Unusual thiophilic ring-opening of fused oligothiophenes with organolithium reagents

Article abstract of DOI:10.1016/j.tet.2011.06.082

Organolithium reagents attack the sulfur atoms of fused oligothiophenes producing ring-opened organolithium intermediates that can be trapped with a suitable electrophile. The reaction was found to be general for fused thieno[2,3-b]-thiophenes and some [3

Full text of DOI:10.1016/j.tet.2011.06.082

Tetrahedron 67 (2011) 6812e6818
Contents lists available at ScienceDirect
Tetrahedron
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Unusual thiophilic ring-opening of fused oligothiophenes with organolithium
reagents
,
Konstantin Chernichenko a, Nikolai Emelyanov a, Ilya Gridnev b, Valentine G. Nenajdenko a
*
a Moscow State University, Department of Chemistry, Leninskie Gory, Moscow 119992, Russia
b Tokyo Institute of Technology, Tokyo, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 May 2011
Received in revised form 16 June 2011
Accepted 24 June 2011
Available online 30 June 2011
Organolithium reagents attack the sulfur atoms of fused oligothiophenes producing ring-opened orga-
nolithium intermediates that can be trapped with a suitable electrophile. The reaction was found to be
general for fused thieno[2,3-b]-thiophenes and some [3,2-b]-fused oligothiophenes. Thermodynamic
(organilithiums basicity) and mechanistic (RLi coordination by neighboring sulfur) aspects control the
substrate scope and regioselectivity of the reaction. When competitive deprotonation of the substrate is
possible, high selectivity toward ring-opening was observed with n-BuLi when compared with the other
tested organolithiums. The recently discovered octathio[8]circulene produces multifold ring-opening
products.
Keywords:
Thiophene
Oligothiophene
Organolithium
Thiophilic
Ó 2011 Elsevier Ltd. All rights reserved.
Ring-opening
Li
1. Introduction
Classical
AlkX
ring-opening:
S-
S
1
SAlk
Recently, much attention has been dedicated to fused oligo-
thiophenes as potential organic semiconductors for various appli-
cations.1 Stability and aromaticity of the thiophene core as well as
unique properties of the sulfur atom allows even the preparation of
fully thiophenic helicenes2 and circulenes.3 Several novel ap-
proaches toward fused oligothiophenes have been published re-
cently demonstrating great progress achieved in this field.4 Thus
further work on the synthesis of fused oligothiophenes as well as
their chemical properties is of particular interest.
Herein we report the unusual reactivity of fused oligothiophenes
toward organolithium reagents, which leads to cleavage of the
thiophene ring. Ring-opening of thiophene, e.g., 3-lithiothiophenes
1 (Scheme 1) and other heterocyclic cores, such as oxazoles and
thiazoles is a well-known reaction type in heterocyclic chemistry.5
However, in 1998 Belly et al. reported an addition reaction in
which organolithiums attack the sulfur atoms of certain chlor-
othiophenes 4. As a result, ring-opened lithium species 5 are formed
that can be trapped with various electrophiles. Later, this reaction
type was extended to 2-fluoro-3-arylbenzothiophenes.6 More
recently Wang et al. reported dithieno[2,3-b;30,20-d]thiophene
systems 6 to react similarly.7 Despite being well-known for
3
2
R2
R2
Cl
Thiophilic
ring-opening:
N
S
RLi
N
S
R1
R1
Cl
4a
Li
S
5a
SR
R4
R4
R5
R3
R5
RLi
R3
4b
Li
SR
S
5b
R=Me, Bu, s-Bu, t-Bu;
R1=Me, NHAc; R2=H, Cl;
R3=Cl, Ph; R4=Cl; R5=H;
R3=F; R4=Ph, PMP; R5=H, Cl;
R7
R7
R7 R7
R6
R6
BuLi
R6
R6
S
S
S
S
S
S
Li
6
7
Bu
R6=H, Alk, Ar, COOEt, TMS; R7=H;
R6R7=CH=CHCH=CH
* Corresponding author. E-mail addresses: gridnev.i.aa@m.titech.ac.jp (I. Gridnev),
Scheme 1. Classical ring-opening of 3-lithiothiophenes and previously reported
nen@acylium.chem.msu.ru (V.G. Nenajdenko).
examples of thiophilic ring-opening.
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.06.082

K. Chernichenko et al. / Tetrahedron 67 (2011) 6812e6818
6813
selenophenes and 1,2-thiazoles,8 thiophilic ring-opening of thio-
phene was previously reported only among the mentioned sub-
strates. Moreover no explanations were provided for such unusual
thiophene reactivity and were considered to be uncommon.
substrate to measure the ring-opening selectivity of different
organolithiums (Table 1) due to its ability to undergo both depro-
tonation and ring-opening reactions. The reaction mixture was
treated with proton source (1 M HCl) to provide quantitative con-
version of the organolithium intermediates to the respective
products. For alkyllithiums the product ratio was the same after 15,
45, and 90 min, implying that the reaction was fully converted
within minutes at ꢀ80 ꢁC. The reaction with phenyllithium, which
has relatively low basicity, was done at room temperature as it was
unreactive at ꢀ80 ꢁC (15% of 10g after 45 min). Methyl- and tert-
butyllithium led mainly to ring-opening products, though not in
quantitative yield as with n-butyllithium. Both the relatively highly
basic sec-butyllithium and the less basic phenyllithium mostly
deprotonate dithieno[2,3-b;30,20-d]thiophene.11 The absence of the
strong correlation between basicity of the organolithium and its
ring-opening selectivity argues for a more complex mechanism
than just a simple nucleophilic attack of RLi on the central sulfur
atom (see below).
Despite the fact that previous examples of thiophilic ring-
opening were fused thiophenes (2- or 3-chloro- and fluo-
rothiophenes fused with another aromatic ring, e.g., benzene,
thiazole or pyridine, and dithieno[2,3-b;30,20-d]thiophene core),6,7
there were no attempts made on a wide variation of oligothio-
phene core. However the substrate scope of the reaction is a crucial
issue shedding light on mechanism and the driving force of the
thiophilic ring-opening reaction. We have screened various fused
oligothiophenes using n-butyllithium, which was shown to be the
most selective ring-opener in experiments with 8.
2. Results and discussion
In the course of our work on dithieno[2,3-b;30,20-d]thiophene 8
functionalization9 we have discovered independently thiophilic
ring-opening of dithieno[2,3-b;30,20-d]thiophene 8. Attempted
deprotonationwith n-butyllithium inTHFat ꢀ80 ꢁC produces almost
exclusively unexpected derivatives 10. The formed organolithium
intermediate was trapped with various electrophiles: proton source
(1 M HCl), 4-methoxybenzaldehyde and dimethyl disulfide to give
products 10a, 10b, and 10c, respectively. The methylsulfanyl de-
rivative 10c was oxidized to give crystalline bis-sulfone 12 and its
structure was proved unambiguously by X-ray diffraction (Table 1,
Scheme 2).10 In contrast, when a lithium amide base was used, the
product of deprotonation 11 was isolated in high yield.
