Synthesis of donor-acceptor substituted oligothiophenes by Stille coupling

Article abstract of DOI:10.1016/j.tet.2004.03.022

A synthesis of donor-acceptor-substituted oligothiophenes by Stille coupling is described. The 5′-estanyl derivatives, readily prepared from 5-alkoxy- and 5-amino-2,2′-bithiophenes 7 were coupled with the appropriate aryl or heteroaryl bromides to give th

Full text of DOI:10.1016/j.tet.2004.03.022

Tetrahedron 60 (2004) 4071–4078
Synthesis of donor–acceptor substituted oligothiophenes
by Stille coupling
a
b
M. Manuela M. Raposo,a A. Maurıcio C. Fonseca and G. Kirsch
,
*
´
a
´
Centro de Quımica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
´
b
´ ´ ˆ
Laboratoire d’Ingenierie Moleculaire et Biochimie Pharmacologique, UFR SciFA/Universite de Metz, 1, bd Arago, Metz Technopole,
CP 87811, 57078 Metz Cedex 3, France
Received 13 June 2003; revised 4 November 2003; accepted 2 March 2004
Abstract—A synthesis of donor–acceptor-substituted oligothiophenes by Stille coupling is described. The 50-estanyl derivatives, readily
prepared from 5-alkoxy- and 5-amino-2,20-bithiophenes 7 were coupled with the appropriate aryl or heteroaryl bromides to give the title
compounds.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
As part of our continuing interest in non-linear optical
material32–36 we report here the use of the readily available
5-amino- and 5-alkoxy-2,20-bithiophenes in the Stille cross-
coupling reaction with phenyl, thienyl and bithienyl
bromides to obtain new donor–acceptor substituted
oligothiophenes.
The interest in future photonic devices such as frequency
converters, light modulators and optical switches has led to
the development of a variety of organic non-linear optical
(NLO) chromophores.1–3
In the last few years, thiophene containing donor–acceptor
substituted p systems have been extensively investi-
gated.4–19
The Stille coupling was chosen because it is one of the most
versatile methods for C–C bond formation for several
reasons: (i) the organostannanes are readily prepared,
purified and stored; (ii) the Stille conditions tolerate a
wide variety of functional groups (e.g. CO2R, CN, OH,
CHO, NO2); (iii) the reaction can be performed under mild
conditions and (iv) in contrast to the Suzuki reaction, the
Stille coupling can be run under neutral conditions.37,38
These novel push–pull systems exibit enhanced second-
order polarizabilities b compared to biphenyls or stilbenes.14,16
Donor–acceptor substituted oligothiophenes represent
promising candidates for NLO applications.1–4,13,17,20
The synthesis of donor–acceptor oligothiophenes may be
achieved by several methods such as cross-coupling
reactions; Stille,14–17,21–24 Suzuki,25 or others4,6,8,26–28 and
by procedures involving thiophene ring formations.19,29,30
2. Results and discussion
2.1. Synthesis
Recently we have developed an efficient0 method for the
synthesis of 5-amino- and 5-alkoxy-2,2 -bithiophenes.31
These compounds have proved to be versatile substrates in
formylation, dicyanovinylation and tricyanovinylation reac-
tions, permitting the preparation of several new donor–
acceptor substituted bithiophenes.32
A series of chromophores was synthesized with either
alcoxy- or N,N-dialkylamino- donors and formyl, nitro and
dicyanovinyl acceptors across a conjugated p-bridge
containing a bithiophene-benzene, terthiophene or tetra-
thiophene moiety.
The bithiophenes 9d, 10a–d, 11d, the terthiophenes 12b,
13–15d and the quaterthiophene 16d were synthesized by
Pd(PPh3)4 catalyzed cross coupling reactions of (tributyl-
stannyl)bithiophenes 8a–d with the acceptor-substituted
bromo-aryl or heteroaryl compounds 1a–b,d, 2a–c and 6.
Keywords: 5-Alkoxy- and 5-amino-2,20-bithiophenes; Stille coupling;
Donor–acceptor
oligothiophenes;
UV–visible
spectroscopy;
Chromophores; Solvatochromism; Non-linear optical (NLO) material;
NLO applications.
The aryl, thienyl and the bithienyl bromides used were
activated by electron withdrawing substituents such as
*
Corresponding author. Tel.: þ351-253-604381; fax: þ351-253-678983;
e-mail address: mfox@quimica.uminho.pt
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.03.022

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M. M. M. Raposo et al. / Tetrahedron 60 (2004) 4071–4078
Scheme 1.
formyl, nitro and dicyanovinyl. The bromo derivatives
1-bromo-4-cyanobenzene 1a, 1-bromo-4-nitrobenzene 1b,
4-bromo-1-formylbenzene 1c, 5-bromo-2-formylthiophene
2a and 5-bromo-2-nitrothiophene 2b were commercially
available. The synthesis of the other bromo derivatives was
achieved by several methods. Knoevenagel condensation39
of the commercial available 4-bromo-1-formylbenzene 1c
and 5-bromo-2-formylthiophene 2a with malononitrile in
refluxing ethanol gave the corresponding dicyanovinyl
derivatives 4-bromo-1-dicyanovinylbenzene 1d and
5-bromo-2-dicyanovinylthiophene 2c in 87 and 91% yield,
respectively.
