Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 4, pp. 745−747.
Pleiades Publishing, Ltd., 2010.
Original Russian Text
E.Sh. Kagan, V.P. Kashparova, I.Yu. Zhukova, I.I. Kashparov, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 4,
Oxidation of Alcohols by Iodine in the Presence
of Nitroxyl Radicals Generated Electrochemically
E. Sh. Kagan, V. P. Kashparova, I. Yu. Zhukova, and I. I. Kashparov
South Russian State Technical University (Novocherkassk Polytechnical Institute), Novocherkassk, Russia
Received April 28, 2009
Abstract—Oxidation of primary and secondary alcohols in the two-phase system of methylene chloride–aqueous
solution of sodium hydrocarbonate in the presence of the mediator system of potassium iodide–nitroxyl radical
was studied. It is supposed that under these conditions the iodonium ion generated on a platinum electrode is the
primary oxidizing agent.
Selective oxidation of alcohols up to aldehydes is one of
the oldest problems of organic synthesis. An examination
of published data shows that the most promising is the
method of alcohols oxidation using a catalytic system
containing a nitroxyl radical of the 2,2,6,6-tetramethyl-
piperidine series and an inexpensive primary oxidizing
agent, for example a hypochlorite or other oxidizing
agents including anodic oxidation of a nitroxyl radical [1,
2]. The pathway of the oxidation of organic compounds
using nitroxyl radicals as catalysts is shown in scheme 1.
However in some cases the application of such strong
oxidizing agents as NaOCl is unacceptable, as it can give
rise to the oxidation of other functional groups or to the
halogenation of a substrate . The oxidation of alcohols
can be carried out in mild conditions in the presence of
crystalline iodine and a nitroxyl radical. A disadvantage
of this method is a considerable iodine consumption (2
mol of iodine per 1 mol of alcohol) and the formation of
coproducts (potassium iodide) .
In the present work we have offered the electrochemi-
cal procedure for the oxidation of primary and secondary
alcohols up to corresponding carbonyl compounds with
application of the two-mediator system of nitroxyl radical
(I-III) - potassium iodide:
It is known that in the case of electrochemical oxida-
tion of alcohols in the presence of only potassium iodide
primary alcohols are oxidized up to ethers of acids and
secondary alcohols - up to corresponding ketones. In this
case the iodonium ion is the oxidizing agent [4, 5]. It was
found that the presence of a catalytic amount of a nitroxyl
radical of the 2,2,6,6-tetramethylpiperidine series changes
radically the reaction direction. Primary alcohols in this
case are oxidized only up to corresponding aldehydes. A
possible mechanism of the reaction of alcohols oxida-
tion by the system nitroxyl radical - potassium iodide is
shown in Scheme 2.