Reduction of the Diazo Functionality of α-Diazocarbonyl Compounds into a Methylene Group by NH3BH3 or NaBH4 Catalyzed by Au Nanoparticles

Supported Au nanoparticles on TiO2 (1 mol%) are capable of catalyzing the reduction of the carbene-like diazo functionality of α-diazocarbonyl compounds into a methylene group [C=(N2) → CH2] by NH3BH3 or NaBH4 in methanol as solvent. The Au-catalyzed reduction that occurs within a few minutes at room temperature formally requires one hydride equivalent (B-H) and one proton that originates from the protic solvent. This pathway is in contrast to the Pt/CeO2-catalyzed reaction of α-diazocarbonyl compounds with NH3BH3 in methanol, which leads to the corresponding hydrazones instead. Under our stoichiometric Au-catalyzed reaction conditions, the ketone-type carbonyls remain intact, which is in contrast to the uncatalyzed conditions where they are selectively reduced by the boron hydride reagent. It is proposed that the transformation occurs via the formation of chemisorbed carbenes on Au nanoparticles, having proximally activated the boron hydride reagent. This protocol is the first general example of catalytic transfer hydrogenation of the carbene-like α -ketodiazo functionality.

Ligand-Free (Z)-Selective Transfer Semihydrogenation of Alkynes Catalyzed by in situ Generated Oxidizable Copper Nanoparticles

Herein, we present (Z)-selective transfer semihydrogenation of alkynes based on in situ generated CuNPs in the presence of hydrogen donors, such as ammonia-borane and a green protic solvent. This environmentally-friendly...

Effect of KOH Pretreatment on Lignocellulosic Waste for the Reduction of Nitrobenzene to Aniline without Metal

A green reduction of nitrobenzene to aniline was carried out using lignocellulosic biomass as a hydrogen source in a subcritical polar protic solvent, such as water and alcohol. The method is simple to implement, inexpensive, and easily applicable on a larger scale. The present method does not demand elaborated experimental conditions nor any metal catalyst. Optimal conditions provided aniline with a 90% yield by reduction of nitrobenzene in the presence of sawdust impregnated by KOH in subcritical methanol at 240 °C for 6 h.

Electrochemistry of Br−/Br2 Redox Couple in Acetonitrile, Methanol and Mix Media of Acetonitrile–Methanol: An Insight into Redox Behavior of Bromide on Platinum (Pt) and Gold (Au) Electrode

Electro-oxidation of Br− on platinum and gold electrode was studied in acetonitrile, methanol and mix media of acetonitrile–methanol. The mechanism of Br− oxidation in these media was investigated using CV, Semi Integration Cyclic Voltammetry, and Digital Simulation technique. Since, Br− oxidation mechanism on platinum involves the formation of Br3− as intermediate, therefore, Kstab for Br3− formation in the mixed media was estimated using digital simulation, Nelson and Iwamoto method. Redox mechanism of Br− and Br2 on gold (Au) electrode was also investigated in protic solvent such as H2O, methanol, ethanol, 1-butanol, and formic acid. It was ascertained that Br− oxidation on gold (Au) electrode in these above protic solvents involve [AuBr2]− intermediate rather than Br3−.