Preparation of 4,7-dibromobenzo[b]thiophene as a versatile building block and synthetic application to a bis(ethynylthienyl)oligoarene system

Article abstract of DOI:10.1246/bcsj.20100345

Benzo[b]thiophene, 4,7-dibromobenzo[b]thiophene, thieno[3,2-b]thiophene, and 3-bromothieno[3,2-b]thiophene were prepared by AuCl-catalyzed cyclization of (t-butylsulfanyl)(ethynyl)benzenes or (t-butylsulfanyl)(ethynyl)thiophenes. Several reactions of 4,7-dibromobenzo[b]thiophene were investigated, including metallation and cross coupling reactions.

Full text of DOI:10.1246/bcsj.20100345

© 2012 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 85, No. 5, 613-623 (2012)
613
Preparation of 4,7-Dibromobenzo[b]thiophene
as a Versatile Building Block and Synthetic Application
to a Bis(ethynylthienyl)oligoarene System
Takuya Yamamoto, Hiroshi Katsuta, Kozo Toyota,* Takeaki Iwamoto, and Noboru Morita
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, Miyagi 980-8578
Received December 8, 2010; E-mail: toyota@m.tohoku.ac.jp
Benzo[b]thiophene, 4,7-dibromobenzo[b]thiophene, thieno[3,2-b]thiophene, and 3-bromothieno[3,2-b]thiophene
were prepared by AuCl-catalyzed cyclization of (t-butylsulfanyl)(ethynyl)benzenes or (t-butylsulfanyl)(ethynyl)thio-
phenes. Several reactions of 4,7-dibromobenzo[b]thiophene were investigated, including metallation and cross coupling
reactions.
Ring-fused thiophenes, such as benzo[b]thiophenes and
thieno[3,2-b]thiophenes, have attracted much interest in the
fields of physical organic chemistry, materials science, and
synthetic organic chemistry.1 Brominated benzo[b]thiophenes
and thieno[3,2-b]thiophenes are often used for introduction of
substituents and functional groups to the fused rings. Con-
sequently, preparations of various bromobenzo[b]thiophenes2
and bromothieno[3,2-b]thiophenes3 have been reported. How-
ever, direct and selective introduction of bromine atom to the 4-
and 7-positions of benzo[b]thiophene is difficult: Electrophilic
substitution reactions of parent benzo[b]thiophene proceed
normally at the 3-, 5-, or 6-positions. In fact, 4,7-dibromo-
benzo[b]thiophene (1a, Chart 1), without substituents at the
other positions, remained unexplored. Nevertheless, develop-
ment of a new synthetic method for ring-fused thiophenes may
find a route to the missing bromobenzothiophene derivatives:
We report here a preparation and reactions of hitherto unknown
compound 1a. Preparations of parent benzo[b]thiophene (1b)
and thieno[3,2-b]thiophene derivatives 2a and 2b as well as
some oligoarenes containing the ring-fused thiophene moieties
are also described.
thiophene (1b) at the 4- and/or 7-positions is difficult as
mentioned above. Among some possible routes to benzo[b]-
thiophenes,4 a cyclization of ethynyl(sulfanyl)benzene deriva-
tive seemed to be promising. Nakamura and co-workers re-
ported Au-catalyzed cyclization of 3 (Scheme 1, R2 º H).4a,4b
In this reaction, a substituent R2 on the sulfur atom rearranges
to the 3-position of the cyclized product to give 4. However,
if we use a t-butylsulfanyl group as a substituent, the t-butyl
group may be removed by appropriate reagent under acidic
conditions, before or after cyclization. Based on this plan,
preparation of parent 1b was investigated as follows. 2-t-Butyl-
sulfanylbenzaldehyde (6b)5 was prepared by the reaction of 2-
bromobenzaldehyde (5b) with t-BuSNa (Scheme 2). Reaction
of 6b with dimethyl 1-diazo-2-oxo-2-phenylethylphosphonate
(7)6 gave 2-(t-butylsulfanyl)(ethynyl)benzene (8b). When 8b
was treated with AuCl in 1,4-dioxane and water (6:1) for
10 min, 1b was obtained in 56% yield.
For preparation of the desired congener 1a, we chose com-
mercially available 3,6-dibromo-2-fluorobenzaldehyde (5a) as
a starting material. Reaction of 5a with t-BuSNa gave 6a,
which was converted to 8a, by reaction with 7. Treatment of
8a with AuCl in 1,4-dioxane and water afforded 1a in 97%
yield.
Results and Discussion
In a synthetic plan of 1a, bromine atoms should be intro-
duced before construction of the benzothiophene skeleton,
because the straightforward bromination of parent benzo[b]-
3-Bromothieno[3,2-b]thiophene (2a)3a was also pre-
pared (Scheme 3) by the (t-butylsulfanyl)(ethynyl)arene/AuCl
method as follows. A reaction of 3,4-dibromothiophene-
2-carbaldehyde (9a) with t-BuSNa formed 10a, which was
converted to 11a by reaction with 7. When 11a was treated with
R
S
R1
R2
cat. AuCl
S
S
R
R1
R
S R2
S
toluene, 25 °C
1a: R=Br
b: R=H
2a: R=Br
b: R=H
3
4
Scheme 1. AuCl-catalyzed synthesis of benzo[b]thio-
phenes.4a,4b
Chart 1.
Published on the web April 28, 2012; doi:10.1246/bcsj.20100345

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Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
Preparation of 4,7-Dibromobenzo[b]thiophene
R
R
Br
Br
CHO
X
CHO
(i)
(i)
(ii)
Li
Me
S
t-Bu
S
S
R
R
Br
Br
Br
5a: R=Br, X=F
b: R=H, X=Br
6a,b
12
1a
Br
Li
R
R
(iii)
(iv)
(ii)
O
(iii)
1a,b
O
S
S
S
t-Bu
MeO P
MeO
Ph
13
N2
7
8a,b
(v)
Scheme 2. Reagents and conditions: (i) t-BuSNa, N,N-
dimethylformamide (DMF), ¹30 °C, 7 h; (ii) K2CO3,
MeOH, 0 °C to r.t.; (iii) AuCl (5 mol %), 1,4-dioxane,
H2O, r.t., 10 min.
Br
Br
(vi)
(vii)
S
S
S
CHO
Br
CHO
(i)
S
S
I
S
t-Bu
14
15
16
S
S
R
R
Scheme 4. Reagents and conditions: (i) LDA, THF, ¹78 °C,
then 0 °C, 30 min; (ii) MeI, ¹78 °C, then r.t., 15 h; (iii) n-
BuLi, THF, ¹78 °C, 30 min; (iv) MeOH, ¹78 °C; (v) 1,2-
diiodoethane, Et2O, ¹78 °C, then r.t., 2 h; (vi) 3-thienyl-
boronic acid, [Pd(PPh3)4], K2CO3, THF, H2O, 45 °C, 12 h;
(vii) n-BuLi, THF, Et2O, ¹78 °C, 30 min, then aq. NH4Cl.
9a: R = Br
b: R = H
10a,b
(iii)
S
7
2a,b
(ii)
S
t-Bu
R
11a,b
S
Scheme 3. Reagents and conditions: (i) t-BuSNa, DMF,
¹30 °C, 4 h (for 10a) or r.t., 12 h (for 10b); (ii) K2CO3,
MeOH, 0 °C to r.t., 12 h; (iii) AuCl (2-8 mol %), 1,4-
dioxane, H2O, r.t., 3 h.
(i)
S
S
AuCl in 1,4-dioxane and water, 2a was obtained in 88% yield.
Similarly, parent thieno[3,2-b]thiophene (2b) was prepared,
from 3-bromothiophene-2-carbaldehyde (9b), via 10b and 11b.
It should be mentioned that conventional preparative routes
to 2a3b and 2b3c include high-temperature decarboxylation
(Cu/quinoline/260 °C). Thus, the present Au-catalyzed method
has several advantages from viewpoints of the numbers of
reaction steps, yield, and reaction temperature.
17
1a
S
(ii)
As we could obtain a novel dibromobenzo[b]thiophene
1a, we then investigated reactions of 1a (Schemes 4 and 5). In
the first place, metallation reactions of 1a (Scheme 4) were
investigated and reactivities at the 2-, 4-, and 7-positions were
evaluated: Lithiation of 1a with 1 molar equivalent of lithium
N,N-diisopropylamide (LDA) occurred at the 2-position of 1a.
When the reaction mixture was quenched with iodomethane,
4,7-dibromo-2-methylbenzo[b]thiophene (12) was obtained in
74% yield. On the other hand, a reaction of 1a with butyl-
lithium (1 molar equivalent) followed by treatment with MeOH
S
18
S
Scheme 5. Reagents and conditions: (i) 2-(2-thienyl)-
4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2.4 molar equiv-
alents), [Pd(PPh3)4], K2CO3, 1,4-dioxane, H2O, 80 °C,
16 h; (ii) 3-thienylboronic acid (2.4 molar equivalents),
[Pd(PPh3)4], K2CO3, 1,4-dioxane, H2O, 80 °C, 15 h.

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
615
gave 13,2c via lithium-bromine exchange. When the metal-
lation reaction was quenched by 1,2-diiodoethane, 4-bromo-7-
iodo derivative 14 was obtained in 83% yield. These results
show that the metallations at the 2-, 4-, and 7-positions are
well controlled by choosing the lithium reagent. This selectiv-
ity helps sophisticated constructions of oligoarenes containing
the benzo[b]thiophene-4,7-diyl moiety (see below).
