Homologous series of regioregular alkylsubstituted oligothiophenes up to an 11-mer

Article abstract of DOI:10.1016/S0040-4020(01)00254-X

A complete series of structurally well-defined butylated oligothiophenes up to an 11-mer was synthesized by a combination of aryl-aryl cross-coupling reactions and cyclization of 1,3-butadiyne precursors with sulfide anions. Palladium-catalyzed cross-coupling of halogenated thiophene units with trimethylsilylacetylene effectively yields ethynylated thiophenes which after deprotection are oxidatively coupled to the corresponding 1,3-butadiynes.

Full text of DOI:10.1016/S0040-4020(01)00254-X

TETRAHEDRON
Pergamon
Tetrahedron 57 42001) 3785±3794
Homologous series of regioregular alkylsubstituted
oligothiophenes up to an 11-mer
²
Jens Kromer and Peter Bauerle
p
È
È
Department of Organic Chemistry II ꢀOrganic Materials and Combinatorial Chemistry), University of Ulm,
Albert-Einstein-Allee 11, D-89081 Ulm, Germany
Received 10 November 2000; accepted 12 January 2001
AbstractÐA complete series ofstructurally well-de®ned butylated oligothiophenes up to an 11-mer was synthesized by a combination of
aryl±aryl cross-coupling reactions and cyclization of1,3-butadiyne precursors with sul®de anions. Palladium-catalyzed cross-coupling of
halogenated thiophene units with trimethylsilylacetylene effectively yields ethynylated thiophenes which after deprotection are oxidatively
coupled to the corresponding 1,3-butadiynes. q 2001 Published by Elsevier Science Ltd.
1. Introduction
estingly, it was shown that conjugation along the one-
dimensional chain is saturated after 20 repeating units.6a
Our aim now was to evaluate synthetic routes to ®nally
obtain a complete homologous series oflinear b-alkyl-
substituted a-conjugated oligothiophenes consisting of
members in which the chain length only varies by bithio-
phene units 4Scheme 1).
Owing to their de®ned structure, chain and conjugation
length, a-conjugated oligothiophenes represent the most
frequently investigated model compounds for conducting
polymers.1 Various series ofoligothiophenes which were
preferably alkylated and therefore soluble, have been
synthesized and the physical properties are well correlated
to the 4conjugated) chain length. Thus, structure±property
relationships become available and valuable information
can be deduced which is normally not obtainable from the
corresponding polymers due to their polydisperse nature.1,2
Moreover, the study on de®ned oligomers led to novel
organic materials and a-conjugated oligothiophenes have
recently successfully been used as active components in
organic ®eld-effect transistors,3 light-emitting devices,4 or
photovoltaic solar cells.5
Scheme 1.
2. Results and discussion
Several synthetic routes to linear a-conjugated oligothio-
phenes have recently been established, however, their
syntheses by step-wise assembly ofde®ned units are
typically tedious with respect to 4isomeric) purity and
yield, particularly for longer oligomers.1 Two different
general routes are widely used, either transition metal-cata-
lyzed aryl±aryl cross-coupling reactions ofthiophene build-
ing blocks or ring closure reactions from acyclic precursors.
Very recently, oligothiophenes comprising chain lengths
exceeding the mean conjugation length ofcorresponding
polymers by far were synthesized and characterized.6 Inter-
2.1. Synthesis of alkylsubstituted oligothiophenes via
nickel-catalyzed cross-coupling reactions
For the synthesis ofthe oligothiophene series 3,4-dibutyl-
thiophene 1 was chosen as the key building block in order to
provide suf®cient solubility of particularly the longer oligo-
mers in organic solvents. In contrast to the use of
3-alkylthiophene units, symmetric 3,4-dibutylthiophene 1
guarantees isomerically pure products, because regio-
irregular couplings are avoided.7 Sterically demanding
substituents in oligo- or polythiophenes typically lead to a
distortion ofthe conjugated backbone and consequently to
a reduced effective conjugation length. In particular,
3,30-substituted bithiophene units result in a nearly perpen-
dicular conformation of adjacent thiophene rings and give
rise to higher redox potentials and optical band gaps.1b
Therefore, in our oligomers each second thiophene ring
Keywords: conjugated oligomers; oligothiophenes; metal-catalyzed cross-
coupling reactions.
p
Corresponding author. Tel.: 149-731-502-2850; fax: 149-731-502-
2840; e-mail: peter.baeuerle@chemie.uni-ulm.de
Present address: Henkel KGaA, Henkelstr. 67, D-40191 DuÈsseldorf,
Germany.
²
0040±4020/01/$ - see front matter q 2001 Published by Elsevier Science Ltd.
PII: S0040-4020401)00254-X

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J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3786
Scheme 2.
was not substituted. Owing to this alternating pattern, at
the same time suf®cient solubility and minimized steric
interactions between individual thiophene rings is achieved
which ideally provides structurally de®ned model
compounds for polythiophenes.
2.2. Introduction of ethynyl groups into the
oligothiophene core
Besides transition metal-catalyzed aryl±aryl cross-coupling
reactions, for the synthesis of oligothiophenes various
methods starting from acyclic precursor molecules have
been established. 1,4-Diketones can be cyclized by means
ofsuulfr donors such as phosphorous pentasul®de or
Lawesson's reagent to the corresponding thiophenes in
good yields.6i,9 However, as a side reaction, direct dehydra-
tisation ofthe 1,4-diketone may lead to ufrans which are
dif®cult to separate.10 In contrast, cyclization of1,3-buta-
diynes with sul®de anions to the corresponding thiophenes
is more generally applicable.11 In particular, longer
oligothiophenes are accessible by this method via random
oligomerization ofbis- and mono-ufnctionalized building
blocks and their successive chromatographic separation.6a,6b
3,4-Dibutylthiophene 1 was synthesized according several
literature procedures in 29% overall yield starting from thio-
phene via tetrabromothiophene and 3,4-dibromothiophene.
Bromination of 1 with one equivalent NBS in DMF8 gave
2-bromo-3,4-dibutylthiophene 2 in 69% yield and with two
equivalents 2,5-dibromo-3,4-dibutylthiophene 3 in 84%
yield 4Scheme 2). Nickel-catalyzed cross-coupling ofthe
Grignard reagent ofbromothiophene 2 and 2,5-dibromo-
thiophene 4 resulted in the next higher homologue, tetra-
butyl-terthiophene 5, in 82% yield 4Scheme 3). Similarly,
`Kumada-coupling' of2-thienylmagnesium bromide 60 and
dibromothiophene 3 with Ni4dppp)Cl2 as catalyst gave
30,40-dibutylterthiophene 7 493% yield) which successively
was brominated with the system NBS/DMF to yield the
corresponding dibromo compound 8 491% yield). In a
further nickel-catalyzed coupling, the latter was reacted
with the Grignard reagent ofbromothiophene 2 to hexa-
butyl-quinquethiophene 9 in 76% yield 4Scheme 4).
Owing to homo-couplings, 3,30,4,40-tetrabutyl-2,20-bithio-
phene was formed as a side product 47% yield) which was
easily separated by chromatography. For the synthesis ofthe
higher homologues, however, aryl±aryl coupling reactions
proved to be less effective and face several problems, i.e.
selective metallation ofoligothiophenes and an increasing
portion ofhomo-coupling products which become more
dif®cult to separate and ®nally results in gradually decreased
yields.
Thienyl-substituted 1,3-butadiynes are obtained by oxida-
tive dimerization ofthiophene-acetylenes.
6a,6b,12
We have
evaluated the effective introduction of ethynyl groups at
the oligothiophene core by using tetrabutyl-terthiophene 5
as an example. The Corey±Fuchs method for the prepa-
ration of2-ethynylthiophenes combines Vilsmeier ofrmyl-
ation and the Wittig reaction.11,13 Terthiophene 5 was
selectively formylated with POCl3 and DMF in dichloro-
ethane to give monoaldehyde 10 in 77% yield. Wittig
reaction ofthe latter compound and a mixture oftetra-
bromomethane and triphenylphosphane effectively resulted
in 1,1-dibromoethylene-terthiophene 11 485% yield) which
is by reaction with n-butyl lithium subsequently trans-
formed to the monoethynylated terthiophene 12 4Scheme
5). Due to the inherent instability ofthese acetylene
Scheme 3.
Scheme 4.

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J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3787
Scheme 5.
derivatives and side reactions 4alkylation at the 5-position
with n-BuLi), only moderate yields were obtained 447%).
dium-catalyzed couplings ofeach compound and tri-
methylsilylacetylene gave coresponding TMS-protected
2-ethynylthiophene 17 in 66% and 5-ethynylquinquethio-
phene 19 in 69% yield 4Scheme 7).
