Ceric ammonium nitrate as the novel oxidizing agent for the facile synthesis of (dichloroiodo)arenes

Article abstract of DOI:10.1080/00397911.2011.573172

Ceric ammonium nitrate (CAN) has been found to be a remarkable oxidizing agent for the oxidative conversion of iodoarenes to (dichloroiodo)arenes in acetic acid using aqueous HCl. The reaction of CAN with HCl generates in situ molecular chlorine, which is responsible for the oxidation. This method avoids the use of hazardous, toxic, and corrosive gaseous chlorine.

Full text of DOI:10.1080/00397911.2011.573172

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Ceric Ammonium Nitrate as the Novel
Oxidizing Agent for the Facile Synthesis
of (Dichloroiodo)arenes
Nilesh P. Tale a , Amol V. Shelke a & Nandkishor N. Karade a
a Department of Chemistry, Rashtrasant Tukadoji Maharaj Nagpur
University, Nagpur, Maharashtra, India
Available online: 02 Jan 2012
To cite this article: Nilesh P. Tale, Amol V. Shelke & Nandkishor N. Karade (2012): Ceric Ammonium
Nitrate as the Novel Oxidizing Agent for the Facile Synthesis of (Dichloroiodo)arenes, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
42:20, 2959-2965
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Synthetic Communications1, 42: 2959–2965, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.573172
CERIC AMMONIUM NITRATE AS THE NOVEL
OXIDIZING AGENT FOR THE FACILE SYNTHESIS OF
(DICHLOROIODO)ARENES
Nilesh P. Tale, Amol V. Shelke, and Nandkishor N. Karade
Department of Chemistry, Rashtrasant Tukadoji Maharaj Nagpur
University, Nagpur, Maharashtra, India
GRAPHICAL ABSTRACT
Abstract Ceric ammonium nitrate (CAN) has been found to be a remarkable oxidizing
agent for the oxidative conversion of iodoarenes to (dichloroiodo)arenes in acetic acid using
aqueous HCl. The reaction of CAN with HCl generates in situ molecular chlorine, which is
responsible for the oxidation. This method avoids the use of hazardous, toxic, and corrosive
gaseous chlorine.
Keywords Ceric ammonium nitrate; chlorination; (dichloroiodo)arenes; HCl; hyper-
valent iodine; iodoarenes; oxidation
INTRODUCTION
(Dichloroiodo)arenes have found broad synthetic applications as reagents for
chlorination and oxidation of various organic substrates.[1] For example, 4-amino-3-
chlroacetophenone, a common intermediate in the synthesis of cyclooxygenase-II
selective inhibitors, was synthesized via regioselective monochlorination of 4-ami-
noacetophenone on a 24.8-kg scale using PhICl2 in 87% yield.[2] (Dichloroiodo)
arenes have a practical advantage over gaseous elemental chlorine because of their
safe handling and operational simplicity. Thus, ArICl2 can be weighed accurately
for chlorination reaction.[3] Moreover, ArICl2 can be readily converted to other
important hypervalent iodine reagents, namely, iodosylbenzene, iodylarenes, (diacy-
loxyiodo)arenes, (difluoroiodo)arenes, or diaryliodonium salts.[4]
Received February 14, 2011.
Address correspondence to Nandkishor N. Karade, Department of Chemistry, Rashtrasant
Tukadoji Maharaj Nagpur University, Nagpur, Maharashtra 440033, India. E-mail: nnkarade@
gmail.com
2959

