Efficient synthesis,reactions, and biological activities of new thieno and furopyrazolo[3,4-b]pyrazines and their related heterocycles

In the present investigation, a simple and straightforward methodology for the preparation of novel bifunctional thienopyrazolopyrazines 4a–d has been reported. Synthesis of thieno or furopyrazolopyrazines 5a , b , e , f was achieved by the reaction of o-amino-esters 4a , b , e , f with 2,5-dimethoxytetrahydrofuran. The latter pyrrolyl derivatives 5a , b , e , f were used as starting intermediates for the synthesis of new pyrimido, pyrido, and pyrazino heterocycles fused to the thieno or furopyrazolopyrazine moiety. Furthermore, alkaline hydrolysis of the o-amino-ester 4a followed by acidification afforded the corresponding o-amino carboxylic acid 15 , which was used as a versatile precursor for the synthesis of other heterocyclic compounds fused to the thienopyrazolopyrazine ring system, namely: pyrimidine, oxazine, oxazepine, and pyridine derivatives 16–23 . The chemical structures of the synthesized compounds were confirmed on the basis of elemental and spectral analyses (Fourier-transform infrared spectroscopy [FT-IR], ¹H nuclear magnetic resonance [NMR], and mass spectroscopy [MS] in addition to ¹³C NMR for some of them). Moreover, from the biological screening, we found that most of the tested compounds exhibited promising antifungal, antibacterial, and anti-inflammatory activities compared with the corresponding reference drugs.     

A convenient green synthetic approach to the synthesis of novel bioactive selenolo[2,3-c]pyrazoles as antibacterial and antifungal agents

A series of new pyrimidine, triazine, and isoindole heterocycles fused to the selenolopyrazole ring system was synthesized by various condensation reactions of the amino selenolopyrazole carboxamide 1 , which was performed by a new green methodology. The pyrimidinone compound 6 was used as a versatile precursor for several aromatic nucleophilic substitution reactions to produce the sulfanyl pyrimidines 10a-c and the corresponding amines 11a-c and 12a , b . Assignment of the chemical structures for the newly synthesized compounds was confirmed by elemental and spectral analyses including Fourier transform infrared (FTIR), ¹H-NMR, and ¹³C-NMR and mass spectroscopy for some of them. Furthermore, some of these compounds were screened against various pathogenic bacterial and fungal strains. Their results demonstrated that some of them revealed remarkable antimicrobial activities.     

Immobilization of transition metal ion complexes and their catalytic activity towards the activation of hydrogen peroxide

Transition metal ion-imidazole complexes have been immobilized on silica, silica–alumina (25%Al₂O₃), and alumina supports by adsorption and functionalization methods. The catalytic activity of these supported complexes in the decomposition of H₂O₂ has been studied. The reaction exhibits first-order kinetics with respect to [H₂O₂] and the quantity of catalyst. The rate of reaction decreases as [H₂O₂]₀ increases. The order of catalytic reactivity is strongly dependent on the type of metal ion, support, and the immobilization method. The complex anchored via adsorption exhibited a higher activity compared to the corresponding complex anchored via functionalization of the surface. The reaction proceed via formation of the peroxo-intermediate, which has an inhibiting effect on the reaction rate. The reaction is enthalpy-controlled as is concluded from the isokinetic relationship. A mechanism is proposed involving the generation of HO₂ radicals from the peroxo-intermediate in the rate-determining step.     

The synthesis of imidazo[4,5-d]pyridines from a substituted imidazole and acyl or sulfonyl acetonitrile

1-Aryl-5-amino-4-cyanoformimidoyl imidazoles were reacted with acyl and sulfonyl acetonitriles, under mild experimental conditions, leading to imidazo[4,5-b]pyridines and imidazo[4,5-b]pyridine-5-ones. A reaction intermediate could be isolated in the reaction with methyl cyanoacetate, under carefully controlled experimental conditions. This intermediate cyclized to imidazo[4,5-b]pyridine-5-one, in the presence of DBU. Reaction between 5-amino-4-cyanoformimidoyl-1-(4-fluorophenyl)imidazole and acetylacetone, occurred by a different pathway to give a 6-carbamoylpurine.     

Über das polarographische Verhalten von Zirkonium- und Thorium-Farbstoffkomplexen

Zusammenfassung Das polarographische Verhalten der Solochrom-Violett RS-Komplexe des Zirkoniums und Thoriums wurde untersucht und Proportionalität zwischen der Höhe der Reduktionswellen der Farbstoffkomplexe und der Konzentration der Metallionen im p_H- Gebiet zwischen 2 und 3 festgestellt. Nach eingehender Überprüfung der p_H-Abhängigkeit von Form und Lage der Reduktionswelle konnte eine Arbeitsvorschrift ausgearbeitet werden, die die gemeinsame Bestimmung des Zirkoniums und Thoriums erlaubt und darüber hinaus durch Maskierung des Thoriums mit Acetationen die Möglichkeit zur selektiven Bestimmung des Zirkoniums neben Thorium bietet. Störungen durch Anionen und andere Kationen wurden untersucht und eingehend diskutiert.

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Summary The polarographic behavior of the Solochrom-Violet RS-complexes of zirconium and thorium was studied, and a proportionality was found between the height of the reduction waves of the dyestuff complex and the concentration of the metal ions in the p_H region between 2 and 3. After intensive checking of the p_H-dependence of the form and position of the reduction waves, a working procedure could be worked out, which permits the simultaneous determination of zirconium and thorium, and which furthermore by masking the thorium with acetate ions, creates the possibility of the selective determination of zirconium in the presence of thorium. Interferences by anions and other cations were investigated and discussed at length.