Table 1
Distribution of ring-opening versus deprotonation products of 8 with various
organolithiumsa
1) 1.1 eq. RLi,
THF
+
S
S
S
S
S
2) H2O
S
S
8
S
S
8
10
R
R
Solvent,
Ring-opening
product
Yield of ring-opening
product, %
Yield of
8 (%)
We have found that the reaction of thiophilic ring-opening is
general for fused oligothiophenes 13e15 and circulene 16 con-
taining thieno[2,3-b]thiophene fragment (Scheme 3). As in the case
of dithieno[2,3-b;30,20-d]thiophene 8 attack of organometallics is
directed on the central thiophene core for substrates containing
non-equivalent thiophenic nuclei. For example, when 14 was
treated subsequently with MeLi and MeSSMe, symmetrical 23 was
isolated as the only product.
However, it is well-known from the literature that dibenzo-
thiophene 2912 and isomeric dithieno[3,2-b:20,30-d]thiophene 3013
are smoothly deprotonated with butyllithium in THF to form ortho-
substituted products 32 and 33, respectively (Scheme 4). Moreover,
we have found that [1]benzothieno[3,2-b][1]benzothiophene 31
gives exclusively 34, the product of deprotonation, when treated
with BuLi followed by dimethyl disulfide. Thus we concluded that
[3,2-b]-fusion of thiophenic rings does not undergo thiophilic ring-
opening, and alternative reactions, such as deprotonation occur.
In contrast, treatment of [1]benzothieno[20,30:4,5]thieno[3,2-b]
[1]benzothiophene 17 with BuLi leads to the ring-opened product
27 (Scheme 3). The reaction rate is very slow, even at room tem-
perature and with 150% excess of BuLi the conversion reaches only
42% after 2 h (at longer reaction times butyllithium is fully
decomposed by THF). Interestingly, in spite of [2,3-b]-fused 8, 14,
and 15, butyllithium opens regioselectively the side thiophenic core
of 17.
The vast difference in reactivity of different fused oligothio-
phenes can be explained by precoordination of organolithium to
the sulfur atom, which facilitates attack on the conjunct thiophene
ring (Fig. 2). A very high reaction rate (generally within minutes
at ꢀ80 ꢁC) in the case of [2,3-b]-fused oligothiophenes is likely due
to optimal configuration for thiophilic attack. Longer distance
between one-sided thiophene rings in 17 hampers optimal con-
figuration and results in low reaction rate. The crucial role of
complexation is also supported by the observed ring-opening
regioselectivity for 17. In 31 coordinated RLi cannot reach the sul-
fur atom of the conjunct thiophene ring and ortho-deprotonation
occurs. Generally thiophenes are easily deprotonated by strong
temperature, ꢁC
Bu
THF, ꢀ80
THF, ꢀ80
THF, ꢀ80
THF, ꢀ80
THF, rt
10a
10d
10e
10f
10g
98
68
23
80
40
2
32
77
20
60
Me
s-Bu
t-Bu
Ph
a
To solution of 8 in THF at ꢀ80 ꢁC 1.1 equiv RLi was added and stirred at this
temperature. Samples were taken after 15, 45, and 90 min and quenched with
watereTHF mixture. Products distribution was measured by 1H NMR and was
unchanged with time.
BuLi, THF
E+
-80 °C
S
S
S
S
S
S
S
S
E
S
Li
8
9
Bu
Bu
1)TMPLi, THF, -80 °C
2)PMPCHO
OH
10a, E=H, 98%
10b, E=PMPCH(OH), 63%
10c, E=SMe, 95%
PMP
PMP = 4-methoxyphenyl
TMP = 2,2,6,6-tetramethylpiperidyl
S
S
S
11, 72%
S
H2O2,
Bu
O
O
S
O
AcOH
S
10c
S
=
O
12, 82%
Scheme 2. Ring-opening and deprotonation of dithieno[2,3-b;30,20-d]thiophene 8.
X-ray structure of bis-sulfone 12.
This surprising reactivity of dithieno[2,3-b;30,20-d]thiophene
promoted us to study it systematically. To gain further insight
into the problem the nature of the organolithium reagent was
varied. Dithieno[2,3-b;30,20-d]thiophene 8 was chosen as a model
bases in
a-, b- (if a-positions are occupied) and ortho-position

6814
K. Chernichenko et al. / Tetrahedron 67 (2011) 6812e6818
BuS
1) BuLi, THF
-80 °C, 1 h
E
+
2) E+
S
S
S
S
E
SBu
13
18 E=D 19
20 E=H 21
67%
14%
E
S
SR
1) RLi, THF
-80 °C, 1 h
S
S
S
S
22, R=Bu, E=H,
100%
S
23, R=Me, E=SMe, 80%
2) E+
14
S
S
S
1) BuLi, THF
-80 °C, 15 min
S
S
S
SBu
2) MeOH
15
24, 23% (conversion 100%)
SMeSMe
S
SMeSMe
S
S
S
S
1) 10 eq.
MeLi, THF,
r. t., 2 h
S
S
S
S
S
SMe
SMe
MeS
MeS
SMe
SMe
MeS
MeS
S
S
+
2) 20 eq.
MeSSMe
S
S
S
S
S
SMe
SMe
25, 30%
16
26, 21%
1) 2.5 eq. BuLi,
THF, r. t., 2 h
S
S
2) MeOH
S
S
S
S
BuS
SBu
S
17
27, 42%
28, not observed
Scheme 3. Thiophilic ring-opening of fused thiophenic systems.
1)BuLi, THF
2) E+
In the computed transition state for the ring-opening reaction
(Fig. 3) the Li atom is found almost directly over the sulfur atom of
the opened thiophene ring on its way to the -carbon atom of the
second thiophene ring. This structure of the transition state illus-
trates the cooperation of the adjacent thiophene rings in the ring-
opening reaction.
S
S
S
S
a
E
32
29
1)BuLi, THF
2) E+
S
S
S
S
E
30
33
Thermodynamically, the driving force of the reaction is a de-
crease in basicity from the highly basic organolithium reagent to
less basic products. Intramolecular coordination of the formed
organolithium intermediate by the alkyl- or arylsulfanyl sub-
stituent likely provides additional stabilization. We have found that
the structure of the organolithium intermediate generated during
ring-opening correlates with its basicity and mainly the less basic
product is formed. For example, benzothienobenzothiophene 13
gives mainly 18 and 20 via intermediate formation of its less basic
lithium derivative. Compounds 20 and 21 formed as minor prod-
ucts, are derived from the more basic phenyllithium salt.14 Similarly
trithienothiophene 15 yields the only type of ring-opening product
24, due to the much lower basicity of thieno[3,2-b]thien-2-
yllithium than the alternative thien-3-yllithium derivative.
1)BuLi, THF
-40 °C, 1 h
S
S
S
S
2) MeSSMe
SMe
31
34,87%
Scheme 4. Fused oligothiophenes producing only deprotonation products with n-BuLi.
