Synthesis of 5,5′-diarylated 2,2′-bithiophenes via palladium-catalyzed arylation reactions

Article abstract of DOI:10.1016/j.tet.2004.06.075

2,2′-Bithiophene and 3,3′-dicyano-2,2′-bithiophenes are diarylated directly with aryl bromides at the 5- and 5′-positions accompanied by C-H bond cleavage in the presence of Pd(OAc)₂ and a bulky phosphine ligand using Cs₂CO₃ as base. In the reaction using (2,2′-bithiophen-5-yl)diphenylmethanol as the substrate, monoarylation at the 5-position via C-C bond cleavage occurs selectively to give 5-aryl-2,2′-bithiophenes and the subsequent arylation with a different aryl bromide affords the corresponding unsymmetrically 5,5′-diarylated products.

Full text of DOI:10.1016/j.tet.2004.06.075

Tetrahedron 60 (2004) 6757–6763
Synthesis of 5,50-diarylated 2,20-bithiophenes via
palladium-catalyzed arylation reactions
*
Aya Yokooji, Tetsuya Satoh, Masahiro Miura and Masakatsu Nomura
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
Received 3 June 2004; revised 15 June 2004; accepted 15 June 2004
Abstract—2,20-Bithiophene and 3,30-dicyano-2,20-bithiophenes are diarylated directly with aryl bromides at the 5- and 50-positions
accompanied by C–H bond cleavage in the presence of Pd(OAc)2 and a bulky phosphine ligand using Cs2CO3 as base. In the reaction using
(2,20-bithi0ophen-5-yl)diphenylmethanol as the substrate, monoarylation at the 5-position via C–C bond cleavage occurs selectively to give
5-aryl-2,2 -bithiophenes and the subsequent arylation with a different aryl bromide affords the corresponding unsymmetrically 5,50-
diarylated products.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
benzylalcohols via C–C bond cleavage.6 The results are
reported herein.
Poly- and oligoaryl compounds involving a thiophene unit
have attracted much attention as the organic components of
electronic devices.1 Among the most useful methods to
prepare such arylheterocycles is the palladium-catalyzed
cross-coupling of either heteroaryl halides with arylmetals
or aryl halides with heteroarylmetals. Thus, the reaction has
been extensively studied.2
2. Results and discussion
The arylation of 2,20-bithiophene (2a) (1 mmol) was first
carried out with bromobenzene (1a) (4 mmol) in the
presence of Pd(OAc)2 (0.1 mmol) and P(biphenyl-2-yl)-
(t-Bu)2 (L1)7 (0.2 mmol) using Cs2CO3 as base in DMF at
150 8C for 48 h. As expected, 5,50-diphenyl-2,20-bithio-
phene (3) was obtained in 60% yield (Scheme 1 and entry 1
in Table 1).
Meanwhile, it is known that aryl halides can couple directly
with a number of five-membered heteroaromatics3 including
thiophenes3,4 at their 2- and/or 5-position(s) in the presence
of a palladium catalyst. The method has a significant
advantage, not requiring stoichiometric metalation of the
heterocycles. We recently reported that thiophenes5a as well
as thiazoles5b are effectively arylated with aryl bromides in
the presence of Pd(OAc)2 and a bulky phosphine ligand
using Cs2CO3 as base.
5,50-Diaryl-2,20-bithiophenes have been shown to be useful
compounds as organic semiconductors1c,d and fluorescent
materials.1e,f Consequently, we have examined t0he direct
arylation of 2,20-bithiophene as well as its 3,3 -dicyano
derivative by means of palladium catalysis. It has also bee0n
undertaken to prepare unsymmetrically 5,50-diarylated 2,2 -
bithiophenes using diphenyl(2,20-bithiophen-5-yl)diphenyl-
methanol as the strating substrate; the first step is based on
our method recently developed for preparing unsymmetrical
biaryls by the palladium-catalyzed arylation of tert-
Keywords: Arylation; Aryl halides; Palladium and compounds;
Thiophenes.
*
Corresponding author. Tel.: þ81-668797361; fax: þ81-668797362;
e-mail address: miura@chem.eng.osaka-u.ac.jp
Scheme 1.
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.06.075

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A. Yokooji et al. / Tetrahedron 60 (2004) 6757–6763
Table 1. Diarylation of 2,20-bithiophene (2a), 3,30-dicyano-2,20-bithio-
phene (2b), and 3,4-dicyanothiophene (2c) with aryl bromides 1a–fa
in the presence of Cs2CO3 in DMF, although the reaction of
2b proceeded more efficiently in DMF than in o-xylene
(entries 7 vs 8).
Entry Bromide Thiophene Conditionsb Time Product, yieldc
(h)
(%)
While the above direct method is useful for the symmetrical
diarylation, it is not successful for the monoarylation, since
a mixture of mono- and diarylated products is formed even
with a limited amount of an aryl bromide. Thus, another
strategy is required to furnish the unsymmetrical 5,50-
diarylation, especially for the initial step. We have recently
reported that the palladium-catalyzed arylation of tert-
benzylalcohols with aryl halides efficiently occurs
accompanied by C–C bond cleavage to give unsymmetrical
biaryls along with the corresponding ketones.6 In order to
see applicability of this new cross-coupling method to a
bithiophene system, we have undertaken the reaction of
(2,20-bithiophen-5-yl)diphenylmethanol (2e).
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1b
1d
1e
1e
1f
2a
2a
2a
2a
2b
2b
2b
2b
2b
2c
2c
Ad
A
B
A
B
B
48
8
48
8
4
4
1
4
4
8
18
3, 60
4, 60
5, 87
6, 91
7, 66
8, 93
9, 96
9, 87
B
Be
B
9
10
11
10, 94
11, 76
12, 62
1e
1f
Be,f
Be,f
a
The reaction was carried out in DMF under N2 unless otherwise noted.
