Non-symmetrical oligothiophenes with 'incompatible' substituents

Article abstract of DOI:10.1016/j.tet.2006.11.029

The syntheses of oligothiophenes 1 and 2 comprising two different types of peripheral substituents, namely alkyl and perfluoroalkyl, is reported. The key synthetic step is the Pd-catalyzed cross-coupling of perfluoroalkylated bromide 3 with an appropriate boronate. This molecular design is expected to promote unusual two-layer packing, which is of interest for application in electronic devices. Quaterthiophene 1 forms smectic mesophase, though in the narrow temperature range, and is suitable for the fabrication of thin films by solution processing methods.

Full text of DOI:10.1016/j.tet.2006.11.029

Tetrahedron 63 (2007) 941–946
Non-symmetrical oligothiophenes with ‘incompatible’
substituents
*
Delphine Didier, Sergey Sergeyev and Yves Henri Geerts
´
Universite Libre de Bruxelles, Laboratoire de Chimie des Polymeres, CP 206/01, Boulevard du Triomphe, 1050 Bruxelles, Belgium
ꢀ
Received 3 October 2006; revised 9 November 2006; accepted 10 November 2006
Available online 29 November 2006
Abstract—The syntheses of oligothiophenes 1 and 2 comprising two different types of peripheral substituents, namely alkyl and perfluoro-
alkyl, is reported. The key synthetic step is the Pd-catalyzed cross-coupling of perfluoroalkylated bromide 3 with an appropriate boronate.
This molecular design is expected to promote unusual two-layer packing, which is of interest for application in electronic devices. Quater-
thiophene 1 forms smectic mesophase, though in the narrow temperature range, and is suitable for the fabrication of thin films by solution
processing methods.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
Oligothiophenes have been receiving increasing attention in
the field of organic electronics due to their interesting semi-
conducting properties. In particular, a,u-dialkylthiophenes
demonstrate high charge carrier mobility in liquid crystal-
line mesophases combined with the excellent chemical and
electrochemical stability.1,2 However, all such systems be-
have as p-type (hole transporting) semiconductors, presum-
ably because of the electron-richness of the thiophene rings.
On the other hand, development of n-type (electron trans-
porting) semiconducting materials would promote new ap-
plications such as ambipolar transistors or p–n junction
Figure 1. Molecular structure of oligothiophenes 1 and 2 (bottom) and their
two-layer packing (top).
diodes and contribute to a better fundamental understanding
of charge transport in organic molecular semiconductors.3
Recently, the synthesis of a series of a,u-diperfluorohexyl-
oligothiophene was reported.4 Notably, a,u-diperfluoro-
Figure 1: (i) the self-organization into a large variety of
lyotropic mesophases as a function of concentration and the
nature of solvent (alkanes, perfluoroalkanes, aromatics); (ii)
formation of thin films with different morphologies depend-
ing on deposition conditions; and (iii) the packing into highly
ordered smectic mesophases promoting fast ambipolar
charge transport.
hexylsexithiophene shows n-type semiconductivity in thin
film transistors.3 Apparently, electron transport in this mole-
cule bearing polyfluoroalkyl substituents is facilitated by the
stabilization of anion-radicals.
Here, we report the syntheses and characterization of the
non-symmetric quaterthiophene 1 and sexithiophene 2, com-
prising three ‘incompatible’ parts: a rigid aromatic core, a
perfluoroalkyl chain and an alkyl chain. Several new features
are anticipated from these rod-like molecules depicted in
2. Results and discussion
The convergent syntheses of oligothiophenes 1 and 2 com-
prising alkyl and perfluoroalkyl substituents rely on Suzuki–
Miyaura coupling5 as a key step (Schemes 1 and 2). It should
be noted here that only few examples of oligothiophenes with
different substituents in one molecule are known to date.
Thus, Funahashi and Hanna recently reported high charge
Keywords: Liquid crystals; Oligothiophenes; Perfluoroalkylation; Cross-
coupling.
* Corresponding author. Tel.: +32 2 650 5390; fax: +32 2 650 5410; e-mail:
ygeerts@ulb.ac.be
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.11.029

942
D. Didier et al. / Tetrahedron 63 (2007) 941–946
Scheme 1. Synthesis of quaterthiophene 1.
carrier mobility in smectic phases of a-alkyl-a0-alkynyloli-
gothiophenes, prepared by multi-step synthesis involving
sequential Kumada couplings as key steps to assemble the
oligothiophene core.2 Although it appears clear that non-
symmetrical oligothiophenes should be easily accessible by
the Suzuki coupling of the correspondent building blocks, no
successful attempt is mentioned in the literature. In addition,
the synthetic approach based on Suzuki coupling is particu-
larly attractive since a great number of arylboronate building
blocks is either available commercially or can be easily
prepared from commercial precursors.
poorly reproducible: the yield of 6 varied between 14 and
68% while 53% was reported by Facchetti et al.4 In addition,
further unidentified side products were detected (TLC and
1H NMR).
