Acid catalyzed stereoselective rearrangement and dimerization of flavenes: synthesis of dependensin

Appropriately substituted flavenes undergo stereoselective rearrangement and dimerization when treated with methanolic hydrochloric acid to give benzopyranobenzopyrans. A rationale for the rearrangement is proposed. This synthetic methodology has been used for a high yield synthesis of the natural product dependensin.     

Aggregation effects in maximum covering models

The level of aggregation is critical in discrete location analyses as it affects the level of data collection required, computation times and the usefulness of the analyses. We examine the effects of three alternative nodal aggregation schemes on (i) the model's solution times, (ii) the locational decisions indicated by the maximum covering model, (iii) the coverage provided by the aggregate solutions compared with the optimal solutions, and (iv) the coverage predicted by the aggregate model compared with the coverage that results from using the aggregate model's facility sites and the disaggregate demands. The results suggest that considerable aggregation can be tolerated without incurring large errors in total coverage, but that location errors are introduced at moderate levels of aggregation. The magnitude of these errors is significantly affected by the aggregation scheme employed.     

Simultaneous Determination of Pioglitazone and Glimepiride by High-Performance Liquid Chromatography

A rapid and accurate HPLC method has been developed for simultaneous determination of pioglitazone and glimepiride. Chromatographic separation of the two pharmaceuticals was performed on a Cosmosil C₁₈ column (150 mm × 4.6 mm, 5 m) with a 45:35:20 (v/v) mixture of 0.01 m triammonium citrate (pH adjusted to 6.95 with orthophosphoric acid), acetonitrile, and methanol as mobile phase, at a flow rate of 1.0 mL min^–1, and detection at 228 nm. Separation was complete in less than 10 min. The method was validated for linearity, accuracy, precision, limit of quantitation, and robustness [1, 2]. Linearity, accuracy, and precision were found to be acceptable over the ranges 2.50–30.00 g mL^–1 for pioglitazone and 0.10–10.00 g mL^–1 for glimepiride.     

Aggregation Behavior of Pluronic-L64 in Presence of Sodium Dodecyl Sulphate in Water

The effect of sodium dodecyl sulfate (SDS) on the micellization and aggregation behavior of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic copolymer (Pluronic L64: EO₁₃ PO₃₀ EO₁₃) have been investigated by various techniques like, cloud point, viscosity, isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC), fluorescence spectroscopy, room temperature phosphorescence (RTP), and small angle neutron scattering (SANS). Addition of SDS in L64 solutions shows mark alteration of different properties. We observed synergistic interaction between SDS and Pluronic L64. The changes in the critical micelle concentration (CMC), critical micelle temperature (CMT), cloud point (CP), micelle size, and shape has been correlated and reported in terms of structure dynamics and mechanics. The ITC titrations have been used to explore the different stages of binding and interactions of SDS with L64. The enthalpies of aggregation for copolymer-SDS aggregates binding, organizational change of bound aggregates, and the threshold concentrations of SDS in the presence of copolymer were estimated directly from ITC titration curves. The effect of temperature on enthalpy values has been reported in terms of different aggregation state. Fluorescence and RTP for L64 were used to investigate the change in micellar environment on the addition of SDS at different temperature. Appearance and shifting of SANS peaks have been used to monitor the size and inter micellar interaction on addition of SDS in L64 solution. Cloud point and viscosity elaborate the penetration of SDS molecule in L64 micelle and hence changing the micellar architect.     

Studies on morphology of polyaniline films formed at liquid–liquid and solid–liquid interfaces at 25 and 5 °C,respectively, and effect of doping

It is well accepted that the morphology of the nanomaterials has great effect on the properties and hence their applications. Therefore, morphology of materials has become a focus of research in the scientific world. The present study shows that interfacial polymerization and subsequent self-assembly provides a control over the morphology, nanorod/nanosheet, of polyaniline (PANI) films synthesized by liquid–liquid interface reaction technique and solid–liquid interface reaction technique. The synthesized PANI films and its particulate structure are characterized by using various spectroscopic techniques such as UV–visible, ATR-IR, Raman and XPS. The study confirmed the formation, the structure, the size and shape of particles and morphology of PANI by using analytical techniques namely, SAED, SEM and TEM. An important observation is that doping with HCl significantly improves the nanorod formation at the interface. The doped PANI electrode exhibits a higher area with rectangular shape in CV cycle and better cycle stability when compared with the performance of undoped PANI films. We believe that the results of these studies can give valuable leads to manoeuvre formation of PANI films with desired morphology for various applications.

Nickel‐Catalyzed α‐Carbonylalkylarylation of Vinylarenes: Expedient Access to γ,γ‐Diarylcarbonyl and Aryltetralone Derivatives

We report a Ni‐catalyzed regioselective α‐carbonylalkylarylation of vinylarenes with α‐halocarbonyl compounds and arylzinc reagents. The reaction works with primary, secondary, and tertiary α‐halocarbonyl molecules, and electronically varied arylzinc reagents. The reaction generates γ,γ‐diarylcarbonyl derivatives with α‐secondary, tertiary, and quaternary carbon centers. The products can be readily converted to aryltetralones, including a precursor to Zoloft, an antidepressant drug.