Al(HSO4)3 and Al2O3-SO3H as Efficient Catalysts for Modified Preparation of 3,4-Dihydropyrimidin-2 (1H)-ones/thiones

An environmentally friendly procedure for the preparation of dihydropyrimidinone derivatives or their sulfur analogues under thermal solvent-free conditions in the presence of aluminium hydrogen sulfate [Al(HSO₄)₃] and alumina sulfuric acid (Al₂O₃-SO₃H) as heterogeneous catalysts was developed.     

Reaction in Dry Media: Silica Gel Supported Ferric Chloride Catalyzed Synthesis of 1,8-Dioxo-octahydroxanthene Derivatives

Herein, we describe a green procedure for the one-pot preparation of 1,8-dioxo-octahydroxanthene derivatives by condensation of dimedone and substituted benzaldehydes in the presence of FeCl ₃ -SiO ₂ as an efficient and heterogeneous catalyst under microwave irradiation and thermal conditions. This method has the advantages of high yields, cleaner reactions, efficient and cost-effective method, simple methodology, short reaction times, easy workup, and greener conditions.     

Synthesis of New and Novel N-Protected 1-Aminoalkyl-2-naphthol Derivatives

A series of three-component reactions has been carried out using HClO₄-SiO₂ as a versatile heterogeneous catalyst. A series of new and novel N-protected 1-aminoalkyl-2-naphthol derivatives have been prepared under thermal solvent-free reaction conditions. In all cases, the reaction conditions were very simple and high-yielding.     

Adsorption sensitivity of pristine and Al- or Si-doped boron nitride nanoflake to COCl2: a DFT study

ABSTRACT

The adsorption of phosgene (COCl₂) on pristine, Al- and Si-doped boron nitride nanoflakes (BNNFs) is studied using density functional theory calculations. The adsorption energies of the most stable complexes, formed from interaction between COCl₂ and the pristine, Al- and Si-doped BNNFs are ?28.97, ?78.71 and ?171.60?kJ/mol at the M06-2X/6-31?+?G* level of theory, respectively. It is found that COCl₂ experiences a chemisorption interaction over the doped BNNFs, significantly altering its structure with respect to the gas-phase molecule. The COCl₂ adsorption can also induce a change in the HOMO–LUMO or SOMO–LUMO energy gap of the surface. In particular, the adsorption of COCl₂ is found to decrease the HOMO–LUMO energy gap of Al-doped BNNF by about 30%. It is suggested that the Al- or Si-doped BNNFs can be considered as a potential material for detecting toxic COCl₂.     

Intramolecular cyclization of <Emphasis Type="Italic">N</Emphasis>-propargyl anilines: a new synthetic entry into highly substituted indoles

Indole derivatives are an important class of heterocycle found in a large number of natural products and synthetic pharmaceuticals. Given the low cost and easy availability of N-propargyl anilines, synthesis of indole cores from these versatile structural motifs has attracted a lot of attention in the past decade. In this review, we summarize the most representative and interesting reports on this rapidly advancing area, with special emphasis on mechanistic aspects of the reactions.     

A nonconvex quadratic optimization approach to the maximum edge weight clique problem

The maximum edge weight clique (MEWC) problem, defined on a simple edge-weighted graph, is to find a subset of vertices inducing a complete subgraph with the maximum total sum of edge weights. We propose a quadratic optimization formulation for the MEWC problem and study characteristics of this formulation in terms of local and global optimality. We establish the correspondence between local maxima of the proposed formulation and maximal cliques of the underlying graph, implying that the characteristic vector of a MEWC in the graph is a global optimizer of the continuous problem. In addition, we present an exact algorithm to solve the MEWC problem. The algorithm is a combinatorial branch-and-bound procedure that takes advantage of a new upper bound as well as an efficient construction heuristic based on the proposed quadratic formulation. Results of computational experiments on some benchmark instances are also presented.     

An Experimental Setup for Combined In-Vacuo Raman Spectroscopy and Cavity-Interferometry Measurements on TMDC Nano-resonators

Experimental Mechanics - Nanoelectromechanical (NEMS) systems fabricated using atomically thin materials have low mass and high stiffness and are thus ideal candidates for force and mass sensing...     

Chloropicrin sensor based on the pristine BN nanocones: DFT studies

Structural Chemistry - We investigated the chloropicrin adsorption on the BN nanocones using DFT calculations. We selected two kinds of BN nanocones with 180? disclination angle entailing BN-N...     

Synthesis,structure, spectroscopic,magnetic and electrochemical studies of a rare syn–anti acetate-bridged copper(II) complex

The structure, spectroscopy and electrochemical properties of a novel dinuclear copper(II) complex, [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ where phen = 1,10-phenanthroline, is reported. The crystal structure contains two independent Cu(II) ions, with different geometry around each copper center, which are bridged by an acetate anion. The acetate-bridged ligand shows a syn–anti coordination mode with a trigonal bipyramidal geometry for the Cu(1) center and a distorted square-based pyramidal geometry for the Cu(2) center. The angular structural index parameter τ for Cu(1) and Cu(2) is 0.9 and 0.33, respectively. The copper(II) atoms display a different geometry with a N₄O chromophore group and with Cu–O distances of 1.993(5)–1.996(5) Å and Cu–N distances which vary from 1.980(5) to 2.161(6) Å. The intra Cu…Cu separation is 4.9904(5) Å. The effective magnetic moment (μ_eff) of the complex was measured by the Evans method. The cyclic voltammogram of [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ shows two waves at positive potential which are assigned to the two Cu(II/I) reduction couples.     

Exact three-dimensional interface stress and electrode-effect analysis of multilayer piezoelectric transducers under torsion

In this paper, exact three-dimensional analysis for torsion of multilayer piezoelectric transducers is presented to highlight the remarkable effects of electrode and size effects on interface stresses and deformation. A generalized formulation is introduced for torsion of an arbitrarily layered cross section. In order to reach an advanced and better device, multilayer piezoelectric materials with different properties are formulated while axis of torsion and the polarization axes of each layer make different orientations with respect to each other. An exact formulation for n-layer piezoelectric device with rectangular cross section is presented to compensate considerable deviation of previous studies’ results from exact solution due to the assumption of linear distribution for the electric potential. In order to improve the performance of the transducers, being utilized in industry, several case studies are presented in order to investigate the influence of different parameters, e.g. thickness and material properties of electrodes over shear and peel stresses. Besides, a correction factor is introduced to completely compensate the effect of ignoring electrodes.