Selective Aerobic Oxidation of Hydroxyl Compounds Catalyzed by Dimeric N‑Salicylidene Oxovanadium Complexes

In this study, our focus lies in investigating how the microenvironment surrounding the vanadium center influences the selective aerobic oxidation of alcohols via a tailored ligand design. Under optimized reaction conditions, oxovanadium complex 1a with N-salicylidene-amino alcohol ligands effectively converted various hydroxyl compounds, including primary benzylic, allylic, propargylic, heteroaryl-containing alcohols, lactate, and secondary aromatic alcohols, into their corresponding aldehydes or ketones in high yields without any additives. Complex 1a displayed remarkable reaction stability and featured a binuclear structure containing VV species confirmed by vanadium nuclear magnetic resonance and single-crystal X-ray diffraction analysis. Activating the α-C–H bond is the rate-determining step verified by the kinetic isotopic effect study. The introduction of electron-donating groups on the ligand’s aromatic ring could increase its catalytic activity. Mechanistic studies indicate that the oxovanadium complex undergoes a cycle from VV species to VIV species, validated by electron paramagnetic resonance. These phenomena have implications for the development of efficient metallic complexes for aerobic oxidation processes.