Expeditious one-pot multicomponent microwave-assisted green synthesis of substituted 2-phenyl Quinoxaline and 7-bromo-3-(4-ethylphenyl) pyrido[2,3-b]pyrazine in water–PEG and water–ethanol

An eco-friendly, expeditious one-pot multicomponent synthesis of substituted 2-phenyl quinoxaline and 7-bromo-3-(4-ethylphenyl) pyrido[2,3-b]pyrazine 4a–k in water–ethanol from easily available starting materials as acetophenone 1, succinamide 2, aromatic amine 3, in situ-generated α-iodo acetophenone from acetophenone, succinamide and catalyzed by silver iodide in combination with green solvent polyethylene glycol-400 and water (2:1) under microwave irradiation. The newly developed protocol with excellent yield of products in very short time of reaction by avoiding the use of lacrimatic α-chloro and α-bromocarbonyl compounds, volatile, toxic organic hazardous solvents, and reagents is the advantage of this research work. The final products were confirmed by their characterization data such as FTIR, ¹H NMR, ¹³C NMR, Mass, HRMS and were compared with its reported method.     

Rapid and efficient one-pot microwave-assisted synthesis of 2-phenylimidazo[1,2-a]pyridines and 2-phenylimidazo[1,2-a]quinoline in water–PEG-400

An effective, expeditious, environmentally benign one-pot synthesis of 2-phenylimidazo[1,2-a]pyridines and 2-phenylimidazo[1,2-a]quinoline from easily available starting materials as aromatic carbonyl compound, 2-amino pyridine, succinamide, and in situ generated α-iodo acetophenone in combination with green solvent PEG-400 and water (2:1) under microwave irradiation. The newly developed protocol with excellent yield of product in very short time of reaction by avoiding the use of lachrymatric α-chloro and α-bromocarbonyl compounds, volatile, toxic organic and hazardous solvents, reagents is the advantage of this research work. The final products were confirmed by their characterization data such as ¹H NMR, ¹³C NMR, high resolution mass spectrometry (HRMS) and were compared with its reported method.     

Zinc(II)‐Catalyzed Intermolecular Hydrative Aldol Reactions of 2‐En‐1‐ynamides with Aldehydes and Water to form Branched Aldol Products Regio‐ and Stereoselectively

This work describes zinc(II)‐catalyzed hydrative aldol reactions of 2‐en‐1‐ynamides with aldehydes and water to afford branched aldol products regio‐ and stereoselectively. The anti and syn selectivity can be modulated by the sizes of sulfonamides to yield E‐ and Z‐configured zinc(II) dienolates selectively. This new reaction leads to enantiopure aldol products by using a cheap chiral sulfonamide. The mechanistic analysis reveals that the sulfonamide amides of the substrates can trap a released proton to generate dual acidic sites to activate a carbonyl allylation reaction.     

Molecular‐Recognition‐Assisted pKa Shifts and Metal‐Ion‐Induced Fluorescence Regeneration in p‐Sulfonatocalix[6]arene‐Encapsulated Acridine

The host–guest interactions of cationic (AcH⁺) and neutral (Ac) forms of the dye acridine with the macrocyclic host p‐sulfonatocalix[6]arene (SCX6) were investigated by using ground‐state absorption, steady‐state and time‐resolved fluorescence, and NMR measurements. The cationic form undergoes significant complexation with SCX6 (K_eq=2.5×10⁴ M ^?1), causing a sharp decrease in the fluorescence intensity and severe quenching in the excited‐state lifetime of the dye. The strong binding of the AcH⁺ form of the dye with SCX6 is attributed to ion–ion interactions involving the sulfonato groups (SO₃^?) of SCX6 and the positively charged AcH⁺ at pH of approximately 4.3. Whereas, the neutral Ac form of the dye undergoes weak complexation with SCX6 (K_eq=0.9×10³ M ^?1) and the binding constant is lowered by one order of magnitude compared with that of the SCX6–AcH⁺ system. The strong affinity of SCX6 to the protonated form leads to a large upward pK_a shift (≈2 units) in the dye. In contrast, strong emission quenching upon SCX6 interaction and the regeneration of fluorescence intensity of the dye in the presence of Gd³⁺ through competitive binding have also been demonstrated.     

