Highly efficient halogenation of organic compounds with halides catalyzed by cerium(III) chloride heptahydrate using hydrogen peroxide as the terminal oxidant in water

Article abstract of DOI:10.1002/adsc.200900124

In this article a new environmentally friendly catalytic method is described for the efficient monoiodination and bromination of arenes and also iodoetherification and iodolactonization of olefins using hydrogen peroxide as the terminal oxidant. The method is based on using sodium iodide or sodium bromide, hydrogen peroxide (35%) and cerium(III) chloride as an effective catalyst in water at room temperature or under reflux conditions. By this protocol, iodination of anilines proceeded with high regioselectivity at the para position with the formation of small amounts of the ortho isomers. However, bromination of anilines proceeded with absolute regioselectivity to give the para isomers as the sole products in high yields. Iodinations and bromi-nations of m-xylene, toluene, chloro- and bromobenzenes were proceeded with excellent regioselectivity to produce the para isomers as the sole products. Benzene was also halogenated by this catalytic system to give the monohalogenated benzene in good yields. Iodoetherification and iodolactonization of olefins also proceeded easily in high yields at room temperature. However, the bromination of olefins by this protocol failed and the starting materials were detected intact.

Full text of DOI:10.1002/adsc.200900124

FULL PAPERS
DOI: 10.1002/adsc.200900124
Highly Efficient Halogenation of Organic Compounds with
Halides Catalyzed by Cerium(III) Chloride Heptahydrate Using
Hydrogen Peroxide as the Terminal Oxidant in Water
AHCTUNGTRENNUNG
a,
a,
a
a
Habib Firouzabadi, * Nasser Iranpoor, * Somayeh Kazemi, Arash Ghaderi,
a
and Atefeh Garzan
a
Chemistry Department, College of Sciences, Shiraz University, Shiraz 71454, Iran
Fax : (+98)-228-6009; e-mail: firouzabadi@chem.susc.ac.ir or iranpoor@chem.susc.ac.ir
Received: February 22, 2009; Revised: June 9, 2009; Published online: July 27, 2009
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200900124.
Abstract: In this article a new environmentally nations of m-xylene, toluene, chloro- and bromoben-
friendly catalytic method is described for the effi- zenes were proceeded with excellent regioselectivity
cient monoiodination and bromination of arenes and to produce the para isomers as the sole products.
also iodoetherification and iodolactonization of ole- Benzene was also halogenated by this catalytic
fins using hydrogen peroxide as the terminal oxidant. system to give the monohalogenated benzene in
The method is based on using sodium iodide or good yields. Iodoetherification and iodolactonization
sodium bromide, hydrogen peroxide (35%) and of olefins also proceeded easily in high yields at
cerium ACHTUNGTRENNUNG( III) chloride as an effective catalyst in water room temperature. However, the bromination of ole-
at room temperature or under reflux conditions. By fins by this protocol failed and the starting materials
this protocol, iodination of anilines proceeded with were detected intact.
high regioselectivity at the para position with the for-
mation of small amounts of the ortho isomers. How-
ever, bromination of anilines proceeded with abso- Keywords: aromatic compounds; bromination;
lute regioselectivity to give the para isomers as the cerium AHCUTNGRNENUG( III) chloride; hydrogen peroxide; iodination;
sole products in high yields. Iodinations and bromi- water
Introduction
creates problems, especially when large-scale opera-
tion is concerned. On the other hand, water with its
Environmentally sustainable chemical processes in- chemical and physical properties imposes selectivity
volving clean organic reactions in the absence of and reactivity in reactions conducted in aqueous
harmful organic solvents are highly encouraged from media which cannot be attained using organic sol-
[
8–10]
economical and social concerns. For these reasons, in vents.
In addition, in water, phase separation is
response, industry has started adopting green chemis- easier because most organic compounds are not solu-
try practices including waste prevention rather than ble in water and can be easily separated from the
its treatment. Disposal of organic solvents in the phar- aqueous phase.
maceutical industries is nowadays a major problem
Using water as the reaction mediunm has been a
[
1,2]
and constitutes around 80% of their wastes.
Re- topic of our interest in recent years. Along this line,
placement of expensive, toxic, flammable, not recycla- we have introduced the Michael addition of amines
[
11]
ble organic solvents with water is a challenge and in and thiols to a,ß-unsaturated ketones,
regioselec-
[
12]
great demand from academia and chemical indus- tive iodination of aromatic compounds, ring open-
[3–7]
[13]
tries.