(for fused thiophenes). If for kinetic reasons discussed above,
ring-opening cannot occur or is slow then alternative reactions
dominate. In spite of 17 being structurally similar to dithieno[3,2-
b:20,30-d]thiophene 30 has highly kinetically acidic
a
-protons and is
instantly deprotonated with BuLi at low temperatures.13

K. Chernichenko et al. / Tetrahedron 67 (2011) 6812e6818
6815
Table 2
Influence of solvent nature on ring-opening rate with n-butyllithium at ꢀ80 ꢁCa
Entry Substrate Solvent
Time, Electrophilic Products distribution,
min
reagent
yield, % (compound)
1
2
3
4
5
6
8
8
13
13
13
13
THF
Et2O
THF
THF
THF
THFeHMPT 15
¼8:1
15
15
15
45
60
H2O
PMPCHO
H2O
H2O
H2O
98 (10a); 2 (8)
5.9 (10b); 1.4 (11)
35.8 (20); 8.6 (21)
60 (20); 10 (21)
67 (20); 14 (21)
82 (20); 10 (21)
H2O
a
Products distribution was measured by 1H NMR and was referenced to pure
samples.
thiophene ring cleavages were observed. Due to the insolubility of
circulene 16, the ring-opening was performed at room temperature
to shorten the duration of the heterogeneous reaction. In-
terestingly, using 50-fold excess of MeLi a D4h-symmetric tetra-
lithium intermediate was detected as the major product by 13C
NMR measurements (Fig.1). However treatment of the sample with
proton source (methanol) provided an inseparable complex mix-
ture of products. Quenching the reaction mixture (10 equiv of MeLi)
with dimethyl disulfide gave symmetrical 3- and 4-fold products 25
and 26 in 30% and 21% yields, respectively (Scheme 4). It should be
noted, that this is the first reported reaction of 16.
13
Fig. 1. Section plot of the C NMR spectrum (100 MHz, THF-d8, 25 ꢁC) of the sample
obtained by dissolving sulflower 16 in a 50-fold excess of MeLi/hexane and adding
THF-d8. Computed structure of the symmetric tetralithium intermediate is shown
above the spectrum. The signals of the less symmetric trilithium intermediate are less
intensive and probably merged into the background.
Ring-opening:
3. Conclusions
Fast
Slow
No
S
S
In summary, fused oligothiophenes react with organolithiums
to produce ring-opened products as a result of thiophilic attack by
the organolithium species. The reaction proceeds very fast at low
temperature in readily coordinating solvents, such as THF. When
competitive deprotonation of the substrate is possible n-BuLi
shows the highest selectivity to ring-opening among the tested
organolithium reagents. The decrease of the organolithium species
basicity is a driving force of the reaction and defines the ring-
opening regioselectivity for non-symmetrical substrates. The co-
ordination of organolithiums by the neighboring sulfur atom is
suggested to play a key role in the ring-opening mechanism, thus
restricting the scope of substrates to fused thieno[2,3-b]thiophenes
and some thieno[3,2-b]thiophenes, for example, 17. For highly
fused oligothiophenes multiple ring-openings are possible as was
shown for octathio[8]circulene 16. Thiophilic ring-opening of 16 is
the first chemical transformation of this unique molecule.
S
S
S
S
S
Li
17
H
3R2
31
R1
R1
Li
R3
Li
R
R1
R2
R2
R3
Fig. 2. Possible reaction intermediate, facilitating RLi attack on sulfur.
Fig. 3. Transition state for the ring-opening reaction of MeLi and dithiophene 13
computed at the B3LYP/6-311þG(d,p) level of theory.
4. Experimental section
4.1. General experimental
The aggregation of organolithiums and its complexation with
the solvent essentially influence its reactivity. We supposed that
complexation between RLi and oligothiophenes plays a key role in
thiophilic ring-opening. Therefore we varied the nature of the
solvent to study its effect. We found, that when dithienothiophene
8 was treated with BuLi in the less polar diethyl ether instead of
THF, (Table 2, entry 1), the conversion drops to less than 8% and
ring-opening selectivity was lost (Table 1, entry 2). For the less
reactive 13 a 45% conversion is achieved in THF (entry 3) and 92%
in 8:1 THFeHMPT mixture in 15 min (entry 6). Thus, well
coordinating and polar solvents promote ring-opening reaction.
We studied also the reaction of organolithiums with the recently
synthesized sulflower 16, the first fully thiophenic circulene.3 Due
to the unique structure of this molecule it was difficult to propose
any reactions for sulflower. Therefore the unique molecule de-
mands unique reactions. We observed here for the first time the
possibility of chemical transformation of sulflower. Multiple
1H and 13C NMR spectra were referenced to solvent. Column
chromatography was performed on silica gel (63e200 mesh).
Melting points are uncorrected. THF and Et2O were freshly distilled
from the sodium-benzophenone ketyl. HMPT, 2,2,6,6-
tetramethylpiperidine, and dimethyl disulfide were distilled from
CaH2. The following organolithiums were used: n-BuLi as 1.6 or
2.5 M solution in hexane(s), s-BuLi as 1.6 M solution in cyclohexane,
t-BuLi as 1.6 M solution in pentane, MeLi as 1.6 M solution in diethyl
ether, PhLi as 2.0 M solution in dibutyl ether.
Starting oligothiophenes were prepared as described pre-
viously: dithieno[2,3-b:30,20-d]thiophene 8,9 [1]benzothieno[2,3-b]
[1]benzothiophene 13,15 [1]benzothieno[3,2-b][1]benzothiophene
31,16 thieno[3,2-b]thieno[20,30:4,5]thieno[3,2-d]thiophene 15,4b [1]
benzothieno[20,30:4,5]thieno[3,2-b][1]benzothiophene 17,17 [1]
benzothieno[30,20:4,5]thieno[2,3-b][1]benzothiophene 14,7 sul-
flower 16.3a

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K. Chernichenko et al. / Tetrahedron 67 (2011) 6812e6818
4.1.1. Ring-opening of dithieno[2,3-b:30,20-d]thiophene 8. To a pre-
cooled solution of dithieno[2,3-b:30,20-d]thiophene (196 mg,
1 mmol) in THF (Et2O was used instead of THF in several experi-
ments) (5 mL) organolithium (1.1 mmol) solution was added
at ꢀ80 ꢁC. Mixture was stirred at the same temperature and after
15, 45, and 60 min 1 mL samples were taken and poured into 1 mL
of 1 M aq HCl, extracted with 3ꢂ1 mL of dichloromethane and or-
ganic extracts were dried in vacuum. 1H NMR spectroscopic anal-
ysis showed that in the case of n-, tert-, sec-butyllithiums and
methyllithium the ratio of dithienothiophene to ring-opening
product was unchanged among samples taken after different
times, indicating that conversion was full within 15 min. Dithie-
nothiophene was formed as a result of dithienothienyllithium back
protonation, this was evident by formation of dithienothien-2-yl
derivatives when non-proton electrophiles were used. Pure sam-
ples of 10deg were isolated by the column chromatography (silica
gel, hexane).