(triisopropylsilyl)ethynyl groups] was carried out by a cross
coupling of 12 with 2.3 molar equivalents of 25 to give 19a
in 58% yield (Scheme 7).
n-Hex
S
Sii-Pr3
In the second place, cross coupling reactions of above
compounds were investigated (Schemes 4 and 5). Suzuki-
Miyaura coupling of 14 with 3-thienylboronic acid afforded
15, which was converted to 16 (Scheme 4). The spectral data
of 16 obtained in this experiment matched with the reported
data of 16,7 confirming the structures of 14 and 15. Similarly,
Suzuki-Miyaura coupling of 1a with 2-(2-thienyl)-4,4,5,5-
tetramethyl-1,3,2-dioxaborolane (2.4 molar equivalents) or 3-
thienylboronic acid (2.4 molar equivalents) afforded 17 or 18
in 80 and 94% yield, respectively (Scheme 5). It should be
mentioned that formation of 17 has been supposed in the
literature of Curtis and co-workers8 in the dehydrogenation
reaction of 4,7-di(2-thienyl)-4,5,6,7-tetrahydrobenzo[b]thio-
phene with tetrachloro-p-benzoquinone. However, the structure
could not be experimentally determined, because an attempted
alternative synthesis was unsuccessful by their hands. Compar-
ison of the physical data of 17 supported the assignment of
Curtis et al. and the problem was solved.
n-Hex
S
Sii-Pr3
R
S
S
Me
Me
S
S
S
S
Sii-Pr3
Sii-Pr3
S
n-Hex
Based on the results described above, applications of com-
pounds 1a and 2a to preparations of peptide-inspired bis(2-
ethynyl-3-thienyl)oligoarenes9 19a, 19b, and 20 (Chart 2) were
planned in the third place (Schemes 6-9). Preparations of the
terminal units of 19 and 20 are shown in Scheme 6: boronates
25 and 26 were prepared from 219d via 22-24. Preparation of
oligoarene 19a with three side chains [one methyl and two
Sii-Pr3
20
19a: R=i-Pr3Si
b: R=Ph
S
n-Hex
Chart 2.
n-Hex
n-Hex
n-Hex
S
S
S
S
Sii-Pr3
Sii-Pr3
Ph
(i)
(ii)
(iii)
21
Br
Br
22
Br
23
Br
24
(iv)
(iv)
n-Hex
n-Hex
S
S
Sii-Pr3
Ph
B
B
O
O
O
O
25
26
Scheme 6. Reagents and conditions: (i) LDA, THF, ¹78 °C, 70 min, then 1-iodohexane, ¹78 °C, then 50 °C, 3 h; (ii) tetrabutyl-
ammonium fluoride, THF, r.t., 70 min; (iii) iodobenzene, [PdCl2(PPh3)2], CuI, N,N-diisopropylamine, THF, 50 °C, 15 h; (iv) n-BuLi,
THF, ¹78 °C then 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, ¹78 °C, then r.t.

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Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
Preparation of 4,7-Dibromobenzo[b]thiophene
Br
S
25 (2.3 mol equiv)
Ref. 9d
Me
19a
S
2a
S
(i)
Sii-Pr3
B
Br
O
O
12
30
25
(1.0 mol equiv)
(i)
n-Hex
S
Sii-Pr3
n-Hex
n-Hex
(i)
i-Pr3Si
(ii)
S
S
Sii-Pr3
Sii-Pr3
S
19a
+
+
31
S
S
Me
Me
n-Hex
S
S
Br
Br
Sii-Pr3
27
28
Scheme 7. Reagents and conditions: (i) [Pd(PPh3)4], K2CO3,
1,4-dioxane, H2O, 90 °C, 13 h.
(iii)
20
31
+
i-Pr3Si
Br
Br
S
(i)
Me
Me
S
S
S
B
Br
I
O
O
12
29
32
(ii)
(iii)
Scheme 9. Reagents and conditions: (i) 22, [Pd(PPh3)4],
K2CO3, THF, toluene, H2O, 80 °C, 14 h; (ii) n-BuLi, THF,
¹78 °C, 1 h, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane, ¹78 °C, then r.t., 3 h; (iii) 29 (0.35 molar equiva-
lent), 2-dicyclohexylphosphino-2¤,6¤-dimethoxybiphenyl,
Pd(OAc)2, K2CO3, THF, 50 °C, 2 d.
28
19b
Scheme 8. Reagents and conditions: (i) n-BuLi, THF,
¹78 °C, 30 min, then 1,2-diiodoethane, ¹78 °C, then r.t.,
2 h; (ii) 25 (1.0 molar equivalent), [Pd(PPh3)4], K2CO3,
1,4-dioxane, H2O, 80 °C, 46 h; (iii) 26 (1.0 molar
equivalent), [Pd(PPh3)4], K2CO3, 1,4-dioxane, H2O,
90 °C, 13 h.
and (triisopropylsilyl)ethynyl side chains] with a controlled
sequence (89% yield).
It should be mentioned that a reaction of 12 with 1 molar
equivalent of 25 under similar conditions was not regioselec-
tive: The reaction gave a mixture of 27 and 28 (ca. 1:0.4 ratio)
as well as 19a. An attempted separation of 27 and 28 by
column chromatography was unsuccessful. However, when the
mixture of 27 and 28 was subjected to a further cross coupling
reaction with 25, compound 19a was obtained in 66% yield.
Confirmation of the structure of 28 and preparation of 19b
was carried out as follows (Scheme 8). Compound 12 was
converted to 29, which was then reacted with 25 under the
cross coupling conditions to give an authentic 28 in 80% yield.
A cross coupling of 28 with 26 afforded 19b, which con-
tains three different side chains [i.e., phenylethynyl, methyl,
Thus, for the purpose of preparation of peptide-inspired
systems,9,10 utilization of the 4-bromo-7-iodobenzo[b]thio-
phene derivatives is a promising method. Sequences of side
chains are regarded as important in such systems.
For further elongation of the (pseudo)axes of the oligo-
arenes, the benzothiophene spacer and the thienothiophene
spacer were combined as follows (Scheme 9). Compound 2a
was converted to (triisopropylsilyl)ethynyl-substituted com-
pound 30.9d Suzuki-Miyaura cross coupling of 30 with 22
afforded 31 in 84% yield. The thienothiophene moiety of 31
was again converted to a dioxaborolane derivative 32 (97%
yield) and subjected to Suzuki coupling with 29 (0.35 molar
equivalent) to give the extended compound 20 along with the

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
617
thienothiophene 31. Although the yield of 20 in this step is low
(5% yield after repetitive purification), the major product 31
(65% yield) can be reused as a starting material of the reaction
described above.
and purified by silica gel column chromatography to give 217
mg (0.623 mmol, 70% yield) of 8a: Colorless crystals, mp
1
56-57 °C; H NMR (400 MHz, CDCl3): ¤ 1.42 (9H, s, t-Bu),
3
3.66 (1H, s, C¸CH), 7.45 (1H, d, J = 8.7 Hz, phenyl), and
3
In summary, we prepared parent benzo[b]thiophene, 4,7-
dibromobenzo[b]thiophene, parent thieno[3,2-b]thiophene,
and 3-bromothieno[3,2-b]thiophene. Several oligoarenes such
as 19a were prepared from 4,7-dibromobenzo[b]thiophene
(1a). 4-Bromo-7-iodobenzo[b]thiophene (29) was also prepared
and utilized to construct oligoarene 20. A sequence of three
different side chains was controlled, in the preparation of 19b,
by utilization of 29. Thus, 4-bromo-7-halogenobenzo[b]thio-
phenes as well as 3-bromothieno[3,2-b]thiophene are promis-
ing starting materials for construction of sophisticated oligo-
arene systems.
7.54 (1H, d, J = 8.7 Hz, phenyl); 13C{1H} NMR (100 MHz,
CDCl3): ¤ 31.8 (Me), 52.9 (CMe3), 82.5 (C¸C), 87.1 (C¸C),
126.0, 133.4, 133.7, 133.8, 133.9, and 138.8; IR (KBr): 3250
(C¸CH), 2957, 2106 (C¸C), 1470, 1456, 1414, 1366, 1348,
1161, 1117, 1073, 824, 774, and 737 cm¹1. HRMS (EI):
Found: m/z 345.9026. Calcd for C12H12Br2S: 345.9026. Anal.
Found: C, 41.32; H, 3.55%. Calcd for C12H12Br2S: C, 41.40;
H, 3.47%.
2-(t-Butylsulfanyl)(ethynyl)benzene (8b). To a mixture
of 7 (737 mg, 2.90 mmol) and K2CO3 (983 mg, 7.11 mmol) in
MeOH (6.5 mL) was added a solution of 6b5 (461 mg, 2.37
mmol) in MeOH (3.0 mL) at 0 °C under N2. The reaction
mixture was stirred at room temperature for 1 h. Upon com-
pletion, the mixture was poured into water, and extracted with
Et2O. The organic layer was washed with brine and dried
over MgSO4. The filtrate was concentrated under reduced
pressure, and separated by silica gel column chromatography to
give 324 mg (1.70 mmol, 72% yield) of 8b: Pale yellow oil;
1H NMR (400 MHz, CDCl3): ¤ 1.35 (9H, s, t-Bu), 3.30 (1H, s,
C¸CH), 7.30-7.33 (2H, m, phenyl), and 7.58-7.61 (2H, m,
phenyl). This compound was used in succeeding reactions
without further purification.
Experimental
Apparatus.
Melting points were measured on a
Yanagimoto MP-J3 micro melting point apparatus and are
not corrected. NMR spectra were recorded on a Bruker Avance-
400 or a JEOL ECA-600 spectrometer. UV spectra were mea-
sured on a JASCO V-660 spectrometer. IR spectra were
obtained on a Shimadzu FTIR-8100M spectrometer or a
JASCO FT/IR-4100 spectrometer. MS (EI, 70 eV) spectra were
taken on a Hitachi M-2500S spectrometer. FT-ICR-MS (ESI)
spectra were measured on a Bruker APEX III spectrometer.
Elemental analyses were performed at Analytical Research
Center for Giant Molecules, Graduate School of Science,
Tohoku University.
4,7-Dibromobenzo[b]thiophene (1a).