The use of water as the reaction medium has ing of epoxides with varieties of nucleophiles, oxi-
several benefits; water is a cheap and abundant, non- dation of sulfides to their sulfoxides with H O , Mi-
[14]
2
2
toxic, non-flammable and relatively green solvent. chael addition of indoles and pyrroles to a,ß-unsatu-
[
15]
However, the heat capacity of water is not favorable rated electron-deficient compounds and the conver-
and isolation and drying of the products sometimes
Adv. Synth. Catal. 2009, 351, 1925 – 1932
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1925

Habib Firouzabadi et al.
FULL PAPERS
[
54]
sion of epoxides to thiiranes and amino alcohols in pH 6 buffer in Et O-H O,
aqueous media.
KBr/benzyltriphenyl-
2
2
[16]
[55]
phosphonium peroxodisulfate/MeCN,
Br or LiBr/
2
The aromatic halogenation reaction is an important tetrabutylammonium
peroxydisulfate/MeCN
or
[
56]
electrophilic substitution reaction and haloarenes are CH Cl
and I /poly(4-vinylpyridine)-supported per-
2
2
2
[
57]
useful synthetic intermediates in the pharmaceuticals, oxodisulfate/MeCN.
[
17,18]
pesticides and agrochemical industries.
They are
All the above-mentioned reactions proceed in or-
also useful and important substrates for various cross- ganic solvents except for one in which Ce(OH) OOH
3
[
19–22]
[12]
coupling reactions.
Halogenation of organic sub- is used in SDS micellar solution.
strates consists of using chlorine, bromine, or iodine.
Iodoetherification and iodolactonization are signifi-
However, halogenation reactions are associated with cant and fundamental transformations in organic syn-
serious environmental hazards with respect to the thesis from different points of view. These reactions
handling, transportation and storage of chlorine, bro- are also of importance for structural elucidation of or-
[
23]
[58,59]
mine and iodine. Handling halide salts is safer and ganic molecules.
Examples consist of Coreyꢁs
[
60]
easier and they can be easily oxidized to the corre- prostaglandin synthesis, total synthesis of tumor in-
sponding positive halogens or hypohalous acids by a hibitors, for example, vernolepin and vernomenin
variety of methods. One method for this purpose is and in vitamin D and D synthesis. In this study,
[61]
[
24]
[62]
2
3
to use H O as an environmentally friendly and strong we have also paid attention to the application of this
2
2
[
25]
oxidant. However, the rate of oxidation of halides catalytic system for haloetherification and halolacto-
[
26]
with H O is slow and not a practical process. At nization reactions.
2
2
lower pH, the rate enhancement for halogenation
Literature surveys show that easy, inexpensive and
occurs by the in situ generation of hypohalous acids. environmentally friendly catalytic methods for the
However, acid-sensitive functional groups do not tol- halogenation of arenes, especially those conducted in
[
27,28]
erate these reaction conditions.
water in the absence of any organic co-solvents, are
Due to the potential utility of aryl bromides in the scarce in the literature and are of interest and in
synthesis of aryl esters, arylolefins and other useful demand from different points of view.
compounds, bromination of aromatic compounds has
been the subject of numerous studies.
Now in this article we introduce a new and a novel
catalytic method using CeCl ·7H O as an efficient cat-
[
29–32]
3
2
Because of the low electrophilicity of molecular alyst for the iodination and bromination of arenes by
iodine, compared to those of molecular bromine and NaI or NaBr to their monosubstituted halides using
chlorine, the direct iodination of aromatic compounds H O (35%) as the terminal oxidant in neat water. In
2
2
with iodine is difficult. Recently, methodologies inten- addition, the syntheses of iodinated cyclic ethers and
sively developed for the preparation of iodoarenes the iodinated lactones from their corresponding unsa-
[
33]
are based on a wide range of iodinating agents such turated alcohols and carboxylic acids in the presence
[
34]
[35]
[36]
as I -Ag SO , I2-HgO, NIS in ionic liquids, ICl/ of this catalytic system in water are presented.
