Magnetically Retrievable Nano Crystalline Nickel FerriteCatalyzed Aerobic, Ligand-Free C-N, C-O and C-C Cross-Coupling Reactions for the Synthesis of a Diversified Library of Heterocyclic Molecules

A new nickel ferrite nano-crystal-catalyzed, ligand-free strategy for the construction of C-N, C-O, and C-C bonds is presented, in which easily available nitrogen and oxygen nucleophiles, aryl/heteroaryl halides and arylboronic acids are used for the cross-coupling reactions. The reactions can be performed at low catalyst loadings with excellent functional group tolerance and chemoselectivity. A variety of functional groups are compatible with the reaction conditions, including nitro, methoxy, as well as acid- and base-sensitive heteroaromatic groups. This unprecedented chemistry nicely complements classical methods for the N-arylation of amines/heteroamines, the O-arylation of phenols/hydroxycoumarins and biaryl/heteroaryl synthesis. The low cost, easy to handle nature and the simplicity of this catalytic system render the method competitive with comparable copper- and palladium-based protocols which require the presence of sophisticated ligands. Nickel ferrite magnetic nanoparticles were prepared by a simple hydrothermal method and characterized by using XRD, TEM image, energy dispersive X-ray analysis, XPS and FT-IR. The easy recovery of the catalyst and high yield of the products make the protocol attractive, sustainable and economic. The catalyst was reused for five cycles with almost unaltered catalytic activity.