Synthesis of new optically pure isoxazolines via 1,3-dipolar cycloaddition of nitrile oxides with allyl esters derived from eugenol

1,3-dipolar cycloaddition of arylnitrile oxides with allyl ester prepared from eugenol afforded new chiral isoxazolines in good yields. The chemical structure of this compounds was characterized by 1H NMR,13C NMR, 2D NMR and TOF-MS analysis. All the cycloadducts were obtained through a regiospecific and stereospecific pathway and all cases, only one isomer was isolated, as established by unambiguous NMR analysi

Benzo[c]phenanthrene derivatives: Synthesis, optical properties and cytotoxic activity

A new benzo[c]phenanthrene ketone has been synthesized through Heck coupling and oxidative photocyclization. The optical properties of the target tetracyclic system were also investigated by UV-visible absorption and photoluminescence spectroscopy and an emission in the visible region was observed. The tetracyclic ketone has been reacted with primary amines in the presence of Lewis acid followed by NaBH4 reduction to provide new polyaromatic secondary amines in good yields and purity. All the synthesized new compounds were identified and characterized through a combination of nuclear magnetic resonance spectroscopy and mass spectrometric methods. The cytotoxic activity of all pure benzo[c]phenanthrene derivatives has been evaluated against Hep-2 cell line using (MTT) colori­metric assay

Conditions for the Palladium-Catalysed Direct 2-Arylation of 3-Bromobenzo[b]thiophene Tolerant of the Benzothienyl Carbon-Bromine Bond

International audiencePhosphine-free palladium(II) acetate catalyst was found to promote the direct 2-arylation of 3-bromobenzo[b]thiophene without cleavage of the benzothienyl carbon-bromine bond, allowing the synthesis of 2-aryl-3-bromobenzo[b]thiophenes in only one step. The best results were generally obtained using a low loading of the palladium catalyst (0.5 mol%), quite low reaction temps. (80-120 °C) and short reaction times (0.5-2 h). The reaction proceeds with electron-deficient para-, meta- and ortho-substituted aryl bromides and also with heteroaryl bromides. The benzothienyl carbon-bromine bond has been profitably employed for further palladium-catalyzed functionalisations. This strategy allows the straightforward synthesis of 2,3-di(hetero)arylated benzo[b]thiophenes with two different (hetero)aryl units via sequential catalytic arylations

Reactivity of 3-(pyrrol-1-yl)thiophenes in Pd-catalysed direct arylations

International audienceThe regioselectivity of the Pd-catalysed direct arylation of 3-(pyrrol-1-yl)thiophene derivatives was investigated. Conditions allowing either the regioselective arylation at C2 or at C5 of the thiophene ring are reported. From methyl 3-(pyrrol-1-yl)thiophene-2-carboxylate using KOAc as the base, DMA as the solvent and only 1 mol % Pd(OAc)2 catalyst, the target 5-arylated thiophenes were obtained in moderate to good yields with a wide variety of aryl halides; whereas the use of 1-(4-methylthiophen-3-yl)-pyrrole affords the C2-arylated thiophenes. The sequential palladium catalysed 2,5-diheteroarylation of such 3-(pyrrol-1-yl)thiophene is also reported allowing the access to thiophenes bearing two different aryl units at C2 and C5. A pyrazole bearing an ester substituent at C4 and a pyrrole substituent at C5 was only arylated at C2 on the pyrrole ring

Conditions for palladium-catalyzed direct arylations of 4-bromo and 4-iodo N-substituted pyrazoles without C-Br or C-I bond cleavage

International audienceThe Pd-catalyzed arylation at the C5 position of N-protected pyrazole derivs. bearing bromo or iodo substituents at the C4 position is described. A simple phosphine-free catalytic system was used, namely, 1 mol% Pd(OAc)2 in DMA in the presence of KOAc as the base. A wide aryl bromide scope as a coupling partner has been coupled with pyrazole derivs. The reaction was very chemoselective as the C-halogen bonds of the pyrazole units were not involved in the C-H bond arylation process. Some examples demonstrating the synthetic potential of the bromo and iodo pyrazole substituents for chem. transformations are reported

Electrochemical Capacitive K + EMIS Chemical Sensor Based on the Dibromoaza[7]helicene as an Ionophore for Potassium Ions Detection

International audienceA K+-sensitive capacitive electrolyte-membrane-insulator-semiconductor (EMIS) based on a novel dibromoaza[7]helicene ionophore has been developed. An ion-sensitive membrane based on polyvinylchloride (PVC) doped with the ionophore was deposited on the Si3N4/SiO2/Si-p/Cu-Al transducer. The properties of the K+-EMIS chemical sensor were investigated by electrochemical impedance spectroscopy (EIS). All the developed devices upon being tested have shown good sensitivity and linearity responses within the range 10(-6) M to 10(-1) M of potassium activity, with good selectivity over a wide variety of other cations (Na+, Li+, Cu2+, Ca2+, and Mg2+). To our knowledge, this is the first time that a capacitive field-effect sensor has been fabricated using helicene as a carrier for K+-detection, combined with the structure: Si3N4/SiO2/Si-p/Cu-Al as a transducer