(196 mg, 1 mmol) in THF (5 mL) n-butyllithium (1.1 mmol) solution
was added at ꢀ80 ꢁC. After stirring for additional 15 min dimethyl
disulfide (122 mg, 1.3 mmol) was added via syringe. Cooling bath
was removed and reaction was allowed to warm to room temper-
ature, quenched with water (10 mL), and extracted with dichloro-
methane (3ꢂ2 mL). Organic extracts were combined, passed
through short column (silica gel, 5 mL, dichloromethane) and
rotary evaporated. Volatile byproducts and starting materials
(dimethyl disulfide, butyl methyl sulfide) were removed in vacuum
(1 Torr, 50 ꢁC) to give target product as residual yellowish oil
(285 mg, 95%). dH (360 MHz, CDCl3) 0.80e0.89 (m, 3H), 1.25e1.39
(m, 2H), 1.43e1.55 (m, 2H), 2.39 (s, 3H), 2.71 (t, J 7.1 Hz, 2H), 7.19 (t, J
4.9 Hz, 2H), 7.32 (d, J 5.3 Hz, 1H), 7.35 (d, J 5.3 Hz, 1H); dC (75 MHz,
CDCl3) 13.5, 21.5, 21.5, 31.2, 38.2, 125.7, 126.5, 129.8, 130.1, 132.1,
133.9, 137.9, 139.3; nmax (liquid film) 660, 673, 713, 846, 876, 908,
968, 1010, 1331, 1417, 1431, 1462, 2920, 2955, 3100 cmꢀ1; HRESI-
TOFþ: MNaþ, found 323,0015, requires C13H16S4Naþ 323,0027.
4.1.1.1. 2-(Methylsulfanyl)-3,30-bithiophene (10d)18. Yield 108 mg
(51%) as colorless oil; dH (300 MHz CDC13) 2.43 (s, 1H), 7.18 (d, J
5.5 Hz, 1H), 7.29 (d, J 5.5 Hz, 1H), 7.36 (dd, J 5.0, 3.0 Hz, 1H), 7.51 (dd,
J 5.0, 1.4 Hz, 1H), 7.66 (dd, J 3.0, 1.4 Hz, 1H); dC (75 MHz, CDCl3) 21.2,
122.6, 125.1, 126.3, 127.7, 129.1, 131.2, 136.0, 137.6; nmax (liquid film)
658, 724, 757, 782, 845, 968, 1010, 1072, 1188, 1333, 1393, 1418,
1428, 3101 cmꢀ1; HRESI-TOFþ: MNaþ, found 234.9662, requires
C9H8S3Naþ 234.9680.
4.1.1.7. 2-(Butylsulfonyl)-20-(methylsulfonyl)-3,30-bithiophene
(12). Compound 10c (150 mg, 0.5 mmol) was dissolved in acetic
acid (10 mL) and hydrogen peroxide (30% in water, 340 mg, 3 mmol)
was added and stirred for 7 days. Hydrogen peroxide (340 mg) was
additionally added and stirring was continued for another 7 days.
Water (50 mL) was added, the product was filtered and recrystal-
lized from acetic acid to give 12 as fine needles (300 mg, 82%);
mp¼164e166 ꢁC; dH (400 MHz, CDCl3) 0.91 (t, J 7.4 Hz, 2H),
1.35e1.48 (sxt, J 7.4 Hz, 2H), 1.68e1.80 (m, 2H), 3.085e3.15 (t, J
8.0 Hz, 2H), 3.13 (s, 3H), 7.15 (d, J 5.1 Hz, 1H), 7.18 (d, J 5.1 Hz, 1H),
7.71 (d, J 5.1 Hz, 1H), 7.73 (d, J 5.1 Hz, 1H); dC (100 MHz, CDCl3) 13.4,
21.3, 24.5, 45.8, 57.1, 131.0, 131.3, 131.8, 131.9, 137.6, 137.8, 137.8,
138.9; nmax (liquid film) 754, 772, 861, 966, 1042, 1084, 1099, 1135,
1303, 1313, 3109 cmꢀ1; HRESI-TOFþ: MNaþ, found 386.9844, re-
quires C13H16O4S4Naþ 386.9824; X-ray data are available from
Cambridge Crystallographic Data Center, http://www.ccdc.cam.a-
c.uk/products/csd/request/, deposition number 813592.
4.1.1.2. 2-(Butylsulfanyl)-3,30-bithiophene (10a). Yield 214 mg
(95%) as colorless oil; dH (300 MHz, CDCl3) 0.86 (t, J 7.3 Hz, 3H)
1.26e1.44 (m, 2H) 1.48e1.62 (m, 2H) 2.74e2.83 (m, 2H) 7.21 (d, J
5.2 Hz, 1H) 7.32 (d, J 5.5 Hz, 1H) 7.36 (dd, J 5.0, 3.0 Hz, 1H) 7.53 (dd, J
5.1, 1.2 Hz, 1H) 7.70 (dd, J 3.0, 1.4 Hz, 1H); dC (75 MHz, CDCl3) 13.6,
21.6, 31.2, 38.1, 122.8, 125.0, 126.9, 127.9, 129.1, 129.4, 136.2, 139.0;
nmax (liquid film) 723, 783, 846, 1008, 1071, 1333, 1462, 2926,
2955, 3102 cmꢀ1; HRESI-TOFþ: MNaþ, found 277.0160, requires
C12H14S3Naþ 277.0150.
4.1.1.8. [20-(Butylthio)-3,30-bithien-2-yl](4-methoxyphenyl)meth-
anol (10b). To a precooled solution of dithieno[2,3-b:30,20-d]thio-
phene (98 mg, 0.5 mmol) in THF (2.5 mL) n-butyllithium
(0.51 mmol, 0.32 mL 1.6 M) solution was added at ꢀ80 ꢁC. After
stirring for additional 15 min 4-methoxybenzaldehyde (80 mg,
0.58 mmol) in THF (1 mL) was added via syringe. Cooling bath was
removed and reaction was allowed to warm to room temperature,
treated with 1 mL of aq NH4Cl and hexane (5 mL). Organic extracts
were combined, passed through short column (silica gel, 5 mL,
dichloromethane) and rotary evaporated. The residual oil was
chromatographed (50 mL silica gel, hexaneeethyl acetate 4:1) to
give 10b as yellowish oil (124 mg, 63%) unstable in air on prolonged
storage. dH (300 MHz, CDCl3) 0.82 (t, J 7.1 Hz, 3H), 1.27 (m, 2H), 1.45
(m, 2H), 2.59 (t, J 7.4 Hz, 2H), 2.84 (dd, J 3.3, 1.1 Hz, 1H), 5.97 (d, J
3.0 Hz, 1H), 6.81 (d, J 8.5 Hz, 2H), 6.96 (d, J 5.5 Hz, 2H), 7.23 (d, J
8.2 Hz, 3H), 7.28 (d, J 5.2 Hz, 1H), 7.31 (dd, J 5.2, 1.1 Hz, 1H); dC
(75 MHz, CDCl3) 13.5, 21.5, 31.1, 37.8, 55.2, 69.9, 113.6, 124.4, 127.0,
127.2, 129.2, 130.0, 131.4, 133.0, 135.4, 139.8, 145.3, 159.0; nmax
(liquid film) 716, 831, 851, 1030, 1172, 1245, 1509, 1610, 2955, 3424
4.1.1.3. 2-(tert-Butylsulfanyl)-3,30-bithiophene (10f). Yield 172 mg
(68%) as colorless oil; dH (300 MHz, CDCl3) 1.20 (s, 9H), 7.27 (d, J
5.6 Hz, 1H), 7.33 (dd, J 5.1, 3.0 Hz, 1H), 7.41 (d, J 5.6 Hz, 1H), 7.56 (d, J
5.1 Hz, 1H), 7.74 (d, J 3.0 Hz, 1H); dC (75 MHz, CDCl3) 30.6, 49.0,123.3,
124.6, 126.6, 128.5, 129.0, 129.3, 136.7, 142.4; nmax (liquid film) 726,
784, 847, 1162, 1363, 1455, 2958, 3103 cmꢀ1; HRESI-TOFþ: MNaþ,
found 277.0139, requires C12H14S3Naþ 277.0150.
