we recover all the results listed in Feroze et al. (J. Math. Phys. 42:4947, 2001) and Bashir and Ehsan (Il Nuovo Cimento B 123:1, 2008). 相似文献
Poly(4-vinylpyridinium) hydrogen sulfate solid acid was found to be efficient catalyst for preparation of 1,1-diacetate using ultrasound irradiation at ambient temperature and neat condition. Deprotection of the resulting 1,1-diacetates were achieved using the same catalyst in methanol solvent under ultrasound irradiation at room temperature. This new method consistently has the advantage of excellent yields and short reaction times. Utilization of solvent free, simple reaction conditions, isolation, and purification makes this manipulation very interesting from an economic and environmental perspective. Further, the catalyst can be reused and recovered for several times. 相似文献
Journal of Thermal Analysis and Calorimetry - The influence of using copper oxide–thermal oil on convective heat transfer and pressure drop in an upward flow in an inclined smooth tube is... 相似文献
This article studies buoyancy-driven natural convection of a nanofluid affected by a magnetic field within a square enclosure with an individual conductive pin fin. The effects of electromagnetic forces, thermal conductivity, and inclination angle of pin fin were investigated using non-dimensional parameters. An extensive sensitivity analysis was conducted seeking an optimal heat transfer setting. The novelty of this work lies in including different contributing factors in heat transfer analysis, rigorous analysis of design parameters, and comprehensive mathematical analysis of solution domain for optimization. Results showed that magnetic strength diminished the heat transfer efficacy, while higher relative thermal conductivity of pin fin improved it. Based on the problem settings, we also obtained the relative conductivity value in which the heat transfer is optimal. Higher sensitivity of heat transfer was, though, noticed for both magnetic strength and fin thermal conductivity in comparison to fin inclination angle. Further studies, specifically with realistic geometrical configurations and heat transfer settings, are urged to translate current findings to industrial applications.