The Sonogashira±Hagihara coupling ofacetylenes and
halogenated 4het)arenes is an interesting alternative for
the synthesis ofmonoethynylated oligothiophenes.
6a,6b,14
2.3. Copper-promoted coupling of ethynylated
oligothiophenes to 1,3-butadiynes and their cyclization
to oligothiophenes with sul®de anions
Despite the general problem to selectively monobrominate
oligothiophenes, terthiophene 5 was ®rst reacted with the
system NBS/DMF to give after chromatographic work-up
and separation from dibromoterthiophene 14 5-bromo
derivative 13 in 52% yield 4Scheme 6). Subsequent palla-
dium-catalyzed reaction ofbromoterthiophene 13 and
trimethylsilylacetylene went very smoothly to result in
TMS-protected 5-ethynylterthiophene 18 in 73% yield
4Scheme 7).
Symmetric 1,3-butadiynes are accessible in good yields
through oxidative coupling ofacetylenes with the aid of
copper salts.6a,6b,12 Pioneering work ofHay demonstrated
that the system Cu4I)Cl/TMEDA in acetone or dichloro-
methane is very effective to couple ethynylated benzenes
at moderate temperatures.15 We used this methodology to
dimerize ethynylated thiophenes 17±19 after deprotection
by hydroxide in situ to the bis4oligo)thiophene-1,3-buta-
diynes 20±22 in 73, 77, and 65% yield, respectively,
which represent stable crystalline solids 4Scheme 7).
Ifone compares both methods ofr the preparation of
ethynylated terthiophenes 12 and 18 the latter method
comprises minor advantages with respect to the overall
yield 438% vs. 31%) and to practicality. Therefore, the
same methodology was applied to bromothiophene 2 and
bromoquinquethiophene 15 which was analogously synthe-
sized from pentamer 9 and NBS/DMF in 42% yield. Palla-
Kagan et al. reported that dithienylbutadiynes quantitatively
react with sodium sul®de in boiling methanol to give the
corresponding terthiophenes in excellent yields.11,13 We
Scheme 6.
Scheme 7.

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J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3788
Scheme 8.
optimized this protocol for our 4oligo)thiophenebutadiynes
and found that the butyl side chains exert steric constraints
on adjacent diyne units so that the temperature had to be
raised. Analogous reaction of4oligo)thiophenebutadiynes
20±22 with sodium sul®de nonahydrate in boiling 2-meth-
oxyethanol cleanly gave trimer 5 in 61%, heptamer 23 in
80%, and undecamer 24 in 73% yield, respectively 4Scheme
7).
coupling reactions; higher homologues were obtained by a
sequence including `Sonogashira±Hagihara' coupling and
introduction ofacetylene groups to the thiophene core,
followed by an oxidative dimerization under `Hay' con-
ditions and ®nal cyclization ofthe resulting butadiynes
with sul®de to the various oligothiophenes. Due to their
excellent solubility, the characterization ofthe physical
properties in dependence ofthe chain length leads to excel-
lent structure±property relationships. This will be reported
elsewhere.
2.4. Synthesis of a nonamerÐnonithiophene 28
By the procedures described above the whole homologous
series ofalkylated oligothiophenes except the nonamer
could be synthesized. Therefore, quinquethiophene 9 was
iodinated with elemental iodine in the presence ofmercuric
acetate to give diiodoquinquethiophene 25 in 87% yield,
which was further reacted with TMS±acetylene under palla-
dium catalysis to the twofold ethynylated pentamer 26 470%
yield). After deprotection, this bis-functionalized oligothio-
phene was coupled under `Hay conditions' with mono-
ethynylthiophene 17 as a `capping reagent'. Besides
dithienylbutadiyne 20 which is formed in 21% yield as a
homo-coupling product and higher molecular weight
products, oligomer 27 was isolated in 17% yield after
chromatographic work-up. Final cyclization ofthe two
diyne units with sodium sul®de in 2-methoxyethanol gave
the desired nonithiophene 28 in 69% yield 4Scheme 8).
3. Experimental
1H/13C NMR: AMX 500, ACF 250, AC 200; TMS internal
standard. MS: Finnigan MAT 8200 and SSQ 7000 4EI:
70 eV), Finnigan MAT 95 4FAB), Bruker Daltonik Re¯ex
III 4MALDI±TOF). IR: Perkin±Elmer FTIR Spectrum
2000. Elemental analyses: Perkin±Elmer EA 240 and
EA 2400 in the Division ofAnalytical Chemistry ofthe
University ofUlm. Melting points 4uncorrected): BuÈchi
B-545. TLC: Macherey±Nagel SIL G/UV254. Column
chromatography 4CC): Silica gel 60 40.020±0.200 mm).
Gas chromatography 4GC): Carlo±Erba Auto-HRGC MFC
500, PS086 glass capillary column, 10 m and 20 m. HPLC:
Shimadzu SCL-10AVP controller, LC-10AT pump, SPD-
M10AVP detector, Macherey±Nagel nucleosil column NO2
44 mm£250 mm, corn diameter 5 mm). Preparative HPLC:
Shimadzu LC-8A pump, SPD-10A detector, Macherey±
Nagel nucleosil column NO2 440 mm£250 mm, corn
diameter 100±10 mm). All solvents and reagents were
puri®ed and dried according to common procedures prior
to use. All reactions were performed under an argon atmos-
phere.
In conclusion, a complete homologous series ofbutylated
linear a-conjugated oligothiophenes 41T, 3T, 5T, 7T, 9T,
11T) was prepared. The new approach involves a combi-
nation oftwo basic synthetic routes. Oligothiophenes up to
the corresponding quinquethiophene were synthesized on
large scale 4.10 g) by nickel-catalyzed `Kumada' cross-

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J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3789
3.1. Starting materials
0.96 4t, 6 H, ±CH3), 1.48 4m, 8 H, b,g-CH2), 2.66 4m, 4 H,
3
a-CH2), 6.87 4d, Jˆ3.1 Hz, 2 H, H-3,300), 7.01 4d,
Commercially available: [1,3-Bis4diphenylphosphino)pro-
pane]nickel4II)-chloride 4Aldrich), bis4triphenylphosphine)-
palladium4II)-chloride
3Jˆ3.1 Hz, 2 H, H-4,400). 13C NMR 4126 MHz, CDCl3) d
13.8 4±CH3), 22.9 4g-CH2), 27.8 4a-CH2), 32.9 4b-CH2),
112.0 4C-5,500), 126.2 4C-3,300), 129.4 4C-20,50), 130.2
4C-4,400), 137.4 4C-2,200), 140.5 4C-30,40). Anal. Calcd for
C20H22Br2S3 4518.4): C, 46.34; H, 4.28; S, 18.55. Found C,
46.44; H, 4.27; S, 18.45.
4Merck),
N-bromosuccinimid
4Aldrich), 2-bromothiophene 4Aldrich), n-butyl lithium 41.6N
in n-hexane, Merck), 2,5-dibromothiophene 4ABCR),
iodine 4Merck), copper4I)-chloride 4Merck), copper4II)-
chloride 4Merck), copper4I)-iodide 4Aldrich), magnesium
4Merck), magnesium sulfate 4Merck), sodium sul®de nona-
hydrate 4Fluka), thiophene 4Merck). Prepared according to
literature procedures: tetrabromothiophene 467%, mp 113±
1148C),16 3,4-dibromothiophene 455%, bp 104±1058C/
20 mbar),17 3,4-dibutylthiophene 41) 479%, bp 60±628C;
1022 mbar),18 30,40-dibutyl-2,20:50,200-terthiophene 47)
493%, oil),19 trimethylsilylacetylene 435%, bp 52±538C).20
3.2.4.
