A novel and efficient ceric ammonium nitrate catalyzed oxidative nuclear chlorination of activated aromatic compounds by acetyl chloride

Article abstract of DOI:10.1055/s-2003-36783

A mild and efficient oxidative chlorination of activated aromatic compounds have been achieved in excellent yields using acetyl chloride in the presence of a catalytic amount of ceric ammonium nitrate at room temperature. However, chlorination failed to occur with deactivated aromatic rings.

Full text of DOI:10.1055/s-2003-36783

LETTER
221
A Novel and Efficient Ceric Ammonium Nitrate Catalyzed Oxidative Nuclear
Chlorination of Activated Aromatic Compounds by Acetyl Chloride
C
S
eric
A
mmon
u
ium
N
itrate
C
b
atalyze
d
O
x
h
idative
N
ucl
a
ear
C
hlorin
s
ation Chandra Roy,* Kalyan Kumar Rana, Chandrani Guin, Biplab Banerjee
Department of Organic Chemistry Indian Association for the Cultivation of Science, Jadavpur, Calcutta - 700 032, India
E-mail: ocscr@mahendra.iacs.res.in
Received 2 December 2002
lytic amount of CAN. Acetyl chloride by itself is com-
monly used for acetylation reactions and has never been
reported to chlorinate aromatic compounds. We report
Abstract: A mild and efficient oxidative chlorination of activated
aromatic compounds have been achieved in excellent yields using
acetyl chloride in the presence of a catalytic amount of ceric ammo-
nium nitrate at room temperature. However, chlorination failed to here, for the first time, the use of a stoichiometric amount
1
5
occur with deactivated aromatic rings.
of acetyl chloride as a reagent for monochlorination of
activated aromatic nucleus in the presence of a catalytic
amount of CAN in acetonitrile (Scheme 1). Thus, a num-
ber of activated aromatic compounds were subjected to
chlorination reaction and the results are summarized in
Table 1.
Key words: ceric ammonium nitrate, nuclear chlorination, acetyl
chloride
Halogenation of aromatic systems is one of the most vast-
ly investigated organic reactions and it has been discussed
1
in a wealth of chemical literature. Aromatic chlorides
have a wide diversity of uses. They can serve as precur-
sors for numerous functionalities, such as phenols, aro-
matic ethers and thioethers, aryl amines, aryl hydrazines,
benzonitriles, benzaldehydes, fluoroaromatics, silylated
2
aromatics, and aromatic hydrocarbons. There are two
fundamental routes to prepare chloro aromatic com-
pounds. The first is through electrophilic aromatic substi-
Scheme 1
3
tution by chlorine and the other is through organometallic
The aromatic compounds shown in the Table 1 were con-
verted to their corresponding monochloro derivatives
4
intermediates (ArLi or ArMgCl).
Some of the representative chlorinating agents, which re- without any detectable dichloro compounds. Aniline and
place the traditional use of molecular chlorine in presence phenol, as expected, furnished solely acetanilide and phe-
5
of a catalyst including sulfuryl chloride, iodine trichlor- nyl acetate respectively with one equivalent of acetyl
6
7
8
ide, titanium(IV)chloride, copper(II)chloride, anti- chloride. It is noteworthy that the use of an excess (2.2
9
10
mony(V)chloride, tellurium(IV)chloride, trichloroiso- equiv) of acetyl chloride for aniline with an expectation of
1
1
12
cyanuric acid, and poly(N-chloromaleimide). Many of yielding acetylated monochloro products, furnished un-
these reagents are used either in the presence of an acid or characterizable material. Nevertheless, pure acetanilide
an oxidizing agent. However, some of the regents are un- (entry 8, Table 1) when subjected to the chlorination con-
stable and have to be prepared freshly just before their ditions, furnished solely the corresponding monochlori-
use. Recently, a new chlorinating agent, benzyltrimethyl- nated product in good yield. However, N,N-dimethyl and
ammonium tetrachloroiodate (BTMA ICl ) has been N,N-diethyl anilines, two tertiary aromatic amines, were
disclosed with its versatile applications for aromatic found to afford the corresponding monochloro-products
compounds. But this methodology is not suitable for sub- in good yields.
4
1
3
strates containing acid sensitive functionalities as it uses
The reaction did not proceed at all with deactivated aro-
acetic acid as solvent. Depending on the reaction condi-
matic compounds such as nitrobenzene, benzaldehyde,