To a solution of
compound 8a (50.4 mg, 0.145 mmol) in 1,4-dioxane (0.5 mL)
and water (0.1 mL) was added AuCl (1.7 mg, 0.0072 mmol) in
1,4-dioxane (0.1 mL) under N2. The reaction mixture was
stirred at room temperature for 10 min. Upon completion, the
solvent was removed and the residue was purified by silica
gel column chromatography to give 41.0 mg (0.140 mmol,
3,6-Dibromo-2-(t-butylsulfanyl)benzaldehyde (6a). To a
solution of NaH (187 mg, 7.80 mmol) in N,N-dimethylform-
amide (DMF, 3.6 mL) was added t-BuSH (0.88 mL, 7.8 mmol)
in DMF (3.0 mL) at 0 °C over 15 min under N2. The reaction
mixture was stirred at 0 °C for 30 min, and then 3,6-dibromo-2-
fluorobenzaldehyde (5a, 2.00 g, 7.09 mmol) in DMF (1.0 mL)
was added at ¹30 °C. The reaction mixture was stirred at
¹30 °C for 7 h. Upon completion, the mixture was poured into
saturated aqueous NH4Cl, and extracted with Et2O. The organic
layer was washed with brine and dried over MgSO4. The filtrate
was concentrated under reduced pressure, and purified by silica
gel column chromatography to give 2.33 g (6.65 mmol, 94%
1
97% yield) of 1a: Colorless needles, mp 77-78 °C; H NMR
3
(400 MHz, CDCl3): ¤ 7.34 (1H, d, J = 8.0 Hz), 7.41 (1H, d,
3
3
3J = 8.0 Hz), 7.55 (1H, d, J = 5.6 Hz), and 7.57 (1H, d, J =
5.6 Hz); 13C{1H} NMR (100 MHz, CDCl3): ¤ 114.9, 116.4,
125.4, 127.9, 128.2, 128.6, 140.0, and 142.2; IR (KBr): 3083,
1487, 1437, 1354, 1314, 1302, 1182, 1111, 1094, 1069, 905,
831, 806, and 754 cm¹1. HRMS (EI): Found: m/z 289.8399.
Calcd for C8H4Br2S: 289.8400. Anal. Found: C, 33.10; H,
1.53%. Calcd for C8H4Br2S: C, 32.91; H, 1.38%.
1
yield) of 6a: Yellow oil; H NMR (400 MHz, CDCl3): ¤ 1.32
3
(9H, s, t-Bu), 7.55 (1H, d, J = 8.6 Hz, phenyl), 7.71 (1H, d,
Benzo[b]thiophene (1b). To a solution of 8b (27.6 mg,
0.145 mmol) in 1,4-dioxane (0.5 mL) and water (0.1 mL) was
added AuCl (1.7 mg, 0.0073 mmol) in 1,4-dioxane (0.1 mL)
under N2. The reaction mixture was stirred at room temperature
for 10 min. Upon completion, the solvent was removed and the
residue was purified by silica gel column chromatography to
give 10.8 mg (0.0805 mmol, 56% yield) of 1b.
4-Bromo-3-(t-butylsulfanyl)thiophene-2-carbaldehyde
(10a). To a solution of NaH (17.8 mg, 0.741 mmol) in THF
(1.0 mL) was added t-BuSH (0.084 mL, 0.74 mmol) in DMF
(1.0 mL) at 0 °C under N2. The resulting mixture was stirred
at 0 °C for 5 min, and then 9a (100 g, 0.370 mmol) in DMF
(1.0 mL) was added at ¹30 °C. The reaction mixture was stirred
for 4 h at ¹30 °C, and then allowed to warm to room temper-
ature and stirred for 12 h. Upon completion, the mixture was
poured into saturated aqueous NH4Cl, and extracted with Et2O.
The organic layer was washed with brine and dried over
3J = 8.6 Hz, phenyl), and 10.4 (1H, s, CHO); 13C{1H} NMR
(100 MHz, CDCl3): ¤ 31.4 (Me), 52.4 (CMe3), 119.6, 134.4,
136.1, 136.6, 137.3, 143.3, and 192.1 (CHO); IR (neat): 3101,
2977, 2872, 1696, 1545, 1472, 1460, 1418, 1395, 1366, 1335,
¹1
1250, 1202, 1157, 1121, 1069, 968, 835, 762, and 743 cm
.
HRMS (ESI): Found: m/z 372.8869. Calcd for C11H12Br2-
NaOS: (M + Na)+, 372.8868.
3,6-Dibromo-2-(t-butylsulfanyl)(ethynyl)benzene
(8a).
To a mixture of dimethyl 1-diazo-2-oxo-2-phenylethylphos-
phonate (7) (270 mg, 1.06 mmol) and K2CO3 (367 mg, 2.66
mmol) in MeOH (6.5 mL) was added a solution of 6a (312 mg,
0.886 mmol) in MeOH (3.0 mL) at 0 °C under N2. The reaction
mixture was stirred at room temperature for 2 h. Upon com-
pletion, the mixture was poured into water, and extracted with
Et2O. The organic layer was washed with brine and dried over
MgSO4. The filtrate was concentrated under reduced pressure,

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Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
Preparation of 4,7-Dibromobenzo[b]thiophene
1
MgSO4. The filtrate was concentrated under reduced pressure,
and purified by silica gel column chromatography to give
80.0 mg (0.287 mmol, 78% yield) of 10a: Yellow crystals, mp
116-117 °C; 1H NMR (400 MHz, CDCl3): ¤ 1.35 (9H, s, t-Bu),
7.78 (1H, d, 5J = 1.2 Hz, 5-thienyl), and 10.1 (1H, d, 5J =
1.2 Hz, CHO); 13C{1H} NMR (100 MHz, CDCl3): ¤ 31.2
(CMe3), 50.5 (CMe3), 122.2, 131.2, 139.8, 147.5, and 185.3
(CHO); IR (KBr): 3106, 2975, 2957, 2865, 2847, 1653, 1472,
1458, 1399, 1362, 1335, 1308, 1208, 1163, 1138, 932, 860,
799, 758, and 671 cm¹1. HRMS (EI): Found: m/z 277.9433.
Calcd for C9H11BrOS2: 277.9435. Anal. Found: C, 38.77;
H, 4.03%. Calcd for C9H11BrOS2: C, 38.71; H, 3.97%.
mg (2.40 mmol, 90% yield) of 11b: Yellow oil; H NMR (400
MHz, CDCl3): ¤ 1.34 (9H, s, t-Bu), 3.52 (1H, s, C¸CH), 7.03
(1H, d, 3J = 5.1 Hz, thienyl), and 7.25 (d, 3J = 5.1 Hz, thienyl);
13C{1H} NMR (100 MHz, CDCl3): ¤ 31.1 (CMe3), 48.6
(CMe3), 76.6 (C¸C), 84.5 (C¸C), 125.7, 127.8, 134.7, and
134.9; IR (neat): 3293 (C¸CH), 2961, 2107 (C¸C), 1719,
1470, 1456, 1402, 1364, 1279, 1169, 1076, 884, 725, 644,
and 596 cm¹1. HRMS (EI): Found: m/z 196.0376. Calcd for
C10H12S2: 196.0380.
3-Bromothieno[3,2-b]thiophene (2a). A mixture of 11a
(54.4 mg, 0.197 mmol) and AuCl (2.3 mg, 0.016 mmol) in 1,4-
dioxane (1.7 mL) and water (0.30 mL) was stirred at room
temperature for 3 h under N2. Upon completion, the mixture
was poured into water, and extracted with CHCl3. The organic
layer was washed with brine and dried over MgSO4. The filtrate
was concentrated under reduced pressure, and purified by silica
gel column chromatography to give 40.6 mg (0.173 mmol, 88%
yield) of 2a.
Thieno[3,2-b]thiophene (2b). To a solution of 11b (100
mg, 0.510 mmol) in 1,4-dioxane (3.4 mL) and water (0.73 mL)
was added AuCl (2.4 mg, 0.010 mmol) in 1,4-dioxane (1.0 mL)
under N2. The reaction mixture was stirred at room temperature
for 3 h. Upon completion, the mixture was poured into water,
and extracted with Et2O. The organic layer was washed with
brine and dried over MgSO4. The filtrate was concentrated
under reduced pressure, and purified by silica gel column
chromatography to give 58.0 mg (0.414 mmol, 81% yield)
of 2b.
3-(t-Butylsulfanyl)thiophene-2-carbaldehyde (10b). To a
solution of NaH (252 mg, 10.5 mmol) in DMF (9.0 mL) was
added t-BuSH (1.2 mL, 11 mmol) in DMF (3.0 mL) at 0 °C
under N2. The resulting mixture was stirred at 0 °C for 15 min,
and then 9b (1.00 g, 5.23 mmol) in DMF (3 mL) was added at
0 °C. The reaction mixture was then allowed to warm to room
temperature and stirred for 12 h. Upon completion, the mixture
was poured into saturated aqueous NH4Cl, and extracted with
Et2O. The organic layer was washed with brine and dried over
MgSO4. The filtrate was concentrated under reduced pressure,
and purified by silica gel column chromatography to give
1
686 mg (3.43 mmol, 66% yield) of 10b: Yellow oil; H NMR
3
(400 MHz, CDCl3): ¤ 1.34 (9H, s, t-Bu), 7.19 (1H, d, J =
5.0 Hz, 4-thienyl), 7.73 (1H, dd, J = 5.0 and 1.2 Hz, 5-thienyl),
and 10.2 (1H, d, 5J = 1.2 Hz, CHO); 13C{1H} NMR (100 MHz,
CDCl3): ¤ 31.0 (CMe3), 47.8 (CMe3), 133.0, 136.3, 139.3,
145.8, and 184.7 (CHO); IR (neat): 2965, 1665, 1456, 1412,
1364, 1339, 1215, 1167, 1156, 911, 826, 745, 687, 666,
and 648 cm¹1. HRMS (ESI): Found: m/z 223.0221. Calcd for
C9H12NaOS2: (M + Na)+, 223.0222.