2
2
4
[
37]
In
MeCN,
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(OTf) in MeCN-CHCl
I /O /H PV Mo O in
2 2 5 2 10 40
[39]
3
3,
[
38]
I2/Fe
A( NO ) /H PW O in CH Cl ,
C
H
T
U
N
G
T
R
E
N
N
U
N
G
I2 or
3
3
3
12 40
40]
2
2
[
NaI/Fe
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(NO )·1.5N O /charcoal,
NIS/ZrCl4
in Results and Discussion
3
2
4
[
[
41]
42]
CH Cl ,
I2/Bi
A
C
H
T
U
N
G
T
R
N
U
G
2
2
3
3
3
3
[43]
CH Cl , I /silfen in CH Cl
and I /ortho-periodic To optimize the reaction conditions, we first studied
2
2
2
2
2,
2
acid in EtOH (95%) under microwave irradiation or the iodination of anisole as a model compound using
[
44]
by conventional heating.
Some disadvantages of the H O (35%)/NaI system in the presence of a cata-
2 2
these methods are: a) use of large amounts of the oxi- lytic amount of CeCl ·7H O in H O at room tempera-
3
2
2
dants, b) some of the oxidants are hazardous and ture. We observed that the reaction of anisole
toxic compounds, c) usually high reaction tempera- (1.0 mmol) with 1 mL of H O (35%), 1 mmol of NaI
2
2
tures and long reaction times are needed and, in addi- and 0.5 mmol of CeCl ·7 H O in 2 mL of H O pro-
3
2
2
tion, the reactions are conducted in organic solvents.
ceeded to completion within 3 h (GC analysis). Work-
However, a number of articles describing the appli- up of the reaction mixture resulted in the correspond-
cation of peroxo compounds for the oxidative iodina- ing 4-iodoanisole with excellent regioselectivity and in
tion and bromination of arenes has been recently ap- excellent isolated yield (93%).
[
12]
peared in the literature; Ce(OH) OH/SDS-H O,
Then similar reaction conditions were applied for
3
2
[
45]
[46]
NH I/oxone/MeOH,
KI/oxone/MeOH,
KI/ben- the mono-iodination of benzene, bromo- and chloro-
4
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
zyltriphenylphosphonium
peroxomonosulfate/ benzenes and activated aromatic compounds. As is
[47]
[48]
MeCN,
KI/H O
A
H
U
G
R
N
N
(30%)/H SO /MeOH,
KI or I / evident from the results indicated in the tables, iodi-
2
2
2
4
2
[
49]
PVP supported H O /H PW O in CH Cl ,
KI/(Na CO ·3 H O ),
CH Cl ,
MeCN
I2 or nation and bromination substitution reactions all pro-
2
2
3
12 40
2
2
[
50]
I /
A
H
U
T
E
N
N
(Bu N)
(S O )/MeCN,
A
H
U
G
R
N
N
(S O )/MeCN or ceeded well at room temperature with this catalytic
2
3
2
2
2
4
4
2
8
[
51]
[52]
I /
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(MePPh )
A
H
U
G
R
N
U
G
NaS O / system in water. The reaction of 1,3-dimethoxyben-
2
2
[
2
3
2
2
8
2 8
53]
and NaI/H O /organotelluride catalyst at zene was completed after 45 min to produce the
2 2
1926
asc.wiley-vch.de
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2009, 351, 1925 – 1932

Highly Efficient Halogenation of Organic Compounds with Halides
FULL PAPERS
mono-iodinated compound in 95% isolate yield. The room temperature were observed, respectively. Isola-
reaction of anisole took longer and was completed tion of iodobenzene in 60%, p-iodobromobenzene in
within 3 h to give 4-iodoanisole as the sole product of 55% and 4-iodochlorobenzene in 59% from the reac-
the reaction. Iodinations of N-methylaniline, N,N-di- tion mixtures as the sole products of the reaction indi-
methylaniline and N-ethylaniline were also completed cates the high regioselectivity of the method. The io-
in a short reaction time (30 min) and the mono-iodi- dination of acetophenone under similar reaction con-
nated para isomers were obtained in 80–82% isolated ditions failed and the stating material was isolated
yields plus their corresponding ortho isomers, which intact after 48 h. The results of this study are summar-
were isolated in 5–15% yields. The iodination of tolu- ized in Table 1. We have also studied the iodination
ene produced 4-iodotoluene in 79% isolated yield as reactions under reflux conditions in which the reac-
the sole product after 15 h together with unreacted tions proceeded faster with higher yields (Table 1).
starting material. 1,3-Dimethylbenzene also was iodi-
Iodoetherification and iodolactonization are impor-
nated within 8 h to give the mono-iodinated product tant and crucial reactions in organic synthesis and for
[
63]
in 89% isolated yield as the sole product of the reac- structural elucidation of organic molecules. Exam-
[
64]
tion.
ples include Coreyꢁs prostaglandin synthesis,
total
Iodinations of benzene, bromobenzene and chloro- syntheses of tumor inhibitors. for example, vernolepin
[
65]
benzene as less reactive arenes were also studied. and vernomenin and in vitamin D and D synthe-
Progress of the reactions was monitored by GC analy- ses.
sis whereby, after 24 h, 65, 60 and 63% conversions at
2
3
[
66]
Table 1. Monoiodination of aromatic compounds using NaI/H O catalyzed by CeCl ·7H O.
