Copper-dioxygen complexes and their roles in biomimetic oxidation reactions - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 103

special proximity or stereoelectronic features that are absent in the solution
model chemistry.

Overview . The chemistry described in Scheme 5 (XYL system) may
best model the hydroxylation function of tyrosinase with its dicopper active
site. Other very different copper monooxygenases include dopamine
and peptidylglycine monooxygenase)
(PAM) (Table 1), which are important pharmacological targets due to their
roles in regulating neurotransmitters and polypeptide hormones. Models for
benzylic hydroxylation chemistry in (see below) and oxidative N-
dealkylation chemistry in PAM 9 have appeared. From the interest in C-H
activation chemistry, an important target for future chemical modeling is the
copper-dependent particulate methane monooxygenase

3.4 Aliphatic Hydroxylation

Synthetic copper complexes which can activate dioxygen and
hydroxylate aliphatic C-H bonds are of great importance, both for shedding
light on common industrial processes which employ copper catalysts and also
as models for the copper monooxygenases mentioned above, such as
PAM, and pMMO.
One such system is the one reported by Itoh and co-workers, 109 which
employs a tridentate ligand, N,N -bis[2-(2-pyridyl)ethyl]-2-phenylethylamine

-bis[2-(2-pyridyl)ethyl]-benzylamine (PY2Bz), a
ligand that was previously studied in our laboratories. 65 When the
mononuclear Cu(II) complex was treated with one
equivalent of a two electron reductant (a 1,2-enediolate derived from benzoin
and triethylamine) under Ar, then exposed to for several hours, the
dinuclear copper(II) compound with bridging alkoxide ligands forms,
demonstrating that benzylic hydroxylation of the ligand occurs. Removal of
the copper from the ligand confirms that the yield of the ligand hydroxylation
was 100%. When the well-characterized copper(I) complex
was treated with the isolated yield of the hydroxylated ligand was the
maximum 50% (Scheme 8). Although the only copper-dioxygen adduct
detected in these reactions is a

(PY2Phe), similar to N,N

species, the authors