Due to encountered reproducibility problem, we decided
to test an alternative synthesis of 6 by the mild radical
perfluoroalkylation of terthiophene (4) with perfluorohexa-
noyl peroxide. This method was successfully employed in
the synthesis of various perfluoroalkyl thiophenes and furans
and demonstrated excellent regioselectivity and high yields.8
However, its use for the perfluoroalkylation of oligothio-
phenes was not reported. Perfluorohexyl peroxide was gener-
ated in situ from the corresponding acyl chloride and H2O2/
NaOH in water9 and its concentration in solution was deter-
mined by the iodometric titration.10 When terthiophene (4)
was allowed to react with solution of perfluorohexanoyl per-
oxide at 40 ꢀC, the product 6 with the perfluorohexyl substi-
tuent in the a-position of the terminal thiophene ring was
isolated. No detectable amounts of regioisomeric side prod-
ucts or products resulting from the multiple substitution of
hydrogen atoms by the C6F13 radical were observed. On
the other hand, the yield of 6 remained rather moderate
(31%). In addition, the polyfluorinated diacyl peroxides are
unstable at ambient conditions even in diluted solutions
and require quick manipulations at low temperatures.
They key intermediate in the syntheses of 1 and 2 is the
perfluorohexyl terthiophene 3. Among known methods of
perfluoroalkylation of aromatic molecules, a Cu-promoted
cross-coupling between aryl bromides or iodides and
perfluoroalkyl iodides in polar solvent (typically DMSO)
is frequently used. This method was reported to give satis-
factory results for a variety of aromatic substrates6 including
thiophenes and oligothiophenes.4 The use of the Cu-pro-
moted cross-coupling method requires the synthesis of the
intermediate monobromide 5, which was prepared from
the commercial terthiophene (4) by slightly modified known
methods.4,7 We have found that the bromination with N-bro-
mosuccinimide (NBS) in N,N-dimethylformamide (DMF)
at the ambient temperature gives the best results (69% yield
of 5 after crystallization) while reaction in CCl4 produced
considerable amounts of the corresponding dibromide.
Finally, perfluorohexyl terthiophene 6 was brominated (NBS
and DMF) to give bromide 3 in 68% yield.
The subsequent reaction of bromide 5 with n–C6F13I and
copper in DMSO at 125 ꢀC furnished perfluoroalkylterthio-
phene 6 (Scheme 1). However, we found this reaction to be
Another intermediate in the synthesis of quaterthiophene 1 is
boronate 7. It was synthesized from the bromo thiophene 9,
Scheme 2. Synthesis of sexithiophene 2.

D. Didier et al. / Tetrahedron 63 (2007) 941–946
943
prepared by the bromination of commercial 2-octylthiophene
(8) with NBS in 92% yield.11 On the other hand, one-pot
synthesis involving bromine–lithium exchange in 9 followed
by the reaction of the lithium derivative with B(OEt)3 and
subsequent transesterification with pinacol (2,3-dimethyl-
butane-2,3-diol)12 produced boronate 7 in 59% yield after
purification by column chromatography.
water from 11 to give olefin 12. This elimination is likely
catalyzed by traces of acid and proceeds extremely easily
because of formation of the resonance-stabilized cation 13.
However, by a thorough control of reaction time the un-
wanted side reaction was completely avoided and the target
alcohol 11 was isolated in 95% yield (Scheme 2).
The hydride transfer reduction of alcohol 11 to give 14
is non-trivial as many reducing agents provoke the above
mentioned elimination of water from 11 to give olefin 12.
However, reduction with ZnI2 and Na[BH3CN] in dry 1,2-di-
chloroethane at the ambient temperature according to the
known general method18 provided the target 14 (89% yield).
Subsequent bromination of 14 with NBS in DMF did not
represent any difficulty and afforded bromide 15 in nearly
quantitative yield (97%). In the next step, 15 was converted
to the boronate 16 via bromine–lithium exchange followed
by reaction of the lithium intermediate with 2-isopropoxy-
4,4,5,5-tetramethyl-1,3,2-dioxaborolane.19
In a key step, boronate 7 was reacted with bromide 3 in
typical Suzuki coupling conditions with [Pd(PPh3)4] as a
catalyst.13 After standard workup, quaterthiophene 1 (53%
yield) was isolated by precipitation from CH2Cl2 and puri-
fied by two repetitive crystallizations from toluene.
Quaterthiophene 1 (yellow solid with limited solubility in
common organic solvents) was characterized and its high
purity was confirmed by 1H, 19F, and 13C NMR, EIMS, and
UV–vis spectroscopy. Thermotropic properties of 1 were in-
vestigated by differential scanning calorimetry (DSC). The
DSC trace of 1 (Fig. 2) exhibits a distinct transition between
crystalline (Cr) and liquid crystalline (LC) phases at 198 ꢀC
[enthalpy 23.1 kJ molꢁ1] and a clearing point at 207 ꢀC
[2.8 kJ molꢁ1]. The LC mesophase between 198 ꢀC and
207 ꢀC was preliminarily identified as a fluid smectic, prob-
ably SmA phase from the characteristic birefringent flowing
texture obtained by the polarized optical microscopy (POM)
study.14 This tentative assignment is supported by the low
value of the enthalpy of isotropization, which is consistent
with moderately ordered structure of a mesophase.15
Finally, Suzuki coupling between bromide 3 and boronate 16
in the same conditions as in the synthesis of quaterthiophene
1 afforded sexithiophene 2 as an orange solid (55%), which
precipitated from the reaction mixture. In spite of the steri-
cally demanding branched alkyl chain, sexithiophene 2 is
nearly insoluble in common organic solvents and was puri-
fied by washing with copious amounts of water and toluene
and then dried in vacuum.
