Kinetic and mechanistic investigations on the oxidation of N’-heteroaryl unsymmetrical formamidines by permanganate in aqueous alkaline medium

Kinetic studies on the oxidation of two substituted azinyl formamidines (Azn-Fs), namely N,N-dimethyl-N’-(pyrimidin-2-yl) formamidine (Pym-F) and N,N-dimethyl-N’-(pyridin-2-yl) formamidine (Py-F), by alkaline permanganate have been performed by spectrophotometry. The spectroscopic and kinetic evidence reveals the formation of 1:1 intermediate complexes between the oxidant and substrates. The influence of pH on the oxidation rates indicated that the reactions are base-catalyzed. The reactions show identical kinetics, being first order each in [MnO₄ ^?]₀ and [Azn-F]₀, but with a fractional first-order dependence on [OH^?]. The effect of temperature on the reaction rate has been studied. Increasing ionic strength has no significant effect on the rate. The final oxidation products of Pym-F and Py-F were identified as 2-aminopyrimidine and 2-aminopyridine, respectively, in addition to dimethyl amine and carbon dioxide. Under comparable experimental conditions, the oxidation rate of Py-F is higher than that of Pym-F. A reaction mechanism adequately describing the observed kinetic behavior is proposed, and the reaction constants involved in the different steps of the mechanism have been evaluated. The activation parameters with respect to the rate-limiting step of the reactions, along with thermodynamic quantities, are presented and discussed.     

Synthesis and cytotoxic activity of some novel benzocoumarin derivatives under solvent free conditions

In the present study, a rapid, less expensive, clean and environmental friendly route to synthesis new pyrazoles, pyrazolopyridazines and condensed pyrimidines was developed via grinding of 2-(3-(dimethylamino)acryloyl)-3H-benzo[f]chromen-3-one (1) with different reagents. All the new compounds were characterized and established using elemental analysis and spectral data. Eight compounds were selected for in vitro antiproliferative against different human cancer cell lines entitled melanoma, cancers of the lung, leukemia, breast, brain, colon, prostate, ovary and kidney by the USA NCI.     

An Efficient Approach for the Synthesis of 1,2,3‐Triazole Moiety to Generate Uracil Molecular Architectures Through Cu‐Catalyzed Azide–Alkyne Cycloaddition

A simple and efficient pathway to tether conjugates of monosaccharides or aromatic moieties to uracil establishing a 1,2,3‐triazole linker via click chemistry was reported. The reaction of arylimines of 5‐amino uracil with propargyl bromide in a basic medium gave a di‐propargylated uracil. The latter compound was converted into molecular architectures containing bis‐1,2,3‐triazole rings through Cu‐catalyzed 1,3‐cycloaddition reaction with different azides. The same arylimine of 5‐amino uracil yielded different products under reflux with propargyl bromide in acetonitril with the majority to 6‐propargylated‐5‐amino uracil.     

Reassignment of the structures of products produced by reactions of the product believed to be 2-(1-phenyl-2-thiocyanatoethylidene)-malononitrile with electrophiles

The reactivity of the product believed to be 2-(1-phenyl-2-thiocyanato-ethylidene)malononitrile toward a variety of electrophilic and nucleophilic reagents is reported.     

Quasi-classical trajectory study of the S + OH → SO + H reaction: from reaction probability to thermal rate constant

First quasi-classical trajectory calculations have been carried out for the S((3)P) + OH(X?(2)Π) → SO(X?(3)Σ(-)) + H((2)S) reaction on an ab initio global potential energy surface for the ground electronic state, X?(2)A', of HSO. Cross sections, computed for collision energies up to 1 eV, show no energy threshold and decrease with the increasing collision energy. Rate constants have been calculated in the 5-500 K temperature range. The thermal rate constant is in good agreement with approximate quantum results, while a disagreement is found at 298 K with the experimental data. Product energy distributions have also been reported at four collision energies from 0.001 to 0.5 eV. The shapes of the rovibrational and angular distributions suggest the formation of an intermediate complex that is more and more long-lived as the collision energy increases.     

