Synthesis of alkynylated selenophenes by site-selective sonogashira reactions of tetrabromoselenophene

Article abstract of DOI:10.1002/ejoc.201201440

Mono-, di-, and tetraalkynylated selenophenes were prepared by site-selective Sonogashira reactions of tetrabromoselenophene. Aryl-, alkyl-, and trimethylsilylacetylenes were suitable substrates for this procedure. The first attack occurred regioselective

Full text of DOI:10.1002/ejoc.201201440

FULL PAPER
DOI: 10.1002/ejoc.201201440
Synthesis of Alkynylated Selenophenes by Site-Selective Sonogashira Reactions
of Tetrabromoselenophene
Peter Ehlers,[a,b] Tung T. Dang,[a] Tamás Patonay,[c] Alexander Villinger,[a] and
Peter Langer*[a,b]
Keywords: Heterocycles / Selenium / Alkynes / Cross-coupling / Palladium / Regioselectivity
Mono-, di-, and tetraalkynylated selenophenes were pre-
pared by site-selective Sonogashira reactions of tetrabromo-
selenophene. Aryl-, alkyl-, and trimethylsilylacetylenes were
suitable substrates for this procedure. The first attack oc-
curred regioselectively at C-2 and C-5. In addition, dif-
ferently diarylated dialkynylselenophenes were prepared
using site-selective Suzuki and Sonogashira reactions.
sulfur counterparts, selenophenes are little studied, due to
a lack of suitable synthetic methods. Chemical transforma-
tions and syntheses of selenium heterocycles are, in general,
more difficult to carry out than those of their sulfur ana-
logues, because of the lower stability of selenium heterocy-
cles. Synthetic procedures developed for sulfur heterocycles
cannot usually simply be applied to their selenium ana-
logues, and an individual development or optimization is
usually required. In contrast to sulfur, oxygen, and nitrogen
heterocycles, palladium-catalyzed cross-coupling reactions
of selenium heterocycles are relatively rare.
In recent years, we have developed site-selective Suzuki–
Miyaura reactions of tetrabromothiophene,[16] tetrabromo-
N-methylpyrrole,[17] tetrabromofuran,[18] and tetrabromose-
lenophene.[19] We have also reported Heck reactions of
tetrabromothiophene and tetrabromo-N-methylpyrrole.[20]
Whitesides et al. have reported Sonogashira reactions of
tetrabromothiophene.[21] We have reported Sonogashira re-
actions of tetrabromo-N-methylpyrrole[22] and of tetra-
bromofuran.[23] In this paper, we report what are, to the
best of our knowledge, the first Sonogashira reactions[24] of
tetrabromoselenophene. These reactions proceed with very
good site-selectivity, and allow a convenient synthesis of
hitherto unknown polyalkynylated selenophenes.
Introduction
Selenium compounds are considerably relevant in phar-
maceutical chemistry.[1] In fact, selenium is an essential ele-
ment for humans, and various diseases result from an insuf-
ficient supply of selenium.[2,3] A number of drugs contain-
ing selenium heterocycles play an important role in the
clinic.[4] For example, selenazofurin is an antitumor and
antiviral agent (Figure 1).[5] Various pharmacological ac-
tivities have been reported for selenophenes, including
muscarinic antagonist activity,[6] antiviral activity,[7] and
antiproliferative activity against human leukemia cells.[8,9]
Selenophenes stabilize microtubules by polymerization of
tubulin.[10] They are cytotoxic against colon carcinoma,[11]
human cervical cancer, and hepatocellular carcinoma.[12] In
addition, selenophenes show antifungal activity.[13]
Figure 1. Structure of selenazofurin.
Moreover, conjugated selenophenes have received signifi-
cant attention in the field of organic electronics.[14] It is
notable that Polyselenophenes have lower band gaps than Results and Discussion
their sulfur analogues. This makes them excellent candi-
dates for OFET (organic field-effect transistor) applications
or polymer solar cells.[15] However, in contrast to their
Tetrabromoselenophene was prepared according to the
procedure of Helmholdt and co-workers by the reaction of
selenophene with an excess of bromine (Scheme 1).[25]
[a] Institut für Chemie, Universität Rostock,
Albert-Einstein-Str. 3a, 18059 Rostock, Germany
Homepage: http://www.langer.chemie.uni-rostock.de/
[b] Leibniz-Institut für Katalyse an der Universität Rostock e.V.,
Albert Einstein Str. 29a, 18059 Rostock, Germany
[c] Department of Organic Chemistry, University of Debrecen,
4032 Debrecen, Egyetem tér 1, Hungary
Scheme 1. Synthesis of tetrabromoselenophene. Conditions:
i) 1) Br2 (7.0 equiv.), 0 °C, CH2Cl2; 2) reflux 72 h; 3) NaOH, H2O
(2 m), reflux, 6 h.
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201201440.
2000
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 2000–2007

Synthesis of Alkynylated Selenophenes
Table 1. Optimization of the synthesis of 3a.
