Metal-free oxidative coupling reactions via ω-iodonium intermediates: The efficient synthesis of bithiophenes using hypervalent iodine reagents

Article abstract of DOI:10.1002/ejoc.201100969

The direct oxidative biaryl coupling reaction is an attractive tool for environmentally benign green chemistry. A novel direct method for the synthesis of bithiophene using a hypervalent iodine reagent has been developed. The reaction mechanism has also been investigated, casting light on the reaction intermediate and revealing the reactivity with iodonium salts.

Full text of DOI:10.1002/ejoc.201100969

FULL PAPER
DOI: 10.1002/ejoc.201100969
Metal-Free Oxidative Coupling Reactions via σ-Iodonium Intermediates: The
Efficient Synthesis of Bithiophenes Using Hypervalent Iodine Reagents
Koji Morimoto,[a] Tomofumi Nakae,[a] Nobutaka Yamaoka,[a] Toshifumi Dohi,[a] and
Yasuyuki Kita*[a]
Keywords: Iodine / Cross-coupling / Biaryls / Sulfur heterocycles / Oligomerization
The direct oxidative biaryl coupling reaction is an attractive
tool for environmentally benign green chemistry. A novel di-
rect method for the synthesis of bithiophene using a hyper-
valent iodine reagent has been developed. The reaction
mechanism has also been investigated, casting light on the
reaction intermediate and revealing the reactivity with
iodonium salts.
ization or polymerization of thiophenes.[5] Recently, Mori
and co-workers reported the palladium-catalyzed oxidative
coupling reaction of 2-substituted thiophenes using stoi-
chiometric silver fluoride as the terminal oxidant.[6]
Introduction
Oligo- and polythiophene derivatives have gained re-
cognition as important materials due to their useful physi-
cal properties such as electrical conductivity and electrolu-
minescence.[1] 2,2Ј-Bithiophenes are one of the most impor-
tant classes of compounds for synthesizing oligo- and poly-
thiophenes because they polymerize under mild conditions
due to their lower oxidation potential relative to thiophene
and predominantly yield a higher-quality α-linked polymer
compared with that prepared from thiophene.[1b] Therefore
there have been a large number of reports on the synthesis
of 2,2Ј-bithiophenes, but these methodologies have been
limited to transition-metal-catalyzed coupling reactions,
namely carbon–carbon (C–C) coupling reactions performed
with Grignard (Kumada–Tamao), boron (Suzuki–Mi-
yaura), and zinc reagents (Negishi).[2,3] On the other hand,
the oxidative biaryl coupling reactions of thiophenes is a
very attractive and convenient straightforward route to bi-
thiophenes due to its operational simplicity by avoiding the
preparation of the corresponding halogenated and met-
alated thiophenes. However, to the best of our knowledge,
there have been no reports on the oxidative dimerization
of thiophenes due to the lower oxidation potential of the
bithiophenes relative to the corresponding thiophenes. That
is, the dimer, which is more easily oxidized than the mono-
mer, usually undergoes further coupling to afford the poly-
thiophene through successive reactions.[4] Therefore typical
oxidative coupling methods using electrochemical oxidation
or heavy-metal oxidants such as FeIII, TlIII, RuIII, and MoIII
have not been utilized for dimerization but for the oligomer-
Hypervalent iodine(III) reagents have received consider-
able attention as alternatives to toxic heavy-metal reagents
due to their mild oxidation abilities, low toxicity, and easy
handling.[7] Over the past decades, we have focused our at-
tention on a new, efficient, and mild oxidative transforma-
tion of electron-rich aromatic compounds and have devel-
oped the phenyliodine(III) bis(trifluoroacetate) (PIFA) in-
duced direct oxidative nucleophilic substitution of phenyl
ethers by various nucleophiles such as N3, OAc, α-dicar-
bonyl compounds, SAr, and SCN in 1,1,1,3,3,3-hexafluo-
ropropane-2-ol (HFIP).[8]
In addition, we have found that the activated PIFA/
BF3·Et2O and PIFA/TMSOTf are effective for the intra-
and intermolecular biaryl coupling reactions of phenyl
ethers and alkylarenes (Scheme 1).[9] These reactions would
proceed via the cation radical intermediate A and the bond
formation could oxidatively occur by the reaction of A with
[a] College of Pharmaceutical Sciences, Ritsumeikan University,
1-1-1 Nojihigashi, Kusatsu, Shiga 525-0058, Japan
Fax: +81-77-561-5829
E-mail: kita@ph.ritsumei.ac.jp
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201100969.
Scheme 1. Biaryl coupling reactions of phenyl ethers and alkyl-
arenes.
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Metal-Free Oxidative Coupling Reactions
nucleophiles or neutral molecules of the substrate to give
the corresponding coupling products. As part of our contin-
ued studies on the PIFA-induced biaryl coupling reaction
we have developed the biaryl coupling reactions of substi-
tuted thiophenes 3 and 5 by using PIFA activated by
BF3·Et2O or TMSOTf (Scheme 2).[10] However, these reac-
tions required an excessive amount of the starting materials
at low temperature, see reaction (1), and the resulting cou-
pling products were obtained as a mixture of regioisomers
in low yields, see reaction (2).
Results and Discussion
Based on our previous results concerning the oxidative
biaryl coupling reactions of phenyl ethers and alkylarenes,
we first examined the coupling reaction of 3,4-dihexylthio-
phene (3a) with PIFA and a Lewis acid such as BF3·Et2O or
TMSOTf in dichloromethane at a low temperature (Table 1,
entries 1 and 2).[8] However, both BF3·Et2O and TMSOTf
were ineffective, producing only trace amounts of the cou-
pling product 4a, which was detected by TLC and GC
along with unreacted starting material 3a. On the other
hand, the use of bromotrimethylsilane (TMSBr) produced
a small amount of the coupling product 4a, whereas the
previously reported coupling reaction of pyrroles[13]
smoothly proceeded under the same reaction conditions
(entry 3). To improve the yield of the desired coupling prod-
uct 4a, a variety of solvents and temperatures were evalu-
ated. An earlier study by our group has shown that a fluoro
alcohol can enhance the reactivity of the hypervalent iodine
reagent towards thiophenes.[8b,14] Based on these studies, we
attempted the coupling reaction in a fluoro alcohol and
found that the use of TMSBr in HFIP increased the reactiv-
ity, producing the coupling product 4a in good yield (en-
try 6). Other ordinary organic solvents, such as toluene, di-
ethyl ether, DME, dioxane, dichloromethane, and another
fluoro alcohol CF3CH2OH, were less effective than HFIP.
Scheme 2. Biaryl coupling reactions of 3-substituted thiophenes
using hypervalent iodine reagent.
Table 1. Screening of Lewis acids and solvents in the coupling reac-
tion, see reaction (3).[a]
Recently, our research group has been involved in the
development of the hypervalent iodine(III)-induced cross-
coupling reactions of heteroaromatic compounds with vari-
ous arenes.[11] For these processes, the experimental data
revealed the involvement of iodonium(III) intermediates.
