Phosphotungstic acid impregnated niobium coated superparamagnetic iron oxide nanoparticles as recyclable catalyst for selective isomerization of terpenes.

Conversion efficiency as high as 80-100% and 50% selectivity for camphene and limonene was achieved with low production of polymeric byproducts (18-28%), easy recovery with a magnet and reuse for up to five cycles maintaining similar activity and distribution of products, using a new magnetically recyclable catalyst based on niobium oxide coated on superparamagnetic iron oxide nanoparticles (SPION) impregnated with phosphotungstic acid (HPW). The catalyst was demonstrated to be effective in the selective conversion of alpha and beta-pinenes into valuable terpenes, under ultrasonic probe activation and with toluene as solvent. A unique synergic effect between the components generating more active and selective catalytic sites was demonstrated, indicating that the SPION covered with 30 wt% of Nb2O5 gives the best performance when impregnated with HPW as co-catalyst. The materials were fully characterized by XRD, EDX, XPS, TEM, BET, VSM and FTIR.

2-[(4-Chloro-phen-yl)selan-yl]-3,4-di-hydro-2H-benzo[h]chromene-5,6-dione: crystal structure and Hirshfeld analysis.

The title organoselenium compound, C19H13ClO3Se {systematic name: 2-[(4-chloro-phen-yl)selan-yl]-2H,3H,4H,5H,6H-naphtho-[1,2-b]pyran-5,6-dione}, has the substituted 2-pyranyl ring in a half-chair conformation with the methyl-ene-C atom bound to the methine-C atom being the flap atom. The dihedral angle between the two aromatic regions of the mol-ecule is 9.96 (9)° and indicates a step-like conformation. An intra-molecular Se⋯O inter-action of 2.8122 (13) Šis noted. In the crystal, π-π contacts between naphthyl rings [inter-centroid distance = 3.7213 (12) Å] and between naphthyl and chloro-benzene rings [inter-centroid distance = 3.7715 (13) Å], along with C-Cl⋯π(chloro-benzene) contacts, lead to supra-molecular layers parallel to the ab plane, which are connected into a three-dimensional architecture via methyl-ene-C-H⋯O(carbon-yl) inter-actions. The contributions of these and other weak contacts to the Hirshfeld surface is described.

Ni-catalyzed ketene cycloaddition: a system that resists the formation of decarbonylation side products.

Ni-phosphine complexes were used as catalysts for the cycloaddition of various ketenes and diynes. In general, 2,4-cyclohexadienones were formed instead of products arising from decarbonylation of the ketenes.

Dihydropyrimidin-(2H)-ones obtained by ultrasound irradiation: a new class of potential antioxidant agents.

An efficient and simple synthetic protocol for the Biginelli reaction has been developed for the preparation of several new dihydropyrimidinones, under ultrasound irradiation in the presence of NH(4)Cl, in good yields and short reaction time. Some of the synthesized compounds were tested in vitro for their antioxidant activity. All of the selected compounds showed some antioxidant activity. Analogues compounds 3b and 4b exhibited a strong activity against lipid peroxidation induced by Fe + EDTA, while compounds 3b and 3d were the most potent in reducing ROS levels.

Suzuki-Miyaura cross-coupling reactions of aryl tellurides with potassium aryltrifluoroborate salts.

[reaction: see text] Palladium(0)-catalyzed cross-coupling between potassium aryltrifluoroborate salts and aryl tellurides proceeds readily to afford the desired biaryls in good to excellent yield. The reaction seems to be unaffected by the presence of electron-withdrawing or electron-donating substituents in both the potassium aryltrifluoroborate salts and aryl tellurides partners. Biaryls containing a variety of functional groups can be prepared. A chemoselectivity study was also carried out using aryl tellurides bearing halogen atoms in the same compound. In addition, this new version of the Suzuki-Miyaura cross-coupling reaction was monitored by electrospray ionization mass spectrometry where some reaction intermediates were detected and analyzed.