Entry Catalyst
Ligand
Solvent/Base
CuI [mol-%] T [°C] Yield [%][a]
1
2
3
PdCl2(CH3CN)2 (3 mol-%)
P(tBu)3 (6 mol-%)
P(tBu)3 (6 mol-%)
X-Phos (6 mol-%)
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
toluene + ethanol/HN(iPr)2
DMF/NEt3
N(CH2CH2OH)3
HN(iPr)2
2
2
2
20
100
20
100
20
100
80
90
86
73
54
61
66
42
PdCl2(CH3CN)2 (3 mol-%)
PdCl2(CH3CN)2 (3 mol-%)
Pd(PPh3)4 (10 mol-%)
Pd(PPh3)4 (10 mol-%)
Pd(OAc)2 (10 mol-%)
4
10
5[b]
6
7
10 mol-% Pd(PPh3)4 (10 mol-%)
10
[a] Yields of isolated products. [b] Procedure developed by Zeni et al. (Ref.[26]).
Helmholdt used CHCl3 as the solvent and obtained tetra- try 7). The use of a less reactive catalyst system avoids the
bromoselenophene in 39% yield. We found that the yield formation of products with higher degrees of alkynylation.
could be dramatically improved to 84% by using CH2Cl2.
Product 3h could not be prepared, presumably because the
The reaction of tetrabromoselenophene (2) with free OH group of 2-methyl-3-butyn-2-ol underwent com-
2.4 equiv. phenylacetylene gave 2,5-dialkynyl-3,4-dibro- plexation to the metal centre, which led to inhibition of the
moselenophene 3a (Scheme 2). The yield strongly depended reaction. However, the reaction could be successfully car-
on the conditions. To find the best conditions for the Sono- ried out in the more polar solvent DMF under conditions
gashira reaction, we tested different catalyst systems. The developed by Zeni and co-workers (Table 1, entry 5).[26] The
results are listed in Table 1.
reaction proceeds without the need of a copper co-catalyst.
Unfortunately, 1-dimethylamino-2-propyne did not react
under these conditions.
Scheme 2. Optimization of the synthesis of 3a.
Scheme 3. Synthesis of 3a–j. Conditions: i) 2 (1.0 equiv.), RCϵCH
(2.4 equiv.), PdCl2(CH3CN)2 (3 mol-%), CuI (2 mol-%), HP-
(tBu)3BF4 (6 mol-%), 1,4-dioxane, HN(iPr)2, 20 °C, 20 h.
After a thorough optimization, the yield could be im-
proved to up to 90% [Table 1, entry 1, PdCl2(CH3CN)2,
P(tBu)3, dioxane, HN(iPr)2, 20 °C]. The catalyst and ligand
proved to be the most important parameters in the optimi-
zation, while temperature and solvent also played a role. At
first glance, it is surprising that the yield at 100 °C (Table 1,
entry 2) is lower than that obtained at room temperature
(Table 1, entry 1). This can be explained as follows: The re-
action at positions 2 and 5 is favoured because of the elec-
tron-withdrawing effect of the selenium atom. At elevated
temperatures, significant amounts of tri- and tetra-substi-
tuted selenophenes were formed.
The scope of the reaction was studied next (Scheme 3,
Table 2). For aryl- and TMS-substituted acetylenes, the best
yields were obtained when the reactions were carried out
under the optimized conditions outlined above (Table 1, en-
try 1). Only trace amounts of product were isolated when
p-fluorophenylacetylene was used. This can be explained by
the electron-withdrawing nature of the fluoride moiety.
Substitution of one bromide by the p-fluorophenylacetylene
Table 2. Synthesis of 3a–j.
3
R
Yield [%][a]
a
b
c
d
e
f
Ph
3-MeC6H4
Me3Si
4-FC6H4
Oct
CH2NMe2
4-(MeO)C6H4
C(OH)Me2
4-tBuC6H4
CH2OAc
90
83
65
traces
47 (87)[b]
0
g
h
i
40
0 (48)[c]
32
j
71
[a] Yields of isolated products (conditions: Table 1, entry 1).
[b] Yields of isolated products (conditions: Table 1, entry 7).
[c] Yields of isolated products (conditions: Table 1, entry 5).
The structures of all products were confirmed by spectro-
moiety resulted in some activation, and the product reacted scopic methods. The structure of 3b was independently con-
much more quickly with the second molecule of the alkyne firmed by X-ray crystal structure analysis (Figure 2).[27]
than did the starting material. In fact, the tetra-substituted
The synthesis of tetraalkynylselenophenes was studied
selenophene was the major product, and some starting ma- next (Scheme 4, Table 3). In 2008, we described the synthe-
terial 2 was also recovered. In the case of 1-decyne, product sis of tetraalkynylselenophene 4a in 77% yield.[19] However,
3e was isolated in only 47% yield using the optimized con- the procedure required a very high palladium concentra-
ditions (Table 1, entry 1). But the yield increased to 87% tion, and was not catalytic with respect to CuI. Thus, it was
when the reaction was carried out under similar conditions our objective to develop a new procedure that would allow
that we had developed for the Sonogashira reaction of the synthesis of tetraalkynylselenophenes with a low cata-
tetrabromopyrrole[22] and tetrabromofuran[23] (Table 1, en- lyst concentration. The reactions were carried out under the
Eur. J. Org. Chem. 2013, 2000–2007
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2001

P. Ehlers, T. T. Dang, T. Patonay, A. Villinger, P. Langer
FULL PAPER
Scheme 5. Synthesis of 5a. Conditions: see Table 4.
