Benzylic Ligand Hydroxylation Starting from a Dicopper μ‐η2:η2 Peroxo Intermediate: Dramatic Acceleration of the Reaction by Hydrogen‐Atom Donors

Abstract

Radicals in directed pathways: The μ-η2:η2 peroxo CuII2 intermediate 1 shows a much faster benzylic ligand hydroxylation than systems without phenol. This novel reactivity can be further accelerated by addition of external H-atom donors such as TEMPO-H. The results imply initial H-atom transfer leading to the formation of phenoxyl radicals. A highly reactive copper oxyl intermediate is then formed, which inserts oxygen into the benzylic CH bond.