Synthesis and evaluation of the anti-microbial activity of new heterocycles containing the 1,3,4-thiadiazole moiety

A new series of thiadiazole-enaminones 4 were synthesized via reactions of 5-acetyl-1,3,4-thiadiazoles 3 with dimethylformamide-dimethylacetal (DMF-DMA). The simple phenyl substituted thiadiazole-enaminone 4f was used as a synthetic precursor for the preparation of a wide variety of new heterocyclic compounds, including the 5-substituted-1,3,4-thiadiazole derivatives 5, 6, 11, 12 and 13, which were obtained via reactions of 4f with nitrogen nucleophiles. Also, reactions of enaminone 4f with carbon nucleophiles afforded the respective 1,3,4-thiadiazoles 8a-d. In addition, the results of the antimicrobial activities of thiadiazole-enaminones 4 and their precursors 2 and 3 indicate that some members of this series display promising activities against all tested microorganisms.     

Applying green analytical chemistry (GAC) for development of stability indicating HPLC method for determining clonazepam and its related substances in pharmaceutical formulations and calculating uncertainty

Clonazepam contains one benzodiazepine ring in its chemical structure which makes it vulnerable to degradation. In this study, green analytical chemistry approach was applied in attempts for the development of validated stability indicating RP-HPLC method for determining clonazepam and its related substances in pharmaceutical formulation. Validation has been performed according to ICH guidelines. Assay was capable of simultaneous monitoring of the intact drug in the presence of its related substances within the same run. HPLC assay involved an ODS column and a mobile phase composed of 2% sodium dodecyl sulfate, 0.05 M sodium acetate buffer pH 3.5 and isopropanol in ratio (25:55:20) at a flow rate of 1.5 mL/min and detection was carried out at 254 nm. HPLC method allowed good resolution between the peaks that corresponded to the active pharmaceutical ingredients and its degradation products with good linearity, precision, accuracy, specificity, LOD and LOQ. The expanded uncertainty (0.33%) of the method was also estimated from method validation data. This analytical technique is not only ecofriendly but also faster than the conventional liquid chromatographic system official in the USP-36.     

Asymptotic modeling of Signorini problem with Coulomb friction for a linearly elastostatic shallow shell

In 2002–2003, Paumier studied the Signorini problem with friction in the linear Kirchhoff–Love theory of plates using the convergence method. In 2008, Léger and Miara generalized this study to the case of linearized shallow shell but without friction. The purpose of this paper is to extend those results to the case of linearized shallow shell with a Coulomb friction law. Copyright © 2015 John Wiley & Sons, Ltd.     

Platinum oxide catalyzed hydrosilylation of unsymmetrical internal aryl alkynes under ortho-substituent regiocontrol

[chemical reaction: see text]. PtO2- and H2PtCl6-catalyzed hydrosilylation of internal aryl alkynes having a para or an ortho substituent with triethylsilane are discussed and compared. The regioselectivity of the H-Si bond addition was found to be controlled by the ortho substituent rather than the nature of the platinum catalyst. Arylalkynes with an ortho substituent, regardless of its electronic nature, directed the silyl substituent mainly to the alpha-position. PtO2 proved to be a versatile and powerful catalyst compared to H2PtCl6 since it prevents the alkyne reduction.     

Organic inorganic dye filler for polymer: blue-coloured layered double hydroxides into polystyrene

A series of blue dye molecules, Evans blue (EB), Chicago sky blue (CB), Niagara blue (NB) were incorporated by direct co-precipitation within the galleries of negatively charge layered double hydroxide (LDH). The materials of cation composition Zn/Al = 2 lead to well-defined organic inorganic assemblies. The molecular arrangement of the interleaved dye molecule is proposed by 1D electronic density projection along the stacking direction for the hydrothermally treated samples with alternatively a highly inclined orientation of EB and CB and a parallel-bilayer arrangement for NB. Blue coloured LDH assemblies were subsequently dispersed into polystyrene (PS). It was found that the hybrid fillers do not interfere in the radical polymerization of styrene, giving rise to similar molecular weight and polydispersity than filler free PS, while higher glass transition temperatures were obtained for the nanocomposites. This was consistent with the rheological behaviour with the observation for LDH/NB filler based nanocomposite of shear thinning exponent different from zero, underlining frictional interaction between filler and PS chain. The absorption maximum slightly blue-shifted for the hybrid filler in comparison to the corresponding organic dye was found unmodified for the PS nanocomposite, thus giving rise to blue coloured plastic films, reminiscent somehow of the blue Maya effect.     

One-pot hydrosilylation-protodesilylation of functionalized diarylalkynes: a highly selective access to Z-stilbenes. Application to the synthesis of combretastatin A-4

An efficient stereoselective synthesis of Z-stilbenes has been developed from diarylalkynes via a new hydrosilylation-protodesilylation process. The scope and limitation of this method is presented to stereoselectively prepare a wide range of (Z)-stilbenes in a one-pot way is presented. A concise application to the preparation of combretastatin A-4 (CA-4), a vascular targeting agent inhibitor of tubulin polymerisation is described.