Organic Electrosynthesis - Fundamentals and Applications of Organic Electrochemistry - page 205

the oxidation of alcohols. N -Oxyl adsorbed on
the surface of silica gel disperse mediatory
system has been developed ( Figure 6.6 ) [10].
(6.3)
In this dispersive system, Br − is at first
anodically oxidized to generate Br + , which
oxidizes N -oxyl on the silica gel to form
oxoammonium ion (N=O + ) followed by
oxidation of alcohols to produce ketones. In this
case, the oxidation can be achieved without
organic solvent. One of advantages of the
dispersed system is as follows. After
electrolysis, electrolytic solution is filtered and
the remaining silica gel is washed with
appropriate solvents like acetone to provide the
product. However, during washing, the
mediator also dissolves into the organic solvent.
In order to avoid dissolution of the mediator,
N -oxyl-immobilized silica gel was developed as
a readily recyclable mediator [11].
N -Oxyl-immobilized polymer particles have
also been developed. Furthermore, the
combination of electrodes modified with
TEMPO-immobilized polymer and chiral bases
is known to be highly useful for asymmetric
synthesis [12] (see also section 5.3).