Synthesis of conjugated 2 and 2,5-(ethenyl) and (ethynyl)phenylethynyl thiophenes: Fluorescence properties

Article abstract of DOI:10.1016/j.tet.2006.01.032

Nano conjugated thienylethenyl and thienylethynyl compounds with controlled structure and dimensions have been efficiently prepared, by heterocoupling reaction between 1,4-(thienylethynyl)phenylacetylene (or thienylethenyl) phenylacetylene and 2- or 2,5-dihalothiophene. Conjugated 1,4-di(2- thienylethynylphenyl)- (or 2-thienylethenylphenyl)-1,3-butadiyne were obtained by the homocoupling of the terminal acetylenes in excellent yield. The end-capped (N,N-dimethylaminophenyl)- and [3,5-di(trimethylsilylethynyl)-1- ethynyl]-2,5-di(phenylethynyl)_nthiophene were obtained by the heterocoupling between the corresponding terminal acetylene and 2,5-di(iodo)thiophene, catalyzed by the bis(triphenylphosphine)palladium and cuprous iodide system in excellent yield.

Full text of DOI:10.1016/j.tet.2006.01.032

Tetrahedron 62 (2006) 3112–3122
Synthesis of conjugated 2 and 2,5-(ethenyl) and
(ethynyl)phenylethynyl thiophenes: fluorescence properties
*
J. Gonzalo Rodriguez, Jorge Esquivias, Antonio Lafuente and Laura Rubio
´
´
´
Dpto. Quımica Organica, Universidad Autonoma, Cantoblanco, 28049 Madrid, Spain
Received 21 November 2005; revised 20 December 2005; accepted 10 January 2006
Available online 13 February 2006
Abstract—Nano conjugated thienylethenyl and thienylethynyl compounds with controlled structure and dimensions have been
efficiently prepared, by heterocoupling reaction between 1,4-(thienylethynyl)phenylacetylene (or thienylethenyl)phenylacetylene and
2- or 2,5-dihalothiophene. Conjugated 1,4-di(2-thienylethynylphenyl)- (or 2-thienylethenylphenyl)-1,3-butadiyne were obtained by the
homocoupling of the terminal acetylenes in excellent yield. The end-capped (N,N-dimethylaminophenyl)- and [3,5-di(trimethylsilylethynyl)-
1-ethynyl]-2,5-di(phenylethynyl)nthiophene were obtained by the heterocoupling between the corresponding terminal acetylene and
2,5-di(iodo)thiophene, catalyzed by the bis(triphenylphosphine)palladium and cuprous iodide system in excellent yield.
q 2006 Elsevier Ltd. All rights reserved.
1. Introduction
the preparation of conjugated substituted oligo- and
polythiophenes,12 which exhibit an electronic conductivity
that was dependent on the resonance along the polymeric
chain.10 Thiophene dendrimers with p-extended conjugated
chains, shown that the p–p* conduction band decreases
from the periphery to the heart, increasing the fluorescence
quantum yield.13 The conjugated thiophene chains show
interesting solvatochromic properties.14
Nanometer-sized molecules of precise length showing p
extended conjugation, exhibit in general high thermal
stability and can present electroconductive, magnetic and
optical properties.1 Several potential applications such as
artificial photosynthesis,2 photocatalysis,3 molecular photo-
voltaic cells,4 molecular informatics,5 and optoelectronic
devices6,7 are beginning to emerge from this new field
of research.
Recently, we have developed p-extended conjugated
structures with important optical properties.15 Now, we
report the synthesis of conjugated end-capped (N,N-
dimethylaminophenyl)- and [3,5-di(trimethylsilylethynyl)-
1-ethynyl]-2,5-di(phenylethynyl) molecules containing the
thiophene ring. Moreover, the conjugation effect through
the double or triple bond linking the thiophene ring and the
conjugated chains are also considered.
Earlier studies on the heteroaromatic systems containing
the thiophene ring shows three significant details: (i) an
increasing of the first molecular hyperpolarizability (b)8
(ii) the substitution of the thiophene ring by an aryl one,
changes the donor versus the acceptor effect, (iii) the
electronic nature of the heteroaromatic ring affects the
donor or acceptor strength through the inductive effects.9
9
2. Results and discussion
Therefore, polythiophene has been obtained as a conjugated
polymer with many interesting optical and electronic
properties such as electrochromism and near-metallic
conductivity.10 Oligomers of thiophene are also technologi-
cally important materials and have been used in prototype
organic thin-film transistors.11 Interest in materials with
these properties has directed substantial efforts towards
The synthesis of (E,E)-1,4-di(20-thienyl)-1,3-butadiene,
(E,E)-216 and 1,4-di(2-thienyl)-1,3-butadiyne (4),17 was
carried out to compare the polarity-polarizability produced
by the double or triple bond of the thiophene conjugated
systems.
Thus, compound0(E,E)-2 was obtained by the homocoupling
reaction of 2-(2 -chlorovinyl)thiophene (1), catalyzed by
the zerovalent nickel(triphenylphosphine)n complexes. The
mixture (Z/E)-2-chlorovinylthiophene (1),18 (Z/E, 43:57),
was obtained by the Wittig reaction between furfural and
Keywords: Arylethynylthiophenes; p-Extended conjugation; Eglinton–
Glaser reaction; Cadiot–Chodkiewicz reaction; Sonogashira reaction;
Fluorescence.
*
Corresponding author. Tel.: C34 914974715; fax: C34 914973966;
e-mail: gonzalo.rodriguez@uam.es
0040–4020/$ - see front matter q 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.01.032

J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
3113
H
O
H
i.
ii.
S
S
S
Cl
S
(E/Z)-1
(E,E)-2
i. Cl2CH2PPh3, tBuOK
ii. NiCl2(PPh3)2, Zn, THF, rt, 2 h
iii. tBuOK, THF; iv. CuCl/O2, pyridine
iii.
S
iv.
H
S
S
3
4
Scheme 1.
the (chloromethyl)(triphenyl)phosphonium ylide, in good
yield. The homocoupling reaction of the (Z/E)-1 mixture
was catalyzed by the zerovalent nickel complexes, prepared
in situ by reaction of dichloro bis[(triphenyl)phosphine]-
nickel and powdered zinc in tetrahydrofuran giving (E,E)-
1,4-di(2-thienyl)-1,3-butadiene 2 as the unique isomer in
good yield (62%), Scheme 1.
reaction between furfural and p-(iodobenzyl)(triphenyl)-
phosphonium ylide, giving the (Z/E)-5 mixture (50:50).20
The complete isomerization of (Z/E)-5 to (E)-5 was carried
out by sunlight exposure in presence of iodine crystals,
Scheme 2.
Now, the heterocoupling of (E)-5 with 2-methyl-3-butyn-2-
ol in presence of dichloro bis[(triphenyl)phosphine]palla-
dium and cuprous iodide catalyst system, in diethylamine at
room temperature, gives the propargyl compound (E)-6,
which by treatment with powdered sodium hydroxide in dry
toluene at reflux temperature gives the terminal acetylene
(E)-7 in good yield.
Moreover, the (Z/E)-1 mixture was treated with potassium
tert-butoxide, at room temperature, giving 2-ethynylthio-
phene (3) in good yield (77%).19 The oxidative dimerization
of the terminal acetylene 3 was catalyzed by cuprous
chloride in pyridine, under oxygen atmosphere, affording
1,4-di(thienyl)-1,3-butadiyne (4), in excellent yield (91%),
Scheme 1.
The 2-(p-iodophenylethynyl)thiophene (8) was prepared
from (E)-5 by bromine addition and successive elimination
with potassium tert-butoxide in quantitave yield. The
heterocoupling reaction between 8 and 2-methyl-3-butyn-
2-ol, in presence of the palladium–copper catalyst, affords
the propargyl intermediate 9 in good yield (85%), which
was treated with powdered sodium hydroxide in dry toluene,
giving the terminal acetylene 10.
