Oxygenation of 2,6-di-t-butylphenols with superoxo Co(III) complexes

Superoxo Co(III) complexes, Co(CN)₅O₂]X]₃ where X = Et₃N⁺ and (Ph₃P)₂N⁺, mediate the dioxygen incorporation into 2,6-di-$\text{t}$-butylphenols ($\text{1}$) with the same regioselectivity as that in the base-catalyzed oxygenation of $\text{1}$. The superoxo species acts as a base but is not incorporated into the substrate.