4.1.1.4. 2-(Butan-2-ylsulfanyl)-3,30-bithiophene (10e). Yield 51 mg
(20%) as colorless oil; dH (300 MHz, CDCl3) 0.92 (t, J 7.3 Hz, 3H), 1.18
(d, J 6.9 Hz, 3H),1.45 (sxt, J 7.1 Hz,1H),1.59 (sxt, J 7.3 Hz,1H), 2.94 (sxt,
J 6.6 Hz, 1H), 7.22 (d, J 5.6 Hz, 1H), 7.34 (d, J 5.3 Hz, 1H), 7.34 (dd, J 5.1,
3.0 Hz, 1H), 7.55 (dd, J 4.9, 1.1 Hz, 1H), 7.72 (dd, J 3.0, 1.1 Hz, 1H); dC
(75 MHz, CD3COCD3) 12.0, 21.0, 30.4, 49.7, 124.5, 126.6, 128.6, 129.4,
129.8, 130.8, 137.8, 142.0; nmax (liquid film) 725, 783, 846, 1007, 1334,
1376, 1454, 2922, 2960, 3104 cmꢀ1; HRESI-TOFþ: MNaþ, found
277.0133, requires C12H14S3Naþ 277.0150.
4.1.1.5. 2-(Phenylsulfanyl)-3,30-bithiophene (10g). Yield 90 mg
(33%) as colorless oil; dH (300 MHz, CDCl3) 7.12e7.19 (m, 3H),
7.22e7.30 (m, 2H), 7.32 (dd, J 4.9, 3.0 Hz, 1H), 7.35 (d, J 5.5 Hz, 1H),
7.44 (dd, J 4.9, 1.4 Hz, 1H), 7.51 (d, J 5.5 Hz, 1H), 7.60 (dd, J 3.0, 1.4 Hz,
1H); dC (75 MHz, CDCl3) 123.3, 124.2, 125.2, 125.8, 126.4, 127.7, 129.1,
129.4, 129.9, 135.6, 138.6, 142.1; nmax (liquid film) 686, 727, 785, 846,
1022, 1076, 1260, 1438, 1475, 1578 cmꢀ1; HRESI-TOFþ: MNaþ, found
296.9837, requires C14H10S3Naþ 296.9837.
(br) cmꢀ1
;
HRESI-TOFþ: MNaþ, found 413.0651, requires
C20H22O2S3Naþ 413.0674.
4.1.1.9. Bisthieno[2,3-b:30,20-d]thiophen-2-yl(4-methoxyphenyl)
methanol (11). 2,2,6,6-Tetramethylpiperidine (80 mg, 0.56 mmol)
in THF (2 mL) was treated with n-butyllithium (0.32 mL, 1.6 M,
0.51 mmol) at 0 ꢁC, stirred for 15 min and cooled to ꢀ80 ꢁC.
Dithieno[2,3-b:30,20-d]thiophene (98 mg, 0.5 mmol) in THF (0.5 mL)
was added via syringe and stirred for 10 min, then 4-
methoxybenzaldehyde (80 mg, 0.58 mmol) in THF (1 mL) was
added via syringe. The cooling bath was removed, allowed to warm
4.1.1.6. 2-(Butylsulfanyl)-20-(methylsulfanyl)-3,30-bithiophene
(10c). To a precooled solution of dithieno[2,3-b:30,20-d]thiophene

K. Chernichenko et al. / Tetrahedron 67 (2011) 6812e6818
6817
to room temperature and treated with 1 mL of aq NH4Cl and hexane
(5 mL). Organic phase was separated, volatiles evaporated, and the
residue recrystallized from 95% ethanol (4 mL) to give 11 as yel-
lowish crystals (120 mg, 72%) unstable in air on prolonged storage.
Mp 143e145 ꢁC; dH (300 MHz, CDCl3) 2.47 (d, J 4.1 Hz, 1H), 3.81 (s,
3H), 6.04 (d, J 3.9 Hz, 1H), 6.91 (d, J 8.8 Hz, 2H), 7.10 (d, J 1.1 Hz, 1H),
7.27 (d, J 5.2 Hz, 1H), 7.34 (d, J 5.2 Hz, 1H), 7.40 (d, J 8.79 Hz, 2H); dC
(75 MHz, CDCl3) 55.3, 72.7, 114.0, 116.5, 118.7, 127.6, 127.8, 134.9,
137.5, 138.5, 138.6, 138.2, 151.2, 159.6; nmax (liquid film) 674, 724,
817, 843, 1021, 1172, 1244, 1511, 1608, 3460 (br) cmꢀ1; HRESI-TOFþ:
MNaþ, found 354.9915, requires C16H12O2S3Naþ 354.9892.
4.1.2.4. 2-(Butylsulfanyl)-3-(2-2H)phenyl-1-benzothiophene
(19). From run 4, 36 mg (12%), colorless oil; dH (300 MHz, CDCl3)
0.84 (t, J 7.4 Hz, 3H), 1.33 (sxt, J 7.4 Hz, 2H), 1.49e1.62 (qt, J 7.4 Hz,
2H), 2.83 (t, J 7.4 Hz, 2H), 7.27e7.37 (m, 2H), 7.38e7.58 (m, 5H),
7.74e7.83 (m, 1H); dC (75 MHz, CDCl3) 13.5, 21.6, 31.5, 36.9, 121.7,
122.9, 124.4, 124.5, 127.7, 128.2, 128.3, 130.2, 133.7, 134.7, 139.1,
139.8, 140.1; nmax (liquid film) 669, 733, 749, 735, 1430, 1461, 2931,
2971, 3054 cmꢀ1; HRESI-TOFþ: MNaþ, found 322.0791, requires
C18H17DS2Naþ 322.0805.
4.1.3. Ring-opening of fused oligothiophenes 14e17. 4.1.3.1. 3-[3-
(Butylthio)thien-2-yl]thieno[3,2-b]thiophene (24). Compound 15
was treated with n-BuLi in a manner similar to previously described
for 8. For all of the samples taken after 15, 45, and 90 min and
quenched with 1 M aq HCl ring-opening conversion constitutes 23%.