We also reported the regioselective oxidative synthesis of
head-to-tail (H-T) bithiophenes 6(H-T) by using hydroxy-
(tosyloxy)iodobenzene [PhI(OH)OTs, HTIB].[12]
Entry Lewis acid
Solvent
Temp. [°C]
Time [h]
Yield [%]
We now present a detailed study of the oxidative biaryl
coupling reaction for the synthesis of substituted bithio-
phenes (Scheme 3). The reaction conditions permitted the
use of electron-rich thiophenes without oligo- or polymeri-
zation. We investigated the reaction mechanism and found
that the reaction would be mediated by diaryliodonium(III)
intermediates generated in situ from thiophenes and HTIB
in HFIP. In addition, we also synthesized oligothiophenes
with well-defined structures by repeated oxidative coupling
reactions.
1
2
3
BF3·Et2O
TMSOTf
TMSBr
CH2Cl2
CH2Cl2
CH2Cl2
–78
–78
–78
6
6
24
trace
trace
15
4
5
6
BF3·Et2O
TMSOTf
TMSBr
HFIP
HFIP
HFIP
r.t.
r.t.
r.t.
24
24
6
n.d.
n.d.
65
[a] Performed by using 3a (2 equiv.), PIFA (1 equiv.), and Lewis
acid (2 equiv.) in solvent.
Further screening of the iodine(III) reagent was carried
out by using HFIP as the solvent in conjunction with
2 equiv. of TMSBr (Table 2). The use of phenyliodine di-
acetate (PIDA) decreased the yield of the reaction product
(entry 1). However, HTIB gave a better result than PIFA
(entry 2). Interestingly, we noticed the importance of pre-
mixing thiophene 3a and HTIB for the yield of the coupling
product. Thus, TMSBr was added to a stirred solution of
3a and HTIB, and the reaction was completed at this stage,
giving a higher yield of the coupling product 4a (entry 3).
Other iodine reagents with an electron-withdrawing group,
Scheme 3. Biaryl coupling reactions of various substituted thio-
phenes.
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K. Morimoto, T. Nakae, N. Yamaoka, T. Dohi, Y. Kita
FULL PAPER
such as trifluoromethyl or fluoride, were less efficient for
Next we performed the coupling reaction with unsym-
this coupling reaction (entries 4 and 5). After the optimiza- metrical 3,4-disubstituted thiophenes. In the case of 3-
tion process, the biaryl coupling of various thiophenes was methyl-4-methoxythiophene (3i), the coupling product 4i
carried out under our standard conditions: 2 equiv. of was obtained as a single regioisomer, albeit in a low yield,
TMSBr, 1 equiv. of HTIB as the oxidant, and HFIP as the see reaction (4).
solvent.
Table 2. Screening of iodine(III) reagents in the coupling reaction,
see reaction (3).[a]
Entry
Iodine(III) reagent
Temp. [°C] Time [h]
Yield [%]
1
2
PhI(OCOCH3)2 (PIDA)
PhI(OH)OTs (HTIB)
PhI(OH)OTs (HTIB)
C6F5I(OH)OTs
r.t.
r.t.
r.t.
r.t.
r.t.
6
6
6
24
6
32
76
83
trace
67
3[b]
4
On the other hand, 3-methyl-4-(p-tolyl)thiophene (3j)
and 3-isobutyl-4-methylthiophene (3k) are good substrates
for this reaction, providing the coupling products 4j and 4k,
respectively, see reactions (5) and (6). However, the resulting
coupling products 4j and 4k are produced together with a
mixture of other regioisomers that are inseparable by col-
umn chromatography.
5
4-CF3C6H4I(OH)OTs
[a] Performed by using 3a (2 equiv.), IIII (1 equiv.), and TMSBr
(2 equiv.) in HFIP at room temperature. [b] TMSBr was added after
thiophene 3a had reacted with HTIB in HFIP.
Scope of the Reaction
The optimized conditions were then applied to examine
the scope and limitations of the reaction. The reaction was
found to be compatible with a wide range of substituted
thiophenes and the results are summarized in Table 3. The
alkylthiophenes 3a–c, with a small or large alkyl substitu-
ent, gave the desired coupling products in excellent yields
(entries 1–3). The bulkier substituent in 3d did not affect
the product yield (entry 4). In general, electron-rich alkoxy-
substituted bithiophenes, such as 3e and 3f,[15] have prob-
lems under acidic and oxidative conditions due to their low
oxidation potentials. When we attempted the coupling reac-
tions of 3e and 3f, the coupling products 4e and 4f were
obtained in 83 and 89% yields under the same reaction con-
ditions (entries 5 and 6). The 3,4-(diethylenedioxy)thio-
phene (EDOT) dimer 4g, which has a very low oxidation
potential and is a precursor for electropolymerization, giv-
ing a polymer with excellent conductivities and stable
doped states,[16] was produced in 61% yield (entry 7).
Highly Regioselective Oxidative Coupling Reactions of
Thiophenes
We were also interested in the regioselective coupling re-
actions of 3-monosubstituted thiophenes. For the coupling
reactions of β-substituted thiophenes, the resulting coupling
products were thought to be a mixture of three regioiso-
mers: head-to-head (H-H) coupled between the 2- and 2Ј-
positions of the thiophene ring, tail-to-tail (T-T) coupled
between the 5- and 5Ј-positions of the thiophene ring, and
head-to-tail (H-T) coupled between the 2- and 5Ј-positions
of the thiophene ring. However, we extended our coupling
reaction to various 3-monosubstituted thiophenes 5a–g
with electron-donating groups, such as alkyl and alkoxy,
and the H-T dimers were obtained as single isomers
(Table 4). The head-to-tail (H-T) dimers[3] are useful pre-
cursors for high quality, well-defined regioregular oligo-
and polythiophenes and their derivatives.[17] The regiochem-
istries of the products were determined by measurement of
Table 3. Scope of the coupling reaction.[a]
Entry
R
Time [h]
Yield [%]
1
2
3
4
5
6
7
8
nHex (3a)
Me (3b)
3
3
3
3
3
3
6
6
83
73
74
78
83
89
61
56
nOct (3c)
isobutyl (3d)
OMe (3e)
OBu (3f)
–O(CH2)2O– (3g)
p-tolyl (3h)
1
their H NMR spectra or by comparing them with authen-
tic samples. Alkylthiophenes 5a–d gave the desired products
in excellent yields and with high regioselectivities (entries 1–
4). The coupling reactions of sterically hindered substrates
5e and 5f also proceeded smoothly to give the desired H-T
coupling products (entries 5 and 6). The bromo group of 5g
[a] Performed by using 3 (2 equiv.), HTIB (1 equiv.), and TMSBr
(2 equiv.) in HFIP at room temperature.
