Iodination of aromatic compounds with iodine and n-butyltriphenylphosphonium peroxodisulfate

Article abstract of DOI:10.1081/SCC-120018691

Iodine and n-butyltriphenylphosphonium peroxodisulfate can be successfully used for the iodination of some aromatic compounds in acetonitrile as solvent. The yields obtained are good to excellent.

Full text of DOI:10.1081/SCC-120018691

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Iodination of Aromatic Compounds with Iodine and n -
Butyl- triphenylphosphonium Peroxodisulfate
H. Tajik a , A. A. Esmaeili b , I. Mohammadpoor-Baltork c , A. Ershadi b & H. Tajmehri a
a Department of Chemistry , College of Science , Guilan University , Rasht, Iran
b Department of Chemistry , College of Science , Beerjand University , Beirjand, Iran
c Department of Chemistry , College of Science , Isfahan University , Isfahan, Iran
Published online: 15 Aug 2006.
To cite this article: H. Tajik , A. A. Esmaeili , I. Mohammadpoor-Baltork , A. Ershadi & H. Tajmehri (2003) Iodination of
Aromatic Compounds with Iodine and n -Butyl- triphenylphosphonium Peroxodisulfate, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 33:8, 1319-1323, DOI: 10.1081/SCC-120018691
To link to this article: http://dx.doi.org/10.1081/SCC-120018691
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 8, pp. 1319–1323, 2003
Iodination of Aromatic Compounds
with Iodine and n-Butyl-
triphenylphosphonium Peroxodisulfate
2
3
H. Tajik,1, A. A. Esmaeili, I. Mohammadpoor-Baltork,
*
A. Ershadi,2 and H. Tajmehri1
1Department of Chemistry, College of Science,
Guilan University, Rasht, Iran
2Department of Chemistry, College of Science,
Beerjand University, Beirjand, Iran
3Department of Chemistry, College of Science,
Isfahan University, Isfahan, Iran
ABSTRACT
Iodine and n-butyltriphenylphosphoniumperoxodisulfate can be
successfully used for the iodination of some aromatic compounds
in acetonitrile as solvent. The yields obtained are good to excellent.
*Correspondence: H. Tajik, Department of Chemistry, College of Science,
Guilan University, Rasht, Iran; E-mail: tajik@kadoas.gu.ac.ir.
1319
DOI: 10.1081/SCC-120018691
Copyright & 2003 by Marcel Dekker, Inc.
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1320
Tajik et al.
Iodoarenes are useful compounds in organic synthesis. Because of
the low reactivity of iodine, the general procedure for halogenation of
aromatic compounds cannot be successfully used for preparation of aryl
iodides. In order to obtain aryl iodides some procedures have been
employed among them we can refer to the following; addition of an
oxidizing agent[1–7] or base,[8,9] iodine monochloride[10,11] (alone or in
the presence of a Lewis acid), N-iodosuccinimide[12] and metal iodide-
oxidizing agent systems.[13–15] Nevertheless, most of them employ acidic
or severe conditions. In most cases the yields of reactions are not high.
Furthermore, there are not simple and reliable methods for their prepara-
tion. Recently, some new systems have been reported especially for direct
iodination of aromatic compounds.[16,17]
In this research we have chosen n-butyltriphenylphosphonium
peroxodisulfate,[18] [(n-BuPPh3)2S2O8], as oxidizing agent and molecular
iodine to iodinate aryl ethers, phenols, and aromatic carboxylic acids as
shown in Table 1.
According to the optained results, this method describes a mild and
convenient way of iodinating aromatic rings. Aromatic ethers can be
quantitatively iodinated by this system. The compounds which contain
electron donating groups give para substitiuted products (Table 1).
In some cases where the para position is blocked, no reaction was
observed even after a long reaction time (Table 1, Entries 6,7). Aromatic
compounds which are deactivated were also directly iodinated in meta
position in relatively good yields (Table 1, Entries 8,11), which to the best
of our knowledge was not reported in the literatures. Phenols and
aromatic amines, however, gave mostly the oxidation products that
was not intended in this research.
In all of the cases, parallel reactions were performed to check the
oxidation products. According to the results obtained no oxidation
product was observed for all of the substrate given in Table 1.
EXPERIMENTAL
All products were identified by comparison of their spectral and
physical data with those of the known samples.[19] The purity of the
products was checked by TLC on silica gel polygramSIL G UV 254
plates. n-Butyltriphenylphosphoniumperoxodisulfate was prepared
according to Ref.[18] Other chemicals were purchased from the
Merck chemical company. Products were separated and identified by
different chromatography techniques, and also identified by comparison

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Iodination of Aromatic Compounds
1321
Table 1. Iodination of some aromatic compounds with iodine and (n-Bu
PPh3)3S2O8 in acetonitrile under reflux (substrate/iodine/oxidant; 1:1:1).
Entry
1
Substrate
Product
Reaction time (h)
0.5
Yield (%)
100
2
3
4
0.4
0.5
0.5
100
100
100
5
2
100
6
7
8
—
—
20
20
3
—
—
80
9
10
11
15
15
2
70
80
70
of their m.p., b.p., IR, and NMR spectra and refractive index with those
reported for the authentic samples.
General procedure: To a solution of aromatic compound (1 mmol),
iodine (1 mmol) and n-butyltriphenylphosphoniumperoxodisulfate were
added and refluxed for 0.25–20 h. Progress of the reactions was moni-
tored by TLC or GC (capillary column). The reaction mixture was cooled
to room temperature and the excess of iodine was removed by dropwise
addition of sodiumthiosulfate solution (1 M). The colorless solution was
transferred to a separatory funnel and the organic layer was separated

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1322
Tajik et al.
and dried with magnesium sulfate or calcium chloride. Evaporation of
the solvent followed by column chromatography on silica gel gave the
corresponding compounds from good to excellent yields (Table 1).
ACKNOWLEDGMENT
We are thankful of Guilan University Research Council for partial
support of this work.
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Received in the USA February 4, 2002

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