Vanadyl Sulfate Embedded in Poly(ethylene glycol) for the Selective Aerobic Aromatic Alcohol Oxidation to Carbonyl Compounds

A poly(ethylene glycol) (PEG)-based composite containing a well-defined, molecular neutral vanadyl sulfate compound was synthesized in dimethylacetamide (DMA) and characterized. The composite material catalyzed the aerobic oxidation of selected aromatic alcohols to carbonyl compounds in DMA (homogeneous reaction condition) under high selectivity, using a very low amount of vanadium (0.5 mol %). The catalytic activity of the composite material turned out to be significantly superior to that of the bare vanadium compound and to reported catalytic results stemming from vanadyl-based catalyst, which use either high reaction temperature and vanadium loading or toxic and expensive additives (i.e. a TOF value for benzyl alcohol conversion of 57 h–1). PEG turned out to be important not only for the catalytic activity of the vanadium-based catalyst but also for the efficient recovery of vanadium. The deactivation of the molecular vanadium catalyst studied by independent recycling experiments and spectroscopic analyses carried out on the recovered catalyst turned out to be due to the formation of polymeric V(III)-O-V(III) species.