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Metal-Free Oxidative Coupling Reactions
is tolerated under the reaction conditions (entry 7). In each
On the other hand, in the reaction of the 3-arylthiophene
case, the resulting coupling product contained less than 1% 5p, the yield of the coupling product was lower and the
or no other regioisomers.
starting materials remained almost unchanged, see reac-
tion (7). Moreover, the coupling products were obtained as
a mixture of regioisomers.
Table 4. Regioselective coupling reactions of 3-alkylthiophenes.[a]
Entry
R
Yield [%]
1
2
3
4
5
6
7
nHex (5a)
Me (5b)
78
87
88
75
74
75
72
Thiophenes bearing strongly electron-withdrawing
groups, such as acetyl, cyano, and chloro, did not react at
all and the starting materials were recovered unchanged un-
der the present oxidative reaction conditions. These results
indicate that the electronic effects of the substituent on the
thiophene ring[18] are important if this coupling reaction is
to proceed.
nBu (5c)
nOct (5d)
isobutyl (5e)
cHex (5f)
–(CH2)6–Br (5g)
[a] Performed by using 5 (2 equiv.), HTIB (1 equiv.), and TMSBr
(2 equiv.) in HFIP at room temperature.
Mechanistic Considerations
Alkoxythiophenes
The reason for the H-T product selectivity is the focus of
We examined various 3-alkoxy-substituted thiophenes continuing investigation. We assumed that the intermediate
5h–o to explore the substrate scope under our reaction con- of this coupling reaction is different to that of the coupling
ditions (Table 5). The reactions proceeded smoothly and reactions of phenyl ethers and alkylarenes, which proceed
gave the corresponding H-T bithiophenes 5h–o(H-T) in via cation radical intermediates.[8] When we carried out the
high yields as a single isomer. The bithiophenes 6i(H-T) and reaction in the absence of TMSBr, stable diaryliodonium
6j(H-T) should be useful precursors for high-conducting salts of the thiophenes were obtained in high yields. There-
polymers (entries 2 and 3) as poly(3-butoxythiophene)s and fore we presumed from this result that the coupling reac-
poly(3-hexyloxythiophene)s are frequently used as soluble, tions of thiophenes proceed via the diaryliodonium salts.
conjugated polymers with excellent stability in air.[1] Steric To clarify the precise reaction mechanism for this oxidative
effects affected neither the reactivity nor selectivity of the biaryl coupling reaction, we examined the reactivity of the
reactions with 5k and 5l, giving the coupling products diaryliodonium salts.
6k(H-T) and 6l(H-T) in high yields. The fluoroalkyl-substi-
First, 3-methylthiophene (5b) was treated with the HTIB
tuted thiophene 5m also provided 6m(H-T) as a single iso- in HFIP to form the stable iodonium salt 7b-OTs in 98%
mer in 75% yield. The presence of protecting groups such yield.[13] The iodonium salt 7b-OTs was then treated with
as 2-(2-methoxyethoxy)ethyl (MEET) and benzyl were well thiophene 5b in the presence of TMSBr to produce the cou-
tolerated, affording the corresponding coupling products pling product in comparable yield under the same reaction
6n(H-T) and 6o(H-T) in good yields.
conditions. However, 7b-OTs did not react with 5b in the
absence of TMSBr (Scheme 4).
Table 5. Regioselective coupling reactions of 3-alkoxythiophenes.[a]
Entry
R
Yield [%]
1
2
3
4
5
6
7
8
Me (5h)
85
84
75
73
70
75
72
61
nHex (5i)
nBu (5j)
isobutyl (5k)
cHex (5l)
–CH2(CF2)5CF3 (5m)
(CH2)2O(CH2)2OCH3 (5n)
Bn (5o)
[a] Performed by using 5 (2 equiv.), HTIB (1 equiv.), and TMSBr
(2 equiv.) in HFIP at room temperature.
Scheme 4. Reactivity of iodonium salt 7b-OTs.
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K. Morimoto, T. Nakae, N. Yamaoka, T. Dohi, Y. Kita
FULL PAPER
We next examined the role of TMSBr in the reaction. vices.[19] Therefore the synthesis of oligothiophenes with
When iodonium tosylate 7b-OTs was treated with 1 equiv. well-defined structures is highly important. We envisaged
of TMSBr in HFIP, the iodonium bromide was obtained in a facile synthesis of extended oligomers by repeating the
78% yield. From this result, it is clear that one of the im- oxidative coupling and thus they have been synthesized by
portant steps is the generation of the iodonium bromide utilizing our coupling method (Scheme 6). As a result, 5-
intermediate 7b-Br, see reaction (8).
arylated 2,2Ј-bithiophene 8 was obtained in 44% yield when
the activated PIFA/BF3·Et2O-induced cross-coupling of 4e
was carried out with 3 equiv. of pentamethylbenzene. Re-
peated oxidative cross-coupling led to 5,5Ј-diaryl-2,2Ј-bi-
thiophene 9 in 20% yield under the same conditions. 5,5Ј-
Diaryl-2,2Ј-bithiophenes have been shown to be useful as
organic semiconductors and fluorescent materials.[19c,19d]
Our method has a significant advantage as it does not re-
quire stoichiometric metalation or halogenation of the aro-
matics.
The isolated iodonium bromide 7b-Br reacted with the
3-methylthiophene (5b) in the presence of 1 equiv. of
TMSBr to give the coupling product 6b(H-T) in 76% yield,
see reaction (9). In this case, no transfer of the phenyl group
from the salts was observed.
A plausible reaction mechanism for the present oxidative
coupling of thiophenes is illustrated in Scheme 5. As pre-
sumed from our experimental results, first, HTIB induces
the SET oxidation of thiophenes to produce the cation radi-
cal via the CT complex in HFIP. The formation of the cat-
ion radical A is sufficiently confirmed by the UV spectra.[14]
The cation radical can selectively react at the 2-position
with the iodine oxidant to form the stable iodonium-OTs 7-
OTs. This process occurs rapidly with the aid of the fluoro
alcohol solvent. From this experiment, it is clear that 7-OTs
reacts with TMSBr and the resulting iodonium bromide B
is activated by the added TMSBr in HFIP to induce further
reactions and provide the bithiophenes 6(H-T).
Scheme 6. Short-step synthesis of oligoaryls from the dimer 4e.
Conclusions
We have described herein the oxidative biaryl coupling
reaction of substituted thiophenes using a combination of
a hypervalent iodine(III) reagent with TMSBr in HFIP at
room temperature. Our novel biaryl coupling reaction has
some characteristic features: 1) Direct and regioselective
coupling of substituted thiophenes without the use of tran-
sition-metal catalysts or heavy-metal oxidants and 2) the
coupling reaction proceeds via the stable iodonium interme-
diate generated in situ from thiophenes and the iodine(III)
reagent. The high regioselectivities might be attributed to
this thiophene intermediate.