Figure 2. ORTEP plot of 3b.
optimized conditions given in Table 1 (entries 1 and 3) with
6 equiv. acetylene. Products 4a,b were prepared using X-
Phos, and 4c,d were prepared using HP(tBu)3BF4 as the
ligand. The moderate yields of 4a–c can be explained as
being due to practical problems during the chromato-
graphic purification.
Figure 3. Crystal structure of 5a.
Analysis of the crude mixture revealed that a high
amount of the monoalkynylated product was formed, but
it was difficult to isolate this product in good yield, presum-
ably due to decomposition during chromatography. There-
fore, we tried to trap the product by the addition of a sec-
ond alkyne and isolation of a more stable (unsymmetrical)
2,5-dialkynylselenophene. The reaction of 2 with two dif-
ferent alkynes gave products 6a,b in good yields (Scheme 6,
Table 5). The reactions were carried out under the condi-
tions given in Table 1, entry 1.
Scheme 4. Synthesis of tetraalkynylated selenophenes 4a–d. Condi-
tions: i) 2 (1.0 equiv.), RCϵCH (6.0 equiv.), PdCl2(CH3CN)2
(3 mol-%), CuI (2 mol-%), HP(tBu)3BF4 or X-Phos (6 mol-%),
HN(iPr)2, 20 °C, 20 h.
Table 3. Synthesis of 4a–d.
4
Ligand
R
Yield [%][a]
a
b
c
X-Phos
X-Phos
P(tBu)3
P(tBu)3
C6H5
34
28
37
87
4-tBuC6H4
4-FC6H4
4-MeC6H4
d
[a] Yields of isolated products.
The synthesis of 5-alkynyl-3,4,5-tribromoselenophenes
proved to be impossible. Optimization of the synthesis of 5-
phenylethynyl-3,4,5-tribromoselenophene (5a) showed that
at least 38% isolated yield could be obtained (Table 4,
Scheme 5). The structure of 5a was independently con-
firmed by X-ray crystal structure analysis (Figure 3).[27]
Scheme 6. Synthesis of unsymmetrical 2,5-dialkynylselenophenes
6a,b. Conditions: i) 2 (1.0 equiv.), R1CϵCH (1.05 equiv.) and
R2CϵCH (1.05 equiv.), PdCl2(CH3CN)2 (3 mol-%), CuI (2 mol-%),
HP(tBu)3BF4 (6 mol-%), HN(iPr)2, 20 °C, 20 h.
Table 4. Optimization of the synthesis of 5a.
Entry
Catalyst
Ligand
Solvent/base
Equiv. alkyne
T [°C]
Yield [%][a]
1
2
3
4
5
6
7
8
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(CH3CN)2Cl2
Pd(PPh3)4
P(tBu)3
P(tBu)3
P(tBu)3
P(tBu)3
P(tBu)3
P(tBu)3
P(Cy)3
P(Cy)3
X-Phos
P(2-Tol)3
–
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
dioxane/HN(iPr)2
DMF/NEt3
1.50
2.00
1.20
1.05
1.05
1.05[b]
1.20
1.20
1.20
1.05
1.50
20
20
20
20
0
traces
0
traces
traces
0
6
0
traces
0
traces
38
0
20
60
20
20
80
9
10
11
[a] Yields of isolated products. [b] Slow addition of the alkyne.
2002
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Synthesis of Alkynylated Selenophenes
Table 5. Synthesis of unsymmetrical 2,5-alkynylated selenophenes.
6
R1
R2
Yield [%][a]
a
b
C6H5
3-MeC6H4
3-MeC6H4
4-tBuC6H4
67
54
[a] Yields of isolated products (small amounts of symmetrical di-
substituted products could not be separated).
The reaction of 2,5-dialkynylselenophenes 3a,b,j with
2.4 equiv. of alkynes gave tetraalkynylselenophenes 7a–d
(Scheme 7, Table 6). Products 7a,b,d were isolated in good
yields, but the yield of 7c was low. This might be explained
Scheme 9. Synthesis of compound 10. Conditions: i) Pd(PPh3)4
(5 mol-%), K3PO4 (4.0 equiv.), boronic acid (2.2 equiv.), toluene,
water, 20 h; ii) PdCl2(CH3CN)2 (3 mol-%), X-Phos (6 mol-%), CuI
by complexation of the acetyl group to the catalyst and in- (2 mol-%), dioxane, HN(iPr)2, alkyne (3.0 equiv.).
hibition of the catalytic cycle. The reactions were carried
out under the conditions reported in Table 1, entry 1.
In conclusion, we have reported the first Sonogashira
cross-coupling reactions of tetrabromoselenophene. A large
number of different alkynylated selenophenes were obtained
in moderate to good yields. The optimized reaction condi-
tions allow the site-selective synthesis of the mono-, di-, and
tetraalkynylselenophenes. Furthermore, tetrasubstituted
selenophenes derived from Suzuki- and Sonogashira cross-
coupling reactions were obtained.
