Synthesis of acenes via coupling of 1,4-dilithiobutadienes with diiodoarenes in the presence of CuCl

Article abstract of DOI:10.1016/j.tetlet.2009.02.191

Dilithiobutadienes prepared from diiodobutadienes reacted with diiodobenzene or diiodonaphthalene to afford substituted naphthalene, anthracene, dihydronaphthacene, and dihydropentacene derivatives in the presence of CuCl and DMPU. Dihydronaphthacene and

Full text of DOI:10.1016/j.tetlet.2009.02.191

Tetrahedron Letters 50 (2009) 2722–2726
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Synthesis of acenes via coupling of 1,4-dilithiobutadienes with diiodoarenes
in the presence of CuCl
Lishan Zhou a, Kiyohiko Nakajima b, Ken-ichiro Kanno a, Tamotsu Takahashi a,
*
a Catalysis Research Center, Hokkaido University, and SORST, Japan Science and Technology Agency (JST), Sapporo 001-0021, Japan
b Department of Chemistry, Aichi University of Education, Igaya, Kariya 448-8542, Aichi, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Dilithiobutadienes prepared from diiodobutadienes reacted with diiodobenzene or diiodonaphthalene to
afford substituted naphthalene, anthracene, dihydronaphthacene, and dihydropentacene derivatives in
the presence of CuCl and DMPU. Dihydronaphthacene and dihydropentacene derivatives were converted
into the corresponding naphthacene and pentacene derivatives.
Received 28 January 2009
Revised 24 February 2009
Accepted 26 February 2009
Available online 1 March 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Linearly fused polycyclic aromatic compounds have been
attractive as organic materials, since Jackson reported that penta-
cene showed comparable or higher charge-carrier mobility than
amorphous silicon in 1997.1 Since then the area of pentacene has
been rapidly developing. Unfortunately pentacene is not soluble
in organic solvent at ambient conditions. Therefore, we proposed
that soluble substituted pentacenes were important.2a
tives as shown in Scheme 2. Diiodobutadiene derivatives were iso-
lated and purified in high yields.7 Dilithiobutadiene derivatives
were prepared in situ and they were used for the coupling with
diiodobenzene in the presence of CuCl.
Surprisingly, the corresponding naphthalene derivative 2d was
obtained in 86% GC yield. The coupling method was improved by
this method via diiodobutadiene derivatives.
Before our proposal, there were only two reports for the forma-
tion of substituted pentacenes.3,4 After that substituted acenes
have been reported,5 however the preparative method of substi-
tuted acenes is still limited.
Similarly, a t-butyl-substituted zirconacyclopentadiene did not
afford the coupling product at all with diiodobenzene in the pres-
ence of CuCl and DMPU. This reaction can also be circumvented via
isolation of diiodobutadiene and dilithiobutadiene derivatives as
shown in Scheme 3. In the presence of CuCl and DMPU, the desired
product 2g was obtained in 51% yield.
As shown above, stepwise preparation improved the situation
of trimethylsilyl- or t-Bu-substituted zirconacyclopentadienes. In
order to investigate the scope and limitation of this method, we
carried out the coupling reactions using usual alkyl- or aryl-substi-
tuted diiodobutadienes (Scheme 4). Table 1 shows the result of
various substituted diiodobutadienes including trimethylsilyl and
t-butyl cases for the reaction with 1,2-diiodobenzene.
We developed two methods for the preparation of substituted
acene derivatives. One is a homologation method using diynes or
tetraynes with transition metals stoichiometrically or catalyti-
cally.2 The other is a coupling method.6 The coupling method
involves reactions of zirconacyclopentadienes, which can be con-
veniently prepared from diynes, with diiodobenzene derivatives.
