Regioselective Ortho-C-H sulfenylation of free phenols catalyzed by Co(II)-immobilized on silica-coated magnetic nanoparticles

Fe3O4@SiO2-UT@Co-II is prepared by the silica-coated magnetic nanoparticles, urea-triazole, and CoCl2. This organic-inorganic hybride composite showed a good to excellent catalytic activity toward regioselective ortho-sulfenylation of free phenols and naphthols using pivalic anhydride as a directing group, also K2S2O8 and PPh3 were employed as oxidant and additive respectively. The newly synthesized catalyst was fully characterized by using different techniques such as FT-IR, TGA, DTG, TEM, SEM, EDS, ICP and VSM analyses. The competitive price, accessibility and lower toxicity of cobalt compared to expensive transition metals using for C-H bond activation and functionalization constitute precious advantages for this method. Moreover, this heterogeneous catalyst could be magnetically recovered and reused without significant loss of its catalytic activity after five cycles.