Scheme 7. Synthesis of compounds 7a–d. Conditions: i) 2
(1.0 equiv.), R1CϵCH (2.4 equiv.), PdCl2(CH3CN)2 (3 mol-%), CuI
(2 mol-%), HP(tBu)3BF4 (6 mol-%), HN(iPr)2, 20 °C, 20 h; ii) 4a,b,j
(1.0 equiv.), R2CϵCH (3.0 equiv.), PdCl2(CH3CN)2 (5 mol-%), CuI
(3 mol-%), HP(tBu)3BF4 (10 mol-%), HN(iPr)2, 60 °C, 10 h.
Experimental Section
General Remarks: 1H NMR spectroscopy: Bruker AV 300
(300 MHz) and Bruker AV 400 (400 MHz). References: 0.00 for
TMS, 7.26 for CDCl3. Peak characterization: s = singlet, d = doub-
let, t = triplet, dd = doublet of doublets, q = quartet, m = multiplet.
The spectra were measured with a standard number of scans.
Where the assignment was unclear, all possible proton assignments
are stated. 13C NMR spectroscopy: Bruker AV 300 (75 MHz) and
Bruker AV 400 (100 MHz). References: 0.00 for TMS, 77.00 for
CDCl3. Peak characterization: q = quartet. The DEPT method was
used for determining the presence of primary, secondary, teriary,
and quaternary carbon atoms. Mass spectrometry (MS): Finnigan
MAT 95 XP (electron ionisation EI, 70 eV). High-resolution MS
(HRMS): Finnigan MAT 95 XP. Only measurements with an
average deviation from the theoretical mass of Ϯ2 mDa were con-
sidered to be correct. Infrared spectroscopy (IR): Nicolet 550 FTIR
spectrometer with ATR sampling technique for both solids and
liquids. Signal characterization: w = weak, m = medium, s =
strong. X-ray crystallography: Bruker X8Apex diffractometer with
CCD camera (Mo-Kα radiation and graphite monochromator, λ
= 0.71073 Å). The space groups were determined by the XPREP
program, and the structures were solved using the SHELX-97 pro-
gram package. Refinements were carried out according to the mini-
mum square error method. Elemental analysis (EA): Leco 932 C,
H, N, S. Melting point determination: Micro-Hot-Stage GalenTM
III Cambridge Instruments. Thin-layer chromatography (TLC):
Merck Kieselgel 60 F254 on aluminium foil from Macherey–Nagel.
Detection was carried out under UV light at 254 nm and 365 nm.
The following mixtures were used as stains: 1–2% of either p-anis-
aldehyde or vanillin, glacial acetic acid (10%), sulfuric acid (5%),
and methanol (83–84%). Column chromatography: performed with
Merck Silica Gel 60 or Macherey–Nagel Silica Gel 60 (0.063–
0.200 mm, 70–230 mesh). The finer Merck Silica Gel 60 (0.040–
0.063 mm, 230–400 mesh) was used when appropriate.
Table 6. Synthesis of 7a–d.
4
7
R1
R2
Yield [%][a]
a
a
j
a
b
c
C6H5
C6H5
CH2OAc
3-MeC6H4
CH2OAc
3-MeC6H4
3-MeC6H4
CH2OAc
93
60
22
82
b
d
[a] Yields of isolated products.
A combination of Suzuki and Sonogashira reactions was
investigated next. The reaction of 3a with 4-(methoxy-
phenyl)boronic acid gave 8 in 95% yield (Scheme 8). The
best yields were obtained when the ligand X-Phos was used.
Scheme 8. Synthesis of compound 8. Conditions: i) 3a (1.0 equiv.),
boronic acid (3.0 equiv.), Pd(OAc)2 (2 mol-%), X-Phos (3 mol-%),
K3PO4 (3 equiv.), dioxane, water, 80 °C, 8 h.
Earlier, we reported the synthesis of 2,5-diarylseleno-
phene 9.[17] Its reaction with phenylacetylene gave 10, albeit
in only 24% yield (Scheme 9).
Eur. J. Org. Chem. 2013, 2000–2007
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2003

P. Ehlers, T. T. Dang, T. Patonay, A. Villinger, P. Langer
FULL PAPER
General Procedure for Synthesis of 3a–j: The appropriate alkyne
(2.4 equiv.) was added to a solution of PdCl2(CH3CN)2 (4 mg,
3 mol-%), CuI (2 mg, 2 mol-%), HP(tBu)3BF4 (9 mg, 6 mol-%), and
2 (0.5 mmol, 224 mg) in dioxane (2 mL) and HN(iPr)2 (0.5 mL).
The reaction mixture was stirred for 20 h at room temperature. Af-
ter completion of the reaction time, brine was added. The aqueous
phase was extracted with CH2Cl2 (3ϫ). The combined organic ex-
tracts were dried with Na2SO4 and filtered, and the solution was
concentrated. The residue was purified by column chromatography
(heptane) to obtain 3a–j.
