Efficient synthesis of trimethylsilyl-substituted dithieno[2,3-b:3′, 2′-d]thiophene, tetra[2,3-thienylene] and hexa[2,3-thienylene] from substituted [3,3′]bithiophenyl

Article abstract of DOI:10.1055/s-2007-985582

Efficient synthetic procedures for the preparation of β-trithiophenes (dithieno[2,3-b:3′,2′-d]thiophene) and two macrocyclic compounds, tetra[2,3-thienylene] and hexa[2,3-thienylene] bearing trimethylsilyl (TMS) groups from 2,2′-dibromo-5,5′-bistrimethylsilanyl[3,3′] bithiophenyl are reported. The UV-Vis spectra property and crystal structures of these macrocyclic oligothiophenes are described. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-985582

2390
LETTER
Efficient Synthesis of Trimethylsilyl-Substituted Dithieno[2,3-b:3¢,2¢-d]thio-
phene, Tetra[2,3-thienylene] and Hexa[2,3-thienylene] from Substituted
[3,3¢]Bithiophenyl
E
a
fficient
S
ynthesis
a
of
b
-Trithi
n
ophene
s
and
g
M
acrocyclic
g
Compoundsuang Wang,a Zhihua Wang,a Dongfeng Zhao,a Zhen Wang,a Yangxiang Cheng,*b Hua Wang*a
Key Lab for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004, P. R. of China
b
Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. of China
Fax +86(378)3881358; E-mail: hwang@henu.edu.cn
Received 24 May 2007
compound 2 in 40% yield. Marsella14 also described the
synthesis of a functionalized hexa[2,3-thienylene], a
tubular sexithiophene 4 in 3% yield from 3,3¢-bithio-
phenyl as the starting material in six steps. Rajca8b also re-
Abstract: Efficient synthetic procedures for the preparation of
b-trithiophenes (dithieno[2,3-b:3¢,2¢-d]thiophene) and two macro-
cyclic compounds, tetra[2,3-thienylene] and hexa[2,3-thienylene]
bearing trimethylsilyl (TMS) groups from 2,2¢-dibromo-5,5¢-bistri-
methylsilanyl[3,3¢]bithiophenyl are reported. The UV–Vis spectra ported the preparation of a functionalized derivative of 1,
property and crystal structures of these macrocyclic oligo-
thiophenes are described.
3,4-dibromo-2,5-bistrimethylsilanyldithieno[2,3-b;3¢,2¢-
d]thiophene together with the dimeric and trimeric 5 as
Key words: bithiophenyl, cyclization, fused-ring system, hetero-
cycles, macrocylces
side products. The yields of the dimers (2% and 0.3% for
two different structural dimers) and trimer 5 (0.1–0.4%)
were very low.
With considerable characteristics of environmental stabil-
ity and flexibility in synthesis, oligothiophenes and anne-
lated oligothiophenes are thought to be one of the most
versatile classes of conjugated systems.1–3 In recent years,
particular attention has been paid to oligothiophenes,
active materials in devices such as organic field effect
transistors (OFETs),4 organic semiconductors,5 light-
emitting diodes (LEDs),6 and photovoltaic cells.7
S
S
S
S
S
S
S
S
S
S
S
S
S
Dithieno[2,3-b:3',2'-
d]thiophene
tetra[2,3-thienylene]
hexa[2,3-thienylene]
1
2
3
Br
Br
Cl
Dithieno[2,3-b:3¢,2¢-d]thiophene 1 (Figure 1) has been
used as the building blocks for higher homologues of
helicences in recent years.8 As one of the six possible
isomeric dithienophenes, 1 has received considerable at-
tention in preparation. These synthetic methods included
oxidative ring closure of 3,3¢-dilithio-2,2¢-dithienyl sul-
fide;9 3,3¢-diZnCl or 3,3¢-diCuCN derivatives10 using
CuCl2 as an oxidizing reagent, high loading (15–20%) of
Pd-catalyzed11 cross-coupling transformation of 3,3¢-di-
bromo-2,2¢-dithienyl sulfide in the presence of hexameth-
ylditin and cyclization of 2,2¢-dilithio-3,3¢-dithienyl
sulfide.12
Cl
Cl
S
TMS
TMS
TMS
S
S
S
S
S
S
TMS
Br
S
S
S
Br
S
S
S
S
S
Br
Br
Cl
Cl
Cl
TMS TMS
4
5
Figure 1 Dithieno[2,3-b:3¢,2¢-d]thiophene 1 and macrocyclic oligo-
thiophenes 2–5
The synthesis for macrocyclic analogues, tetra[2,3-thi-
enylene] 2 and hexa[2,3-thienylene] 3 have also been
known for about 40 years (Figure 1). However, no effi-
cient method has been found for their synthesis, especially
for the twelve-membered macrocyclic compound 3. In
1978, Kauffmann13 reported the synthesis of 2 and 3 in
18% and 4% isolated yields, respectively via the CuCl2-
promoted oxidative homocoupling of 3,3¢-di-
lithio[2,2¢]bithiophene. Using copper-catalyzed coupling
of organozinc species, Iyoda10a reported the preparation of
In this paper, we wish to report an efficient synthetic route
to b-trithiophenes 1, and poly(2,3-thienylene)-based
macrocycles 10 and 11 starting from TMS-protected 2,2¢-
dibromo[3,3¢]bithiophenyl 8. In addition, the UV–Vis
spectral properties and crystal structures of macrocycles
10 and 11 have also been described.
