Solvent-free selective oxidation of alcohols with tert-butyl hydroperoxide catalyzed by palladium(II) isatin Schiff base complex supported into three-dimensional mesoporous silica KIT-6

Abstract

In this work, the catalytic activity of a palladium(II) isatin Schiff base complex immobilized into mesoporous silica KIT-6 (Pd-isatin Schiff base@KIT-6) was studied for the oxidation of different alcohols with tert-butyl hydroperoxide (TBHP, 70% aqueous solution) as an oxidant under solvent-free conditions. To find the suitable reaction conditions, the effect of essential factors including the solvent, temperature, catalyst amount and kind of oxidant on the oxidation of benzyl alcohol was explored. The results showed that in this catalytic system, the corresponding aldehydes and ketones were obtained with high to excellent yields at 50 °C without the formation of carboxylic acids as by-products. The catalyst was easily recovered by simple filtration and reused in five subsequent reaction cycles without any significant loss in the catalytic activity. Moreover, the comparison of the Fourier transform infrared (FT-IR) spectrum, X-ray diffraction (XRD) pattern, scanning and transmission electron microscopy (SEM and TEM) images of the used catalyst with a fresh one showed that the structure of the Pd-isatin Schiff base@KIT-6 catalyst remained intact after five times of reuse.