5-Bromo-3,300,4,400-tetrabutyl-2,20:50,200-terthio-
phene 513). According to GP1, NBS 44.14 g, 23.3 mmol)
in 150 ml DMF, tetrabutylterthiophene 45) 410.00 g,
21.1 mmol) in 300 ml DMF, 1 h, 6 h, chromatographic
work-up 4SiO2; petroleum ether/dichloromethane 12:1),
yield 6.05 g 411.0 mmol, 52%) yellow oil. 1H NMR
4500 MHz, CDCl3) d 0.94 4t, 12 H, ±CH3), 1.52 4m, 16 H,
b,g-CH2), 2.55 4m, 4 H, a-CH2), 2.72 4m, 4 H, a-CH2),
3
6.87 4s, 1H, H-500), 7.00 [d, Jˆ3.8 Hz, 1 H, H-40 4or 30)],
3.2. General procedure for the bromination of
thiophenes with NBS in DMF 5GP1)
7.03 [d, 3Jˆ3.8 Hz, 1 H, H-30 4or 40)]. 13C NMR 4126 MHz,
CDCl3) d 13.97, 13.87, 13.81 4±CH3), 22.95, 22.88, 22.81,
22.67 4g-CH2), 28.90, 28.42, 28.21, 27.50 4a-CH2), 32.93,
32.69, 31.90, 31.80 4b-CH2), 108.5 4C-5), 119.2 4C-500),
143.6, 142.6, 139.0, 138.8, 137.2, 135.1, 131.0, 130.6,
126.3, 125.8 4C-2,3,4,20,30,40,50,200,300,400). MS 4EI) m/z
4%): 554 415) [M1], 553 430) [M1], 552 4100) [M1], 551
428) [M1], 550 487) [M1]. Anal. Calcd for C28H39BrS3
4551.7): C, 60.96; H, 7.13; S, 17.43. Found C, 61.02; H,
7.23; S, 17.21.
In the absence oflight and at 0 8C, a solution ofNBS in DMF
was added dropwise over a period ofseveral hours to a
solution ofthe thiophene in DMF, and the mixture was
stirred for several hours at ambient temperature, poured
onto ice, and extracted with diethyl ether. The organic
phases were combined, washed with water, and dried over
sodium sulfate. Evaporation of the solvent and either distil-
lation under reduced pressure or chromatographic work-up
4phase; eluent) yielded the desired brominated thiophenes.
3.2.5. 5,500-Dibromo-3,300,4,400-tetrabutyl-2,20:50,200-ter-
thiophene 514). According to GP1, NBS 47.48 g,
42 mmol) in 200 ml DMF, tetrabutylterthiophene 45)
49.45 g, 20 mmol) in 100 ml DMF, 1 h, 3 h, chromato-
graphic work-up 4SiO2; n-hexane/dichloromethane 10:1),
yield 10.7 g 416.8 mmol, 84%) yellow solid, mp 35±368C.
1H NMR 4250 MHz, CDCl3) d 0.96 4m, 12 H, ±CH3), 1.48
4m, 16 H, b,g-CH2), 2.55 4t, 4 H, a-CH2), 2.71 4t, 4 H,
a-CH2), 6.89 4s, 2 H, H-30,40). 13C NMR 463 MHz,
CDCl3) d 13.89, 13.95 4±CH3), 22.85, 22.94 4g-CH2),
28.24, 28.44 4a-CH2), 31.84, 32.97 4b-CH2), 108.7
4C-5,500), 126.3 4C-30,40), 130.7, 135.7, 139.0, 142.6
4C-2,3,4,20,50,200,300,400). MS 4EI) m/z 4%):632 463) [M1],
630 4100) [M1], 628 450) [M1]. Anal. Calcd for
C28H38Br2S3 4630.6): C, 53.33; H, 6.07; S, 15.25. Found
C, 53.23; H, 5.95; S, 15.05.
3.2.1. 2-Bromo-3,4-dibutylthiophene 52). According to
GP1, NBS 427.10 g, 152.3 mmol) in 200 ml DMF, 3,4-di-
butylthiophene 41) 429.90 g, 152.3 mmol) in 200 ml DMF,
4 h, 18 h, distillation, yield 28.92 g 469%), slightly yellow
liquid, bp 84±868C 41022 mbar). 1H NMR 4500 MHz,
CDCl3) d 0.97 4t, 6 H, ±CH3), 1.52 4m, 8 H, b,g-CH2),
2.54 4m, 4 H, a-CH2), 6.86 4s, 1 H, H-5). 13C NMR
4126 MHz, CDCl3) d 13.9 4±CH3), 22.7, 22.5 4g-CH2),
29.3, 27.8 4a-CH2), 31.6, 31.5 4b-CH2), 109.2 4C-2),
119.9 4C-5), 141.0 4C-3), 141.9 4C-4). MS 4EI) m/z 4%):
276 421) [M1], 274 420) [M1], 234 415) [M1±C3H6], 232
414) [M1±C3H6], 191 450) [M1±C3H6±C3H7], 189 447)
[M1±C3H6±C3H7], 153 410) [M1±C3H6±Br]. Anal. Calcd
for C12H19BrS 4275.3): C, 52.36; H, 6.96; S, 11.65. Found C,
52.22; H, 6.99; S, 11.61.
3.2.6. 5-Bromo-3,300,30000,4,400,40000-hexabutyl-2,20:50,200:500,
2000:5000,20000-quinquethiophene 515). According to GP1,
NBS 40.52 g, 2.9 mmol) in 100 ml DMF, hexabutylquin-
quethiophene 49) 42.02 g, 2.7 mmol) in 100 ml DMF, 1 h,
12 h, chromatographic work-up 4SiO2; petroleum ether/
dichloromethane 15:1, Rfˆ0.52), yield 0.92 g 41.1 mmol,
3.2.2. 2,5-Dibromo-3,4-dibutylthiophene 53). According
to GP1, NBS 413.10 g, 73.5 mmol) in 70 ml DMF, 3,4-di-
butylthiophene 41) 46.0 g, 30.6 mmol) in 55 ml DMF, 1 h,
3 h, distillation, yield 9.9 g 429.7 mmol, 92%) yellow oil, bp
1
135±1368C 41022 mbar). H NMR 4250 MHz, CDCl3) d
0.95 4t, 6 H, ±CH3), 1.42 4m, 8 H, b,g-CH2), 2.45 4m, 4
H, a-CH2). 13C NMR 463 MHz, CDCl3) d 14.1 4±CH3),
22.8 4g-CH2), 28.9 4a-CH2), 31.9 4b-CH2), 108.0 4C-2,5),
141.0 4C-3,4). Anal. Calcd for C12H18Br2S 4354.14): C,
40.70; H, 5.12; S, 9.05. Found C, 40.55; H, 4.93; S, 8.89.
1
42%) yellow oil. H NMR 4500 MHz, CDCl3) d 0.97 4t,
18 H, ±CH3), 1.54 4m, 24 H, b,g-CH2), 2.56 4m, 4 H,
a-CH2), 2.74 4m, 8 H, a-CH2), 6.87 4s, 1 H, H-50000), 7.02
3
3
4d, Jˆ3.8 Hz, 1 H, bH±Th), 7.06 4d, Jˆ3.8 Hz, 1 H,
bH±Th), 7.08 4d, 3Jˆ3.8 Hz, 1 H, bH±Th), 7.09 4d,
3Jˆ3.8 Hz, 1 H, bH±Th). 13C NMR 4126 MHz, CDCl3) d
13.85 4±CH3), 22.68, 22.81, 22.90, 22.98, 23.03 4g-CH2),
28.91, 28.42, 28.22, 27.96, 27.52 4a-CH2), 32.90, 32.69,
31.91, 31.80 4b-CH2), 108.6 4C-5), 119.2 4C-50000), 143.6,
142.6, 140.3, 140.1, 138.9, 138.9, 136.9, 136.4, 135.7,
135.3, 130.9, 130.8, 130.1, 129.6, 126.3, 126.0, 125.9,
3.2.3. 5,500-Dibromo-30,40-dibutyl-2,20:50,200-terthiophene
58). According to GP1, NBS 43.26 g, 18.3 mmol) in 50 ml
DMF, dibutylterthiophene 47) 43.30 g, 9.15 mmol) in 50 ml
DMF, 1 h, 3 h, chromatographic work-up 4SiO2; petroleum
ether/dichloromethane 9:1), yield 4.30 g 48.33 mmol, 91%)
1
yellow solid, mp 38±398C. H NMR 4500 MHz, CDCl3) d

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J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3790
125.9 4C-2,3,4,20,30,40,50,200,300,400,500,2000,3000,4000,5000,20000,30000,
40000). MS 4EI) m/z 4%): 828 4100) [M1], 414 46) [M21].