1
Sexithiophene 2 was characterized by H NMR, UV–vis,
and EIMS spectroscopy. H NMR spectrum confirmed the
1
For the synthesis of non-symmetrical sexithiophene 2 we
used a similar strategy involving Suzuki cross-coupling as a
key step. It is well known that the expansion of the aromatic
core dramatically reduces solubility of p-conjugated rod-
like molecules. On the other hand, branching of side chains
efficiently reduces p–p-stacking between aromatic cores of
various mesogens and improves solubility.16 Taking into ac-
count the modest solubility of quaterthiophene 1 in organic
solvents, we decided to introduce branched alkyl substitu-
ents in the molecule of sexithiophene 2. Addition of the
Grignard reagent prepared from the racemic 1-bromo-3,7-
dimethyloctane to aldehyde 1017 afforded the tertiary alco-
hol 11 as a mixture of diastereoisomers, which was used in
the next synthetic step without separation. It should be noted
that this addition was accompanied by the elimination of
substitution of the oligothiophene core with a-alkyl and
a0-perfluoroalkyl groups (characteristic signals at ca. 6.65
and ca. 7.45 ppm, respectively, cf. spectrum of 1). On the
other hand, 1H NMR spectrum revealed presence of impuri-
ties in the sample. In addition, broadening of the signals, pre-
sumably due to strong self-aggregation, was observed. Very
low solubility of sexithiophene 2 renders its purification by
chromatography or crystallization impossible. It should be
noted that even the 1H NMR measurement was very difficult
and required long time due to very poor solubility of 2. The
DSC trace of 2 did not indicate any phase transitions before
the apparent decomposition above 250 ꢀC. Taking all this
into account, we decide to focus our further studies on deriv-
atives of quaterthiophene with ‘incompatible’ alkyl and
Figure 2. Left: DSC traces of quaterthiophene 1 upon heating and cooling, 10 ꢀC minꢁ1; right: POM images of 1 obtained after cooling from 220 ꢀC (isotropic
liquid) to 200 ꢀC (smectic liquid crystalline phase).

944
D. Didier et al. / Tetrahedron 63 (2007) 941–946
perfluoroalkyl substituents such as 1. On the other hand, we
planned to study the possibility of purification and process-
ing of 2 by vacuum techniques such as gradient sublimation
and vapor deposition.
(100 mL) and CH2Cl2 (50 mL) were added to the filtrate, the
organic layer was washed with water, dried over MgSO4,
and concentrated in vacuum. Crystallization from hexane/
toluene afforded compound 5 (882 mg, 69%). Yellow solid;
1
mp 135–136 ꢀC; H NMR (300 MHz, CDCl3, 25 ꢀC):
3
4
d¼7.22 (dd, JH,H¼5.1 Hz, JH,H¼1.2 Hz, 1H), 7.16 (dd,
4
3
3. Conclusion
3JH,H¼3.6 Hz, JH,H¼1.2 Hz, 1H), 7.05 (d, JH,H¼3.9 Hz,
3
1H), 7.01 (dd, JH,H¼3.6, 5.1 Hz, 1H), 6.99 (d,
3
We have described the syntheses of quaterthiophene 1 and
sexithiophene 2 bearing ‘incompatible’ peripheral substitu-
ents. This is, to the best of our knowledge, the first example
of such design of the rod-like molecules with potential semi-
conducting properties. Although quaterthiophene 1 is rela-
tively poorly soluble in organic solvents, it can be easily
purified by crystallization. Solubility of 1 in some solvents
such as CH2Cl2/CS2 is sufficient for the processing of thin
filmsbysolutionmethods. On thecontrary, thoroughpurifica-
tion of the nearly insoluble sexithiophene 2 is hardly possible.
3JH,H¼3.9 Hz, 1H), 6.96 (d, JH,H¼3.9 Hz, 1H), 6.89 (d,
3JH,H¼3.6 Hz, 1H); C NMR (75 MHz, CDCl3, 25 ꢀC):
13
d¼138.6, 136.8, 136.7, 135.0, 130.6, 127.9, 124.7, 124.5,
124.3, 123.9, 123.7, 111.0; HREIMS: m/z: calcd for
C12H779BrS3 ([M]+): 325.8893; found 325.8944; CIMS
(NH3): m/z (%)¼326 (58, [M]+), 249 (32), 203 (49); UV
(MeOH): lmax (3)¼387 nm (2.16ꢂ104 L molꢁ1 cmꢁ1).
4.1.2. 5-Tridecafluorohexyl-2,20:50,200-terthiophene (6).
Procedure 1.
A mixture of bromide 5 (206 mg,
0.631 mmol), Cu powder (217 mg, 3.42 mmol), C6F13I
(340 mL, 1.58 mmol), and dry DMSO (2.5 mL) was placed
in a Schlenk tube. The mixture was degassed by three
freeze-pump-thaw cycles and then heated for 18 h at
125 ꢀC (bath temperature). After cooling to room tempera-
ture, Et2O (20 mL) was added and the reaction mixture
was filtered over Celite. The organic phase was washed
with water, dried over MgSO4, and concentrated in vacuum.