2.1. Synthesis of the terminal acetylenes
The previous synthesis of terminal acetylenes are necessary
for the construction of the p extended conjugated thienyl-
(p-ethynylphenyl) structures. Thus, the conjugated units of
2-(E)-phenylethenyl- and phenylethynyl- for the thiophene
structures were prepared by heterocoupling between 2-
[p-(iodophenyl)-20-ethenyl]thiophene (E)-5 and the ethynyl
analogue 8. Compound (E)-5 was prepared by the Wittig
Thus, the heterocoupling between the acetylene 11 and
4-(hydroxyl-3-methyl-1-butyn)-1-iodobenzene gives an
CH3
v.
i.
I
S
I
ii.
S
iii.
iv.
I
8
(E)-5
(E/Z)-5
vii.
vi.
vi.
S
S
(E)-5
OH
H
(E)-6
(E)-7
vii.
8
OH
H
S
S
9
10
i. NBS/CCl4; ii. PPh3;iii. tBuOK, Furfural, toluene; iv. EtOH, sunlight, I2; v. Br2, CCl4, tBuOK;
vi. PdCl2(PPh3)2, CuI, 2-methyl-3-butyn-2-ol, HNEt2, at rt;vii. NaOH, toluene, at reflux.
Scheme 2.

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J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
Me
Me
Me
Me
Me
i.
ii.
N
H
N
I
N
OH
Me
11
I
OH
Me
Me
11
N
N
OH
iii.
ii.
Me
Me
H
12
i. 2-Methyl-3-butyn-2-ol, CuI, PdCl2(PPh3)2, NEt3; ii. NaOH, toluene at reflux; iii. CuI, PdCl2(PPh3)2, NEt3.
Scheme 3.
intermediate propargyl derivative, which by treatment with
sodium hydroxide in dry toluene at the reflux temperature
yields compound 12, as a red solid, in excellent yield (90%),
Scheme 3.
conditions fails. The 1,3-butadiyne (E,E)-14 was obtained
by the Cadiot–Chodkiewicz reaction. Thus, through the
oxidative bromination of compound (E)-7, which was
carried out in situ with potassium hypobromide giving
(E)-13 in good yield, which in presence of cuprous chloride
gives (E,E)-14 in moderate yield, Scheme 4.
2.2. Oxidative dimerization of the terminal acetylenes
In contrast, the 1,3-butadiyne derivative 15 was obtained by
oxidative homocoupling reaction of the terminal acetylene
10, catalyzed by cuprous chloride in pyridine, at room
temperature, under oxygen atmosphere, Scheme 5. The
different reactive behavior of (E)-7, seems to be due to
To extend the conjugation of the terminal acetylenes (E)-7
and 10 were transformed by catalytic oxidative dimerization
in (E,E)-14 and 15, respectively. Thus, the oxidative
homocoupling of (E)-7 was carried out in presence of
cuprous chloride and under the Glaser (or Eglinton)
S
i.
S
H
S
(E,E)-14
(E)-7
ii.
iii.
S
Br
(E)-13
.
i. CuCl, O2, pyridine; ii. KOBr, H2O/THF; iii. (E)-6, Et2NH, NH2OH HCl, CuCl, MeOH.
Scheme 4.
i.
S
H
S
S
10
15
iv.
S
8 + 10
S
16
i. CuCl, O2, pyridine;ii. PdCl2(PPh3)2, CuI, 2-methyl-3-butyn-2-ol.
Scheme 5.

J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
3115
S
n
n
Me2N
NMe2
n = 0, 17 (98%)
i.
Me2N
H
n
n = 1, 19 (85%)
+
n = 0, 11
n = 1, 12
Me2N
NMe2
n
n = 0, 18 (2%)
n = 1, 20 (2%)
i. 2,5-Diiodothiophene, CuI, PdCl2(PPh3)2, NEt3.
Scheme 6.
the double bond coordination to the cuprous salt catalyst,
avoiding the intermediate cuprous acetylide formation.21
Similarly, 2,5-[di(p-N,N-dimethylamino)(phenylethynyl)
(phenylethynyl)]thiophene (19) was obtained in good
yield (85%) by the heterocoupling reaction between 2,5-
di(iodo)thiophene and the terminal acetylene 12, catalyzed
with the palladium–copper system. In this reaction was also
detected the oxidative dimerization product 20 in very low
yield (2%), Scheme 6.
The 1,3-diyne 15 was analyzed by mass spectrometry
(MALDI-TOF technique) using a laser radiation at 337 nm,
with complete volatilization of the sample. During the laser
irradiation the topo-oligomerization products were detected
in the mass spectrum,22 in the following ratio: dimer (21%);
trimer (4%); tetramer (1%) and pentamer (in traces).
On the other hand, compounds 17 and 19 exhibit the
conjugated chains on 2,5 positions of the thiophene ring
forming a high-angle structure. High-angle structures contain-
ing the end-capped thiophene ring were also synthesized.
The conjugated structural homologue 16 was synthesized as
a conjugated reference to compare their optical properties
with the 1,3-diyne structure 15. Compound 16 was obtained
by the heterocoupling reaction between 8 and the terminal
acetylene 10, catalyzed by the palladium–copper system, in
good yield (78%), Scheme 5.
Thus, the heterocoupling reaction between 2,5-di(iodo)thio-
phene and the thienylethenyl terminal acetylene (E)-7 (or
the thienylethynyl terminal acetylene 10) affords the
conjugated high-angle structure 21 as a yellow solid in a
65% yield (or 22, 85%), Scheme 7.
2.3. Synthesis of the conjugated arylethynyl-2,5-thio-
phene structures
Finally the synthesis of high-angle 2,5-(ethynylphenyl)thio-
phenes, with trigonal-linear 3,5-di(trimethylsilylethynyl)-1-
phenylethynyl structure, was carried out by the hetero-
coupling reaction between 2,5-di(iodo)thiophene and the
terminal acetylenes 23 (nZ1), 24 (nZ2) or 25 (nZ3),
previously prepared,14b catalyzed by the palladium–copper
system, giving the conjugated compounds 26 (97%), 27
(95%) and 28 (95%), respectively, Scheme 8.
The heterocoupling reaction between 2,5-di(iodo)thiophene
and the terminal acetylene 11, in presence of the palladium–
copper catalyst, provides 2,5-[di(p-N,N-dimethylamino)-
phenylethynyl]thiophene (17) (98%) and the 1,3-butadiyne
derivative 18 (2%). Compound 18 seems to be formed by
the oxidative dimerization of the terminal acetylene,
resulting from the Eglinton–Glaser behavior of the catalyst.
At this point, it is remarkable the high reactivity of 2,5-
di(iodo)thiophene compared with 2,5-dibromothiophene,
that gives only the 1,3-butadiyne derivative (18).
The oxidation potential of compounds 26–28 was deter-
mined by cyclic voltammetry resulting of 1.04, 1.08 and
i.
S
H
S
S
21
(E)-7
S
i.
S
H
S
S
S
10
22
i. 2,5-Diiodothiophene, PdCl2(PPh3)2, NEt3, CuI.
Scheme 7.

3116
J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
Me3Si
Me3Si
SiMe3
S
i.
H
n
n
n
Me3Si
n = 0, 26
n = 0, 23
n = 1, 24
n = 2, 25
Me3Si
SiMe3
n = 1, 27
n = 2, 28
i. 2,5-Diiodothiophene, PdCl2(PPh3)2, CuI, NEt3.
Scheme 8.
Figure 1. Computed analysis of compound 17.
1.08 V, respectively, as irreversible oxidizable peaks.
Hence, no dependence of the oxidative potential on the
chain conjugation must be expected.
(E,E)-1,4-di(thienyl)-1,3-diene (E,E)-2, exhibits a fluor-
escent radiation with very low quantum yield, while 1,4-
di(thienyl)-1,3-diyne (4) does not show appreciable fluor-
escence emission radiation in dichloromethane, Table 1.