Scheme 5. Plausible mechanism for the coupling reaction.
Experimental Section
General: 1H and 13C NMR spectra were recorded with a JEOL
Convenient Synthesis of Substituted Thiophene Oligomer
Poly- and oligoaryl compounds involving thiophenes
JMN-300 spectrometer operating at 300 MHz in CDCl3 and
have been used to prepare electronic and electro-optical de- CD3OD at 25 °C with tetramethylsilane as the internal standard.
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Metal-Free Oxidative Coupling Reactions
The data are reported as follows: Chemical shifts (δ) in ppm, multi-
plicity (s singlet, d doublet, t triplet, q quartet, quint quintet, br.
broad, m multiplet), coupling constant in Hz, integration, and in-
terpretation. IR spectra were recorded by using a Hitachi 270-50
spectrometer; intensities of absorptions are reported in reciprocal
centimeters. Mass spectra were obtained by using a Shimadzu GC–
MS QP 5000 spectrometer with ionization voltages of 70 eV. High-
resolution mass spectra were recorded by the Elemental Analysis
Section of Osaka University. Column chromatography and TLC
were carried out on Merck silica gel 60 (230–400 mesh) and Merck
silica gel F254 plates (0.25 mm), respectively.
3,3Ј,4,4Ј-Tetrabutoxy-2,2Ј-bithiophene (4f): A brown solid; m.p.
132–133 °C. H NMR (400 MHz, CDCl3): δ = 0.95 (t, J = 7.4 Hz,
12 H), 1.42–1.53 (m, 8 H), 1.72–1.83 (m, 8 H), 3.94 (t, J = 6.3 Hz,
4 H), 4.07 (t, J = 6.7 Hz, 4 H), 6.03 (s, 2 H) ppm. 13C NMR
(100.53 MHz, CDCl3): δ = 14.6, 14.7, 19.9, 20.1, 32.1, 33.0, 70.4,
1
73.2, 95.3, 118.7, 142.9, 150.4 ppm. IR (KBr): ν = 3113, 2957, 2933,
˜
1548, 1458, 1376, 1261, 1229, 1194, 1172, 1145, 1068, 1025, 958,
902, 849, 750, 724, 688 cm–1. HRMS (FAB): calcd. for C24H38O4S2
[M]+ 454.2212; found 454.2219.
3,4:3Ј,4Ј-Bis(ethylenedioxy)-2,2Ј-bithiophene(4g):[22] A white solid;
1
m.p. 205–207 °C. H NMR (300 MHz, CDCl3): δ = 4.24 (m, 4 H),
4.36 (m, 4 H), 6.27 (s, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ
Representative Procedure for the Direct Oxidative Biaryl Coupling
Reaction of Thiophenes: HTIB (0.3 mmol) and then TMSBr
(0.08 mL, 0.6 mmol) were added to a stirred solution of 3,4-dihex-
ylthiophene (3a; 151 mg, 0.6 mmol) in HFIP (6 mL) at room tem-
perature and the color of the solution immediately changed to
brown. After stirring for 3 h, CH2Cl2 and saturated aq. NaHCO3
were successively added to the reaction mixture with stirring. The
organic layer was then separated and the solvents evaporated to
dryness. The residue was evaporated and subjected to column
chromatography (SiO2, hexane) to give 3,3Ј,4,4Ј-tetrahexyl-2,2Ј-bi-
thiophene (4a; 125 mg, 83%) as a pale-yellow oil. The regiochemis-
try of the product 4a was determined by comparing it with an
authentic sample.
= 64.6, 65.0, 97.5, 109.9, 137.0, 141.2 ppm. IR (KBr): ν = 2924,
˜
2868, 2361, 2341, 1566, 1468, 1439, 1364, 1244, 1173, 1144, 1057,
1024, 951, 897, 866, 745, 700, 652 cm–1. HRMS (FAB): calcd. for
C12H14O4S2 [M]+ 282.0021; found 283.0076.
3,3Ј,4,4Ј-Tetra(p-tolyl)-2,2Ј-bithiophene (4h): A pale-yellow solid;
1
m.p. 201–204 °C. H NMR (400 MHz, CDCl3): δ = 2.24 (s, 6 H),
2.26 (s, 6 H), 6.69 (d, J = 7.8 Hz, 4 H), 6.85 (d, J = 7.8 Hz, 4 H),
6.91–6.99 (m, 8 H), 7.17 (s, 2 H) ppm. 13C NMR (100.53 MHz,
CDCl3): δ = 21.1, 21.3, 123.2, 128.4, 128.6, 128.7, 128.8, 130.3,
132.6, 133.9, 136.0, 136.2, 140.0, 142.4 ppm. IR (KBr): ν = 3022,
˜
2921, 2859, 1523, 1492, 1449, 1378, 1345, 1261, 1184, 1125, 1109,
1021, 911, 870, 818, 737, 700, 651 cm–1. HRMS (FAB): calcd. for
C36H30S2 [M]+ 526.1789; found 526.1801.
3,4Ј-Dimethoxy-3Ј,4-dimethyl-2,2Ј-bithiophene (4i):[23] A brown oil.
1H NMR (300 MHz, CDCl3): δ = 2.10 (s, 3 H), 2.13 (s, 3 H), 3.65
(s, 3 H), 3.82 (s, 3 H), 6.19 (s, 1 H), 6.82 (s, 1 H) ppm. 13C NMR
(100.53 MHz, CDCl3): δ = 11.9, 13.3, 57.0, 60.1, 95.6, 117.6, 119.3,
3,3Ј,4,4Ј-Tetrahexyl-2,2Ј-bithiophene (4a): A pale-yellow oil. 1H
NMR (400 MHz, CDCl3): δ = 0.81–0.91 (m, 12 H), 1.19–1.39 (m,
28 H), 1.61–1.67 (m, 4 H), 2.42 (t, J = 8.0 Hz, 4 H), 2.52 (t, J =
7.7 Hz, 4 H), 6.92 (s, 2 H) ppm. 13C NMR (100.53 MHz, CDCl3):
δ = 14.1, 14.1, 22.5, 22.6, 27.6, 29.3, 29.3, 29.4, 29.7, 30.4, 31.5,
31.8, 120.0, 129.8, 141.4, 142.3 ppm. IR (KBr): ν = 2926, 2855,
˜
127.4, 127.7, 131.7, 153.4, 156.4 ppm. IR (KBr): ν = 2925, 2853,
˜
2340, 1462, 1377, 1261, 1171, 1016, 874, 797, 743 cm–1. HRMS
(FAB): calcd. for C32H54S2 [M]+ 502.3667; found 502.3667.
1726, 1551, 1497, 1454, 1380, 1261, 1203, 1150, 1100, 1021, 876,
854, 822, 768, 750, 660, 612 cm–1.