Compound 1 could be prepared from 3-bromothiophene
in five steps (Scheme 1). The first step was a CuCl2-pro-
moted homocoupling reaction of 3-lithiothiophene pre-
pared in situ via the treatment of 3-bromothiophene with
1.01 equivalents of n-BuLi to afford 6 within 75–87%
yields. Bromination of 6 with NBS proceeded at a posi-
tions in high selectivity and high yield to give 7 in 91–
99% yields.15 The two acidic protons at a¢ positions in 7
SYNLETT 2007, No. 15, pp 2390–2394
1
7
.0
9
.2
0
0
7
Advanced online publication: 13.08.2007
DOI: 10.1055/s-2007-985582; Art ID: W10307ST
© Georg Thieme Verlag Stuttgart · New York

LETTER
Efficient Synthesis of b-Trithiophenes and Macrocyclic Compounds
2391
were then protected as the bis(TMS) derivative 8 in 89% generate 2 (18%) and 3 (4%) from the literature.13 The
yield.16 Double Br/Li-exchange on 8 by t-BuLi, followed amazing result was that high yields of 10 (41%) and 11
by reaction with bis(phenylsulfonyl)sulfide produced 2,5- (36%) were obtained when 8 was employed.19 Such a
bis(TMS)dithieno[2,3-b;3¢,2¢-d]thiophene 9, an annelated high-yield preparation of 11 is probably the best synthetic
b-trithiophenes derivative in 65% yield.17 Replacing t- protocol to prepare the twelve-membered macrocyclic
BuLi with n-BuLi still afforded compound 9 in 52% yield. oligothiophene compounds.
Due to the presence of the two TMS groups, 8 has a very Compound 8, as compared to 7, possesses TMS-protected
good solubility and there was no solubility problem in groups that could prevent the possible side reactions from
both Br/Li-exchange and subsequent coupling reaction. occurring at the acidic a positions and could also avoid the
On the other hand, TMS-protected 8 also prevented possi- solubility problem during the Br/Li-exchange reaction
ble side reactions from occurring at the acidic a positions and subsequent homocoupling. These factors could be
of 7 during the Br/Li-exchange reaction and its subse- used to explain why a lower yield was obtained from the
quent coupling reaction. In fact, direct conversion of com- homocoupling reaction of compound 7.13
pound 7 (step f, Scheme 1) gave compound 1 in much
Compounds 2 and 3 could be prepared in 86% and 83%
yields from compounds 10 and 11, respectively, by re-
lower yield (31%) according to the literature.12 In con-
trast, our method offers a practical route to compound 1 in
reasonably good yields (overall 40–47%). Subsequent
moving the TMS groups in the presence of TFA in
CHCl3.20 Therefore, compounds 2 and 3 could be obtained
removal of the TMS groups in 9 in the presence of TFA
in overall ca. 28% and ca. 24% isolated yields, respective-
ly in five steps from 3-bromothiophene.