Compounds 17, 19, 21, 22 and 26–28 exhibit the referred
high-angle geometry for the linear chain on 2,5- positions of
the thiophene ring. The internal angle for compound 17
reaches a value of 153.78, calculated by theoretical
computational methods23 (Fig. 1), which agrees well with
the data obtained by X-ray diffraction analysis.24
The terminal N,N-dimethylamino compounds, such as the
ethynyl conjugated 1,3-diyne 15 shows an unique fluor-
escence emission band at 421 nm while that their ethenyl
conjugated 1,3-diyne analogue 14, shows two emission
bands at 427 and 454 nm (Table 1). Similarly, the terminal
N,N-dimethylamino triyne conjugated 16 also exhibits two
fluorescence emission bands at 390 and 410 nm with
practically, the same quantum yield while their 1,3-diyne
15 shows only an emission band at 421 nm with higher
quantum yield, Table 1.
2.4. Fluorescent properties
The UV–vis absorption and fluorescent emission radiation
of the terminal acetylenes, 1,3-butadiynes and conjugated
arylethynyl-2,5-thiophene structures were analyzed.
The terminal N,N-dimethylamino 2,5-thiophene conjugated
structures (compounds 17 and 19) show fluorescent
emission radiation with important quantum yields
(Table 2). There is a significant increase of the radiation
quantum yield with the conjugation by the number of
All the 1,3-butadiynes and terminal acetylenes show
fluorescence emission radiation in solution of dichloro-
methane. In a general analysis, it is noticeable that
Table 1. UV–vis absorption and fluorescence emission radiation for
compounds 2, 4, 7, 10, and 14–16 in CH2Cl2 at room temperature
Table 2. UV–vis absorption and fluorescence emission radiation for the
compounds 17, 19, and 21–22 in CH2Cl2 at room temperature
Compound
UV–vis
lmax (nm)
3 (MK1 cmK1
)
Fluorescence
lmax (nm)
Ffa
Compound
UV–vis
lmax (nm)
3 (MK1 cmK1
)
Fluorescence
lmax (nm)
Ff
2
4
7
10
14
15
16
381
364
341
337
382
359
352
25,100
26,300
28,400
30,000
78,300
81,250
57,100
431
—
420, 450
392, 410
427, 454
421
0.02
—
17
19
21
22
385
393
367
379
57,500
104,320
21,850
44,000
456
512
440, 462
398, 423
0.23a
0.30b
0.10a
0.34a
0.13
0.14
0.29
0.36
0.30
a Fluorescence quantum yield was determined relative to 2-aminopyridine
in 0.1 N H SO4.
390, 410
2
b Fluorescence quantum yield was determined relative to quinine sulphate
in 1 N H SO4.
a Fluorescence quantum yield was determined relatively to 2-aminopyri-
dine in 0.1 N H SO4.
2
2

J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
3117
17
19
1.0
0.8
0.6
0.4
0.2
0.0
21
1.0
0.8
0.6
0.4
0.2
0.0
22
400
450
500
550
l/nm
600
650
350
400
450
l/nm
500
550
Figure 2. Normalized fluorescence emission spectra for compounds 17, 19 and 21–22 in dichloromethane at room temperature.
26 27 28
23 24
25
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
300
350
400
l/nm
450
500
350
400
450
500
550
l/nm
Figure 3. Normalized fluorescence emission spectra for compounds 23–25 and 26–28 in CH2Cl2 at room temperature.
the ethynylphenyl units in the chain, as it was observed in
compounds 17 and 19, Table 2.
and 28 show a significant increasing in the fluorescence
quantum yield with the number of the ethynylphenyl units in
the conjugated chain, Table 3.
However, an important increasing of the fluorescence
emission quantum yield was observed in compound 22
triple bond linked to the thiophene ring versus compound 21
with the conjugated double bond connecting with the
thiophene ring. Compounds 21 and 22 show two fluor-
escence wavelength emission bands, while the end-capped
1,4-(N,N-dimethylaminophenyl) chains show an unique
emission band (compounds 17 and 19), Figure 2.
Table 3. UV–vis absorption and fluorescence emission radiation for
compounds 23–28 in CH2Cl2 at room temperature
Compound
UV–vis
lmax (nm)
3 (MK1 cmK1
)
Fluorescence
lmax (nm)
Ffa
23
24
25
26
27
28
344
346
345
355
379
377
55,100
75,000
99,100
46,900
78,900
113,000
350, 373
373, 395
406, 428
391, 410
421, 447
429, 454
0.10
0.28
0.60
0.20a
0.42a
0.54a
Recently, we report the fluorescence emission of the
terminal acetylenes 23–25 connected with different linear
linkers such as benzene, 1,5-naphthalene and 1,3-diyne.14d
In all the cases was observed a similar bathochromic shift
close-up 20 nm by each ethynylphenyl unit increasing the
conjugate chain. Nevertheless, the high-angle structure of
the 2,5-tiophene in compounds 26–28 produces an irregular
bathochromic shift for each ethynylphenyl unit in the
conjugated chain, Figure 3. However, compounds 26, 27
a Fluorescence quantum yield was determined relative to 2-aminopyridine
in 0.1 N H SO4.
2
3. Conclusions
New nano conjugated thienylethenyl and thienylethynyl
derivatives can be synthesized through the Sonogashira

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J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
reaction between 2- or 2,5-dihalothiophene and 1,4-
(thienylethynyl)phenylacetylene (or (thienylethenyl)phenyl-
acetylene) in good yield. Conjugated 1,4-di(2-thienyl-
ethynylphenyl)- (or 2-thienylethenylphenyl)-1,3-butadiynes
can be obtained by the homocoupling of the terminal
acetylenes in excellent yield.
187 mg (62%), was isolated as a yellow solid, mp 140–
143 8C. UV–vis (CH2Cl2), lmax (nm): 381, 362, 268.
Fluorescence (CH2Cl2), lmax (nm): 431 (fZ0.021). FT-IR
1
(KBr, cmK1): 1653, 1541, 1457, 978. H NMR (300 MHz,
CDCl3): d 7.17 (d, 2H, JZ4.4 Hz); 7.02 (d, 2H, JZ6.9 Hz);
6.99 (dd, 2H, JZ6.9, 4.4 Hz); 6.72 (d, 2H, JZ17.0 Hz);
6.73 (dd, 2H, JZ17.0, 8.5 Hz). 13C NMR (75 MHz,
CDCl3): d 143.0, 128.6, 127.6, 125.9, 125.5, 124.4. MS
(70 eV): 218 (MC, 100), 184 (36), 173 (9), 134 (17), 121
(8), 109 (7), 97 (16).
The conjugated 1,3-butadiyne derivatives can be efficiently
prepared by the catalytic Eglinton–Glaser or Cadiot–
Chodkiewicz reactions.
4.1.2. (E)-1-(p-Iodophenyl)-2-(20-thienyl)ethene (E)-5.
To a solution of p-(iodobenzyl)(triphenyl)phosphonium
bromide (560 mg, 1.0 mmol) in toluene (25 ml), under
dryness and argon atmosphere and at 0 8C, was added
potassium tert-butoxide (112 mg, 1.0 mmol). The mixture
was stirred for 30 min and then, was slowly added a solution
of 2-thiophenecarboxaldehyde (112 mg, 0.1 ml, 1.0 mmol)
in anhydrous toluene (5 ml). The mixture was stirred at
room temperature overnight. After evaporation of solvent,
the residual solid was extracted with dichloromethane and a
little amount of water. The organic layer was dried on
anhydrous magnesium sulphate, filtered off and solvent
removed, to give a (Z/E) isomers mixture (50:50).
The end-capped (N,N-dimethylaminophenyl)- and [3,5-
di(trimethylsilylethynyl)-1-ethynyl]-2,5-di(phenylethynyl)n-
thiophene were obtained in good yield by the heterocoupling
between the appropriate terminal acetylene and 2,5-
di(iodo)thiophene, catalyzed by the bis(triphenylphosphine)-
palladium and cuprous iodide system in diethylamine.
