Novel One‐Pot Synthesis of Functionalized Quinolines from Isocyanides,Aniline, and Acetylene Dicarboxylate via Cu‐Catalyzed Intramolecular C─H Activation Reactions

The one‐pot synthesis of a novel class of substituted quinoline derivatives with good yields is achieved via the Cu‐catalyzed intramolecular C─H activation reaction between isocyanides, aniline, and acetylene dicarboxylate in MeCN at room temperature. The existence of one‐pot conditions, availability of a starting material‐catalyst, the absence of column chromatography, and a high yield of products are among the advantages of this method. The structures are confirmed spectroscopically (¹H NMR and ¹³C NMR, IR, and EI‐MS) and through elemental analyses.     

Synthesis of Pyrano[3,2‐c]quinoline‐3‐carboxaldehyde and 3‐(Ethoxymethylene)‐pyrano[3,2‐c]quinolinone and Their Chemical Behavior toward Some Nitrogen and Carbon Nucleophiles

Synthesis of novel 3‐(ethoxymethylene)‐pyrano[3,2‐c]quinolinone and pyrano[3,2‐c]quinoline‐3‐carboxaldehyde was accomplished efficiently via a simple method. These two scaffolds were used as precursors to afford new biologically interesting products in good yield and short reaction times. The chemical reactivity of ethoxy methylene 2 and carboxaldehyde 3 toward different nucleophilic reagents was studied. Structures of the new synthesized compounds were elucidated by their analytical and spectral data.     

Thermodynamic and kinetic studies of the retro-Diels-Alder reaction of 1,4-cyclohexadiene, 4H-pyran 4H-thiopyran, 1,4-dioxine,and 1,4-dithiine: a theoretical investigation

Theoretical studies of the retro-Diels-Alder reaction of 1,4-cyclohexadiene, 4H-pyran 4H-thiopyran, 1,4-dioxine, and 1,4-dithiine in the gas phase were carried out using DFT methods at the B3LYP/6–311?+?G(d,p) levels of theory. The barrier height (ΔE^?) and thermodynamic parameters (ΔG^? and ΔH^?) were estimated. The progress of the reactions was followed by means of the Wiberg bond indices. The synchronicity values of the reactions were calculated. The kinetic parameters were calculated for both reactions in 300–1200-K temperature range. Also, fitted equations to the gas phase Arrhenius equation were determined. Effect of the character and number of heteroatoms were illustrated on the thermodynamic and kinetic parameters.

     

Modification of WS2 nanosheets with beta-cyclodextrone and N-isopropylacrylamide polymers for tamoxifen adsorption and investigation of in vitro drug release

In this research, tungsten disulfide (WS₂) nanosheets were modified with beta-cyclodextrone (βCD) N-isopropylacrylamide polymers (NIPAAP) for adsorption of tamoxifen (TAM) drug. The synthesized WS₂/βCD/NIPAAP samples were characterized by field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) analyses. The adsorption experiments of TAM on WS₂/βCD/NIPAAP were performed as a function of pH, reaction contact time, temperature and drug concentration. The adsorption kinetic data were well fitted to the pseudo-second-order model. Also, the equilibrium data were well described by Langmuir isotherm model. The maximum adsorption capacity of WS₂/βCD/NIPAAP for TAM drug was found to be 62.0 mg/g. The results of regeneration tests showed that the synthesized WS₂/βCD/NIPAAP adsorbent can be easily reused after 6 cycles of adsorption–desorption. Furthermore, TAM drug release was investigated in a simulated system with pH 7.4 at different temperatures. The results showed that the release of TAM drug from WS₂/βCD/NIPAAP carrier at 50 °C and 37 °C was greater than TAM release at 25 °C. Also, the experimental data of drug release were studied by Higuchi, Ritger-Peppas, zero-order and first-order models. The release data were well fitted to the zero-order model indicating a case II transport. The results showed a high stability for TAM drug.

     

A theoretical investigation on decarboxylation mechanism of antibiotic para-aminosalicylic acid to highly toxic form meta-aminophenol

Structural Chemistry - The antibiotic para-aminosalicylic acid (PAS) is decomposed into its decarboxylated product, meta-aminophenol, with a series of toxicity symptoms including hemolytic anemia....     

