Regioselectivity in palladium-catalyzed C-H activation/oxygenation reactions

[reaction: see text] Palladium-catalyzed directed C-H activation/oxygenation reactions have been explored in a series of meta-substituted aryl pyridine and aryl amide derivatives. These transformations tolerate a diverse array of electron-donating and electron-withdrawing meta-substituents and generally proceed with high levels of regioselectivity for functionalization of the less sterically hindered ortho-C-H bond.     

Nickel-catalyzed intramolecular C–H arylation using aryl pivalates as electrophiles

This paper describes a method for nickel catalyzed intramolecular C–H arylation using aryl pivalates as electrophiles. The transformation is efficient for the synthesis of diverse electronically and sterically differentiated dibenzofurans. Additionally, the method could be expanded toward the synthesis of carbazoles. Preliminary mechanistic studies of the transformation are also described.     

A specific HPLC-UV method for the determination of cysteine and related aminothiols in biological samples

We present a highly selective and sensitive method for the determination of cysteine (Cys) and related aminothiols that play important roles in health and disease. The key step in the analysis is treatment with 1,1′-thiocarbonyldiimidazole (TCDI) that rapidly and quantitatively reacts with both the amino and thiol groups to form stable cyclic dithiocarbamates with intense UV absorption. Cys, homocysteine (hCys), and cysteinylglycine in plasma (75 μl), urine (100 μl), or cerebrospinal fluid (100–500 μl) were determined by separating and measuring their cyclic derivatives by a high performance liquid chromatograph (HPLC) connected to a UV detector. The chromatograms obtained using TCDI contained fewer and better-resolved peaks than those produced by less selective reagents used previously. Using chemically similar 2-methylcysteine as the internal standard, high repeatability (variation of less than 5%) and adequate sensitivity to detect small increments (10–20%) in the concentrations of cysteinylglycine and hCys were achieved. The HPLC method can also be modified to measure -penicillamine (greater than 0.8 μM) in plasma (50 μl) providing a potential method to monitor plasma levels of this drug in patients.     

Synthesis,characterization and biological evaluation of purine nucleoside analogues

We present a convenient route for the synthesis of C6-amino-C5′-N-cyclopropyl carboxamido-C2-alkynylated purine nucleoside analogues 11a–g via Sonogashira coupling reaction. The nine step synthesis is easy to perform, employing commercially available reagents. Compound 9 is used as key intermediate for the synthesis of analogues 11a–g. Synthetic intermediates and final products are appropriately characterized by IR, ¹H NMR, ¹³C NMR and Mass. The modified nucleoside analogues 11a–g is evaluated for in vitro anticancer activity against MDA-MB-231 and Caco-2 cell lines. Screening data reveals that compounds 11b and 11e displayed potent IC₅₀ value of 7.9, 6.8 µg/mL respectively against MDA-MB-231 and of 7.5, 8.3 µg/mL respectively against Caco-2 than the standard drug doxorubicin, thus establishing the potential anti-cancer properties of these newer derivatives.     

Physical properties of LiMn2O4 spinel prepared at moderate temperature

A moderate-temperature method of preparation of the spinel LiMn₂O₄ was developed around 500 °C. Physical features of the products were identified by X-ray photoelectron spectroscopy, X-ray diffractometry, Raman scattering and FTIR spectroscopy. The electronic conductivity of LiMn₂O₄ has been studied as a function of annealing temperature. The product LiMn₂O₄ is identified as a micron-sized powder and analysis of the local environment is in good accordance with the classical structural model of Fd3m space group. LiMn₂O₄ exhibits an electrical conductivity of 1.9×10⁻⁵ S/cm at room temperature with an activation energy of 0.16 eV which corresponds to an electron hopping mechanism between the two charge states of Mn³⁺ and Mn⁴⁺ ions. A first-order phase transition is observed at 292 K.     

Cosmological models with constant deceleration parameter in Nordtvedt’s theory

Exact solutions of the field equations of Nordtvedt’s theory for spatially flat FRW models with constant deceleration parameter have been obtained. Singular solutions with (i) power-law (ii) exponential expansion have been studied in Nordtvedt’s theory where the coupling parameterω is a function of the scalar fieldφ.     

Cosmological Models with Bulk Viscosity in the Presence of Particle Creation

The effect of bulk viscosity, with a time varying bulk viscous coefficient, on the evolution of frw models is investigated in the context of open thermodynamic systems, which allows for particle creation. It is seen that, by choosing an appropriate function for particle creation, the models presented exhibit non-singular beginnings.     

Calibration transfer between electronic nose systems for rapid In situ measurement of pulp and paper industry emissions

Electronic nose systems when deployed in network mesh can effectively provide a low budget and onsite solution for the industrial obnoxious gaseous measurement. For accurate and identical prediction capability by all the electronic nose systems, a reliable calibration transfer model needs to be implemented in order to overcome the inherent sensor array variability. In this work, robust regression (RR) is used for calibration transfer between two electronic nose systems using a Box–Behnken (BB) design. Out of the two electronic nose systems, one was trained using industrial gas samples by four artificial neural network models, for the measurement of obnoxious odours emitted from pulp and paper industries. The emissions constitute mainly of hydrogen sulphide (H₂S), methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) in different proportions. A Box–Behnken design consisting of 27 experiment sets based on synthetic gas combinations of H₂S, MM, DMS and DMDS, were conducted for calibration transfer between two identical electronic nose systems. Identical sensors on both the systems were mapped and the prediction models developed using ANN were then transferred to the second system using BB–RR methodology. The results showed successful transmission of prediction models developed for one system to other system, with the mean absolute error between the actual and predicted concentration of analytes in mg L⁻¹ after calibration transfer (on second system) being 0.076, 0.1801, 0.0329, 0.427 for DMS, DMDS, MM, H₂S respectively.     

Evaluation of suitable methods to synthesize battery active LiNiO2

A detailed investigation has been made on the possibility of synthesizing LiNiO₂ through different methods using a variety of precursors and varying heat treating conditions with a view to identify a suitable method to synthesize LiNiO₂ and to understand the influence of synthesis method and the nature of the precursors towards the performance characteristics of LiNiO₂. In this regard, four different methods,viz., solid-state, organic precursors, solution combustion and microwave methods were adopted involving suitable combinations of lithium and nickel precursors. All the synthesized compounds were characterized for their phase purity (PXRD), local cation environment (FTIR), particle size, surface area, and electrochemical behavior (charge-discharge). Based on the results obtained especially from PXRD and charge-discharge studies, the “all-hydroxide” precursors of Li and Ni were found to be effective in yielding battery active LiNiO₂ as far as the solid-state and microwave-assisted methods are concerned. With regard to solution synthesis methods, citrate precursor and the combustion method involving hydrazine hydrate fuel were found to yield better performing LiNiO₂, compared to the rest of the combinations attempted in both categories. However, among the wet chemistry based solution methods the present study recommends solution combustion method with hydrazine hydrate as fuel to synthesize electrochemically active LiNiO₂ as it was found to exhibit a stable discharge capacity of 177 mAh/g at least up to 20 cycles.