generated the target compound 1 in 98% yield.18
Scheme 1 also depicts the synthetic route to the macro-
cyclic oligothiophenes 2, 3, 10 and 11. The dimeric eight-
membered ring compounds 2 and 10, and the trimeric
The structures of dimer 10 and trimer 11 were confirmed
by single crystal X-ray analysis (Figure 2).21,22 Compound
10 possessed approximately the D2 point group of sym-
twelve-membered ring compounds 3 and 11, were synthe-
metry. In the structure of dimer 10, the central cycloocta-
sized via the CuCl2-promoted oxidative homocoupling of
tetraene ring had a ‘saddle’ form with an average dihedral
2,2¢-dilithio[3,3¢]bithiophene derivatives. After the dou-
angle of 51.7°, which was smaller than that in tetra-o-
ble Br/Li-exchange of compound 7, the resulting 2,2¢-di-
lithio[3,3¢]bithiophene was oxidized with CuCl2 to give 2
(27%) and 3 (7%). The yields are comparable to those
from the oxidation of 3,3¢-dilithio[2,2¢]bithiophene to
phenylene derivatives.23 Tetra-o-thiophene moiety ex-
hibited a more planar structure than the tetra-o-phenylene
moiety. The molecular symmetry in solution on the NMR
time-scale corresponds to the approximate molecular
S
S
S
S
S
S
S
S
+
S
S
S
S
S
2, 27%
3, 7%
1, 98%
e
f
g
Br
TMS
TMS
TMS
TMS
a
b
c
d
S
S
S
S
S
S
S
S
S
S
Br
Br
7, 95%
Br
Br
8, 89%
6, 75–87%
9, 65%
h
TMS
TMS
TMS
S
TMS
TMS
S
S
S
S
+
S
S
S
S
S
TMS
TMS
TMS
TMS
TMS
10, 41%
11, 36%
Scheme 1 Synthesis of annelated b-trithiophenes 1 and macrocyclic oligothiophenes 10 and 11.
Reagents and conditions: (a) (i) n-BuLi (1.01 equiv), Et2O, –78 °C; (ii) CuCl2 (1.01 equiv); (b) NBS (2.4 equiv), AcOH–CHCl3 (1:1), r.t.;
(c) (i) LDA (2.3 equiv), Et2O, 0 °C; (ii) TMSCl (5.0 equiv), –78 °C; (d) (i) t-BuLi (4.6 equiv), Et2O, –78 °C; (ii) (PhSO2)2S (1.0 equiv), –78 °C
to r.t., overnight; (e) TFA, CHCl3; (f) BuLi–SCl2 or (PhSO2)2S, 31% (ref. 12); (g, h) i) n-BuLi (2.3 equiv), Et2O, 0 °C; ii) CuCl2 (3.0 equiv),
–78 °C to r.t., overnight.
Synlett 2007, No. 15, 2390–2394 © Thieme Stuttgart · New York

2392
Y. Wang et al.
LETTER
Figure 2 Molecular structures and conformations for compounds
10 and 11, left: top view for 10; right: side view for 11
symmetry determined by crystallography. In dimer 10, in
which the bithienyl moieties are axially homochiral, the
1H and 13C NMR spectra show only one type of thiophene
moiety at room temperature.
Figure 3 The UV–Vis spectra for 2, 3, 6, 10 and 11 in CHCl3
([C] = 3 × 10–5 M) at room temperature
functional materials with b-trithiophenes as building
blocks. With the development of efficient preparations of
10 and 11, such macrocyclic compounds could be used as
a new type of host molecules in the field of supramolecu-
lar chemistry.
Similar to the case of 5,8b trimer 11 possessed a chiral con-
formation with a somewhat distorted C2 point group sym-
metry. The shape of the twelve-membered core looked
like a distorted U-shaped cycle containing both convex
and concave U-shapes linked together. The rim distances
between the two convex ‘U’s and the two concave ‘U’s
were the same (ca. 3.5 Å). The two homochiral bithienyl
moieties of 11 had cisoid conformations, but the third
moiety had a transoid conformation. The 1H and 13C NMR
spectra at room temperature showed three nonequivalent
thiophene moieties, due to two bithienyl moieties possess-
Acknowledgment
This research was supported by the National Science Foundation of
China (20572015, 20672028), Program for New Century Excellent
Talents in University (NCET-05-0610), the Scientific Research
Foundation for the Returned Overseas Chinese Scholars, State
Education Ministry (SRF for ROCS, SEM), Program for Young
Excellent Talents in Henan Universities, Foundation of Education
Department of Henan Province (2006150004), Program for Extra-
ordinary Professors of Henan University and the Key Foundation of
Henan University (04ZDZR013).
1
ing the same relative configuration. Similar H and 13C
NMR spectra behaviors were also found in the case of 3.