2
2
3
2
Entry
1
Substrate
Product
Time (r.t./reflux)
5 min/10 min
Conversion [%] (GC)
100/100
Isolated yield [%]
95/97
4
[a]
[a]
A
H
U
G
R
N
N
(62)
3
100/100
(53)
2
3
4
5
6
7
8
9
93/95
82/85
81/83
80/87
[
a]
[a]
A
H
U
G
E
N
N
3
100/100
[a]
[a]
A
T
N
T
E
N
G
(66)
3
100/100
[a]
[a]
A
H
N
R
N
N
(70)
3
100/100
[a]
[a]
A
H
U
G
R
N
U
G
(70)
[
[
b]
b]
[b]
8 h/3 h
95/100
85/100
89/91
[b]
15 h/4 h
24 h/6 h
24 h/12 h
79/87
[
b]
b]
[b]
65/93
60/90
60/83
[
[b]
55/86
[b]
[b]
1
1
0
1
24 h/12 h
48 h/48 h
63/90
0/30
59/83
–
[
[
a]
The data in parentheses refer to aromatic compound (1 mmol), NaI (1 mmol), CeCl ·7H O (0.1 mmol), H O (2 mL) and
3
2
2
2
H O (3 mL) under reflux conditions.
2
b]
Only para-isomers were detected and isolated
Adv. Synth. Catal. 2009, 351, 1925 – 1932
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
1927

Habib Firouzabadi et al.
FULL PAPERS
However, we have studied the reaction of iodina- of CeCl ·7H O in water also was studied. We found
3
2
tion followed by ring-closure of unsaturated alcohols the molar ratios used in iodination reactions work
and carboxylic acids by this method. For this purpose, well for bromination also. Then a broad spectrum of
the lactonization of 4-pentene-1-carboxylic acid as a aromatic compounds was subjected to the conditions
model reaction was studied. The carboxylic acid of 1 mmol of arene, 1 mL of H O , 0.5 mmol of
2
2
(
1.0 mmol) with 1 mL of H O (35%), 1.0 mmol of CeCl ·7H O in 2 mL of H O at room temperature.
2 2 3 2 2 2
NaI and 0.5 mmol of CeCl ·7 H O, in 2 mL of H O The highly regioselective bromination of activated ar-
3
2
2
proceeded to completion immediately and the desired omatic nuclei proceeded well in short reaction times
iodolactone was isolated as the sole product in 93% with excellent yields at room temperature. The bromi-
yield (Scheme 1).
nations of toluene, 1, 3-dimethylbenzene, benzene,
Then we applied these optimized conditions to un- chloro- and bromobenzenes proceeded also smoothly
saturated alcohols (Scheme 2). The reactions proceed- with high yields in longer reaction times. The results
ed well and produced the iodo-cyclic ethers in excel- of this study are presented in Table 2. By this method
lent yields within short reaction times.
bromoetherification and bromolactonization failed
The bromination of aromatic nuclei with NaBr in
the presence of H O (35%) and a catalytic amount
2
2
Scheme 1.
Scheme 2.
Table 2. Bromination of aromatic compounds using NaBr/H O catalyzed by CeCl ·7H O.
2
2
3
2
Entry
1
Substrate
Product
Time
Conversion [%] (GC)
100
Isolated yield [%]
95
3
0 min[
a]
[a]
A
H
U
G
R
N
U
G
(68)
1
h
100
(71)
2
3
4
5
6
7
8
93
92
90
[
a]
[a]
A
H
U
G
E
N
G
2
100
(76)
[a]
[a]
A
H
U
G
R
N
U
G
2 h
100
100
95
89
–
[
[
[
b]
b]
b]
3 h
87
82
81
–
4.5 h
6 h
12 h
[
[
a]
b]
The data in parentheses refer to aromatic compound (1 mmol), NaBr (1 mmol), CeCl ·7H O (0.1 mmol), H O (2 mL)
3
2
2
2
and H O (3 mL) under reflux conditions.