3,3Ј,4,4Ј-Tetramethyl-2,2Ј-bithiophene (4b):[20] A colorless crystal;
m.p. 87–88 °C. 1H NMR (300 MHz, CDCl3): δ = 2.01 (s, 6 H), 2.16
(s, 6 H), 6.88 (s, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 13.4,
3,4Ј-Dihexyl-2,2Ј-bithiophene [6a(H-T)]:[24] A pale-yellow oil. 1H
NMR (300 MHz, CDCl3): δ = 0.84–0.92 (m, 6 H), 1.20–1.35 (m,
12 H), 1.52–1.70 (m, 4 H), 2.63 (t, J = 8.4 Hz, 2 H), 2.74 (t, J =
8.4 Hz, 2 H), 6.89–6.92 (m, 2 H), 7.03 (s, 1 H), 7.12 (d, J = 5.5 Hz,
1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1, 22.6, 29.0, 29.1,
29.2, 29.7, 30.4, 30.5, 30.7, 31.6, 31.7, 119.9, 123.4, 124.8, 127.3,
129.9, 130.9, 135.8, 139.3, 143.5 ppm. HRMS (FAB): calcd for
C20H30S2 [M]+ 334.1789; found 334.1784.
3,4Ј-Dimethyl-2,2Ј-bithiophene [6b(H-T)]:[25] A pale-yellow oil. 1H
NMR (300 MHz, CDCl3): δ = 2.28 (s, 3 H), 2.38 (s, 3 H), 6.86–
6.87 (m, 2 H), 6.94 (s, 1 H), 7.11 (d, J = 5.1 Hz, 1 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 15.3, 15.7, 120.4, 123.0, 127.7, 131.3,
133.7, 136.3, 138.0, 141.3 ppm. HRMS (FAB): calcd. for
C20H26O2S2 [M]+ 362.1374; found 362.1371.
3,4Ј-Dibutyl-2,2Ј-bithiophene [6c(H-T)]:[26] A pale-yellow oil. 1H
NMR (300 MHz, CDCl3): δ = 0.83–0.96 (m, 6 H), 1.29–1.42 (m, 4
H), 1.58–1.67 (m, 4 H), 2.61 (t, J = 7.5 Hz, 2 H), 2.75 (t, J =
7.5 Hz, 2 H), 6.87–6.96 (m, 3 H), 7.13 (d, J = 5.1 Hz, 1 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 13.9, 22.4, 22.6, 28.9, 30.2 (ϫ2),
32.6, 32.9, 119.9, 123.4, 127.3, 129.9, 130.9, 134.1, 139.3,
15.4, 120.6, 131.1, 136.9, 178.4 ppm. IR (KBr): ν = 2922, 2253,
˜
1445, 1385, 1261, 1096, 988, 912, 860, 787, 743, 650, 623 cm–1.
3,3Ј,4,4Ј-Tetraoctyl-2,2Ј-bithiophene (4c):[21] A pale-yellow oil. 1H
NMR (300 MHz, CDCl3): δ = 0.83–0.89 (m, 12 H), 1.24–1.39 (m,
44 H), 1.53–1.68 (m, 4 H), 2.43 (t, J = 8.1 Hz, 4 H), 2.52 (t, J =
8.1 Hz, 4 H), 6.91 (s, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
14.1, 22.7, 27.5, 29.2, 29.2, 29.3, 29.3, 29.5, 29.5, 29.6, 29.7, 29.7,
30.5, 31.9, 31.9, 31.9, 120.0, 129.8, 141.3, 142.3 ppm. IR (KBr): ν
˜
= 3051, 2955, 2924, 2855, 1728, 1464, 1377, 1263, 1121, 895, 874,
789, 746, 706 cm–1.
3,3Ј,4,4Ј-Tetraisobutyl-2,2Ј-bithiophene (4d): A pale-yellow oil. 1H
NMR (400 MHz, CDCl3): δ = 0.72 (d, J = 6.8 Hz, 12 H), 0.92 (d,
J = 6.4 Hz, 12 H), 1.62–1.72 (m, 2 H), 1.83–1.93 (m, 2 H), 2.30 (d,
J = 7.2 Hz, 4 H), 2.40 (d, J = 7.2 Hz, 4 H), 6.90 (s, 2 H) ppm. 13C
NMR (100.53 MHz, CDCl3): δ = 22.5, 22.6, 28.8, 29.1, 36.7, 38.7,
121.0, 130.9, 140.1, 141.4 ppm. IR (KBr): ν = 3051, 2955, 2928,
˜
2868, 1726, 1464, 1433, 1383, 1366, 1337, 1275, 1263, 1207, 1167,
1124, 1076, 1040, 895, 881, 862, 802, 748, 706, 665 cm–1. HRMS
(FAB): calcd. for C24H38S2 [M]+ 390.2415; found 390.2419.
143.5 ppm. IR (KBr): ν = 3051, 2930, 2858, 1732, 1456, 1377, 1263,
˜
1088, 831, 748, 652 cm–1. HRMS (FAB): calcd. for C18H22S2 [M]+
278.1163; found 278.1162. C16H22S2 (278.48): C 69.01, H 7.96, S
23.03; found C 69.01, H 7.93, S 22.74.
3,3Ј,4,4Ј-Tetramethoxy-2,2Ј-bithiophene (4e): A white solid; m.p.
1
195–196 °C. H NMR (400 MHz, CDCl3): δ = 3.83 (s, 6 H), 3.88
(s, 6 H), 6.10 (s, 2 H) ppm. 13C NMR (100.53 MHz, CDCl3): δ = 3,4Ј-Dioctyl-2,2Ј-bithiophene [6d(H-T)]:[27] A pale-yellow oil. 1H
57.2, 60.0, 94.6, 117.8, 142.9, 150.3 ppm. IR (KBr): ν = 3942, 3105,
NMR (300 MHz, CDCl3): δ = 0.86–0.88 (m, 6 H), 1.20–1.30 (m,
20 H), 1.56–1.63 (m, 4 H), 2.60 (t, J = 7.5 Hz, 2 H), 2.74 (t, J =
7.5 Hz, 2 H), 6.88–6.93 (m, 3 H), 7.14 (d, J = 5.1 Hz, 1 H) ppm.
13C NMR (62.8 MHz, CDCl3): δ = 14.12, 15.28, 22.68, 29.14,
˜
3058, 2986, 2936, 2685, 2305, 1552, 1475, 1447, 1435, 1421, 1402,
1261, 1203, 1151, 1028, 993, 897, 864, 764, 748, 704 cm–1. HRMS
(FAB): calcd. for C12H14O4S2 [M]+ 286.0334; found 286.0334.