A: [1]:[2]:[Pd(OAc)2]:[L1]:[Cs2CO3]¼2.4:1:0.1:0.2:2.4 (in mmol). B:
[1]:[2]:[Pd(OAc)2]:[L1]:[Cs2CO3]¼1.2:0.5:0.05:0.1:1.2 (in mmol). L1¼
P(biphenyl-2-yl)(t-Bu)2.
b
c
d
e
f
Isolated yield.
[1]:[2]:[Cs2CO3]¼4:1:4.
Before beginning the examination with 2e, the reaction of
diphenyl(thiophen-2-yl)methanol (2d) was carried out in
order to obtain appropriate conditions (Scheme 3 and
Table 2).
Reaction in o-xylene.
K2CO3 was used in place of Cs2CO3.
Using less volatile 1-bromo-4-tert-butylbenzene (1b)
(2.4 mmol), the same yield of the corresponding product 4
was attained after 8 h (entry 2). The symmetrically
diarylated compounds 3 and 4 are relatively less soluble,
and therefore, they were isolated by filtration through a
silica gel pad and extraction with hot toluene. Use of
2-bromo-5,6,7,8-tetrapropylnaphthalene (1c)8 as arylating
reagent afforded 5,50-bis(5,6,7,8-tetrapropylnaphthalen-2-
yl)-2,20-bithiophene (5), which was readily soluble in
ether and isolated in a higher yield (entry 3). The reaction
with 1-bromo-3-(trifluoromethyl)benzene (1d) also gave a
relatively soluble compound 6 (entry 4). While the reaction
with 4-bromoanisole (1e) proceeded, isolation of the
product in pure state was not successful due to its
insolubility.
Scheme 3.
Table 2. Arylation of diphenyl(thiophen-2-yl)methanol (2d) and 2-
arylthiophenes 13 and 14 with aryl bromides 1d and 1ea
Entry Bromide Thiophene Ligandb Solvent Time
(h)
Product,
yieldc
(%)
It has been reported that 3,30-dicyano-2,20-bithiophene (2b)
exhibits a high fluorescence quantum yield (F¼0.995),
while its molar extinction coefficient is relatively low
(log 1¼3.86).9 On the other hand, 3-cyanothiophene was
found to be readily arylated by the direct method.3c,4,5a
Thus, we next examined the diarylation of 2b. Treatment of
2b 0with 1b,d,e and 4-bromo-N,N-dimethylaniline (1f) gave
5,5 -diaryl-3,30-dicyano-2,20-bithiophenes 7–10 in good
yields (Scheme 1 and entries 5–9 in Table 1). For the
comparison of their properties, 2,5-di(4-methoxyphenyl)-
(11) and 2,5-bis[4-(dimethylamino)phenyl]-3,4-dicyano-
thiophenes (12) were also prepared by the reaction of 3,4-
dicyanothiophene (2c) with 1e and 1f (Scheme 2 and entries
10 and 11, the optical properties are described later). For the
reaction of 2c, K2CO3 and o-xylene were used as base and
solvent, respectively. The products appeared to be unstable
1d
2e
3f
4d
5e
6g
7g
1d
1d
1e
1e
1e
1e
1d
2d
2d
2d
2d
2d
13
14
L1
L2
L1
L1
L2
L1
L1
o-xylene
o-xylene
o-xylene
DMF
o-xylene
DMF
DMF
2
1
1.5
2
1
8
24
13, 62
13, 91 (71)
14, 88
14, 59
14, 88 (82)
15, 85 (64)
15, 72
a
The reaction was carried out at 150 8C under N2.
L1¼P(biphenyl-2-yl)(t-Bu)2, L2¼P(cyclohexyl)3.
b
c
d
e
f
Determined by GLC abalysis. Value in parenthesis is isolated yield.
[1]:[2]:[Pd(OAc)2]:[L]:[Cs2CO3]¼1:1:0.025:0.05:1 (in mmol).
[1]:[2]:[Pd(OAc)2]:[L]:[Cs2CO3]¼1.5:1.5:0.025:0.05:1 (in mmol).
[1]:[2]:[Pd(OAc)2]:[L]:[Cs2CO3]¼1.8:1.5:0.025:0.05:1 (in mmol).
[1]:[13 or 14]:[Pd(OAc)2]:[L]:[Cs2CO3]¼0.6:0.5:0.05:0.1:0.6 (in mmol).
g
The reactions of 2d with 1d in o-xylene using L1 and
P(cyclohexyl)3 (L2) indicated that L2 is superior than L1, as
was observed in the reaction of triphenylmethanol (entry 2
vs 1).6 In the reaction with 1e, however, the ligand effect
was not important (entries 3 and 5). The origin of this
discrepancy between 1d and 1e is not definitive at the
present stage. DMF as solvent was not effective for the
Scheme 2.

A. Yokooji et al. / Tetrahedron 60 (2004) 6757–6763
6759
reaction (entry 4 vs 3). This may be attributed to the fact that
coordination of the oxygen of the alcohol to metal center is
the key for the coupling.6
The obtained 2-arylthiophenes 13 and 14 were then treated
with 1e and 1b in DMF as for the reaction of 2a. Both the
reactions gave 2-(4-methoxyphenyl)-5-(3-trifluoromethyl-
phenyl)thiophene (15), while 13 reacted more efficiently
(entries 6 and 7 in Table 2). The electron-withdrawing group
in 13 seems to promote the deprotonation in the catalytic
cycle.4a An attempt to use 2-(2-thienyl)-2-propanol in place
of 2d was unsuccessful.
Based on the above results, alcohol 2e was reacted with
1a,d,e, 1-bromo-4-cyanobenzene (1g) and 1-bromo-
naphthalene (1h) using L2 in o-xylene (Scheme 4). As
shown in Table 3, 5-aryl-2,20-bithiophenes 16–20 were
obtained in good yields.
Scheme 5.