All the new conjugated 2- or 2,5- thiophene derivatives
show fluorescent radiation emission which, for the
conjugation by triple bond linking ethynylphenyl module
exhibit highest quantum yields than the double one
(29–54%).
4. Experimental
A solution of the (Z/E) mixture in ethanol was completely
transformed to the E-isomer by sunlight exposure for 72 h,
giving (E)-1-(p-iodophenyl)-2-(20-thienyl)ethene (E)-5, as a
yellow solid, mp 155–157 8C, 129 mg (41%). UV–vis
(CH2Cl2), lmax (nm): 335, 284. FT-IR (KBr, cmK1): 3075,
1525, 1487, 1429, 960, 815. 1H NMR (300 MHz, CDCl3): d
7.63 (d, 1H, JZ5.0 Hz); 7.60 (d, 2H, JZ8.4 Hz); 7.23
(d, 1H, JZ16.1 Hz); 7.19 (d, 2H, JZ8.4 Hz); 7.06 (d, 1H,
JZ3.4 Hz); 7.00 (dd, 1H, JZ5.0, 3.4 Hz); 6.83 (d, 1H, JZ
16.1 Hz). 13C NMR (75 MHz, CDCl3): d 142.4, 137.7,
136.5, 127.7, 127.3, 127.0, 126.5, 124.8, 122.5, 92.6.
C12H9IS (311.95): Anal. Calcd C 46.17, H 2.91; found: C
45.96, H 3.12.
4.1. General procedures
Melting points were determined in open capillaries and are
uncorrected. FT-IR spectra were recorded using KBr pellets
or NaCl plates and only partial data is reported. Proton
nuclear magnetic resonance (1H NMR) spectra were
recorded at 300 MHz. Chemical shifts are reported in
delta (d) units, parts per million (ppm) downfield from
trimethylsilane. Coupling constants are reported in Hertz
(Hz). Carbon-13 nuclear magnetic resonance (13C NMR)
spectra were recorded at 75 MHz. Chemical shifts are
reported in delta (d) units, parts per million (ppm) relative to
the center of the triplet at 77.00 ppm for deuteriochloro-
form. Mass spectra were obtained at an ionizing potential of
70 eV and reported as m/e (relative intensity). Accurate
masses are reported for the molecular ion (MC1) or a
suitable fragment ion. Flash chromatography was performed
on silica gel 60 (200–400 mesh) using the indicated
solvents. The UV–vis spectra frequencies are given in nm
4.1.3. 1-(Bromo-p-iodophenyl)-2-(bromo-20-thienyl)-
ethane. To a solution of (E)-1-(p-iodophenyl)-2-(20-thieny-
l)ethene (E)-5 (850 mg, 2.72 mmol) in tetrachloromethane
(30 ml), at 0 8C was added slowly bromine (435.2 mg,
2.72 mmol) in tetrachloromethane (60 ml), and the mixture
was vigorously stirred for 6 h. The solvent0was removed to
give 1-(bromo-p-iodophenyl)-2-(bromo-2 -thienyl)ethane,
as a white solid, 1.29 g (100%). 1H NMR (300 MHz,
CDCl3): d 7.74 (d, 2H, JZ8.1 Hz); 7.41 (d, 1H, JZ4.8 Hz);
7.23 (d, 1H JZ4.3 Hz); 7.22 (d, 2H, JZ8.1 Hz); 7.00 (dd,
1H, JZ4.8, 4.3 Hz); 5.75 (d, 1H, JZ11.2 Hz); 5.30 (d, 1H,
JZ11.2 Hz).
and 3 in L molK1 cmK1
.
4.1.1. (E,E)-1,4-Di(20-thienyl)-1,3-butadiene16 (2) To a
solution of dichlorobistriphenylphosphine nickel (915 mg,
1.4 mmol) in dry tetrahydrofuran (10 ml), under argon
atmosphere was added tetrabutylammonium iodide
(518 mg, 1.4 mmol) and zinc powder (136 mg, 2 mmol)
and the mixture was stirred until the solution takes a dark
red color. After 30 min with stirring was added a solution of
1-chloro-2-(20-thienyl)ethene (1) (200 mg, 1.4 mmol) in dry
tetrahydrofuran (10 ml) and the mixture was stirred over-
night at room temperature. Finally, was added dichloro-
methane and filtered to remove the catalyst. The organic
layer was dried on anhydrous magnesium sulphate, filtered
off and the solvent removed. The residual solid was purified
by silica gel column chromatography using hexane as
the eluent. The (E,E)-1,4-di(20-thienyl)-1,3-butadiene (2),
4.1.4. 1-(p-Iodophenyl)-2-(20-thienyl)ethylene (E)-8. To
a solution of 1-(bromo-p-iodophenyl)-2-(bromo-20-thieny-
l)ethane (1.29 g, 2.72 mmol) in anhydrous tetrahydrofuran
(60 ml), and potassium tert-butoxide (919.4 mg,
8.20 mmol). The mixture was stirred at room temperature
for 2 h and then0, the solvent was removed to give 1-(p-
iodophenyl)-2-(2 -thienyl)ethene (8) as a white solid, mp
89–91 8C, 828 mg (98%). UV–vis (CH2Cl2), lmax (nm):
330, 310, 266. FT-IR (KBr, cmK1): 3421, 1518, 1481, 819.
1H NMR (300 MHz, CDCl3): d 7.68 (d, 2H, JZ8.4 Hz);
7.30 (d, 1H, JZ5.2 Hz); 7.28 (d, 1H, JZ3.4 Hz); 7.23 (d,

J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
3119
2H, JZ8.4 Hz); 7.02 (dd, 1H, JZ5.2, 3.4 Hz). 13C NMR
(75 MHz, CDCl3): d 137.5, 132.8, 132.2, 127.6, 127.2,
122.9, 122.5, 94.3, 92.1, 84.1. C12H7IS (309.93): Anal.
Calcd C 46.47, H 2.27; found: C 46.31, H 2.55.
7.27 (d, 1H, JZ3.4 Hz); 7.01 (dd, 1H, JZ5.2, 3.4 Hz); 1.61
(s, 6H).
4.1.8. 1-(20-Thienyl)-2-(p-ethynylphenyl)ethyne25 (10)
Following the general method used for the synthesis of 7,
propargylic derivate (9) (400 mg, 1.50 mmol) in dry toluene
(15 ml) was warmed at the reflux temperature during 12 h to
give 1-(20-thienyl)-2-(4-ethynylphenyl)ethyne (10), 295 mg
(94%) as a yellow solid, mp 90–92 8C. UV–vis (CH2Cl2),
lmax (nm): 337, 316, 281, 269. Fluorescence (CH2Cl2), lmax
(nm): 410 and 392 (fZ0.142). FT-IR (KBr, cmK1): 3273,
2195, 1523, 1489, 1421, 832. 1H NMR (300 MHz, CDCl3):
d 7.46 (s, 4H); 7.32 (d, 1H, JZ4.8 Hz); 7.30 (d, 1H, JZ
3.2 Hz); 7.03 (dd, 1H, JZ4.8, 3.2 Hz); 3.19 (s, 1H). 13C
NMR (75 MHz, CDCl3): d 132.2, 132.1, 131.2, 127.7,
127.2, 123.4, 122.9, 122.0, 92.5, 83.2, 79.0, 77.4. C14H8S
(208.03): Anal. Calcd C 80.73, H 3.87; found: C 80.61,
H 4.02.
4.1.5. (E)-1-[4-(3-Hydroxy-3-methyl-1-butyn)phenyl]-2-
(20-thienyl)ethene, (E)-6. General procedure to the
heterocoupling reaction. To a solution of (E)-1-(p-
iodophenyl)-2-(20-thienyl)ethene (E)-5, 5 g (16.02 mmol)
in freshly distilled and saturated in argon diethylamine
(25 ml), and 2-methylbut-3-yn-2-ol (2.05 g, 24.3 mmol),
was added in this order, dichlorobis[(triphenyl)phosphine]-
palladium (113 mg, 0.16 mmol) and a little amount of
copper(I) iodide. The mixture was stirred at room
temperature and after 20 h, was concentrated at reduced
pressure and then was added an aqueous solution of
saturated ammonium chloride and potassium cyanide. The
mixture was extracted with dichloromethane and the
organic layer was dried on anhydrous magnesium sulphate.
