An Efficient One‐Pot Four‐Component Synthesis of Functionalized Imidazo[1,2‐a]pyridines

An efficient one‐pot four‐component protocol for the synthesis of imidazo[1,2‐a]pyridines was developed by condensing ethane‐1,2‐diamine ( 2 ), 1,1‐bis(methylthio)‐2‐nitroethene ( 1 ), aldehydes 3 , and activated methylene compounds in EtOH under reflux conditions (Tables 1–3). The features of this procedure are operational simplicity, good yields of products, in situ preparation of heterocyclic ketene aminals (HKA), and catalyst‐free conditions.     

Electrochemical Determination of Dextromethorphan on Reduced Graphene Oxide Modified Screen‐Printed Electrode after Electromembrane Extraction

In this paper, electromembrane extraction coupled with differential pulse voltammetry (DPV) on a reduced graphene oxide modified screen‐printed carbon electrode (RGO‐SPCE) for the determination of dextromethorphan (DXM) in urine and plasma has been described. DXM migrated from 4 mL of a donor phase across a thin layer of 2‐nitrophenyl octyl ether (NPOE) immobilized in the pores of a porous hollow fiber, into a 20 µL acceptor phase (HCl) present inside the lumen of the fiber. Then, 15 µL of a 0.1 M NaOH solution was added to the acceptor phase and the mixture was analyzed using DPV.     

One-pot synthesis of 1,2,3-triazole linked dihydropyrimidinones via Huisgen 1,3-dipolar/Biginelli cycloaddition

The combination of the Biginelli reaction with click chemistry has been used for the one-pot synthesis of 1,2,3-triazole linked dihydropyrimidinones from azides, aromatic aldehydes containing a propargyl ether group, urea, and 1,3-dicarbonyl compounds using Cu(OAc)₂/sodium ascorbate as catalyst in acetic acid under mild reaction conditions.     

Direct synthesis of nitrogen-doped graphene on platinum wire as a new fiber coating method for the solid-phase microextraction of BXes in water samples: Comparison of headspace and cold-fiber headspace modes

In this work, a new solid-phase microextraction fiber was prepared based on nitrogen-doped graphene (N-doped G). Moreover, a new strategy was proposed to solve problems dealt in direct coating of N-doped G. For this purpose, first, Graphene oxide (GO) was coated on Pt wire by electrophoretic deposition method. Then, chemical reduction of coated GO to N-doped G was accomplished by hydrazine and NH₃. The prepared fiber showed good mechanical and thermal stabilities. The obtained fiber was used in two different modes (conventional headspace solid-phase microextraction and cold-fiber headspace solid-phase microextraction (CF-HS-SPME)). Both modes were optimized and applied for the extraction of benzene and xylenes from different aqueous samples. All effective parameters including extraction time, salt content, stirring rate, and desorption time were optimized. The optimized CF-HS-SPME combined with GC-FID showed good limit of detections (LODs) (0.3–2.3 μg/L), limit of quantifications (LOQs) (1.0–7.0 μg/L) and linear ranges (1.0–5000 μg/L). The developed method was applied for the analysis of benzene and xylenes in rainwater and some wastewater samples.     

New Convenient Five‐Component One‐Pot Synthesis of 3‐Alkyl‐6‐amino‐1,4‐dihydro‐4‐{[(1,2,3‐triazol‐4‐yl)methoxy]phenyl}pyrano[2,3‐c]pyrazole‐5‐carbonitrile Derivatives

3‐Alkyl‐6‐amino‐1,4‐dihydro‐4‐{[(1,2,3‐triazol‐4‐yl)methoxy]phenyl}pyrano[2,3‐c]pyrazole‐5‐carbonitrile derivatives were synthesized through a one‐pot five‐component condensation reaction.     

