Mn(III)-salan/grapheneoxide/magnetite nanocomposite as a highly selective catalyst for aerobic epoxidation of olefins

A nanocomposite was synthesized using carbon-coated Fe3O4 nanoparticle-decorated reduced graphene oxide as a convenient and efficient supporting material for grafting of a manganese-reduced Schiff base (salan) complex via covalent attachment. The nanocomposite was characterized using X-ray diffraction, Fourier transform infrared and diffuse reflectance UV-visible spectroscopies, inductively coupled plasma atomic emission spectrometry and scanning electron microscopy. It was evaluated as a catalyst for the aerobic epoxidation of olefins in acetonitrile in combination with a sacrificial co-reductant (isobutyraldehyde). The catalytic performance of the heterogeneous system of the Mn-salan complex is superior to that of the homogeneous one. The catalyst activity strongly depends on the reaction temperature and nature of the solvent. The epoxide yield increases with the nucleophilic character of the olefin. The nanocomposite performs well as an epoxidation catalyst for electron-rich and conjugated olefins. It can be recovered from the reaction medium by magnetic decantation and reused, maintaining good catalytic activity. Copyright (C) 2016 John Wiley & Sons, Ltd.