The coupling method provides a direct ring extension reaction
from diiodoaromatic compounds such as diiodobenzene and diiod-
onaphthalene. This reaction proceeded in the presence of CuCl and
DMPU. However, unfortunately trimethylsilyl-substituted zircona-
cyclopentadienes did not show any coupling reaction as shown in
Scheme 1. This prompted us to develop more general method for
the ring extension reaction from diiodobenzenes.
Alkyl-substituted diiodobutadienes (entries 1–3, and 5) gave
the corresponding naphthalenes in yields that are comparable
to those obtained from the direct coupling of zirconacyclopent-
adienes. Alkyl-substituted diiodobutadienes with bicyclic system
It has been believed that treatment of zirconacyclopentadienes
with CuCl afforded the corresponding dicopper dienes as an active
species, although the structure of such species has not been deter-
mined yet. Probably, the efficiency of the transmetalation would be
affected by substituents on the 2,5-positions of zirconacyclopent-
adienes. We carried out the stepwise preparation of such dicopper
diene species via diiodobutadiene and dilithiobutadiene deriva-
SiMe3
SiMe3
ZrCp2
SiMe3
Bu
Bu
Bu
Bu
I
I
CuCl, DMPU
THF
+
SiMe3
0%
* Corresponding author. Tel./fax: +81 11 706 9149.
E-mail address: tamotsu@cat.hokudai.ac.jp (T. Takahashi).
Scheme 1.
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.02.191

L. Zhou et al. / Tetrahedron Letters 50 (2009) 2722–2726
2723
I
SiMe3
SiMe3
SiMe3
Bu
Bu
Bu
Bu
Bu
t-BuLi
I
I
Li
Li
I
CuCl,
DMPU
THF
Bu
SiMe3
SiMe3
SiMe3
2d
1d
86% GC yield
Scheme 2.
direct coupling method
I
t-Bu
t-Bu
I
ZrCp2
CuCl, DMPU
t-Bu
t-Bu
0%
novel coupling method via dilithiobutadiene
I
t-Bu
t-Bu
t-Bu
t-BuLi
I
I
Li
Li
I
CuCl,
DMPU
t-Bu
t-Bu
t-Bu
2g
1g
51% isolated yield
Scheme 3.
I
I
R1
R1
R1
R1
R2
R2
R2
R2
R2
R2
t-BuLi
I
I
Li
Li
CuCl
DMPU
THF
R1
R1
Scheme 4.
I
I
I
R1
R1
R1
R1
R2
R2
R2
R2
R2
R2
I
I
t-BuLi
I
I
I
I
I
CuCl
DMPU
R1
R1
Scheme 5.
R3
R4
R4
I
I
R3
R3
R1
R1
R2
R2
R4
R4
R2
R2
1) 4 eq. t-BuLi
R3
I
I
2) 2 eq. CuCl
3 eq. DMPU
R1
R1
Scheme 6.
gave the products in relatively higher yields (entries 8 and 9).
Phenyl-substituted diiodobutadienes also showed the similar
reactivity (entries 6 and 10). Trimethylsilyl-substituted diiodo-
butadiene 1k afforded the coupling product, dihydronaphthacene
2k but during the work-up trimethylsilyl groups were eliminated
(entry 11).