14.1 (CH3), 20.1, 22.7, 28.2, 28.8, 29.0, 29.2, 31.8 (CH2), 103.6,
112.2 (CϵC), 118.3, 127.6 (CHetar). IR (ATR): ν = 2953 (m), 2922
˜
(s), 2853 (s), 2218 (w), 1709 (br., m), 1458 (m), 1377 (w), 1241 (w),
1113 (w), 722 (m) cm–1. MS (EI, = 70 eV): m/z (%) = 562 (76)
[M]+, 465 (100), 436 (12), 353 (24), 327 (28), 287 (23), 207 (69), 165
(63).
3,4-Dibromo-2,5-(4-methoxyphenylacetylene)selenophene (3g): (4-
Methoxyphenyl)acetylene (2.4 equiv., 0.159 mg) was added to a
solution of PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI (2 mg, 2 mol-%),
HP(tBu)3BF4 (9 mg, 6 mol-%), and 2 in dioxane (2 mL) and
HN(iPr)2 (0.5 mL). The reaction mixture was stirred for 20 h at
3,4-Dibromo-2,5-(phenylethynyl)selenophene (3a): Phenylacetylene
(2.4 equiv., 0.132mL) was added to a solution of PdCl2(CH3CN)2 room temperature. Purification resulted in 3g (100 mg, 40%) as a
(4 mg, 3 mol-%), CuI (2 mg, 2 mol-%), HP(tBu)3BF4 (9 mg, 6 mol- yellow solid, m.p. 101–103 °C. 1H NMR (300 MHz, CDCl3): δ =
3
3
%), and 2 in dioxane (2 mL) and HN(iPr)2 (0.5 mL). The reaction
3.83 (s, 6 H, OCH3), 6.89 (d, J = 8.9 Hz, 4 H, Ar), 7.49 (d, J =
8.9 Hz, 4 H, Ar). 13C NMR (75 MHz, CDCl3): δ = 55.4 (OCH3),
82.3, 100.9 (CϵC), 113.9 (CAr/Hetar) 114.2 (CH), 118.8, 123.7 (CAr/
mixture was stirred for 20 h at room temperature. Purification re-
1
sulted in 3a (220 mg, 90%) as a yellow solid, m.p. 119–121 °C. H
NMR (300 MHz, CDCl3): δ = 7.36–7.39 (m, 6 H, Ph), 7.55–7.58
Hetar), 133.2 (CH), 160.4 (CAr). IR (ATR): ν = 3072 (w), 3049 (w),
3033 (w), 3005 (w) 2957 (w), 2938 (w), 2914 (w), 2836 (m), 2196
˜
(m, 4 H, Ph) ppm. 13C NMR (75 MHz, CDCl3): δ = 83.6, 101.0
(CϵC), 119.9, 122.4 (CHetar), 124.2 (CPh), 128.8, 129.6, 131.9 (m), 1600 (s), 1517 (s), 1453 (m), 1290 (s), 1245 (s), 1169 (s), 1021
(CHPh) ppm. IR (ATR): ν = 3142 (w), 3053 (m), 3020 (w), 2957
(s), 822 (s) cm–1. MS (EI, = 70 eV): m/z (%) = 550 (100) [M]+, 535
(w), 2924 (w), 2858 (w), 2202 (w), 1511 (m), 1441 (m), 1292 (br., (33), 316 (13), 295 (14), 280 (23), 262 (37), 247 (20), 235 (17), 223
˜
m), 912 (m), 743 (s), 682 (s) cm–1. MS (EI, = 70 eV): m/z (%) =
491 (22) [M(81Br)]+, 490 (100) [M]+, 330 (15), 250 (87), 125 (25).
HRMS (EI, 70 eV): calcd. for C20H10Br2Se 487.83090; found
487.83051.
(13), 112 (14). HRMS (EI, 70 eV): calcd. for C22H14Br2Se
547.85203; found 547.852633.
4,4Ј-(3,4-Dibromoselenophen-2,5-diyl)bis(2-methylbut-3-yn-2-ol)
(3h): 2-Methyl-3-butyn-2-ol (2.5 equiv., 0.12 mL) was added to a
solution of tetrakispalladium(0) (10 mol-%, 58 mg) and 2
(0.5 mmol, 224 mg) in DMF (3 mL) and NEt3 (1 mL). The reaction
3,4-Dibromo-2,5-bis(m-tolylethynyl)selenophene (3b): m-Tolylacetyl-
ene (2.4 equiv., 0.154 mL) was added to
a
solution of
PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI (2 mg, 2 mol-%), HP- mixture was stirred for 8 h at 80 °C. Purification resulted in 3h
(tBu)3BF4 (9 mg, 6 mol-%), and 2 in dioxane (2 mL) and HN-
(iPr)2 (0.5 mL). The reaction mixture was stirred for 20 h at room
(107 mg, 48 %) as a brown solid, m.p. 150–152 °C. 1H NMR
(300 MHz, CDCl3): δ = 1.64 (s, 12 H, CH3). 13C NMR (75 MHz,
CDCl3): δ = 31.1 (CH3), 66.0 [C(CH3)2OH], 76.1, 105.0 (CϵC),
temperature. Purification resulted in 3b (198 mg, 83%) as a red
1
solid, m.p. 132–133 °C. H NMR (300 MHz, CDCl3): δ = 2.37 (s, 119.7, 123.3 (CHetar). IR (ATR): ν = 3274 (br., m), 2975 (m), 2926
˜
6 H, CH3), 7.18–7.26 (m, 4 H, Ar), 7.35–7.39 (m, 4 H, Ar) ppm. (w), 1511 (m), 1454 (w), 1412 (w), 1377 (m), 1363 (s), 1155 (br., s)
13C NMR (75 MHz, CDCl3): δ = 21.2 (CH3), 83.0, 101.0 (CϵC), cm–1. MS (EI, = 70 eV): m/z (%) = 454 (26) [M]+, 439 (47), 418
119.4, 121.9 (CHetar), 123.9 (CAr), 128.4, 128.7, 130.2, 132.1 (CH), (38), 379 (18), 336 (113), 315 (13), 279 (7), 218 (7). HRMS (EI,
138.3 (CAr) ppm. IR (ATR): ν = 3018 (w), 2953 (w), 2920 (m),
70 eV): calcd. for C14H14O2Br2Se 451.85203; found 451.851938.