The electronic absorption UV–Vis spectrum of
[3,3¢]bithiophenyl 6 was used as a reference for the eval-
uation of electron delocalization of macrocyclic oligoth-
iophenes 2, 3, 10 and 11. The spectra of 2, 3, 6, 10 and 11
References and Notes
showed two major bands at lmax ≈ 242–244 nm and lmax
≈
(1) Roncali, J. Chem. Rev. 1992, 92, 711.
262–294 nm (Figure 3). Almost no shift changes could be
observed for the bands at 242–244 nm for all compounds.
However, substantial bathochromic shifts of the long
wavelength bands were found for dimer 2 (279 nm), and
trimer 3 (294 nm) as compared to monomer 6 (262 nm).
With TMS groups, both dimer 10 and trimer 11 showed
additional shoulder peaks at 332 nm and 337 nm, respec-
tively, as compared to 2 and 3. The significant increases
in absorbance were also observed for all macrocyclic
oligothiophenes as compared to 6. The macrocyclic oligo-
thiophenes possess the molecular connectivity of homo-
logous cross-conjugated p systems. Both the distortion
and the possible conjugation may affect the increased
delocalization in macrocyclic oligothiophenes.
(2) Handbook of Oligothiophenes and Polythiophenes; Fichou,
D., Ed.; Wiley-VCH: Weinheim, 1999.
(3) Radke, K. R.; Ogawa, K.; Rasmussen, S. C. Org. Lett. 2005,
7, 5253.
(4) (a) Xiao, K.; Liu, Y.; Qi, T.; Zhang, W.; Wang, F.; Gao, J.;
Qiu, W.; Ma, Y.; Cui, G.; Chen, S.; Zhan, X.; Yu, G.; Qin,
J.; Hu, W.; Zhu, D. J. Am. Chem. Soc. 2005, 127, 13281.
(b) Sun, Y.; Ma, Y.; Liu, Y.; Lin, Y.; Wang, Z.; Wang, Y.;
Xiao, K.; Chen, X.; Qiu, W.; Zhang, B.; Yu, G.; Hu, W.;
Zhu, D. Adv. Funct. Mater. 2006, 16, 426. (c) Morrison, J.
J.; Murray, M. M.; Li, X. C.; Holmes, A. B.; Morratti, S. C.;
Friend, R. H.; Sirringhaus, H. Synth. Met. 1999, 102, 987.
(5) Li, X. C.; Sirringhaus, H.; Garnier, F.; Holmes, A. B.;
Morratti, S. C.; Feeder, N.; Clegg, W.; Teat, S. J.; Friend, R.
H. J. Am. Chem. Soc. 1998, 120, 2206.
(6) (a) Barbarella, G.; Favaretto, L.; Sotgiu, G.; Zambianchi,
M.; Fattori, V.; Cocchi, M.; Cacialli, F.; Gigli, G.; Cingolani,
R. Adv. Mater. 1999, 11, 1375. (b) Halls, J. J. M.; Walsh, C.
A.; Greenham, N. C.; Marseglia, E. A.; Friend, R. H.;
Moratti, S. C.; Holmes, A. B. Nature (London) 1995, 376,
498.
In summary, a new synthesis of functionalized b-
trithiophenes 9 and two macrocyclic oligothiophenes, 10
and 11 has been developed. The introduction of TMS as
protecting groups into [3,3¢]bithiophenyl was the key to
the successful preparation of the title compounds. This
work will facilitate the synthetic approaches to organic
(7) Noma, N.; Tsuzuki, T.; Shirota, Y. Adv. Mater. 1995, 7, 647.
Synlett 2007, No. 15, 2390–2394 © Thieme Stuttgart · New York

LETTER
Efficient Synthesis of b-Trithiophenes and Macrocyclic Compounds
2393
(8) From Dr. Rajca’s work: (a) Rajca, A.; Wang, H.; Pink, M.;
Rajca, S. Angew. Chem. Int. Ed. 2000, 39, 4481; Angew.
Chem. 2000, 112, 4655. (b) Rajca, A.; Miyasaka, M.; Pink,
M.; Wang, H.; Rajca, S. J. Am. Chem. Soc. 2004, 126,
15211. (c) Miyasaka, M.; Pink, M.; Rajca, A.; Rajca, S.
Chem. Eur. J. 2004, 10, 6531. (d) Miyasaka, M.; Rajca, A.
