A convenient and improved synthesis of dithieno[3,2-b:2′,3′-d]thiophene

Article abstract of DOI:10.1016/S0040-4039(02)00006-0

An improved synthesis of dithieno[3,2-b:2′,3′-d]thiophene 1 is presented. By starting from 2,3-dibromothiophene 2 the total yield was improved from 35 to 58%. We also describe a more convenient synthesis of one of the reagents, benzenesulfonic acid thioanhydride 3.

Full text of DOI:10.1016/S0040-4039(02)00006-0

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 1553–1554
A convenient and improved synthesis of
dithieno[3,2-b:2%,3%-d]thiophene
Fredrik Allared, Jonas Hellberg* and Tommi Remonen†
Department of Organic Chemistry, Royal Institute of Technology, Teknikringen 56, S-100 44 Stockholm, Sweden
Received 4 December 2001; accepted 21 December 2001
Abstract—An improved synthesis of dithieno[3,2-b:2%,3%-d]thiophene 1 is presented. By starting from 2,3-dibromothiophene 2 the
total yield was improved from 35 to 58%. We also describe a more convenient synthesis of one of the reagents, benzenesulfonic
acid thioanhydride 3. © 2002 Elsevier Science Ltd. All rights reserved.
Dithieno[3,2-b:2%,3%-d]thiophene (DTT) 1 has found use
in materials for electronic and optical applications.
Optical phenomena such as two-photon absorption,1,2
electro-luminescence,3,4 photochromism,5 and two-
photon excited fluorescence6 in DTT-based materials
have been investigated. The DTT-system has attracted
interest as a building block for dimeric systems that can
be used as the active component in thin film transis-
tors.7–9 These transistors have shown interesting device
characteristics, e.g. high mobilities and large on/off
ratios. Organic acceptor and donor molecules based on
DTT have been synthesized and used for the prepara-
tion of different cation radical salts and charge-transfer
complexes.10–14 Conducting polymers based on DTT
have also been made.15,16
Our improved synthesis of 1 is depicted in Scheme 2.
Lithiation of 2,3-dibromothiophene 2 using n-butyl-
lithium followed by oxidative coupling with cupric
chloride according to the literature procedure18,19 gave,
after recrystallization from hexanes, 79% of the desired
3,3%-dibromo 2,2%-bithiophene 6. In the second step, 6
was dissolved in diethyl ether (10 ml/mmol), and cooled
to −78°C under nitrogen. After addition of 2 equiv. of
n-butyllithium and 40 min of stirring, 1 equiv. of 3 was
added, and the mixture was left to reach room temper-
ature overnight. Normal work-up and purification by
Br
S
S
c)
d)
a)
b)
One of the factors hampering further exploration of the
dithienothiophene family is the inefficiency of the
presently used synthesis.17
S
S
S
S
S
5
4
1
Scheme 1. Usual route to dithieno[3,2-b:2%,3%-d]thiophene 1.
Reagents and conditions: (a) n-BuLi, −78°C; (b) (PhSO2)2S 3,
−78°C to rt; (c) n-BuLi, −78°C; (d) CuCl2, −78°C to rt.
The old synthesis is depicted in Scheme 1. 3-Bromoth-
iophene 4 is lithiated with n-butyllithium and reacted
with benzenesulfonic acid thioanhydride 3. The result-
ing 3,3%-dithienylsulfide 5 is again treated with n-butyl-
lithium and then with cupric chloride, to yield the
desired target 1. In our hands the total yield has varied
from 10% up to 35% (which is the reported yield).
These low yields can be attributed mainly to the low-
yielding distillation of the dithienyl sulfide 5, and to an
anticipated low selectivity of the lithiation of 5 in the
second step.
Br
Br
Br
S
S
c)
d)
a)
b)
S
S
S
S
Br
6
2
1
Scheme 2. New synthesis of dithieno[3,2-b:2%,3%-d]thiophene
1. Reagents and conditions: (a) n-BuLi, −78°C; (b) CuCl2,
−78°C to rt (79%); (c) n-BuLi, −78°C; (d) (PhSO2)2S 3, −78°C
to rt (70%).
* Corresponding author. Tel.: +46-8-7908127; fax: +46-8-7912333;
e-mail: jhel@kth.se
† Present address: Acreo AB, Bredgatan 34, S-602 21 Norrko¨ping,
Sweden.
0040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)00006-0