˜
2854 (w), 2729 (w), 2199 (w), 1508 (m), 1300 (m), 908 (m), 878 (m),
779 (s), 685 (s) cm–1. MS (EI, 70 eV): m/z (%) = 517 (100) [M]+,
358 (15), 356 (11), 278 (60), 274 (13), 138 (17). C22H14Br2Se
(517.11): calcd. C 51.10, H 2.73; found C 51.07, H 2.85.
3,4-Dibromo-2,5-bis[(4-tert-butylphenyl)ethynyl]selenophene (3i): (4-
tert-Butylphenyl)acetylene (2.4 equiv., 0.159 mg) was added to a
solution of PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI (2 mg, 2 mol-%),
HP(tBu)3BF4 (9 mg, 6 mol-%), and 2 in dioxane (2 mL) and
(3,4-Dibromoselenophene-2,5-diyl)bis(ethyne-2,1-diyl)bis(trimeth- HN(iPr)2 (0.5 mL). The reaction mixture was stirred for 20 h at
ylsilane) (3c): (Trimethylsilyl)acetylene (2.4 equiv., 0.21 mL) was
added to a solution of PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI
(2 mg, 2 mol-%), HP(tBu)3BF4 (9 mg, 6 mol-%), and 2 in dioxane
(2 mL) and HN(iPr)2 (0.5 mL). The reaction mixture was stirred
for 20 h at room temperature. Purification resulted in 3c (150 mg,
65 %) as a brown solid, m.p. 128–129 °C. 1H NMR (300 MHz,
room temperature. Purification resulted in 3i (94 mg, 32%) as a red
1
solid, m.p. 180–182 °C. H NMR (300 MHz, CDCl3): δ = 1.32 (s,
3
3
18 H, CH3), 7.38 (d, J = 8.6 Hz, 4 H, Ar), 7.49 (d, J = 8.7 Hz, 4
H, Ar). 13C NMR (75 MHz, CDCl3): δ = 31.1 (CH3), 34.9
[C(CH3)3], 82.8, 101.0 (CϵC), 119.1, 119.3, 123.9 (CAr/Hetar), 125.5,
131.4 (CH), 152.7 (CAr). IR (ATR): ν = 3084 (w), 3065 (w), 3032
˜
CDCl3): δ = 0.25 (s, 18 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): (w), 2958 (br., m), 2901 (w), 2865 (w), 2202 (m), 1908 (w), 1523
δ = 0.3 (CH3), 97.6, 108.0 (CϵC), 120.4, 124.2 (C) ppm. IR (ATR): (m), 1460 (m), 1406 (s), 1362 (m), 1115 (m), 828 (s) cm–1. MS (EI,
ν = 2953 (m), 2896 (w), 2853 (w), 2784 (w), 2174 (m), 1494 (m),
= 70 eV): m/z (%) = 602 (100) [M]+, 587 (74), 557 (9), 522 (7), 286
(19), 258 (10), 138 (8). C28H26Br2Se (601.27): calcd. C 55.93, H
4.36; found C 55.87, H 4.475.
˜
1408 (br., w), 1275 (m), 1247 (s), 834 (br., s), 758 (s) cm–1. MS (EI,
= 70 eV): m/z (%) = 482 (88) [M]+, 467 (100), 293 (29), 227 (24),
169 (21), 139 (16). HRMS (EI, 70 eV): calcd. for C14H18Br2SeSi2
479.84735; found 479.847476.