Anal. Calcd for C44H59BrS5 4828.2): C, 63.81; H, 7.18; S,
19.36. Found C, 63.60; H, 6.99; S, 19.64.
3.3.2. 3,300,30000,4,400,40000-Hexabutyl-2,20:50,200:500,2000:5000,20000-
quinquethiophene 59). According to GP2, bromothiophene
42) 48.06 g, 29.3 mmol) in 15 ml diethyl ether, magnesium
40.71 g, 29.3 mmol) in 15 ml diethyl ether, 4 h; dibromo-
terthiophene 48) 43.80 g, 7.3 mmol), Ni4dppp)Cl2 480 mg,
146 mmol) in 30 ml diethyl ether, 24 h; chromatographic
work-up 4SiO2; n-hexane/dichloromethane 9:1, second
fraction of chromatography), yield 4.17 g 45.5 mmol,
3.2.7. 5,50000-Dibromo-3,300,30000,4,400,40000-hexabutyl-2,20:50,
200:500,2000:5000,20000-quinquethiophene 516). This compound
was isolated as a second fraction from the chromatographic
work-up 4Rfˆ0.68) ofthe corresponding monobromo
derivative 15, yield 0.25 g 40.27 mmol, 10%) orange solid,
mp 70±718C. 1H NMR 4200 MHz, CDCl3) d 0.99 4m, 18 H,
±CH3), 1.52 4m, 24 H, b,g-CH2), 2.56 4t, 4 H, a-CH2), 2.76
4m, 8 H, a-CH2), 7.03 4d, 3Jˆ3.6 Hz, 2 H, bH±Th), 7.09 4d,
3Jˆ3.6 Hz, 2 H, bH±Th). 13C NMR 450 MHz, CDCl3) d
13.85, 13.90 4±CH3), 22.80, 22.91, 23.04 4g-CH2), 27.94,
28.21, 28.37 4a-CH2), 31.79, 32.87, 32.91 4b-CH2), 108.6
4C-5,50000), 125.89, 126.22, 129.71, 130.87, 135.28, 136.14,
138.74, 140.16, 142.55 4C-2,3,4,20,30,40,50,200,300,400,500,
2000,3000,4000,5000,20000,30000,40000). MS 4EI) m/z 4%): 906 4100)
[M1], 826 415) [M1±Br]. Anal. Calcd for C44H58Br2S5
4907.1): C, 58.26; H, 6.45; S, 17.67. Found C, 58.35; H,
6.29; S, 17.76.
1
76%), orange crystals, mp 60±618C. H NMR 4500 MHz,
CDCl3) d 0.95 4m, 18 H, ±CH3), 1.59 4m, 24 H, b,g-CH2),
2.56 4t, 4 H, a-CH2), 2.75 4t, 8 H, a-CH2), 6.89 4s, 2H,
3
3
H-5,500), 7.08 4d, Jˆ3.5 Hz, 2 H, bH±Th), 7.10 4d, Jˆ
3.5 Hz, 2 H, bH±Th). 13C NMR 463 MHz, CDCl3) d
13.87, 14.00 4±CH3), 22.68, 22.98, 23.04 4g-CH2), 27.52,
27.96, 28.90 4a-CH2), 31.88, 32.70, 32.91 4b-CH2), 119.1
4C-5,500), 125.88, 125.90, 129.8, 130.8, 135.8, 136.7, 138.9,
140.1, 143.6 4C-2,3,4,20,30,40,50,200,300,400,500, 2000,3000,4000,5000,
20000,30000,40000). HRMS 4EI) m/z: C44H60S5: 748.32986. Found
748.33029 [M1]. Anal. Calcd for C44H60S5 4749.3): C,
70.53; H, 8.07; S, 21.39. Found C, 70.65; H, 8.22; S, 21.12.
As a side product 0.80 g 42.0 mmol, 7%) 3,30,4,40-tetra-
butyl-2,20-bithiophene was isolated as a yellow oil 4®rst
fraction of chromatography). H NMR 4500 MHz, CDCl3)
1
3.3. General procedure for the nickel-catalyzed cross-
coupling 5`Kumada' coupling) of halogenated
thiophenes and metallated thiophenes 5GP2)
d 0.87 4t, 6 H, ±CH3), 1.01 4t, 6 H, ±CH3), 1.50 4m, 16 H,
b,g-CH2), 2.50 4t, 4 H, a-CH2), 2.59 4t, 4 H, a-CH2), 6.87
4s, 2 H, H-5,500). 13C NMR 463 MHz, CDCl3) d 13.77, 13.98
4±CH3), 22.68, 22.78 4g-CH2), 27.25, 29.00 4a-CH2),
32.66, 31.91 4b-CH2), 120.1 4C-5,500), 129.9 4C-2,20),
141.3, 142.2 4C-3,30,4,40).
A solution ofthe bromothiophene in diethyl ether was added
dropwise to magnesium chips in boiling diethyl ether. The
resulting mixture was heated at re¯ux for several hours,
allowed to cool to room temperature, and transferred by
means ofa syringe to the dropping ufnnel ofa second
apparatus. The Grignard solution was added dropwise to a
solution or suspension ofthe dibrominated thiophene and
1,3-bis4diphenylphosphino)propane nickel4II) chloride in
diethyl ether. The resulting mixture was heated at re¯ux
for several hours, cooled to 08C, acidi®ed with 1N HCl,
and was extracted with dichloromethane. The organic
phase was washed with water and was dried with mag-
nesium sulfate. Evaporation of the solvent and puri®cation
ofthe raw material by chromatography 4phase; eluent) or
recrystallization 4solvent) yielded the desired oligothio-
phene.
3.4. General procedure for the palladium-catalyzed
cross-coupling 5`Sonogashira±Hagihara' coupling) of
halogenated thiophenes and trimethylsilylacetylene
5GP3)
A suspension ofthe halogenothiophene, bis4triphenylphos-
phino) palladium4II) chloride, triphenylphosphine,
copper4I) iodide, pyridine, and triethylamine was purged
with argon for 20 min and subsequently heated to 608C.
Trimethylsilylacetylene was added by means ofa syringe
and the resulting mixture stirred for several hours at 608C,
cooled to 08C, and ®ltered. Evaporation ofthe solvent and
puri®cation ofthe raw material by chromatography 4phase;
eluent) yielded the desired protected ethynylated oligothio-
phene.
3.3.1. 3,300,4,400-Tetrabutyl-2,20:50,200-terthiophene 55).
According to GP2, bromothiophene 42) 432.65 g,
118.7 mmol) in 90 ml diethyl ether, magnesium 42.90 g,
118.7 mmol) in 30 ml diethyl ether, 4 h; 2,5-dibromothio-
phene 44) 413.04 g, 53.9 mmol), Ni4dppp)Cl2 4135 mg,
250 mmol) in 150 ml diethyl ether, 24 h; recrystallization
42-propanol), yield 20.8 g 444.2 mmol, 82%), yellow crys-
3.4.1. 3,4-Dibutyl-2-5trimethylsilylethynyl)thiophene 517).
According to GP3, bromothiophene 42) 44.10 g, 14.9 mmol),
Pd[PPh3]2Cl2 4520 mg, 0.74 mmol), triphenylphosphine
4390 mg, 1.48 mmol), copper4I) iodide 4282 mg, 1.48
mmol), 10 ml pyridine, 10 ml triethylamin, trimethylsilyl-
acetylene 42.92 g, 29.8 mmol), 12 h; chromatographic
work-up 4SiO2; petroleum ether), yield 2.87 g 49.8 mmol,
66%), yellow liquid, bp 103±1048C 41£1022 mbar). 1H
NMR 4200 MHz, CDCl3) d 0.26 4s, 9 H, Si4CH3)3), 0.95
4m, 6 H, ±CH3), 1.49 4m, 8 H, b,g-CH2), 2.50 4t, 2 H,
a-CH2), 2.66 4t, 2 H, a-CH2), 6.80 4s, 1H, H-5). 13C
NMR 450 MHz, CDCl3) d 20.04 4Si4CH3)3), 13.88, 13.93
4±CH3), 22.51, 22.62 4g-CH2), 27.82, 28.65 4a-CH2),
31.90, 31.95 4b-CH2), 98.4 4Th±CxC±), 100.0
4Th±CxC±), 118.4 4C-2); 121.2 4C-5), 141.8 4C-4), 147.9
4C-3). MS 4EI) m/z 4%): 293 423) [M1], 292 4100) [M1], 277
1
tals, mp 49±508C. H NMR 4250 MHz, CDCl3) d 0.98 4m,
12 H, ±CH3), 1.59 4m, 16 H, b,g-CH2), 2.56 4t, 4 H,
a-CH2), 2.75 4t, 4 H, a-CH2), 6.88 4s, 2H, H-5,500), 7.07
4s, 2 H, H-30,40). 13C NMR 463 MHz, CDCl3) d 13.9, 14.0
4±CH3), 22.7, 23.0 4g-CH2), 27.5, 28.9 4a-CH2), 31.8, 32.7
4b-CH2), 119.0 4C-5,500), 125.8 4C-30,40), 130.8 4C-2,200),
136.5 4C-3,300), 138.8 4C-4,400), 143.5 4C-20,50). MS 4EI)
m/z 4%): 474 416) [M1], 473 431) [M1], 472 4100) [M1],
430 413), 429 420) [M1±C3H7]. Anal. Calcd for C28H40S3
4472.8): C, 71.15; H, 8.54; S, 20.31. Found C, 70.91; H,
8.44; S, 20.42.