1554
F. Allared et al. / Tetrahedron Letters 43 (2002) 1553–1554
References
chromatography or recrystallization from methanol
gave 70% yield of pure dithieno[3,2-b:2%,3%-d]thiophene.
We found that it was necessary to grind the benzene-
sulfonic acid thioanhydride 3 finely; when large crys-
tals of 3 were used, macrocyclic by-products were
formed. We had earlier observed, but not fully under-
stood, this problem in the synthesis of the tetra-
1. Kim, O.-K.; Lee, K.-S.; Woo, H. Y.; Kim, K.-S.; He, G.
S.; Swiatkiewicz, J.; Prasad, P. N. Chem. Mater. 2000, 12,
284–286.
,
2. Wang, C.-K.; Macak, P.; Luo, Y.; Agren, H. J. Chem. Phys.
2001, 9813–9820.
3. Kim, O.-K.; Woo, H. Y.; Lee, K.-S.; Kim, J. K.; Shim,
H.-K.; Kim, C. Y. Synth. Met. 2001, 121, 1607–1608.
4. Osterod, F.; Peters, L.; Kraft, A.; Sano, T.; Morrison, J.
J.; Feeder, N.; Holmes, A. B. J. Mater. Chem. 2001, 11,
1625–1633.
methylsubstituted
dithieno[3,2-b:2%,3%-d]thiophene.20
3,3%-Dibromo 2,2%-bithiophene 6 can also be obtained
by tetrabromination–debromination of 2,2%-bithio-
phene.21 This procedure can be readily scaled up.
5. Tsivgoulis, G. M.; Lehn, J.-M. Angew. Chem., Int. Ed. Engl.
1995, 34, 1119–1122.
6. Ventelon, L.; Moreaux, L.; Mertz, J.; Blanchard-Desce, M.
To further improve the synthesis and make it more
convenient, we looked at the synthesis of the ben-
zenesulfonic acid thioanhydride 3 used in the last
step. Although the published synthesis gave decent
yields of 3, the product showed varying shelf life. We
tried to replace benzene with toluene, but the higher
boiling point of toluene accelerated degradation of 3
during recrystallization. Instead we found diethyl
ether to be a suitable solvent. The benzenesulfinic
acid sodium salt dihydrate was slurried in ether and
0.5 equiv. of sulfur dichloride (twice distilled from
phosphorus trichloride) was added over 15 min. After
2 h the reaction was stopped by the addition of
water and the insoluble product was filtered off and
rinsed with water. Recrystallization from acetone gave
an 80–90% yield of 3 as large white crystals with
excellent stability in ambient atmosphere and temper-
ature.
Chem. Commun. 1999, 2055–2056.
7. Sirringhaus, H.; Friend, R.; Li, X. C.; Moratti, S. C.;
Holmes, A. B.; Feeder, N. Appl. Phys. Lett. 1997, 71,
3871–3873.
8. Li, X.-C.; Sirringhaus, H.; Garnier, F.; Holmes, A. B.;
Moratti, S. C.; Feeder, N.; Clegg, W.; Teat, S. J.; Friend,
R. H. J. Am. Chem. Soc. 1998, 120, 2206–2207.
9. Morrison, J. J.; Murray, M. M.; Li, X.-C.; Holmes, A. B.;
Morratti, S. C.; Friend, R. H.; Sirringhaus, H. Synth.
Met. 1999, 102, 987–988.
10. Hayashi, N.; Mazaki, Y.; Kobayashi, K. Chem. Lett. 1992,
1689–1692.
11. Yui, K.; Ishida, H.; Aso, Y.; Otsubo, T.; Ogura, F. Chem.
Lett. 1987, 2339–2342.
12. Yui, K.; Ishida, H.; Aso, Y.; Otsubo, T.; Ogura, F. Bull.
Chem. Soc. Jap. 1989, 62, 1547–1554.
13. Mazaki, Y.; Kobayashi, K. J. Chem. Soc., Perkin Trans.
2 1992, 761–764.
14. Bertinelli, F.;CostaBizzarri, P.;DellaCasa, C.;Marchesini,
A.; Pelizzi, G.; Zamboni, R.; Taliani, C. Mol. Cryst. Liq.
Cryst. 1984, 109, 289–302.
The main advantages of this improved synthesis are:
(a) the crystallinity of the bithiophene 6, (b) the
regioselective lithiation of the two brominated posi-
tions in 6, and (c) the improved quality of 3. All
these factors improve the yield and purity of the
product.
15. Di Marco, P.; Mastragostino, M.; Taliani, C. Mol. Cryst.
Liq. Cryst. 1985, 118, 241–244.
16. Lazzaroni, R.; Taliani, C.; Zamboni, R.; Danieli, R.;
Ostroja, P.; Porzio, W.; Bre´das, J. L. Synth. Met. 1989,
28, C515–C520.
17. De Jong, F.; Janssen, M. J. J. Org. Chem. 1971, 36,
1645–1648.
18. Dahlmann, U.; Neidlein, R. Helv. Chim. Acta 1996, 79,
755–766.
Acknowledgements
19. Gronowitz, S. Acta Chem. Scand. 1961, 15, 1393–1395.
20. Remonen, T.; Hellberg, J. Synth. Met. 1995, 70, 1137–
1138.
21. Khor, E.; Ng, S. C.; Li, H. C.; Chai, S. Heterocycles 1991,
32, 1805–1812.
Financial support from the Royal Institute of Tech-
nology, Swedish Natural Science Research Council
and the Ernst Johnson foundation is gratefully
acknowledged.