Column chromatography (hexane) afforded 6 as a yellow
We are currently investigating fabrication of thin films of
1 by spin coating and their morphology by STM and X-ray
diffraction techniques. The fact that quaterthiophene 1 forms
a smectic liquid crystalline mesophase, though in narrow
temperature range, is quite encouraging. Our further research
efforts are directed to the tuning of the thermotropic behavior
and improvement of solubility of the novel quaterthiophene
mesogens. Further objectives involve studies of their semi-
conducting properties in organic field effect transistors.
solid. Yield 163 mg (46%); mp 127 ꢀC; 1H NMR (300 MHz,
3
CDCl3, 25 ꢀC): d¼7.32–7.36 (m, 1H), 7.26 (dd, JH,H
¼
3.6 Hz, 4JH,H¼1.2 Hz, 1H), 7.20 (dd, 3JH,H¼5.1 Hz, 4JH,H
¼
4. Experimental section
4.1. General
1.2 Hz, 1H), 7.13–7.17 (m, 2H), 7.11 (d, 3JH,H¼3.9 Hz, 1H),
7.04 (dd, JH,H¼3.6, 5.1 Hz, 1H); 13C NMR (75 MHz,
3
CDCl3, 25 ꢀC): d¼142.4, 138.3, 136.6, 134.0, 131.2, 128.1,
127.3, 126.0, 125.2, 124.5, 124.2, 123.4, 117.3, 114.7, 111.1,
19
All chemicals were purchased from Aldrich or Acros and
used without further purification unless stated otherwise.
THF was refluxed over sodium and benzophenone until a
blue-violet color persisted and distilled directly into the
reaction flask. Commercially available solution of n–BuLi
in hexane was titrated with Ph2CHCOOH immediately
before use. Column chromatography: SiO2 Kieselgel 60
(Macherey–Nagel, particle size 0.04–0.063 mm). TLC:
110.5, 110.3, 108.5; F NMR (376 MHz, CDCl3, 25 ꢀC):
d¼ꢁ81.2 (3F), ꢁ101.7 (2F), ꢁ121.9 (4F), ꢁ123.3 (2F),
ꢁ126.6 (2F); HREIMS: m/z: calcd for C18H7F13S3 ([M]+):
565.9502; found 565.9635; CIMS (NH3): m/z (%)¼567
(100, [M+H]+), 565 (39), 547 (46, [MꢁF]+), 297 (34,
[MꢁC5F11ꢁH]+); UV(MeOH): lmax (3)¼361 nm (2.32ꢂ
104 L molꢁ1 cmꢁ1).
1
precoated SiO2 plates Kieselgel 60F254 (Merck). H NMR
Procedure 2. Solutions of NaOH (3.03 M in H2O, 2.60 mL)
and H2O2 (30% in H2O, 0.40 mL) were added to 1,1,2-tri-
chlorotrifluoroethane (5 mL) at ꢁ6 ꢀC. Precooled C6F13COCl
(1.3 mL, 7.84 mmol) was added at the same temperature,
after 2 min the solution was allowed to reach 0 ꢀC and stirred
for further 5 min. The organic layer was quickly washed with
an ice-cold saturated aqueous NaHCO3 solution and water,
dried over Na2SO4, and kept at ꢁ78 ꢀC. The concentration
of acylperoxide solution was determined by iodometric titra-
tion of an aliquot (1 mL).10
(300 MHz) and 13C NMR (75 MHz) spectra were recorded
in CDCl3 on a Brucker Avance 300 spectrometer; chemical
shifts (d) are given in parts per million relative to Me4Si;
coupling constants (J) are given in Hertz. 19F NMR
(376 MHz) spectra were recorded in CDCl3 on a Varian
VNMR System 400 spectrometer; chemical shifts (d) are
given in parts per million relative to CFCl3. EIMS (70 eV)
and CIMS (NH3) spectra were recorded on a VG Micromass
7070F instrument; m/z with the lowest isotopic mass is
reported. Phase transition temperatures were measured by
differential scanning spectroscopy (Mettler Toledo DSC
821); heating and cooling rates 10 ꢀC minꢁ1; phase transi-
tions were determined from the onset of the second heating
curve. Optical textures of mesophases were observed with
polarizing microscope (Nikon Eclipse 80i).
In a Schlenk tube, a solution of terthiophene 4 (249 mg,
1.00 mmol) in CH2Cl2 (5 mL) was added to a solution con-
taining 0.5 mmol of acylperoxide. The mixture was de-
gassed by three freeze-pump-thaw cycles and then heated
for 3 h at 40 ꢀC. The mixture was cooled to the room temper-
ature, the organic phase was separated, washed with water,
dried over MgSO4, and concentrated in vacuum. Column
chromatography (hexane) afforded 6 (174 mg, 31%) as a
yellow solid. All analytical data were identical to those for
compound 6 prepared by the Procedure 1.