After filtration, solvent was removed to give (E)-1-(4-(3-
hydroxy-3-methyl-1-butyn)-phenyl)-2-(20-thienyl)ethene,
4.1.9. 1-[p-(3-Hydroxy-3-methyl-1-butyn)phenyl]-2-(p-
N,N-dimethylaminophenyl)ethyne. Following the general
method used for the synthesis of 6, a mixture of terminal
acetylene 11 (221 mg, 0.64 mmol), 2-methyl-but-3-yn-2-ol
(53 mg, 0.64 mmol) in diethylamine (3 ml), dichlorobis
[(triphenyl)phosphine]palladium (6 mg, 0.0064 mmol) and
a little amount of copper(I) iodide. The mixture was stirred
at room temperature for 8 h. After purification gives 1-[p-(3-
hydroxy-3-mehyl-1-butyn)phenyl]-2-(p-N,N-dimethylami-
nophenyl)ethyne 158 mg (82%) as a brown solid, mp
1
4.03 g (94%) as a brown solid, mp 144–147 8C. H NMR
(300 MHz, CDCl3): d 7.50 (br s, 4H); 7.25 (d, 1H, JZ
5.0 Hz); 7.24 (d, 1H, JZ16.1 Hz); 7.08 (d, 1H, JZ3.4 Hz);
7.00 (dd, 1H, JZ5.0, 3.4 Hz); 6.88 (d, 1H, JZ16.1 Hz);
1.62 (s, 6H). 13C NMR (75 MHz, CDCl3): d 142.6, 136.8,
131.9, 127.4, 127.7, 126.5, 126.0, 124.7, 122.5, 121.6, 94.6,
84.0, 65.6, 31.0.
1
4.1.6. (E)-1-(20-Thienyl)-2-(p-ethynylphenyl)ethene, (E)-
7. To a solution of the propargylic derivate (E)-6 (5.04 g,
18.8 mmol) in dry toluene (50 ml), under argon atmosphere,
was added a little amount of powered sodium hydroxide.
The mixture was warmed at reflux temperature during 12 h.
After, the solution was filtered and the solvent was
eliminated at reduced pressure. The residual oil was purified
by silica gel column chromatography using hexane/
dichloromethane 2:1 as the eluent to give (E)-7, 2.8 g
(72%) as a yellow solid, mp 117–119 8C. UV–vis (CH2Cl2),
lmax (nm): 341, 240. Fluorescence (CH2Cl2), lmax (nm): 450
and 420 (fZ0.129). FT-IR (KBr, cmK1): 3271, 1590, 1514,
1411, 949, 829. 1H NMR (300 MHz, CDCl3): d 7.40 (d, 2H,
JZ8.6 Hz), 7.39 (d, 2H, JZ8.6 Hz); 7.24 (d, 1H, JZ
16.1 Hz); 7.22 (d, 1H, JZ5.0 Hz); 7.08 (d, 1H, JZ3.4 Hz);
7.00 (dd, 1H, JZ5.0, 3.4 Hz); 6.88 (d, 1H, JZ16.1 Hz);
3.15 (s, 1H). 13C NMR (75 MHz, CDCl3): d 142.5, 137.5,
132.5, 127.7, 127.4, 126.6, 126.1, 124.8, 122.9, 118.9, 83.7,
77.9. C14H10S (210.05): Anal. Calcd C 79.96, H 4.79;
found: C 79.71, H 4.60.
90–93 8C. H NMR (300 MHz, CDCl3): d 7.43 (d, 2H, JZ
8.6 Hz); 7.40 (d, 2H, JZ9.0 Hz); 7.35 (d, 2H, JZ8.6 Hz);
6.66 (d, 2H, JZ9.0 Hz); 3.00 (s, 6H); 1.62 (s, 6H).
4.1.10. 1-(p-N,N-Dimethylaminophenyl)-2-(p-ethynyl-
phenyl)ethyne (12). Following the general method used
for the synthesis of 7, propargylic derivate (158 mg,
0.52 mmol) in dry toluene (5 ml) was warmed at the reflux
temperature during 12 h to give 1-(p-N,N-dimethylamino-
phenyl)-2-(p-ethynylphenyl)ethyne (12), 115.4 mg (90%)
as a red solid, mp 138–140 8C. UV–vis (CH2Cl2), lmax (nm):
´
354, 280, 269. Fluorescence (CH2Cl2), l max (nm): 443
(fZ0.238). FT-IR (KBr): 3240 (C^CH); 2208 (C^C);
1606 and 1523 (C]C); 1351 (C–N); 818 (p-disust. ArH).
1H NMR (300 MHz, CDCl3): d 7.44 (s, 4H,); 7.40 (d, 2H,
JZ8.6 Hz); 6.66 (d, 2H, JZ8.6 Hz); 3.15 (s, 1H); 3.00 (s,
6H). 13C NMR (75 MHz, CDCl3): d 150.2, 132.7, 131.9,
131.0, 124.7, 120.8, 111.7, 109.5, 92.9, 87.0, 83.5, 78.4,
40.1. C18H15N (245.12): Anal. Calcd C 88.13, H 6.16, N
5.71; found: C 87.92, H 6.14, N 5.58.
4.1.7. 1-[4-(3-Hydroxy-3-methyl-1-butyn)phenyl]-2-(20-
thienyl)ethyne (9). Following the general method used for
the synthesis of 6, a mixture of 1-(p-iodophenyl)-2-(20-
thienyl)ethyne (550 mg, 1.77 mmol) (8), 2-methyl-but-3-
yn-2-ol (149 mg, 1.77 mmol) in diethylamine (10 ml),
dichlorobis[(triphenyl)phosphine]palladium (13.3 mg,
0.018 mmol) and a little amount of copper(I) iodide. The
mixture was stirred at room temperature for 8 h. After
purification gives 1-(4-(3-hydroxy-3-methyl-1-butyn)phe-
nyl)-2-(20-thienyl)ethylene (9), 400 mg (85%) as a white
solid, mp 102–105 8C. FT-IR (KBr, cmK1): 3240, 1523,
1428, 832. 1H NMR (300 MHz, CDCl3): d 7.43 (d, 2H, JZ
8.6 Hz); 7.37 (d, 2H, JZ8.6 Hz); 7.29 (d, 1H, JZ5.2 Hz);
4.1.11. (E)-1-(20-Thienyl)-2-(4-bromoethynylphenyl)-
ethene (E)-13. Bromine (152 mg) was added to a solution
of potassium hydroxide (142 mg, 2.54 mmol) in water
(5 ml) and vigorously stirred at K5 8C for 15 min. A pale
yellow solution 0of KOBr was formed and then, was slowly
added (E)-1-(2 -thienyl)-2-(p-ethenylphenyl)ethene (E)-7
(200 mg, 0.95 mmol) in 15 ml of tetrahydrofuran, main-
tained the solution between 10–20 8C. The mixture was
stirred at room temperature overnight and then the solvent
removed. The residual solid was extracted with dichloro-
methane and the organic layer was dried on anhydrous
magnesium sulphate, filtered and solvent evaporated to give
a brown solid that was purified by silica gel column

3120
J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
chromatography using hexane–dichloromethane (1/1) as the
eluent, to give (E)-1-(2-thienyl)-2-(4-bromoethenylphenyl)-
ethene (E)-13, 200 mg (70%) as a red-orange solid. This
compound should be used without delay.