Mesoionic 1,2,4-triazolo[4,3-c]quinazolines

Because of the close structural similarity between triazoloquinazolines and certain 5-membered ring mesoionic heterocycles, all of which possess antiinflammatory activity, we prepared several examples of the novel mesoionic 1,2,4-triazolo[4,3-c]quinazoline ring system for their therapeutic potential. These compounds can be prepared by the cyclization of the appropriately substituted 4-hydrazinoquinazolines with phosgene. When the mesoionic product was unsubstituted at the 5-position (i.e., quinazoline 2-position), it could only be isolated as its hydrochloride salt and not as its unstable free base. None of the mesoionic products were sufficiently stable in solution to allow for evaluation of their antiinflammatory activity.     

Pyridazine Derivatives and Related Compounds. Part 11: 1Synthesis of Some Pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazines

3-Substituted pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine-2,4-di-ones and 3-amino-2-methylpyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine-4-ones were synthesized starting from ethyl 5-aminothieno[2,3-c] pyridazine-6-carboxylate 1. Reaction of amino ester 1with phenyl isothiocyanate affords thiourea derivative 10which undergo further transformation to the related fused heterocyclic systems.     

Synthesis, spectral and thermal studies of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complex dyes based on hydroxyquinoline moiety

A series of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of azo-compounds containing hydroxyl quinoline moiety have been synthesized and characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic and ESR spectral studies. The results revealed the formation of 1:1 and 1:2 (L:M) complexes. The molar conductance data reveal that the chelates are nonelectrolyte. IR spectra indicate that the azodyes behave as monobasic bidentate or dibasic tetradentate ligands through phenolate or carboxy oxygen, azo N for 1:1 (L:M) complexes beside phenolate oxygen and quinoline N atoms for 1:2 (L:M) complexes. The thermal analyses (TG and DTA) as well as the solid electrical conductivity measurements are also studied. The molecular parameters of the ligands and their metal complexes have been calculated.     

Gamma radiation curing of nitrile rubber/high density polyethylene blends

Nitrile butadiene rubber (NBR) was mixed with high density polyethylene (HDPE) thermoplastics with different ratio namely (100/20), (100/40), (100/60) and (100/80). The obtained blends were subjected to gamma irradiation with varying dose from 50 to 250 kGy. The induced crosslinking and hence the improvement in the different properties were followed up as a function of irradiation dose. Mechanical properties as tensile strength, tensile modulus at 50 % elongation, elongation at break percent, permanent set and hardness were carried out as a function of irradiation dose and blend ratio. Moreover, physical properties namely, gel fraction % and swelling number were found to improve with the increase of irradiation dose up to 250 kGy and with the increase of the content of HDPE in blend. Moreover, presence of NBR enhances the shrinking properties of the obtained blend which can be used as a good heat shrinkable material.     

A novel carbon/chitosan paste electrode for electrochemical detection of normetanephrine in the urine

Normetanephrine is a marker for pheochromocytoma, a rare catecholamine-secreting and neuroendocrine tumor, that arises from sympathetic and parasympathetic paraganglia. In this work, a novel carbon/chitosan electrode paste was used for sensitive voltammetric determination of normetanephrine and dopamine in the presence of ascorbic acid and uric acid. The modified electrode has shown an increase in the effective area of up to 68%, well-separated oxidation peaks, and an excellent electrocatalytic activity. The electrochemical response characteristics were investigated by cyclic and differential pulse voltammetry. Interestingly, high sensitivity and selectivity in the linear range of normetanephrine, dopamine, ascorbic acid, and uric acid concentrations were observed. The present method was applied in the urine sample and satisfactory results were obtained showing that this electrode is very suitable in pharmaceutical and clinical preparations.