4.1.1. 5-Bromo-2,20:50,200-terthiophene (5). NBS (694 mg,
3.90 mmol) was added to a solution of terthiophene 4
(0.966 g, 3.89 mmol) in DMF (55 mL). The reaction mixture
was stirred for 24 h at room temperature and filtered. Water

D. Didier et al. / Tetrahedron 63 (2007) 941–946
945
4.1.3. 500-Bromo-5-tridecafluorohexyl-2,20:50,200-terthio-
phene (3). Prepared similarly to 5 from NBS (50 mg,
0.282 mmol) and 6 (160 mg, 0.282 mmol) in DMF (7 mL).
Crystallization from CH2Cl2 afforded pure 3 (124 mg,
68%). Yellow solid; mp 116 ꢀC; 1H NMR (300 MHz,
CDCl3, 25 ꢀC): d¼7.32–7.35 (m, 1H), 7.13–7.16 (m, 2H),
amount of CH2Cl2 caused precipitation of a yellow crystal-
line solid, which was filtered. Both solids were combined
and dried in vacuum. Crude 1 was then crystallized twice
from toluene and finally washed with MeOH to give 188 mg
1
(53%) of a yellow solid. DSC: Cr 200 ꢀC LC 213 ꢀC I; H
NMR (600 MHz, CDCl3, 25 ꢀC): d¼7.33 (d, 3JH,H¼3.6 Hz,
3
3
3
7.04 (d, JH,H¼3.9 Hz, 1H), 6.99 (d, JH,H¼3.9 Hz, 1H),
1H), 7.14 (d, JH,H¼4.2 Hz, 2H), 7.04–7.08 (m, 2H), 6.97
3
3
3
6.94 (d, JH,H¼3.9 Hz, 1H); 13C NMR (75 MHz, CDCl3,
(d, JH,H¼4.2 Hz, 1H), 6.95 (d, JH,H¼4.2 Hz, 1H), 6.67
25 ꢀC): d¼142.0, 138.0, 137.0, 134.4, 131.2, 130.8, 127.1,
125.9, 124.7, 124.3, 123.5, 111.8; HREIMS: m/z: calcd for
C18H679BrF13S3 ([M]+): 643.8601; found 643.8561; EIMS:
m/z (%)¼644 (50), 376 (48), 374 (44), 126 (100).
(d, 3JH,H¼3.6 Hz, 1H), 2.81 (t, 3JH,H¼7.8 Hz, 2H), 1.70 (q,
3JH,H¼7.8 Hz, 2H), 1.20–1.40 (m, 10H), 0.90 (t, JH,H
¼
3
6.9 Hz, 3H). 13C NMR (75 MHz, CDCl3, 25 ꢀC): d¼145.7,
134.3, 125.9, 124.9, 124.8, 124.0, 123.6, 123.5, 123.1,
32.0, 31.7, 30.3, 29.5, 29.4, 29.2, 22.9, 14.2 (signals of
C–F and of some aromatic C were not observed because
of the 19F–13C coupling resulting in the low intensity of
4.1.4. 2-Bromo-5-octyl-thiophene (9). A solution of NBS
(4.53 g, 0.0255 mol) in DMF (20 mL) was added dropwise
at 0 ꢀC to a solution of 2-octylthiophene 8 (5.00 g,
0.0255 mol) in DMF (5 mL). The mixture was stirred for
16 h at room temperature and then partitioned between water
(10 mL) and hexane (50 mL). The organic layer was washed
with water, dried over MgSO4, and concentrated in vacuum.
Column chromatography (hexane) afforded 9 (6.46 g, 92%).
19
signals); F NMR (282 MHz, CDCl3, 25 ꢀC): d¼ꢁ81.1
(3F), ꢁ101.4 (2F), ꢁ121.7 (4F), ꢁ123.7 (2F), ꢁ126.4
(2F). HREIMS: m/z: calcd for C30H25F13S4 ([M]+):
760.0631; found 760.0590; EIMS: m/z (%)¼760 (100),
661 (30), 392 (14); UV (hexane): lmax (3)¼398 nm (2.97ꢂ
104 L molꢁ1 cmꢁ1).
1
Colorless liquid; H NMR (300 MHz, CDCl3, 25 ꢀC):
3
3
d¼6.82 (d, JH,H¼3.7 Hz, 1H), 6.52 (d, JH,H¼3.7 Hz,
4.1.7. ( )-(S,S/R,R)- and ( )-(S,R/R,S)-4,8-Dimethyl-
1-(2,20:50,200-terthiophen-5-yl)-nonan-1-ol (11), mixture
of diastereoisomers. 1,2-Dibromoethane (0.067 mL,
0.078 mmol) was added to the suspension of Mg turnings
(162 mg, 6.66 mmol) in dry Et2O (8 mL). The solution was
heated until continuous gas evolution was observed, then
(ꢃ)-1-bromo-3,7-dimethyloctane (0.945 mL, 4.44 mmol)
was added and the mixturewas heated to reflux for 1 h. A sus-
pension of aldehyde 10 (307 mg, 1.11 mmol) in dry Et2O
(2.5 mL) was added and the heating was continued for 1 h.
