Russian Journal of Organic Chemistry, Vol. 41, No. 6, 2005, pp. 935–936. From Zhurnal Organicheskoi Khimii, Vol. 41, No. 6, 2005, pp. 952–953.
Original English Text Copyright © 2005 by Hashemi, Akhbari.
SHORT
COMMUNICATIONS
Efficient Solvent-Free Oxidation of Phenols to p-Quinones
with Iodic Acid on the Surface of K10 Montmorillonite*
M. M. Hashemi and M. Akhbari
Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran
e-mail: mhashemi@sharif.edu
Received January 15, 2004
Solid-phase organic reactions make it possible to
obtain various compounds and constitute an attractive
field of organic synthesis [1–3]. The use of montmoril-
lonite clays ensured exceptionally important advances
in manufacture of products of fine organic synthesis
supports were tested, in particular clay, aluminum
oxide, K10 montmorillonite, and silica gel. The best
results from the viewpoint of the purity of products
were obtained with the use of K10 montmorillonite.
The reactions were carried out by mixing the corre-
sponding phenol with iodic acid in the presence of K10
montmorillonite, followed by irradiation of the mixture
in a microwave oven or by heating on a water bath
over a period indicated in table. No o-quinones were
detected among the oxidation products. When potas-
sium or sodium iodate was used as oxidant, the yields
were lower. Poor yields were also obtained in the
absence of K10 montmorillonite.
The mechanism of oxidation was not studied spe-
cially. Presumably, the presence of montmorillonite as
acidic support under conditions of microwave irradia-
tion enhances the reactivity of phenols and favors
formation of polar intermediates, thus increasing the
reaction rate [15]. No oxidation occurred without
microwave irradiation.
[
1, 4]. Derivatives of quinones exhibit biological activ-
ity and are important intermediate products in the
synthesis of drugs such as anthracycline antibiotics and
anthracyclinones [5]. In addition, they are used as
oxidants and aromatizers. Therefore, oxidation of
phenols to the corresponding quinones is of great
significance for organic synthesis. Although numerous
procedures have been reported [6], search for new
methods of oxidation of phenols to quinones remains
an important problem. Reactions occurring in the ab-
sence of a solvent under microwave irradiation may be
carried out in open vessels on a preparative scale [7].
The transformation of phenols into quinones may
be effected with the aid of such oxidants as potassium
bichromate [8], sodium nitrate [9], hydrogen peroxide
The use of iodic acid for oxidation of phenols to
p-quinones was reported in [16, 17]. The reactions
were performed in sulfuric acid as solvent. However,
low yields of the products, high temperature, long
reaction time, and laborious isolation procedure make
this method unsuitable from the preparative viewpoint.
[
10], ozone [1], and some bacteria [12, 13]. Most these
procedures require severe conditions [8, 10, 11], give
poor yields of the target products [9, 10], and include
laborious workup [12, 13].
In continuation of our studies on the use of micro-
wave irradiation to accelerate chemical reactions [14],
the present communication describes oxidation of
phenols to the corresponding p-quinones with iodic
All reagents used were commercial products
(
Merck, Fluka, Aldrich). The products were isolated
and purified by column chromatography. All the prod-
ucts were reported previously; they were identified by
acid (HIO ) in the presence of K10 montmorillonite
3
1
under microwave irradiation (see table). The polar
character of phenol derivatives and iodic acid should
favor their reaction in a microwave oven.
the melting points and IR and H NMR spectra.
General procedure for oxidation of phenols to
p-quinones. A mixture of iodic acid (2 mmol), K10
2
Both substituted phenols and unsubstituted com-
pound were quickly oxidized to the corresponding
quinones in the absence of a solvent. Various mineral
montmorillonite (2 g, specific surface 200 m /g,
Fluka), and the corresponding phenol (1 mmol) was
thoroughly ground in a mortar. The resulting mixture
was irradiated in a microwave oven or heated on
a boiling water bath under atmospheric pressure over
*
The original article was submitted in English.
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070-4280/05/4106-0935 © 2005 MAIK “Nauka/Interperiodica”