2960
N. P. TALE, A. V. SHELKE, AND N. N. KARADE
Scheme 1. Willgerodt synthesis of (dichloroiodo)arenes.
The first synthesis of (dichloroiodo)benzene, PhICl2, was reported by
Willgerodt in 1885 by the reaction of iodobenzene with ICl3.[5] Alternatively, an
improved and high-yielding procedure for the preparation of ArICl2 was again
reported by Willgerodt in 1886 by passing the stream of Cl2 through solutions of
ArI dissolved in CHCl3 at 0 ꢀC (Scheme 1).[6]
This strategy of passing chlorine gas to the respective iodoarenes has been also
explored in the synthesis of recyclable chlorinating agents such as 4,40-bis(dichloro-
iodo)biphenyl, 3-(dichloroiodo)benzoic acid,[7] and polymer-supported[8] and flurous[9]
(dichloroiodo)arenes. To circumvent the use of hazardous, toxic, and corrosive gaseous
chlorine used in these methods, an environmentally benign oxidative halogenation
process for in situ generation of molecular chlorine from the oxidation of chloride
with suitable oxidant under monophasic and biphasic reaction conditions has been
developed.[10] Various oxidizing agents such as activated KMnO4,[11] MnO2,[11]
CrO3,[12] concentrated HNO3,[13] Na2S2O8,[14] KClO3,[15] NaClO2, and NaClO[16] have
been reported for the synthesis of (dichloroiodo)arenes using hydrochloric acid either
as a separate phase or cosolvent. Alternatively, the hydrogen peroxide[17] and its deri-
vatives such as sodium perborate (NaBO3 H2O),[13] sodium percarbonate (Na2CO3
1.5H2O2),[18] and urea hydrogen peroxide (UHP)[19] can be also used for the synthesis
of (dichloroiodo)arenes. Some of these reported methods for the synthesis of (dichlor-
oiodo)arenes involve excess use of oxidant, strong reaction conditions, longer reaction
time, and difficult isolation of the products. Thus, the development of alternative and
more efficient strategies using a novel oxidizing agent for the synthesis of (dichloroio-
do)arenes is of considerable relevance.
RESULTS AND DISCUSSION
Ceric ammonium nitrate (CAN) is a well-known single-electron oxidant used
for various organic transformations.[20] There are number of reports of bromination
and iodination reactions mediated by CAN.[21] Its applications for the chlorination
reaction as well as its utility for the preparation of hypervalent iodine reagents are
hitherto unknown. In continuation of our work on hypervalent iodine reagents,[22]
herein we report a facile and straightforward method for the preparation of (dichlor-
oiodo)arenes from iodoarenes in dilute hydrochloric acid solution using CAN as an
oxidant and acetic acid as cosolvent (Scheme 2). The reaction of CAN with aqueous
hydrochloric acid generates in situ molecular chlorine, responsible for the oxidative
conversion of iodoarenes to (dichloroiodo)arenes. This method avoids the use of gas-
eous chlorine and is relatively safe and inexpensive.
The optimum reaction conditions were investigated using the reaction of iodo-
benzene with various chlorides (LiCl, NaCl, and HCl) and CAN as the oxidant. The

SYNTHESIS OF (DICHLOROIODO)ARENES
2961
Scheme 2. Synthesis of (dichloroiodo)arenes using CAN.
combination of LiCl or NaCl with CAN in acetic acid or CCl4 resulted in poor yield
for the oxidative conversion of iodobenzene to PhICl2. When CAN (10 mmol) was
added to a stirred solution of iodobenzene (5 mmol) and aqueous HCl [made by mix-
ing concentrated HCl (10 mL) and H2O (20 mL)] in acetic acid, the resulting orange
solution gradually turned dark yellow with the clean precipitation of product within
1 h. Filtration of the reaction mixture followed by petroleum ether wash resulted in
the formation of PhICl2 (mp 108–109 ꢀC, lit.[12a] 110–111 ꢀC) in 92% yield with 94%
HPLC purity. The absence of either water or acetic acid in the reaction mixture led
to the poor yield of PhICl2.
Having succeeded with iodobenzene, the methodology was extended to a wide
range of iodoarenes possessing electron-withdrawing and electron-donating groups.
The results are summarized in Table 1. In all the cases, the reactions were completed
in 1 h with good to excellent yields of yellow solid crystalline (dichloroiodo)arenes.
The reaction was successful for the iodoarenes with electron-withdrawing groups
such as nitro. The synthesis of recyclable chlorinating agents such as 4,40-bis(dichloro-
iodo)biphenyl and 3-(dichloroiodo)benzoic acid was also accomplished by the reac-
tion of 4, 40-diiodobiphenyl and 3-iodobenzoic acid respectively (Table 1, entries 2j
and 2n) with appropriate stoichiometric ratio of CAN and aqueous HCl. Confir-
mation for the structures of all (dichloroiodo)arenes was established by comparison
Table 1. Preparation of (dichloroiodo)arenes from iodoarenes using ceric ammonium nitrate and aqueous
HCl at room temperature
Entry
Substrate ArI 1
Product ArICl2
2
Yield (%)a
Mp (ꢀC)
Lit. mp (ꢀC)
a
b
c
d
e
f
C6H5I
C6H5ICl2
92
85
87
83
69
76
89
88
90
76
68
73
69
75
108–109
88–89
110–111[12a]
89–90[19]
2-CH3C6H4I
3-CH3C6H4I
4-CH3C6H4I
4-CH3OC6H4I
3-ClC6H4I
2-CH3C6H4ICl2
3-CH3C6H4ICl2
4-CH3C6H4ICl2
100–102
105–107
72–74
97–98[12a]
108–111[12a]
75–76[12a]
96–98[12a]
110–112[12a]
—
b
4-CH3OC6H4ICl2
3-ClC6H4ICl2
4-ClC6H4ICl2
97–98
g
h
i
4-ClC6H4I
3-BrC6H4I
108–110
129–131
121–123
159–161
92–93
3-BrC6H4ICl2
4-BrC6H4I
4-BrC6H4ICl2
123–124[15]
156–158[7]
92–94[12a]
94–95[12a]
175–176[15]
183–185[7]
j
4, 40-(C6H4I)2
2-NO2C6H4I
3-NO2C6H4I
4-NO2C6H4I
3-HO2CC6H4I
4, 40-(C6H4ICl2)2
2-NO2C6H4ICl2
3-NO2C6H4ICl2
4-NO2C6H4ICl2
3-HO2CC6H4ICl2
k
l
91–93
173–174
182–184
m
n
aIsolated yields.
bUnstable yellow solid.