4,7-Dibromo-2-methylbenzo[b]thiophene (12).
To a
solution of 1a (100 mg, 0.342 mmol) in 3.0 mL of tetra-
hydrofuran (THF) was added 0.374 mmol of lithium N,N-
diisopropylamide (LDA, 0.567 M solution in THF, 0.66 mL;
M = mol dm¹3) at ¹78 °C under N2. The reaction mixture was
stirred at 0 °C for 30 min, and then iodomethane (0.026 mL,
0.41 mmol) was added at ¹78 °C. The reaction mixture was
allowed to warm to room temperature and stirred for 15 h.
Upon completion, the mixture was poured into saturated
aqueous NH4Cl, and extracted with Et2O. The organic layer
was washed with brine and dried over MgSO4. The filtrate was
concentrated under reduced pressure, and purified by silica
gel column chromatography to give 77.1 mg (0.252 mmol, 74%
yield) of 12: Colorless needles, mp 111-112 °C; 1H NMR (400
4-Bromo-3-(t-butylsulfanyl)-2-ethynylthiophene
(11a).
To a mixture of 10a (138 mg, 0.493 mmol) and K2CO3 (205
mg, 1.48 mmol) in MeOH (3.0 mL) was added a solution of
7 (251 mg, 0.986 mmol) in MeOH (2.0 mL) at 0 °C under N2.
The reaction mixture was stirred at room temperature for 12 h.
Upon completion, the mixture was poured into water, and
extracted with Et2O. The organic layer was washed with brine
and dried over MgSO4. The filtrate was concentrated under
reduced pressure, and purified by silica gel column chroma-
tography to give 77.9 mg (0.283 mmol, 57% yield) of 11a:
Yellow crystals, mp 47-49 °C; 1H NMR (400 MHz, CDCl3):
¤ 1.36 (9H, s, t-Bu), 3.55 (1H, s, C¸CH), and 7.28 (1H, s, 5-
thienyl); 13C{1H} NMR (100 MHz, CDCl3): ¤ 31.5 (CMe3),
51.7 (CMe3), 76.7 (C¸C), 85.4 (C¸C), 120.0, 123.8, 129.5,
and 135.8; IR (KBr): 3306 (C¸CH), 3254 (C¸CH), 3114,
3077, 2959, 2896, 2851, 1466, 1455, 1397, 1366, 1300, 1163,
905, 770, 735, and 685 cm¹1. HRMS (EI): Found: m/z
273.9483. Calcd for C10H11BrS2: 273.9486.
4
MHz, CDCl3): ¤ 2.61 (3H, d, J = 1.2 Hz, benzothienyl-Me),
7.21 (1H, q, 4J = 1.2 Hz, 3-benzothienyl), 7.24 (1H, d, 3J = 8.1
Hz, benzothienyl), and 7.34 (1H, d, 3J = 8.1 Hz, benzothienyl);
13C{1H} NMR (100 MHz, CDCl3): ¤ 16.3 (benzothienyl-Me),
114.2, 115.0, 123.0, 126.9, 128.5, 140.6, 141.6, and 143.2;
IR (KBr): 1846, 1522, 1433, 1358, 1348, 1202, 1186, 1121,
1109, 1084, 912, 814, and 797 cm¹1. HRMS (EI): Found:
m/z 303.8557. Calcd for C9H6Br2S: 303.8554. Anal. Found:
C, 35.57; H, 1.99%. Calcd for C9H6Br2S: C, 35.32; H, 1.98%.
3-(t-Butylsulfanyl)-2-ethynylthiophene (11b).
To a
mixture of 10b (533 mg, 2.66 mmol) and K2CO3 (1.10 g, 7.98
mmol) in MeOH (6.0 mL) was added a solution of 7 (879 mg,
3.46 mmol) in MeOH (3.0 mL) at 0 °C under N2. The reaction
mixture was stirred at room temperature for 12 h. Upon com-
pletion, the mixture was poured into water, and extracted with
Et2O. The organic layer was washed with brine and dried over
MgSO4. The filtrate was concentrated under reduced pressure,
and purified by silica gel column chromatography to give 470.4
4-Bromobenzo[b]thiophene (13).
To a solution of 1a
(59.0 mg, 0.202 mmol) in THF (2 mL) was added 0.23 mmol of
n-BuLi (1.65 M solution in hexane, 0.14 mL) at ¹78 °C under
N2. The resulting mixture was stirred at ¹78 °C for 30 min, and
then quenched with 1 mL of MeOH. To the mixture was added
EtOAc and water, the organic phase was separated, washed
with brine, and dried over MgSO4. The filtrate was concen-
trated under reduced pressure and the residue was treated with

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
619
silica gel column chromatography (hexane) to give 22.8 mg
(0.107 mmol, 53% yield) of 13.2c 1H NMR (400 MHz, CDCl3):
¤ 7.20 (1H, t, J = 8.0 Hz), 7.48-7.55 (3H, m), and 7.81 (1H,
d, 3J = 8.0 Hz); 13C{1H} NMR (100 MHz, CDCl3): ¤ 117.4,
thienyl), 7.56 (1H, dd, J = 4.8 and 1.2 Hz, 4-thienyl), 7.75
(1H, dd, J = 3.0 and 1.2 Hz, 2-thienyl), and 7.80 (1H, dd,
J = 7.8 and 1.2 Hz, 4-benzothienyl); 13C{1H} NMR (150 MHz,
CDCl3): ¤ 122.5 (2-thienyl), 122.6 (4-benzothienyl), 123.7 (6-
benzothienyl), 124.4 (3-benzothienyl), 124.7 (5-benzothienyl),
126.0 (5-thienyl), 126.5 (2-benzothienyl), 127.4 (4-thienyl),
131.4 (7-benzothienyl), 138.2 (3a-benzothienyl), 140.5 (7a-
benzothienyl), and 141.1 (3-thienyl); IR (neat): 3102, 1578,
3
121.6, 124.2, 125.1, 127.2, 127.4, 139.4, and 140.5.
4-Bromo-7-iodobenzo[b]thiophene (14).
To a solution
of 1a (100 mg, 0.342 mmol) in Et2O (2.0 mL) was added
0.36 mmol of n-BuLi (1.57 M solution in hexane, 0.23 mL) at
¹78 °C under N2. The reaction mixture was stirred at ¹78 °C
for 30 min, and then 1,2-diiodoethane (96.4 mg, 0.376 mmol) in
Et2O (1.0 mL) was added at ¹78 °C. The reaction mixture was
allowed to warm to room temperature and stirred for 2 h. Upon
completion, the mixture was poured into saturated aqueous
NH4Cl, and extracted with Et2O. The organic layer was washed
with brine and dried over MgSO4. The filtrate was concentrated
under reduced pressure, and the residue was treated with silica
gel column chromatography to give 96.2 mg (0.284 mmol, 83%
1458 (Lit.7 1460), 1389, 1339, 1221, 1204, 1098, 1048, 857
¹1
(Lit. 860), 803, 777 (Lit. 775), 700, and 652 cm
.
4,7-Di(2-thienyl)benzo[b]thiophene (17). A mixture of 1a
(86.0 mg, 0.295 mmol), 2-(2-thienyl)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (166 mg, 0.719 mmol), K2CO3 (204 mg, 1.48
mmol) and tetrakis(triphenylphosphine)palladium (17.0 mg,
0.015 mmol) in 1,4-dioxane (3.4 mL) and water (0.7 mL) was
stirred at 80 °C for 16 h under N2. Upon completion, the
mixture was poured into water, and extracted with Et2O. The
organic layer was washed with brine and dried over MgSO4.
The filtrate was concentrated under reduced pressure, and
purified by silica gel column chromatography to give 70.6 mg
(0.237 mmol, 80% yield) of 17: Pale yellow solid, mp 71-73 °C
1
yield) of 14: Colorless needles, mp 77-78 °C; H NMR (400
3
3
MHz, CDCl3): ¤ 7.28 (1H, d, J = 8.0 Hz), 7.53 (1H, d, J =
3
3
8.0 Hz), 7.59 (1H, d, J = 5.5 Hz), and 7.72 (1H, d, J = 5.5
Hz); 13C{1H} NMR (100 MHz, CDCl3): ¤ 85.8, 117.8, 125.8,
127.6, 128.7, 134.4, 138.8, and 147.0; IR (KBr): 1431, 1347,
1312, 1183, 1103, 1088, 1065, 891, 826, 806, 797, 754,
and 687 cm¹1. HRMS (EI): Found: m/z 337.8257. Calcd
for C8H4BrIS: 337.8262. Anal. Found: C, 28.57; H, 1.23%.
Calcd for C8H4BrIS: C, 28.34; H, 1.19%.
1
(Lit.8 73 °C); H NMR (400 MHz, CDCl3): ¤ 7.13-7.22 (3H,
m), 7.33 (1H, dd, J = 3.6 and 1.1 Hz, thienyl), 7.38 (1H,
dd, J = 5.1 and 1.0 Hz, thienyl), 7.50 (1H, d, 3J = 5.6 Hz,
benzothienyl), 7.51 (1H, d, 3J = 7.7 Hz, benzothienyl), 7.56
3
(1H, d, J = 7.7 Hz, benzothienyl), 7.62 (1H, dd, J = 3.6 and
3
4-Bromo-7-(3-thienyl)benzo[b]thiophene (15).