Determination of chlorophenols in water samples using simultaneous dispersive liquid-liquid microextraction and derivatization followed by gas chromatography-electron-capture detection

Simultaneous dispersive liquid-liquid microextraction (DLLME) and derivatization combined with gas chromatography-electron-capture detection (GC-ECD) was used to determine chlorophenols (CPs) in water sample. In this derivatization/extraction method, 500 microL acetone (disperser solvent) containing 10.0 microL chlorobenzene (extraction solvent) and 50 microL acetic anhydride (derivatization reagent) was rapidly injected by syringe in 5.00 mL aqueous sample containing CPs (analytes) and K(2)CO(3) (0.5%, w/v). Within a few seconds the analytes derivatized and extracted at the same time. After centrifugation, 0.50 microL of sedimented phase containing enriched analytes was determined by GC-ECD. Some effective parameters on derivatization and extraction, such as extraction and disperser solvent type and their volume, amount of derivatization reagent, derivatization and extraction time, salt addition and amount of K(2)CO(3) were studied and optimized. Under the optimum conditions, enrichment factors and recoveries are in the range of 287-906 and 28.7-90.6%, respectively. The calibration graphs are linear in the range of 0.02-400 microg L(-1) and limit of detections (LODs) are in the range of 0.010-2.0 microg L(-1). The relative standard deviations (RSDs, for 200 microg L(-1) of MCPs, 100 microg L(-1) of DCPs, 4.00 microg L(-1) of TCPs, 2.00 microg L(-1) of TeCPs and PCP in water) with and without using internal standard are in the range of 0.6-4.7% (n=7) and 1.7-7.1% (n=7), respectively. The relative recoveries of well, tap and river water samples which have been spiked with different levels of CPs are 91.6-104.7, 80.8-117.9 and 83.3-101.3%, respectively. The obtained results show that simultaneous DLLME and derivatization combined with GC-ECD is a fast simple method for the determination of CPs in water samples.     

Cyclodextrin Host‐Guest Recognition Approach for Simultaneous Quantification and Voltammetric Studies of Levodopa and Carbidopa in Pharmaceutical Products

An electrochemical sensor for simultaneous quantification of Levodopa (L‐dopa) and Carbidopa (C‐dopa) using a β‐cyclodextrin/poly(N‐acetylaniline) (β‐CD/PNAANI) modified carbon paste electrode has been developed. Preconcentrating effect of β‐CD as well as its different inclusion complex stability with L‐dopa and C‐dopa was used to construct an electrochemical sensor for quantification of these important analytes. The overlapping anodic peaks of L‐dopa and C‐dopa at 810 mV on bare carbon paste electrode resolved in two well‐defined voltammetric peaks at 450 and 880 mV vs. Ag/AgCl, respectively, with a drastic enhancement of the anodic peak currents. Under optimized conditions, linear calibration curves were obtained in the ranges of 0.5–117 µM and 1.6–210 µM with detection limits down to 0.2 and 0.8 µM for L‐dopa and C‐dopa, respectively. The proposed electrode was successfully applied for the determination of L‐dopa /C‐dopa in pharmaceutical formulations and the results were in close agreement with the labeled values.     

Synthesis and Application of Co‐Poly(2‐hydroxyethyl methacrylate‐ethylene dimethacrylate) Coupled with Alizarin Yellow for Preconcentration and Determination of Lead in Water Samples by Flame Atomic Absorption Spectrometry

Poly(2‐hydroxyethyl methacrylate‐ethylene dimethacrylate) (PHEMA‐EDMA) beads were produced by free radical co‐polymerization of 2‐hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA). Then, metal complexing ligand alizarin yellow was covalently attached onto PHEMA‐EDMA beads. The resulting resin has been characterized by FT‐IR and studied for the preconcentration and determination of trace Pb(II) ion from solution samples. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 100 mg.g^‐1. The chelating resin can be reused for 20 cycles of sorption‐desorption without any significant change in sorption capacity. A recovery of 96% was obtained for the metal ion with 0.1 M nitric acid as eluting agent. The equilibrium adsorption data of Pb(II) on modified resin were analyzed by Langmuir and Freundlich models. Based on equilibrium adsorption data the Langmuir and Freundlich constants were determined 2.571 and 418.7 at pH 5 and 25 °C. The method was applied for lead ions determination from well water sample.     

Synthesis of nanocrystalline zinc manganese oxide by thermal decomposition of new dinuclear manganese(III) precursors

Nanocrystalline manganese-doped zinc oxide was synthesized by thermal decomposition of a zinc oxide sol with two new dinuclear manganese(III) complexes as precursor. Thermal analysis results indicated that the decomposition of manganese precursors occurred at 269 and 314 °C. X-ray structural analysis shows the presence of dimanganese core in the complexes and the binding of the ligands to the manganese(III) is through N₂O₂. The manganese-doped zinc oxide composite was characterized by means of X-ray diffraction, scanning electron microscopy, and UV–Vis spectroscopy. Structural properties of the composites elucidated that the manganese ions have substituted the zinc ions without changing the wurtzite structure of zinc oxide.