An improved procedure for the preparation of 9,10-dibromoanthracene

Article abstract of DOI:10.1081/SCC-100104326

An improved procedure is described for the dibromination of anthracene, affording 9,10-dibromoanthracene with yields >95%.

Full text of DOI:10.1081/SCC-100104326

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AN IMPROVED PROCEDURE FOR THE PREPARATION OF
9,10-DIBROMOANTHRACENE
Simon Jones a & J. C. Christian Atherton a
a Department of Chemistry , University of Newcastle upon Tyne , Bedson Building,
Newcastle upon Tyne, NE1 7RU, UK
Published online: 16 Aug 2006.
To cite this article: Simon Jones & J. C. Christian Atherton (2001) AN IMPROVED PROCEDURE FOR THE PREPARATION OF
9,10-DIBROMOANTHRACENE, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 31:12, 1799-1802, DOI: 10.1081/SCC-100104326
To link to this article: http://dx.doi.org/10.1081/SCC-100104326
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SYNTHETIC COMMUNICATIONS, 31(12), 1799–1802 (2001)
AN IMPROVED PROCEDURE
FOR THE PREPARATION OF
9,10-DIBROMOANTHRACENE
Simon Jones* and J.C.Christian Atherton
Department of Chemistry, University of Newcastle upon Tyne,
Bedson Building, Newcastle upon Tyne, NE1 7RU, UK
ABSTRACT
An improved procedure is described for the dibromination of
anthracene, affording 9,10-dibromoanthracene with yields
>95%.
9,10-Dibromoanthracene has been used extensively as a component in
fluorescent and light-emitting polymers.1 In the course of some studies direc-
ted towards the synthesis of 9,10-disubstituted anthracene derivatives we
required significant quantities of 9,10-dibromoanthracene as our key start-
ing material and opted to prepare this compound ourselves by adopting a
recent procedure reported by Muathen (Scheme 1).2
Br
DBU.HBr3
AcOH
Br
Scheme 1.
* Corresponding author. E-mail: s.jones@ncl.ac.uk
1799
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

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JONES AND ATHERTON
This involved the bromination of anthracene by heating at reflux in
acetic acid with DBU.HBr3, which in turn had to be prepared from the
reaction of DBU and bromine in the presence of HBr in acetic acid.
Although this reaction proceeded well in our hands (91% yield unpurified),
it required an additional step to prepare DBU.HBr3. It occurred to us that it
may be possible to use a catalytic quantity of DBU, since the reagent
DBU.HBr3 should be easily generated in situ and then subsequently regene-
rated once electrophilic aromatic substitution had taken place (Scheme 2).
Br
AcOH
Br
DBU.HBr
Br2
DBU.HBr3
HBr ( x 2)
Scheme 2.
However, in the control reaction whereby bromine was added to a
heated solution of anthracene in acetic acid, bromination proceeded effi-
ciently giving the desired product in 97% yield. This meant that direct
bromination of the anthracene was occurring and it was subsequently
demonstrated that addition of bromine in acetic acid dropwise to a stirred
suspension of anthracene in acetic acid at room temperature gave the
desired product in 95% yield after workup (Scheme 3).
Br
i) Br2, AcOH
ii) H2O
Br
Scheme 3.
The reaction was found to be complete within 30 minutes and was
amenable to be carried out on a multi-gram scale. For example, no loss of
yield was observed when the experiment was conducted on a 1 g (94%) or on
a 10 g (94%) scale. In all cases, the 9,10-dibromoanthracene formed was
found to be of good quality and purity (mpt. 220–222ꢀC, Lit.2 226ꢀC).

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9,10-DIBROMOANTHRACENE
1801
No attempt was made to purify the material and we have subsequently used
this unpurified product in lithiation chemistry with no resulting problems.
Aside from those reactions that necessitate the synthesis of exotic
brominating agents, other methods exist in the literature for the direct
bromination of anthracene. The current Organic Syntheses preparation
of 9,10-dibromoanthracene requires heating with bromine in carbon
tetrachloride giving the desired compound in 83–88% yield,3 while Graebe
and Liebermann reported a preparation using carbon disulphide as the
reaction solvent.4 Perhaps the most efficient existing synthetic route to
9,10-dibromoanthracene involves the reaction with bromine in dry dioxane,
giving 9,10-dibromoanthracene in 99% yield.5 However, in each of these
cases there are problems associated with the toxicity, expense and inflam-
mable nature of the solvents used.
In summary we have developed an improved synthesis of 9,10-
dibromoanthracene that uses mild conditions and inexpensive, non-toxic
acetic acid as solvent.
General Procedure for the Preparation of 9,10-Dibromoanthracene
Bromine (17.9 g, 5.8 mL, 0.112 mol) in acetic acid (50 mL) was added
dropwise over a period of 5 minutes to a vigorously stirred* suspension of
anthracene (10.0 g, 0.056 mol) in acetic acid (300 mL) at room temperature
[CARE!! The reaction evolves HBr and is best connected to a HBr gas trap
(bubbler containing 1 M NaOH solution) preferably in a fumehood]. The
reaction was left to stir for 30 minutes during which a canary yellow pre-
cipitate formed. Water (300 mL) was added,** the suspension left to stir for
10 minutes, then filtered and washed with a little water. The yellow solid was
dried in vacuo for 24 hours to give the title compound (17.70 g, 94%);
mpt 220–222ꢀC (lit.2 226ꢀC); dH (200 MHz; CDCl3; Me4Si) 8.57 (4H,
AA0XX0 system, ArCH1,4,5,8), 7.62 (4H, AA0XX0 system, ArCH2,3,6,7); m/z
(EI) 333.8992 (Mþ C14H8Br2 requires 333.8993), 255 (6%), 174 (16), 168
(11), 149 (5).
*When conducting experiments on a larger scale, overhead stirring is necessary to
ensure efficient mixing.
**Addition of water was necessary to achieve complete precipitation of the
product. The optimal volume added was found to be approximately the same as
the acetic acid used.

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JONES AND ATHERTON
ACKNOWLEDGMENTS
We would like to thank the EPSRC and Thomas Swan and Co. Ltd.
for support (JCCA).
REFERENCES
1. For example see Fang, M.-C.; Watanabe, A. and Matsuda, M.
Macromolecules 1996, 29, 6807, and references therein.
2. Muathen, H.A. J. Org. Chem. 1992, 57, 2740.
3. Organic Syntheses Vol. 3, Chapman & Hall Ltd., New York, 1923,
pp. 41–43.
4. Graebe, C. and Liebermann, C. Chem. Ber. 1868, 1, 186.
5. Price, C.C. and Weaver, C. J. Am. Chem. Soc. 1939, 61, 3360.
Received in the UK July 27, 2000

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