Eur. J. Org. Chem. 2011, 6326–6334
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
6331

K. Morimoto, T. Nakae, N. Yamaoka, T. Dohi, Y. Kita
FULL PAPER
29.27, 29.36, 29.42, 29.44, 29.55, 30.43, 30.51, 30.73, 31.89, 119.87,
123.38, 127.30, 129.89, 130.97, 135.83, 139.36, 143.54 ppm. IR low oil. H NMR (400 MHz, CDCl3): δ = 1.00 (d, J = 6.8 Hz, 6
3,4Ј-Bis(2-methylpropyloxy)-2,2Ј-bithiophene [6k(H-T)]: A pale-yel-
1
(KBr): ν = 2953, 2924, 2853, 2359, 2341, 1556, 1529, 1464, 1412, H), 1.07 (d, J = 6.8 Hz, 6 H), 2.04–2.15 (m, 2 H), 3.69 (d, J =
˜
1303, 1200, 1086, 864, 831, 721, 687, 669, 652 cm–1. C24H38S2
(390.68): calcd. C 73.78, H 9.80, S 16.42; found C 73.83, H 9.82, S
16.13.
6.4 Hz, 2 H), 3.86 (d, J = 6.4 Hz, 2 H), 6.08 (d, J = 1.6 Hz, 1 H),
6.79 (d, J = 5.6 Hz, 1 H), 6.88 (d, J = 1.6 Hz, 1 H), 7.01 (d, J =
5.6 Hz, 1 H) ppm. 13C NMR (100.53 MHz, CDCl3): δ = 19.2, 19.3,
28.2, 28.7, 76.4, 78.1, 95.4, 114.5, 115.0, 117.1, 121.4, 133.9, 153.0,
3,4Ј-Bis(2-methylpropyl)-2,2Ј-bithiophene [6e(H-T)]:[28] A pale-yel-
low oil. 1H NMR (300 MHz, CDCl3): δ = 0.90–0.94 (m, 12 H),
1.83–1.96 (m, 2 H), 2.46 (d, J = 7.2 Hz, 2 H), 2.61 (d, J = 7.2 Hz,
2 H), 6.85 (d, J = 1.2 Hz, 1 H), 6.89 (d, J = 5.1 Hz, 1 H), 6.90 (d,
J = 1.2 Hz, 1 H), 7.13 (d, J = 5.1 Hz, 1 H) ppm. 13C NMR
(100.53 MHz, CDCl3): δ = 22.4, 22.5, 29.6, 29.7, 38.1, 39.8, 120.8,
123.1, 128.0, 130.5, 131.5, 135.7, 138.4, 142.2 ppm. HRMS (FAB):
calcd. for C16H22S2 [M]+ 278.1163; found 278.1152.
157.2 ppm. IR (KBr): ν = 3114, 2958, 2929, 2871, 1567, 1538, 1466,
˜
1385, 1358, 1261, 1169, 1100, 1065, 1035, 1016, 982, 916, 866, 825,
806, 687, 640, 617 cm–1. HRMS (FAB): calcd. for C16H22O2S2
[M]+ 310.1061; found 310.1045.
3,4Ј-Bis(cyclohexyloxy)-2,2Ј-bithiophene [6l(H-T)]: A pale-yellow
oil. 1H NMR (400 MHz, CDCl3): δ = 1.26–1.39 (m, 6 H), 1.45–
1.57 (m, 4 H), 1.60–1.69 (m, 2 H), 1.78–1.81 (m, 4 H), 1.92–2.03
(m, 4 H), 4.08 (quint, J = 4.0 Hz, 1 H), 4.22 (quint, J = 4.0 Hz, 1
H), 6.11 (d, J = 1.6 Hz, 1 H), 6.78 (d, J = 5.6 Hz, 1 H), 6.88 (d, J
= 1.6 Hz, 1 H), 7.01 (d, J = 5.6 Hz, 1 H) ppm. 13C NMR
(100.53 MHz, CDCl3): δ = 23.4, 23.8, 25.5, 25.6, 31.8, 32.0, 76.7,
79.2, 97.1, 115.2, 116.6, 118.3, 121.3, 133.8, 151.5, 155.4 ppm. IR
1
3,4Ј-Dicyclohexyl-2,2Ј-bithiophene [6f(H-T)]: A pale-yellow oil. H
NMR (300 MHz, CDCl3): δ = 1.26–1.56 (m, 12 H), 1.72–1.87 (m,
6 H), 1.99–2.02 (m, 2 H), 2.57–2.59 (m, 1 H), 2.96–3.01 (m, 1 H),
6.91 (s, 1 H), 6.97–7.03 (m, 2 H), 7.15 (d, J = 5.4 Hz, 1 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 26.1 (ϫ2), 26.6, 26.7, 34.1, 34.4,
38.2, 39.6, 118.5, 123.8, 126.4, 127.3, 130.1, 135.5, 144.8,
(KBr): ν = 3111, 2934, 2856, 1563, 1534, 1465, 1387, 1360, 1261,
˜
1166, 1126, 1044, 1023, 993, 951, 915, 889, 865, 822, 808, 741, 687,
645, 622 cm–1. HRMS (FAB): calcd. for C20H26O2S2 [M]+
362.1374; found 362.1371.
149.3 ppm. IR (KBr): ν = 2923, 2851, 1728, 1448, 1263, 1124, 943,
˜
833, 731, 708, 650 cm–1. HRMS (FAB): calcd. for C20H26S2 [M]+
330.1476; found 330.1470. C20H26S2 (330.55): C 72.67, H 7.93, S
19.40; found C 72.66, H 7.86, S 19.09.
3,4Ј-Bis(2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyloxy)-2,2Ј-bithio-
phene [6m(H-T)]: A pale-yellow solid; m.p. 67–68 °C. 1H NMR
(400 MHz, CDCl3): δ = 4.24 (t, J = 12.8 Hz, 2 H), 4.52 (t, J =
12.8 Hz, 2 H), 6.29 (d, J = 1.6 Hz, 1 H), 6.81 (d, J = 5.6 Hz, 1 H),
6.97 (d, J = 1.6 Hz, 1 H), 7.11 (d, J = 5.6 Hz, 1 H) ppm. 13C NMR
(100.53 MHz, CDCl3): δ = 66.9 (t, J = 27.3 Hz), 68.0 (t, J =
27.3 Hz), 99.0, 110.5 (m), 110.9 (m), 114.7 (m), 115.4, 115.7 (m),
117.2, 118.0, 118.6 (m), 122.7, 133.6, 150.7, 155.2 ppm. IR (KBr):
3,4Ј-Bis(6-bromohexyl)-2,2Ј-bithiophene [6g(H-T)]:[29] A pale-yellow
oil. 1H NMR (300 MHz, CDCl3): δ = 1.30–1.51 (m, 8 H), 1.59–
1.71 (m, 4 H), 1.80–1.92 (m, 4 H), 2.61 (t, J = 7.5 Hz, 2 H), 2.75
(t, J = 7.5 Hz, 2 H), 3.40 (q, J = 7.5 Hz, 4 H), 6.89–6.92 (m, 3 H),
7.20 (d, J = 5.1 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
27.9, 28.4, 28.5, 28.9, 30.1, 30.2, 30.3, 30.4, 32.7, 33.9 (ϫ2), 120.0,
123.6, 127.3, 129.8, 131.0, 135.8, 139.0, 143.2 ppm. HRMS (FAB):
calcd. for C20H28Br2S2 [M]+ 489.9999; found 489.9988.