Synlett 2004, 177. (e) Miyasaka, M.; Rajca, A.; Pink, M.;
Rajca, S. J. Am. Chem. Soc. 2005, 127, 13806.
(9) Jong, F.; Janssen, M. J. J. Org. Chem. 1971, 36, 1645.
(10) (a) Kabir, S. M. H.; Miura, M.; Sasaki, S.; Harada, G.;
Kuwatani, Y.; Yoshida, M.; Iyoda, M. Heterocycles 2000,
52, 761. (b) Miyasaka, M.; Rajca, A. J. Org. Chem. 2006,
71, 3264.
(11) Iyoda, M.; Miura, M.; Sasiki, S.; Kabir, S. M. H.; Kuwatani,
Y.; Yoshida, M. Tetrahedron Lett. 1997, 38, 4581.
(12) Nenajdenko, V. G.; Gribkov, D. V.; Sumerin, V. V.;
Balenkova, E. S. Synthesis 2003, 124.
(13) Kauffmann, T.; Greving, B.; Kriegesmann, R.; Mitschker,
A.; Woltermann, A. Chem. Ber. 1978, 111, 1330.
(18) Preparation of 1: To a solution of 9 (2.11 g, 6.19 mmol) in
CHCl3 (30 mL), TFA (2.0 mL) was added dropwise at r.t.
The reaction progress was monitored by TLC analysis. After
stirring at r.t. for 1 h, the reaction mixture was quenched with
H2O (10 mL), extracted with CHCl3 (3 × 50 mL), and then
washed with sat. NaHCO3 (40 mL) and H2O (2 × 40 mL).
After drying over MgSO4, the solvent was removed in
vacuo. A white powder of 1 (1.20 g, 98.7%) was obtained.
From another reaction on a 2.09-g scale of 9, 1.17 g (97.2%)
of 1 was obtained; mp 84–85 °C (lit.10b 86–87 °C). 1H NMR
(400 MHz, CDCl3): d = 7.40 (d, J = 5.2 Hz, 2 H), 7.38 (d,
J = 5.2 Hz, 2 H). 13C NMR (100 MHz, CDCl3): d = 139.0,
138.3, 127.5, 118.8. MS (EI, 70 eV): m/z = 196 (100) [M+].
IR (KBr): 2955, 2894 (CH) cm–1.
(19) Preparation of 10 and 11: To a solution of 8 (2.00 g, 4.27
mmol) in anhyd Et2O (60 mL), n-BuLi (2.5 M, 4.0 mL, 10.0
mmol, 2.3 equiv) was added dropwise at –78 °C. After
keeping at –78 °C for 2 h, anhyd CuCl2 (1.7 g, 12.6 mmol,
3.0 equiv) was added. The reaction mixture was kept at
–78 °C for 2 h, and then slowly warmed to r.t. overnight. The
reaction mixture was quenched with H2O (50 mL), extracted
with Et2O (3 × 40 mL), washed with H2O (50 mL), and then
finally dried over MgSO4. After removing the solvent in
vacuo, the residue was purified by column chromatography
on silica gel with PE (60–90 °C) as eluent to yield 10 (0.55 g,
41.5%) as a pale white crystal and 11 (0.40 g, 36.5%) as a
white powder. For 10: mp 302 °C(sublimation). 1H NMR
(14) Marsella, M. J.; Yoon, K.; Tham, F. S. Org. Lett. 2001, 3,
2129.
(15) Compounds 6 and 7 were prepared according to the method
from ref. 12.
(16) Preparation of 8: n-BuLi (2.5 M in hexane, 15.0 mL, 37.5
mmol, 2.2 equiv) was added dropwise to diisopropylamine
(5.5 mL, 38.9 mmol, 2.3 equiv) in Et2O (30 mL) at 0 °C.
