Aqueous media preparation of 2-amino-4,6-diphenylnicotinonitriles using cellulose sulfuric acid as an efficient catalyst

A convenient approach to the synthesis of 2-amino-4,6-diphenylnicotinonitriles via four-component reaction of aromatic aldehydes, acetophenone derivatives, malononitrile and ammonium acetate is described. The reactions were done in water as solvent using cellulose sulfuric acid as catalyst. This simple protocol offer advantages such as shorter reaction times, simple work-up procedure, excellent yields and catalyst recovery.     

35Cl NQR frequency and spin lattice relaxation study in 3,4-dichloronitrobenzene as a function of temperature and pressure

³⁵Cl NQR frequency and spin lattice relaxation time in 3,4-dichloronitrobenzene have been measured as a function of temperature and pressure. Two NQR signals were observed in the temperature range 77 to 300 K and pressure up to 5.1 kbar at 300 K. The contributions to the relaxation from the torsional motion of the molecule and reorientational motion of the nitro group have been analyzed on the basis of the Woessner and Gutowsky model. The temperature dependence of the average torsional lifetimes of the molecules, transition probabilities, and the activation energy for the reorientation of the nitro group was estimated. The pressure dependence of the NQR frequency in 3,4-Dichloronitrobenzene shows a nonlinear increase in NQR frequency with increase in pressure, indicating increased contribution from the static effects at higher pressures. A thermodynamic analysis of the data was carried out to determine the constant-volume temperature coefficients of the NQR frequency. The spin–lattice relaxation was found to be weakly dependent on pressure.     

Development and validation of liquid chromatography–tandem mass spectrometry method for the estimation of a potential genotoxic impurity 2-(2-chloroethoxy)ethanol in hydroxyzine

2-(2-Chloroethoxy)ethanol (CEE) belongs to the so-called cohort of concerns which were classified as highly potent mutagenic carcinogens by the World Health Organization. It is widely used in the synthesis of the essential anti-histamine drug hydroxyzine. In addition, it is used as a primary solvent in dyes, nitrocellulose, paints, inks and resins. Owing to its potential genotoxicity, an efficient liquid chromatography–tandem mass spectrometry method was developed for the quantitative estimation of CEE traces in an active pharmaceutical ingredients and in tablet dosage forms of hydroxyzine-free base. The chromatographic separation was achieved on a C₁₈ column using a gradient elution mode with a binary solvent system (ammonium formate and methanol). Mass detection was performed for CEE using a positive mode with selected ion monitoring technique at m/z value of [M + NH₄]⁺. The developed method was validated as per the International Conference on Harmonizaiton guidelines. The quantitation limit, linearity and recoveries were found to be 0.56 ppm, 0.56–7.49 ppm (r² > 0.9985) and 93.6–99.3%, respectively. The proposed method was highly compatible and was used effectively to estimate CEE traces in different stages of drug synthesis and in tablet dosage forms of hydroxyzine for routine and stability testing.     

Storage performance of LiFe<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript> nanoplates (<Emphasis Type="Italic">x </Emphasis>= 0, 0.5, and 1)

Although LiFePO₄ (LFP) is considered to be a potential cathode material for the lithium-ion batteries, its rate performance is significantly restricted by sluggish kinetics of electrons and lithium ions. Several attempts have been made so far to improve the performance of LiFePO₄ by reducing the grain size, doping with aliovalent atoms, and coating conductive materials such as carbon or RuO₂. We report here synthesis of LFP nanoplates by solvothermal method, tailoring the thickness as well as carbon coverage at surfaces to explore their influence on the storage performance. Due to the fact that Li⁺ ion diffuses along the b-axis, solvothermal method was aimed to control the thickness of nanoplates across the b-axis. We synthesized several nanoplates with various plate thicknesses along b-axis; among those, nanoplates of LFP with ～30-nm-thick b-axis having thin (2–5 nm) and uniform layer of carbon coating exhibits high storage capacity as well as high rate performances. Thus, a favorable morphology for LiFePO₄ has been achieved via solvothermal method for fast insertion/extraction of Li⁺ as compared to spherical nanoparticles of carbon-coated LFP. Galvanostatic cycling shows a capacity of 164?±?5 mAh g^?1 at 0.1 C rate, 100?±?5 mAh g^?1 at 10 C rate, and 46?±?5 mAh g^?1 at 30 C rate, with excellent capacity retention of up to 50 cycles. Further attempts have been made to synthesize LiMnPO₄ (LMP) as well as Li(Fe_1???x Mn _x )PO₄/C (x?=?0.5) nanoplates using solvothermal method. Although LiMnPO₄ does not exhibit high storage behavior comparable with that of LiFePO₄, the mixed systems have shown an impressive storage performance.     

Reusable silica-bonded S-sulfonic acid catalyst for three-component synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromenes and 2-amino-4H-pyrans in aqueous ethanol

Silica-bonded S-sulfonic acid (SBSSA)-catalyzed, facile, one-pot, three-component coupling of 5,5-dimethyl-1,3-cyclohexanedione (dimedone) or 5,5-dimethyl-1,3-cyclohexanedione, aromatic aldehydes, and malononitrile at reflux temperature is described for preparation of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene derivatives. 2-Amino-3-cyano-6-methyl-4-phenyl-4H-pyran-5-ethylcarboxylate derivatives can also be prepared in good yield under the same experimental conditions by use of ethyl acetoacetate, aldehydes, and malononitrile. The catalyst, silica-bonded S-sulfonic acid, was reused and recycled without any loss of activity or product yield.     

Silica-supported perchloric acid (HClO4–SiO2): a mild, reusable and highly efficient heterogeneous catalyst for multicomponent synthesis of 1,4-dihydropyridines via unsymmetrical Hantzsch reaction

Facile synthesis of some 1,4-dihydropyridine derivatives via Hantzsch reaction of 5,5-dimethyl-1,3-cyclohexanedione (dimedone), 1,3-diphenyl-2-propen-1-one derivatives and ammonium acetate under solvent-free condition in the presence of silica-supported perchloric acid (HClO₄–SiO₂) is described. The catalyst is easily prepared, stable, reusable and efficient under the reaction conditions.     

Structural and Magnetic properties of Cr-diffused CdTe nanocrystalline thin films deposited by electron beam evaporation

Cr-diffused cadmium telluride (CdTe) thin films with different Cr content were prepared using electron beam evaporation method at a substrate temperature of 373 K followed by annealing at 573 K. The structures, composition, chemical and magnetic properties of the prepared films were studied using appropriate techniques. The X-ray diffraction spectra showed a predominant (1 1 1) reflection corresponding to the zinc blende structure of CdTe. Increase of lattice parameter with increase in Cr content has been observed. The cross-sectional HRSEM images displayed a columnar grain growth in the films. EDAX data exposed the presence of Cr, Cd and Te with near stoichiometry. The Raman spectra revealed emission peaks corresponding to A1, TO and LO modes of CdTe showing gradual shift in peak position and decreased intensity confirming the incorporation of Cr into CdTe host lattice. M–H plots displayed a clear well-defined room temperature ferromagnetic hysteresis loop with increase in Cr content.