390 (fZ0.296). FT-IR (KBr, cmK1): 2197, 1595, 1524,
1424, 831. 1H NMR (300 MHz, CDCl3): d 7.49 (s, 8H), 7.33
(d, 2H, JZ5.2 Hz); 7.30 (d, 2H, JZ3.7 Hz); 7.03 (dd, 2H,
JZ5.2, 3.7 Hz). 13C NMR (75 MHz, CDCl3): d 132.4,
131.5, 131.3, 127.8, 127.2, 123.9, 123.0, 121.5, 92.5, 85.4,
82.1. MS (MALDI-TOF): 390.0. C26H14S2 (390.05): Anal.
Calcd C 79.96, H 3.61; found: C 79.75, H 3.97.
4.1.12. (E,E)-1,4-Di(4-(2-(2-thienyl)ethenyl)phenyl)-1,3-
butadiyne, (E,E)-14. To a solution of hydroxylamine$HCl
(200 mg) in water (10 ml), an aqueous solution of
ethylamine (70%, 10 ml) methanol (50 ml) and a little
amount of copper(I) chloride, under argon atmosphere, was
added (E)-1-(2-thienyl)-2-(4-ethenylp0henyl)ethene (E)-7
(147 mg, 0.70 mmol) and (E)-1-(2 -thienyl)-2-(4-bro-
moethenylphenyl)ethene (E)-13 (200 mg, 0.70 mmol)
between 30–35 8C. After 1 h the mixture was hydrolyzed
with a saturated aqueous ammonium chloride solution with
vigorous stirring and extracted with dichloromethane. The
organic layer was dried on anhydrous magnesium sulphate,
filtered and the solvent evaporated to give (E,E)-1,4-di-(4-
(2-(2-thienyl)ethenyl)phenyl)butadiyne (E,E)-14, 65 mg
(45%), as a yellow solid, mp O300 8C. UV–vis
(CH2Cl2), lmax (nm): 347, 248. Fluorescence (CH2Cl2),
lmax (nm): 454 and 427 (fZ0.289). FT-IR (KBr, cmK1):
2143, 1621, 1514, 1410, 831. 1H NMR (300 MHz, CDCl3):
d 7.45 (d, 2H, JZ8.6 Hz); 7.40 (d, 2H, JZ8.6 Hz); 7.24
(d, 1H, JZ16.1 Hz); 7.21 (d, 1H, JZ5.0 Hz); 7.09 (d,1H,
JZ3.4 Hz); 7.01 (dd, 1H, JZ5.0, 3.4 Hz); 6.88 (d, 1H, JZ
16.1 Hz). MS (70 eV): 418 (MC, 100), 209 (M2C, 6).
C28H18S2 (418.08): Anal. Calcd C 80.34, H 4.33; found: C
80.17, H 4.49.
4.1.15. 2,5-[Di(p-N,N-dimethylamino)phenylethynyl]-
thiophene (17). Following the general method used for
the synthesis of 6, a mixture of terminal acetylene 11
(100 mg, 0.68 mmol), 2,5-di(iodo)thiophene (231 mg,
0.68 mmol) in diethylamine (10 ml), dichlorobis[triphenyl-
phosphine]palladium (48 mg, 0.068 mmol) and a little
amount of copper(I) iodide. The mixture was stirred at
room temperature for 3 h. After purification gives 2,5-[di(p-
N,N-dimethylamino)phenylethynyl]thiophene (17) 246 mg
(98%), as a yellow solid, p.f. 181–183 8C. UV–vis
(CH2Cl2), lmax (nm): 385. Fluorescence (CH2Cl2), lmax
(nm): 456 (fZ0.23). FT-IR (KBr, cmK1): 2157, 1578,
1466, 1372. 1H NMR (300 MHz, CDCl3): d 7.38 (d, 4H, JZ
8.0 Hz); 7.05 (s, 2H); 6.64 (d, 4H, JZ8.0 Hz); 2.99 (s, 12H).
13C NMR (75 MHz, CDCl3): d 149.1, 133.4, 131.5, 122.3,
113.8, 112.3, 92.7, 86.4, 41.0. MS (FABC) m/z 370.1 (MC,
100), 170.1 (31). C24H22N2S (370.15): Anal. Calcd C 77.80,
H 5.98, N 7.56; found: C 78.63, H 5.78, N 7.43
4.1.16. 2,5-[Di(p-N,N-dimethylamino)(phenylethynyl)
(phenylethynyl)]thiophene (19). Following the general
method used for the synthesis of 6, a mixture of terminal
acetylene 12 (115.4 mg, 0.47 mmol), 2,5-di(iodo)thiophene
(157 mg, 0.47 mmol) in diethylamine (10 ml), dichlorobis
[triphenylphosphine]palladium (33 mg, 0.047 mmol) and
a little amount of copper(I) iodide. The mixture was stirred
at room temperature for 5 h. After purification gives 2,5-
[di(p-N,N-dimethylamino)(phenylethynyl)(phenylethynyl)]-
thiophene (19) 227 mg (85%), as a yellow solid, p.f. 227–
230 8C. UV–vis (CH2Cl2), lmax (nm): 393. Fluorescence
(CH2Cl2), lmax (nm): 512 (fZ0.30). FT-IR (KBr, cmK1):
2153, 1552, 1428, 1381. 1H NMR (300 MHz, CDCl3): d 7.46
(m, 8H); 7.43 (d, 4H, JZ8.0 Hz); 7.16 (s, 2H); 6.66 (d, 4H,
JZ8.0 Hz); 3.00 (s, 12H). 13C NMR (75 MHz, CDCl3): d
149.3, 133.2, 131.9, 131.5, 122.6, 122.3, 113.9, 112.2, 92.9,
92.8, 92.7, 86.5, 40.4. MS (FABC): 570.2 (MC, 100), 370.1
(43). C24H22N2S (570.20): Anal. Calcd C 84.18, H 5.30, N
4.91; found: C 84.93, H 5.29, N 4.73.
4.1.13. (1,4-Di(4-(20-thienyl)ethynyl)phenyl)-1,3-buta-
diyne (15). To a solution of cuprous chloride (35.4 mg,
0.18 mmol) in dry pyridine (5 ml), under an oxyge0n
atmosphere, at 40 8C was added a solution of 1-(2 -
thienyl)-2-(p-ethynylphenyl)ethyne
(8)
(150 mg,
0.72 mmol) in dry pyridine (5 ml) and the mixture was
stirred for 30 min. The solvent was removed and the
residual solid was washed with ammonium hydroxide and
extracted with dichloromethane. The organic layer was
dried on anhydrous magnesium sulphate, filtered and
solvent evaporated to give (1,4-di(4-(20-thienyl)ethynyl)-
phenyl)-1,3-butadiyne (15), 69 mg (61%) as a yellow solid,
mp 239–240 8C. UV–vis (CH2Cl2), lmax (nm): 359, 260,
244. Fluorescence (CH2Cl2), lmax (nm): 421 (fZ0.364).
FT-IR (KBr, cmK1): 2198, 1594, 1521, 1487, 829. 1H NMR
(300 MHz, CDCl3): d 7.49 (s, 8H); 7.33 (d, 2H, JZ5.4 Hz);
7.30 (d, 2H, JZ3.8 Hz); 7.03 (dd, 2H, JZ5.4, 3.8 Hz). 13C
NMR (75 MHz, CDCl3): d 133.1, 132.8, 131.6, 129.3,
127.8, 123.8, 121.9, 120.9, 92.4, 85.8, 82.6, 75.6. MS
(MALDI-TOF): 414.0. C28H14S2 (414.05): Anal. Calcd C
81.13, H 3.40; found: C 80.98, H 3.63.