After keeping at 0 °C for 0.5 h, the prepared LDA solution
was transferred by syringe into a solution of 7 (5.44 g, 16.8
mmol) with anhyd Et2O. After keeping at 0 °C for 2 h, the
reaction mixture was cooled to –78 °C, then trimethyl-
chlorosilane (10.8 mL, 85.1 mmol, 5.1 equiv) was added
dropwise. The reaction mixture was kept at –78 °C for 1 h
and then warmed slowly to r.t. overnight. After quenching
with H2O (50 mL), the crude product was extracted with
Et2O (3 × 40 mL) and washed with H2O (50 mL), and then
dried over MgSO4. After removing the solvent in vacuo, the
residue was purified by column chromatography on silica
gel with PE (60–90 °C) as eluent to yield 8 (7.00 g, 89.1%)
as a white solid. From two other reactions on a 4.44-g and
5.79-g scale of 7, 5.74 g (89.5%) and 7.39 g (88.4%) of 8
were obtained, respectively; mp 79–81 °C. 1H NMR (400
MHz, CDCl3): d = 7.15 (s, 2 H), 0.32 (s, 18 H). 13C NMR
(100 MHz, CDCl3): d = 141.7, 137.0, 136.0, 115.7, 0.0
[J(29Si–13C) = 54 Hz]. MS (EI, 70 eV): m/z = 568 (14)
[M+], 453 (67) [M+ – Me]. Anal. Calcd for C14H20Br2S2Si2
(468.42): C, 35.90; H, 4.30; S, 13.69. Found: C, 35.33; H,
4.40; S, 13.46. IR (KBr): 3095, 3078, 2927, 2857 (CH) cm–1.
(17) Preparation of 9: To a solution of 8 (1.00 g, 2.13 mmol) in
anhyd Et2O (80 mL), t-BuLi (2.5 M, 3.9 mL, 4.6 equiv) was
added dropwise at –78 °C. After keeping at –78 °C for 2 h,
anhyd (PhSO2)2S (0.67 g, 2.13 mmol, 1.0 equiv) was added,
then the reaction mixture was kept at –78 °C for 2 h and
warmed slowly to r.t. overnight. The reaction mixture was
quenched with H2O (50 mL), extracted with Et2O (2 × 40
mL) and then washed with H2O (2 × 50 mL). After drying
over MgSO4, the solvent was removed in vacuo. The residue
was purified by column chromatography on silica gel with
PE (60–90 °C) as eluent to yield 9 (0.47 g, 64.8%) as a white
solid. From two other reactions on a 1.00-g and 3.00-g scale
of 8, using n-BuLi (2.3 equiv), 0.38 g (52.4%) and 1.10 g
(51.0%) of 9 were obtained, respectively; mp 49–50 °C. 1H
NMR (400 MHz, CDCl3): d = 7.47 (s, 2 H), 0.37 (s, 18 H).
13C NMR (100 MHz, CDCl3): d = 144.5, 144.1, 139.8, 125.1,
–0.3. MS (EI, 70 eV): m/z = 340 (77) [M+], 325 (100) [M+ –
Me]. Anal. Calcd for C14H20S3Si2 (340.67): C, 49.36; H,
5.92; S, 28.24. Found: C, 49.30; H, 5.83; S, 27.74. IR (KBr):
2951, 2889 (CH) cm–1.
(400 MHz, CDCl3): d = 7.06 (s, 4 H), 0.32 (s, 36 H). 13
C
NMR (100 MHz, CDCl3): d = 142.3, 137.7, 137.3, 136.8,
136.5, –0.2 [J(29Si–13C) = 49 Hz]. HRMS (ESI): m/z [M +
H]+ calcd for C28H41S4Si4: 617.1168; found: 617.1154.
HRMS (ESI): m/z [M + Na]+ calcd for C28H40NaS4Si4:
639.0988; found: 639.0997. IR: 3160.2, 2954.9 (CH) cm–1.
For 11: mp 258–261 °C (wax), 286 °C (clear). 1H NMR (400
MHz, CDCl3): d = 7.17 (s, 2 H), 6.83 (s, 2 H), 6.44 (s, 2 H),
0.38 (s, 18 H), 0.28 (s, 18 H), 0.18 (s, 18 H). 13C NMR (100
MHz, CDCl3): d = 140.0, 139.8, 139.5, 138.4, 138.1, 136.4,
136.0, 135.6, 134.8, 132.3, –0.1. HRMS (ESI): m/z [M + H]+
calcd for C42H61S6Si6: 925.1713; found: 925.1700. HRMS
(ESI): m/z [M + Na]+ calcd for C42H60NaS6Si6: 947.1532;
found: 947.1564. IR: 3160.2, 2955.5 (CH) cm–1.