50-Bromo-5-dicyanovinyl-2,20-bithiophene 6 was obtained
from 5-dicyanovinyl-2,20-bithiophene 5 by bromination
with NBS in a solution of chloroform–acetic acid (1:1) in
85% yield. Compound 5 was obtained in 55% yield, by
Stille coupling of (tributhylstannyl)thiophene 440 under
Pd(PPh3)4 catalysis at 80 8C in toluene. Compound 4 was
synthesized from the commercially available 2-bromothio-
phene 3 in quantitative yield, by lithiation, using n-BuLi at
0 8C, followed by transmetalation with tributyltin chloride
at 278 8C (Scheme 1).
The bromo derivatives 1d, 2c and 6 described earlier were
Scheme 2.

M. M. M. Raposo et al. / Tetrahedron 60 (2004) 4071–4078
4073
synthesized in order to be coupled under Stille conditions
with the stannane bithiophenes 8a–d.
13d (Table 1, entry 8) to 545.5 nm in piperidino-T3-
[CHvC(CN)2] 15d (Table 1, entry 10). The influence of
the strength of the donor group is demonstrated by
comparison of the absorption maxima of compounds 10a
and 10c as the longest wavelength transition is shifted
from 413.0 nm in methoxy-T2-4-NO2-Ph 10a (Table 1,
entry 2) to 474.5 nm in N,N-diethyl-T2-4-NO2-Ph 10c
(Table 1, entry 4).
The synthesis of bithienylstannanes 8a–d was achieved b0y
metalation of 5-alkoxy- and 5-N,N-dialkylamino-2,2 -
bithiophenes 7a–d, using n-BuLi at 0 8C followed by
transmetalation with tributyltin chloride at 278 8C (Scheme
2). The organotin compounds 8a–d were obtained in good
yields (81–90%) and were used in the Stille coupling
reactions without further purification.
In general, the stronger the donor and/or acceptor group, the
smaller the energy difference between ground and excited
states, and the longer the wavelength of absorption.14
According to Zyss1 the increase of the b values charac-
teristic of the NLO effects is accompanied by an increase of
the lmax in the UV–vis spectra.
The Stille reactions were performed in toluene under an
argon atmosphere and Pd(PPh3)4 (2 mol%) was used as
palladium catalyst at 80 8C for 8–33.5 h (Scheme 2).
The donor–acceptor oligothiophenes were obtained in
moderate to good yields 42–65% (Table 1). Better yields
were obtained when more activated aryl or thienyl bromides
were used in the Stille couplings. Therefore, bithiophene
10a was synthesized in 65% yield (Table 1, entry 2) and
terthiophene 15d was obtained in 55% yield (Table 1, entry
10).
Comparison of the electronic absorption spectra of piperi-
dino-T2-4-NO2-Ph 10d (Table 1, entry 5) (lmax¼453.0 nm)
with piperidino-T3-NO2 14d (Table 1, entry 9) (lmax¼504.0
nm) reveals that the replacement of a benzene ring with a
thiophene ring causes a dramatic red shift of the charge-
transfer band. This observation clearly indicates that the
incorporation of thiophene moieties in push–pull com-
pounds enhances their charge-transfer properties.4,8,13,20
The influence of the activation of the aryl or heteroaryl
bromides on the yield of the Stille coupling is demonstrated
by comparison of the yield of 9d (43%) (Table 1, entry 1)
with the yield of 11d (56%) (Table 1, entry 6). A better yield
was obtained for compound 11d due to the activation of the
bromide 1d by the dicyanovinyl group.
2.3. Solvatochromic behavior of oligothiophenes
Solvatochromism is easily quantified by UV–vis spectro-
scopy and is particularly suitable for the empirical
determination of the polarity of a solvent42,43 on a
molecular-microscopic level. To evaluate the intermolecu-
lar forces between the solvents and the solute molecules
we have measured absorption spectra of six oligothiophenes
in 14 solvents of different solvatation character.
Waite41 et al. reported the study of the polarizability and
hyperpolarizability of terthiophene 12b but no analytical
data was described for this compound.
2.2. UV–visible study of oligothiophenes
The maxima of the wavenumbers nmax for compounds 10d,
11d, 12b, 13d, 15d and 16d, as well as the corresponding
wavelength l are listed in Table 2 and compared with the pp
determined by Kamlet and Taft.