2962
N. P. TALE, A. V. SHELKE, AND N. N. KARADE
1
of H NMR spectra of the corresponding iodoarenes. The melting points of all the
products (dichloroiodo)arenes, agreed well with the literature data.
Mechanistically, the reaction of CAN with aqueous HCl generates in situ
molecular chlorine, which is responsible for the oxidative conversion of iodoarenes
to (dichloroiodo)arenes. CAN was not observed to oxidize iodoarenes directly to
iodine(III) species.
CONCLUSION
In conclusion, we have developed a general and efficient method for the syn-
thesis of (dichloroiodo)arenes from iodoarenes in dilute hydrochloric acid solution
using CAN as an oxidant and acetic acid as a cosolvent (biphasic system). This
method is operationally simple because it avoids the use of toxic and corrosive
gaseous chlorine. The products, (dichloroiodo)arenes, are formed in excellent purity
with good yields in short reaction times (1 h).
EXPERIMENTAL
Representative Experimental Procedure
CAN (5.48 g, 10 mmol) was portionwise added to a stirred solution of iodoar-
enes (5 mmol) in a mixture of glacial AcOH (10 mL) and dilute HCl [made by mixing
concentrated HCl (10 mL) and H2O (20 mL)]. The progress of the reaction was fol-
lowed by thin-layer chromatography (TLC). The mixture was stirred at room
temperature for 1 h. The resulting orange solution gradually formed a yellow precipi-
tate of solid product. The yellow precipitate was collected by filtration and washed
well with ice-cold water (until the washings were colorless and neutral) and then with
petroleum ether. The resulting product, (dichloroiodo)arene was obtained in excel-
lent purity subsequently air dried in the dark. The melting points of all the products
were determined immediately to avoid any probable decomposition.
(Dichloroiodo)benzene (2a)
1H NMR (DMSO, 400 MHz): d 7.18 (t, 1H, J ¼ 7.6 Hz, ArH), 7.39 (t, 3H,
J ¼ 7.2 Hz, ArH), 7.73 (d, 1H, J ¼ 7.6 Hz, ArH). 13C NMR (CDCl3, 100 MHz): d
125.36, 131.62, 132.16, 133.87.
2-Methyl(dichloroiodo)benzene (2b)
1H NMR (CDCl3, 400 MHz): d 2.42 (s, 3H, ArCH3), 6.85–6.87 (m, 1H, ArH),
7.23 (d, 2H, J ¼ 6.8 Hz, ArH), 7.79 (d, 1H, J ¼ 8 Hz, ArH).
3-Methyl(dichloroiodo)benzene (2c)
1H NMR (CDCl3, 400 MHz): d 2.43 (s, 3H, ArCH3), 7.33–7.4 (m, 2H, ArH),
7.96–7.99 (m, 2H, ArH).