Com-
1.1 Hz, thienyl), and 7.80 (1H, d, J = 5.6 Hz, benzothienyl);
pound 14 (155 mg, 0.456 mmol), 3-thienylboronic acid (64.2
mg, 0.502 mmol), K2CO3 (315 mg, 2.28 mmol) and tetrakis-
(triphenylphosphine)palladium (10.5 mg, 9.12 ¯mol) in THF
(3.8 mL) and water (0.8 mL) was stirred at 45 °C for 12 h under
N2. Upon completion, the mixture was poured into water, and
extracted with Et2O. The organic layer was washed with brine
and dried over MgSO4. The filtrate was concentrated under
reduced pressure, and purified by silica gel column chroma-
tography to give 63.4 mg (0.215 mmol, 47% yield) of 15:
13C{1H} NMR (100 MHz, CDCl3): ¤ 123.9, 124.1, 125.47,
125.50, 125.6, 125.7, 126.1, 127.1, 127.6, 127.8, 129.0, 129.6,
138.3, 138.6, 142.3, and 142.4; IR (neat): 3104, 1460, 1426,
1370, 1354, 1346, 1331, 1269, 1213, 1183, 1103, 1080, 1048,
990, 889, 882, 847, 814 (br), 779, and 690 cm¹1. (Lit.8 1458,
850, 825, 810, 690 cm¹1). HRMS (EI): Found: m/z 297.9942.
Calcd for C16H10S3: 297.9945.
4,7-Di(3-thienyl)benzo[b]thiophene (18). A mixture of
1a (150 mg, 0.524 mmol), 3-thienylboronic acid (161 mg,
1.26 mmol), K2CO3 (355 mg, 2.43 mmol), and tetrakis(tri-
phenylphosphine)palladium (29.7 mg, 0.0262 mmol) in 1,4-
dioxane (7 mL) and water (1.4 mL) was stirred at 80 °C for 15 h
under N2. Upon completion, the mixture was poured into water,
and extracted with CH2Cl2. The organic layer was washed with
brine and dried over MgSO4. The filtrate was concentrated
under reduced pressure, and purified by silica gel column
chromatography to give 147 mg (0.492 mmol, 94% yield) of
18: Colorless powder, mp 122-123 °C; 1H NMR (400 MHz,
CDCl3): ¤ 7.40 (1H, dd, J = 5.0 and 1.4 Hz, thienyl), 7.46-7.50
(4H, m, thienyl + benzothienyl), 7.50 (1H, d, 3J = 7.0 Hz,
benzothienyl), 7.52 (1H, d, 3J = 7.0 Hz, benzothienyl), 7.56
(1H, dd, J = 5.0 and 1.4 Hz, thienyl), 7.64 (1H, d, 3J = 5.6 Hz,
benzothienyl), and 7.76 (1H, dd, J = 3.0 and 1.4 Hz, thienyl);
13C NMR (100 MHz, CDCl3): ¤ 122.6, 122.7, 123.8, 123.9,
125.1, 125.7, 126.0, 126.6, 127.5, 128.5, 130.4, 131.4, 138.5,
139.0, 140.9, and 141.4; IR (KBr): 3098, 1456, 1362, 1335,
1293, 1202, 1186, 1150, 1103, 1080, 1051, 912, 855, 785, 770,
704, and 664 cm¹1. HRMS (EI): Found: m/z 297.9940. Calcd
for C16H10S3: 297.9945. Anal. Found: C, 64.15; H, 3.57%.
Calcd for C16H10S3: C, 64.39; H, 3.38%.
1
Colorless needles, mp 98-99 °C; H NMR (400 MHz, CDCl3):
3
¤ 7.32 (1H, d, J = 7.9 Hz, benzothienyl), 7.46-7.50 (2H, m,
4- and 5-thienyl), 7.55 (1H, d, 3J = 5.8 Hz, benzothienyl), 7.56
3
3
(1H, d, J = 5.8 Hz, benzothienyl), 7.60 (1H, d, J = 7.9 Hz,
benzothienyl), and 7.71 (1H, dd, J = 2.8 and 1.5 Hz, 2-thienyl);
13C{1H} NMR (100 MHz, CDCl3): ¤ 116.3, 122.8, 124.6,
124.9, 126.3, 127.3, 127.5, 128.0, 130.7, 139.0, 139.9, and
140.2; IR (KBr): 2361, 1449, 1335, 1200, 1096, 1082, 858,
826, 776, 758, 691, and 652 cm¹1. HRMS (EI): Found: m/z
293.9167. Calcd for C12H7BrS2: 293.9173.
7-(3-Thienyl)benzo[b]thiophene (16). To a solution of 15
(35.5 mg, 0.120 mmol) in THF (1.2 mL) was added n-BuLi
(0.0815 mL, 1.26 mmol) in Et2O (0.5 mL) at ¹78 °C under N2.
The reaction mixture was stirred at ¹78 °C for 30 min, and then
the mixture was quenched with saturated aqueous NH4Cl, and
extracted with Et2O. The organic layer was washed with brine
and dried over MgSO4. The filtrate was concentrated under
reduced pressure, and purified by silica gel column chroma-
tography to give 19.8 mg (0.0915 mmol, 76% yield) of 16:
Colorless oil; 1H NMR (600 MHz, CDCl3): ¤ 7.42 (1H, d, 3J =
5.4 Hz, 3-benzothienyl), 7.45 (1H, t, 3J = 7.8 Hz, 5-benzo-
thienyl), 7.48 (1H, dd, J = 4.8 and 3.0 Hz, 5-thienyl), 7.49 (1H,
1-Bromo-4-{5-hexyl-2-[2-(triisopropylsilyl)ethynyl]-3-
thienyl}benzene (22). To a solution of 219d (1.25 g, 2.98
3
d, J = 5.4 Hz, 2-benzothienyl), 7.49-7.51 (1H, m, 6-benzo-

620
Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
Preparation of 4,7-Dibromobenzo[b]thiophene
mmol) in THF (30 mL) was added 3.7 mmol of LDA (6.3 mL
of a 0.58 M solution in THF) at ¹78 °C under N2. The resulting
mixture was stirred at ¹78 °C for 70 min. To the reaction
mixture was added 1-iodohexane (0.58 mL, 3.9 mmol) at
¹78 °C. The reaction mixture was allowed to warm to 50 °C
and stirred for 3 h. After cooling to room temperature, EtOAc
(ca. 200 mL) and water (ca. 200 mL) were added, the organic
phase was separated, washed with brine, and dried over
MgSO4. The solvent was removed under reduced pressure and
the residue was treated with a silica gel column chromato-
graphy (hexane) to give 1.27 g (2.52 mmol, 85% yield) of
stirred at 50 °C for 15 h under N2. After cooling to room
temperature, EtOAc (ca. 30 mL) and water (ca. 30 mL) were
added to the reaction mixture. The organic phase was separated,
washed with brine, and dried over MgSO4. The solvent was
removed under reduced pressure and the residue was treated
with silica gel column chromatography (hexane) to give 226
1
mg (0.533 mmol, 77% yield) of 24: Yellow oil; H NMR (400
MHz, CDCl3): ¤ 0.90 (3H, t, 3J = 7.0 Hz, Me), 1.31-1.40 (6H,
3
m, CH2), 1.66-1.74 (2H, m, CH2), 2.78 (2H, t, J = 7.4 Hz,
theinyl-CH2), 6.88 (1H, s, thienyl), 7.31-7.35 (3H, m, Ph),
3
7.43-7.45 (2H, m, Ph), 7.55 (2H, d, J = 8.6 Hz, phenyl), and
1
3
22: Colorless oil; H NMR (400 MHz, CDCl3): ¤ 0.89 (3H, t,
7.69 (2H, d, J = 8.6 Hz, phenyl); 13C{1H} NMR (100 MHz,
3J = 6.9 Hz, MeCH2), 1.10 (18H, br s, Me2C), 1.31 (4H, m,
CDCl3): ¤ 14.1 (Me), 22.5 (CH2), 28.7 (CH2), 30.2 (CH2), 31.3
(CH2), 31.5 (CH2), 83.4 (C¸C), 94.9 (C¸C), 115.6, 121.4,
123.0, 124.6, 128.2, 129.3, 131.1, 131.4, 134.5, 143.1, and
147.4; IR (neat): 2955, 2928, 2855, 2201 (C¸C), 1597, 1493,
1456, 1443, 1402, 1377, 1102, 1069, 1011, 912, 860, 824,
754, 689, and 515 cm¹1; MS (EI): m/z (rel intensity) 424
(M+ + 2; 100), 422 (M+; 94), 353 (M+ ¹ n-Pen + 2; 64),
351 (M+ ¹ n-Pen; 62), and 271 (M+ ¹ n-Pen ¹ Br ¹ 1; 25).
HRMS (EI): Found: m/z 422.0703. Calcd for C24H23BrS: M,
422.0704.
3
CH2 + CH2), 1.38 (3H, m, Me2CH), 1.67 (2H, quin, J = 7.4
3
Hz, thienyl-CH2CH2), 2.77 (2H, t, J = 7.4 Hz, thienyl-CH2),
6.83 (1H, s, 4-thienyl), 7.47 (2H, m, 3- and 5-phenyl), and 7.71
(2H, m, 2- and 6-phenyl); 13C{1H} NMR (150 MHz, CDCl3):
¤ 11.3 (Me2C), 14.1 (MeCH2), 18.6 (Me2C), 22.5 (CH2), 28.7
(CH2), 30.2 (CH2), 31.4 (CH2), 31.5 (CH2), 98.0 (C¸C), 99.8
(C¸C), 116.1 (2-thienyl), 121.3 (1-Ph), 124.3 (4-thienyl),
129.4 (3- and 5-Ph), 131.3 (2- and 6-Ph), 134.3 (4-Ph), 143.2
(3-thienyl), and 147.2 (5-thienyl); IR (neat): 2945, 2865, 2137
(C¸C), 1495, 1464, 1071, 1011, 997, 884, 822, 772, and
677 cm¹1; MS (EI): m/z (rel intensity) 504 (M+ + 2; 65), 502
(M+; 58), 461 (M+ ¹ i-Pr + 2; 100), and 459 (M+ ¹ i-Pr; 90).
HRMS (EI): Found: m/z 502.1723. Calcd for C27H39BrSSi:
M, 502.1725.