(20) Compounds 2 and 3 were prepared from 10 and 11,
respectively according to the method used for the
preparation of 1 from 9. Compound 2: mp 252–253 °C (lit.13
253–256 °C). 1H NMR (400 MHz, CDCl3): d = 7.40 (d, J =
5.4 Hz, 4 H), 6.96 (d, J = 5.4 Hz, 4 H). MS (EI): m/z = 328
(100) [M+]. HRMS (ESI): m/z [M + H]+ calcd for C16H9S4:
328.9587; found: 328.9588. IR: 3101.2, 2926.0 (CH) cm–1.
Compound 3: mp 281–283 °C (sublimation). 1H NMR (400
MHz, CDCl3): d = 7.33 (d, J = 5.2 Hz, 2 H), 7.08 (d, J = 5.2
Hz, 2 H), 6.97 (d, J = 5.2 Hz, 2 H), 6.92 (d, J = 5.1 Hz, 2 H),
6.79 (d, J = 5.2 Hz, 2 H), 6.44 (d, J = 5.1 Hz, 2 H). 13C NMR
(100 MHz, CDCl3): d = 135.4, 133.4, 133.3, 132.1, 131.9,
131.5, 131.0, 130.4, 130.0, 129.7, 128.8, 126.1, 125.0,
124.9. MS (EI): m/z = 492 (48) [M+]. HRMS (ESI): m/z [M
+ H]+ calcd for C24H13S6: 492.9341; found: 492.9341. IR:
3100.5, 2924.6 (CH) cm–1.
(21) (a) Crystal Data for 10: M = 701.36, C34H52S4Si4, triclinic,
space group P1, a = 12.6217(9) Å, b = 13.2892(9) Å, c =
13.3125(9) Å, a = 110.0070(10)°, b = 111.4940(10)°, g =
96.1850(10)°, V = 1881.6(2) Å3, Z = 2, Dcalcd = 1.238 g/cm3.
A colorless crystal of dimensions 0.30 × 0.23 × 0.11 mm was
used for measurement at 293 (2) K with the w scan mode on
a Bruker Smart APEX diffractometer with CCD detector
using Mo–Ka radiation (l = 0.71073 Å). The data were
corrected for Lorentz and polarization effects and absorption
corrections were performed using SADABS21b program. The
Synlett 2007, No. 15, 2390–2394 © Thieme Stuttgart · New York

2394
Y. Wang et al.
LETTER
crystal structures were solved using the SHELXTL21c
program and refined using full matrix least squares. The
positions of hydrogen atoms were calculated theoretically
and included in the final cycles of refinement in a riding
model along with attached carbons. The final cycle of full-
matrix least-squares refinement was based on 7240
independent reflections [I >2s(I)] and 357 variable
parameters with R1 = 0.0667, wR2 = 0.1979. The
supplementary crystallographic data can be obtained free of
charge from the Cambridge Crystallographic Data Centre
via www.ccdc.cam.uk/data_request/cif. Please quote the
reference number CCDC: 652683. (b) Sheldrick, G. M.
SADABS; University of Göttingen: Germany, 1996.
(c) Sheldrick, G. M. SHELXTL Version 5.1; Bruker
Analytical X-ray Systems, Inc.: Madisonv / WI, 1997.
(22) Crystal Data for 11: M = 1045.17, C43H61Cl3S6Si6, triclinic,
space group P1, a = 11.8377(12) Å, b = 14.0164(15) Å, c =
17.9101(18) Å, a = 94.620(2)°, b = 103.881(2)°, g =
94.390(2)°, V = 2861.4(5) Å3, Z = 2, Dcalcd = 1.213 g/cm3.
A colorless crystal of dimensions 0.30 × 0.11 × 0.11 mm was
used for measurement at 293 (2) K. The structure was solved
by the same methods as used for 10. The final cycle of full-
matrix least-squares refinement was based on 11009
observed reflections [I >2s(I)] and 541 variable parameters
with R1 = 0.0731, wR2 = 0.1255. The supplementary
crystallographic data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via
www.ccdc.cam.uk/data_request/cif. Please quote the
reference number CCDC: 652684.
(23) (a) Rajca, A.; Wang, H.; Bolshov, P.; Rajca, S. Tetrahedron
2001, 57, 3725. (b) Iyoda, M.; Kabir, S. M. H.; Vorasingha,
A.; Kuwatani, Y.; Yoshida, M. Tetrahedron Lett. 1998, 39,
5393. (c) Man, Y. M.; Mak, T. C. W.; Wong, H. N. C. J. Org.
Chem. 1990, 55, 3214.
Synlett 2007, No. 15, 2390–2394 © Thieme Stuttgart · New York

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