Table 4. Arylation of 5-aryl-2,20-bithiophenes 19 and 20 with aryl bromides
1b,e,h,ia
Entry
Bromide
Thiophene
Time (h)
Product, yieldb (%)
1
2
3
4
5
1b
1e
1h
1i
19
19
19
19
20
8
4
4
4
8
21, 57
22, 51
23, 63
24, 91
25, 53
1e
a
The reaction was carried out in DMF at 150 8C under N2. [1]:[19 or
20]:[Pd(OAc)2]:[L1]:[Cs2CO3]¼0.75:0.5:0.05:0.1:0.75 (in mmol). L1¼
P(biphenyl-2-yl)(t-Bu)2.
Scheme 4.
b
Isolated yield.
Table 3. Arylation of (2,20-bithiophen-5-yl)diphenylmethanol (2e) with
aryl bromides 1a,d,e,g,ha
maxima; such a behavior has been reported to be often
characteristic for 5,50-diaryl-2,20-bithiophene. It is wort0h
noting that the introduction of two cyano groups to the 3,3 -
positions of 5,50-di(4-tert-butylphenyl)-2,20-bithiophene (4)
increased the quantum yield0 as expected (compound 7
versus 4). 3,30-Dicyano-5,5 -di(4-methoxyphenyl)-2,20-
bithiophene (9) also showed a relatively high quantum
yield. In the case of the bis[3-(trifluoromethyl)phenyl]
derivative 8, however, it was significantly low (compound 8
versus 6). The introduction of strongly electron-donating
4-N,N-dimethylamino group allowed a remarkable red-shift
Entry
Bromide
Conditionsb
Time (h)
Product, yieldc (%)
1
2
3
4
5
6
1a
1d
1e
1e
1g
1h
A
A
A
B
B
B
1
1
2
24
1
1
16, 96 (94)
17, 75 (60)
18, 71
18, 71 (55)
19, 99 (91)
20, 76 (74)
a
The reaction was carried out in o-xylene at 150 8C under N2.
A; [1]:[2e]:[Pd(OAc)2]:[L2]:[Cs2CO3]¼0.525:0.5:0.025:0.05:0.525 (in
mmol). B; [1]:[2e]:[Pd(OAc)2]:[L2]:[Cs2CO3]¼1.575:1.5:0.025:
0.05:1.575 (in mmol). L2¼P(cyclohexyl)3.
b
Table 5. Optical absorption and emission maxima, extinction coefficient,
fluorescent quantum yield, and optical band gap of diarylated bithiophenes
3–10, 21 and 23–25 and those of diarylated thiophenes 11, 12, and 15a
c
Determined by GLC abalysis. Value in parenthesis is isolated yield.
Then, the arylation reactions of 19 with 1b,e,h and 1-bromo-
4-hexyloxybenzene (1i) and of 20 with 1e were conducted
as for that of 13 (Scheme 5 and Table 4). The
unsymmetrically disubstituted bithiophenes 21–25 could
be extracted with ethyl acetate or chloroform and were
relatively tractable.
Compound
l
abs (nm)
lem (nm)
log 1
Fb
E00 (eV)
3
4
5
6
7
8
9
10
21
23
24
25
11
12
15
373
377
399
374
394
309
407
460
396
384
400
369
348
412
338
431, 455
436, 462
462, 491
431, 455
478
429
497
565
467, 476
469, 478
491
461
436
4.54
4.51
4.72
4.57
4.35
4.12
4.39
4.44
4.63
4.59
4.63
4.53
4.38
4.59
4.49
0.17
0.16
0.29
0.17
0.33
0.01
0.42
0.12
0.12
0.21
0.12
0.18
0.08
0.04
0.32
2.98
2.94
2.78
2.98
2.73
3.22
2.64
2.33
2.80
2.84
2.80
2.92
3.13
2.70
3.25
Shown in Table 5 are the optical properties of diarylated
bithiophenes and thiophenes measured for the correspond-
ing chloroform solutions under ambient conditions.
The optical band gap E00 was estimated from the
interception of the absorption and emission spectra; the
influence of Stokes shifts was neglected.9 It can be seen that
fine-tuning of the gap of 5,50-diaryl-2,20-bithiophene
(compounds 3–10 and 21–25) is possible by substituent
effects; it is perturbed in a range of 2.33–3.22 eV. The
emission spectra of compounds 3–6, 21 and 23 showed two
488
414
a
Absorption and emission spectra were measured as a chloroform solution
(5£1025 M and 0.1 to 2.5£1026 M, respectively).
b
Determined by comparison of quinine sulfate (F¼0.546).

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A. Yokooji et al. / Tetrahedron 60 (2004) 6757–6763
(compound 10). The fluorescent efficiencies of 2,5-diaryl-
3,4-dicyanothiophenes 11 and 12 were low. While the
relation of structures of the dicyanothiophenes with the
emission properties can not be rationalized, it is remarkable
that compounds 7 and 9 having a larger torsion angle around
the C2–C20bond show relatively high emission efficiencies.
3.3.1. 5,50-Di(4-tert-butylphenyl)-2,20-bithiophene (4). In
a 100 cm3 two-necked flask was placed Cs2CO3 (2.4 mmol,
782 mg), which was then dried at 150 8C in vacuo for 2 h.
Then, Pd(OAc)2 (0.1 mmol, 22.4 mg), P(biphenyl-2-
yl)(t-Bu)2 (L1) (0.2 mmol, 40.5 mg), 1-bromo-4-tert-butyl-
benzene (1b) (2.4 mmol, 511 mg), 2,20-bithiophene (2a)
(1 mmol, 166 mg), 1-methylnaphthalene (ca. 100 mg) as
internal standard and DMF (5 cm3) were added. The
resulting mixture was stirred under N2 (balloon) at 150 8C
for 8 h. The reaction mixture was filtered through a silica gel
pad (ca. 20 g) with hot toluene. After evaporation of the
solvents, the residue was washed with hexane and
recrystallized with toluene to give compound 4 (256 mg,
60%).