The mixture was cooled to room temperature and water
(20 mL) was added. The resulting mixture was stirred for
30 min, the organic phase was separated and the aqueous
phase was extracted with Et2O/hexane (1:1). Combined or-
ganic phases were washed with water, dried over Na2SO4,
and concentrated in vacuum. Column chromatography
(hexane/CH2Cl2 9:1) afforded 11 (443 mg, 95%) as an
amorphous brown solid; 1H NMR (300 MHz, CDCl3,
1H), 2.72 (t, 3JH,H¼7.2 Hz, 2H), 1.62 (quint, 3JH,H¼7.2 Hz,
2H), 1.20–1.40 (m, 10H), 0.88 (t, JH,H¼6.9 Hz, 3H); 13C
3
NMR (75 MHz, CDCl3, 25 ꢀC): d¼147.6, 129.3, 124.3,
108.5, 31.8, 31.4, 30.3, 29.3, 29.2, 29.0, 22.6, 14.1.
4.1.5. 4,4,5,5-Tetramethyl-2-(5-octylthiophen-2-yl)-1,3,2-
dioxaborolane (7). A solution of bromide 9 (462 mg,
1.68 mmol) in THF (14 mL) was cooled to ꢁ70 ꢀC, and a
1.43 M solution of n–BuLi in hexane (1.44 mL, 2.057 mmol)
was added. The mixture was allowed to reach room temper-
ature, stirred for 1 h, and cooled again to ꢁ70 ꢀC. Triethyl-
borate (1.91 mL, 11.22 mmol) was added, the mixture was
allowed to reach room temperature and stirred for 1 h.
Pinacol (1.436 g, 12.16 mmol) was added and stirring was
continued for further 16 h, then the mixture was partitioned
between CH2Cl2 (15 mL) and water (60 mL). The organic
phase was washed with water (3ꢂ60 mL), dried over MgSO4,
and concentrated in vacuum. Column chromatography (hex-
ane, then CH2Cl2/AcOEt 1:1) afforded 7 (0.320 g, 59%) as
an orange oil; 1H NMR (300 MHz, CDCl3, 25 ꢀC): d¼7.47
3
4
25 ꢀC): d¼7.26 (dd, JH,H¼5.1 Hz, JH,H¼1.2 Hz, 1H),
3
4
7.21 (dd, JH,H¼3.6 Hz, JH,H¼1.2 Hz, 1H), 6.96–7.09 (m,
3
3
4H), 6.87 (d, JH,H¼3.6 Hz, 1H), 4.39 (t, JH,H¼6.9 Hz,
1H), 1.10–2.00 (m, 12H), 0.8–0.92 (m, 9H); 13C NMR
(75 MHz, CDCl3, 25 ꢀC): d¼147.19, 147.10, 136.10,
135.28, 135.24, 135.20, 135.12, 126.85, 123.55, 123.47,
123.44, 123.28, 123.09, 122.65, 122.07, 122.06, 69.90,
69.82, 38.26, 36.06, 35.73, 35.68, 31.86, 31.64, 26.94,
23.73, 23.68, 21.69, 21.59, 18.62, 18.59; HREIMS: m/z:
calcd for C23H30OS3 ([M]+): 418.1458; found 418.1510;
EIMS: m/z (%)¼418 (65, [M]+), 400 (27, [MꢁH2O]+), 287
(48), 277 (100), 261 (53), 57 (37); UV(MeOH): lmax
(3)¼357 nm (1.72ꢂ104 L molꢁ1 cmꢁ1).
3
3
(d, JH,H¼3.3 Hz, 1H), 6.86 (d, JH,H¼3.3 Hz, 1H), 2.84
(t, 3JH,H¼7.5 Hz, 2H), 1.68 (quint, 3JH,H¼7.6 Hz, 2H), 1.33
(s, 12H), 1.18–1.40 (m, 10H), 0.82–0.92 (m, 3H); 13C
NMR (75 MHz, CDCl3, 25 ꢀC): d¼153.7, 137.3, 125.7,
83.8, 31.8, 31.6, 30.1, 29.3, 29.2, 29.0, 24.7, 22.6, 14.0;
HREIMS: m/z: calcd for C18H31BO2S ([M]+): 322.2138;
found: 322.2132; EIMS: m/z (%)¼322 (100), 320 (17), 307
(14), 236 (11), 224 (30), 223 (79), 222 (14).
4.1.6. 5-Octyl-5000-tridecafluorohexyl-2,20:50,200:500,2000-
quaterthiophene (1). Boronate 7 (227 mg, 0.704 mmol) in
EtOH (2 mL) and K2CO3 (390 mg, 2.82 mmol) in water
(1 mL) were added to a solution of bromide 3 (0.303 mg,
0.470 mmol) and [Pd(PPh3)4] (55 mg, 0.0475 mmol) in
toluene (10 mL). The mixture was heated at 80 ꢀC for 5 h,
cooled to room temperature and diluted with CH2Cl2. The
organic layer was filtered through the sintered glass filter
and the yellow solid was washed with CH2Cl2. Combined or-
ganic phases were washed with water (3ꢂ20 mL), dried over
MgSO4, and concentrated in vacuum. Addition of a small
4.1.8. ( )-5-(4,8-Dimethylnonyl)-2,20:50,200-terthiophene
(14). ZnI2 (437 mg, 1.369 mmol) and Na[BH3CN] (446 mg,
7.097 mmol) were added to a solution of alcohol 11
(424 mg, 1.01 mmol) in dry 1,2-dichloroethane (30 mL).
