Template synthesis of a rare 14-membered macrocyclic complex using cadmium(II) ion as a collector

Journal of Inclusion Phenomena and Macrocyclic Chemistry - In this work, a new macrocyclic cadmium complex, [Cd(ACE)I]2[CdI4] (1); ACE: 1,3,6,10,12,15-hexaazatricyclo[13.3.1.16,10]eicosane, was...     

Highly sensitive kinetic spectrophotometric method for tramadol trace level detection and process optimization using response surface methodology

Tramadol is a centrally acting analgesic‐anodyne agent of high oral bioavailability. The tramadol contains a weakly absorbing chromophore in its molecule and it was determined by kinetic spectrophotometric method in pharmaceutical, urine, and blood plasma. Response surface methodology and the central composite design was applied to study the influence of maximum sensitivity, reagents concentration, temperature, and time on the UV–Vis spectrophotometry analysis of tramadol. Analysis of variance showed a high coefficient of determination (R²) value for responses, confirming adjustment of the models with experimental data. The change in absorbance was followed spectrophotometrically at 478 nm. Under optimum experimental conditions, calibration curve was linear over the range 0.45–100.0 μg/L of tramadol. The limit of detection was 0.12 μg/L of tramadol. The developed method was successfully applied for the determination of tramadol in real samples.     

Dust ion acoustic waves in non-thermal Cairns bi-Maxwellian plasma

Using kinetic theory approach, the dispersion relation ω_r and Landau damping rate γ for dust ion acoustic waves are investigated numerically and analytically in an unmagnetized collisionless dusty plasma considering Cairns distribution for electrons and ions in stationary dust particles background. The phase velocity and Landau damping rate are calculated in the limits v_td∥ < v_ti∥ << ω/k << v_te∥ . The electrons and ions non-thermality effects are incorporated via the non-thermality parameter (0 ≤ α < 1) . The real frequency ω_r and Landau damping rate γ of the mode in Cairns bi-Maxwellian distributed plasma are graphically shown to depend on plasma parameters namely non-thermality index α , ion to electron temperature ratio T_i∥/T_e∥ and the dust concentration parameter δ (=1 − ηZ_d) .     

Optimization of ethylene trimerization using catalysts based on TiCl3/half‐sandwich ligands

Catalytic trimerization of ethylene using three titanium‐based complexes [η⁵‐C₉H₆C(R)thienyl]TiCl₃ with various types of bridges (R = cyclo‐C₅H₁₀ ( C1 ), cyclo‐C₄H₈ ( C2 ) and (CH₃)₂ ( C3 )) has been successfully optimized and compared. First of all, three benzofulvene precursors, C₉H₆C(R), were synthesized. Then the corresponding indenyl‐based ligands were obtained via the reaction of the precursors with thienyllithium. The final titanium‐based catalysts display a distorted tetrahedral geometry, as expected for Ti(IV), with the ligand coordinated with a hemilabile behaviour. The structures of the compounds were confirmed on the basis of various analyses. The effect of catalyst concentration, ethylene pressure, reaction temperature and nature of the bridge as the significant factor affecting coordination and orientation of thienyl group relative to the metal centre on 1‐hexene (1‐C₆) productivity and selectivity was investigated. Results revealed that the bulky bridge groups such as cyclo‐C₅H₁₀ and cyclo‐C₄H₈ are appropriate for ethylene trimerization due to the closer coordination of sulfur atom with Ti, especially in cationic state, and catalyst C2 with cyclo‐C₄H₈ bridge exhibits moderate productivity equal to 785 kg 1‐C₆ (mol Ti)^?1 h^?1. According to the results, ethylene at a pressure of 10 bar, 50°C and 1.5 μmol of catalyst were selected as the best conditions for obtaining 1‐C₆ with high productivity and selectivity. The presence of indenyl enhances the thermal stability of the catalysts and preserves their activity in higher temperatures such as 50 and 80°C.     

