Magnetic Nanoparticles Linked to Pyridinium Hydrotribromide Groups as Catalysts for Selective Oxidation of Alcohols and Protection of Alcohols.

In this research, a novel magnetic nanocatalyst based on iron oxide nanoparticles linked with pyridinium hydrotribromide (Fe3O4@PyHBr3) was synthesized in three steps. In the first step, 3-(aminopropyl)triethoxysilane (APTES) was reacted with 4-(bromomethyl)pyridine hydrobromide. In the second step, the product obtained in the first step was reacted with iron oxide nanoparticles. In the last step, a grinding reaction was carried out with KBr and HIO4 in a mortar. The Fe3O4@PyHBr3 nanocatalyst was characterized by FT-IR, CHN, XRD, SEM, TGA and VSM analysis. The magnetic nanocatalyst was used as a catalyst for the selective oxidation of alcohols to aldehydes and ketones using 30% H2O2 as oxidant in a short time and with high yields. Moreover, no overoxidation of the alcohols was observed. The nanocatalyst was efficiently recycled in five consecutive cycles without significant loss of its catalytic activity. Moreover, trimethylsilylation and tetrahydropyranylation of alcohols were carried out in the presence of this nanocatalyst.