Scheme 4. Proposed Pathways for [Cu^II(O₂^•–)]⁺ Reactivity with p-OMe-DTBP or p-^tBu-DTBP Substrates Leading to Observed Products.

See text for detailed descriptions of direct/indirect evidence or literature support for the individual reaction steps or intermediates described. EPR spectra observed for (A ≡ A′) (from mixing 2 and p-X-DTBP at −90 °C), for LCu^II–OH(H) (observable at room temperature and refreezing to record EPR spectra) are indistinguishable; see Figure S7 and caption.