Aromatization of 1,4-Dihydropyridines Under Mild and Heterogeneous Conditions

A combination of Mg(HSO₄)₂ and NaNO₂ in the presence of wet SiO₂ was used as an effective oxidizing agent for the oxidation of dihydropyridines to their corresponding pyridine derivatives at room temperature with moderate to excellent yields.     

An Efficient Method for the Oxidation of Hantzsch 1,4-Dihydropyridines to their Corresponding Pyridine Derivatives Under Mild and Heterogeneous Conditions

A combination of oxalic acid dihydrate and sodium nitrite in the presence of wet SiO₂ was used as an effective oxidizing agent for the oxidation of dihydropyridines to their corresponding pyridine derivatives at room temperature with excellent yields.     

Cut-off analysis of coherent vortical structure identification in a three-dimensional external flow

Vortical structure identification has more recently been applied in the study of the transport of vortical structures in low Reynolds number three-dimensional complex geometry flows. An important issue in this identification procedure is to choose an appropriate cut-off value ${\lambda }_2$ which takes into consideration the finite precision vortex interfaces. This cut-off choice is studied in this Note and applied to an external flow around a curved cylinder. The vortex identification technique at different cut-off values is compared to the threshold of the vorticity field showing the efficiency of choosing the optimal tolerance gap. The computations are performed with a fully three-dimensional spectral/hp element method. To cite this article: A. Miliou et al., C. R. Mecanique 333 (2005).     

Étude de la convergence numérique d'une méthode vortex pour un écoulement a grand nombre de Reynolds dans un mélangeurNumerical convergence of vortex method for a high Reynolds number 2D bluff-body flow

In this paper the convergence of the RVM for a complex flow is studied, in function of three discretization parameters. Two of these parameters are related to the spatial discretization of the vorticity Γ (sheet or blob strength) and h (sheet length or core radius) and the third one to the time discretization Δt. Two main events are observed: first, the computation works but the convergence is not attained, secondly the computation fails. The first behaviour is attributed to a lack of accuracy and the second to a lack of numerical stability. Once the stability conditions are satisfied, decreasing the value of parameters always leads to convergence. To cite this article: I. Mortazavi et al., C. R. Mecanique 330 (2002) 409–416.     

Selective oxidation of alkenes using [bmim]5[PW11ZnO39]·3H2O hybrid catalyst

The catalytic activity of [bmim]₅[PW₁₁ZnO₃₉]·3H₂O as a hybrid catalyst was studied in the oxidation of various alkenes in acetonitrile, using hydrogen peroxide as oxygen source. The effect of reaction parameters such as type of solvent and oxidant, amount of catalyst and oxidant, and temperature was also investigated. From our results, [bmim]₅[PW₁₁ZnO₃₉]·3H₂O hybrid catalyst gave higher yields and selectivity in the oxidation of alkenes and was reused four times without loss of its catalytic activity.     

A mild and efficient method for the methoxymethylation and acetylation of alcohols promoted by benzyltriphenylphosphonium tribromide

<正>A mild and efficient method for the conversion of alcohols to their corresponding methoxymethyl ethers and acetates using benzyltriphenylphosphonium tribromide(BTPTB) as catalyst is described.All reactions were performed under completely heterogeneous reaction conditions in good to high yields.     

Regioselective multi-component synthesis of 1H-pyrazolo[3,4-d]pyrimidine-6(7H)-thiones

A variety of pyrazolo[3,4-d]pyrimidine-6(7H)-thione derivatives were easily synthesized with a novel, simple, efficient, and regioselective method via three-component condensation reaction of 5-methyl-1H-pyrazol-3-amine, arylisothiocyanates, and aldehydes in the presence of catalytic amount of p-toluenesulfonic acid (p-TSA) in 1-butyl-3-methylimidazolium bromide ionic liquid with excellent yields and short reaction times.     

Bis[N‐(4‐nitrophenyl)thiobenzamidato]mercury(II)

The molecule of the title compound, [Hg(C₁₃H₉N₂O₂S)₂], has approximate twofold rotation symmetry, with the Hg atom in an essentially linear two‐coordinate HgS₂ environment supported by secondary π interactions with the nitrophenyl rings of both ligands. The ligands are in the imine–thiolate rather than the amine–thione tautomeric form.     

Graphene oxide nanosheets supported manganese(III) porphyrin: a highly efficient and reusable biomimetic catalyst for epoxidation of alkenes with sodium periodate

Efficient epoxidation of alkenes catalyzed by tetrakis(p-aminophenyl)porphyrinatomanganese(III) chloride, [Mn(TNH₂PP)Cl], supported on graphene oxide nanosheets, is reported. The catalyst, [Mn(TNH₂PP)Cl]@GO, was prepared by covalent attachment of amino groups of porphyrin to carboxylic acid groups of GO. This new heterogenized catalyst was characterized by ICP, FT-IR and diffuse reflectance UV–vis spectroscopies, scanning electron microscopy and transmission electron microscopy. This catalyst was applied as an efficient and reusable catalyst in the epoxidation of alkenes with NaIO₄ at room temperature, in the presence of imidazole as axial ligand. The most noteworthy advantage of [Mn(TNH₂PP)Cl]@GO is its high reusability in the oxidation reactions, in which the catalyst was reused several times without significant loss of its catalytic activity.     

C–S Targeted Biodegradation of Dibenzothiophene by Stenotrophomonas sp. NISOC-04

Crude oil-contaminated soil samples were gathered across Khuzestan oilfields (National Iranian South Oil Company, NISOC) consequently experienced a screening procedure for isolating C-S targeted dibenzothiophene-biodegrading microorganisms with previously optimized techniques. Among the isolates, a bacterial strain was selected due to its capability of biodegrading dibenzothiophene in a C-S targeted manner in aqueous phases and medium mostly consisting of separately biphasic water-gasoline. The 16S rDNA of the isolate was amplified using eubacterial-specific primers and then sequenced. Based on sequence data analysis, the microorganism, designated NISOC-04, clustered most closely with the members of the genus Stenotrophomonas. Gas chromatography indicated that Stenotrophomonas sp. NISOC-04 utilizes 82% of starting 0.8 mM dibenzothiophene within a 48-h-long exponential growth phase. Growth curve analysis revealed the inability of Stenotrophomonas sp. NISOC-04 to utilize dibenzothiophene (DBT) as the exclusive carbon or carbon/sulfur source. Gibbs' assay showed no 2-hydroxy biphenyl accumulation, but HPLC confirmed the presence of 2-hydroxy biphenyl as the final product of DBT desulfurization. Under sulfur starvation, Stenotrophomonas sp. NISOC-04 produced a huge biomass with untraceable sulfur and utilized atmospheric insignificant sulfur levels.