In summary, we have described that 2,20-bithiophene and
3,30-dicyano-2,20-bithiophene can0 be directly and effec-
tively diarylated at the 5- and 5 -positions by means of
palladium catalysis. The diarylated 3,30-dicyano-2,20-bithio-
phenes with aryl bromides having an electron-donating
substituent0 shows relatively high fluorescent efficiency.
Using (2,2 -bithiophen-5-yl)diphenylmethanol as the sub-
strate, 5-aryl-2,20-bithiophenes can be obtained selectively
and the successive direct arylation affords unsymmetrically
5,50-diarylated products. Thus, the arylation method
accompanying C–C bond cleavage as well as that via
C–H bond cleavage we reported previously can be applied
effectively to bithiophene systems.
3.3.2. 5,50-Di(4-tert-butylphenyl)-3,30-dicyano-2,20-
bithiophene (7). In a 100 cm3 two-necked flask was placed
Cs2CO3 (1.2 mmol, 391 mg) and dried as above. Then,
Pd(OAc)2 (0.05 mmol, 11.2 mg), P(biphenyl-2-yl)(t-Bu)2
(L1) (0.1 mmol, 20.3 mg), 1-bromo-4-tert-butylbenzene
(1b) (1.2 mmol, 256 mg), 3,30-dicyano-2,20-bithiophene
(2b) (0.5 mmol, 108 mg) and DMF (5 cm3) were added.
The resulting mixture was stirred under N2 (balloon) at
150 8C for 4 h. After cooling, the reaction mixture was
extracted with ethyl acetate. Column chromatography on
silica gel using hexane–ethyl acetate (98.5:1.5, v/v) gave
compound 7 (159 mg, 66%).
3. Experimental
3.1. General
1H and 13C NMR spectra were recorded at 400 and
100 MHz, respectively. MS analysis was made by EI. GC
analysis was carried out using a Silicone OV-17 glass
column (i.d. 2.6 mm£1.5 m).
3.3.3. 5-(4-tert-Butylphenyl)-50-(4-cyanophenly)-2,20-
bithiophene (21). In a 100 cm3 two-necked flask was
placed Cs2CO3 (1.575 mmol, 513 mg) and dried as above.
Then, Pd(OAc)2 (0.025 mmol, 5.6 mg), P(cyclohexyl)3 (L2)
(0.05 mmol, 14 mg), 1-bromo-4-cyanobenzene (1g)
3.2. Preparation of thiophenes 2
(1.575 mmol,
286 mg),
diphenyl(2,20-bithiophen-5-
Bithiophene 2a was commercially available. Thiophenes
2b,10 2c11 and 2d6b were prepared according to the methods
reported previously.
yl)methanol (2e) (1.5 mmol, 522 mg), 1-methylnaphthalene
(ca. 100 mg) as internal standard and o-xylene (5 cm3) were
added. The resulting mixture was stirred under N2 (balloon)
at 150 8C for 1 h. After cooling, the reaction mixture was
extracted with ethyl acetate. After evaporation of the
solvents, the residue was washed with hexane to give
compound 19 (364 mg, 91%). Then, 19 (130 mg, 0.5 mmol)
was treated with 1-bromo-4-tert-butylbenzene (1b)
(136 mg, 0.75 mmol) in the presence of Pd(OAc)2
(0.05 mmol, 11.2 mg), P(biphenyl-2-yl)(t-Bu)2 (L1)
(0.1 mmol, 20.3 mg) and Cs2CO3 (0.75 mmol, 244 mg) in
DMF (5 cm3) under N2 at 150 8C for 8 h. Compound 21
(114 mg, 57%) was obtained by extraction with chloroform,
washing with hexane and recrystallization with toluene.
3.2.1. (2,20-Bithiophen-5-yl)diphenylmethanol (2e). In a
200 cm3 three-necked flask were added 2,20-bithiophene
(3.34 g, 20 mmol) and THF (50 cm3). Then, BuLi in hexane
(1.57 M, 13 ml) and TMEDA (3 cm3, 20 mmol) was added
with srirring at 278 8C under N2 (balloon) and allowed to
warm to room temperature. After stirring 30 min, the
mixture was cooled to 210 8C and benzophenone (3.09 g,
17 mmol) in THF (10 cm3) was added. Then, the mixture
was stirred at room temperature for 15 h, after which it was
poured into aq. NH4Cl, extracted with ethyl acetate and
dried over Na2SO4. Evaporation of the solvents and column
chromatography on silica gel using hexane–toluene (8:2,
v/v) as eluent gave compound 2e (5.74 g, 97%): Viscous oil;
1H NMR (400 MHz, CDCl3) d 2.95 (s, 1H), 6.62 (d,
J¼3.7 Hz, 1H), 6.98 (dd, J¼3.7, 5.1 Hz, 1H), 7.00 (d,
J¼3.7 Hz, 1H), 7.11 (dd, J¼1.1, 3.7 Hz, 1H), 7.18 (dd,
J¼1.1, 5.1 Hz, 1H), 7.28–7.42 (m, 10H); 13C NMR
(100 MHz, CDCl3) d 80.12, 122.94, 123.69, 124.41,
127.24, 127.48, 127.72, 127.76, 128.05, 137.27, 137.67,
146.16, 151.03; HR-MS m/z (Mþ). Calcd for C21H16OS2
348.0643. Found 348.0648.
3.4. Characterization data of products
3.4.1. 5,50-Diphenyl-2,20-bithiophene (3).12 Mp 239.5–
1
240 8C; H NMR (400 MHz, CDCl3) d 7.18 (d, J¼4.0 Hz,
2H), 7.25 (d, J¼4.0 Hz, 2H), 7.29 (t, J¼7.3 Hz, 2H), 7.39 (t,
J¼7.7 Hz, 4H), 7.61 (d, J¼7.7 Hz, 4H); 13C NMR
(100 MHz, CDCl3) d 123.80, 124.48, 125.62, 127.61,
128.96, 134.04, 136.72, 143.16; MS m/z 318 (Mþ).