New synthetic strategy for Friedlander condensation of 4-amino-2-oxo-2H-chromene-3-carbaldehyde by heterogeneous catalysis

Chromenopyridines are an important class of compound because of their diverse biological activities. In the present work, we have developed convenient route for the synthesis of chromeno[4,3-b] pyridine derivatives ( 3a – e , 5a – e , and 7a – d ) by Friedlander condensation of 4-amino-2-oxo-2H-chromene-3-carbaldehyde with various active methylene compounds. We have used mixed metal oxide catalyst such as nanomaterial Zinc titanate. The reaction was carried out for various solvent systems, also we have altered the concentration of the catalyst. The 2-propanol/water solvent system and 5 mol% catalyst concentration are best as far as yield and rate of reaction are concerned. The structures of the synthesized compounds were confirmed by ¹H NMR, ¹³C NMR, mass spectra, and elemental analysis.     

Axisymmetric response of a cracked fiber in matrix

Solved is the problem of a penny-shaped crack in a fiber surrounded by a finite radius matrix subjected to uniform axial strain. The stress intensity factor at the crack edge and the maximum stresses at the interface are examined. These quantities depend on the elastic moduli of the fiber and the matrix, the interface properties, the fiber volume fraction and the crack length. The axisymmetric results are compared with those in plane extension. They are discussed in relation to possible crack growth directions depending on assumed interface strength.     

阳离子配比对共沉淀法制备的镍锌铁陵盐纳米颗粒的结构和磁性的影响

Ferrites having general formula Ni1-xZnxFe2O4 with x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7 were prepared by wet chemical co-precipitation method. The structural and magnetic properties were studied by means of X-ray diffraction, magnetization, and AC susceptibility measurements. The X-ray analysis confirmed the single-phase formation of the samples. The lattice parameter obtained from XRD data was found to increase with Zn content x. The cation distribution was studied by X-ray intensity ratio calculations. Magnetization results exhibit collinear ferrimagnetic structure for x<0.4, and which changes to non-collinear for x>0.4. Curie temperature TC obtained from AC susceptibility data decreases with increasing x.     

Nano-dimensional iron tungstate for super high energy density symmetric supercapacitor with redox electrolyte

Journal of Solid State Electrochemistry - In present work, we have developed 2.0 V symmetric supercapacitor with rationally prepared iron tungstate (FeWO4) nanoparticles as electrodes and...     

Chiral separation and thermodynamic investigation of WCK 3023: A novel oxazolidinone antibacterial agent,application to pre‐clinical pharmacokinetic study

A chiral liquid chromatographic method was developed and validated for the quantification of R‐enantiomer impurity (RE) in WCK 3023 (S‐enantiomer), a new drug substance. The separation was achieved on Chiralpak IA (amylose‐based immobilized chiral stationary phase), using a mobile phase consisting of n‐hexane–ethanol–trifluoroacetic acid (70:30:0.2, v/v/v) at a flow rate of 1.0 mL/min. The method was extensively validated for the quantification of RE in WCK 3023 and proved to be robust. For RE the detector response was linear over the concentration range of 0.11–5 μg/mL. The limit of quantitation and limit of detection for RE were 0.11 and 0.04 μg/mL respectively. Average recovery of the RE was in the range of 98.11–99.55%. The developed method was specific, sensitive, precise and accurate for quantitative determination of RE in WCK 3023. The impact of thermodynamic parameters on the chiral separation was evaluated. The method was employed for controlling the enantiomeric impurity in the lots of WCK 3023 used for pre‐clinical studies. The method was successfully applied to evaluate the possible conversion of WCK 3023 to RE in rat serum samples during pre‐clinical pharmacokinetic studies.     

Forced degradation studies of mangiferin and berberine by high-performance thin-layer chromatography

JPC – Journal of Planar Chromatography – Modern TLC - Since ancient times, herbal drugs have been used by different cultures throughout the world to treat illness. With the upgrading of...