Heterogeneous magnetic catalyst for S-arylation reactions

A convenient method for the synthesis of monodisperse, superparamagnetic copper ferrite (CuFe2O4) nanoparticles with high surface area has been described. The synthesized material was characterized by various techniques. XRD showed the nanocrystalline nature of CuFe2O4 with a crystallite size of 6 nm. TEM analysis showed that uniform spherical CuFe2O4 particles are formed with a size of 55 +/- 5 nm. N-2 adsorption/desorption measurements confirmed the mesoporous nature of the sample with surface area >216 m(2) g(-1). The field dependent magnetization, illustrated by VSM and saturation magnetization was found to be 44 emu g(-1). The catalytic applications of the synthesized CuFe2O4 nanoparticles were explored for the cross-coupling of thiols with diverse range of aryl halides. Aryl iodides and bromides result in biarylsulfides in good to excellent yields (62-98%) whereas aryl chlorides gave significant amount of diaryldisulfide. Scope of this catalytic protocol further extended to one-pot synthesis of biologically important tricyclic dibenzothiazepines. The superparamagnetic nature of CuFe2O4 nanoparticles was found to be advantageous for their easy, quick and quantitative separation from the reaction mixture. Negligible leaching of Cu and Fe in consecutive cycles makes the catalyst economical and environmentally benign. (C) 2012 Elsevier B.V. All rights reserved.