2724
L. Zhou et al. / Tetrahedron Letters 50 (2009) 2722–2726
Table 1
Table 2
Formation of substituted acenes from diiodobutadienes and 1,2-diiodobenzenea
Formation of substituted acenes from diiodobutadienes and 1,2,4,5-tetraiodo-
benezenea
Entry
Diiodobutadiene 1
Product 2
Yieldb (%)
Entry Diiodobutadiene 1
Product 3
Isolated yield (%)
Et
Et
Et
Et
Et
Et
Et
I
I
1
56 (48)
I
I
Et
1a
2a
2b
2c
I
1
2
3
4
5
6
7
8
1a
1b
1c
3a
3b
3c
48
Et
Et
Et
Pr
Pr
I
Et
Et
Et
Et
Pr
Et
Pr
Pr
I
I
2
3
1b
78 (59)
74 (57)
Pr
Pr
I
Pr
Pr
Pr
Pr
I
I
52
53
43
55
55
47
Pr
Bu
Pr
Pr
Pr
Bu
Bu
I
Pr
Bu
I
I
1c
Bu
Bu
Bu
Bu
Bu
Bu
Bu
I
I
Bu
Bu
I
I
TMS
TMS
Bu
Bu
Bu
Bu
Bu
I
I
4
1d
2d
86 (41)
Bu
Bu
TMS
TMS
Me
TMS
Et
TMS
I
Me
Me
I
I
1l
3d
3e
3f
Et
Me
I
I
I
5
6
7
1e
2e
2f
(57)
(63)
(51)
TMS
Et
TMS
Et
Ph
Et
Et
Ph
I
I
I
1e
1f
I
I
1f
I
Et
Et
Ph
t-Bu
Ph
t-Bu
Ph
Ph
I
I
I
I
I
I
1g
2g
t-Bu
Pr
t-Bu
Ph
Ph
Pr
TMS
TMS
I
I
8
9
1h
1i
2h
2i
82 (57)
89 (61)
I
I
I
I
1m
3g
Pr
Bu
Pr
Bu
TMS
TMS
I
I
Bu
Bu
Bu
Bu
I
I
I
I
Bu
Ph
Bu
Ph
1i
3h 48
I
I
10
1j
2j
(47)
(54)
a
Ratio
and
conditions;
diiododiene
1:t-BuLi:CuCl:tetraiodoben-
Ph
Ph
H
zene:DMPU = 1.0:4.0:2.2:2.0:3.0. The coupling was carried out at 50 °C for 3–12 h.
TMS
I
I
11
1k
2k
1,2,4,5-tetraiodobenzene as shown in Scheme 5. The results are
summarized in Table 2.
TMS
H
Alkyl-substituted diiodobutadienes afforded the corresponding
diiodoarene derivatives in moderate yields (entries 1–3, 5, and
8). Trimethylsilyl-substituted diiodobutadienes also gave the prod-
ucts in yields comparable to those of alkyl substituted cases (en-
tries 4 and 7).
a
Ratio and conditions; diiododiene 1:t-BuLi:CuCl:diiodobenzene:DMPU =
1.0:4.0:2.2:2.0:3.0. The coupling was carried out at 50 °C for 3–12 h.
b
GC yields. Isolated yields are shown in parentheses.
The reaction of various dilithiobutadienes prepared from
diiodobutadienes was also applicable for the coupling with
Recently we have reported positive effects of phenyl substitu-
tion for the coupling reaction of zirconacyclopentadienes with

L. Zhou et al. / Tetrahedron Letters 50 (2009) 2722–2726
2725
Table 3
Formation of substituted acenes from diiodobutadienes and 2,3-diiodonaphthalenesa
Entry
Diiodobutadiene 1
Product 3
Product 4
Isolated yield (%)
(51)
Et
Et
Et
Et
Et
Et
I
I
Et
Et
Et
Et
I
1
1a
3a
3b
3c
4a
4b
4c
4d
I
Et
Et
Et
Et
Et
Pr
Et
Pr
Et
Et
I
I
Pr
Pr
Pr
Pr
2
3
4
1a
(56)
(53)
(57)
Et
Et
Pr
Pr
Bu
Et
Et
Bu
I
I
Bu
Bu
Bu
Bu
1a
Et
Et
Bu
Bu
Pr
Pr
Pr
Pr
Pr
Pr
Pr
I
1b
3b
3c
I
Pr
Pr
Pr
Pr
Pr
Bu
Bu
Bu
Bu
Bu
Bu
Bu
I
5
1c
4e
(54)
I
Bu
Bu
Bu
Bu
Bu
TMS
TMS
Me
Me
I
I
I
I
6
7
8
1l
3i
4f
(35)
(32)
Me
Me
TMS
TMS
TMS
TMS
Et
Et
Et
Et
I
I
1m
3a
4g
TMS
TMS
TMS
1m
3i
4h
(37)
(53)
TMS
Ph
Ph
Et
Et
Et
Et
I
I
9
1f
3a
4i
Ph
Ph
a
Ratio and conditions; diiododiene 1:t-BuLi:CuCl:diiodonaphthalene 3:DMPU = 1.0:4.0:2.2:2.0:3.0. The coupling was carried out at 50 °C for 3–12 h.