3.4.2. 5,50-Di(4-tert-butylphenyl)-2,20-bithiophene (4).
1
3.3. Synthesis of 5,50-diaryl-2,20-bithiophenes
Mp 282–283 8C; H NMR (400 MHz, CDCl3) d 1.35 (s,
18H), 7.15 (d, J¼3.8 Hz, 2H), 7.20 (d, J¼3.8 Hz, 2H), 7.41
(d, J¼8.6 Hz, 4H), 7.54 (d, J¼8.6 Hz, 4H); 13C NMR
(100 MHz, CDCl3) d 31.26, 34.63, 123.35, 124.30, 125.35,
The following experimental procedures may be regarded as
typical in methodology and scale.

A. Yokooji et al. / Tetrahedron 60 (2004) 6757–6763
6761
125.86, 131.31, 136.37, 143.10, 150.76; HR-MS m/z (Mþ).
Calcd for C28H30S2 430.1780. Found 430.1789.
113.43, 114.96, 122.31, 129.11, 152.40, 161.65; HR-MS
m/z (Mþ). Calcd for C20H14N2O2S 346.0776. Found
346.0774.
3.4.3. 5,50-Bis(5,6,7,8-tetrapropylnaphtalen-2-yl)-2,20-
bithiophene (5). Mp 169–171 8C; 1H NMR (400 MHz,
CDCl3) d 1.01–1.20 (m, 24H), 1.57–1.78 (m, 16H), 2.72–
2.77 (m, 8H), 2.99–3.08 (m, 8H), 7.24 (d, J¼3.6 Hz, 2H),
7.33 (d, J¼3.6 Hz, 2H), 7.66 (d, J¼8.7 Hz, 2H), 8.00 (d,
J¼8.7 Hz, 2H), 8.20 (s, 2H); 13C NMR (100 MHz, CDCl3) d
14.9, 15.1, 15.1, 24.6, 24.7, 24.9, 24.9, 31.2, 31.2, 32.6,
32.7, 121.1, 122.5, 123.7, 124.6, 125.3, 129.9, 130.6, 131.3,
134.3, 134.4, 136.6, 137.4, 137.8, 144.2; MS m/z 754 (Mþ).
Anal. Calcd for C52H66S2: C, 82.70; H, 8.81; S, 8.49. Found
C, 82.44; H, 8.69; S, 8.60.
3.4.10. 2,5-Bis[4-(N,N-dimethylamino)phenyl]-3,4-di-
cyanothiophene (12). Mp 228.5–230 8C; 1H NMR
(400 MHz, DMSO-d6) d 3.01 (s, 12H), 6.85 (d, J¼8.8 Hz,
4H), 7.65 (d, J¼8.8 Hz, 4H); 13C NMR (100 MHz, DMSO-
d6) d 39.82, 103.31, 112.26, 114.45, 116.51, 128.35, 151.79,
152.09; HR-MS m/z (Mþ). Calcd for C22H20N4S 372.1409.
Found 372.1415.
3.4.11. 2-(3-Trifluoromethylphenyl)thiophene (13). Oil;
1H NMR (400 MHz, CDCl3) d 7.09 (dd, J¼3.5, 5.1 Hz 1H),
7.33 (dd, J¼1.1, 5.1 Hz, 1H), 7.35 (dd, J¼1.1, 3.5 Hz, 1H),
7.45–7.53 (m, 2H), 7.76 (d, J¼8.0 Hz, 1H), 7.83 (s, 1H);
13C NMR (100 MHz, CDCl3) d 122.55 (d, J¼3.7 Hz),
123.94 (q, J¼3.7 Hz), 124.11, 125.82, 127.30 (q, J¼
297 Hz), 128.23, 129.07, 129.37, 131.34 (q, J¼32.2 Hz),
135.20, 142.64; HR-MS m/z (Mþ). Calcd for C11H7F3S
228.0221. Found 228.0235.
3.4.4. 5,50-Di(3-trifluoromethylphenyl)-2,20-bithiophene
1
(6). Mp 125–126 8C; H NMR (400 MHz, CDCl3) d 7.22
(d, J¼4.0 Hz, 2H), 7.31 (d, J¼4.0 Hz, 2H), 7.49–7.55 (m,
4H), 7.55–7.77 (m, 2H), 7.83 (s, 2H); 13C NMR (100 MHz,
CDCl3) d 122.24 (q, J¼3.7 Hz), 124.31 (q, J¼3.7 Hz),
124.91, 124.93, 126.65 (q, J¼273 Hz), 128.70,
129.50, 131.49 (q, J¼32.2 Hz), 134.72, 137.37, 141.59;
HR-MS m/z (Mþ). Calcd for C22H12F6S2 454.0285. Found
454.0293.
3.4.12. 2-(4-Methoxyphenyl)thiophene (14).13 Mp 106–
107 8C; 1H NMR (400 MHz, CDCl3) d 3.83 (s, 3H), 6.90–
6.93 (m, 2H), 7.05 (dd, J¼3.6, 5.1 Hz, 1H), 7.19 (dd, J¼1.5,
3.6 Hz, 1H), 7.21 (dd, J¼1.5, 5.1 Hz, 1H), 7.51–7.55 (m,
2H); 13C NMR (100 MHz, CDCl3) d 55.34, 114.27, 122.07,
123.81, 127.22, 127.31, 127.89, 144.33, 159.18; MS m/z 190
(Mþ).
3.4.5. 5,50-Di(4-tert-butylphenyl)-3,30-dicyano-2,20-
1
bithiophene (7). Mp 275–276.5 8C; H NMR (400 MHz,
CDCl3) d 1.36 (s, 18H), 7.44 (s, 2H), 7.47 (d, J¼8.6 Hz,
4H), 7.55 (d, J¼8.6 Hz, 4H); 13C NMR (100 MHz, CDCl3)
d 31.17, 34.85, 109.78, 114.86, 124.92, 126.01, 126.31,
128.71, 139.40, 147.01, 153.04; HR-MS m/z (Mþ). Calcd
for C30H28N2S2 480.1694. Found 480.1697.
