Novel, water-based procedure for the mono iodination of aromatic amines and phenols

Article abstract of DOI:10.1080/00397910600602750

A mixture of potassium chlorate and potassium iodide was found to be a good iodinating agent for various aromatic amines and phenols with excellent yields in the presence of mineral acid in aqueous medium. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910600602750

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Novel, Water‐Based Procedure for the Mono
Iodination of Aromatic Amines and Phenols
R. Sathiyapriya a & R. Joel Karunakaran a
a Department of Chemistry, Madras Christian College, Chennai, Tamilnadu,
India
Version of record first published: 18 Aug 2006
To cite this article: R. Sathiyapriya & R. Joel Karunakaran (2006): Novel, Water‐Based Procedure for the
Mono Iodination of Aromatic Amines and Phenols, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 36:13, 1915-1917
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Synthetic Communicationsw, 36: 1915–1917, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600602750
Novel, Water-Based Procedure
for the Mono Iodination of Aromatic
Amines and Phenols
R. Sathiyapriya and R. Joel Karunakaran
Department of Chemistry, Madras Christian College, Chennai,
Tamilnadu, India
Abstract: A mixture of potassium chlorate and potassium iodide was found to be a
good iodinating agent for various aromatic amines and phenols with excellent yields
in the presence of mineral acid in aqueous medium.
Keywords: Aqueous medium, aromatic iodination, potassium chlorate, potassium
iodide
The aromatic iodination reactions are important electrophilic substitution
reactions and the resultant iodo products are useful intermediate in organic
syntheses as they can be easily involved in the metal-catalyzed cross-
coupling reaction.[1] Because of their potential ability as bioactive materials,
most of the iodo derivatives are widely used in the biomedical area.[2]
Iodination of organic substrates simply by molecular iodine is not
possible because of its least reactive nature. Hence, an oxidant is used along
with diiodine to get more reactive electrophilic species. Various oxidants
such as chromium oxide,[3] silver sulphate,[4] sodium iodate,[5] and HIO3
[6]
have been used along with elemental iodine for the effective iodination
process. These iodination reactions are routinely performed in an organic
solvent in the presence of a catalytic amount of acid. The other procedures
using iodonium ion-donating reagents (iodine mononochloride,[7] N-iodosuc-
cinimide,[8] N-iodosuccinimide-trifluoroacetic acid,[9] NaI-chloramine-T,[10]
Received in India December 26, 2005
Address correspondence to R. Joel Karunakaran, Department of Chemistry, Madras
Christian College, Tambaram, Chennai 600059, Tamilnadu, India. Tel.: þ 91-44-
22271458; E-mail: joelkarunakaran2005@yahoo.com
1915

1916
R. Sathiyapriya and R. J. Karunakaran
and NaI/conc. H2SO4[11]) are also reported. As in the case of aromatic iodina-
tion, some procedures have been reported using aqueous media in an environ-
mentally friendly manner.[12,13] With a view to this concern, we become
interested in developing iodination procedures in aqueous media, and herein
we report our new, efficient, environmentally friendly procedure for the iodi-
nation of aromatic compounds, especially for aromatic amines and phenolic
derivatives using the reagent system KClO3/KI/HCl.
The test reaction was carried out on 2-naphthol (10 mmol) in aqueous
medium with potassium chlorate (3.3 mmol) and potassium iodide
(10 mmol) in the presence of hydrochloric acid (10 mmol) at 808C for 2 h
and gave 1-iodo 2-naphthol in good yield.
To prove the generality of the method, a variety of commercially
available amines and phenols were subjected to this method under similar
reaction conditions, and our results are summarized in Table 1. As
expected, all the substrates underwent iodination reactions and delivered
excellent yields of mono iodo products.
In conclusion, an effective, environmentally friendly, water-solvent
method for the iodination of amines and phenols has been reported using
potassium chlorate and potassium iodide in the presence of hydrochloric acid.
EXPERIMENTAL
Mass spectra were recorded on a GC-Mass Spec Finnigan Mat 8230MS
spectrophotometer. JEOL 270 and 400-MHz spectrophotometer were used
1
for H NMR spectral analysis, and 13C NMR spectra were measured with a
Varian Gemini 300-MHz spectrophotometer.
Table 1. Iodination of aromatics with KClO3/KI/HCl in aqueous medium
Time
(h)
Yield
c
Entry
Substrate
Phenol
Product
Iodophenola
%
1
2
1
95
93
88
90
81
86
74
86
91
94
4-Chlorophenol
2-Nitrophenol
2-Naphthol
1.5
1.5
2
4-Chloro 2-iodophenol
4-Iodo 2-nitrophenol
1-Iodo 2-naphthol
Iodoanilineb
3
4
5
Aniline
2
6
4-Nitro aniline
Salicylic acid
N-phenylacetamide
4-Chloroaniline
2-Aminonaphthalene
2.5
2.5
2.5
2.5
2
2-Iodo 4-nitroaniline
2-Hydroxy-5-iodobenzoic acid
N-(4-Iodophenyl)acetamide
4-Chloro 2-iodoaniline
2-Amino-1-iodonaphthalene
7
8
9
10
aPara: ortho ratio is 95 : 5 by GC analysis.
bPara: ortho ratio is 90 : 10 by GC analysis.
cAll the compounds showed satisfactory spectroscopic data.

Mono Iodination of Aromatic Amines and Phenols
General Procedure
1917
A solution of 2-naphthol (1.44 g, 10 mmol), potassium chlorate (0.403 g,
3.33 mmol), and potassium iodide (1.66 g, 10 mmol) was prepared in
methanol (5 mL) and water (45 mL). To this mixture, hydrochloric acid
(10 mmol) was added at 808C. After completion of the reaction (measured
by TLC monitoring), the reaction mixture was extracted with diethyl ether
(40 mL). The ether extract was washed with 5% aqueous sodium thiosulphate
and water and dried over anhydrous Na2SO4. Removal of the solvent gave a
residue, which was purified on silica gel using hexane as eluent to afford
1-iodo 2-naphthol (2.43 g, 90%), mp 928C (lit. 928C). Mass: m/e ¼ 270.
1H NMR (CDCl3): d 7.98 (d, 1H, J ¼ 9 Hz, 8-H), 7.75 (overlapping
doublets, 2H, 4-H and 5-H), 7.58 (t, 1 H, J ¼ 8 Hz, 7-H), 7.35 (t, 1 H,
J ¼ 8 Hz, 6-H), 7.22 (d, 1 H, J ¼ 8 Hz, 3-H); 13C NMR (CDCl3): d 154.8,
135.6, 131.8, 130.7, 130.5, 126.95, 126.9, 125.0, 117.2, 86.8.
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