Electronic absorption spectra of all the push–pull com-
pounds 9–16 show an intense lowest energy charge-transfer
absorption band in the UV–vis region. The position of
this band is strongly influenced by the structure of the
compounds, for example by the type of p bridge and the
substitution pattern in the donor and acceptor moieties19
(Table 1).
The highest energy transitions are found with non-polar
solvents such as hexane and cyclohexane. More polar
solvents such as DMF resulted in lower energy transitions.
This behavior has been defined as a positive solvatochromic
response (between Dn¼1333 cm21 for 16d and Dn¼
3758 cm21 for 11d) that is related to a greater stabilization
of the excited state relative to the ground state with
increasing polarity of the solvent.
The influence of the strength of the acceptor group is
demonstrated by comparison of the absorption maxima of
compounds 13d and 15d as the longest wavelength
transition is shifted from 456.0 nm in piperidino-T3-CHO
Table 1. Yields and UV–vis absorption spectra of the coupled donor–acceptor oligothiophenes 9–16
Entry
Bromide
Bithienyl stannane
Product
Yield (%)
Reaction time [h]
lmaxa [nm] (1)
1
2
3
4
5
6
7
8
1a
1b
1b
1b
1b
1d
2a
2a
2b
2c
6
8d
8a
8b
8c
8d
8d
8b
8d
8d
8d
8d
Piperidino-T2-4-CN-Ph 9d
43
65
42
44
53
56
46
51
53
55
45
19
10.5
19
24.5
8
30
20
17
33
420.0 (18,660)
413.0 (25,750)
461.0 (10,050)
474.5 (16,800)
453.0 (10,000)
468.0 (21,400)
465.5 (22,690)
456.0 (15,260)
504.0 (10,100)
545.5 (23,770)
510.5 (12,000)
Methoxy-T2-4-NO2-Ph 10a
N,N-Dimethyl-T2-4-NO2-Ph 10b
N,N-Diethyl-T2-4-NO2-Ph 10c
Piperidino-T2-4-NO2-Ph 10d
Piperidino-T2-4-[CHvC(CN)2]-Ph 11d
N,N-Dimethyl-T3-CHO 12b
Piperidino-T3-CHO 13d
Piperidino-T3-NO2 14d
Piperidino-T3-[CHvC(CN)2] 15d
Piperidino-T4-[CHvC(CN)2] 16d
9
10
11
33.5
30
a
All the UV/vis spectra were run in ethanol.

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M. M. M. Raposo et al. / Tetrahedron 60 (2004) 4071–4078
Table 3. Correlation of UV–vis absorption maxima of bithiophenes 10d,
11d, terthiophenes 12b, 13d, 15d and quaterthiophene 16d and solvent
parameter ppa
Compounds
n0 [cm21
]
Regression analysis sb [cm21
]
rb
10d
11d
12d
13d
15d
16dc
22,588
22,376
22,415
22,730
18,698
20,019
21120
23297
21294
21252
21003
21002
20.8084
20.8495
20.9410
20.9037
20.8869
20.9150
l
l
l
l
l
l
a
Applied solvents (pp value): n-hexane (20.08), cyclohexane (0.00),
diethyl ether (0.27), dioxane (0.55), ethyl acetate (0.55), tetrahydrofuran
(0.58), acetone (0.71), acetonitrile (0.75), dimethylformamide (0.88),
ethanol (0.54), methanol (0.60), chloroform (0.76), dichloromethane
(0.82), toluene (0.54).
Intercept, slope, and correlation coefficient r of the linear solvatation
energy relationship.
Without n-hexane and cyclohexane.
b
c
Because of the pronounced solvatochromism, the good
correlation with pp values for the 14 solvents investigated
(r¼0.8495) and the long wavelength absorption in the
visible range, 11d seemed to be a very appropriate solvent
polarity indicating dye (Table 3). The change in dipole
moment on electronic excitation was shown to be oriented
parallel to the transition dipole and is moreover constant
over the whole charge transfer band.
The great number of aliphatic and dipolar aprotic solvents
was chosen to determine the correlation behavior of nmax
(11d) and pp because specific interactions were not
expected. In fact a good correlation between absorption
Figure 1. Correlation between absorption wavenumbers nmax (11d) and the
pp scale according to Kamlet and Taft. Aliphatic and dipolar aprotic
solvents (V), protic solvents (A), chlorinated solvents (K) and aromatic
solvents (W).

M. M. M. Raposo et al. / Tetrahedron 60 (2004) 4071–4078
4075
1
wavenumbers of 11d and pp values (r¼0.9431) of the
2224 (CN) cm21. H NMR (CDCl3) d 7.70 (d, 2H, J¼
8.4 Hz, 2£Ar-H), 7.73 (s, 1H, CH¼C(CN)2), 7.78 (d, 2H,
J¼8.4 Hz, 2£Ar-H). Anal. calcd for C10H5BrN2: C, 51.52;
H; 2.15; N, 12.02. Found C, 51.34; H, 2.46; N, 11.84%.
corresponding solvents was obtained (Table 2).