The reaction mixture was stirred for 72 h at room tempera-
ture and filtered through Celite. The Celite cake was
washed with CH2Cl2 (50 mL) and combined filtrates were
evaporated. Column chromatography (hexane) afforded
14 (364 mg, 89%). Amorphous yellow solid; 1H NMR

946
D. Didier et al. / Tetrahedron 63 (2007) 941–946
3
(300 MHz, CDCl3, 25 ꢀC): d¼7.20 (dd, JH,H¼5.1 Hz,
filtered through the glass filter. The solid on the filter was
excessively washed with water and toluene and dried in
vacuum. Orange solid; yield 74 mg (55%); 1H NMR
(300 MHz, CDCl3, 25 ꢀC): d¼7.42–7.50 (m, 1H), 6.92–7.12
(m, 10H), 6.60–6.68 (m, 1H), 2.76–2.82 (m, 2H), 1.10–1.80
(m, 12H), 0.80–0.96 (m, 9H). HRCIMS (NH3): m/z: calcd
for C41H35F13S6 ([M]+): 966.0855; found 966.1140; CIMS
(NH3): m/z (%)¼966 (100, [M]+), 826 (12); UV (CH2Cl2):
lmax (3)¼432 nm (1.31ꢂ104 L molꢁ1 cmꢁ1).
3
4
4JH,H¼1.2 Hz, 1H), 7.15 (dd, JH,H¼3.6 Hz, JH,H¼1.2 Hz,
3
1H), 7.05 (d, JH,H¼3.9 Hz, 1H), 6.96–7.03 (m, 3H), 6.68
3
3
(d, JH,H¼3.6 Hz, 1H), 2.77 (t, JH,H¼7.5 Hz, 2H), 1.00–
1.80 (m, 12H), 0.80–0.90 (m, 9H); 13C NMR (75 MHz,
CDCl3, 25 ꢀC): d¼145.5, 137.3, 136.8, 135.4, 134.4, 127.8,
124.8, 124.28, 124.22, 123.43, 123.40, 123.3, 39.3, 37.2,
36.4, 32.6, 30.5, 29.1, 28.0, 24.8, 22.7, 22.6, 19.6; HREIMS:
m/z: calcd for C23H30S3 ([M]+): 402.1509; found: 402.1489;
EIMS: m/z (%)¼402 (88, [M]+), 261 (100); UV (MeOH):
lmax (3)¼358 nm (2.20ꢂ104 L molꢁ1 cmꢁ1).
Acknowledgements
4.1.9. ( )-500-Bromo-5-(4,8-dimethylnonyl)-2,20:50,200-ter-
thiophene (15). Prepared similarly to 5 from NBS (40 mg,
0.223 mmol) and 14 (89.7 mg, 0.223 mmol) in DMF (5 mL).
Crystallization from CH2Cl2 afforded pure 15 (104 mg,
We thank J. Leroy for the synthesis of 9 and R. d’Orazio and
M. Luhmer for the measurement of NMR spectra.
1
97%). Brown solid; mp 107–109 ꢀC; H NMR (300 MHz,
CDCl3, 25 ꢀC): d¼6.95–6.99 (m, 4H), 6.88 (d, 3JH,H¼3.9 Hz,
1H), 6.68 (d, 3JH,H¼3.6 Hz, 1H), 2.77 (t, 3JH,H¼7.2 Hz, 2H),
1.00–1.80 (m, 12H), 0.80–0.92 (m, 9H); 13C NMR (75 MHz,
CDCl3, 25 ꢀC): d¼145.9, 138.8, 137.3, 134.3, 134.2, 130.6,
124.9, 124.5, 123.6, 123.5 (2C), 110.8, 39.3, 37.2, 36.6, 32.6,
30.5, 29.1, 28.0, 24.8, 22.7, 22.6, 19.6; HREIMS: m/z: calcd
for C23H2979BrS3 ([M]+): 480.0615; found 480.0635; EIMS:
m/z (%)¼480 (100, [M]+), 340 (97), 338 (90); UV(MeOH):
lmax (3)¼363 nm (2.52ꢂ104 L molꢁ1 cmꢁ1).
References and notes
1. Horowitz, G. Adv. Mater. 1998, 10, 365.
2. Funahashi, M.; Hanna, J. Adv. Mater. 2005, 17, 594.
3. Facchetti, A.; Deng, Y.; Wang, A.; Koide, Y.; Sirringhaus, H.;
Marks, T. J.; Friend, R. H. Angew. Chem., Int. Ed. 2000, 39,
4547.
4. Facchetti, A.; Yoon, M.-H.; Stern, C. L.; Hutchison, G. R.;
Ratner, M. A.; Marks, T. J. J. Am. Chem. Soc. 2004, 126, 13480.
5. Ishiyama, T.; Murata, M.; Miyaura, N. J. Org. Chem. 1995, 60,
7508.
6. (a) McLoughlin, V. C. R.; Thrower, J. Tetrahedron 1969,
25, 5921; (b) Leroy, J.; Rubinstein, M.; Wakselman, C.