2
Only para-isomers were detected and isolated
1928
asc.wiley-vch.de
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2009, 351, 1925 – 1932

Highly Efficient Halogenation of Organic Compounds with Halides
FULL PAPERS
Table 3. Comparison of the results obtained for direct cata-
Table 4. Comparison of the experimental results obtained
for the mono-iodination of 1,3-dimethoxybenzene using
NaI/H O in the presence of 0.5 molar ratio of CeCl ·7H O
lytic iodination of benzene with NaI/H O /CeCl ·7H O
2
2
3
2
system and some of those using non-catalytic methods.
2
2
3
2
and other Lewis acid catalysts at room temperature.
Methods
System
Time (Tem-
perature)
Isolated
Yield
[a]
[a]
Entry
Lewis acid catalysts
CeCl ·7H O
Time [h]
Yield [%]
[%]
1
2
3
4
5
6
7
8
9
45 min
95
20
20
15
15
17
trace
trace
trace
trace
trace
3
2
Catalytic
method
H O /CeCl ·7H O 24 h (r.t.)
60
83
74
AlCl3
AlPW O
4
1
1
1
1
1
1
1
1
1
1
2
2
3
2
[72]
(cat.)
Fe(NO ) ·1.5N O / 24 h (r.t.)
charcoal
6 h (reflux)
1
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
ZnCl2
CdCl2
3
3
2
4
[
40]
[
67]
Non-catalytic Ag SO
methods using NaIO3
oxidizing re-
agents
74 h (r.t.)
4 h (r.t.)
10 h (1008C)
74
65
BF ·Et O
2
4
68]
3
2
[
CoCl2
CrCl3
CuCl2
[a]
Na WO
–
2
4
1
1
0
1
MnCl2
[
a]
Our observations.
NiCl2
[a]
Even after longer reaction times (10 h) the yield of the
product was not altered within the range of the experi-
mental error.
and the starting materials remained intact after the
appropriate reaction time.
Both iodination and bromination of arenes were
also investigated in the presence of lower amounts of
CeCl ·7H O (0.1 mmol). The results showed that the
3
2
reactions were sluggish and proceeded only for acti-
vated arenes under reflux conditions in moderate
yields. The results are shown in Table 1 (entries 1–5)
and Table 2 (entries 1–3).
In order to show the merit of this method, we have
compared our results with some other protocols using
different oxidizing agents for the direct iodination of
benzene (Table 3).
The role of cerium
alyst in organic reactions is well documented.
ACHTUNGTRNENUNG( III) chloride as a Lewis acid cat-
[
69,70,71]
However, as we have observed in this study,
CeCl ·7H O does not act as an ordinary Lewis acid
3
2
for the activation of H O . In order to show this dif-
2
2
ference, we have studied the iodination of 1, 3-dime- Scheme 3.
thoxybenzene (1 mmol) using H O (1 mmol) and NaI
2
2
(
1 mmol) in the presence of a catalytic amount of var-
ious Lewis acids (0.5 mmol) at room temperature for diately changed to a yellowish colored solution of
h. Analysis of the reaction mixtures showed the for- Ce(IV) the UV-visible spectrum of which showed a
1
mation of the mono-iodinated product from a trace to strong absorption band at 600 nm. This is very strong
a maximum of 20% plus unreacted starting materials evidence for the in situ generation of Ce(IV) species
(
Table 4, entries 2–11). The drastic rate enhancement in the mixture. Then addition of I (0.7 mmol) to this
2
and the yield of the reaction catalyzed by solution, followed by work-up with Na S O solution
2
2
4
CeCl ·7H O (Table 4, entry 1, 45 min, and 95%) in (5%) produces a colorless solution of which the UV-
3
2
comparison with other Lewis acid catalysts suggests visible spectrum did not show any absorption at
that the reactions conducted in the presence of 600 nm. This is an indication for the formation of
CeCl ·7H O should not be a simple Lewis acid cataly- Ce ACHTGNUTRNEUNG( III) in the mixture. Addition of H O to this color-
3
2
2 2
sis and there may be an electron-transfer process op- less solution, changed the color to yellow which is an
erating plus Lewis acid catalysis in these reactions. indication of the in situ generation of Ce(IV) species.
The suggested mechanism via an electron-transfer
process is shown in Scheme 3.