4.1.2. Ring-opening of [1]benzothieno[2,3-b][1]benzothiophene 13. [1]
Benzothieno[2,3-b][1]benzothiophene (13) was not fully spectro-
scopically characterized previously. dH (400 MHz, CDCl3) 7.34e7.44
(m, 2H), 7.53 (td, J 7.6, 1.1 Hz, 2H), 7.89 (d, J 7.7 Hz, 2H), 8.32 (d, J
7.7 Hz, 2H); dC (100 MHz, CDCl3) 121.1, 123.2, 123.9, 124.8, 133.4,
135.0, 139.8, 143.5.
Ring-openings of 13 were performed with n-butyllithium sim-
ilar to 8. Products distribution was defined with 1H NMR. As shown
in table below ring-opening rate is slower comparing to 8 and
conversion is growing with time. Quenching with D2O showed no
deprotonation (ortho-lithiation) of 13, the only compound in re-
action mixture except ring-opening products was starting 13. Ad-
dition of HMPT substantially increases ring-opening rate. Pure
samples of 18e21 were isolated by column chromatography (hex-
ane, silica gel).
The rest is starting 15 as result of a-deprotonation-back protonation.
Pure 24 was separated from 15 by column chromatography (hexane,
silica gel). Colorless oil; darkening when stored long in air. dH
(400 MHz, CDCl3) 0.88 (t, J 7.3 Hz, 3H),1.36e1.45 (m, 2H),1.59 (quint,
J 7.4 Hz, 2H), 2.89 (t, J 7.3 Hz, 2H), 7.15 (d, J 5.1 Hz,1H), 7.32 (d, J 5.3 Hz,
1H), 7.34 (d, J 5.1 Hz, 1H), 7.42e7.50 (m, 1H), 7.95 (d, J 1.3 Hz, 1H); dC
(75 MHz, CDCl3) 13.6, 21.8, 31.5, 35.3, 119.7 123.4, 125.4, 126.5, 127.6,
129.4, 131.0, 133.7, 138.7, 139.3; nmax (liquid film) 669, 719, 808, 874,
920, 1082, 1184, 1309, 1336, 1463, 2925, 2954, 3101 cmꢀ1; HRESI-
TOFþ: MNaþ, found 332.9871, requires C14H14S4Naþ 332.9871.
4.1. 3. 2. 2-(Butylsulfanyl)-3, 30-bi-1-benzothiophene
(22). Compound 14 (296 mg,1 mmol) in THF (5 mL) was treated with
n-BuLi (1.1 mmol) at ꢀ80 ꢁC and stirred additionally for 1 h. Methanol
(0.5 mL) was added, reaction was allowed to warm to room temper-
ature and volatiles removed. Residue was treated with aqueous 1 M
HCl and dichloromethane (5 mL), organic phase was separated,
flashed through silica gel (5 mL), and evaporated to yield 22 (354 mg,
100%) as colorless oil; dH (400 MHz, CDCl3) 0.83 (t, J 7.3 Hz, 3H),
1.24e1.39 (m, 2H), 1.50e1.65 (m, 2H), 2.80e2.95 (m, 2H), 7.25e7.46
(m, 5H), 7.49e7.54 (m, 1H), 7.55 (s, 1H), 7.86 (d, J 8.1 Hz, 1H), 8.00 (d, J
8.1 Hz,1H); dC (100MHz, CDCl3) 13.5, 21.6, 31.5, 36.9,121.9,122.8,123.2,
123.6, 124.2, 124.5, 124.6, 126.7, 130.2, 132.8, 136.2, 138.6, 140.0; nmax
Run
Solvent
Time,
min
Electrophilic
reagent
Yield of 18
or 20
Yield of
19 or 21
1
2
3
4
5
THF
THF
THF
THF
15
45
60
60
15
H2O
H2O
H2O
D2O
H2O
35.8%
60%
67%
67%
82%
8.6%
10%
14%
14%
10%
THFeHMPT¼8:1
4.1.2.1. 3-[2-(Butylsulfanyl)phenyl]-1-benzothiophene (20). From
run 3, 176 mg (59%), colorless oil; dH (300 MHz, CDCl3) 0.85 (t, J
7.3 Hz, 3H), 1.26e1.41 (m, 2H), 1.46e1.60 (m, 2H), 2.77 (t, J 7.3 Hz,
2H), 7.22e7.30 (m, 1H), 7.30e7.48 (m, 6H), 7.50e7.56 (m, 1H),
7.89e7.96 (m, 1H); dC (75 MHz, CDCl3) 13.6, 22.0, 30.8, 32.7, 122.6,
123.2, 124.0, 124.3, 125.0, 125.0, 127.5, 128.3, 130.9, 135.4, 136.0,
137.7, 138.7, 139.8; nmax (liquid film) 692, 730, 759, 828, 1424, 1461,
2926, 2955, 3054 cmꢀ1; HRESI-TOFþ: MNaþ, found 321.0722, re-
quires C18H18S2Naþ 321.0742.
(liquid film) 729, 754, 1251, 1416, 1428, 1454, 2925, 2954, 3056 cmꢀ1
;
HRESI-TOFþ: MNaþ, found 377.0453, requires C20H18S3Naþ 377.0463.
4.1.3.3. 2,20-Bis(methylsulfanyl)-3,30-bi-1-benzothiophene
(23). Compound 23 was prepared analogously to 22. Compound 14
was treated with MeLi similarly to previously described. Dimethyl
disulfide (141 mg, 1.5 mmol) in THF (1 mL) was added instead of
methanol. After warming to room temperature organic phase was
evaporated, treated with water (5 mL) and dichloromethane (5 mL).
Organic phase was separated, solvent evaporated, and residue pu-
rified by column chromatography (hexaneeethyl acetate¼20:1,
silica gel) to yield 23 (286 mg, 80%) as yellow crystals,
mp¼148e150 ꢁC; dH (400 MHz, CDCl3) 2.53 (s, 6H), 7.21e7.32 (m,
4H), 7.35 (t, J 6.7 Hz, 2H), 7.86 (d, J 7.8 Hz, 2H); dC (100 MHz, CDCl3)
19.8, 121.9, 122.7, 124.2, 124.5, 129.8, 138.8, 139.4, 139.6; nmax (liquid
film) 730, 770, 970, 1380, 1470, 2850, 2980 cmꢀ1; HRESI-TOFþ:
MNaþ, found 380.9872, requires C18H14S4Naþ 380.9876.
4.1.2.2. 2-(Butylsulfanyl)-3-phenyl-1-benzothiophene (21). From
run 3, 33 mg (11%), colorless oil; dH (300 MHz, CDCl3) 0.84 (t, J
7.4 Hz, 3H), 1.33 (sxt, J 7.4 Hz, 2H), 1.55 (qt, J 7.4 Hz, 2H), 2.84 (t, J
7.3 Hz, 2H), 7.27e7.37 (m, 2H), 7.38e7.60 (m, 6H), 7.75e7.83 (m,
1H); dC (75 MHz, CDCl3) 13.5, 21.6, 31.4, 36.9, 121.7, 122.9, 124.4,
124.4, 127.7, 128.3, 130.2, 133.7, 134.7, 139.1, 139.8, 140.1; nmax (liquid
film) 692, 730, 758, 830, 1424, 1463, 2926, 2955, 3053 cmꢀ1; HRESI-
TOFþ: MNaþ, found 321.0719, requires C18H18S2Naþ 321.0742.
