Studies On C-S Bond Coupling Reaction And Tandem Reaction Catalyzed By Magnetic Nanocatalysts

Superparamagnetic nanoparticles and composite materials, which possess high surface to volume ratios and have high surface energies, show a high catalytic activity and can be reused after separation from the reaction system by using a magnet. This paper discusses the design and synthesis of magnetic nanocatalyst, specifically about fabrication of magnetic nanocomposites for C-S bond coupling reaction and preliminary studies towards the preparation of magnetic nano-carbene catalyst.1. Aminosilane coupling agent and PEI-600as ligands were loaded to magnetic nano-particles, and uniformed monodisperse nanocomposites CoFe2O4-NH2(Ligand A), Fe3O4@Si(CH2)3NH2(Ligand B), Fe3O4@Si(CH2)3PEI (Ligand C), Fe3O4@Si(CH2)3NHC(O)(CH2)2PEI (Ligand D) and Fe3O4@Si(CH2)3NHC(O)PEI (Ligand E) were obtained. The catalytic applications of the synthesized magnetic nanocomposites were explored for the cross-coupling of heterocyclic thiols with aromatic iodides. The reaction was carried out in the presence of Cul (5mol%), ligand (10mol%N) and K2CO3(1.3eq) in DMF at120℃.A variety of heterocyclic sulfides were prepared in good to excellent yields (up to99%). Ligands B and C had a good catalyst activity after five consecutive cycles.2.5-(Aminomethyl)-2-phenyl-6,7-dihydro-5H-pyrrolo[2,1-c][1,2,4]triazol-2-ium tetrafluorobo-rate was synthesized through8steps. Triazole carbene precursor as a catalyst was crosslinked to Fe3O4nanomaterials by glutaraldehyde for the first time. Infrared spectra and elemental analysis showed that triazole carbene was successful imbolized on nanoparticles surface and the N-heterocyclic carbene loading amount reached0.6764mmol/g. The catalytic application of the synthesized magnetic nano-carbene catalyst was explored for the tandem reaction. The catalyst deactivated due to the interaction of N-heterocyclic carbene as ligand and iron atoms.