Singlet-Oxygen-Induced Phospholipase A2 Inhibition: A Major Role for Interfacial Tryptophan Dioxidation

Several studies have revealed that various diseases such as cancer have been associated with elevated phospholipase A₂ (PLA₂) activity. Therefore, the regulation of PLA₂ catalytic activity is undoubtedly vital. In this study, effective inactivation of PLA₂ due to reactive species produced from cold physical plasma as a source to model oxidative stress is reported. We found singlet oxygen to be the most relevant active agent in PLA₂ inhibition. A more detailed analysis of the plasma-treated PLA₂ identified tryptophan 128 as a hot spot, rich in double oxidation. The significant dioxidation of this interfacial tryptophan resulted in an N-formylkynurenine product via the oxidative opening of the tryptophan indole ring. Molecular dynamics simulation indicated that the efficient interactions between the tryptophan residue and phospholipids are eliminated following tryptophan dioxidation. As interfacial tryptophan residues are predominantly involved in the attaching of membrane enzymes to the bilayers, tryptophan dioxidation and indole ring opening leads to the loss of essential interactions for enzyme binding and, consequently, enzyme inactivation.     

Facile preparation of highly stable and active hybrid palladium nanoparticles: effectual,reusable and heterogeneous catalyst for coupling reactions

Palladium nanoparticles were supported on a bed of Fe₃O₄@‐NH₂@Murexide using a simple and efficient method, and characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies and inductively coupled plasma optical emission spectrometry. The catalytic system showed great efficiency in cross‐coupling reaction of aryl iodides and arylboronic acid and in Sonogashira cross‐coupling reaction in the green solvent EtOH–H₂O (1:1). The isolation and recovery of the catalyst were simple and facile and it could be used for several successive Suzuki–Miyaura coupling and Sonogashira cross‐coupling reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

In Situ Synthesis of a Novel Quinone Imine Self‐Assembled Monolayer and Consideration of Its Reactivity with L‐Arginine

In situ functionalization of a 4‐aminothiophenol (4ATP) self‐assembled monolayer (SAM) on a Au electrode (4ATP/Au SAM) by the Michael addition reaction is considered. Under optimized conditions, the nucleophilic attack of the amino group of 4ATP/Au SAM to give an electrogenerated ortho‐quinone produced a novel electroactive SAM (ESAM). The ESAM could be oxidized to quinone‐imine SAM (QI SAM) for the covalent immobilization of L ‐arginine monolayers. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared (FTIR) spectroscopy are employed to characterize these systems.. The apparent heterogeneous rate constant (k_s^app) for ESAM/Au and the rate constant (k′) of the pseudo‐first order Michael addition reaction of L ‐arginine and ESAM/Au are calculated.     

Four‐component synthesis of disubstituted 1,3,4‐oxadiazole derivatives from cinnamaldehyde,an aromatic carboxylic acid,a secondary amine,and N‐isocyaniminotriphenylphosphorane

The iminium intermediate generated by the reaction between a secondary amine and cinnamaldehyde was reacted with N‐isocyanimino‐triphenylphosphorane in the presence of benzoic acid derivatives to form the corresponding iminophosphorane intermediate, whose intramolecular aza‐Wittig reaction led to disubstituted 1,3,4‐oxadiazole derivatives. The syntheses were completed under neutral conditions at room temperature to give excellent yields. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:315–321, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21013     

Phosphoramidates: Synthesis,spectroscopy, and X‐Ray crystallography

A series of novel phosphoramidates with a general formula P(O)X₁X₂X₃, where X₁ = X₂ = X₃ = 1H‐1,2,4‐triazol ( 1 ); X₁ = X₂ = X₃ = N‐phenylhydrazine ( 2 ); X₁ = Br, X₂ = X₃ = N‐phenylhydrazine ( 3 ), X₁ = Br, X₂ = X₃ = dipropylamine ( 4 ), and X₁ = X₂ = X₃ = 1,4‐dioxa‐8‐azaspiro[4.5]decane ( 5 ) as well as [P(O)(NC₄H₈NH‐CH₃)⁺₃.3Cl^‐] ( 6 ), were synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR spectroscopy, and elemental analysis. It is interesting that the P atoms of compounds 3 and 4 are the most upfielded atoms (δ(³¹P) = −23.00, −21.65 ppm) among molecules 1–6 . This indicates that the Br atom acts as a strong electron donor to the P atom via a resonance interaction. The ¹H and ¹³C NMR spectra of compound 5 reveal three separate sets of peaks for the aliphatic CH² protons of three four‐membered rings. This can be explained by different spatial orientations (conformations) of the aliphatic rings. The crystal structure of compound 6 was also determined by X‐ray crystallography. There are intermolecular N H ···Cl hydrogen bonds in this structure. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:478–485, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21040