A new method for the oxybromination of aromatic compounds with copper(II)bromide and potassium dichromate

Article abstract of DOI:10.1080/104265090517262

A new and mild method for oxybromination of aromatic compounds with CuBr₂ and K₂Cr₂O₇ in HOAC is reported. Copyright Taylor & Francis Inc.

Full text of DOI:10.1080/104265090517262

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Phosphorus, Sulfur, and Silicon
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A New Method for the
Oxybromination of
Aromatic Compounds with
Copper(II)bromide and
Potassium Dichromate
a
a
Rashid Badri & Mohammad Reza Shushizadeh
a
Chemistry Department, Chamran University, Ahvaz,
Iran
Published online: 21 Dec 2010.
To cite this article: Rashid Badri & Mohammad Reza Shushizadeh (2005) A New
Method for the Oxybromination of Aromatic Compounds with Copper(II)bromide and
Potassium Dichromate, Phosphorus, Sulfur, and Silicon and the Related Elements,
180:2, 533-536, DOI: 10.1080/104265090517262
To link to this article: http://dx.doi.org/10.1080/104265090517262
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Phosphorus, Sulfur, and Silicon, 180:533–536, 2005
Copyright © Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/104265090517262
A New Method for the Oxybromination of Aromatic
Compounds with Copper(II)bromide and Potassium
Dichromate
Rashid Badri
Mohammad Reza Shushizadeh
Chamran University, Chemistry Department, Ahvaz, Iran
A new and mild method for oxybromination of aromatic compounds with CuBr
2
and K Cr O in HOAC is reported.
2
2 7
Keywords Aromatic compound; copper(II)bromide; oxybromination; potassium
dichromate
INTRODUCTION
The conversion of aromatic compounds to corresponding aromatic
halides which are usefull intermediates for preparation of organometal-
lic species is important in organic synthesis and numerous procedures
of halogenation such as bromination and chlorination of aromatic com-
pounds in the presence of a catalyst usually ferric bromide or ferric chlo-
ride and other lewis acids,1 use of halides of some transition metals,
,2
3–5
6
chlorination by Mn(OAC)3 and acetylchloride, N-bromosuccinimide
7
8
and HBF4, HBr in DMSO and a variety of other bromination meth-
ods have been repoted.9 However, many of these suffer from harsh
reaction conditions or long reaction times and extraction procedures.
–12
Recently the use of oxidants such as oxone1 and sodium bismutate
3
14
with metal halides have been used as alternatives for halogenation of
aromatic compounds. In this paper we wish to report a simple and con-
venient procedure for the conversion of aromatic compounds to their
corresponding bromides with potassium dichromate as an oxidant and
CuBr2 as bromide source.
Received July 20, 2004; in final form December 16, 2004.
We thank Chamran University for financial support of this work.
Address correspondence to Rashid Badri, Chamran University, Chemistry Depart-
ment, Ahvaz, Iran. E-mail: rashidbadri@yahoo.com
533

5
34
R. Badri and M. R. Shushizadeh
2
TABLE I Oxybromination of Aromatic Compounds with CuBr and
K
2
Cr
2
O
7
in HOAC
Entry
Substrate
Product
Bromobenzene
p-Bromotoluene
2-Bromo-1,4-dimethyl benzene
4-Bromo-1,3-dimethyl benzene
p-Bromo anisol
2,4,6-Tribromo phenol
p-Bromo acetanilide
2,4,6-Tribromo aniline
—
Time (h)
yielda (%)
1
2
3
4
5
6
7
8
9
Benzene
Toluene
p-Xylene
m-Xylene
Anisol
Phenol
Acetanilide
Aniline
Benzaldehyde
Benzoic acid
Nitrobenzene
Cyanobenzene
2-Naphthol
2-Naphthyl amine
Naphthalene
Anthracene
Phenanthrene
15
7
8
5
0.5
1
0.5
0.5
24
24
24
24
0.5
0.5
1.5
1
65
87
70
65
85
90
70
85
—
—
—
—
80
85
88
90
92
1
1
1
1
1
1
1
1
0
1
2
1
2
3
4
5
—
—
—
1-Bromo-2-naphthol
1-Bromo-2-naphthyl amine
1-Bromo naphthalene
9-Bropmo anthracene
9-Bromo phenanthrene
1
(
a)
Yields refer to pure isolated products. Products were characterized by comparison
1
of their physical data, IR and HNMR spectra with these of known samples.
RESULTS AND DISCUSSION
When various aromatic substrates were treated with CuBr2 and slight
excess of potassium dichromate in acetic acid at ambient temperature,
the corresponding aromatic bromides were obtained in good to excellent
yields. Work up was conventional and involved dilution of the reaction
mixture with dichloromethane, neutralization with sodium bicarbon-
ate solution, and filtration and evaporation of the solvent.The results
obtained are summerized in Table I.
The plausible mechanism might be as outlined in Scheme 1.4
CuBr2
K2Cr2O7 + CuBr → Br2 −−−→ + Br-Br . . . Cu Br2
δ
+
−δ
ArH + Br2 → ArBr + HBr
HBr + CuBr2 → HCuBr3
SCHEME 1
Results in Table I indicate that benzene and its substituted deriva-
tives carring electron-donating groups were converted to the corre-
sponding bromides in moderate to excellent yields (Entries 1–8). Fur-
ther bromination to di-and tribromo compounds was not obsered except

Oxybromination
535
for high reactive aromatic compounds such as phenols and anilines (En-
tries 6, 8). Substituted derivatives with electron-withdrawing groups ei-
ther remained intact or gave very poor yields under the same reaction
conditions (Entries 11, 12 ). Bromination of polycyclic aromatic com-
pounds such as naphthalene, anthracene, and phenanthrene were also
examined. The reaction of these reactive aromatic moleculs proceeded
efficiently and produced bromo compounds in good yields (Entries 13–
15). It is noteworthy that the same procedure were carried out with
other metal halides such as: ZnCl2, KCl, NaCl, AlCl3, CaCl2, FeCl3 and
MgCl2, but only with CuBr2 the reaction afforded high yields.
CONCLUSION
It is evident from the results presented in Table I that our procedure for
bromination of aromatic compounds is a mild, convenient, and versatile
method and is broadly applicable for the conversion of aromatic com-
pounds into their bromoderivatives.
EXPERIMENTAL
Products were characterized by comparison of their physical data,
1
HNMR and IR spectra with those of authentic samples. The purity
of products and reaction monitoring were accomplished by thin layer
chromatography (TLC) on silica gel polygram SILG/uv 254 plates. All
the reagents and solvents used were of AR grade.
GENERAL PROCEDURE
A solution of substrate (5 mmol), copper(II) bromide (5 mmol) and potas-
sium dichromate (5.5 mmol) in glacial acetic acid (5 mmol) in a 100 ml
round-bottomed flask equipped with a magnetic stirrer was prepared.
The reaction mixture was allowed to stirr at ambient temprature for
an approperiate time (Table I). The progress of the rection was moni-
tored by TLC (eluent hexane/ethyl acetate, 10/1). After completion of
the reaction, dichloromethane (50 mL) was added to the mixture and
the reaction mixture was filtered. The filtrate was washed with water
(
50 mL × 2) and then with sodium carbonate solution (50 mL × 2). The
organic layer after separation was dried over anhydrous sodium sulfate
and filtered. The solvent was evaporated. The resulting crude material
was purified on a silica gel plate with appropriate solvent. Pure bromo
compounds were obtained in 65–95% yields (Table I).

5
36
R. Badri and M. R. Shushizadeh
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