Unified Model of Drainage and Imbibition in 3D Fractionally Wet Porous Media

We develop a grain-based model for capillarity controlled displacement within 3D fractionally wet porous media. The model is based on a novel local calculation of the position of stable fluid–fluid interfaces in contact with multiple spherical grains of arbitrary contact angles. The interface is assumed to be locally spherical between bulk phases; the interface is assumed to be toroidal between pairs of grains (surfaces of pendular rings). Because the calculation of interface position is entirely local and grain-based, it provides a single, generalized, geometric basis for computing pore-filling events during drainage as well as imbibition with both Melrose events (merging of two interfaces) and Haines events (geometric instability). The model is validated against a series of drainage/imbibition experiments (oil/water) on fractionally wet porous media prepared by mixing oil-wet grains with water-wet grains.     

<Emphasis Type="Italic">N</Emphasis>-Heterocyclic carbene–copper complex supported on ionic liquid-modified graphene oxide: versatile catalyst for synthesis of (i) 1,2,3-triazole and (ii) propargylamine derivatives

A N-heterocyclic carbene–copper complex grafted on graphene oxide with an ionic liquid framework was prepared. The synthesis of (i) 1,2,3-triazole derivatives by ‘Click reaction’ and (ii) propargylamine derivatives by ‘A³ coupling reaction’ in aqueous media by this new catalyst were all successfully accomplished. The catalyst is characterized using infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetric analysis and energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and elemental analysis. The catalyst is reused in the ten reaction cycles without considerable loss of catalytic activity.

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Multivariate curve resolution-alternating least squares (MCR-ALS) and central composite experimental design for monitoring and optimization of simultaneous removal of some organic dyes

In this work, multivariate curve resolution-alternating least squares (MCR-ALS) has been applied to resolve and study the simultaneous degradation of three toxic organic dyes using Fenton reaction. Second-order kinetic-spectrophotometric data in the simultaneous degradation of malachite green, crystal violet and methylene blue were analyzed by MCR analysis to get their concentration profiles and calculate their degradation factors. The effect of three parameters (Fe²⁺, H₂O₂ concentration and initial pH) and their possible interaction in the simultaneous degradation of mentioned dyes were studied and optimized using experimental design and response surface method. Acquiring second-order data makes possible the analysis and study of the studied dyes in the gray systems which is termed as second-order advantage in the literatures. The prominent point of this work is the combination of second-order data and response surface methodology.     

Copper nanoparticles incorporated on a mesoporous carbon nitride,an excellent catalyst in the Huisgen 1,3‐dipolar cycloaddition and N‐arylation of N‐heterocycles

Cu nanoparticles with average particles size around 10 nm were incorporated on the surface of a mesoporous carbon nitride support. The XRD and N₂ adsorption isotherms show that it maintains a hexagonal mesoporous structure with a high surface area (600.03 m² g^?1). The embedded Cu nanoparticles exhibit extremely high catalytic performance in two different kinds of organic reactions. The Huisgen 1,3‐dipolar cycloaddition and N‐arylation of N‐heterocycles were all accomplished.     

Application of a new fiber coating based on electrochemically reduced graphene oxide for the cold‐fiber headspace solid‐phase microextraction of tricyclic antidepressants

A new fiber based on the electrochemical reduction of graphene oxide was prepared on a copper wire for solid‐phase microextraction (SPME) applications. The prepared fiber was used for the SPME and gas chromatographic analysis of tricyclic antidepressants (TCADs), including amitriptyline, trimipramine, and clomipramine. The feasibility of direct‐immersion and headspace modes of SPME for the determination of TCADs was studied. The effects of four parameters including pH, salt content, extraction temperature with and without cooling the fiber, and extraction time were investigated. The comparison showed that headspace cold fiber SPME results in the best outcome for the extraction of TCADs. Under the optimized conditions of this mode, the calibration curves were linear between 2.0 and 500 ng/mL and the detection limits were between 0.30 and 0.53 ng/mL. The intraday and interday RSDs obtained at 20 ng/mL (n = 5), using a single fiber, were 5.5–9.0 and 7.5–9.8, respectively. The fiber to fiber repeatability (n = 4), expressed as the RSD, was between 12.8 and 13.2% at a 20 ng/mL concentration level. The method was successfully applied to the analysis of TCADs in plasma samples showing recoveries from 73 to 96%.