Recherches en série diazépine-1,4 et triazépine-1,2,4. XI—etude en spectrométrie de masse des fragmentations de triazépines-1,2,4

The mass spectra of eleven 1,2,4-triazepines with oxo, thioxo, methoxy and methylmercapto groups in the 3 and 5 positions are reported and analysed. Each of the five structures of the triazepine ring present is characterized by a particular group of fragmentations.     

Synthèses de 1,2,4-triazolo[4,3-d][1,4]diazépines et de 1,2,4-oxadiazolo[4,5-d][1,4]diazépines par cycloaddition dipolaire-1,3

We report here a one-step synthesis of the 4,5,6,7-tetrahydro-1H- 1,2,4,-triazolo[4,3-d][1,4]diazepine, 4-6, and 1,2,4-oxadiazolo[4,5-d][1,4]-diazepine, 7-10, by 1,3-dipolar cycloaddition of nitrile imines and nitrile oxides with 2,3-dihydro-H-1,4-diazepine, 1. In all cases these cycloaddition are peri- and regioselectives (the C ? N bond is sole affected) and occures with high yields. Structure and conformations of cycloadducts have been assigned by means of nmr analysis     

Facile Synthesis and in Vitro Cytotoxic Evaluation of Novel Thiadiazole,Pyrazole, and Dithiole-Androstane Derivatives

In the aim of identifying new steroidal cytotoxic agents with potential antiproliferative activity against hepatoma cell lines (Hep-G₂), we synthesized modified steroids containing the thiadiazole, pyrazole, or dithiole moiety. Epiandrosterone 1 reacted with carbon disulfide and sodium hydride to furnish α-oxoketene dithio-disodium salt 2. Treatment of 2 with the hydrazonoyl halides 5a–d produced the thiadiazole anellated androstanone 7a–d, respectively. The reaction of 1 with hydrazine hydrate produced the hydrazide adduct 8, which cyclized upon reflux in acetic acid to form the condensed pyrazoloandrostanone derivative 9. Interaction of 8 with carbon disulfide and sodium hydride formed the disodium salt 10, which reacted with ethylchloroacetate to furnish the final adduct, dithioloandrostane derivative, 13. Compounds 7a, 7d, 9, and 13 were examined for their cytotoxicity against a panel of hepatoma cell lines (Hep-G₂) using MTT assay. The results provide that, at incubation time 72 h, in DMSO, compound 7d (50 μ mol/mL) showed the most significant cytotoxic effect at P < 0.05. The higher dose (100 μ mol/mL) of compound 7d, at 48 h incubation, reversed the effect causing resistance and the growth rate return to the control level.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Zirconium complexes to overcome oxygen inhibition in free‐radical photopolymerization of acrylates: Kinetic,mechanism, and depth profiling

The photopolymerization process of acrylate coatings initiated by visible light (λ > 380 nm) and performed in air was studied in the presence of zirconium complexes. Depth profiling experiments were performed using confocal Raman microscopy showing that the conversion, which is low at the surface of the sample, increases with increasing depth and reaches a full conversion close to the substrate. RT‐FTIR spectroscopy corroborates Raman results in evidencing the efficiency of some zirconium compounds to reduce oxygen inhibition. Finally, laser flash photolysis experiments revealed that the beneficial effect in air is attributable to the reaction of the zirconium complex on the peroxyl radicals formed from the reaction of oxygen with radicals. Therefore, the oxygen present in the medium is depleted, allowing a better efficiency of the photopolymerization process. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Molecular dynamics simulations of the nano-scale room-temperature oxidation of aluminum single crystals

The oxidation of aluminum single crystals is studied using molecular dynamics (MD) simulations with dynamic charge transfer between atoms. The simulations are performed on three aluminum low-index surfaces ((1 0 0), (1 1 0) and (1 1 1)) at room temperature. The results show that the oxide film growth kinetics is independent of the crystallographic orientation under the present conditions. Beyond a transition regime (100 ps) the growth kinetics follow a direct logarithmic law and present a limiting thickness of ∼3 nm. The obtained amorphous structure of the oxide film has initially Al excess (compared to the composition of Al₂O₃) and evolves, during the oxidation process, to an Al percentage of 45%. We observe also the presence of an important mobile porosity in the oxide. Analysis of atomistic processes allowed us to conclude that the growth proceeds by oxygen atom migration and, to a lesser extent, by aluminum atoms migration. In both cases a layer-by-layer growth mode is observed. The results are in good agreement with both experiments and earlier MD simulations.     

Analytical and numerical study of natural convection heat transfer in an inclined composite enclosure

Laminar natural convection heat transfer in inclined fluid layers divided by a partition with finite thickness and conductivity is studied analytically and numerically. The governing equations for the fluid layers are solved analytically in the limit of a thin layered system with constant flux boundary conditions. The study covers of the range of Ra from 10³ to 10⁷, from 0° to 180° and the thermal conductivity ratio of partition to fluid ratioK from 10^–2 to 10⁶. The Prandtl number was 0.72 (for air). Results are obtained in terms of an overall Nusselt number as a function of Rayleigh number, angle of inclination of the system, mid layer thickness, and mid layer thermal conductivity. The critical Rayleigh number for the onset of convection in a bottom-heated horizontal system is predicted. The results are compared with the numerical results obtained by solving the complete system of governing equations, using SIMPLER method, as well as with the limiting cases in the literature.     

Multiple Steady State Solutions Resulting From Coupling Between Mixed Convection And Radiation In An Inclined Channel

In this work, we present a numerical study of mixed convection coupled with radiation in an inclined channel with an aspect ratio B = L/H=10, and locally heated from one side. Convective, radiative and total Nusselt numbers, evaluated on the cold surface and at the exit of the channel, are presented for different combinations of the governing parameters namely, the surface emissivity (0 1), the Reynolds number (10 Re 50), the inclination of the channel with respect to the horizontal surface (0° 90°) and the Rayleigh number (Ra = 10⁵). The ratio, R = Q_C/Q_E, of the heat quantities, leaving the channel through the cold wall, Q_C, and through the exit, Q_E, is presented to identify the most favorable issue to the heat transfer in the studied configuration. The results obtained show that the flow structure is significantly altered by radiation which contributes to reduce or to enhance the number of the solutions obtained.     

Distribution of free amino acids,polyphenols and sugars of Ziziphus jujuba pulps harvested from plants grown in Tunisia

Ziziphus jujuba pulps are very much appreciated by the inhabitants and have been recently exported. This article reports on the chemical composition (amino acids, polyphenols and sugars) of the pulps of four Z. jujuba ecotypes (Choutrana, Mahdia, Mahres and Sfax). The major amino acids identified were proline, aspartic acid and glutamic acid. Among these, proline was the most abundant amino acid (17.4 mol). Considerable differences in total phenolic contents (15.85 mg/L) were found. Predominant phenols identified by using HPLC were rutin (1.09 mg/L) and chlorogenic acid (2.57 mg/100 g). Sugars isolated from Ziziphus pulps were found at a rate of 43.52%. Using HPLC method, three sugars from the pulp extract were identified: glucose, galactose and sucrose. The Mahdia ecotype was the richest in these sugars with 0.45, 136.51 and 113.28 mg/L, respectively.