Douniazad El Abed

Palladium‐Based Catalytic System for the Direct C3‐Arylation of Furan‐2‐carboxamides and Thiophene‐2‐carboxamides

The palladium‐catalyzed direct arylation of furans or thiophenes that contained secondary carboxamides at the C2 position proceeded regioselectively at either the C3 or C5 positions, depending on the reaction conditions. The nature of the base was crucial for controlling the regioselectivity of the reaction. We had previously observed that, in the presence of potassium acetate, direct arylation at the C5 position was favored. Herein, we report that the use of cesium carbonate as the base and xylene as the solvent selectively afforded the C3‐arylated furans or thiophenes. The reactivity of furan‐2‐carboxamides and thiophene‐2‐carboxamides were similar. The reaction tolerated a range of functional groups on the aryl bromide and also heteroaryl bromide substrates.

Reactivity of (poly)fluorobenzamides in palladium-catalysed direct arylations

The influence of fluoro-substituents on secondary and tertiary benzamides on the regioselectivity of palladium-catalysed direct arylations was studied. With most (poly)fluoro-substituted tertiary benzamides, the arylations proceed very regioselectively at ortho-positions of the fluoro substituents using 1 mol% of air-stable palladium catalysts and PivOK/DMA as the reaction conditions. With the 3,5-difluoro-substituted secondary benzamides, quite regioselective arylations at C4-positions were observed. For these reactions, a variety of substituents on the aryl bromide, such as ester, propionyl, acetyl, formyl, nitro, nitrile, trifluoromethyl, chloro, fluoro or methyl, was tolerated. These results reveal that under our reaction conditions, fluoro substituents act as better directing groups than amides in the palladium-catalysed direct arylations.

CuCO3–CuO nanocomposite as a novel and environmentally friendly catalyst for triazole synthesis

This paper focuses on the use of natural sources for the preparation of efficient and low cost catalysts. CaCO3 is obtained from cuttlefish bone and was modified by the cation exchange of Ca2+ by Cu2+ in CaCO3 using solutions of copper (Cu(NO3)2) at different concentrations. The modification of the solids was investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and ultraviolet-visible (UV-vis) spectroscopy. The results show that the copper exchanged materials contain a CuCO3–CuO nanoparticle composite. The obtained solids were used as catalysts for the cycloaddition reaction of different azides with activated alkenes at room temperature under liquid phase conditions. The different parameters which affect the reaction were investigated such as reaction time, temperature of the reaction, effect of the copper content, catalyst mass, effect of the solvent and nature of the azide. High yields were obtained when the catalyst contained more copper. The best catalysts were calcined at different temperatures (200, 300, 400, 500 °C) in order to determine whether the active phase was CuCO3 or CuO in the catalytic reaction. The XRD analysis of the calcined composites shows that an increase in calcination temperature leads to the formation of the CuO phase. On the other hand, the use of these calcined materials as catalysts shows that the active phase is copper carbonate. Finally, a new method for preparing triazoles with short reaction times was developed by the use of a cheap environmentally friendly catalyst.

Synthesis of indenone by self-condensation of 1-acetyl-2-methylcyclopentene and subsequent unusual autoxidation

Abstract Potassium tert-butoxide induced self-condensation of 1-acetyl-2-methyl-cyclopentene leads to 6-methyl-4-(2′-methylcyclopent-1′-enyl)bicyclo[4.3.0]non-3-en-2-one 2 in 35% yield when one equivalent of dimethyl sulfate is added. Dienone 2 undergoes facile autoxidation leading to the corresponding epoxide 12 and triketone 13.