2-(4-{5-Hexyl-2-[2-(triisopropylsilyl)ethynyl]-3-thienyl}-
phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (25). To a
solution of 22 (176 mg, 0.349 mmol) in THF (3.5 mL) was
added 0.393 mmol of n-BuLi (1.57 M solution in hexane,
0.250 mL) at ¹78 °C under N2. To the resulting mixture was
added 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
(0.090 mL, 0.44 mmol) at ¹78 °C. The reaction mixture was
allowed to warm to room temperature, and stirred for 90 min.
To the resulting mixture were added water (ca. 50 mL) and
EtOAc (ca. 50 mL). The organic phase was separated, washed
with brine, and dried over MgSO4. The solvent was removed
under reduced pressure and the residue was treated with silica
gel column chromatography (hexane-EtOAc 1:0 to 1:0.1)
to give 80.9 mg (0.147 mmol, 42% yield) of 25: Colorless
1-Bromo-4-(5-hexyl-2-ethynyl-3-thienyl)benzene
(23).
To a solution of 22 (403 mg, 0.801 mmol) in THF (8 mL)
was added 0.88 mmol of tetrabutylammonium fluoride (1.0 M
solution in THF, 0.88 mL) at room temperature and the reaction
mixture was stirred at that temperature for 70 min under N2. To
the reaction mixture were added EtOAc (ca. 30 mL) and water
(ca. 30 mL). The organic phase was separated, washed with
brine, and dried over MgSO4. The solvent was removed under
reduced pressure, and the residue was treated with silica gel
column chromatography (hexane) to give 241 mg (0.694 mmol,
1
3
oil; H NMR (400 MHz, CDCl3): ¤ 0.89 (3H, t, J = 6.8 Hz,
MeCH2), 1.10 (21H, br s, i-Pr), 1.26-1.36 (18H, m, CH2 +
1
87% yield) of 23: Colorless oil; H NMR (400 MHz, CDCl3):
3
3
¤ 0.89 (3H, t, J = 6.9 Hz, MeCH2), 1.31-1.38 (6H, m, CH2),
OCMe2), 1.67 (2H, m, CH2), 2.77 (2H, t, J = 7.4 Hz, thienyl-
3
1.64-1.70 (2H, m, thienyl-CH2CH2), 2.78 (2H, t, J = 7.4 Hz,
CH2), 6.90 (1H, s, 4-thienyl), 7.80 (2H, d, 3J = 8.0 Hz, phenyl),
and 7.86 (2H, d, 3J = 8.0 Hz, phenyl); 13C{1H} NMR (150
MHz, CDCl3): ¤ 11.3 (Me2C), 14.1 (MeCH2), 18.7 (Me2C),
22.5 (CH2), 24.8 (OCMe2), 28.7 (CH2), 30.2 (CH2), 31.4 (CH2),
31.5 (CH2), 83.7 (OCMe2), 97.9 (C¸C), 100.1 (C¸C), 116.3,
124.7, 126.9, 134.8, 138.0, 144.0, and 146.8; IR (neat): 2957,
2865, 2137 (C¸C), 1611, 1559, 1541, 1271, 1213, 1146, 1075,
1021, 997, 963, 920, 884, 860, 830, 772, 747, 675, and
579 cm¹1. HRMS (ESI): Found: m/z 573.3360. Calcd for
C33H51BNaO2SSi: (M + Na)+, 573.3364.
thienyl-CH2), 3.39 (1H, S, C¸CH), 6.82 (1H, s, 4-thienyl),
7.52 (2H, d, 3J = 8.6 Hz, 3- and 5-phenyl), and 7.61 (2H,
d, 3J = 8.6 Hz, 2- and 6-phenyl); 13C{1H} NMR (150 MHz,
CDCl3): ¤ 14.1 (Me), 22.5 (CH2), 28.7 (CH2), 30.1 (CH2), 31.3
(CH2), 31.5 (CH2), 77.4 (C¸C), 83.1 (C¸C), 114.3 (2-thienyl),
121.6 (1-phenyl), 124.6 (4-thienyl), 129.3 (3- and 5-phenyl),
131.5 (2- and 6-phenyl), 134.1 (4-phenyl), 144.3 (3-thienyl),
and 147.7 (5-thienyl); IR (neat): 3301 (C¸CH), 2955, 2928,
2855, 2097 (C¸C), 1495, 1466, 1456, 1402, 1069, 1066, 864,
822, 658, 583, and 500 cm¹1; MS (EI): m/z (rel intensity)
348 (M+ + 2; 100), 346 (M+; 97), 277 (M+ ¹ n-Pen + 2; 99),
275 (M+ ¹ n-Pen; 96), and 195 (M+ ¹ n-Pen ¹ Br ¹ 1; 23).
HRMS (EI): Found: m/z 346.0381. Calcd for C18H19BrS: M,
346.0391.
2-{4-[5-Hexyl-2-(2-phenylethynyl)-3-thienyl]phenyl}-
4,4,5,5-tetramethyl-1,3,2-dioxaborolane (26). To a solution
of 24 (190 mg, 0.448 mmol) in THF (4.5 mL) was added 0.468
mmol of n-BuLi (1.67 M solution in hexane, 0.280 mL) at
¹78 °C under N2. The resulting mixture was stirred for 35 min.
To the solution was added 2-isopropoxy-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane (0.10 mL, 0.49 mmol) at ¹78 °C. The reac-
tion mixture was allowed to warm to room temperature, and
stirred for 10 h. EtOAc (ca. 50 mL) and water (ca. 50 mL) were
added to the mixture. The organic phase was separated, washed
1-Bromo-4-[5-hexyl-2-(2-phenylethynyl)-3-thienyl]ben-
zene (24). A mixture of 23 (241 mg, 0.694 mmol), iodo-
benzene (0.090 mL, 0.81 mmol), dichlorobis(triphenylphos-
phine)palladium(II) (9.9 mg, 0.014 mmol), CuI (8.1 mg, 0.042
mmol), and N,N-diisopropylamine (1 mL) in THF (7 mL) was

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
621
with brine, and dried over MgSO4. The solvent was removed
under reduced pressure to give 203 mg (0.432 mmol, 96%
Me), 7.21 (1H, d, 4J = 8.1 Hz, benzothienyl), 7.38 (1H, q,
4J = 1.2 Hz, 3-benzothienyl), and 7.43 (1H, d, 4J = 8.1 Hz,
benzothienyl); 13C{1H} NMR (100 MHz, CDCl3): ¤ 16.3
(benzothienyl-Me), 85.3, 116.4, 123.4, 128.5, 133.3, 139.4,
142.6, and 146.4; IR (KBr): 3064, 2970, 2949, 2912, 2844,
1847, 1598, 1556, 1513, 1431, 1352, 1342, 1309, 1200, 1183,
1117, 1102, 1077, 896, 813, 795, 762, 716, 674, 646, 525,
and 506 cm¹1. HRMS (EI): Found: m/z 351.8415. Calcd for
C9H6BrIS: M, 351.8418.
1
yield) of 26: Yellow oil; H NMR (400 MHz, CDCl3): ¤ 0.90
(3H, t, 3J = 6.9 Hz, MeCH2), 1.32-1.42 (18H, m, CH2 +
3
OCMe2), 1.67-1.75 (2H, m, CH2), 2.81 (2H, t, J = 7.6 Hz,
thienyl-CH2), 6.95 (1H, s, thienyl), 7.31-7.34 (3H, m, Ph),
3
7.45-7.47 (2H, m, Ph), 7.85 (2H, d, J = 8.3 Hz, phenyl), and
3
7.88 (2H, d, J = 8.3 Hz, phenyl); 13C{1H} NMR (100 MHz,
CDCl3): ¤ 14.0 (MeCH2), 22.5 (CH2), 24.8 (OCMe2), 28.7
(CH2), 30.2 (CH2), 31.3 (CH2), 31.5 (CH2), 83.7 (C¸C), 83.7
(OCMe2), 94.7 (C¸C), 115.8, 123.2, 125.0, 127.0, 128.1,
131.1, 134.8, 138.3, 144.2, and 147.1; IR (neat): 2930, 2857,
2201 (C¸C), 1609, 1559, 1541, 1495, 1456, 1399, 1362, 1323,
1271, 1213, 1144, 1096, 1071, 1021, 963, 858, 830, 754, 691,
662, 652, and 521 cm¹1. HRMS (ESI): Found: m/z 493.2391.
Calcd for C30H35BNaO2S: (M + Na)+, 493.2343.