4.1.17. 2,5-Di-[2-(4-((E)-2-(thiophen-2-yl)vinyl)phenyl-
ethynyl)]thiophene (21). Following the general method
used for the synthesis of 6, a mixture of terminal acetylene 7
(60 mg, 0.29 mmol), 2,5-di(iodo)thiophene (50 mg,
0.15 mmol) in diethylamine (10 ml), dichlorobis[triphenyl-
phosphine]palladium (21 mg, 0.03 mmol) and a little
amount of copper(I) iodide. The mixture was stirred at
room temperature for 7 h. After purification gives 2,5-di-[2-
(4-((E)-2-(thiophen-2-yl)vinyl)phenylethynyl)]thiophene
(21) 46 mg (65%), as a yellow solid, p.f. 261–262 8C. UV–
vis (CH2Cl2), lmax (nm): 367. Fluorescence (CH2Cl2), lmax
(nm): 462 and 440 (fZ0.10). FT-IR (KBr, cmK1): 3295,
1579, 1505, 1437, 825. 1H NMR (300 MHz, CDCl3): d 7.45
(s, 8H); 7.35 (d, 1H, JZ4.8 Hz), 7.27 (d, 2H, JZ15.9 Hz);
7.15 (d, 2H, JZ3.8 Hz); 7.10 (s, 2H); 7.02 (dd, 2H, JZ4.8,
3.8 Hz); 6.90 (d, 2H, JZ15.9 Hz). MS (MALDI-TOF):
4.1.14. (Di-(p-(20-thienyl)ethynyl)phenyl)ethyne (16).
Following the general method used for the synthesis of 6,
a mixture of terminal acetylene 8 (100 mg, 0.32 mmol),
1-(20-thienyl)-2-(p-ethynylphenyl)ethylene (10) (66 mg,
0.32 mmol) in diethylamine (10 ml), dichlorobis[triphenyl-
phosphine]palladium (23 mg, 0.032 mmol) and a little
amount of copper(I) iodide. The mixture was stirred at
room temperature for 30 min. After purification gives (di(p-
(20-thienyl)ethynyl)phenyl)ethyne (16), 99 mg (38%), as a
brown-red solid, p.f.O 230 8C. UV–vis (CH2Cl2), lmax
(nm): 352, 243. Fluorescence (CH2Cl2), lmax (nm): 410 and

J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
3121
500.0. C32H20S3 (500.07): Anal. Calcd C 76.76, H 4.03;
found: C 76.61, H 4.32.
4.1.21. 2,5-Di-{{{[3,5-bis(trimethylsilylethynyl)phenyl]-
ethynylphenyl}ethynylphenyl}ethynyl}thiophene (28).
Following the general method used for the synthesis of 6,
a mixture of terminal acetylene 25 (100 mg, 0.20 mmol),
2,5-di(iodo)thiophene (34 mg, 0.10 mmol) in diethylamine
(10 ml), dichlorobis[triphenylphosphine]palladium (10 mg,
0.02 mmol) and a little amount of copper(I) iodide. The
mixture was stirred at room temperature for 12 h. After
purification gives 2,5-di-{{{[3,5-bis(trimethylsilylethynyl)-
phenyl]ethynylphenyl}ethynylphenyl}ethynyl}thiophene
(28) 88 mg (80%), as a green solid, p.f. 291–293 8C. UV–vis
(CH2Cl2), lmax (nm): 377. Fluorescence (CH2Cl2), lmax
(nm): 454 and 429 (fZ0.54). FT-IR (KBr, cmK1): 2159,
1577, 1409, 1249, 759. 1H NMR (300 MHz, CDCl3): d 7.56
(d, 4H, JZ1.6 Hz), 7.53 (t, 2H, JZ1.6 Hz), 7.52 (br s, 8H),
7.51 (d, 4H, JZ8.9 Hz), 7.47 (d, 4H, JZ8.9 Hz), 7.18 (s, 2H),
0.24 (s, 36H). 13C NMR (75 MHz, CDCl3): d 135.0, 134.5,
132.2, 131.6, 131.4, 124.7, 123.8, 123.5, 123.2, 123.1, 122.9,
103.1, 95.8, 94.0, 91.2, 91.1, 90.1, 89.7, 84.27, K0.2. MS
(70 eV): 1068 (MC, 100), 520 (40). C72H66SSi4 (1069.65):
Anal. Calcd C 80.85, H 5.65; found: C 80.91, H 5.59.
4.1.18. 2,5-Di-[2-(thienylethynyl)(phenylethynyl)]thio-
phene (22). Following the general method used for the
synthesis of 6, a mixture of terminal acetylene 10 (47 mg,
0.23 mmol), 2,5-di(iodo)thiophene (41 mg, 0.12 mmol) in
diethylamine (10 ml), dichlorobis[triphenylphosphine]pal-
ladium (16 mg, 0.023 mmol) and a little amount of
copper(I) iodide. The mixture was stirred at room
temperature for 7 h. After purification gives 2,5-di-[2-
(thienylethynyl)(phenylethynyl)]thiophene (22) 48 mg
(85%), as a yellow solid, p.f. 234–235 8C. UV–vis
(CH2Cl2), lmax (nm): 379. Fluorescence (CH2Cl2), lmax
(nm): 423 and 398 (fZ0.34). FT-IR (KBr, cmK1): 3311,
1592, 1519, 1448, 830. 1H NMR (300 MHz, CDCl3): d 7.49
(s, 8H); 7.32 (d, 2H, JZ4.8 Hz); 7.31 (d, 2H, JZ4.3 Hz);
7.18 (s, 2H); 7.03 (dd, 2H, JZ4.8, 4.3 Hz). MS (MALDI-
TOF): 495.9. C32H16S3 (496.04): Anal. Calcd C 77.38, H
3.25; found: C 77.72, H 3.06.
Acknowledgements
4.1.19. 2,5-Di-[(3,5-bis-trimethylsilylethynylphenyl)-
ethynyl]thiophene (26). Following the general method
used for the synthesis of 6, a mixture of terminal acetylene
23 (175 mg, 0.60 mmol), 2,5-di(iodo)thiophene (100 mg,
0.30 mmol) in diethylamine (10 ml), dichlorobis[triphenyl-
phosphine]palladium (42 mg, 0.06 mmol) and a little
amount of copper(I) iodide. The mixture was stirred at
room temperature for 12 h. After purification gives 2,5-di-
[(3,5-bis-trimethylsilylethynylphenyl)ethynyl]thiophene
(26) 191 mg (97%), as a green solid, p.f. 139–140 8C. UV–
vis (CH2Cl2), lmax (nm): 355. Fluorescence (CH2Cl2), lmax
(nm): 410 and 391 (fZ0.20). FT-IR (KBr, cmK1): 2156,
1579, 1410, 1250, 758. 1H NMR (300 MHz, CDCl3): d 7.55
(d, 4H, JZ1.6 Hz); 7.53 (t, 2H, JZ1.6 Hz); 7.14 (s, 2H); 0.24
(s, 36H). 13C NMR (75 MHz, CDCl3): d 135.1, 134.3, 132.2,
124.5, 123.8, 123.0, 103.0, 95.9, 92.6, 83.1, K0.2. MS
(70 eV): 668 (MC, 100), 320 (23), 73 (90). C40H44SSi4
(669.19): Anal. Calcd C 71.79, H 6.63; found: C 71.83, H 6.60.
We thank M. C. Rodriguez and S. I. Pereira for the
computational analyses.
References and notes
1. (a) Bunz, U. H. F. Chem. Rev. 2000, 100, 1605. (b) Irie, M.
Chem. Rev. 2000, 100, 1685. (c) Delaire, J. A.; Nakatani, K.
Chem. Rev. 2000, 100, 1817.
2. Gust, D.; Moore, T. A. Science 1989, 244, 35.
3. Ziessel, R. In Photosensitization and Photocatalysis
using Inorganic and Organometallic Compounds;
¨
Kalyanasundaram, K., Gratzel, M., Eds.; Kluwer Academic:
Dordecht, 1993; p 217.
¨
4. O’Regan, B.; Gratzel, M. Nature 1991, 353, 737.
5. Reynolds, J. R. J. Mol. Electron 1986, 2, 1.
6. Grubbs, R. H.; Gorman, C. B.; Ginsburg, E. J.; Perry, J. W.;
Marder, S. R. In Materials with Nonlinear Optics, Chemical
Perspectives; Marder, S. R., Sohn, J. E., Stricky, G. D., Eds.;
ACS Symposium Series: Washington, DC, 1991; p 455.