È È
J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3791
440) [M1±CH3], 250 442) [M1±C3H7], 235 432) [M1±
C3H7±CH3], 207 434) [M1±2C3H7], 177 428) [M1±
2C3H7±2CH3]. Anal. Calcd for C17H28SSi 4292.6): C,
69.79; H, 9.65; S, 10.96. Found C, 69.56; H, 9.55; S, 10.73.
silylacetylene 41.47 g, 15.0 mmol), 18 h; chromatographic
work-up 4SiO2; petroleum ether/dichloromethane 12:1),
yield 3.3 g 43.5 mmol, 70%), orange solid, mp 112±
1138C. 1H NMR 4500 MHz, CDCl3) d 0.27 4s, 18 H,
Si4CH3)3), 0.97 4m, 18 H, ±CH3), 1.52 4m, 24 H, b,g-
CH2), 2.66 4t, 4 H, a-CH2), 2.73 4t, 8 H, a-CH2), 7.07 4d,
3.4.2. 3,300,4,400-Tetrabutyl-5-5trimethylsilylethynyl)-2,20:
50,200-terthiophene 518). According to GP3, bromoterthio-
phene 413) 41.60 g, 2.9 mmol), Pd[PPh3]2Cl2 498 mg,
0.14 mmol), triphenylphosphine 476 mg, 0.29 mmol),
copper4I) iodide 455 mg, 0.29 mmol), 20 ml pyridine,
20 ml triethylamin, trimethylsilylacetylene 4865 mg,
8.8 mmol), 18 h; chromatographic work-up 4SiO2; petrol
ether / dichloromethane 8:1), yield 1.21 g 42.1 mmol,
3
3Jˆ3.9 Hz, 2 H, bH±Th), 7.09 4d, Jˆ3.9 Hz, 2 H, bH±
Th). 13C NMR 463 MHz, CDCl3) d 20.06 4Si4CH3)3), 13.80
4±CH3), 22.79, 22.91, 23.04 4g-CH2), 27.76, 27.97, 28.43
4a-CH2), 32.26, 32.75, 32.89 4b-CH2), 97.8 4Th±CxC±),
101.9 4Th±CxC±), 117.3 4C-5,50000), 126.02, 126.29, 129.80,
131.70, 135.80, 136.20, 138.40, 140.30, 149.6 4C-2±
C-20000,C-3±C-30000,C-4±C-40000,C-50-5000). MS 4EI) m/z 4%):
943 423) [M1], 942 450) [M1], 941 466) [M1], 940 4100)
[M1], 470 412) [M21]. Anal. Calcd for C54H76S5Si2 4941.7):
C, 68.88; H, 8.13; S, 17.02. Found C, 68.92; H, 8.37; S,
16.88.
1
73%), yellow oil. H NMR 4500 MHz, CDCl3) d 0.26 4s,
9 H, Si4CH3)3), 0.96 4t, 12 H, ±CH3), 1.54 4m, 16 H,
b,g-CH2), 2.54 4t, 4 H, a-CH2), 2.68 4m, 4 H, a-CH2),
3
6.87 4s, 1H, H-500), 7.04 4d, Jˆ3.8 Hz, 1 H, H-404or 30)),
7.06 [d, 3Jˆ3.8 Hz, 1 H, H-30 4or 40)]. 13C NMR 4126 MHz,
CDCl3) d 20.05 4Si4CH3)3), 13.85, 13.89, 13.98 4±CH3),
22.67, 22.78, 22.89, 22.96 4g-CH2), 27.51, 27.73, 28.41,
28.89 4a-CH2), 31.89, 32.26, 32.69, 32.76 4b-CH2), 97.8
4Th±CxC±), 101.8 4Th±CxC±), 117.1 4C-5), 119.2
4C-500), 125.9, 126.2, 130.6, 131.8, 135.4, 137.1, 138.3,
139.0, 143.6, 149.5 4C-2,3,4,20,30,40,50,200,300,400). HRMS
4EI) m/z: C33H48S3Si: 568.26875. Found 568.26922 [M1].
Anal. Calcd for C33H48S3Si 4569.0): C, 69.66; H, 8.50; S,
16.90. Found C, 69.68; H, 8.46; S, 17.05.
3.5. General procedure for the copper-promoted
dimerization 5`Hay' coupling) of ethynylated thiophenes
5GP4)
An aqueous solution ofpotassium hydroxide is dropped to
the protected ethynylthiophene dissolved in aqueous tetra-
hydrofuran and methanol. After stirring for 1 h ice is added
to the reaction mixture which subsequently is extracted with
dichloromethane. The organic phase is washed with water
and dried over magnesium sulfate. Under cooling the solu-
tion is concentrated to a small volume. The deprotected
ethynylthiophene is then added to a stirred solution of
copper4I) chloride and TMEDA in dichloromethane, chloro-
form, or acetone. During several hours a stream of oxygen is
purged through the solution which is simultaneously heated
at re¯ux. For work-up ice is added to the reaction mixture,
the organic phase washed with water and dried over mag-
nesium sulfate. Evaporation of the solvent and puri®cation
ofthe raw material by chromatography 4phase; eluent) and
subsequent recrystallization 4solvent) yielded the desired
butadiyne.
3.4.3. 3,300,30000,4,400,40000-Hexabutyl-5-5trimethylsilylethynyl)-
2,20:50,200:500,2000:5000,20000-quinquethiophene 519). Accord-
ing to GP3, bromoquinquethiophene 415) 40.91 g, 1.1
mmol), Pd[PPh3]2Cl2 439 mg, 0.055 mmol), triphenylpho-
sphine 429 mg, 0.11 mmol), copper4I) iodide 421 mg,
0.11 mmol), 5 ml pyridine, 5 ml triethylamin, trimethylsilyl-
acetylene 4324 mg, 3.3 mmol), 18 h; chromatographic
work-up 4SiO2; petroleum ether/dichloromethane 8:1),
yield 0.64 g 40.76 mmol, 69%), orange solid, mp 61±
628C. 1H NMR 4500 MHz, CDCl3) d 0.27 4s, 9 H,
Si4CH3)3), 0.98 4m, 18 H, ±CH3), 1.56 4m, 24 H,
b,g-CH2), 2.56 4t, 2 H, a-CH2), 2.67 4t, 2 H, a-CH2),
2.74 4t, 8 H, a-CH2), 6.88 4s, 2 H, H-5,500), 7.07 4d,
3.5.1. 1,4-Bis53,4-dibutylthien-2-yl)-1,3-butadiyne 520).
According to GP4, potassium hydroxide 4498 mg,
8.9 mmol) in 2 ml water, protected ethynylthiophene 417)
42.37 g, 8.1 mmol) in 10 ml THF, 10 ml methanol; copper4I)
chloride 4198 mg, 2 mmol) and TMEDA 4348 mg, 3 mmol)
in 25 ml dichloromethane, 3 h; chromatographic work-up
4SiO2; petroleum ether/dichloromethane 4:1), recrystalli-
zation 4methanol) yield 1.30 g 45.9 mmol, 73%) bright
yellow crystals, mp 60±618C. 1H NMR 4250 MHz,
CDCl3) d 0.95 4m, 12 H, ±CH3), 1.49 4m, 16 H, b,g-
CH2), 2.49 4t, 4 H, a-CH2), 2.68 4t, 4 H, a-CH2), 6.87 4s,
2 H, H-5). 13C NMR 463 MHz, CDCl3) d 13.90, 13.94
4±CH3), 22.55, 22.58 4g-CH2), 28.09, 28.62 4a-CH2),
31.84, 32.29 4b-CH2), 77.3 4Th±CxC±), 79.7 4Th±CxC±),
117.6 4C-2), 122.9 4C-5), 142.1 4C-3), 149.8 4C-4). MS 4EI)
m/z 4%): 439 429) [M1], 438 4100) [M1], 353 413) [M1±
2C3H7]. Anal. Calcd for C28H38S2 4438.7): C, 76.65; H, 8.73;
S, 14.62. Found C, 76.75; H, 8.97; S, 14.76.