Cross Coupling Reaction of 12 with 25 (1 molar equiva-
lent). A mixture of 12 (79.4 mg, 0.259 mmol), 25 (141 mg,
0.256 mmol), tetrakis(triphenylphosphine)palladium (9.2 mg,
0.0079 mmol), K2CO3 (179 mg, 1.30 mmol), 1,4-dioxane (2.3
mL), and water (1.2 mL) was heated at 90 °C for 13 h under
N2. After cooling to room temperature, CHCl3 and water were
added to the reaction mixture. The organic phase was separated,
washed with brine, and dried over MgSO4. The solvent was
removed under reduced pressure, the residue was treated with
silica gel column chromatography (hexane to hexane-EtOAc
30:1) to give 43.2 mg (0.0435 mmol, 17% yield) of 19a and
87.1 mg (0.134 mmol, 52% yield) of an isomeric mixture
of 27 and 28 (1.0:0.43). 27 (major signals in the mixture):
1H NMR (400 MHz, CDCl3): ¤ 0.90 (3H, t, 3J = 6.9 Hz,
MeCH2), 1.12 (21H, s, i-Pr), 1.32-1.43 (6H, m, CH2), 1.66-
1.74 (2H, m, CH2), 2.58 (3H, d, 4J = 1.2 Hz, benzothienyl-Me),
4-Bromo-7-{4-[5-hexyl-2-(triisopropylsilylethynyl)-3-thi-
enyl]phenyl}-2-methylbenzo[b]thiophene (28). A mixture of
25 (343 mg, 0.622 mmol), 29 (222 mg, 0.628 mmol), tetrakis-
(triphenylphosphine)palladium (29.1 mg, 0.0252 mmol), K2CO3
(435 mg, 3.15 mmol), 1,4-dioxane (5 mL), and water (2 mL)
was heated under nitrogen at 80 °C for 46 h under N2. After
cooling to room temperature, EtOAc and water were added to
the reaction mixture. The organic phase was separated, washed
with brine, and dried over MgSO4. The solvent was removed
under reduced pressure, the residue was treated with silica gel
column chromatography (hexane) to give 322 mg (0.496 mmol,
3
2.80 (2H, t, J = 7.5 Hz, thienyl-CH2), 6.93 (1H, s, 4-thienyl),
7.20 (1H, d, 4J = 7.8 Hz, benzothienyl), 7.21 (1H, br s, 3-
benzothienyl), 7.48 (1H, d, 4J = 7.8 Hz, benzothienyl), 7.51
(2H, d, 4J = 8.3 Hz, phenyl), and 7.93 (2H, d, 4J = 8.3 Hz,
phenyl). The isomeric mixture was subjected to a further cross
coupling reaction: To the mixture of 27 and 28 (80.7 mg,
0.124 mmol) were added 25 (68.3 mg, 0.124 mmol), tetrakis-
(triphenylphosphine)palladium (4.0 mg, 0.0037 mmol), K2CO3
(92.4 mg, 0.669 mmol), 1,4-dioxane (1.8 mL), and water (0.8
mL). The resulting mixture was heated at 90 °C for 40 h under
N2. After cooling to room temperature, CHCl3 and water were
added to the reaction mixture. The organic phase was separated,
washed with brine, and dried over MgSO4. The solvent was
removed under reduced pressure and the residue was succes-
sively treated with silica gel column chromatography (hexane-
EtOAc 30:1) and gel permeation chromatography to give 81.0
mg of 19a (0.0815 mmol, 66% yield).
1
80% yield) of 28: Colorless oil; H NMR (400 MHz, CDCl3):
3
¤ 0.90 (3H, t, J = 6.9 Hz, MeCH2), 1.11 (21H, s, i-Pr), 1.32-
1.40 (6H, m, CH2), 1.66-1.73 (2H, m, CH2), 2.60 (3H, d, 4J =
1.2 Hz, benzothienyl-Me), 2.80 (2H, t, 3J = 7.5 Hz, thienyl-
4
CH2), 6.93 (1H, s, 4-thienyl), 7.16 (1H, d, J = 7.9 Hz, benzo-
thienyl), 7.22 (1H, q, 4J = 1.2 Hz, 3-benzothienyl), 7.57 (1H, d,
4
4J = 7.9 Hz, benzothienyl), 7.66 (2H, d, J = 8.5 Hz, phenyl),
and 7.94 (2H, d, 4J = 8.5 Hz, phenyl); 13C{1H} NMR (100
MHz, CDCl3): ¤ 11.4 (Me2C), 14.1 (MeCH2), 16.0 (benzo-
thienyl-Me), 18.7 (Me2C), 22.6 (CH2), 28.7 (CH2), 30.2 (CH2),
31.3 (CH2), 31.5 (CH2), 97.6 (C¸C), 100.3 (C¸C), 115.2,
116.0, 122.4, 124.2, 124.5, 127.8, 127.9, 128.0, 128.2, 135.2,
138.7, 139.0, 140.4, 142.4, 144.0, and 146.9; IR (neat): 2928,
2863, 2135 (C¸C), 1512, 1460, 1346, 1203, 1118, 1081, 1017,
995, 919, 882, 811, 771, 677, 577, and 505 cm¹1. HRMS (ESI):
Found: m/z 671.1804. Calcd for C36H45BrNaS2Si: (M + Na)+,
671.1808.
4,7-Bis{4-[5-hexyl-2-(triisopropylsilylethynyl)-3-thienyl]-
phenyl}-2-methylbenzo[b]thiophene (19a).
A mixture of
4-Bromo-7-iodo-2-methylbenzo[b]thiophene (29). To a
solution of 12 (219 mg, 0.716 mmol) in THF (5 mL) was added
0.75 mmol of n-BuLi (1.67 M solution in hexane, 0.45 mL) at
¹78 °C under N2. The resulting mixture was stirred at ¹78 °C
for 30 min and 1,2-diiodoethane (243 mg, 0.862 mmol) in
THF (2 mL) was added at ¹78 °C. The resulting mixture was
allowed to warm to room temperature and stirred for 2 h. To the
reaction mixture were added EtOAc and saturated aqueous
NH4Cl and the resulting mixture was treated with saturated
aqueous Na2S2O3 solution. The organic phase was separated,
washed with brine, and dried over MgSO4. The filtrate was
concentrated under reduced pressure, and purified by silica gel
column chromatography (hexane) to give 234 mg (0.663 mmol,
93% yield) of 29: Colorless powder, mp 113-114 °C; 1H NMR
12 (19.3 mg, 0.0631 mmol), 25 (81.4 mg, 0.148 mmol), tetrakis-
(triphenylphosphine)palladium (3.5 mg, 3.0 ¯mol), and K2CO3
(82.7 mg, 0.598 mmol) in 1,4-dioxane (1.8 mL) and water (1.0
mL) was stirred at 90 °C for 13 h under N2. After cooling to
room temperature, CHCl3 and water were added to the reaction
mixture. The organic layer was separated, washed with brine,
and dried over MgSO4. The filtrate was concentrated under
reduced pressure and the residue was treated with silica gel
column chromatography (hexane-EtOAc 40:1) to give a crude
product, which was purified by successive silica gel column
chromatography (hexane-EtOAc 100:1) to give 36.5 mg
(0.0367 mmol, 58% yield) of 19a: Colorless solid, mp 46-
48 °C; 1H NMR (400 MHz, CDCl3): ¤ 0.91 (6H, t, 3J = 6.9 Hz,
MeCH2), 1.13 (42H, s, i-Pr), 1.32-1.41 (12H, m, CH2), 1.67-
1.74 (4H, m, CH2), 2.57 (3H, d, 4J = 1.2 Hz, benzothienyl-Me),
4
(400 MHz, CDCl3): ¤ 2.60 (3H, d, J = 1.2 Hz, benzothienyl-

622
Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
Preparation of 4,7-Dibromobenzo[b]thiophene
3
2.81 (4H, t, J = 7.6 Hz, thienyl-CH2), 6.96 (2H, s, 4-thienyl),
7.21 (1H, q, 4J = 1.2 Hz, 3-benzothienyl), 7.39 (1H, d, 3J = 7.6
Hz, benzothienyl), 7.43 (1H, d, 3J = 7.6 Hz, benzothienyl),
7.60 (2H, d, 3J = 8.3 Hz, phenyl), 7.76 (2H, d, J = 8.3 Hz,
was treated with silica gel column chromatography (hexane)
to give 257 mg (0.0346 mmol, 84% yield) of 31: Yellow
1
3
oil; H NMR (400 MHz, CDCl3): ¤ 0.95 (3H, t, J = 6.0 Hz,
CH2Me), 1.16 (21H, s, CHMe2), 1.23 (21H, s, CHMe2),
1.31-1.48 (6H, m, CH2), 1.73 (2H, quin, 3J = 7.4 Hz, thi-
enylCH2CH2), 2.82 (2H, t, 3J = 7.5 Hz, thienylCH2), 6.94 (1H,
s, 4-thienyl), 7.23 (1H, d, 3J = 5.2 Hz, thienothienyl), 7.40
3
phenyl), 7.96 (2H, d, J = 8.3 Hz, phenyl), and 7.98 (2H, d,
3J = 8.3 Hz, phenyl); 13C{1H} NMR (100 MHz, CDCl3): ¤ 11.4
(Me2C), 14.1 (MeCH2), 16.1 (benzothienyl-Me), 18.7 (Me2C),
22.6 (CH2), 28.7 (CH2), 30.3 (CH2), 31.4 (CH2), 31.6 (CH2),
97.4 (C¸C), 97.6 (C¸C), 100.3 (C¸C), 100.4 (C¸C), 115.9,
116.0, 121.4, 123.7, 124.7, 125.4, 127.9, 128.0, 128.2, 129.0,
134.5, 135.0, 135.1, 135.6, 139.2, 139.3, 139.6, 140.0, 141.3,
144.2, 144.3, 146.8, and 146.9; UV-vis (CH2Cl2): 264 (log ¾
4.65), 316 (4.63), and 340 nm (sh, 4.60); IR (neat): 2928, 2863,
3
3
(1H, d, J = 5.2 Hz, thienothienyl), 7.91 (2H, d, J = 7.9 Hz,
phenyl), and 8.07 (2H, d, 3J = 7.9 Hz, phenyl); 13C{1H}
NMR (100 MHz, CDCl3): ¤ 11.3 (CHMe2), 11.4 (CHMe2),
14.1 (CH2Me), 18.68 (CHMe2), 18.72 (CHMe2), 22.6 (CH2),
28.8 (CH2), 30.3 (CH2), 31.4 (CH2), 31.6 (CH2), 97.6 (C¸C),
97.9 (C¸C), 100.2 (C¸C), 100.6 (C¸C), 110.9, 116.2, 119.6,
124.6, 127.18 (phenyl), 127.22, 128.0 (phenyl), 133.2, 135.3,
135.4, 143.8, 143.9, 147.0, and 147.5; IR (neat): 2940, 2890,
2864, 2136 (C¸C), 1520, 1462, 1382, 1357, 1242, 1175, 1062,
1016, 995, 955, 911, 882, 830, 772, 735, 711, 668, and
504 cm¹1. Found: m/z 765.3443. Calcd for C44H62NaS3Si2:
(M + Na)+, 765.3444.