3,3Ј-(3,4-Dibromoselenophene-2,5-diyl)bis(prop-2-yne-3,1-diyl)-
diacetate (3j): Propargyl acetate (2.4 equiv., 0.18 mL) was added to
a solution of PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI (2 mg, 2 mol-
%), HP(tBu)3BF4 (9 mg, 6 mol-%), and 2 in dioxane (2 mL) and
HN(iPr)2 (0.5 mL). The reaction mixture was stirred for 20 h at
room temperature. Purification resulted in 3j (135 mg, 71%) as a
brown solid, m.p. 112–113 °C. 1H NMR (300 MHz, CDCl3): δ =
3,4-Dibromo-2,5-di(dec-1-ynyl)selenophene (3e): 1-Decyne
(2.4 equiv., 0.07 mL) was added to a solution of Pd(PPh3)4 (5 mol-
%, 23 mg), CuI (10 mol-%, 15.2 mg), and 2 (0.5 mmol, 224 mg) in
THF (5 mL) and NEt3 (5 mL). The solution was stirred for 4 h at
80 °C. Purification gave 3e as (243 mg, 87%) a brown liquid. 1H
NMR (300 MHz, CDCl3): δ = 0.88–0.93 (m, 6 H, CH3), 1.27–1.36 2.14 (s, 3 H, CH3), 4.95 (s, 2 H, CH2). 13C NMR (75 MHz, CDCl3):
(m, 20 H, CH2), 1.44–1.49 (m, 4 H, CH2), 1.57–1.69 (m, 4 H, CH2), δ = 20.7 (CH3), 52.6 (CH2), 79.7 (CϵC), 94.7 (CϵC), 120.5,
3
2.48 (t, J = 6.9 Hz, 4 H, CH2). 13C NMR (75 MHz, CDCl3): δ =
(CHetar), 123.6 (CHetar), 170.0 (C=O). IR (ATR): ν = 3441 (w), 2961
˜
2004
www.eurjoc.org
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 2000–2007

Synthesis of Alkynylated Selenophenes
(w), 2941 (w), 2709 (w), 2464 (w), 2225 (w), 1741 (s), 1722 (s), 1513
CDCl3): δ = 7.01–7.08 (m, 8 H, Ar), 7.49–7.55 (m, 8 H, Ar). 13C
5
(m), 1449 (m), 1378 (m), 1361 (m), 1220 (br., s), 1024 (br., s) cm–1. NMR (75 MHz, CDCl3): δ = 83.8 (d, J = 1.4 Hz, CϵC), 84.6 (d,
MS (EI, = 70 eV): m/z (%) = 482 (29) [M]+, 439 (37), 422 (20), 380
(37), 299 (20), 123 (14). C14H10Br2O4Se (480.99): calcd. C 34.98, H 21.9 Hz, CH), 116.3 (d, J = 21.9 Hz, CH), 118.9 (d, J = 3.9 Hz,
2.28; found C 35.12, H 2.341.
5J = 1.4 Hz, CϵC), 94.2 (CϵC), 100.0 (CϵC), 116.1 (d, 2J =
2
4
4
C), 119.4 (d, J = 3.9 Hz, C), 129.4 (CHetar), 130.2 (CHetar), 133.8
(d, 3J = 8.4 Hz, CH), 133.9 (d, 3J = 8.4 Hz, CH), 163.1 (d, 1J =
General Procedure for Synthesis of 4a–d: The appropriate alkyne
(6.0 equiv.) was added to a solution of PdCl2(CH3CN)2 (4 mg,
3 mol-%), CuI (2 mg, 2 mol-%), dicyclohexyl(2Ј,4Ј,6Ј-triisoprop-
ylbiphenyl-2-yl)phosphane (14 mg, 6 mol-%) or HP(tBu)3BF4
(9 mg, 6 mol-%), and 2 (0.5 mmol, 224 mg) in dioxane (5 mL) and
HN(iPr)2 (1 mL). The reaction mixture was stirred for 20 h at room
temperature. After the reaction time was over, it was quenched with
brine. The aqueous phase was extracted with CH2Cl2 (3ϫ). The
combined organic extracts were dried with Na2SO4 and filtered,
and the solution was concentrated. The residue was purified by
column chromatography (hexane/dichloromethane = 10:1) to ob-
tain 4a–d.
251.0 Hz, C), 163.3 (d, 1J = 250.9 Hz, C). IR (ATR): ν = 3108 (w),
˜
3058 (w), 2853 (w), 2192 (w), 1886 (w), 1600 (m), 1518 (s), 1228
(br., s), 1151 (s), 1091 (m), 824 (s), 522 (s) cm–1. MS (EI, = 70 eV):
m/z (%) = 604 (100) [M]+, 522 (17), 429 (6), 302 (7), 262 (18), 44
(32). HRMS (EI, 70 eV): calcd. for C36H16F4Se 604.03479; found
604.036296.
2,3,4,5-Tetrakis(m-tolylethynyl)selenophene (4d): m-Tolylacetylene
(6.0 equiv., 0.384 mL) was added to a solution of PdCl2(CH3CN)2
(4 mg, 3 mol-%), CuI (2 mg, 2 mol-%), HP(tBu)3BF4 (9 mg, 6 mol-
%), and 2 in dioxane (5 mL) and HN(iPr)2 (1 mL). The reaction
mixture was stirred for 20 h at room temperature. Quenching with
brine, extraction with CH2Cl2, and purification by column
chromatography resulted in 4d (254 mg, 87%) as a red solid, m.p.
