Catalytic oxidations using cobalt(II) complexes - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 278

oxocobalt(IV) species, which is regarded as the active
intermediate responsible for the oxidation products formed via O-atom
transfer. These are shown above and under the horizontal row.
Oxometal species have been variously invoked as intermediates in O-
transfer reactions, especially in connection with single oxygen atom donors,
such as iodosylbenzene, persulfate, N-oxides and peroxy compounds 54 .
Oxocobalt(IV) was proposed as the active intermediate in the
cobaloxime(II)-catalyzed oxidation of hydrazobenzene with
3.9 Alkene epoxidation
In the presence of methyl, tert -butyl, or (-)-menthyl esters of 2-
oxocyclopentanecarboxylic acids, the cobalt(II)-salen type complexes and
Jacobsen-type manganese(III) complexes shown in Figure 17 are active
catalysts for alkene epoxidation with dioxygen 56 .
In these epoxidations (Figure 18), alkyl-1-hydroxy-2-oxocyclopentane-
carboxylates and 1-alkyl-2-oxo-hexanedicarboxylic acids are formed as co-
oxidation products.