2135 (C¸C), 1519, 1463, 1380, 1260, 1173, 1116, 1073, 1044,
1016, 995, 919, 882, 818, 771, 676, 578, 520, and 503 cm
HRMS (ESI): Found: m/z 1015.5156. Calcd for C63H84NaS3-
Si2: (M + Na)+, 1015.5166.
¹1
.
4-{4-[5-Hexyl-2-(phenylethynyl)-3-thienyl]phenyl}-7-{4-
[5-hexyl-2-(triisopropylsilylethynyl)-3-thienyl]phenyl}-2-
methylbenzo[b]thiophene (19b). A mixture of 26 (64.1 mg,
0.136 mmol), 28 (85.6 mg, 0.132 mmol), tetrakis(triphenyl-
phosphine)palladium (5.8 mg, 0.0050 mmol), K2CO3 (90.4
mg, 0.654 mmol), 1,4-dioxane (1.8 mL), and water (0.8 mL)
was heated at 90 °C for 13 h under N2. After cooling to room
temperature, EtOAc and water were added to the reaction
mixture. The organic phase was separated, washed with brine,
and dried over MgSO4. The solvent was removed under
reduced pressure and the residue was treated with silica
gel column chromatography (hexane-EtOAc, 1:0 to 30:1) to
give 107.3 mg (0.118 mmol, 89% yield) of 19b: Yellow oil;
1H NMR (400 MHz, CDCl3): ¤ 0.97-0.99 (6H, m, MeCH2),
1.20 (21H, s, i-Pr), 1.38-1.47 (12H, m, CH2), 1.74-1.80 (4H,
Compound 20. To a solution of 31 (163.1 mg, 0.219 mmol)
in THF (2 mL) was added 0.25 mmol of n-BuLi (1.65 M
solution in hexane, 0.15 mL) at ¹78 °C under N2 and the
resulting mixture was stirred for 1 h. To the mixture was added
2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.060
mL, 0.29 mmol) at ¹78 °C. The reaction mixture was allowed
to warm to room temperature, and stirred for 3 h. To the
resulting mixture were added water (ca. 30 mL) and EtOAc
(ca. 30 mL). The organic phase was separated, washed with
brine, and dried over MgSO4. The solvent was removed under
reduced pressure and the residue was treated with a short silica
gel column chromatography (EtOAc) to give 184.9 mg (0.213
1
mmol) of 32 in 97% yield. 32: H NMR (400 MHz, CDCl3):
4
3
m, CH2), 2.62 (3H, d, J = 1.1 Hz, benzothienyl-Me), 2.83-
¤ 0.90 (3H, t, J = 6.6 Hz, CH2Me), 1.10 (21H, s, CHMe2),
2.90 (4H, m, thienyl-CH2), 7.00 (1H, s, 4-thienyl), 7.05 (1H, s,
4¤-thienyl), 7.31 (1H, q, 4J = 1.1 Hz, 3-benzothienyl), 7.34-
7.39 (3H, m, Ph), 7.44 (1H, d, 3J = 7.5 Hz, benzothienyl),
1.18 (21H, s, CHMe2), 1.27-1.34 (6H, m, CH2), 1.38 (12H,
3
s, CMe2), 1.69 (2H, quin, J = 7.5 Hz, thienylCH2CH2), 2.79
3
(2H, t, J = 7.5 Hz, thienylCH2), 6.90 (1H, s, thienyl), 7.71
3
3
7.50-7.55 (3H, m, Ph + benzothienyl), 7.73 (2H, d, J = 8.3
(1H, s, thienothienyl), 7.85 (2H, d, J = 8.6 Hz, phenyl), and
3
Hz, phenyl), 7.82 (2H, d, J = 8.3 Hz, phenyl), and 8.02-8.05
8.02 (2H, d, 3J = 8.6 Hz, phenyl). This procedure was repeated,
the products were combined, and used in Suzuki-Miyaura
reaction: A mixture of 32 (263.5 mg, 0.303 mmol), 29 (37.3
mg, 0.106 mmol), 2-dicyclohexylphosphino-2¤,6¤-dimethoxy-
biphenyl (10.3 mg, 0.0251 mmol), palladium(II) aceate (1.9 mg,
0.0084 mmol), K2CO3 (142.3 mg, 1.03 mmol), in THF (3 mL)
was heated at 50 °C for 2 days under N2. After cooling to room
temperature, CHCl3 and water were added to the reaction
mixture. The organic phase was separated, washed with brine,
and dried over MgSO4. The solvent was removed under
reduced pressure. Successive treatment of the residue with
silica gel column chromatography (hexane-EtOAc) and gel
permeation column chromatography gave 33.3 mg of 20
(crude) and 146.3 mg (0.197 mmol, 65% yield) of 31. Recrys-
tallization of the crude product 20 from hexane followed by a
short silica gel column chromatographic treatment (hexane-
CH2Cl2 15:1) gave 9.0 mg (0.0055 mmol, 5% yield) of 20:
Yellow solid, mp 242-245 °C; 1H NMR (400 MHz, CDCl3):
(4H, m, phenyl); 13C{1H} NMR (100 MHz, CDCl3): ¤ 11.4
(Me2C), 14.1 (MeCH2), 16.1 (benzothienyl-Me), 18.7 (Me2C),
22.5 (CH2), 22.6 (CH2), 28.7 (CH2), 28.8 (CH2), 30.2 (CH2),
30.3 (CH2), 31.3 (CH2), 31.4 (CH2), 31.5 (CH2 © 2), 84.0
(C¸C), 94.7 (C¸C), 97.6 (C¸C), 100.3 (C¸C), 115.4, 116.0,
121.4, 123.4, 123.7, 124.7, 125.0, 125.5, 127.9, 128.0, 128.1,
128.2, 128.3, 129.1, 131.1, 134.6, 135.0, 135.1, 135.5, 139.2,
139.3, 139.6, 140.1, 141.3, 144.1, 144.2, 146.9, and 147.3;
UV-vis (CH2Cl2): 265 (log ¾ 4.71) and 322 nm (4.75); IR
(neat): 2927, 2862, 2198 (C¸C), 2135 (C¸C), 1597, 1518,
1468, 1378, 1200, 1119, 1071, 1044, 1016, 996, 909, 882, 819,
771, 754, 677, 538, and 503 cm¹1. HRMS (ESI): Found: m/z
935.4145. Calcd for C60H68NaS3Si: (M + Na)+, 935.4137.
Compound 31. A mixture of 22 (51.0 mg, 0.498 mmol), 30
(184 mg, 0.412 mmol), tetrakis(triphenylphosphine)palladium
(11.4 mg, 0.00986 mmol), K2CO3 (348 mg, 2.52 mmol), toluene
(4 mL), THF (4 mL), and water (3 mL) was heated at 80 °C for
14 h under N2. After cooling to room temperature, CHCl3 and
water were added to the reaction mixture. The organic phase
was separated, washed with brine, and dried over MgSO4. The
solvent was removed under reduced pressure and the residue
3
¤ 0.91 (6H, t, J = 6.5 Hz, CH2Me), 1.12 (42H, s, CHMe2),
1.20 (42H, m, CHMe2), 1.33-1.41 (12H, m, CH2), 1.66-1.74
(4H, m, CH2), 2.66 (3H, s, benzothienyl-Me), 2.80 (4H, t,
3J = 7.5 Hz, thienylCH2), 6.90 (2H, s, 4-thienyl), 7.44 (1H,

T. Yamamoto et al.
Bull. Chem. Soc. Jpn. Vol. 85, No. 5 (2012)
623
2007, 70, 279.
a) A. Bugge, Acta Chem. Scand. 1969, 23, 2704. b) Y.
Mazaki, K. Kobayashi, Tetrahedron Lett. 1989, 30, 3315. c) L. S.
Fuller, B. Iddon, K. A. Smith, J. Chem. Soc., Perkin Trans. 1 1997,
3465.
s, thienothienyl), 7.51 (1H, br s, 3-benzothienyl), 7.53-
7.58 (2H, m, benzothienyl), 7.74 (1H, s, thienothienyl’), 7.87
(4H, d, 3J = 8.1 Hz, phenyl), and 8.04 (4H, d, 3J = 8.1 Hz,
phenyl); 13C{1H} NMR (100 MHz, CDCl3): ¤ 11.3 (CHMe2),
11.4 (CHMe2), 14.1 (CH2Me), 16.3 (benzothienyl-Me), 18.7
(CHMe2), 18.8 (CHMe2), 22.6 (CH2), 28.8 (CH2), 30.3 (CH2),
31.4 (CH2), 31.6 (CH2), 97.8 (C¸C), 98.0 (C¸C), 100.1
(C¸C), 100.4 (C¸C), 111.0, 111.1, 116.2, 118.0, 118.5, 121.5,
123.4, 124.6, 125.9, 127.2, 127.2, 128.0, 128.9, 129.0, 133.0,
133.1, 135.5, 135.5, 135.7, 135.9, 138.4, 139.2, 142.3, 143.3,
143.6, 143.9, 144.2, 144.5, 147.0, 147.1, and 147.4; UV-vis
(CH2Cl2): 243 (log ¾, 4.65), 302 (4.55), and 407 nm (4.85);
IR (neat): 2940, 2890, 2863, 2134 (C¸C), 1519, 1461, 1381,
1173, 1062, 995, 956, 918, 882, 829, 771, 711, 677, 578, 503,
and 459 cm¹1. Found: m/z 1651.7030 Calcd for C97H128NaS7-
Si4: (M + Na)+, 1651.7045.
3
4
For some recent reports on syntheses of benzo[b]thio-
phenes, see: a) I. Nakamura, T. Sato, Y. Yamamoto, Angew. Chem.,
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Brion, M. Alami, Eur. J. Org. Chem. 2010, 4492. g) S.-M. Yang,
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This work was supported in part by Grants-in-Aid for
Scientific Research (No. 20550030) from the Ministry of
Education, Culture, Sports, Science and Technology. The
authors thank Associate Prof. Itaru Nakamura, Tohoku Uni-
versity, for discussion.
5
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