However, as shown in Figure 1, the alcohols, aromatic and
chlorinated solvents slightly deviate from this regression
line. The behavior in chlorinated and aromatic solvents,
which display the lowest energy transitions is noteworthy.
Similar behavior has been observed for donor–acceptor
molecules of oligothiophenes where the trend was ration-
alized as a consequence of an intramolecular charge
transfer.14
3.2.2. 5-Bromo-2-dicyanovinylthiophene 2c. Pale orange
solid (91%). Mp: 157–158 8C. (ether/n-hexane). UV (aceto-
nitrile): lmax nm (1, /M21 cm21) 317.5, (17,000). IR (nujol)
n 3310, 2224 (CN) cm21. 1H NMR (CDCl3) d 7.25 (d, 1H,
J¼4.0 Hz, 4-H), 7.51 (d, 1H, J¼4.0 Hz, 3-H), 7.75 (s, 1H,
CH¼C(CN)2). MS (EI) m/z (%): 240 (Mþ81Br, 98), 238
(Mþ79Br, 100), 189 (10), 187 (10), 159 (51). HRMS: m/z
(EI) for C8H381BrN2S; calcd 239.9180; found: 239.9180.
Anal. calcd for C8H3BrN2S: C, 40.17; H; 1.26; N, 11.72; S,
13.39. Found C, 40.23; H, 1.49; N, 11.44%).
The oligothiophene derivatives 9–16 were completely
1
characterized by HRMS, H spectroscopy and by IR and
UV–vis spectroscopy.
The study of the thermal stability, the electrochemical and
the non-linear optical properties of the new oligothiophenes
are under way.
3.3. Synthesis of 50-bromo-5-dicyanovinyl-2,20-bithio-
phene 6
3.3.1. Synthesis of 2-(tri-n-butylstannyl)thiophene 4.40
Under argon a solution of n-BuLi in hexanes (2.5 ml,
6.14 mmol, 2.5 M) was dropped into a stirred solution of 3
(3.07 mmol) in dry ether at 0 8C. After 1 h the mixture was
cooled to 278 8C and a solution of tributyltin chloride
(1 g/0.83 ml, 3.07 mmol) in dry ether was slowly added and
the mixture was stirred overnight. The mixture was then
added to water (50 ml). The aqueous layer was extracted
with ether (3£30 ml). The combined organic layers were
dried with magnesium sulfate, and the solvent was removed
in vacuo to give the title product 4 as a pale brown oil in
quantitative yield. 1H NMR (CDCl3) d 0.80–1.00 (m, 15H,
3£(CH2)2CH2CH3)), 1.10–1.50 (m, 12H, 3£(CH2)2CH2-
CH3), 7.20 (dd, 1H, J¼3.3, 1.0 Hz, 3-H), 7.25–7.29 (m,
1H, 4-H), 7.66 (dd, 1H, J¼4.7, 1.0 Hz, 5-H). Product 4 was
used in the Stille coupling without further purification.
3. Experimental
3.1. General
1H NMR spectra were obtained on a Varian Unity Plus
Spectrometer at 300 MHz using the solvent peak as internal
reference. The solvents are indicated in parenthesis before
the chemical shift values (d relative to TMS). Mp were
determined on a Gallenkamp apparatus and are uncorrected.
Infrared spectra were recorded on a Perkin–Elmer 1600
FTIR spectrophotometer. UV–vis spectra were recorded
with a Shimadzu UV/2501/PC spectrophotometer using
several solvents analytically pure (Merck). EI mass spectra
EI (70 eV) and HRMS were run on a Unicam GC–MS 120.
Elemental analysis was carried out on a Leco CHNS-932.
Column chromatography was performed on Merck silica gel
60 (Art 9385). Light petroleum refers to solvent boiling in
the range 40–60 8C.
3.3.2. Synthesis of 5-dicyanovinyl-2,20-bithiophene 5. A
degassed solution of the 5-bromo-2-dicyanovinylthiophene
2c (0.66 g, 2.8 mmol), the thienylstananne 4 (3.07 mmol)
and Pd(PPh3)4 (0.056 mmol) in toluene (5 ml) was heated at
80 8C under argon. After 24 h the reaction mixture was
cooled to room temperature, filtered and washed with a col0d
mixture of ether/petrol to give the pure 5-dicyanovinyl-2,2 -
bithiophene 5 as a pale orange solid. The organic solution
obtained from the filtration was washed with a saturated
solution of KF (3£50 ml), water (3£50 ml) and a saturated
solution of NaCl (100 ml). The resulting organic layer were
dried with magnesium sulfate, and the solvent was removed
in vacuo to give a brown oil. Overall yield: 55%. Recrystalli-
zation from n-hexane gave the pure 5-dicyanovinyl-2,200-
bithiophene 5 as a pale orange solid. Mp: 166.5–168.5 8C.
