Electron Transfer Oxidation of Benzene and Aerobic Oxidation to Phenol

The activation of very strong C–H bonds, such as those found in benzene, is important also in the quest for new routes for its functionalization. Using the H5PV2Mo10O40 polyoxometalate as an electron transfer oxidant in >50% aqueous H2SO4 as solvent, the formation of a benzene radicaloid species at RT as probed by visible spectroscopy and by EPR spectroscopy recorded at X-band and W-band, including ELDOR-detected NMR, was verified. The viability of the ET oxidation of benzene is supported by DFT calculations, showing the reaction to be exergonic under these conditions. Furthermore, we show that in the presence of O2, very selective hydroxylation to phenol took place.