An efficient,expeditious, and diastereoselective one-pot pseudo-five-component reaction for the synthesis of new bis-Betti bases under catalyst-free conditions

A novel, diastereoselective, one-pot synthesis of new bis-Betti bases via condensation of dihydroxynaphthalene, two equivalents of aryl aldehydes, and two equivalents of 3-amino-5-methylisoxazole is reported. Conversion into the adducts was almost quantitative without the use of solvent or catalyst. The reaction conditions are very simple and enable easy isolation of the product.     

Performance improvement of PDMS/PES membrane by adding silicalite-1 nanoparticles: separation of xenon and krypton

The polydimethylsiloxane (PDMS) mixed matrix membrane with dispersed phase of nanozeolite silicalite-1 has been synthesized on polyethersulphone (PES) as a support, and its performance in the gas separation of xenon and krypton has been studied. For this purpose, nanozeolite silicalite-1 is synthesized by the hydrothermal clear solution method and is characterized by XRD and SEM analysis. In this research, the separation performance of MMM has also been compared with the polymeric PDMS membrane. Furthermore, the effect of feed pressure and loading percentage of nanozeolite in the polymeric matrix are evaluated. The results indicate that the addition of nanozeolite to the polymeric matrix improves its separation performance, and that the changes of the feed pressure have no major effect. The average permeability of the krypton and xenon gases through the PDMS polymeric membrane is calculated as 1.25 × 10^?9 and 1.78 × 10^?9 cm mol/(cm² s kPa), respectively, while by adding only 5 wt% of nanosilicalite-1 to the polymeric matrix of the membrane, this amount increased to 1.82 × 10^?9 and 8.07 × 10^?9 cm mol/(cm² s kPa), respectively. In addition, the presence of nanosilicalite-1 as the filler leads to an increase in the selectivity of xenon to krypton up to 4.38.     

Analytical solution of three-dimensional Navier–Stokes equations for the flow near an infinite rotating disk

In this letter, we will consider variational iteration method (VIM) and Padé approximant, for finding analytical solutions of three-dimensional viscous flow near an infinite rotating disk. The solutions is compared with the numerical (fourth-order Runge–Kutta) solution. The results illustrate that VIM–Padé is an appropriate method in solving the systems of nonlinear equations. It is predicted that VIM–Padé can have wide application in engineering problems (especially for boundary-layer and natural convection problems).     

Highly Regioselective Ring Opening of Epoxides with Thiols Catalyzed by SbCl3 Under Solvent-Free Conditions

The ring-opening reaction of epoxides with thiols by SbCl ₃ supported on Kieselguhr under solvent-free conditions, afforded high yields of β-hydroxy sulfides. Nucleophilic attack of the thiols occurs regioselectively at the less hindered side of the epoxides.     

One-Pot Stereoselective Synthesis of Alkyl Z-2-[2-Amino-4-oxo-1,3-selenazol-5(4H)-yliden] Acetates

Abstract

Selenourea reacts with dialkyl acetylenedicarboxylates in acetone to form 1:1 adducts, which undergo a cyclization reaction to produce alkyl Z-2-(2-amino-4-oxo-1,3-selenazol-5(4H)-yliden) acetates in fairly good yields. The reaction is completely stereoselective.     

Stereoselective Synthesis of Alkyl Z -2-(2-Amino-4-oxo-1,3-thiazol-5(4 H )-yliden)Acetates in Solventless Conditions

Tiourea reacts with dialkyl acetylenedicarboxylates in solventless conditions to form 1:1 adducts, which undergo a cyclization reaction to produce alkyl Z-2-(2-amino-4-oxo-1,3-thiazol-5(4H)-yliden)acetates in fairly good yields. The stereochemistry of the ethyl Z-2-(2-amino-4-oxo-1,3-thiazol-5(4H)-yliden)acetate was established by the use of X-ray single crystal structure analysis. The reaction is completely stereoselective.     

SYNTHESIS OF SOME BICYCLIC OXAZOLO- AND OXAZEPINOPYRIMIDINE DERIVATIVES

Oxazolopyrimidine compounds 2(a–c) and 3(a–e) were synthesized by a simple one-pot condensation reaction of the pyrimidine derivative 1 with 1,2-dibromoethane and 2-bromopropanoic acid, respectively. In a similar way the oxazepinopyrimidine compounds 4(a–b) were synthesized by reaction of 1 and 1,4-dichlorobutane in dioxane under reflux condition. The yields of products following recrystallization were of the order of 55–85%.