3.4.13. 2-(4-Methoxyphenyl)-5-(3-trifluoromethyl-
phenyl)thiophene (15). Mp 103.5–105 8C; 1H NMR
(400 MHz, CDCl3) d 3.85 (s, 3H), 6.94 (d, J¼8.7 Hz, 2H),
7.20 (d, J¼3.8 Hz, 1H), 7.33 (d, J¼3.8 Hz, 1H), 7.47–7.55
(m, 2H), 7.57 (d, J¼8.7 Hz, 2H), 7.76–7.78 (m, 1H), 7.84
(s, 1H); 13C NMR (100 MHz, CDCl3) d 55.39, 114.39,
122.09 (q, J¼3.8 Hz), 123.09, 123.71 (q, J¼3.8 Hz), 124.02
(q, J¼272 Hz), 124.97, 126.82, 127.03, 128.56, 129.38,
131.43 (q, J¼32.7 Hz), 135.22, 140.62, 144.80, 159.51; MS
m/z 334 (Mþ). Anal. Calcd for C18H13F3OS: C, 64.66; H,
3.92; F, 17.05; S, 9.59. Found C, 64.36; H, 3.70; F, 17.34; S,
9.70.
3.4.6. 5,50-Di(3-trifluoromethylphenyl)-3,30-dicyano-2,20-
bithiophene (8). Mp .300 8C; 1H NMR (400 MHz, CDCl3)
d 7.58 (s, 2H), 7.62 (t, J¼7.7 Hz, 2H), 7.69 (d, J¼7.7 Hz,
2H), 7.81 (d, J¼7.7 Hz, 2H), 7.86 (s, 2H); 13C NMR
(100 MHz, DMF-d7)
d 116.55, 119.99, 128.43 (q,
J¼4.6 Hz), 129.85 (q, J¼272 Hz), 131.76 (q, J¼3.7 Hz),
134.13, 135.82, 136.46, 136.55 (q, J¼32.2 Hz), 138.22,
145.41, 150.78; HR-MS m/z (Mþ). Calcd for C24H10F6N2S2
504.0190. Found 504.0192.
3.4.7. 5,50-Di(4-methoxyphenyl)-3,30-dicyano-2,20-bithio-
phene (9). Mp 266–267.5 8C; 1H NMR (400 MHz, DMSO-
d6) d 3.82 (s, 6H), 7.06 (d, J¼8.8 Hz, 4H), 7.71 (d,
J¼8.8 Hz, 4H), 7.99 (s, 2H); 13C NMR (100 MHz, DMSO-
d6) d 55.57, 109.91, 114.75, 115.05, 123.76, 125.45, 127.65,
137.86, 146.52, 160.51; HR-MS m/z (Mþ). Calcd for
C24H16N2O2S2 428.0653. Found 428.0650.
3.4.14. 5-Phenyl-2,20-bithiophene (16).14 Mp 120–121 8C;
1H NMR (400 MHz, CDCl3) d 7.03 (dd, J¼3.6, 5.1 Hz, 1H),
7.15 (d, J¼3.8 Hz, 1H), 7.20 (dd, J¼1.1, 3.6 Hz, 1H), 7.22
(dd, J¼1.1, 5.1 Hz, 1H), 7.22 (d, J¼3.8 Hz, 1H), 7.27–7.31
(m, 1H), 7.36–7.41 (m, 2H), 7.58–7.62 (m, 2H); 13C NMR
(100 MHz, CDCl3) d 123.62, 123.70, 124.37, 124.59,
125.61, 127.57, 127.85, 128.93, 134.06, 136.71, 137.43,
143.12; MS m/z 242 (Mþ).
3.4.8. 5,50-Bis[4-(N,N-dimethylamino)phenyl]-3,30-
dicyano-2,20-bithiophene (10). Mp .300 8C; 1H NMR
(400 MHz, CDCl3) d 3.03 (s, 12H), 6.72 (d, J¼8.9 Hz, 4H),
7.26 (s, 2H), 7.47 (d, J¼8.9 Hz, 4H); 13C NMR (100 MHz,
CDCl3) d 40.23, 109.09, 112.24, 115.33, 119.42, 122.64,
127.18, 137.98, 147.49, 151.00; HR-MS m/z (Mþ). Calcd
for C26H22N4S2 454.1286. Found 454.1284.
3.4.15. 5-(3-Trifluoromethylphenyl)-2,20-bithiophene
(17). Mp 102–103 8C; 1H NMR (400 MHz, CDCl3) d
7.04 (dd, J¼3.7, 5.1 Hz 1H), 7.17 (d, J¼4.0 Hz, 1H), 7.23
(dd, J¼1.1, 3.7 Hz, 1H), 7.25 (dd, J¼1.1, 5.1 Hz, 1H), 7.29
(d, J¼4.0 Hz, 1H), 7.47–7.54 (m, 2H), 7.74–7.77 (m, 1H),
7.83 (s, 1H); 13C NMR (100 MHz, CDCl3) d 122.19 (q,
J¼4.6 Hz), 123.96 (q, J¼272 Hz), 124.00 (q, J¼4.6 Hz),
124.02, 124.69, 124.77, 124.81, 127.94, 128.66, 129.45,
131.43 (q, J¼32.2 Hz), 134.86, 136.99, 137.87, 141.12;
HR-MS m/z (Mþ). Calcd for C15H9F3S2 310.0098. Found
310.0095.