7. Barker, J. R. In Molecular Electronics; Petty, M. C.,
Bryce, M. R., Bloor, D., Eds.; Edward Arnold: London,
1995; p 345.
4.1.20. 2,5-Di-{[(3,5-bis-trimethylsilylethynylphenyl)-
ethynylphenyl]ethynyl}thiophene (27). Following the
general method used for the synthesis of 6, a mixture
of terminal acetylene 24 (233 mg, 0.60 mmol), 2,5-di
(iodo)thiophene (100 mg, 0.30 mmol) in diethylamine
(10 ml), dichlorobis[triphenylphosphine]palladium (42 mg,
0.06 mmol) and a little amount of copper(I) iodide. The
mixture was stirred at room temperature for 12 h. After
purification gives 2,5-di-{[(3,5-bis-trimethylsilylethynyl-
phenyl)ethynylphenyl]ethynyl}thiophene (27) 249 mg
(97%), as a green solid, p.f. 218–220 8C. UV–vis
(CH2Cl2), lmax (nm): 379. Fluorescence (CH2Cl2), lmax
(nm): 447 and 421 (fZ0.42). FT-IR (KBr, cmK1): 2159,
1577, 1409, 1249, 759. 1H NMR (300 MHz, CDCl3): d 7.56
(d, 4H, JZ1.6 Hz), 7.53 (t, 2H, JZ1.6 Hz), 7.51 (d, 4H, JZ
8.7 Hz), 7.46 (d, 4H, JZ8.7 Hz), 7.18 (s, 2H), 0.24 (s, 36H).
13C NMR (75 MHz, CDCl3): d 135.0, 134.5, 132.1, 131.6,
131.4, 124.7, 123.8, 123.4, 123.0, 122.7, 103.1, 95.8, 93.9,
89.9, 89.8, 84.9, K0.2. MS (70 eV): 868.3 (MC, 100); 419.3
(30). C56H52SSi4 (869.42): Anal. Calcd C 77.36, H 6.03;
found: C 77.43, H 5.98.
8. Varanasi, P. R.; Jen, A. K. Y.; Chandrasekhar, J.; Namboothiri,
I. N. N.; Rathna, A. J. Am. Chem. Soc. 1996, 118, 12443.
9. Albert, I. D. L.; Marks, T. J.; Ratner, M. A. J. Am. Chem. Soc.
1997, 119, 6575.
10. (a) Zhu, Y.; Wolf, M. O. J. Am. Chem. Soc. 2000, 122, 10121. (b)
¨
Granstrom, M.; Petritsch, K.; Arias, A. C.; Lux, A.; Andersson,
M. R.; Friend, R. H. Nature 1998, 395, 257. (c) Skotheim, T. A.;
Elsenbaumer, R. L.; Reynolds, J. R. Handbook of Conducting
Polymers, 2nd ed.; Marcel Dekker: New York, 1998.
11. Torsi, L.; Dodabalapur, A.; Rothberg, L. J.; Fung, A. W. P.;
Katz, H. E. Science 1996, 272, 1462.
12. (a) Lu, H. F.; Chan, H. S. O.; Ng, S. C. Macromolecules 2003,
36, 1543. (b) Lukes, V.; Breza, M.; Vegh, D.; Hrdlovic, P.;
Krajcovic, J.; Laurinc, V. Synth. Met. 2002, 129, 85.
(c) Raimundo, J. M.; Blanchard, P.; Gallego-Planas, N.;
Mercier, N.; Ledoux-Rak, I.; Hierle, R.; Roncali, J. J. Org.

3122
J. G. Rodriguez et al. / Tetrahedron 62 (2006) 3112–3122
17. Beny, J. P.; Dhawan, S. N.; Kagan, J.; Sundlass, S. J. Org.
Chem. 2002, 67, 205. (d) Otsubo, T.; Aso, Y.; Takimiya, K.
Bull. Chem. Soc. Jpn. 2001, 74, 1789. (e) Zhu, Y.; Wolf, M. O.
Chem. Mater. 1999, 11, 2995. (f) Kingsborough, R. P.;
Swager, T. M. Prog. Inorg. Chem. 1999, 48, 123. (g)
Ley, K. D.; Schanze, K. S. Coord. Chem. Rev. 1998, 171,
287. (h) Reddinger, J. L.; Reynolds, J. R. Macromolecules
1997, 30, 673. (i) Segawa, H.; Wu, F. P.; Nakayama, N.;
Maruyama, H.; Sagisaka, S.; Higuchi, N.; Fujitsuka, M.;
Shimidzu, T. Synth. Met. 1995, 71, 2151. (j) Zotti, G.; Zecchin,
S.; Schiavon, G.; Berlin, A.; Pagani, G.; Canavesi, A. Chem.
Mater. 1995, 7, 2309.
Chem. 1982, 47, 2201.
18. Baati, R.; Barma, D. K.; Murali Krishna, U.; Mioskowski, C.;
Falck, J. R. Tetrahedron Lett. 2002, 6, 959.
19. (a) Vaitiekunas, A.; Nord, F. F. J. Org. Chem. 1954, 19, 902.
(b) Keskin, H.; Miller, R. E.; Nord, F. F. J. Org. Chem. 1951,
16, 199.
20. Johansen, O.; Sasse, W. H. F.; Hoskinson, R. M.; Russell, I. M.
J. Text. Inst. 1976, 67, 146.
21. (a) Glaser, G. Chem. Ber. 1869, 2, 422. (b) Glaser, G. Liebigs
Ann. Chem. 1870, 159.
13. (a) Peng, Z. H.; Pan, Y. C.; Xu, B. B.; Zhang, J. H. J. Am.
Chem. Soc. 2000, 122, 6619. (b) Xu, Z. F.; Moore, J. S. Acta
Polym. 1994, 45, 83.
22. Sarkar, A.; Okada, S.; Nakanishi, H.; Matsuda, H. Helv. Chem.
Acta 1999, 82, 138.
23. All calculations have been performed at the B3LYP* level,
using 6-31G basis set for hydrogen, carbon, nitrogen and
sulfur, and the Hay–Wadt small-core effective core potential
(ECP). (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(b) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
(c) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys. 1980,
58, 1200. (d) Hehre, W. J.; Radom, L.; Schleyer, P. V. R.;
Pople, J. A. Ab Initio Molecular Orbital Theory; Wiley: New
York, 1986; p 76 and references therein.
14. (a) Xu, M. H.; Pu, L. Tetrahedron Lett. 2002, 43, 6541. (b)
Pearson, D. L.; Tour, J. M. J. Org. Chem. 1997, 62, 1376.
´
15. (a) Rodrıguez, J. G.; Tejedor, J. L. J. Org. Chem. 2002, 67, 7631.
´
(b) Rodrıguez, J. G.; Esquivias, J. Tetrahedron Lett. 2003, 26,
´ ´
4831. (c) Rodrıguez, J. G.; Tejedor, J. L.; Esquivias, J.; Dıaz, C.
´
Tetrahedron Lett. 2003, 26, 6375. (d) Rodrıguez, J. G.;
´
Esquivias, J.; Lafuente, A.; Dıaz, C. J. Org. Chem. 2003, 68,
´
8120. (e) Rodrıguez, J. G.; Lafuente, A.; Rubio, L. Tetrahedron
´
Lett. 2004, 45, 5685. (f) Rodrıguez, J. G.; Lafuente, A.; Rubio,
24. Mayor, M.; Didschies, C. Angew. Chem., Int. Ed. 2003, 42,
3176.
L.; Esquivias, J. Tetrahedron Lett. 2004, 45, 7061.
16. Birnbaum, D.; Kohler, B. E.; Spangler, C. W. J. Chem. Phys.
1991, 94, 1684.
25. Han, X.; Yang, M.; Xu, G.; Liu, X.; Ye, P. Macromol. Rapid
Commun. 2001, 22, 358.