A new magnetically recoverable nanocatalyst was prepared by coating magnetite with niobium oxide (Fe3O4@Nb2O5) by using a simple wet impregnation method. The Fe3O4@Nb2O5 nanocatalyst was fully characterized, and its catalytic activity was evaluated by using the one‐pot, three‐component Biginelli reaction, with the aim to synthesize 1,4‐dihydropyrimidinones, a class of compounds with diverse pharmacological properties. The developed protocol was applied to a wide range of aliphatic and aromatic substrates, and structurally diverse products were obtained in excellent yields. Compared with copper and nickel nanocatalysts, the Fe3O4@Nb2O5 nanocatalyst demonstrated superior catalytic activity at a remarkably low catalyst loading (0.1 mol %). This niobium nanocatalyst could be easily separated from the reaction mixture with an external magnet and was reused several times without any loss of its catalytic activity. Moreover, although the Biginelli reaction is a century‐old reaction, its mechanism is still a controversial subject, and our investigation provided an insight into the reaction mechanism.

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This study was designed to examine the antioxidant activity in vitro of novel mono- and diselenide compounds. We compared whether the formation of p-methyl-selenol from compounds 1-phenyl-3-(p-tolylselanyl)propan-2-amine (C1) and 1,2-dip-tolyldiselenide (C4) and o-methoxy-selenol from compounds 1-(2-methoxyphenylselanyl)-3-phenylpropan-2-amine (C2) and 1,2-bis(2-methoxyphenyl)diselenide (C3) may be involved in their antioxidant effects. The compounds were tested against Fe(II) and sodium nitroprusside (SNP)-induced lipid peroxidation in rat brain and liver homogenates. Likewise, the antioxidant capacity of the compounds was assessed by their ability to decolorize the DPPH radical as well as the Fe(II) chelating assay through the reduction of molybdenum(VI) (Mo6+) to molybdenum(V) (Mo5+). This colorimetric assay was also used to quantify thiol peroxidase (GPx) and oxidase activity and thioredoxin reductase (TrxR) activity. The results showed that the novel selenide compounds inhibit the thiobarbituric acid reactive species (TBARS) induced by different pro-oxidants, but the monoselenides effects were significant only at concentrations higher than the concentrations of the diselenides. Similarly, the total antioxidant activity was higher in the diselenides. Moreover, GPx and TrxR activity was only observed for the diselenides, which indicates that these compounds are more stable selenol molecules than monoselenides.

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disubstituierte Dithiocarbamate) sind nicht nur geeignet, den Schwefelwasserstoff fast vollig als Fallungsreagenz zu ersetzen, sondern ermoglichen darUber hinaus neue, wichtige und quantitative Trennungsmoglichkeiten sowie brauchbare spezifische Nachweisreaktionen. Es wird eine ubersicht uber die Reaktionen und ihre Bedingungen, die Anwendung sowie die Herstellung d e r ,,Carbate" gegeben. a) Vorbereitende Bemerkungen