3.4.9. 2,5-Di(4-methoxyphenyl)-3,4-dicyanothiophene
1
(11). Mp 225.5–227.5 8C; H NMR (400 MHz, CDCl3) d
3.88 (s, 6H), 7.02 (d, J¼8.8 Hz, 4H), 7.67 (d, J¼8.8 Hz,
4H); 13C NMR (100 MHz, CDCl3) d 55.53, 106.87,

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A. Yokooji et al. / Tetrahedron 60 (2004) 6757–6763
3.4.16. 5-(4-Methoxyphenyl)-2,20-bithiophene (18). Mp
150–151 8C; H NMR (400 MHz, CDCl3) d 3.84 (s, 3H),
3.4.22. 5-(4-Cyanophenyl)-50-(4-hexyloxyphenyl)-2,20-
bithiophene (24). Mp 209.5–210.5 8C; 1H NMR
(400 MHz, CDCl3) d 0.91 (t, J¼6.6 Hz, 3H), 1.34–1.36
(m, 4H), 1.43–1.51 (m, 2H), 1.76–1.83 (m, 2H), 3.98 (t,
J¼7.0 Hz, 2H), 6.91 (d, J¼7.0 Hz, 2H), 7.12–7.17 (m, 3H),
7.34 (d, J¼2.9 Hz, 1H), 7.51 (d, J¼7.3 Hz, 2H), 7.65 (d,
J¼2.9 Hz, 4H); 13C NMR (100 MHz, CDCl3) d 14.02,
22.59, 25.70, 29.20, 31.57, 68.18, 110.37, 114.97, 118.82,
122.74, 124.39, 125.21, 125.61, 125.92, 126.40, 126.95,
132.75, 134.75, 138.33, 139.41, 139.99, 144.29, 159.14;
HR-MS m/z (Mþ). Calcd for C27H25NOS2 443.1378. Found
443.1375.
1
6.92 (d, J¼8.8 Hz, 2H), 7.02 (dd, J¼3.5, 5.0 Hz, 1H), 7.10
(d, J¼4.0 Hz, 1H), 7.12 (d, J¼4.0 Hz, 1H), 7.17 (dd, J¼1.1,
3.5 Hz, 1H), 7.20 (dd, J¼1.1, 5.0 Hz, 1H), 7.52 (d,
J¼8.8 Hz, 2H); 13C NMR (100 MHz, CDCl3) d 55.36,
114.34, 122.64, 123.36, 124.10, 124.56, 126.91, 127.79,
128.05, 135.69, 137.59, 143.15, 159.30; HR-MS m/z (Mþ).
Calcd for C15H12OS2 272.0329. Found 272.0323.
3.4.17. 5-(4-Cyanophenyl)-2,20-bithiophene (19). Mp
1
148 8C; H NMR (400 MHz, CDCl3) d 7.05 (dd, J¼3.6,
5.1 Hz, 1H), 7.18 (d, J¼3.8 Hz, 1H), 7.24 (dd, J¼1.1,
3.6 Hz, 1H), 7.27 (dd, J¼1.1, 5.1 Hz, 1H), 7.34 (d,
J¼3.8 Hz, 1H), 7.64–7.69 (m, 4H); 13C NMR (100 MHz,
CDCl3) d 110.49, 118.81, 124.33, 124.85, 125.20, 125.67,
125.84, 128.02, 132.76, 136.69, 138.29, 139.13, 140.38;
HR-MS m/z (Mþ). Calcd for C15H9NS2 267.0176. Found
267.0171.
3.4.23. 5-(4-Methoxyphenyl)-50-(naphthalen-1-yl)-2,20-
1
bithiophene (25). Mp 135–136 8C; H NMR (400 MHz,
CDCl3) d 3.85 (s, 3H), 6.93 (d, J¼8.8 Hz, 2H), 7.14 (d,
J¼3.7 Hz, 1H), 7.17 (m, 2H), 7.25 (m, 1H), 7.48–7.56 (m,
5H), 7.60 (dd, J¼1.1, 7.0 Hz, 1H), 7.86 (d, J¼8.1 Hz, 1H),
7.89–7.92 (m, 1H), 8.31–8.33 (m, 1H); 13C NMR
(100 MHz, CDCl3) d 55.38, 114.38, 122.75, 123.61,
124.53, 125.29, 125.68, 126.08, 126.55, 126.94, 126.94,
128.01, 128.13, 128.40, 128.53, 131.68, 132.06, 133.93,
135.60, 137.83, 140.55, 143.22, 159.34; MS m/z 398 (Mþ).
Anal. Calcd for C25H18OS2: C, 75.34; H, 4.55; S, 16.09.
Found C, 75.08; H, 4.64; S, 15.83.
3.4.18. 5-(Naphthalen-1-yl)-2,20-bithiophene (20).15 Mp
95–97 8C; 1H NMR (400 MHz, CDCl3) d 7.05 (dd, J¼3.7,
5.1 Hz, 1H), 7.16 (d, J¼3.7 Hz, 1H), 7.23 (dd, J¼1.1,
3.8 Hz, 1H), 7.25–7.26 (m, 2H), 7.48–7.54 (m, 3H), 7.58–
7.61 (m, 1H), 7.86 (d, J¼8.4 Hz, 1H), 7.89–7.91 (m, 1H),
8.29–8.32 (m, 1H); 13C NMR (100 MHz, CDCl3) d 123.71,
123.98, 124.40, 125.27, 125.66, 126.08, 126.54, 127.86,
128.02, 128.07, 128.39, 128.54, 131.69, 132.03, 133.91,
137.34, 137.63, 140.80; MS m/z 292 (Mþ).
References and notes
3.4.19. 5-(4-tert-Butylphenyl)-50-(4-cyanophenyl)-2,20-
bithiophene (21). Mp 285.5–286 8C; H NMR (400 MHz,
1. (a) Roncali, J. Chem. Rev. 1997, 97, 173. (b) Katz, H. E.; Bao,
Z.; Gilat, S. L. Acc. Chem. Res. 2001, 34, 359. (c) Meng, H.;
Bao, Z.; Lovinger, A. J.; Wang, B.-C.; Mujsce, A. M. J. Am.
