Multicomponent Azide-Alkyne Cycloaddition Catalyzed by Impregnated Bimetallic Nickel and Copper on Magnetite

A new bimetallic catalyst derived from nickel and copper has been used successfully for the first time in the multicomponent reaction of terminal alkynes, sodium azide, and benzyl bromide derivatives. The presence of both metallic species on the surface of magnetite seems to have a positive and synergetic effect. The catalyst loading is the lowest ever published for a catalyst of copper anchored on any type of iron support. The catalyst could be easily removed from the reaction media just by magnetic decantation and it could be reused up to ten times without any negative effect on the initial results.

Silica Microparticles Supported Gold and Copper Ferrite Nanoparticles: A Magnetically Recyclable Bimetallic Catalyst for Sonogashira Reaction

Novel silica supported gold and copper ferrite nanoparticles (NPs) have been synthesized, characterized and used as a separable dual catalyst in Sonogashira type reaction. These Au.CuFe2O4@Silica NPs show a high efficiency as catalyst in the alkynylation not only of aryl iodides but also aryl bromides. By using only 0.5 mol% loading and t-BuOK as base in N,N-dimethylacetamide as solvent, aryl iodides react at 115 ºC in 1 d, whereas for aryl bromides the cross-coupling takes place at 130 ºC in 2 d. The catalyst can be successfully recycled using an external magnet for four consecutive runs.

Removal of BrO3 − from drinking water samples using newly developed agricultural waste-based activated carbon and its determination by ultra-performance liquid chromatography-mass spectrometry

Activated carbon was prepared from date pits via chemical activation with H3PO4. The effects of activating agent concentration and activation temperature on the yield and surface area were studied. The optimal activated carbon was prepared at 450 °C using 55 % H3PO4. The prepared activated carbon was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric-differential thermal analysis, and Brunauer, Emmett, and Teller (BET) surface area. The prepared date pit-based activated carbon (DAC) was used for the removal of bromate (BrO3 −). The concentration of BrO3 − was determined by ultra-performance liquid chromatography-mass tandem spectrometry (UPLC-MS/MS). The experimental equilibrium data for BrO3 − adsorption onto DAC was well fitted to the Langmuir isotherm model and showed maximum monolayer adsorption capacity of 25.64 mg g−1. The adsorption kinetics of BrO3 − adsorption was very well represented by the pseudo-first-order equation. The analytical application of DAC for the analysis of real water samples was studied with very promising results.

Enantioselective Synthesis of exo-4-Nitroprolinates from Nitro­alkenes and Azomethine Ylides Catalyzed by Chiral Phosphor­amidite·Silver(I) or Copper(II) Complexes

Chiral complexes formed by privileged phosphoramidites derived from chiral binol and optically pure Davies’ amines, and copper(II) triflate, silver(I) triflate or silver(I) benzoate are excellent catalysts for the general 1,3-dipolar cycloaddition between nitroalkenes and azomethine ylides generated from α-amino acid derived imino esters. These three methods can be conducted at room temperature to afford the exo-cycloadducts (4,5-trans-2,5-cis-4-nitroprolinates) with high diastereoselectivity and high enantioselectivity. In general, the three procedures are complementary but silver catalysts are more versatile and less sensitive to sterically congested starting materials.

Cobalt-Impregnated Magnetite as General Heterogeneous Catalyst for the Hydroacylation Reaction of Azodicarboxylates

Catalysts consisting of cobalt and nickel impregnated on magnetite have been prepared, characterized and used for the hydroacylation reaction of different azodicarboxylate compounds with aldehydes, using nearly stoichiometric amounts of both reagents in only 3 h. Furthermore, this reaction has been conducted with the smallest amount of catalyst. The cobalt catalyst is stable enough to be removed by magnetic decantation and recycled ten-fold without any detrimental effect on the results.