All reactions were carried out under an argon atmosphere in
dry glassware.
The phenyl and thienyl bromides 1a–c, 2a–b and 3 were
purchased from Aldrich and used as received.
The synthesis of bithiophenes 7a–d has been described
elsewhere.31
3.2. General procedure for the synthesis of dicyanovinyl
derivatives 1d and 2c from the corresponding formyl
compounds 1c and 2a by Knoevenagel condensation
1
IR (nujol) n 2218 (CN) cm21. H NMR (CDCl3) d 7.18–
7.22 (m, 1H, 40-H), 7.62 (d, 1H, J¼4.5 Hz, 3-H), 7.67 (dd,
10H, J¼3.8, 1.0 Hz, 30-H), 7.78 (dd, 1H, J¼5.0, 1.0 Hz,
5 -H), 7.89 (d, 1H, J¼4.5 Hz, 3-H), 8.64 (s, 1H, CH¼C(CN)2).
To a solution of malononitrile (1.2 g, 18 mmol) and the
formyl derivatives 1c and 2a (15 mmol) in ethanol (50 ml)
was added piperidine (1 drop). The solution was heated at
reflux for 1 h, then cooled and the solvent was removed
under reduced pressure to give the crude dicyanovinyl
compounds. The resulting solids were recrystallized to give
the title compounds 1d and 2c.
3.3.3. Synthesis of 50-bromo-5-dicyanovinyl-2,20-bithio-
phene 6. To a stirred solution of 5-dicyanovinyl-2,20-
bithiophene 5 (0.1 g, 0.41 mmol) in a 1:1 (v/v) solution of
chloroform–acetic acid (12 ml) was added NBS (0.073 g,
0.41 mmol) at rt. After 24 h the reaction mixture was
washed with water (30 ml). The organic layer was dried
with magnesium sulfate, and the solvent was removed in
3.2.1. 4-Bromo-1-dicyanovinylbenzene 1d. Beige solid
(87%). Mp: 160.5–161.6 8C. (ether/n-hexane). IR (nujol) n

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M. M. M. Raposo et al. / Tetrahedron 60 (2004) 4071–4078
vacuo to give the pure bithiophene 6 as a orange brownish
solid (85%). Recrystallization from n-hexane gave the title
compound as a pale orange solid. Mp: 193–195 8C. UV
(acetonitrile): lmax nm (1, /M21 cm21) 421.0 (21,290),
bithienyl 6 bromides (0.5 mmol), and bithienylstanannes
8a–d (0.55 mmol) in toluene (5 ml) was added Pd(PPh3)4
(0.01 mmol). The mixture was heated at 80 8C under argon.
After the given reactions times (TLC control, Table 1) the
reaction mixture was cooled to room temperature and then
filtered and washed with cold toluene to give the pure
oligothiophenes 9d, 10a–d, 11d, 12b and 13d–16d. The
isolated solids were recrystallized. The organic solution
obtained from the filtration was washed with a saturated
solution of KF (3£30 ml), water (3£30 ml) and a saturated
solution of NaCl (50 ml). The resulting organic layers were
dried with magnesium sulfate, and the solvent was removed
308.0 (240). IR (nujol) n 2222 (CN) cm21 1H NMR
.
(DMSO) d 7.35 (d, 1H, J¼4.2 Hz, 30-H), 7.53 (d, 1H,
J¼4.2 Hz, 40-H), 7.61 (d, 1H, J¼4.5 Hz, 3-H), 7.88 (d, 1H,
J¼4.5 Hz, 4-H), 8.65 (s, 1H, CHvC(CN)2). MS (EI) m/z
(%): 322 (Mþ81Br, 99), 320 (Mþ79Br, 100). HRMS: m/z
(EI) for C12H581BrN2S2; calcd 321.9057; found: 321.9058.
3.4. General procedure for the synthesis of 2-alkoxy- and
2-amino-substituted 5-(tri-n-butylstannyl)-2,20-bithio-
phenes 8a–d
1
in vacuo to give oils which by NMR reveal to be the
stannanes derivatives used in excess.
Under Ar a solution of n-BuLi in hexanes (1.3 ml,
3.21 mmol, 2.5 M) was dropped into a stirred solution of
7 (2.7 mmol) in dry ether at 0 8C. After 1 h the mixture was
cooled to 278 8C and a solution of tri-n-butylchlorostan-
nane (2.7 mmol) in dry ether was slowly added and the
mixture was stirred overnight. The mixture was then added
to water (50 ml). The aqueous layer was extracted with ether
(3£30 ml). The combined organic layers were dried with
magnesium sulfate, and the solvent was removed in vacuo to
give product 8. Derivatives 8a–d were used in the Stille
couplings without further purification.