tetraiodobenzene.6e In the present method, however, such phenyl
effects were not observed (entry 6).
R
R
DDQ (1.1 equiv)
Coupling reaction with 2,3-diiodonaphthalene derivatives is
very useful since two rings can be extended at once. Scheme 6
shows the coupling of diiodonaphthalenes and the results are sum-
marized in Table 3. Alkyl-substituted diiodobutadienes gave the
corresponding anthracene derivatives (entries 1–5). Trimethyl-
silyl-substituted diiodobutadienes reacted with 2,3-diiodonaph-
toluene, 100 °C, 3 h
R
R
5i (78%)
j (48%)
2i (R = Bu)
j (R = Ph)
Scheme 7.

2726
L. Zhou et al. / Tetrahedron Letters 50 (2009) 2722–2726
1) 4 eq. t-BuLi
Pr
Pr
Pr
2) 2 eq. CuCl
3 eq. DMPU
2 eq. DDQ
I
I
3)
I
I
Pr
1h
6h (44%)
Cl
Cl
O
Pr
Pr
CN
O
γ -terpinene
Pr
CN
Pr
Scheme 8.
extended the scope of polyacenes compared with the known
method.
Acknowledgment
Authors thank Mr. Keiichi Kashima for his experimental
assistance.
Supplementary data
Supplementary data associated with this Letter can be found, in
the online version, at doi:10.1016/j.tetlet.2009.02.191.
References and notes
1. (a) Gundlach, D. J.; Lin, Y.-Y.; Jackson, T. N.; Nelson, D. F.; Nelson, S. F.; Schlom, D.
G. IEEE Electron Device Lett. 1997, 18, 87; (b) Lin, Y.-Y.; Gundlach, D. J.; Nelson, D.
F.; Jackson, T. N. IEEE Electron Device Lett. 1997, 18, 606; (c) Lin, Y.-Y.; Gundlach,
D. J.; Nelson, S. F.; Jackson, T. N. IEEE Trans. Electron Devices 1997, 44, 1325; (d)
Lin, Y.-Y.; Gundlach, D. J.; Jackson, T. N. Appl. Phys. Lett. 1998, 72, 1854; (e) Katz,
H. E. Chem. Mater. 2004, 16, 4748.
2. (a) Takahashi, T.; Kitamura, M.; Shen, B.; Nakajima, K. J. Am. Chem. Soc. 2000,
122, 12876; (b) Zhou, X.; Kitamura, M.; Shen, B.; Nakajima, K.; Takahashi, T.
Chem. Lett. 2004, 33, 410; (c) Takahashi, T.; Li, S.; Huang, W.; Kong, F.; Nakajima,
K.; Shen, B.; Ohe, T.; Kanno, K. J. Org. Chem. 2006, 71, 7967; (d) Takahashi, T.; Li,
Y.; Hu, J.; Kong, F.; Nakajima, K.; Zhou, L.; Kanno, K. Tetrahedron Lett. 2007, 48,
6726; (e) Ogasawara, M.; Sakamoto, T.; Nakajima, K.; Takahashi, T. J. Organomet.
Chem. 2007, 692, 55; (f) Li, S.; Zhou, L.; Song, Z.; Bao, F.; Kanno, K.; Takahashi, T.
Heterocycles 2007, 73, 519; g Li, S.; Li, Z.; Nakajima, K.; Kanno, K.; Takahashi, T.
