Mechanistic study of asymmetric oxidative biaryl coupling: Evidence for self-processing of the copper catalyst to achieve control of oxidase vs oxygenase activity

Copper(I) and copper(II) 1,5-diaza-cis-decalin complexes [(N(2))Cu] are effective precatalysts for aerobic oxidative coupling of naphthol substrates. Mechanistic studies, however, reveal that these complexes are not the reactive form of the catalyst under steady-state conditions. Rather, the active catalyst forms in a presteady-state self-processing step that involves oxygenation of the naphthol substrate. The oxygenated substrate, NapH(OX), serves as a cofactor that combines with the (N(2))Cu complexes to achieve highly selective, steady-state oxidase reactivity (aerobic oxidative biaryl coupling).