ν = 3113, 1568, 1535, 1458, 1415, 1360, 1235, 1202, 1146, 1099,
˜
1052, 984, 959, 913, 847, 805, 792, 743, 707, 688, 666, 633, 609,
563, 525 cm–1. HRMS (FAB): calcd. for C22H8F26O2S2 [M]+
861.9551; found 861.9556.
3,4Ј-Dimethoxy-2,2Ј-bithiophene [6h(H-T)]:[30] A pale-yellow oil. 1H
NMR (400 MHz, CDCl3): δ = 3.79 (s, 3 H), 3.92 (s, 3 H), 6.11 (d,
J = 1.6 Hz, 1 H), 6.84 (d, J = 5.6 Hz, 1 H), 6.88 (d, J = 1.6 Hz, 1
H), 7.05 (d, J = 5.6 Hz, 1 H) ppm. 13C NMR (100.53 MHz,
CDCl3): δ = 57.1, 58.8, 95.0, 114.7, 115.1, 116.8, 121.7, 133.9,
3,4Ј-Bis[2-(2-methoxyethoxy)ethoxy]-2,2Ј-bithiophene [6n(H-T)]: A
pale-yellow oil. 1H NMR (400 MHz, CDCl3): δ = 3.35 (s, 3 H),
3.36 (s, 3 H), 3.54 (m, 4 H), 3.69 (m, 4 H), 3.81 (t, J = 4.8 Hz, 2
H), 3.85 (t, J = 4.8 Hz, 2 H), 4.10 (t, J = 4.8 Hz, 2 H), 4.22 (t, J =
4.8 Hz, 2 H), 6.09 (d, J = 1.6 Hz, 1 H), 6.81 (d, J = 5.6 Hz, 1 H),
6.91 (d, J = 1.6 Hz, 1 H), 7.00 (d, J = 5.6 Hz, 1 H) ppm. 13C NMR
(100.53 MHz, CDCl3): δ = 59.0, 69.2, 69.6, 69.9, 70.6, 70.8, 71.2,
71.8, 71.9, 95.9, 114.9, 116.1, 117.8, 121.5, 133.7, 152.5, 156.7 ppm.
153.7, 157.9 ppm. IR (KBr): ν = 3113, 3002, 2935, 2852, 1568,
˜
1540, 1433, 1369, 1257, 1204, 1155, 1103, 1070, 1036, 962, 926,
914, 867, 824, 692, 645, 620 cm–1. HRMS (FAB): calcd. for
C10H10O2S2 [M]+ 226.0122; found 226.0123.
1
3,4Ј-Bis(hexyloxy)-2,2Ј-bithiophene [6i(H-T)]: A pale-yellow oil. H
NMR (400 MHz, CDCl3): δ = 0.87–0.92 (m, 6 H), 1.31–1.35 (m, 8
H), 1.41–1.55 (m, 4 H), 1.72–1.85 (m, 4 H), 3.93 (t, J = 6.4 Hz, 2
H), 4.07 (t, J = 6.4 Hz, 2 H), 6.08 (d, J = 1.6 Hz, 1 H), 6.81 (d, J
= 5.6 Hz, 1 H), 6.89 (d, J = 1.6 Hz, 1 H), 7.01 (d, J = 5.6 Hz, 1
H) ppm. 13C NMR (100.53 MHz, CDCl3): δ = 14.0, 22.5, 22.6,
25.6, 25.7, 29.2, 29.6, 31.5, 31.6, 70.0, 71.8, 95.3, 114.5, 115.3,
IR (KBr): ν = 3109, 2925, 2876, 1567, 1538, 1452, 1395, 1350,
˜
1259, 1199, 1176, 1110, 1075, 987, 932, 868, 823, 714, 688, 659,
640, 621 cm–1. HRMS (FAB): calcd. for C18H26O6S2 [M]+
402.1171; found 402.1159.
3,4Ј-Bis(benzyloxy)-2,2Ј-bithiophene [6o(H-T)]: A pale-yellow oil.
1H NMR (400 MHz, CDCl3): δ = 4.42 (s, 2 H), 5.17 (s, 2 H), 6.19
(d, J = 1.6 Hz, 1 H), 6.82 (d, J = 5.6 Hz, 1 H), 6.98 (d, J = 1.6 Hz,
1 H), 7.02 (d, J = 5.6 Hz, 1 H), 7.32–7.48 (m, 10 H) ppm. 13C
NMR (100.53 MHz, CDCl3): δ = 72.0, 73.5, 96.6, 115.0, 116.2,
117.8, 121.6, 127.3, 127.6, 128.0, 128.1, 128.5, 133.8, 136.7, 136.8,
117.3, 121.4, 133.9, 152.9, 157.1 ppm. IR (KBr): ν = 3114, 2932,
˜
2856, 1567, 1538, 1463, 1359, 1259, 1172, 1067, 1030, 912, 867,
826, 807, 713, 682, 639, 617 cm–1. HRMS (FAB): calcd. for
C20H30O2S2 [M]+ 366.1687; found 366.1683.
3,4Ј-Dibutoxy-2,2Ј-bithiophene [6j(H-T)]:[31] A pale-yellow oil. 1H
NMR (400 MHz, CDCl3): δ = 0.93–0.98 (m, 6 H), 1.45–1.52 (m, 4
H), 1.72–1.81 (m, 4 H), 3.93 (t, J = 6.4 Hz, 2 H), 4.08 (t, J =
6.4 Hz, 2 H), 6.08 (d, J = 1.6 Hz, 1 H), 6.80 (d, J = 5.6 Hz, 1 H),
152.4, 156.7 ppm. IR (KBr): ν = 3112, 3031, 2927, 2871, 1566,
˜
1536, 1454, 1353, 1261, 1205, 1166, 1059, 1026, 976, 912, 823, 740,
697, 640, 618 cm–1.
1
6.87 (d, J = 1.6 Hz, 1 H), 7.02 (d, J = 5.6 Hz, 1 H) ppm. 13C NMR 3,4Ј-Di-p-tolyl-2,2Ј-bithiophene [6p(H-T)]:[32] A pale-yellow oil. H
(100.53 MHz, CDCl3): δ = 13.8, 19.2, 31.3, 31.7, 69.7, 71.5, 95.4, NMR (400 MHz, CDCl3): δ = 2.32 (s, 3 H), 2.34 (s, 3 H), 7.04 (d,
114.5, 115.3, 117.3, 121.4, 133.9, 152.9, 157.1 ppm. IR (KBr): ν =
J = 5.1 Hz, 1 H), 7.12–7.15 (m, 4 H), 7.20–7.28 (m, 5 H), 7.37 (d,
J = 8.0 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.2,
˜
3114, 2957, 2871, 1567, 1538, 1463, 1399, 1360, 1260, 1173, 1072,
1040, 867, 844, 824, 742, 714, 684, 639, 618 cm–1. HRMS (FAB): 21.3, 120.0, 124.0, 125.6, 126.1, 129.1 129.2, 129.4, 130.6, 131.2,
calcd. for C16H22O2S2 [M]+ 310.1061; found 310.1063.