Chem. Soc. 2001, 123, 9214. (d) Mushrush, M.; Facchetti, A.;
Lefenfeld, M.; Katz, H. E.; Marks, T. J. J. Am. Chem. Soc.
2003, 125, 9414. (e) Yoshida, Y.; Tanigaki, N.; Yase, K.;
Hotta, S. Adv. Mater. 2000, 12, 1587. (f) Lee, S. A.; Hotta, S.;
Nakanishi, F. J. Phys. Chem. 2000, 104, 1827. (g) Raposo,
M. M. M.; Fonseca, A. M. C.; Kirsch, G. Tetrahedron 2004,
60, 4071.
1
DMF-d7) d 1.34 (s, 9H), 7.41–7.42 (m, 2H), 7.47 (d,
J¼3.7 Hz, 1H), 7.50 (d, J¼8.4 Hz, 2H), 7.65 (d, J¼8.4 Hz,
2H), 7.71 (d, J¼4.0 Hz, 1H), 7.85 (d, J¼8.8 Hz, 2H), 7.91
(d, J¼8.4 Hz, 2H); 13C NMR (100 MHz, CDCl3) d 30.41,
31.29, 110.93, 119.14, 124.83, 125.89, 125.89, 126.39,
126.47, 126.59, 127.70, 131.52, 133.61, 135.81, 138.70,
139.27, 140.96, 144.45, 151.81; HR-MS m/z (Mþ). Calcd
for C25H21NS2 399.1115. Found 399.1111.
2. (a) In Metal-catalyzed Cross-coupling Reactions; Dietrich, F.,
Stang, P. J., Eds.; Wiley-VCH: Weinheim, 1998. (b) Miyaura,
N., Ed.; Springer: Berlin, 2002. (c) Li, J. J.; Gribble, G. W.
Palladium in Heterocyclic Chemistry; Pergamon: Amsterdam,
2000.
3.4.20. 5-(4-Cyanophenyl)-50-(4-methoxyphenyl)-2,20-
bithiophene (22). Mp 187–188 8C; H NMR (400 MHz,
1
DMF-d7) d 3.87 (s, 3H), 7.06 (d, J¼8.7 Hz, 2H), 7.43–7.46
(m, 3H), 7.67 (d, J¼8.7 Hz, 2H), 7.79 (d, J¼8.7 Hz, 1H),
7.91 (d, J¼8.7 Hz, 2H), 7.95 (d, J¼8.7 Hz, 2H); 13C NMR
(100 MHz, DMF-d7) d 55.76, 110.77, 115.30, 124.25,
125.84, 126.42, 126.56, 126.92, 127.51, 127.97, 133.80,
135.10, 138.70, 139.35, 140.66, 144.42, 160.45, 162.88;
HR-MS m/z (Mþ). Calcd for C22H15NOS2 373.0595. Found
373.0599.
3. (a) Aoyagi, Y.; Inoue, A.; Koizumi, I.; Hashimoto, R.;
Tokunaga, K.; Gohma, K.; Komatsu, J.; Sekine, K.; Miyafuji,
A.; Kunoh, J.; Homma, R.; Akita, Y.; Ohta, A. Heterocycles
1992, 33, 257. Reviews: (b) Miura, M.; Nomura, M. In Cross-
coupling Reactions; Miyaura, N., Ed.; Springer: Berlin, 2002;
´
p 211. (c) Hassan, J.; Sevignon, M.; Gozzi, C.; Schulz, E.;
Lemaire, M. Chem. Rev. 2002, 102, 1359.
3.4.21. 5-(4-Cyanophenyl)-50-(naphthalen-1-yl)-2,20-
4. (a) Pivsa-Art, S.; Satoh, T.; Kawamura, Y.; Miura, M.;
Nomura, M. Bull. Chem. Soc. Jpn 1998, 71, 467. (b) Chabert,
J. F. D. C.; Joucla, L.; David, A.; Lemaire, M. Tetrahedron
2004, 60, 3221. (c) Glover, B.; Harvey, K. A.; Liu, B.; Sharp,
M. J.; Tymoschenko, M. F. Org. Lett. 2003, 5, 301.
5. (a) Okazawa, T.; Satoh, T.; Miura, M.; Nomura, M. J. Am.
Chem. Soc. 2002, 124, 5286. (b) Yokooji, A.; Okazawa, T.;
Satoh, T.; Miura, M.; Nomura, M. Tetrahedron 2003, 59,
5685.
1
bithiophene (23). Mp 197.5–198 8C; H NMR (400 MHz,
DMF-d7) d 7.41 (d, J¼3.7 Hz, 1H), 7.55 (d, J¼4.0 Hz, 1H),
7.61–7.66 (m, 4H), 7.71 (dd, J¼1.1, 7.0 Hz, 1H), 7.83 (d,
J¼4.0 Hz, 1H), 7.93 (d, J¼8.8 Hz, 2H), 7.98 (d, J¼8.8 Hz,
2H), 8.02–8.09 (m, 2H), 8.31–8.33 (m, 1H); 13C NMR
(100 MHz, DMF-d7) d 115.89, 124.41, 130.73, 130.98,
131.24, 131.32, 131.50, 132.07, 132.70, 133.04, 133.82,
134.34, 134.65, 134.70, 136.89, 137.01, 138.84, 139.78,
142.38, 143.66, 143.98, 146.10, 146.83; HR-MS m/z (Mþ).
Calcd for C25H15NS2 393.0646. Found 393.0651.
6. (a) Terao, Y.; Wakui, H.; Satoh, T.; Miura, M.; Nomura, M.
J. Am. Chem. Soc. 2001, 123, 10407. (b) Terao, Y.; Wakui, H.;

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10357.
8. Yasukawa, T.; Satoh, T.; Miura, M.; Nomura, M. J. Am. Chem.
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13. Takahashi, K.; Suzuki, T.; Akiyama, K.; Ikegami, Y.;
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9276.