Safia Djebbar

Palladium-Catalyzed Direct Arylation of Free NH2-Substituted Thiophene Derivatives

The palladium-catalyzed direct 2- or 5-arylation of some free NH(2)-substituted thiophene derivatives was found to proceed in high yields using a variety of aryl bromides. In the course of these reactions, no coupling of the aryl bromide with the thiophene NH(2) substituent was detected. The presence of an ester substituent on C2 of thiophene was found to be useful to block this highly reactive carbon.

Environmentally-Safe Conditions for a Palladium-Catalyzed Direct C3-Arylation with High Turn Over Frequency of Imidazo[1,2-b]pyridazines Using Aryl Bromides and Chlorides.

Pd(OAc)2 was found to catalyze very efficiently the direct arylation of imidazo[1,2-b]pyridazine at C3-position under a very low catalyst loading and phosphine-free conditions. The reaction can be performed in very high TOFs and TONs employing as little as 0.1-0.05 mol % catalyst using a wide range of aryl bromides. In addition, some electron-deficient aryl chlorides were also found to be suitable substrates. Moreover, 31 examples of the cross couplings were reported using green, safe, and renewable solvents, such as pentan-1-ol, diethylcarbonate or cyclopentyl methyl ether, without loss of efficiency.

Characterization and Complexing Capacity of Humic Acid Extracted from Yakouren Soil with Heavy Metals by Conductimetry and Quenching of Fluorescence

New humic acid isolated from forest soil of Yakouren (YHA), Algeria, and purified commercial humic acid (PCHA) were analyzed and characterized. Elemental analyses, electronic microscopy, UV-Vis absorbance E465/E665 ratio and molecular spectroscopy investigation using CP-MAS 13C-NMR of YHA indicated the presence of a high content of aliphatic and carboxylic acid groups. The higher O/C, H/C and N/C ratios of YHA can be assigned to the low aromatization degree. A study of interaction between Ni(II), Zn(II), Cd(II) and humic acids (HAs) at different metal-ligand ratios has been made by conductimetric and fluorescence techniques. The results obtained by the conductimetry method are interpreted using an excess function (Δk), which related the conductivity of the mixture and of the separated components. A positive value of this function is obtained. It indicates the complexation of HAs with metallic ions. The association degree of the heavy metals (M) with both HAs was in the following order: Ni > Zn > Cd and the binding capacity of PCHA is smaller than that of YHA. A fluorescence titration method and a single site model were used for determining metal ion complexing capacities (CCM) and stability constants (log KM) of YHA and PCHA complexes. Titration of HAs with metal ions at pH 7 and ionic strength 0.1 mol/L resulted in a marked decrease of fluorescence intensities of untreated HAs. The quenching constants (KSV) between HAs and M are obtained in terms of Stern–Volmer analysis. KSV show that the YHA binds the higher amount metals than PCHA. CCM of YHA calculated by MATLAB program were higher than those of PCHA and other natural HAs found in the literature at pH 7. Based on these results, YHA may play the role of a biocaptor of polluting metals.

Iron and nickel complexes with heterocyclic ligands: stability, synthesis, spectral characterization, antimicrobial activity, acute and subacute toxicity.

The synthesis and characterization by elemental analysis, emission atomic spectroscopy, TG measurements, magnetic measurements, FTIR, (1)H NMR, UV-visible spectra and conductivity of a series of iron (II) and nickel (II) complexes with two heterocyclic ligands (L(1)(SMX): sulfamethoxazole and L(2)(MIZ): metronidazole) used in pharmaceutical field and with a new ligand derived benzoxazole (L(3)(MPBO): 2-(5-methylpyridine-2-yl)benzoxazole), were reported. The formulae obtained for the complexes are: [M(L(1))2 Cl2]·nH2O, [M(L(2))2Cl2(H2O)2]·H2O and [M(L(3))2(OH)2]·nH2O. Stability constants of these complexes have been determined by potentiometric methods in water-ethanol (90:10, v/v) mixture at a 0.2 mol L(-1) ionic strength (NaCl) and at 25.0±0.1 °C. Sirko program was used to determine the protonation constants as well as the binding constants of three species [ML2H2](2+), [ML2] and [ML](2+). The antimicrobial activity of the ligands and complexes was evaluated in vitro against different human bacteria and fungi using agar diffusion method. Iron sulfamethoxazole complex showed a remarkable inhibition of bacteria growth especially on Staphylococcus aureus and P. aeruginosa. The iron metronidazole complex is active against yeasts especially on Candida tropicalis strain. Nickel complexes presented different antibacterial and antifungal behaviors against bacteria and fungal. The acute toxicity study revealed that the iron complexes are not toxic at 2000 mg/kg dose orally administrated. LD50 for nickel complexes was determined using graphical method. No significant differences in the body weights between the control and the treated groups of both rat sexes in subacute toxicity study using for iron complexes. Hematological and clinical blood chemistry analysis revealed no toxicity effects of the iron complexes. Pathologically, neither gross abnormalities nor histopathological changes were observed for these complexes.

Efficient synthesis of π-conjugated molecules incorporating fluorinated phenylene units through palladium-catalyzed iterative C(sp2)–H bond arylations

Summary We report herein a two or three step synthesis of fluorinated π-conjugated oligomers through iterative C–H bond arylations. Palladium-catalyzed desulfitative arylation of heteroarenes allowed in a first step the synthesis of fluoroaryl-heteroarene units in high yields. Then, the next steps involve direct arylation with aryl bromides catalyzed by PdCl(C3H5)(dppb) to afford triad or tetrad heteroaromatic compounds via regioselective activation of C(sp2)–H bonds.