4.1.3.4. 2-[2-(Butylsulfanyl)phenyl]thieno[3,2-b][1]benzothio-
phene (27). Compound 17 (1 mmol, 296 mg) in 5 mL THF was
treated with n-BuLi (2.5 mmol) at 0 ꢁC and stirred additionally for
2 h at room temperature. Methanol (0.5 mL) was added and vola-
tiles evaporated. Residue was taken in dichloromethaneeaqueous
NH4Cl, organic phase was separated, dried over sodium sulfate,
evaporated, and purified by column chromatography (hex-
aneeethyl acetate¼20:1, silica gel) to yield 32 (149 mg, 42%) as
colorless oil; dH (400 MHz, CDCl3) 0.91 (t, J 7.3 Hz, 3H) 1.37e1.50 (m,
2H) 1.63 (quint, J 7.4 Hz, 2H) 2.89 (t, J 7.5 Hz, 2H) 7.20e7.27 (m, 1H)
4.1.2.3. 3-[2-(Butylsulfanyl)phenyl](2-2H)-1-benzothiophene
(18). From run 4, 185 mg (62%), colorless oil; dH (300 MHz, CDCl3)
0.84 (t, J 7.3 Hz, 3H), 1.24e1.41 (m, 2H), 1.44e1.60 (m, 2H), 2.76 (t, J
7.4 Hz, 2H), 7.21e7.29 (m, 1H), 7.29e7.47 (m, 5H), 7.49e7.55 (m, 1H),
7.88e7.95 (m, 1H); dC (75 MHz, CDCl3) 13.6, 22.0, 30.8, 32.7, 122.6,
123.2, 124.0, 124.3, 125.0, 127.5, 128.3, 130.9, 135.4, 135.9, 137.7,
138.8, 139.7; nmax (liquid film) 668, 730, 751, 763, 1417, 1456, 2924,
2955, 3054 cmꢀ1; HRESI-TOFþ: MNaþ, found 322.0804, requires
C18H17DS2Naþ 322.0805.

6818
K. Chernichenko et al. / Tetrahedron 67 (2011) 6812e6818
7.31e7.39 (m, 2H) 7.40e7.46 (m, 2H) 7.48e7.52 (m, 1H) 7.51 (s, 1H)
7.83e7.91 (m, 2H); dC (100 MHz, CDCl3) 13.6, 22.1, 30.7, 33.2, 120.6,
121.0, 123.8, 124.4, 124.6, 125.4, 128.2, 128.6, 131.1, 132.8, 134.2,
136.8, 137.6, 142.2, 144.2; oil; nmax (liquid film) 730, 760, 840, 1080,
1260, 1350, 1450, 1470, 1590, 2870, 2970, 3050 cmꢀ1; HRESI-TOFþ:
MNaþ, found 377.0459, requires C20H18S3Naþ 377.0463.
For ring-opening of 17 two alternative structures are possible as
result of butyllithium attack either on central (28) or side sulfur
atom (27), which are hardly distinguished by ordinary NMR. The
correct structure 27 was signed based on COSY 1He1H and HMBC
correlations.
Supplementary data
NMR spectra and computational details are available. Supple-
mentary data associated with this article can be found, in the online
version, at doi:10.1016/j.tet.2011.06.082.
References and notes
ꢀ
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4481e4483; (b) Miyasaka, M.; Rajca, A.; Pink, M.; Rajca, S. J. Am. Chem. Soc.
2005, 127, 13806e13807.
4.1.4. Ring-openings of sulflower 16. To a suspension of sulflower 16
(224 mg, 0.5 mmol) in 20 mL of THF MeLi (5 mmol) was added at
0 ꢁC. The reaction was additionally stirred at room temperature for
2 h and dimethyl disulfide (940 mg, 10 mmol in 1 mL THF) was
added and additionally stirred overnight. Volatiles were removed
in vacuum and residue taken in dichloromethaneeH2O, organic
phase was separated, dried over sodium sulfate, solvent evaporated
and volatiles removed in vacuum. Column chromatography of the
residue (hexaneeethyl acetate¼20:1, silica gel) gave 25 (95 mg,
30%) and 26 (73 mg, 21%).
3. (a) Chernichenko, K. Y.; Sumerin, V. V.; Shpanchenko, R. V.; Balenkova, E. S.;
Nenajdenko, V. G. Angew. Chem., Int. Ed. 2006, 45, 7367e7370; (b) Cherni-
chenko, K. Y.; Balenkova, E. S.; Nenajdenko, V. G. Mendeleev Commun. 2008,
171e179; (c) Bukalov, S. S.; Leites, L. A.; Lyssenko, K. A.; Aysin, R. R.; Korlyukov,
A. A.; Zubavichus, J. V.; Chernichenko, K. Y.; Balenkova, E. S.; Nenajdenko, V. G.;
Antipin, M. Y. J. Phys. Chem. A 2008, 112, 10949e10961; (d) Ivasenko, O.; Ma-
cLeod, J. M.; Chernichenko, K. Y.; Balenkova, E. S.; Shpanchenko, R. V.; Ne-
najdenko, V. G.; Rosei, F.; Perepichka, D. F. Chem. Commun. 2009, 1192e1194;
(e) Dadvand, A.; Cicoira, F.; Chernichenko, K. Y.; Balenkova, E. S.; Osuna, R. M.;
Rosei, F.; Nenajdenko, V. G.; Perepichka, D. F. Chem. Commun. 2008,
5354e5356.
4. (a) Oyaizu, K.; Iwasaki, T.; Tsukahara, Y.; Tsuchida, E. Macromolecules 2004, 37,
1257e1270; (b) Nenajdenko, V. G.; Sumerin, V. V.; Chernichenko, K. Y.; Ba-
lenkova, E. S. Org. Lett. 2004, 20, 3437e3439; (c) Okamoto, T.; Kudoh, K.; Wa-
kamiya, A.; Yamaguchi, S. Chem.dEur. J. 2007, 13, 548e556; (d) Okamoto, T.;
Kudoh, K.; Wakamiya, A.; Yamaguchi, S. Org. Lett. 2005, 7, 5301e5304; (e)
Kienle, M.; Unsinn, A.; Knochel, P. Angew. Chem., Int. Ed. 2010, 49, 4751e4754.
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Scrowston, R. M. Adv. Heterocycl. Chem. 1981, 29, 196e197; (c) Bayh, O.; Awad,
H.; Mongin, F.; Hoarau, C.; Bischoff, L.; Trecourt, F.; Queguiner, G.; Marsais, F.;
Blanco, F.; Abarca, B.; Ballesteros, R. J. Org. Chem. 2005, 70, 5190e5196.