tions many of the existing aromatic chlorination protocols
ethyl benzoate and benzoic acid. However, while all the
suffer from nuclear coupling, side chain attack in alkyl
other aromatic compounds shown in the Table 1 afforded
benzenes, disproportionation and polymerization.
solely the monochloro compounds, 1,2-methylenedioxy-
As a part of our exploration of ceric ammonium nitrate benzene afforded the symmetrical 1,2-dichloro-4,5-meth-
1
4
(
CAN) as a single electron oxidant, we have found that ylenedioxybenzene when two equivalents of acetyl
acetyl chloride acted as an efficient chlorinating agent for chloride and 10 mol% of CAN were used. It is noteworthy
activated aromatic compounds in the presence of a cata- that some of the aromatic compounds furnished the nitro
aromatics in 5–6% yields along with the monochloro
compounds. When stoichiometric amounts or excess of
CAN was used, nuclear nitration occurred solely with-
out a trace of chlorinated products.
Synlett 2003, No. 2, Print: 31 01 2003.
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S. C. Roy et al.
LETTER
Table 1 CAN Catalyzed Chlorination of Activated Aromatic Compounds by Acetyl Chloride
Entry
Substrate
Product
Yield (%)
1
2
3
4
5
6
7
8
9
Toluene
4-Chlorotoluene-2-Chlorotoluene (70:30)a
4-Chloroanisole-2-Chloroanisole (75:25)a
1-Chloro-2,5-dimethylbenzene
1-Chloro-2,4-dimethoxybenzene
1-Chloro-3,4-methylenedioxy benzene
4-Chloro-N,N- dimethyl aniline
4-Chloro-N,N- diethyl aniline
4-Chloroacetanilide
70
85
86
82
80
66
62
86
84
78
74
Anisole
p-Xylene
1,3-Dimethoxy benzene
1,2-Methylenedioxy benzene
N,N-Dimethylaniline
N,N-Diethylaniline
Acetanilide
Naphthalene
1-Chloronaphthalene
1
0
1
1-Methoxynaphthalene
2-Methoxynaphthalene
4-Chloro-1-methoxy naphthalene
1-Chloro-2-methoxy naphthalene
1
a
Ratio of the two regioisomers
In summary, we have successfully achieved a mild, effi-
cient and novel method of monochlorination of electron
rich aromatic moieties by using the cheap and commer-
cially available acetyl chloride in the presence of a cata-
lytic amount of ceric ammonium nitrate.
(10) Albeck, M.; Shaik, S. J. Chem. Soc., Perkin Trans. 1 1975,
233.
11) Juenge, E. C.; Beal, D. A.; Duncan, W. P. J. Org. Chem.
970, 35, 719.
12) Yaroslavsky, C.; Katchalski, E. Tetrahedron Lett. 1972,
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13) (a) Kajigaeshi, S.; Kakinami, T.; Ikeda, H.; Okamoto, T.
Chem. Express 1988, 3, 659. (b) Kajigaeshi, S.; Shinmasu,
Y.; Fujisaki, S.; Kakinami, T. Chem. Lett. 1989, 415.
1
(
(
(
1
5
Acknowledgment
(
c) Kajigaeshi, S.; Ueda, Y.; Fujisaki, S.; Kakinami, T. Bull.
We gratefully acknowledge financial support from the Department
of Science and Technology, New Delhi. C. G. and B. B. thank
CSIR, New Delhi for the award of the Research Fellowship.
Chem. Soc. Jpn. 1989, 62, 2096. (d) Kajigaeshi, S.;
Shinmasu, Y.; Fujisaki, S.; Kakinami, T. Bull. Chem. Soc.
Jpn. 1990, 63, 941.
(
(
14) Roy, S. C.; Guin, C.; Rana, K. K.; Maiti, G. Tetrahedron
Lett. 2001, 6941.
15) General Procedure. To a stirred mixture of the aromatic
substrate (1.5 mmol) and freshly distilled acetylchloride
References
(
1) For a general review of aromatic halogenation, see:
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reactions, Vol. III, part 2; Olah, G. A., Ed.; John Wiley and
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(1.52 mmol) in acetonitrile (10 mL), was added ceric
ammonium nitrate (0.15 mmol) in one portion under N at
2
room temperature. The reaction mixture was allowed to stir
for 7–8 h. After completion of the reaction (the progress of
the reaction was monitored by TLC), the reaction mixture
was diluted with diethyl ether (25 mL) and washed
(
(
(
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thoroughly with saturated aqueous NaHCO solution (3 × 10
3
mL), brine (3 × 10 mL) and dried (Na SO ). Volatiles were
2
4
removed under reduced pressure and the residue obtained
was purified by column chromatography over silica gel (2%
ethyl acetate in light petroleum) to yield the pure chlorinated
product.
(
(
5) De la Mare, P. B. D.; Suzuki, H. J. Chem. Soc. C 1967, 1586.
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(
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(
(
(
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Synlett 2003, No. 2, 221–222 ISSN 0936-5214 © Thieme Stuttgart · New York