SYNTHESIS OF (DICHLOROIODO)ARENES
2963
4-Methyl(dichloroiodo)benzene (2d)
1H NMR (CDCl3, 400 MHz): d 2.46 (s, 3H, ArCH3), 7.27 (d, 2H, J ¼ 8 Hz,
ArH), 8.04 (d, 2H, J ¼ 8 Hz, ArH). 13C NMR (CDCl3, 100 MHz): d 21.45, 122.03,
132.35, 133.87, 137.23.
3-Chloro(dichloroiodo)benzene (2f)
1H NMR (CDCl3, 400 MHz): d 7.42 (t, 1H, J ¼ 8.2 Hz, ArH), 7.57 (d, 1H,
J ¼ 7.6 Hz, ArH), 8.09 (d, 1H, J ¼ 7.6 Hz, ArH), 8.19 (s, 1H, ArH).
4-Chloro(dichloroiodo)benzene (2g)
1H NMR (CDCl3, 400 MHz): d 7.45 (d, 2H, J ¼ 8.8 Hz, ArH), 8.11 (d, 2H,
J ¼ 9.2 Hz, ArH). 13C NMR (DMSO, 100 MHz): d 91.05, 130.04, 133.36, 138.23.
3-Bromo(dichloroiodo)benzene (2h)
1H NMR (CDCl3, 400 MHz): d 6.97 (t, 1H, J ¼ 8 Hz, ArH), 7.46 (d, 1H,
J ¼ 8 Hz, ArH), 7.63 (d, 1H, J ¼ 7.6 Hz, ArH), 7.87 (s, 1H, ArH).
4-Bromo(dichloroiodo)benzene (2h)
1H NMR (CDCl3, 400 MHz): d 7.61 (d, 2H, J ¼ 9.6 Hz, ArH), 8.04 (d, 2H,
J ¼ 8.4 Hz, ArH). 13C NMR (DMSO, 100 MHz): d 93.44, 123.01, 134.4, 140.03.
1, 4-Bis(dichloroiodo)benzene (2i)
1H NMR (CDCl3, 400 MHz): d 7.79 (d, 2H, J ¼ 8.8 Hz, ArH), 7.88 (d, 2H,
J ¼ 8.8 Hz, ArH).
4,4’-Bis(dichloroiodo)biphenyl (2k)
1H NMR (CDCl3, 400 MHz): d 7.27 (d, 4H, J ¼ 8 Hz, ArH), 7.76 (d, 4H,
J ¼ 8.4 Hz, ArH).
2-Nitro(dichloroiodo)benzene (2l)
1H NMR (CDCl3, 400 MHz): d 7.26 (t, 1H, J ¼ 8.8 Hz, ArH), 7.49 (t, 1H,
J ¼ 8.4 Hz, ArH), 7.86 (d, 1H, J ¼ 8 Hz, ArH), 8.03 (d, 1H, J ¼ 8 Hz, ArH). 13C
NMR (CDCl3, 100 MHz): d 86.24, 125.46, 129.07, 133.41, 141.93.
3-Nitro(dichloroiodo)benzene (2m)
1H NMR (CDCl3, 400 MHz): d 7.29 (t, 1H, J ¼ 8 Hz, ArH), 8.03 (d, 1H,
J ¼ 7.6 Hz, ArH), 8.21 (d, 1H, J ¼ 7.6 Hz, ArH), 8.57 (s, 1H, ArH).

2964
N. P. TALE, A. V. SHELKE, AND N. N. KARADE
4-Nitro(dichloroiodo)benzene (2n)
1H NMR (CDCl3, 400 MHz): d 7.90 (d, 2H, J ¼ 9.2 Hz, ArH), 7.95 (d, 2H,
J ¼ 9.2 Hz, ArH). 13C NMR (DMSO, 100 MHz): d 102.62, 124.33, 138.21, 147.14
3-(Dichloroiodo)benzoic Acid (2p)
1H NMR (CDCl3, 400 MHz): d 7.23 (t, 1H, J ¼ 8 Hz, ArH), 7.95 (d, 2H,
J ¼ 8 Hz, ArH), 8.08 (d, 2H, J ¼ 8 Hz, ArH), 8.45 (s, 1H, ArH). 13C NMR (DMSO,
100 MHz): d 94.09, 129.23, 130.4, 133.18, 138.89, 141.72, 167.26.
ACKNOWLEDGMENTS
The authors are grateful to the Department of Science and Technology, New
Delhi, India (No. SR=S1=OC-72=2009) for financial support. The authors are also
grateful to Avtar Singh, Punjab University, Chandigarh, India, for recording
NMR spectra.
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