132.8, 133.2, 136.7, 136.9, 137.2, 139.1, 142.1 ppm.
6332
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 6326–6334

Metal-Free Oxidative Coupling Reactions
Phenyl(3-methyl-2-thienyl)iodonium Tosylate (7b-OTs):[33] A white
solid; m.p. 165 °C. 1H NMR (300 MHz, CD3OD): δ = 2.33 (s, 3
H), 2.49 (s, 3 H), 7.03 (d, J = 5.1 Hz, 1 H), 7.19 (d, J = 7.2 Hz, 2
H), 7.46–7.49 (m, 2 H), 7.59–7.67 (m, 3 H), 7.83 (d, J = 5.1 Hz, 1
H), 8.05 (d, J = 7.8 Hz, 2 H) ppm. 13C NMR (75.5 MHz, CD3OD):
δ = 17.5, 21.3, 98.4, 118.4, 126.9, 129.8, 131.0, 133.0, 133.1, 133.4,
For the synthesis of symmetrical bithiophenes, see: a) M. Kum-
ada, Pure Appl. Chem. 1980, 52, 669–679; b) M. J. Marsella,
P. J. Carroll, T. M. Swager, J. Am. Chem. Soc. 1994, 116, 9347–
9348; c) Y. Fort, S. Becker, P. Caubère, Tetrahedron 1994, 50,
11893–11902; d) J. Hassan, L. Lavenot, C. Gozzi, M. Lemaire,
Tetrahedron Lett. 1999, 40, 857–858; e) M. Turbiez, P. Frère,
M. Allain, C. Videlot, J. Ackermann, J. Roncali, Chem. Eur. J.
2005, 11, 3742–3752.
For the synthesis of unsymmetrical bithiophenes, see: a) W. Li,
Maddux, L. T. Yu, Macromolecules 1996, 29, 7329–7334; b)
M.-K. Ng, L. Yu, Angew. Chem. Int. Ed. 2002, 41, 3598–3601;
c) O. Hagemann, M. Jørgensen, F. C. Krebs, J. Org. Chem.
2006, 71, 5546–5559; d) C. Querner, A. Benedetto, R. Demad-
rille, P. Rannou, P. Reiss, Chem. Mater. 2006, 18, 4817–4826;
e) D. J. Turner, R. Anemian, P. R. MacKie, D. C. Cupertino,
S. G. Yeates, M. L. Turner, A. C. Spivey, Org. Biomol. Chem.
2007, 11, 1752–1763.
[2]
[3]
135.4, 137.7, 141.6, 150.0 ppm. IR (KBr): ν = 3051, 1575, 1469,
˜
1440, 1191, 1132, 1045, 1014, 991, 815, 746, 680 cm–1. HRMS
(FAB): calcd. for C11H10IS [M]+ 300.9548; found 300.9549.
Phenyl(3-methyl-2-thienyl)iodonium Bromide (7b-Br): A gray solid;
m.p. 132 °C. 1H NMR (300 MHz, CD3OD): δ = 2.54 (s, 3 H), 7.08
(d, J = 5.4 Hz, 1 H), 7.52 (t, J = 6.9 Hz, 2 H), 7.63–7.68 (m, 1 H),
7.86 (d, J = 5.4 Hz, 1 H), 8.08 (d, J = 7.2 Hz, 2 H) ppm. 13C NMR
(75.5 MHz, CD3OD): δ = 16.9, 104.2, 121.4, 129.7, 131.3, 131.4,
134.3, 135.5, 146.3 ppm. IR (KBr): ν = 3051, 2920, 2853, 1562,
˜
1526, 1468, 1439, 1375, 1319, 1263, 1157, 1086, 993, 1009, 824,
748, 727, 679, 675, 650 cm–1. HRMS (FAB): calcd. for C11H10IS
[M]+ 300.9548; found 300.9553. C11H10BrIS (381.07): calcd. C
34.67, H 2.65; found C 34.89, H 2.72.
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3,3Ј,4,4Ј-Tetramethoxy-5-pentamethylphenyl-2,2Ј-bithiophene (8): A
1
pale-yellow solid; m.p. 115–120 °C. H NMR (400 MHz, CDCl3):
δ = 2.16 (s, 6 H), 2.23 (s, 6 H), 2.26 (s, 3 H), 3.57 (s, 3 H), 3.83 (s,
3 H), 3.85 (s, 3 H), 3.94 (s, 3 H), 6.09 (s, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 16.7, 16.9, 18.5, 57.2, 59.1, 59.9, 60.1, 94.2,
116.3, 117.9, 120.6, 129.3, 132.4, 134.2, 135.5, 142.3, 144.6, 145.0,
[6]
[7]
150.4 ppm. IR (KBr): ν = 3111, 2933, 1556, 1520, 1477, 1388, 1308,
˜
1276, 1255, 1204, 1156, 1127, 1088, 1066, 1037, 997, 961, 750,
695 cm–1. HRMS (FAB): calcd. for C23H28O4S2 [M]+ 432.1249;
found 432.1434.
3,3Ј,4,4Ј-Tetramethoxy-5,5Ј-bis(pentamethylphenyl)-2,2Ј-bithiophene
(9): A pale-yellow solid; m.p. 268–271 °C. 1H NMR (400 MHz,
CDCl3): δ = 2.18 (s, 12 H), 2.23 (s, 12 H), 2.26 (s, 6 H), 3.56 (s, 6
H), 3.91 (s, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 16.7,
16.9, 18.5, 59.1, 60.0, 116.5, 120.4, 129.4, 132.4, 134.3, 135.5, 144.1,
145.2 ppm. IR (KBr): ν = 2935, 1557, 1474, 1381, 1263, 1208, 1160,
˜
1040, 997, 971, 765, 747, 706 cm–1. HRMS (FAB): calcd. for
C34H42O4S2 [M]+ 578.2525; found 578.2522.
Supporting Information (see footnote on the first page of this arti-
1
cle): H and 13C NMR spectra of the coupling products.
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Acknowledgments
This work was partially supported by Grants-in-Aid for Scientific
Research from the Japan Society for the Promotion of Science
(JSPS), the Industrial Technology Research Grant Program of the
New Energy and Industrial Technology Development Organization
(NEDO) of Japan, and the Ritsumeikan Global Innovation Re-
search Organization (R-GIRO). K. M. also acknowledges support
from the Research Activity Start-up of the JSPS.
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Published Online: September 14, 2011
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