J. Fluorine Chem. 1984, 27, 291; (c) Chen, G. J.; Chen, L. S.
J. Fluorine Chem. 1995, 73, 113.
4.1.10. ( )-2-[500-(4,8-Dimethylnonyl)-2,20:50,200-terthio-
phen-5-yl]-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (16).
n–BuLi (1.66 M in hexane, 0.190 mL, 0.315 mmol) was
added to dry THF (1.6 mL) at ꢁ78 ꢀC, then a solution of
bromide 15 (150 mg, 0.311 mmol) in dry THF (2.6 mL)
was added dropwise and the mixture was stirred for 1 h at
ꢁ78 ꢀC. Then the mixture was allowed to reach 10 ꢀC,
cooled again to ꢁ78 ꢀC and 2-isopropoxy-4,4,5,5-tetra-
methyl-1,3,2-dioxaborolane (0.08 mL, 0.404 mmol) was
added in one portion via syringe. The resulting mixture
was stirred for 30 min at ꢁ78 ꢀC, then allowed to reach
room temperature and stirred for further 3 h. The mixture
was poured into 15 mL of Et2O, and a mixture of HCl
(1 M in H2O, 0.40 mL) and ice-cold water (15 mL) was
added. The organic phase was separated, washed with water,
dried over Na2SO4, and concentrated in vacuum to afford 16
as a green solid (120 mg, 72%), which was used without fur-
7. (a) Mac Eachern, A.; Soucy, C.; Leitch, L. C.; Arnason, J. T.;
€
Morand, P. Tetrahedron 1988, 44, 2403; (b) Bauerle, P.;
€
€
Wurthner, F.; Gotz, G.; Effenberger, F. Synthesis 1993, 1099.
8. Sawada, H.; Yoshida, M.; Hagii, H.; Aoshima, K.; Kobayashi,
M. Bull. Chem. Soc. Jpn. 1986, 59, 215.
9. Chengxue, Z.; Renmo, Z.; Heqi, P.; Xiangshan, J.; Yangling,
Q.; Chengjiu, W.; Xikui, J. J. Org. Chem. 1982, 44, 2009.
10. Walling, C.; Cekovic, Z. J. Am. Chem. Soc. 1967, 89, 6681.
11. Pabst, G. R.; Pf€uller, O. C.; Sauer, J. Tetrahedron 1999, 55,
8045.
12. Boyd, T. J.; Geerts, Y.; Lee, J.-K.; Fogg, D. E.; Lavoie, G. G.;
Schrock, R. R.; Rubner, M. F. Macromolecules 1997, 30, 3553.
13. Hof, F.; Schar, M.; Scofield, D. M.; Fischer, F.; Diederich, F.;
1
ther purification. H NMR (300 MHz, CDCl3, 25 ꢀC):
€
3
3
d¼7.52 (d, JH,H¼3.60 Hz, 1H), 7.21 (d, JH,H¼3.60 Hz,
Sergeyev, S. Helv. Chim. Acta 2005, 88, 2333.
14. Dierking, I. Textures of Liquid Crystals; Wiley-VCH:
Weinheim, 2003; p 91.
1H), 7.11 (d, 3JH,H¼3.90 Hz, 1H), 6.97–7.01 (m, 2H), 6.68
3
3
(d, JH,H¼3.30 Hz, 1H), 2.77 (t, JH,H¼7.6 Hz, 2H), 1.35
€
(s, 12H), 1.10–1.70 (m, 12H), 0.80–0.92 (m, 9H).
15. Urban, S.; Massalska-Arodz, M.; Wurflinger, A.; Czuprynski,
K. Z. Naturforsch., A: Phys. Sci. 2002, 57a, 641.
16. (a) Leroy, J.; Levin, J.; Sergeyev, S.; Geerts, Y. Chem. Lett.
2006, 35, 166; (b) Collard, D. M.; Lillya, C. P. J. Am. Chem.
Soc. 1991, 113, 8577.
17. Parakka, J. P.; Cava, M. P. Tetrahedron 1995, 51, 2229.
18. Lau, C. K.; Dufresne, C.; Belanger, P. C.; Pietre, S.; Scheigetz,
J. J. Org. Chem. 1986, 51, 3038.
19. Ponomarenko, S. A.; Kirchmeyer, S.; Elschner, A.; Alpatova,
N. M.; Halik, M.; Klaus, H.; Schmid, G. Chem. Mater. 2006,
18, 579.
4.1.11. 5-(4,8-Dimethylnonyl)-500000-tridecafluorohexyl-
2,20:50,200:500,2000:5000,20000:50000,200000-sexithiophene (2). A solu-
tion of boronate 16 (103 mg, 0.195 mmol) in dry toluene
(2.5 mL), a solution of Na2CO3 in water (2 M, 0.580 mL),
bromide 3 (90 mg, 0.139 mmol), and [Pd(PPh3)4] (10 mg,
0.008 mmol) was mixed in the Schlenk tube, Ar atmosphere
was secured and the mixture was heated to reflux for 16 h.
After cooling to the room temperature, the mixture was parti-
tioned between toluene (50 mL) and water (25 mL) and then