3
3Jˆ3.7 Hz, 1 H, bH±Th), 7.08 4d, Jˆ3.7 Hz, 1 H, bH±
Th), 7.09 4d, 3Jˆ3.7 Hz, 1 H, bH±Th), 7.10 4d, 3Jˆ3.5 Hz,
1 H, bH±Th). 13C NMR 463 MHz, CDCl3) d 20.06
4Si4CH3)3), 13.85, 13.89, 13.97 4±CH3), 22.68, 22.79,
22.91, 22.97, 23.03, 23.04 4g-CH2), 27.53, 27.76, 27.96,
27.99, 28.44, 28.91 4a-CH2), 31.91, 32.26, 32.71, 32.76,
32.91 4b-CH2), 97.9 4Th±CxC±), 101.9 4Th±CxC±),
119.1 4C-5,500), 117.3 4C-5), 119.1 4C-50000), 125.90,
125.96, 125.98, 126.30, 129.61, 130.09, 130.79, 131.72,
135.69, 135.70, 136.34, 136.87, 138.40, 138.93, 140.10,
140.26, 143.6, 149.5 4C-2,3,4,20,30,40,50,200,300, 400,500,2000,
3000,4000,5000,20000,30000,40000). HRMS 4FAB, NBA) m/z:
C49H68S5Si: 844.3694. Found 844.3696 [M1]. Anal. Calcd
for C49H68S5Si 4845.4):C, 69.61; H, 8.11; S, 18.96. Found C,
69.55; H, 8.13; S, 19.07.
3.4.4. 5,50000-Bis5trimethylsilylethynyl)-3,300,30000,4,400,40000-
hexabutyl-2,20:50,200:500,2000:5000,20000-quinquethiophene 526).
According to GP3, diiodoquinquethiophene 425) 45.0 g,
5.0 mmol), Pd[PPh3]2Cl2 4350 mg, 0.5 mmol), triphenyl-
phosphine 4262 mg, 1.0 mmol), copper4I) iodide 4190 mg,
1.0 mmol), 20 ml pyridine, 20 ml triethylamin, trimethyl-
3.5.2. 1,4-Bis53,300,4,400-tetrabutyl-2,20:50,200-terthien-2-yl)-
1,3-butadyine 521). According to GP4, potassium hydrox-
ide 4162 mg, 2.9 mmol) in 2 ml water, protected ethynyl-
terthiophene 418) 41.48 g, 2.6 mmol) in 20 ml THF, 20 ml

È È
J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3792
methanol; copper4I) chloride 4100 mg, 1 mmol) and
TMEDA 4232 mg, 2 mmol) in 35 ml dichloromethane,
5 h; chromatographic work-up 4SiO2; petroleum ether/
dichloromethane 9:1), recrystallization 42-propanol) yield
1.0 g 42.0 mmol, 77%) orange solid, mp 72±738C. 1H
NMR 4250 MHz, CDCl3) d 0.95 4t, 24 H, ±CH3), 1.51 4m,
32 H, b,g-CH2), 2.52 4t, 4 H, a-CH2), 2.68 4m, 12 H,
2.77 4m, 16 H, a-CH2), 6.90 4s, 2 H, aH-Th), 7.13 4s, 4
H, bH±Th). 13C NMR 4126 MHz, CDCl3) d 13.84, 13.88
4±CH3), 22.53, 22.58, 22.70, 22.94, 23.03 4g-CH2), 27.76,
27.97, 28.09, 28.61 4a-CH2), 31.87, 32.27, 32.59, 32.63,
32.83 4b-CH2), 76.9, 78.2, 79.8, 81.3 4Th±CxC±, Th±
CxC±), 116.3, 117.6 4C-2000,500), 123.1 4C-5000), 126.01,
126.53, 129.80, 133.40, 135.40, 136.50, 138.50, 140.30,
142.10, 149.80, 151.40 4C-2,3,20,30,40,50,200,300,400,3000,4000).
HRMS 4FAB, NBA) m/z: C76H96S7: 1232.5557. Found
1232.556 [M1]. Anal. Calcd for C76H96S7 41234.0): C,
73.97; H, 7.84. Found C, C 74.10; H, 7.94.
3
a-CH2), 6.86 4s, 2 H, H-500), 7.05 [d, Jˆ3.7 Hz, 2 H,
3
H-40 4or 30)], 7.10 [d, Jˆ3.7 Hz, 2 H, H-30 4or 40)]. 13C
NMR 463 MHz, CDCl3) d 13.85, 13.91, 14.00 4±CH3),
22.67, 22.72, 22.94, 22.98 4g-CH2), 27.52, 27.75, 28.66,
28.87 4a-CH2), 31.86, 32.63, 32.68 4b-CH2), 77.2 4Th±
CxC±), 81.2 4Th±CxC±), 116.0 4C-5), 119.3 4C-500),
125.9, 126.5, 130.5, 133.6, 135.1, 137.4, 138.5, 139.1,
143.7, 151.6 4C-2,3,4,20,30,40,50,200,300,400). MS 4EI), m/z
4%): 993 422) [M1], 992 447) [M1], 991 463) [M1], 990
4100) [M1]. Anal. Calcd for C60H78S6 4991.6): C, 72.67;
H, 7.93; S, 19.40. Found C, 72.46; H, 7.89; S, 19.12.
3.6. General procedure for the ring closure of
diacetylenes with sul®de anions to thiophenes 5GP5)
Under inert gas, a solution ofthe butadiyne and sodium
sul®de nonahydrate in 2-methoxyethanol is heated at re¯ux
for several hours. After evaporation of the solvent, water
and dichloromethane were added. The organic phase was
washed several times with water and dried over magnesium
sulfate. Evaporation of the solvent and puri®cation of the
raw material by chromatography 4phase; eluent) yielded the
desired oligothiophene.
3.5.3. 1,4-Bis53,300,30000,4,400,40000-hexabutyl-2,20:50,200:500,2000:
5000,20000-quinquethien-5-yl)-1,3-butadyine 522). According
to GP4, potassium hydroxide 435 mg, 0.63 mmol) in 1 ml
water, protected ethynylquinquethiophene 419) 4465 mg,
0.55 mmol) in 15 ml THF, 10 ml methanol; copper4I)
chloride 450 mg, 0.5 mmol) and TMEDA 4232 mg,
2 mmol) in 40 ml dichloromethane, 4 h; chromatographic
work-up 4SiO2; petroleum ether/dichloromethane 9:1)
yield: 276 mg 40.36 mmol, 65%) red solid, mp 85±878C.
1H NMR 4500 MHz, CDCl3) d 0.96 4m, 36 H, ±CH3),
1.57 4m, 48 H, b,g-CH2), 2.56 4t, 4 H, a-CH2), 2.75 4m,
20 H, a-CH2), 6.88 4s, 2H, H-50000), 7.07 4d, 3Jˆ3.7 Hz, 2 H,
bH±Th), 7.10 4d, 3Jˆ3.7 Hz, 2 H, bH±Th), 7.11 4d,
3.6.1. 3,300,4,400-Tetrabutyl-2,20:50,200-terthiophene 55).
According to GP5, thiophene-butadiyne 420) 41.00 g,
2.28 mmol) and sodium sul®de nonahydrate 43.20 g,
13.22 mmol) in 200 ml 2-methoxyethanol, 24 h; chromato-
graphic work-up 4SiO2; n-hexane), yield: 0.68 g 41.44
mmol, 63%). The analytical data ofterthiophene 5 are iden-
tical to the material obtained by Grignard cross-coupling.
3
3Jˆ3.7 Hz, 2 H, bH±Th), 7.13 4d, Jˆ3.5 Hz, 2 H, bH±
3.6.2. 3,300,30000,3000 000,4,400,40000,4000 000-Octabutyl-2,20:50,200:500,
2000:5000,20000:50000,2000 00:5000 00,2000 000-septithiophene 523). Accord-
ing to GP5, terthiophene-butadiyne 421) 4218 mg, 0.22
mmol) and sodium sul®de nonahydrate 4528 mg,
2.2 mmol) in 30 ml 2-methoxyethanol, 12 h; chromato-
graphic work-up 4SiO2; petrol ether/dichloromethane 9:1)
yield: 181 mg 40.18 mmol, 80%) red solid, mp 73±748C.
1H NMR 4500 MHz, CDCl3) d 0.97 4m, 24 H, ±CH3),
1.58 4m, 32 H, b,g-CH2), 2.57 4t, 4 H, a-CH2), 2.78 4m,
Th). 13C NMR 4126 MHz, CDCl3) d 13.84, 13.88, 13.97
4±CH3), 22.67, 22.72, 22.94, 22.97, 23.03 4g-CH2), 27.52,
27.79, 27.96, 28.00, 28.69, 28.91 4a-CH2), 31.91, 32.62,
32.67, 32.69, 32.89 4b-CH2), 77.8 4Th±CxC±), 81.3 4Th±
CxC±), 116.3 4C-5), 119.2 4C-50000), 125.90, 125.99, 126.02,
126.61, 129.50, 130.22, 130.77, 133.6, 135.33, 135.64,
136.74, 136.927, 138.61, 138.94, 140.14, 140.38, 143.6,
151.6 4C-2,3,4,20,30,40,50,200,300,400,500,2000,3000,4000,5000,20000,30000,
40000). HRMS 4FAB, NBA) m/z: C92H118S10: 1542.6441.