3.5.1. 50-(400-Cyanophenyl)-5-piperidino-2,20-bithiophene
9d. Orange solid (43%). Mp: 227–229 8C (ether). UV
(EtOH): lmax nm (1, /M21 cm21) 420.0 (18,660), 297.0
(7450), 255.0 s (8430), 239.0 (11,130), 215.0 s (13,340). IR
1
(nujol) n 2219 (CN) cm21. H NMR (CDCl3) d 1.50–1.80
(m, 6H, 3£CH2), 3.10–3.20 (m, 4H, 2£NCH2), 6.00 (d, 1H,
J¼3.9 Hz, 4-H), 6.92–6.98 (m, 2H, 3 and 30-H), 7.30 (d, 1H,
J¼4.2 Hz, 40-H), 7.63 (br s, 4H, 4£Ar-H). MS (EI) m/z (%):
350 (Mþ, 100). HRMS: m/z (EI) for C20H18N2S2; calcd
350.0911; found: 350.0916.
3.5.2. 5-Methoxy-50-(400-nitrophenyl)-2,20-bithiophene
10a. Orange solid (65%). Mp: 169–171 8C (ether). UV
(EtOH): lmax nm (1, /M21 cm21) 413.0 (25,750), 289.0
(8680), 252.0 (1450), 213.0 s (1810). IR (nujol) n 1593,
1531, 1505, 1351, 1200, 1158, 1111, 1048, 846, 800, 772,
3.4.1. 5-Methoxy-50-(tri-n-butylstannyl)-2,20-bithiophene
1
8a. Green oil (85%). H NMR (CDCl3) d 0.80–1.00 (m,
15H, 3£(CH2)2CH2CH3), 1.20–1.40 (m, 12H, 3£(CH2)2-
CH2CH3)), 3.90 (s, 3H, OCH3), 5.80 (d, 1H, J¼3.9 Hz,
4-H), 6.87 (d, 1H, J¼3.9 Hz, 3-H), 7.00 (d, 1H, J¼3.6 Hz,
30-H), 7.07 (d, 1H, J¼3.6 Hz, 40-H).
749, 721, 666 cm21 1H NMR (CDCl3) d 3.94 (s, 3H,
.
OCH3), 6.18 (d, 1H, J¼3.9 Hz, 4-H), 6.91 (d, 1H, J¼3.9 Hz,
3-H), 7.03 (d, 1H, J¼3.9 Hz, 30-H), 7.3700(d, 1H, J¼3.9 Hz,
40-H), 7.70 (d, 2H, 00J¼9.0 Hz, 200 and 6 -H), 8.23 (d, 2H,
J¼9.0 Hz, 300 and 5 -H). MS (EI) m/z (%): 317 (Mþ, 44).
Anal. calcd for C15H11NO3S2: C, 56.76; H, 3.47; N, 4.41; S,
20.20. Found: C, 56.51; H, 3.52; N, 4.44; S, 19.80. HRMS:
m/z (EI) for C15H11NO3S2; calcd 317.0180; found:
317.0174.
3.4.2. 5-N,N-Dimethylamino-50-(tri-n-butylstannyl)-2,20-
1
bithiophene 8b. Orange oil (90%). H NMR (CDCl3) d
0.80–1.00 (m, 15H, 3£(CH2)2CH2CH3), 1.10–1.45 (m,
12H, 3£(CH2)2CH2CH3), 2.93 (6H, s, N(CH3)2), 5.80 (d,
1H, J¼3.7 Hz, 40-H), 6.87 (d, 1H, J¼3.7 Hz, 3-H), 7.00 (d,
1H, J¼3.5 Hz, 4 -H) 7.07 (d, 1H, J¼3.5 Hz, 30-H).
3.4.3. 5-N,N-Diethylamino-50-(tri-n-butylstannyl)-2,20-
bithiophene 8c. Pale brown oil (90%). H NMR (CDCl3)
3.5.3. 5-N,N-Dimethyl-50-(400-nitrophenyl)-2,20-bithio-
phene 10b. Orange solid (42%). Mp: 243–245 8C (ethanol).
UV (EtOH): lmax nm (1, /M21 cm21) 461.0 (10,050), 322.0
(4650), 264.0 (5140), 211.0 s (8540). IR (nujol) n 1592,
1563, 1534, 1504, 1450, 1425, 1331, 1278, 110, 1056, 919,
1
d 0.80–1.00 (m, 15H, 3£(CH2)2CH2CH3), 1.10–1.45 (m,
12H, 3£(CH2)2CH2CH3), 1.20–1.30 (overlapped t, 6H,
2£CH2CH3), 3.25–3.35 (q, 4H, J¼6.0 Hz, 2£CH2CH3),
5.78 (d, 1H, J¼3.9 Hz, 4-H), 6.86 (d, 1H, J¼3.9 Hz,
3-H), 7.00 (d, 1H, J¼3.6 Hz, 40-H) 7.05 (d, 1H, J¼3.6 Hz,
30-H).
