Efficient, selective and mild oxidation of sulfides and oxidative coupling of thiols catalyzed by Pd(II)-isatin Schiff base complex immobilized into three-dimensional mesoporous silica KIT-6

摘要

In this study, a palladium(II)-isatin Schiff base complex immobilized into three-dimensional (3D) mesoporous silica KIT-6 (Pd-isatin Schiff base@KIT-6) was synthesized and characterized by various techniques including inductively coupled plasma (ICP) and Fourier transform infrared (FT-IR) spectroscopies, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) technique and thermal gravimetric analysis (TGA). This new heterogeneous catalyst was successfully employed for the selective oxidation of sulfides to sulfoxides withtert-butyl hydroperoxide (tert-BuOOH) and oxidative coupling of thiols into corresponding disulfides using 30 H(2)O(2)at room temperature. The products were obtained in good to excellent yields and no over-oxidation of sulfoxides and disulfides was observed. This catalytic system could also be applied for the chemo-selective oxidation of sulfides and thiols in the presence of other functional groups. The studied catalyst can be recovered easily by a simple filtration and reused five times in both oxidation reactions without a remarkable decrease in catalytic activity.