Catalytic oxidations using cobalt(II) complexes - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 276

3.6 Oxidation of quercetin

Quercetinase is a dioxygenase, catalyzing the insertion
of into quercetin and 3-hydroxyflavones, leading to oxidative cleavage of
the heterocyclic ring, affording the corresponding depsides and carbon
monoxide (Figure 13) 36 . Model studies of oxygenations have been reported
using copper(II) complexes 37 . Co(salen) exhibits a remarkable activity in the
cleavage of model substrate (Figure 14) 38 .
Cyclic voltammetry of the substrate anion-catalyst binary intermediate
complex indicates that it is the substrate anion involved in an ion-pair
complex with the cationic that inserts dioxygen,

yielding the product depside 39 HL 2 .

3.7 Mercaptoethanol

Co(salen) immobilized on silica, layered double hydroxides and NaX
zeolite act as photocatalysts for the oxidation of 2-mercaptoethanol and
sodium thiosulfate 40 .

3.8 Alkenes and alcohols

In the presence of cobalt(II) Schiff-base complexes some ketoesters and