1
848, 795, 748, 688, 666 cm21. H NMR (CDCl3) d 2.98
(s, 6H, 2£CH3), 5.81 (d, 1H, J¼3.9 Hz, 4-H), 6.94 (d, 1H,
J¼3.9 Hz, 30-H), 6.96 (d, 1H, J¼3.9 Hz, 300-0 H), 7.35 (d, 1H,
J¼3.9 Hz, 4 -H), 7.65 (d, 2H, J¼8.9 Hz, 2 and 600-H), 8.20
(d, 2H, J¼8.9 Hz, 300 and 500-H). MS (EI) m/z (%): 330 (Mþ,
100). HRMS: m/z (EI) for C16H14N2O2S2; calcd 330.0497;
found: 330.0505.
3.4.4. 5-Piperidino-50-(tri-n-butylstannyl)-2,20-bithio-
phene 8d. Pale brown oil (81%). 1H NMR (CDCl3) d
0.80–1.00 (m, 15H, 3£(CH2)2CH2CH3), 1.20–1.40 (m,
12H, 3£(CH2)2CH2CH3), 1.50–1.80 (m, 6H, 3£CH2),
3.10–3.20 (m, 4H, 2£NCH2), 5.98 (d, 1H, J¼3.9 Hz, 4-H),
6.86 (d, 1H, J¼3.9 Hz, 30-H), 7.00 (d, 1H, J¼3.6 Hz, 40-H)
7.08 (d, 1H, J¼3.6 Hz, 3 -H).
3.5.4. 5-N,N-Diethyl-50-(400-nitrophenyl)-2,20-bithiophene
10c. Dark red solid (44%). Mp: 181–183 8C (ethanol). UV
(EtOH): lmax nm (1, /M21 cm21) 474.5 (16,800), 360.0
(9630), 265.0 (7140). IR (nujol) n 1591, 1504, 1332, 1280,
1183, 1108, 1057, 847, 791, 750, 722, 666 cm21. 1H NMR
(CDCl3) d 1.24 (t, 6H, J¼7.0 Hz, 2£CH2CH3), 3.34 (q, 4H,
J¼7.0 Hz, 2£CH2CH3), 5.79 (d, 1H, J¼3.9 Hz, 4-H), 6.92
(d, 1H, J¼3.9 Hz, 3-H), 6.98 (d, 1H, J¼3.9 Hz, 30-H)0,0 7.35
(d, 1H, J¼3.9 Hz, 40-H), 7.66 (d, 2H, J¼9.0 Hz, 2 and
3.5. General procedure for palladium-catalyzed cross-
couplings of aryl 1a–b, 1d and heteroaryl bromides
2a–c and 6 with stannylbithiophene derivatives 8a–d
To a degassed solution of aryl 1a–b and 1d, thienyl 2a–c or

M. M. M. Raposo et al. / Tetrahedron 60 (2004) 4071–4078
4077
600-H), 8.21 (d, 2H, J¼9.0 Hz, 300 and 500-H). MS (EI) m/z
(%): 358 (Mþ, 100). HRMS: m/z (EI) for C18H18N2O2S2;
calcd 358.0810; found: 358.0810.
(EI) m/z (%): 376 (Mþ, 100). HRMS: m/z (EI) for
C17H16N2O2S3; calcd 376.0374; found: 376.0363.
3.5.10. 500-Dicyanovinyl-5-piperidino-2,20:50,200-terthio-
phene 15d. Dark purple solid (55%). Mp: 185–187 8C.
UV (EtOH): lmax nm (1, /M21 cm21) (Ethanol) 545.5
(23,770), 377.0 (10,992). IR (nujol) n 2218 (CN) cm21. 1H
NMR (DMSO-d6) 1.50–1.70 (m, 6H, 3£CH2), 3.10–3.20
(m, 4H, 2£NCH2), 6.13 (d, 1H, J¼4.2 Hz, 4-H), 7.09 (d, 1H,
J¼3.9 Hz, 40 or 30-H), 7.17 (d, 1H, J¼4.2 Hz, 3-H), 7.505 (d,
1H, J¼4.2 Hz, 300-H), 7.59 (d, 1H, J¼3.9 Hz, 30 or 4 -H),
7.86 (d, 1H, J¼4.2 Hz, 400-H), 8.57 (s, 1H, CHvC(CN)2).
MS (EI) m/z (%): 407 (Mþ, 100). HRMS: m/z (EI) for
C21H17N3S3; calcd 407.0585; found: 407.0594.