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Rèsumè Etude du comportement polarographique du complexe du violet solochrome RS et du zirconium et du thorium; il a été établi qu'il existait une relation de proportionalité entre les hauteurs des vagues de réduction du complexe coloré et la concentration des ions métalliques dans un domaine de p_H compris entre 2 et 3. Après un contrôle précis de la variation en fonction du p_H des vagues de réduction, en forme et en position, il a été possible d'établir un mode opératoire permettant le dosage global du zirconium et du thorium ainsi que le dosage sélectif du zirconium en présence du thorium lorsqu'on masque ce dernier par des ions acétates. Les perturbations apportées par les anions et d'autres cations ont été étudiées et discutées en détail.

     

Electrodialysis of uranium(VI) through cation exchange membranes and modeling of electrodialysis processes

The transport of ionic species through ion exchange membranes found several applications for water effluents purification and metal ion separation. To enhance the transport performance, the effect of electric fields was suggested in this work. The transport of U(VI) species in nitric acid solutions across cation exchange membranes was investigated. Different parameters affecting the transport of U(VI) were studied. These parameters include: nitric acid concentration in the feed solution, stripping solution concentration and applied electric field. From the results obtained, the cationic flux of U(VI) was 6.5^.10^–8 geq^.cm^–2.s^–1 at the optimal conditions of 10^–3M HNO₃ in the feed solution, 0.5M Na₂CO₃ in the stripping solution and 30 V. The modeling of the electrodialysis process was also made. The model correlates the mass transfer as a function of current density and voltage as variables and takes into account the electro-osmotic effect. The model is applied to the experimental data.     

Ion-selective electrodes in organic functional group analysis: Microdetermination of hydrazines with the copper electrode

Summary A simple micromethod is described for the determination of hydrazines using the copper ion-selective electrode. The method is based on direct potentiometric titration of the sample in ammoniacal solution of pH 9.5±0.2 with copper(II) ions at room temperature. N-Shaped curves with well-defined inflections at 11 and 12 molar ratios are obtained. This is probably due to the formation of copper monohydrazinate and copper dihydrazinate complexes. Various alkyl and aryl hydrazines and hydrazine salts have been satisfactorily analyzed with an average recovery of 99.4% and a relative standard deviation of ±0.4%. The reaction of hydrazines with Fehling's solution followed by measuring the copper(I) oxide formed using the copper ion-selective electrode also has been investigated.

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Zusammenfassung Eine einfache Mikromethode zur Bestimmung von Hydrazinen mit einer kupferionen-selektiven Elektrode wurde beschrieben. Sie beruht auf der direkten potentiometrischen Titration in ammoniakalischer Lösung mit Cu(II)ionen bei pH 9,5±0,2 bei Zimmertemperatur. N-förmige Kurven mit gut ausgebildeten Spitzen bei Molverhältnissen 11 und 12 wurden erhalten, wahrscheinlich auf Grund der Bildung von Mono- bzw. Dihydrazinatkomplexen des Kupfers. Verschiedene Alkyl- und Arylhydrazine und deren Salze wurden zu 99,4% mit einer Standardabweichung von ±0,4% wiedergefunden. Die Reaktion der Hydrazine mit Fehlingscher Lösung wurde ebenfalls durch Messung des entstandenen Cu(I) mit der erwähnten Elektrode untersucht.

     

Physicochemical Studies of Some Mercury Pyrimidine Complexes

Mercury(II) complexes of some pyrimidine derivatives were prepared and characterized by elemental analysis and spectral measurements. The ¹H n.m.r and i.r. spectra show the ligands to be in the keto form. Thermal analysis and electrical conductivity measurements of the complexes were investigated in the temperature range 30–250°C. The results indicate slight semiconducting behaviour. The disparity in the activation energy values, ΔE as calculated from the slopes of the linear parts of the electrical conductivity curves is due to the difference in the concentration of the imperfections contained in the different types of the complexes.     

Molecular dynamics and alignment studies of silica-filled 4-pentyl-4′-cyanobiphenyl (5CB) liquid crystal

A comprehensive study of the dielectric properties of 4-pentyl-4′-cyanobiphenyl (5CB) liquid crystal filled with silica particles (particle size 30–80 nm, concentration 2, 3, 5, 10 and 15 wt%). Dielectric spectroscopy in the frequency range 100 to 10 7 Hz was applied to investigate the influence of the filler on the dynamic behaviour of the liquid crystal molecules in both the nematic and isotropic phases. In this frequency range one relaxation process is observed (at f>10⁶ Hz). The dynamical behaviour of the 5CB liquid crystal is described by the Cole-Cole relaxation function. The temperature dependence of the relaxation time obeys the empirical Arrhenius equation. The activation energies are approximately 75 kJ mol¹ for the pure 5CB sample in the nematic phase and 50 kJ mol¹ for the 5 wt% silica-filled 5CB sample. These values are compared with the corresponding literature values. The reversible electro-mechanical response of these samples under the influence of an applied a.c. electric field is investigated.     

First-order optimization algorithms via inertial systems with Hessian driven damping

For controlled discrete-time stochastic processes we introduce a new class of dynamic risk measures, which we call process-based. Their main feature is that they measure risk of processes that are functions of the history of a base process. We introduce a new concept of conditional stochastic time consistency and we derive the structure of process-based risk measures enjoying this property. We show that they can be equivalently represented by a collection of static law-invariant risk measures on the space of functions of the state of the base process. We apply this result to controlled Markov processes and we derive dynamic programming equations. We also derive dynamic programming equations for multistage stochastic programming with decision-dependent distributions.