Catalytic oxidations using cobalt(II) complexes - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 307

6. Catalytic Oxidations using Cobalt(II) Complexes 307

Phosphite ion coordinated to dinuclear
complex is oxidized to phosphate via apparent -atom insertion

into the P-H bond, which resembles a hydroxylation reaction 151 . The
proposed mechanism (Figure 51) of phosphite to phosphate oxidation within
the

O

complex involves the intermediate in Figure 52.

8. OXIDATIONS CATALYZED BY COBALT(II)
PYRIDINE COMPLEXES

8.1 epoxidation

In the presence of t -BuOOH and or as

catalyst, undergoes oxidation by to pinene oxide (PO),

-verbenol (Vol) and verbenone (Vone) (Figure 53) 152-154 . Typically 8-12
mol%

t ra ns

a n d 0.15 mol% catalyst are used in at 60-100°C. In
reaction times of 24 hours, a maximum of 60% verbenone is obtained. Initial
Co(II) to Co(III) oxidation of the catalyst by

t -BuOOH

t -BuOOH affords butoxy and

butylperoxy radicals. The -

pinene, producing an allyl radical, which reacts with yielding trans-
verbenol and verbenone. The butylperoxy radical adds to the double bond of
The resulting alkylperoxy radical decomposes to pinene oxide.

former abstracts an allyli c hydrogen from α