Found 1542.638 [M1]. Anal. Calcd for C92H118S10
41544.6): C, 71.54; H, 7.70; S, 20.76. Found C, 71.39; H,
7.80; S, 20.52.
3
12 H, a-CH2), 6.89 4s, 2 H, H-5000 000), 7.09 4d, Jˆ3.7 Hz, 2
3
H, bH±Th), 7.12 4d, Jˆ3.7 Hz, 2 H, bH±Th), 7.13 4d,
3Jˆ3.7 Hz, 2 H, bH±Th). 13C NMR 4126 MHz, CDCl3) d
13.87, 13.90, 13.99 4±CH3), 22.68, 22.98, 23.05 4g-CH2),
27.52, 27.96, 27.99, 28.98 4a-CH2), 31.88, 32.70, 32.90
4b-CH2), 119.1 4C-5,5000 000), 125.89, 125.91, 125.94,
129.75, 129.94, 130.80, 135.71, 135.94, 136.80, 138.90,
140.06, 140.11, 143.60 4C-2±C2000 000, C3±C3000 000, C4±
C4000 000, C-50 ± C5000 00). HRMS 4FAB, NBA) m/z: C60H80S7:
1024.43051. Found 1024.4303 [M1]. Anal. Calcd for
C60H80S7 41025.7): C, 70.28; H, 7.87; S, 21.85. Found C,
70.34; H, 7.85; S, 21.81.
3.5.4. 5,50000-Bis[4-53,4-dibutylthien-2-yl)-buta-1,3-diynyl]-
3,300,30000,4,400,40000-hexabutyl-2,20:50, 200:500,2000:5000,20000-quin-
quethiophene 527). According to GP4, potassium hydrox-
ide 4442 mg, 7.9 mmol) in 2 ml water, protected bisethynyl-
quinquethiophene 426) 41.50 g, 1.6 mmol) and ethynyl-
protected thiophene 417) 41.17 g, 4.0 mmol) in 25 ml THF,
20 ml methanol; copper4I) chloride 4150 mg, 1.5 mmol) and
TMEDA 4696 mg, 6 mmol) in 75 ml dichloromethane, 6 h;
chromatographic work-up 4SiO2; petroleum ether/dichloro-
methane 10:1), yield bisthienyl-butadiyne 420) 450 mg
41.0 mmol, 50%), bright yellow solid, mp 60±618C. Ana-
lytical data are identical to the material obtained by
coupling ofthiophene 4 17). Subsequent preparative HPLC
3.6.3. 3,300,30000,3000 000,30000 0000,30000 0000 00,4,400,40000,4000 000,40000 0000,40000 0000 00
Dodecabutyl-2,20:50,200:500,2000:5000,20000:50000,2000 00:5000 00,2000 000:5000 000
0000 000:50000 000,20000 0000:50000 0000,2000 000 000,5000 000 000,20000 0000 00-undecithiophene
-
,
2
524). According to GP5, quinquethiophene-butadiyne 422)
4120 mg, 0.078 mmol) and sodium sul®de nonahydrate
4186 mg, 0.78 mmol) in 30 ml 2-methoxyethanol and 2 ml
p-xylene, 6 h; chromatographic work-up 4SiO2; petroleum
ether/dichloromethane 9:1), yield: 89 mg 456.7 mmol, 73%)
red solid, mp 83±848C. 1H NMR 4500 MHz, CDCl3) d 0.97
ofthe residue 4SiO ±nitrophenyl; dichloromethane), yield
2
quinquethiophene 427): 375 mg 40.3 mmol, 15%) orange-
red oil. H NMR 4500 MHz, CDCl3) d 1.03 4m, 30 H,
±CH3), 1.54 4m, 40 H, b,g-CH2), 2.55 4t, 4 H, a-CH2),
1

È È
J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3793
4m, 36 H, ±CH3), 1.57 4m, 48 H, b,g-CH2), 2.55 4t, 4 H,
a-CH2), 2.75 4m, 20 H, a-CH2), 6.87 4s, 2H, H-50000 0000 00), 7.06
4d, 3Jˆ3.7 Hz, 2 H, bH±Th), 7.09 4d, 3Jˆ3.7 Hz, 2 H, bH±
Th), 7.11 4m, 3Jˆ3.7 Hz, 6 H, bH±Th). 13C NMR
4126 MHz, CDCl3) d 13.86, 13.97 4±CH3), 22.67, 22.97,
23.04, 23.06 4g-CH2), 27.52, 27.96, 27.99, 28.90 4a-CH2),
31.89, 32.69, 32.89 4b-CH2), 119.1 4C-5,50000 0000 00), 125.87,
125.92, 125.95, 125.98, 129.76, 129.87, 129.90, 129.97,
130.80, 135.72, 135.92, 135.96, 136.01, 136.80, 138.90,
3.6.6. 1,1-Dibrom-2-53,300,4,400-tetrabutyl-2,20:50,200-ter-
thien-5-yl)-ethylene 511). Tetrabromomethane 43.62 g,
10.91 mmol) and triphenylphosphine 45.72 g, 21.82 mmol)
were dissolved in 120 ml dichlormethane. The solution is
cooled to 08C and terthiophene aldehyde 410) 44.28 g,
8.55 mmol) dissolved in 40 ml dichloromethane was slowly
added and the mixture stirred for 2 h at room temperature.
To the reaction mixture n-hexane was added, the resulting
precipitate ®ltered, and the remaining solution evaporated.
The raw product was puri®ed by chromatography 4SiO2,
cyclohexane/dichloromethane 4:1) to yield 4.79 g
140.07, 140.12, 140.15, 143.50 4C-2±C20000 0000 00
, C3±
C30000 0000 00, C4±C40000 0000 00, C-50 ± C5000 000 000). HRMS 4FAB,
NBA) m/z: C92H120S11: 1576.6318. Found 1576.633 [M1].
Anal. Calcd for C92H120S11 41578.6): C, 70.00; H, 7.66; S,
22.34. Found C, 70.27; H, 7.78; S, 22.28.
1
47.27 mmol, 85%) terthiophene 411) as a red oil. H NMR
4250 MHz, CDCl3) d 0.97 4m, 12 H, ±CH3), 1.50 4m, 16 H,
b,g-CH2), 2.56 4m, 4 H, a-CH2), 2.73 4t, 4 H, a-CH2), 6.88
3
4s, 1 H, H-500), 7.05 4d, Jˆ3.7 Hz, 1 H, bH±Th), 7.13 4d,
3.6.4. 3,300,30000,3000 000,30000 0000,4,400,40000,4000 000,40000 0000-Decabutyl-2,20:
50,200:500,2000:5000,20000:50000,2000 00:5000 00,2000 000:50000 000,20000 0000-nonithio-
phene 528). According to GP5, bisbutadiyne 427) 4300 mg,
0.24 mmol) and sodium sul®de nonahydrate 4583 mg,
2.43 mmol) in 30 ml 2-methoxyethanol, 4 h; chromato-
graphic work-up 4SiO2; petrol ether/dichloromethane 8:1),
yield: 220 mg 40.17 mmol, 69%) red solid, mp 77±788C. 1H
NMR 4500 MHz, CDCl3) d 1.02 4m, 30 H, ±CH3), 1.57 4m,
40 H, b,g-CH2), 2.59 4t, 4 H, a-CH2), 2.78 4m, 16 H,
3Jˆ3.7 Hz, 1 H, bH±Th), 7.62 4s, 1 H, Holef). 13C NMR
463 MHz, CDCl3) d 13.86, 13.90, 14.01 4±CH3), 22.67,
22.82, 22.96 4g-CH2), 27.40, 27.47, 28.87 4a-CH2), 31.83,
32.65, 32.87, 33.47 4b-CH2), 86.10 4±CHyCr), 119.2
4C-500), 125.90, 126.28, 129.33, 130.46, 130.63, 132.30,
135.50, 137.26, 138.20, 138.95, 143.61, 144.91 4C-2,3,
4,5,20,30,40,50,200,300,400, ±CHyCr). MS 4EI) m/z 4%):658
463) [M1], 656 4100) [M1], 654 447) [M1], 576 424)
[M1±Br], 574 421) [M1±Br], 496 421) [M1±2Br]. Anal.
