Synthesis of 3,7-diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans: functional building blocks for the design of new conjugated polymers

3,7-Diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans are efficiently prepared by an iodine-promoted double cyclization. This new heterocyclic core is readily modified by the attachment of alkyl chains for improved solubility. The use of these compounds for the synthesis of new conjugated polymers is also reported.     

Structural and optical characterization of Ag-doped TiO2 nanoparticles prepared by a sol–gel method

Undoped and silver-doped TiO₂ nanoparticles (Ti_1?x Ag _x O₂, where x?=?0.00?C0.10) were synthesized by a sol?Cgel method. The synthesized products were characterized by X-ray diffraction (XRD), particle size analyzer (PSA), scanning electron microscope (SEM), and UV?CVisible spectrophotometer. XRD pattern confirmed the tetragonal structure of synthesized samples. Average crystallite size of synthesized nanoparticles was determined from X-ray line broadening using the Debye?CScherrer formula. The crystallite size was varied from 8 to 33?nm as the calcination temperature was increased from 300 to 800?°C. The incorporation of 3 to 5% Ag⁺ in place of Ti⁴⁺ provoked a decrease in the size of nanocrystals as compared to undoped TiO₂. The SEM micrographs revealed the agglomerated spherical-like morphology of particles. SEM, PSA, and XRD measurements show that the particles size of the powder is in nanoscale. Optical absorption measurements indicated a red shift in the absorption band edge upon silver doping. Direct allowed band gap of undoped and Ag-doped TiO₂ nanoparticles measured by UV?CVis spectrometer were 3.00 and 2.80?eV, respectively, at 500?°C.     

Aqua mediated indium(III) chloride catalyzed synthesis of fused pyrimidines and pyrazoles

The utilization of water as solvent and indium trichloride as promoter for the three-component combinatorial synthesis of a variety of bioactive pyrimidine and pyrazole derivatives (2–10) from aldehydes, 1,3-dicarbonyl compounds, and electron-rich amino heterocycles like 6-amino-1,3-dimethyl uracil and 3-methyl-1-phenyl-1H-pyrazol-5-amine catalyzed by indium trichloride under reflux has been studied. A new class of pyrimidine derivatives (2) has also been synthesized and the structure was confirmed by single crystal X-ray analysis. The reactions are environmentally benign, reaction product could be isolated easily and the catalyst could be recycled, which makes it an appealing synthetic protocol.     

Pd-catalyzed amination of 6-halo-2-cyclopropyl-3-(pyridyl-3-ylmethyl) quinazolin-4(3H)-one

6-Halo-2-cyclopropyl-3-(pyridyl-3-ylmethyl) quinazolin-4(3H)-one derivatives have been synthesized and utilized for amination reactions with aryl, heteroaryl and alkyl amines. Optimization of reaction conditions with different catalysts, ligands, bases, and solvents was conducted. The combination of Pd₂(dba)₃ with DavePhos (L3) proved to be best for these conversions in the presence of NaO^tBu in 1,4-dioxane at 100 °C. The relative reactivities of 6-bromo and 6-chloro-2,3-disubstitued quinazolinones with p-toluidine were conducted and as anticipated the 6-bromo analogue was totally consumed and 6-chloro derivative was completely unreactive.     

化学反应对竖直平板边界磁流体动力学微极流体滑流的影响

Heat and mass transfer effects on the unsteady flow of a micropolar fluid through a porous medium bounded by a semi-infinite vertical plate in a slip-flow regime are studied taking into account a homogeneous chemical reaction of the first order. A uniform magnetic field acts perpendicular to the porous surface absorb micropolar fluid with a suction velocity varying with time. The free stream velocity follows an exponentially increasing or decreasing small perturbation law. Using the approximate method, the expressions for the velocity microrotation, temperature, and concentration are obtained. Futher, the results of the skin friction coefficient, the couple stress coefficient, and the rate of heat and mass transfer at the wall are presented with various values of fluid properties and flow conditions.     

Asymmetric aldol additions: use of titanium tetrachloride and (-)-sparteine for the soft enolization of N-acyl oxazolidinones, oxazolidinethiones, and thiazolidinethiones.

Asymmetric aldol additions using chlorotitanium enolates of N-acyloxazolidinone, oxazolidinethione, and thiazolidinethione propionates proceed with high diastereoselectivity for the Evans or non-Evans syn product depending on the nature and amount of the base used. With 1 equiv of titanium tetrachloride and 2 equiv of (-)-sparteine as the base or 1 equiv of (-)-sparteine and 1 equiv of N-methyl-2-pyrrolidinone, selectivities of 97:3 to > 99:1 were obtained for the Evans syn aldol products using N-propionyl oxazolidinones, oxazolidinethiones, and thiazolidinethiones. The non-Evans syn aldol adducts are available with the oxazolidinethione and thiazolidinethiones by altering the Lewis acid/amine base ratios. The change in facial selectivity in the aldol additions is proposed to be a result of switching of mechanistic pathways between chelated and nonchelated transition states. The auxiliaries can be reductively removed or cleaved by nucleophilic acyl substitution. Iterative aldol sequences with high diastereoselectivity can also be accomplished.     

Radiation effect on temperature distribution in three-dimensional Couette flow with suction or injection

A theoretical analysis of three-dimensional Couette flow with radiation effect on temperature distribution has been analysed, when the injection of the fluid at the lower stationary plate is a transverse sinusoidal one and its corresponding removal by constant suction through the upper porous plate is in uniform motion. Due to this type of injection velocity, the flow becomes three-dimensional. The effect of Prandtl number, radiation parameter and injection parameter on rate of heat transfer has been examined by the help of graphs. The Prandtl number has a much greater effect on the temperature distribution than the injection or radiation parameter.     

Revisiting and enhancing electrochemical properties of SnO2 as anode for sodium-ion batteries

Journal of Solid State Electrochemistry - The tin oxide (SnO2) thin films have been prepared by the pulsed laser deposition (PLD) at deposition temperatures (Td) ranging from 300 to...     

Weighting method for bi-level linear fractional programming problems

In this paper we consider the solution of a bi-level linear fractional programming problem (BLLFPP) by weighting method. A non-dominated solution set is obtained by this method. In this article decision makers (DMs) provide their preference bounds to the decision variables that is the upper and lower bounds to the decision variables they control. We convert the hierarchical system into scalar optimization problem (SOP) by finding proper weights using the analytic hierarchy process (AHP) so that objective functions of both levels can be combined into one objective function. Here the relative weights represent the relative importance of the objective functions.     

Low-limit photo-acoustic detection of solid RDX and TNT explosives with carbon dioxide laser

We report the absorption spectra of RDX and TNT explosive samples in solid form at room temperature using a carbon dioxide laser-based photo-acoustic technique. A continuous wave ¹²C¹⁶O₂ laser, tunable between the 9.25–10.74 μm wavelength region, was used as an energy source. Interference-free limits of detection of solid RDX and TNT in simulated samples are estimated to be 10.0 and 16.5 ppbw, respectively. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 113–118, January–February, 2006.