An Unexpected Controlled New Oxidant: SO4(·-).

A controlled new oxidant sulfate radical anion (SO4(·-)) was found and it can be easily prepared by mixing Na2S2O4 and TBHP with stirring. In this new metal-free oxidation system (Na2S2O4/TBHP), SO4(·-) can be used as a controllable oxidant to oxidize various aromatic alcohols to the corresponding aldehydes in good yields without any acid formation at room temperature. SO4(·-) was determined by a DMPO (5,5-dimethyl-1-pyrroline-N-oxide) spin-trapping EPR method at room temperature on a Bruker E500 spectrometer and the results suggested that SO4(·-) was generated in this transformation.