Therefore, to obtain more evidence in support of Conclusions
the proposed mechanism, we conducted the following
experiments. First, 0.5 mmol of CeCl ·7H O was In this article a new, novel and environmentally
3
2
added to an equivalent amount of H O (35%) in ace- friendly catalytic protocol for highly regioselective
2
2
tonitrile. The colorless solution of Ce ACHNTUGRNENUG( III) was imme- mono-iodination and bromination of arenes is report-
Adv. Synth. Catal. 2009, 351, 1925 – 1932
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
1929

Habib Firouzabadi et al.
FULL PAPERS
ed using safe NaI or NaBr, catalytic amounts of Ce- Typical Procedure for Iodoetherification of 5-
(III), and H O (35%) as the terminal oxidant in neat Hexene-1-ol with NaI/CeCl ·7H O/H O System in
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
ACHTUNGTRENNUNG
2
2
3
2
2
2
aqueous medium at room temperature and under H O at Room Temperature
2
reflux conditions. The high regioselective iodination
To a mixture of 5-hexene-1-ol (0.1 g, 1 mmol), NaI (0.149 g,
mmol) and CeCl ·7H O (0.186 g, 0.5 mmol) in water
and bromination of activated aromatic nuclei as well
as unreactive ones, in excellent yields, are regarded as
advantages of this catalytic system. Also, by this
1
3
2
(
3 mL), H O (1 mL) was added. The progress of the reac-
2 2
tion was monitored by GC or TLC. The resulting reaction
method, the immediate iodination followed by ring mixture was treated with Na S O solution (10 mol%,
2
2
4
closure of unsaturated alcohols and an unsaturated 10 mL) and extracted with diethyl ether (2ꢂ10 mL). The
carboxylic acid to the corresponding iodinated cyclic ethereal solution was dried over anhydrous Na
SO and fil-
2
4
tered. Evaporation of the solvent resulted in the desired
crude product which was further purified by plate chroma-
tography technique to give the pure compound in 95% yield
ethers and iodinated lactone were achieved in high
yields at room temperature. Comparison of the cata-
lytic activity of CeCl ·7 H O with several other Lewis
3
2
(
Scheme 2).
acids and the drastic rate enhancement and the yield
of the reaction in the presence of CeCl ·7H O sug-
3
2
Typical Procedure for Iodolactonization of 4-Penten-
gests that a simple Lewis acid catalysis is not working
in this reaction and an electron-transfer process may
be involved in the halogenation process using H O as
1
-oic Acid with NaI/CeCl ·7H O/H O System in H O
3 2 2 2 2
at Room Temperature
2
2
the terminal oxidant in the presence of this catalyst.
To a mixture of 4-penten-1-oic acid (0.1 g, 1 mmol), NaI
0.149 g, 1 mmol) and CeCl .7H O (0.186 g, 0.5 mmol) in
(
3
2
water (3 mL), H O (1 mL) was added. The progress of the
2
2
reaction was monitored by GC or TLC. The resulting reac-
tion mixture was treated with Na S O solution (10 mol%,
Experimental Section
2
2
4
1
0 mL) and extracted with diethyl ether (2ꢂ10 mL). The
Typical Procedure for Mono-Iodination of Anisole
with NaI/CeCl ·7H O/H O System in H O under
Reflux Conditions
ethereal solution was dried over anhydrous Na SO and fil-
2
4
3
2
2
2
2
tered. Evaporation of the solvent resulted in the desired
crude product which was further purified by plate chroma-
tography technique to give the pure compound in 93% yield
To a mixture of anisole (0.108 g, 1 mmol), NaI (0.149 g,
mmol) and CeCl ·7H O (0.186 g, 0.5 mmol) in water
(
Scheme 1).
1
3
2
(
3 mL), H O (1 mL) was added and the mixture was re-
2 2
fluxed for 25 min. The progress of the reaction was moni-
tored by GC or TLC. The resulting reaction mixture was Acknowledgements
treated with Na S O solution (10 mol%, 10 mL) and ex-
2
2
4
tracted with diethyl ether (2ꢂ10 mL). The ethereal solution
was dried over anhydrous Na SO and filtered. Evaporation
The authors are grateful to TWAS Chapter of Iran based at
ISMO and Shiraz University Research Council for their sup-
port.
2
4
of the solvent resulted in the desired crude product which
was further purified by a plate chromatography technique to
give the pure compound in 95% yield (Table 1, entry 2).
Then similar reaction conditions were applied for the iodi-
nation at room temperature.
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