3.5.5. 5-Piperidino-50-(400-nitrophenyl)-2,20-bithiophene
10d. Brown solid (53%). Mp: 238–240 8C (ethanol). UV
(EtOH): lmax nm (1, /M21 cm21) 453.0 (10,000), 322.0
(4720), 316.0 (4710), 266.0 (4700), 213.0 s (8611). IR
(nujol) n 1592, 1504, 1493, 1329, 1275, 1247, 1117, 1066,
1
843, 796, 686, 666 cm21. H NMR (CDCl3) d 1.50–1.80
(m, 6H, 3£CH2), 3.16–3.20 (m, 4H, 2£NCH2), 5.99 (d, 1H,
J¼3.9 Hz, 4-H), 6.95–6.98 (m, 2H, 3 and 30-H), 7.35 (d, 1H,
J¼3.9 Hz, 40-H), 7.66 (d, 2H, J¼8.9 Hz, 200 and 600-H), 8.21
(d, 2H, J¼8.9 Hz, 300 and 500-H). MS (EI) m/z (%): 370 (Mþ,
100). HRMS: m/z (EI) for C19H18N2O2S2; calcd 370.0810;
found: 370.0814.
3.5.11. 5000-Dicyanovinyl-5-piperidino-2,20:50,200:500,2000-
tetrathiophene 16d. Dark blue solid (45%). Mp:
.230.0 8C (with decomposition). lmax nm (1, /M21 cm21
)
3.5.6. 50-(400-Dicyanovinylphenyl)-5-piperidino-2,20-bi-
thiophene 11d. Green solid with metal luster (56%). Mp:
232–233 8C. UV (ethanol): lmax nm (1, /M21 cm21) 468.0
(21,400), 360.5 (13,386). IR (nujol) n 2223 (CN). cm21. 1H
NMR (DMSO-d6) d 1.45–1.70 (m, 6H, 3£CH2), 3.10–3.20
(m, 4H, 2£NCH2), 6.11 (d, 1H, J¼4.5 Hz, 4-H), 7.08–7.14
(m, 2H, 3 and 300-0H), 7.69 (d, 1H, J¼3.9 Hz, 40-H), 7.90 (d,
2H, J¼8.4 Hz, 2 and 600-H), 7.96 (d, 2H, J¼8.4 Hz, 300 and
500-H), 8.44 (s, 1H, CHvC(CN)2). MS (EI) m/z (%): 401
(Mþ, 100). HRMS: m/z (EI) for C23H19N3S2; calcd
401.1020; found: 401.1022.
(Ethanol) 510.5 (12,000). IR (nujol) n 2218 (CN) cm21. 1H
NMR (DMSO-d6) 1.42–1.70 (m, 6H, 3£CH2), 3.10–3.20
(m, 4H, 2£NCH2), 6.10 (d, 1H, J¼4.2 Hz, 4-H), 7.05 (d, 1H,
J¼4.2 Hz, 40 or0 30-H)0, 7.16 (d, 010 H, J¼4.2 Hz, 3-H), 7.34–
7.38 (m, 2H, 3 or 4 -H and 3 -H or 400-H0)0, 7.64 (d, 1H,
J¼4.2 Hz, 3000-H), 7.67 (d, 1H, J¼4.2 Hz, 4 or 300-H), 7.89
(d, 1H, J¼4.2 Hz, 4000-H), 8.62 (s, 1H, CHvC(CN)2). MS
(EI) m/z (%): 489 (Mþ, 100). HRMS: m/z (EI) for
C25H19N3S4; calcd 489.0462; found: 489.0465.
3.5.7. 500-Formyl-5-N,N-dimethyl-2,20:50200-terthiophene
12b. Brown solid (46%). Mp: 186–188 8C (ethanol) [lit.41
Acknowledgements
(mp not quoted)]. UV (EtOH): lmax nm (1, /M21 cm21
465.5 (22,690), 342.0 (9300), 258.0 (12,010), 213.0 s
)
Thanks are due to Foundation for Science and Technology
(Portugal) for financial support through IBQF (UM) and
through FEDER, POCTI (Ref. POCTI/QUI/37816/2001).
1
(14,100). IR (nujol) n 1650 (CHO) cm21. H NMR d 2.98
(s, 6H, 2£CH3), 5.80 (d, 1H, J¼4.4 Hz, 4-H), 6.87 (d, 1H,
J¼4.4 Hz, 40 or 30-H), 6.96 (d, 1H, J¼3.9 Hz, 3-H), 7.107 (d,
1H, J¼4.4 Hz, 300-H), 7.22 (d, 1H, J¼4.4 Hz, 30 or 4 -H),
7.65 (d, 1H, J¼4.4 Hz, 400-H), 9.84 (s, 1H, CHO). MS (EI)
m/z (%): 319 (Mþ, 100). HRMS: m/z (EI) for C15H13NOS3;
calcd 319.0159; found: 319.0156.
References and notes
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1
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