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4.1.4.1. 3,4,6,7,9,10-Hexakis(methylsulfanyl)-1,12-epithiocycloocta
[1,2-c:3,4-c0:5,6-c00:7,8-c000]tetrakisthiophene (25). Mp >300 ꢁC,
decomp.; dH (400 MHz, CDCl3) (s, 3H), 2.36 (s, 3H), 2.48 (s, 3H); dC
(100 MHz, CDCl3) 20.9, 21.1, 22.9, 131.0, 135.2, 136.5, 137.1, 137.1,
137.9,138.0,139.0; nmax (liquid film) 730, 760, 780,1430,1470, 2840,
2890, 3060 cmꢀ1; HRESI-TOFþ: MNaþ, found 656.8228, requires
C24H18S11Naþ 656.8229.
7. Wang, Z.; Zhaoa, C.; Zhaoa, D.; Lia, C.; Zhanga, J.; Wang, H. Tetrahedron 2010, 66,
2168e2174.
4.1.4.2. 1,3,4,6,7,9,10,12-Octakis(methylsulfanyl)cycloocta[1,2-
c:3,4-c0:5,6-c00:7,8-c000]tetrakisthiophene (26). Mp >300 ꢁC, decomp.;
dH (400 MHz, CDCl3) 2.36 (s, 3H); dC (100 MHz, CDCl3) 21.0, 136.0,
137.3; nmax (liquid film) 730.0, 763.5, 780.0, 1378.0, 1430.0, 1480.2,
2820.0, 2910.4, 3050 cmꢀ1; HRESI-TOFþ: MHþ, found 696.8599,
requires C24H24S12Hþ 696.8599.
8. (a) Webert, J.-M.; Cagniant, D.; Cagniant, P.; Kirsch, G.; Weber, J.-V. J. Heterocycl.
Chem. 1983, 20, 61e64; (b) Gronowitz, S.; Hallberg, A.; Frejd, T. Tetrahedron
1979, 35, 2607e2610; (c) Onyamboko, N. V.; Weber, R.; Fauconnier, A.; Renson,
M. Bull. Soc. Chim. Belg. 1983, 92, 53e60; (d) Litvinov, V. P.; Konyaeva, I. P.;
Gol’dfarb, Y. L. Russ. Chem. Bull. 1976, 25, 466; (e) Iteke, F. B.; Christiaens, L.;
Renson, M. Tetrahedron 1976, 32, 689e691; (f) Gronowitz, S.; Konar, A.; Litvinov,
V. P. Russ. Chem. B. 1981, 30, 1089e1093; (g) Micetich, R. G. Can. J. Chem. 1970,
48, 2006e2015; (h) Caton, M. P. L.; Jones, D. H.; Slack, R.; Wooldridge, K. R. H. J.
Chem. Soc. 1964, 446e451; (i) Gol’dfarb, Y. L.; Kalik, M. A.; Zav’yalova, V. K. Russ.
Chem. Bull. 1985, 34, 145e150; (j) James, F. C.; Krebs, H. D. Aust. J. Chem. 1982, 35,
393e404.
4.1.5. Deprotonation of 31. 1-(Methylsulfanyl)[1]benzothieno[3,2-b]
[1]benzothiophene (34). Compound 18 (240 mg, 1 mmol) in THF
(5 mL) was treated with 1.1 mmol of n-BuLi (solution in hexane) at
ꢀ40 ꢁC and stirred for 1 h at this temperature. Dimethyl disulfide
(141 mg, 1.5 mmol) as solution in THF (1 mL) was added and the
reaction was allowed to warm to room temperature. THF was re-
moved in vacuo, residue was treated with aqueous NH4Cl and
dichloromethane (5 mL). Organic phase was separated, washed with
water, and evaporated. Separation by column chromatography gave
250 mg (87%) of 34 as white powder; mp¼141 ꢁC; dH (400 MHz,
CDCl3) 2.67 (s, 3H), 7.38e7.50 (m, 4H), 7.77 (dd, J 7.8, 1.0 Hz,1H), 7.93
(d, J 7.8 Hz, 2H); dC (100 MHz, CDCl3) 16.9, 119.5, 121.6, 121.7, 124.0,
124.5, 124.9, 124.9, 125.0, 125.1, 125.6, 132.9, 133.0, 133.2, 133.8; nmax
9. Nenajdenko, V. G.; Gribkov, D. V.; Sumerin, V. V.; Balenkova, E. S. Synthesis
2003, 124e128.
10. X-ray data are available from Cambridge Crystallographic Data Centre,
http://www.ccdc.cam.ac.uk/products/csd/request/, under deposition number
813592.
11. Similar strong tendency of sec-butyllithium to deprotonation was reported by
Belly, et al. Ref. 6a.
12. (a) Tedjamulia, M. L.; Tominaga, Y.; Castle, R. N.; Lee, M. L. J. Heterocycl. Chem.
1983, 20, 861e866; (b) Katritzky, A. R.; Perumal, S. J. Heterocycl. Chem. 1990, 27,
1737e1740; (c) Tye, H.; Eldred, C.; Wills, M. J. Chem. Soc., Perkin Trans. 1 1998,
457e466.
13. (a) Kim, O.-K.; Fort, A.; Barzoukas, M.; Blanchard-Desce, M.; Lehn, J.-M. J. Mater.
Chem. 1999, 9, 2227e2232; (b) Osterod, F.; Peters, L.; Kraft, A.; Sano, T.; Mor-
rison, J. J.; Feeder, N.; Holmes, A. B. J. Mater. Chem. 2001, 11, 1625e1633.
14. Predicted pKa for benzothien-2-yllithium, thien-2-yllithium, thien-3-yllithium,
and phenyllithium in DMSO are 32.0, 33.5, 39.0, and 44.7, respectively: Shen,
K.; Fu, Y.; Li, J.-N.; Liu, L.; Guo, Q.-X. Tetrahedron 2007, 63, 1568e1576.
15. Voronkov, M. G.; Udre, V. E. Chem. Heterocycl. Compd. 1968, 33e36.
16. Kosata, B.; Kozmik, V.; Svoboda, J. Collect. Czech. Chem. Commun. 2002, 67,
645e664.
(liquid film) 730, 759, 780, 1340, 1378, 1430, 1480, 2820, 2890 cmꢀ1
;
HRESI-TOFþ: MNaþ, found 308.9837, requires C15H10S3Naþ 308.9837.
Acknowledgements
17. Schroth, W.; Hintzsche, E.; Viola, H.; Winkler, R.; Klose, H.; Boese, R.; Kempe, R.;
Sieler, J. Chem. Ber. 1994, 127, 401e408.
18. Shevchenko, N. E.; Karpov, A. S.; Zakurdaev, E. P.; Nenajdenko, V. G.; Balenkova,
E. S. Chem. Heterocycl. Compd. 2000, 36, 137e143.
Financial support from the Russian Foundation for Basic Re-
search (Grant N 09-03-00629-a) and Chemistry GCOE Program of
Tokyo Institute of Technology is gratefully acknowledged.