Calcd for C30H40Br2S3 4656.6): C, 54.88; H, 6.14; S,
14.65. Found C, 54.73; H, 6.26; S, 14.40.
3
a-CH2), 6.90 4s, 2H, H-50000 0000), 7.10 4d, Jˆ3.7 Hz, 2 H,
bH±Th), 7.14 4d, 3Jˆ3.7 Hz, 2 H, bH±Th), 7.15 4m,
3Jˆ3.7 Hz, 6 H, bH±Th). 13C NMR 4126 MHz, CDCl3) d
13.87, 13.97 4±CH3), 22.67, 22.97, 23.05 4g-CH2), 27.51,
27.98, 28.88 4a-CH2), 31.85, 32.67, 32.88 4b-CH2), 119.1
4C-5,50000 0000), 125.83, 125.88, 125.91, 125.93, 129.73, 129.85,
129.93, 130.79, 135.67, 135.87, 135.95, 136.74, 138.80,
3.6.7. 5-Ethynyl-3,300,4,400-tetrabutyl-2,20:50,200-terthio-
phene 512). To a solution ofterthiophene 4 11) 44.58 g,
6.98 mmol) in 80 ml THF, at 2788C n-butyllithium
49.5 ml 1.6N in n-hexane, 15 mmol) was added, stirred for
2 h at 2788C and 1 h at room temperature. The reaction
mixture was poured onto 150 ml ice water, extracted with
dichloromethane, dried over magnesium sulfate, and evapo-
rated. The crude product was puri®ed by chromatography
4SiO2, cyclohexane) to yield 1.63 g 43.28 mmol, 47%)
ethynylterthiophene 412) as a colourless oil which is only
stable in solution and immediately used for further reac-
tions. 1H NMR 4250 MHz, CDCl3) d 0.95 4m, 12 H,
±CH3), 1.52 4m, 16 H, b,g-CH2), 2.52 4m, 2 H, a-CH2),
2.65 4m, 6 H, a-CH2), 3.49 4s, 1 H, CxCZH), 6.87 4s, 1H,
140.01, 140.06, 140.09, 143.50 4C-2±C20000 0000, C3±C30000 0000
,
C4±C40000 0000, C-50 ± C50000 000). HRMS 4FAB, NBA) m/z:
C76H100S9: 1300.5312. Found 1300.5319 [M1]. Anal.
Calcd for C76H100S9 41302.2): C, 70.10; H, 7.74; S, 22.16.
Found C, 69.96; H, 7.69; S, 22.39.
3.6.5. 3,300,4,400-Tetrabutyl-2,20:50,200-terthiophene-5-carb-
aldehyde 510). To a solution ofterthiophene 4 5) 45.7 g,
12 mmol) and DMF 40.95 g, 13 mmol) in 20 ml 1,2-dichloro-
ethane at 08C freshly distilled phosphorous oxychloride is
slowly added by means ofa syringe and the mixture heated
at 608C for 4 h. After cooling to 08C saturated sodium
hydrogen carbonate solution and dichloromethane were
added. The separated organic phase was washed several
times with saturated sodium hydrogen carbonate solution
and water and dried over magnesium sulfate. Evaporation
ofthe solvent and chromatography 4SiO 2, dichloromethane)
yielded 4.7 g 49.3 mmol, 77%) terthiophene 410) as a red
3
3
H-500), 7.04 4d, Jˆ3.8 Hz, 1 H, bH±Th), 7.06 4d, Jˆ
3.8 Hz, 1 H, bH±Th).
3.6.8. 5,50000-Diiodo-3,300,30000,4,400,40000-hexabutyl-2,20:50,200:500,
2000:5000,20000-quinquethiophene 525). At 08C, iodine 43.47 g,
13.67 mmol) in 150 ml chloroform was slowly added to a
well-stirred suspension ofquinquethiophene 4 9) 45.0 g,
6.67 mmol) and mercury4II) acetate 44.35 g, 13.67 mmol)
in 100 ml chloroform and stirred for 2 h. The reaction
mixture is ®ltered, washed with 1N HCl, aqeuous sodium
thiosulfate solution, dried over magnesium sulfate, and
evaporated. The crude product was puri®ed by chroma-
tography 4SiO2, petroleum ether/dichloromethane 12:1) to
yield 5.78 g 45.8 mmol, 87%) quinquethiophene 425) as a
1
oily solid. H NMR 4250 MHz, CDCl3) d 0.97 4m, 12 H,
±CH3), 1.47 4m, 16 H, b,g-CH2), 2.54 4t, 2 H, a-CH2), 2.73
4t, 4 H, a-CH2), 2.90 4t, 2 H, a-CH2), 6.89 4s, 1H, H-500),
7.08 4d, 3Jˆ4.0 Hz, 1 H, bH±Th), 7.23 4d, 3Jˆ4.0 Hz, 1 H,
bH±Th), 10.01 4s, 1 H, CHO). 13C NMR 463 MHz, CDCl3)
d 13.78, 13.86, 13.95 4±CH3), 22.62, 22.79, 22.92 4g-CH2),
27.03, 27.11, 27.50, 28.81 4a-CH2), 31.80, 32.58, 34.60
4b-CH2), 119.5 4C-500), 126.0, 127.6, 130.2, 134.56,
135.70, 138.85, 139.33, 140.00, 141.2, 143.7, 153.0
4C-2,3,4,5,20,30,40,50,200,300,400), 181.9 4CHO). MS 4EI) m/z
4%):501 436) [M1], 500 4100) [M1], 472 412) [M1±CO],
457 417) [M1±CH3±CO], 415 411) [M1±CO±CH3±C3H6].
Anal. Calcd for C29H40OS3 4500.8): C, 69.55; H, 8.05; S,
19.20. Found C, 69.22; H, 8.37; S, 18.92.
1
yellow solid, mp 51±528C. H NMR 4500 MHz, CDCl3) d
0.97 4m, 18 H, ±CH3), 1.51 4m, 24 H, b,g-CH2), 2.57 4m, 4
H, a-CH2), 2.78 4m, 8 H, a-CH2), 7.03 4d, 3Jˆ3.7 Hz, 2 H,
3
bH±Th), 7.09 4d, Jˆ3.7 Hz, 2 H, bH±Th). 13C NMR
450 MHz, CDCl3) d 13.84, 13.86, 13.91 4±CH3), 22.86,
22.90, 23.03 4g-CH2), 27.96, 28.29, 31.01 4a-CH2), 32.08,
32.88, 32.96 4b-CH2), 74.1 4C-5,50000), 125.90, 126.30,
129.80, 135.49, 135.97, 136.26, 138.60, 140.20, 147.50

È È
J. Kromer, P. Bauerle / Tetrahedron 57 ꢀ2001) 3785±3794
3794
4C-2,3,4,20,30,40,50,200,300,400,500,2000,3000,4000,5000,20000,30000,40000).
MS 4MALDI±TOF) m/z 4%):1003 414) [M1], 1002 436)
[M1], 1001 454) [M1], 1000 4100) [M1]. Anal. Calcd for
C44H58I2S5 41001.1): C, 52.79; H, 5.84; I, 25.35; S 16.01.
Found C, 52.73; H, 5.89; I, 25.13; S, 15.84.
T.; Bidlingmeier, B.; Stabel, A.; Rabe, J. P. Angew. Chem., Int.
Ed. Engl. 1995, 34, 303±307 416-mer). 4f) Sato, M.; Hiroi, M.
Polymer 1996, 37, 1685±1689 415-mer). 4g) Kirschbaum, T.;
È
Briehn, C. A.; Bauerle, P. J. Chem. Soc., Perkin Trans. 1 2000,
1211±1216 412-mer). 4h) Yassar, A.; Delabouglise, D.;
Hmyene, M.; Nessak, B.; Horowitz, G.; Garnier, F. Adv.
Mater. 1992, 4, 490±494 412-mer). 4i) de Leeuw, D. M.
Synth. Met. 1993, 57, 3597±3602 412-mer). 4j) ten Hoeve,
W.; Wynberg, H.; Havinga, E. E.; Meijer, E. W. J. Am.
Chem. Soc. 1991, 113, 5887±5889 411-mer). 4k) Zotti, G.;
Schiavon, G.; Berlin, A.; Pagani, G. Chem. Mater. 1993, 5,
430±436 410-mer).
Acknowledgements
We thank the Fonds der Chemischen Industrie for ®nancial
support. The preparative help ofM. Kunstmann 4University
ofWuÈrzburg) and M. Ammann 4University ofUlm) during
their practical course is gratefully acknowledged.
7. McCullough, R. D. Adv. Mater. 1998, 10, 93±116.
È
1993, 1099±1103.
8. Bauerle, P.; Wurthner, F.; Gotz, G.; Effenberger, F. Synthesis
È
È
9. 4a) Wynberg, H.; Metselaar, J. Synth. Commun. 1984, 14, 1±9.
4b) Roncali, J.; Thobie-Gautier, C. Adv. Mater. 1994, 6, 846±
848.
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