Synthesis of Symmetrical and Unsymmetrical 1,3-Diheteroarylbenzenes Through Palladium-Catalyzed Direct Arylation of Benzene-1,3-disulfonyl Dichloride and 3-Bromobenzenesulfonyl Chlorides

International audienceThe palladium-catalyzed synthesis of unsymmetrical 1,3-diheteroarylbenzenes was investigated. The first synthetic pathway relies on the desymmetrization of benzene-1,3-disulfonyl dichloride through two successive palladium-catalyzed direct desulfitative arylations with two different heteroarenes. The second strategy employs the orthogonal functionalization of 3-bromobenzenesulfonylchloride using an iterative C–H bond arylation sequence, namely, palladium-catalyzed direct desulfitative arylation followed by a palladium-catalyzed direct arylation step using aryl bromide as the coupling partner. The synthesis of symmetrical 1,3-diheteroarylbenzenes was also investigate

Pd-catalysed heteroarylations of 3-bromochromen-4-one via C-H bond activation of heteroarenes.

International audienceThe palladium-catalysed direct coupling of 3-bromochromen-4-one with heteroaromatics was found to proceed in moderate to high yields. A wide variety of heteroaromatics can be coupled with this chomenone derivative using 2 mol % PdCl(C3H5)(dppb) catalyst and KOAc as the base. Moreover, the reaction tolerates a range of useful functional groups on the heteroarene

A new ternary ruthenium(III) complex with 1,3-bis(salicylideneamino) propan-2-ol and 3-picolylamine: Synthesis, characterization, density functional theory and preparation of electrochemical sensor for nitrite analysis.

International audienceA novel electrochem. sensor based on graphite (G) functionalised with a new ternary ruthenium(III) complex was developed and applied to detect nitrite in aq. soln. The Ru(III) complex was synthesized using 1,3-bis(salicylideneamino) propan-2-ol polydentate Schiff base (BSAP) and 3-Picolylamine (PLA), and was characterized by elemental anal., Fourier transform IR spectroscopy (FT-IR), UV-visible spectrophotometry (UV-Visible), gradient-assisted hetero nuclear single quantum coherence spectroscopy (gHSQC) and cyclic voltammetry technique. In addn., the structure of the synthesized complex was optimized using d. functional theory (DFT). The results showed that the ternary Ru(III)-BSAP-PLA complex was formed and the adapted structure was an tetrahedral geometry.The electrochem. behavior of nitrite at the sensor prepd. using G/Ru(III)-BSAP-PLA composite shows that the evaluated electron transfer coeff. (α = 0.83) indicates a very significant electrocatalytic mechanism for oxidn. of nitrite in the presence of the Ru(III)-BSAP-PLA complex.Comparing to other published works, the sensor developed using G/Ru(III)-BSAP-PLA exhibited low limit of detection (LOD = 1.81 μM) around pH = 7. [on SciFinder(R)

Palladium-catalyzed direct arylation of free NH2 substituted thiophene derivatives

International audienceThe palladium-catalyzed direct 2- or 5-arylation of some free NH2-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 NH2 substituent was detected. The presence of an ester substituent on C2 of thiophene was found to be useful to block this highly reactive carbon

Catalytic system for inhibition of amination type reaction and palladium-catalyzed direct arylation using non-protected pyrazole derivatives

International audienceThe palladium-catalysed direct arylation at C-4 of non-protected 5-aminopyrazoles was found to proceed in high yields using a variety of aryl bromides. The choice of potassium acetate as the base was found to be crucial to inhibit the amination reaction and to promote the direct arylation

Reactivity of N-protected 5-(2-bromophenyl)tetrazoles in palladium-catalyzed direct arylation of heteroarenes or fluorobenzenes

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Reactivity of benzofuran and benzothiophene in palladium-catalysed direct C2,C3-diarylations

International audienceThe Pd-catalysed one pot direct diarylation of benzofuran and benzothiophene at both C2- and C3-positions was studied. In the presence of electron-deficient aryl bromides, the diarylation of benzofuran proceeded in good yields; whereas, with benzothiophene moderate yields were generally obtained, as the C3-position exhibits a poor reactivity. In order to obtain 2,3-diarylated benzothiophenes, its sequential arylation was examined. We found that the C3-arylation of benzothiophene followed by its C2-arylation provides a reliable methodology for the access to 2,3-diarylbenzothiophenes

Electrochemical sensors using modified electrodes based on copper complexes formed with Algerian humic acid modified with ethylenediamine or triethylenetetramine for determination of nitrite in water.