Chem. Asian J. 2009, 4, 294.
3. Allen, C. F. H.; Bell, A. J. Am. Chem. Soc. 1942, 64, 1253.
4. Maulding, D. R.; Roberts, B. G. J. Org. Chem. 1969, 34, 1734.
5. For reviews, see: (a) Anthony, J. E. Chem. Rev. 2006, 106, 5028; (b) Anthony, J. E.
Angew. Chem., Int. Ed. 2008, 47, 452.
6. For coupling of zirconacyclopentadienes, see: (a) Takahashi, T.; Hara, R.;
Nishihara, Y.; Kotora, M. J. Am. Chem. Soc. 1996, 118, 5154; (b) Takahashi, T.;
Li, Y.; Stepnicka, P.; Kitamura, M.; Liu, Y.; Nakajima, K.; Kotora, M. J. Am. Chem.
Soc. 2002, 124, 576; (c) Zhou, X.; Li, Z.; Wang, H.; Kitamura, M.; Kanno, K.;
Nakajima, K.; Takahashi, T. J. Org. Chem. 2004, 69, 4559; (d) Takahashi, T.;
Kashima, K.; Li, S.; Nakajima, K.; Kanno, K. J. Am. Chem. Soc. 2007, 129, 15752; (e)
Seri, T.; Qu, H.; Zhou, L.; Kanno, K.; Takahashi, T. Chem. Asian J. 2008, 3, 388.
7. For the synthesis of 1,4-dihalo-1,3-dienes, see: (a) Negishi, E.; Cederbaum, F. E.;
Takahashi, T. Tetrahedron Lett. 1986, 27, 2829; (b) Negishi, E.; Holmes, S. J.; Tour,
J. M.; Miller, J. A.; Cederbaum, F. K.; Swanson, D. R.; Takahashi, T. J. Am. Chem.
Soc. 1989, 111, 3336; (c) Buchwald, S. L.; Nielsen, R. B. J. Am. Chem. Soc. 1989,
111, 2870; (d) Hill, J. E.; Balaich, G.; Fanwick, P. E.; Rothwell, I. P. Organometallics
1993, 12, 2911; (e) Yamaguchi, S.; Jin, R.; Tamao, K.; Sato, F. J. Org. Chem. 1998,
63, 10060; (f) Xi, C.; Kotora, M.; Takahashi, T. Tetrahedron Lett. 1999, 40, 2375;
(g) Xi, Z.; Liu, X.; Lu, J.; Bao, F.; Fan, H.; Li, Z.; Takahashi, T. J. Org. Chem. 2004, 69,
8547; (h) Xi, Z.; Song, Z.; Liu, G.; Liu, X.; Takahashi, T. J. Org. Chem. 2006, 71,
3154.
Figure 1. Structure of diphenylnaphthacene 5j.
thalene or substituted diiodonaphthalenes to give anthracene
derivatives with trimethylsilyl groups in moderate yields (entries
6–8). Phenyl-substituted one also showed the similar reactivity
(entry 9).
Compounds 2i and 2j were aromatized with DDQ at 100 °C
in toluene to afford the corresponding naphthacenes 5i and
5j, respectively (Scheme 7). The structure of naphthacene 5j
was determined by X-ray analysis. The structure is shown in
Figure 1.
Furthermore, the present method was applied for synthesis of
6,13-dipropylpentacene as shown in Scheme 8. Bicyclic diiodobut-
adiene 1h was subjected to the coupling reaction with 2,3-diiodo-
naphthalene to afford the corresponding dihydropentacene 6h,
which can be converted to 6,13-dipropylpentacene via the DDQ ad-
duct as we reported recently.6d
In summary, we have developed a general reaction for the
construction of polycyclic aromatic compounds. The 1,4-
dilithiobutadiene species were demonstrated to be more reactive
substrates for the coupling reaction. The present method