Synthesis of 1H-pyrazolo[3,4-e]-s-triazolo[3,4-c]-as-triazines, 8H-pyrazolo[3,4-e]tetrazolo[5,1-c]-as-triazine and 1,7-dihydro-8H-pyrazolo[3,4-e]-as-triazine derivatives

3-Hydrazino-7-methyl-5-phenyl-5H-pyrazolo[3,4-c]-as-triazine 1 underwent ring closure and/or condensation reaction with formic acid, acetic acid, acetic anhydride and benzoyl chloride to afford 1H-pyrazolo-[3,4-d]-s-triazolo[3,4-c]-as-triazines 2, 5 and 7a and/or N-acyl derivatives 3, 4 and 6 . N-Acyl derivatives 3 and 6 underwent cyclisation reaction on treatment with phosphoryl chloride to give 5 and 7a . 3-Methyl-1-phenyl-8-aryl-1H-pyrazolo[3,4-e]-s-triazolo[34,-c]-as-triazines 7 were also prepared by the reaction of the hydrazono derivatives 8 wit thionyl chloride. On treatment of 1 with nitrous acid gave the 8H-pyrazolo[3,4-e]tetrazolo-[5,1-c]-as-triazine 9 . Compound 1 underwent ring closure with carbon disulphide or ethyl chloroformate to 1,7-dihydro-8H-pyrazolo[3,4-e]-s-triazolo[3,4-c]-as-triazine derivatives 10 and 12 . Reaction of 1 with ethyl acetoacetate or acetylacetone gave 3-pyrazolo derivatives 13 and 14 .     

Electrical and optical properties of chalcopyrite compounds

Optical and electrical properties of Zn- and Cd-modified Cu₂SnSe₄ amorphous films have been studied. The results show that Zn and Cd incorporation decreases the thermal activation energy, the pre-exponential factor and the optical gap. Variation in the refractive index and extinction coefficient with the wavelength has been also reported. The relations between the optical gap and the chemical composition in the investigated films have been discussed in terms of the average heat of atomization. The effect of γ-radiation up to 71.25 Mrad dose on the optical gap was also studied.     

Anticancer and anti-inflammatory sulfur-containing semisynthetic derivatives of sarcophine

Sarcophine (1), a cembranoid diterpene is known to inhibit the process of tumorigenesis. Sarcophine can be isolated in large amounts from the Red Sea soft coral Sarcophyton glaucum and hence is an ideal target for semisynthetic or biocatalytic modifications. Hydroxylated derivatives of 1 were reported to improve its anticancer activity. Despite the promising results and ready availability, there are limited attempts towards further diversifying the library of sarcophine derivatives. Hence, the current study targets the epoxide ring to generate sulfur-containing derivatives of sarcophine by reacting it with ammonium thiocyanate and Lawesson's reagent. Structure elucidation of the products was based on extensive 1D and 2D NMR and high resolution mass spectrometry, in addition to mechanistic considerations. The effect of these derivatives on highly malignant +SA mammary epithialial cell proliferation is reported. Anti-inflammatory potential of sarcophine and its derivatives is also demonstrated.     

Sea water desalination by dynamic layer melt crystallization: Parametric study of the freezing and sweating steps

This work aims at developing a dynamic layer crystallizer operated batchwise, for freezing desalination of sea water. The experiments were performed with water/NaCl solutions and with samples of sea water from Nice, Rabat and Marseille. The pilot crystallizer consists of a cooled tube immersed in a cylindrical double jacketed tank. The solution is poured into the tank and the crystallization takes place on the external surface of the tube, by applying a cooling ramp in the tube. The solution is agitated by air bubbling. The whole process involves the freezing step, leading to the crystallization of the ice layer and the sweating step, which consists of purifying in depth the ice layer by melting the impure zones. A parametric study on the effect of the operating parameters has allowed quantifying the role of the different key parameters of the freezing and sweating steps. Three experiments allowed reaching salinities lower than 0.5 g/kg, satisfying the standards of drinking water. The duration of the whole process dropped to only 8 h (5 h for freezing and 3 h for sweating), with a yield of sweating equal to about 50%, provided severe conditions were applied for sweating. Higher yields required longer times. Overall, the results show the feasibility of the technique.     

Bromination and diazo-coupling of pyridinethiones; microwave assisted synthesis of isothiazolopyridine, pyridothiazine and pyridothiazepines

Isothiazolopyridines, pyridothiazines and pyridothiazepines are important compounds that possess valuable biological activities. This paper reports on the synthesis of these compounds using both conventional chemical methods and modern microwave techniques. 3-Bromo-6-hydroxy-4-methyl-2-thioxo-2,3-dihydropyridine-3-carboxamide, 5-arylazo-6-hydroxy-4-methyl-2-thioxo-1,2-dihydropyridine-3-carboxamides, 3,5-bis-arylazo-6-hydroxy-4-methyl-2-thioxo-2,3-dihydropyridine-3-caboxamide, 4-methyl-2,3,6,7-tetra-hydroisothiazolo[5,4-b]-pyridine-3,6-dione, 2,2'-(methylene-bis-(sulfanediyl))bis(4-methyl-6-oxo-1,6-dihydropyridine-3-carboxamide), 2-hydroxy-5-methyl-4H-pyrido[3,2-e][1,3]-thiazine-4,7(8H)-dione and 2-arylmethylene-8-hydroxy-6-methyl-2,3,4,5-tetrahydropyrido-[3,2-f][1,4]thiazepine-3,5-diones have been prepared from 6-hydroxy-4-methyl-2-thioxo-2,3-dihydropyridine-3-carboxamide. Some of these compounds were prepared using microwave-assisted reaction conditions, that provided higher yields in shorter times than the conventional methods.     

A Fast and Effective Algorithm for the Feedback Arc Set Problem

A divide-and-conquer approach for the feedback arc set is presented. The divide step is performed by solving a minimum bisection problem. Two strategies are used to solve minimum bisection problem: A heuristic based on the stochastic evolution methodology, and a heuristic based on dynamic clustering. Empirical results are presented to compare our method with other approaches. An algorithm to construct test cases for the feedback arc set problem with known optimal number of feedback arcs, is also presented.     

Spectre d'anneaux de polynômes sur une suite de modules

Sans résumé     

A new synthetic route to 1,3,4-oxadiazoles. Pharmacological study of some new derivatives

2-Substituted 1,3,4-oxadiazoles have been examined as possible prodrugs of antidepressant hydrazides. A new method of synthesis of this heterocycle from thionoester and five new oxadiazoles substituted at the 2-position by a 4-pyridyl or 4-aminophenyl group and at the 5-position by a phenyl group are described.