International audienceThe response and efficiency of new sensors for nitrite ions analysis have been studied electrochemically. These sensors were developed by modifying a carbon paste electrode (CPE) with copper (II) complexes formed with commercial (PFHA) and Algerian (YHA) humic acids and their modified compounds with ethylenediamine (EDA) or triethylenetetramine (TETA). The developed mechanism is based on the electrochemical oxidation of NO2(-) on the modified CPE for different nitrite concentrations. The obtained results showed that the carbon paste electrode modified with copper (II)-modified humic acids complexes (Cu-MHA) exhibited substantial electrocatalytic effect on the oxidation of nitrite anions compared with carbon paste electrode. The sensitivity of the modified CPE towards nitrite concentrations depends on the nature of the humic acid and its modified compounds. The measurements performed by using CPE/Cu-YHA-EDA and CPE/Cu-YHA-TETA gave the best sensitivity and a good linear response of current versus nitrite concentrations. The oxidation peak current of nitrite at CPE/Cu-YHA-TETA and CPE/Cu-YHA-EDA electrodes in weak acid solution is proportional to the concentration of nitrite over the range 0-1.38×10(-2)molL(-1) with a limit of detection (LOD) of 1.46μmolL(-1) (Sensitivity=41.06μA(mmolL(-1))(-1) and 2.17μmolL(-1) (Sensitivity=27.63μA(mmolL(-1))(-1), respectively. Compared to the sensors published in the literature, our CPE/Cu-YHA-TETA and CPE/Cu-YHA-EDA electrodes exhibit a good catalytic activity towards nitrite oxidation and a low limit of detection over a wide nitrite concentrations range

Evaluation of adsorption capacities of humic acids extracted from Algerian soil on polyaniline for application to remove pollutants such as Cd(II), Zn(II) and Ni(II) and characterization with cavity microelectrode.

International audienceThe adsorption capacities of new humic acids isolated from Yakouren forest (YHA) and Sahara (Tamenrasset: THA) soils (Algeria) and commercial humic acid (PFHA) on polyaniline emeraldine base (PEB) were studied at pH 6.6. Also the adsorption of heavy metals such as Cd2+, Zn2+ and Ni2+ on humic acid-polyaniline systems (HA-PEB) was investigated at the same conditions. HA-PEB compounds were characterized by scanning electron microscopy (SEM), infrared spectrometry and cavity microelectrode. In addition, batch adsorption and cavity microelectrode were used in the adsorption study of Cd2+, Zn2+ and Ni2+ on HA-PEB. To develop biocaptors of polluting metals using a cavity microelectrode modified by HA-PEB systems, the adsorption kinetic and adsorption capacity were investigated. The SEM analysis showed that the presence of humic acid affected the PEB surface and caused the formation of a granular morphology. The maximum adsorption capacities (q(max)) of PFHA, THA and YHA determined by adsorption isotherms were 91.31, 132.1 and 151.0 mg/g, respectively. Batch adsorption results showed that q(max) of Cd2+, Zn2+ and Ni2+ on HA-PEB followed the order: THA-PEB > YHA-PEB > PFHA-PEB. The voltammograms obtained with HA-PEB modified cavity microelectrode showed the appearance of new redox couples reflecting the adsorption of HA on PEB. Metal-humic acid-polyaniline voltammograms were characterized by appearance of oxidation-reduction couples or reduction wave corresponding to metal. Finally, the result may be exploited to develop a biocaptor based on the cavity microelectrode amended by THA-PEB and YHA-PEB