2,3,4,5-Tetrakis(phenylethynyl)selenophene (4a): Phenylacetylene
(6.0 equiv., 0.330 mL) was added to a solution of PdCl2(CH3CN)2
(4 mg, 3 mol-%), CuI (2 mg, 2 mol-%), dicyclohexyl(2Ј,4Ј,6Ј-triiso-
propylbiphenyl-2-yl)phosphane (14 mg, 6 mol-%), and 2 in dioxane
(5 mL) and HN(iPr)2 (1 mL). The reaction mixture was stirred for
20 h at room temperature. Quenching with brine, extraction with
CH2Cl2, and purification by column chromatography resulted in
4a (79 mg, 34 %) as a yellow solid, m.p. 138–139 °C. 1H NMR
(300 MHz, CDCl3): δ = 7.33–7.38 (m, 12 H, Ph), 7.53–7.62 (m, 8
H, Ph). 13C NMR (75 MHz, CDCl3): δ = 84.1, 84.8, 95.1, 100.8
(CϵC), 122.6, 123.1 (CAr/Hetar), 128.4, 128.5, 128.6, 129.0 (CH),
1
99–100 °C. H NMR (300 MHz, CDCl3): δ = 2.34 (s, 6 H, CH3),
2.36 (s, 6 H, CH3), 7.16–7.28 (m, 8 H, Ar), 7.37–7.45 (m, 8 H, Ar).
13C NMR (75 MHz, CDCl3): δ = 55.3, 55.4 (CH3), 72.9, 81.2, 82.3,
100.9 (CϵC), 113.9 (CAr/Hetar), 114.1, 114.2 (CH), 118.8, 123.7
(CAr/Hetar), 133.2, 134.0 (CH), 160.2, 160.4 (CAr/Hetar). IR (ATR):
ν = 3091 (w), 2029 (w), 2918 (m), 2854 (w), 2730 (w), 2184 (w),
˜
1598 (m), 1578 (m), 1507 (m), 1473 (m), 776 (s), 684 (s) cm–1. MS
(EI, = 70 eV): m/z (%) = 588 (100) [M]+, 477 (5), 401 (3), 237 (15),
200 (6), 149 (7), 129 (9), 111 (16). C40H28Se (587.61): calcd. C
81.76, H 4.80; found C 81.45, H 4.85.
129.2, 130.2 (CAr/Hetar), 131.5, 131.8 (CH). IR (ATR): ν = 3137
˜
(w), 3077 (w), 3052 (w), 3017 (w), 2923 (w), 2852 (w), 2185 (w), 2,3,4-Tribromo-5-(phenylethynyl)selenophene (5a): Phenylacetylene
1596 (m), 1516 (w), 1490 (m), 1440 (m), 747 (s), 681 (s) cm–1. MS (1.2 equiv., 0.07 mL) was added to a solution of Pd(PPh3)4 (5 mol-
(EI, = 70 eV): m/z (%) = 532 (100) [M]+, 450 (21), 432 (4), 266 (10),
224 (19), 44 (9). C36H20Se (531.50): calcd. C 81.35, H 3.79; found
C 81.16, H 3.948.
%, 23 mg), CuI (10 mol-%, 15.2 mg), and 2 (0.5 mmol, 224 mg) in
THF (5 mL) and NEt3 (5 mL). The solution was stirred for 4 h at
80 °C. The reaction was quenched with brine. The aqueous phase
was extracted with CH2Cl2 (3ϫ). The combined organic extracts
were dried with Na2SO4 and filtered, and the solution was concen-
trated. The residue was purified by column chromatography (hept-
ane) to obtain 5a (87 mg, 38%) as an unstable yellow solid, m.p.
97–98 °C. 1H NMR (300 MHz, CDCl3): δ = 7.35–7.39 (m, 3 H,
Ph), 7.53–7.56 (m, 2 H, Ph). 13C NMR (75 MHz, CDCl3): δ = 82.7,
100.7 (CϵC), 113.0, 118.5, 118.8, 122.0, 127.6 (CAr/Hetar), 128.5,
2,3,4,5-Tetrakis[(4-tert-butylphenyl)ethynyl]selenophene (4b): (4-
tert-Butylphenyl)acetylene (6.0 equiv., 475 mg) was added to a
solution of PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI (2 mg, 2 mol-%),
dicyclohexyl(2Ј,4Ј,6Ј-triisopropylbiphenyl-2-yl)phosphane (14 mg,
6 mol-%), and 2 in dioxane (5 mL) and HN(iPr)2 (1 mL). The reac-
tion mixture was stirred for 14 h at 80 °C. Quenching with brine,
extraction with CH2Cl2, and purification by column chromatog-
raphy resulted in 4b (103 mg, 28%) as a red solid, m.p. 206–207 °C.
1H NMR (300 MHz, CDCl3): δ = 1.34 (s, 18 H, CH3), 1.34 (s, 18
129.3, 131.6 (CH). IR (ATR): ν = 3057 (w), 3034 (w), 3018 (w),
˜
2950 (w), 2918 (w), 2873 (w), 2848 (w), 1513 (m), 1430 (m), 1249
(m), 745 (s), 683 (s) cm–1. MS (EI, = 70 eV): m/z (%) = 467 (100)
[M]+, 389 (8), 229 (22), 183 (8), 149 (16), 112 (14). HRMS (EI,
70 eV): calcd. for C12H5Br3Se 465.71011; found 465.709024.
3
3
H, CH3), 7.37 (d, J = 2.3 Hz, 4 H, Ar), 7.40 (d, J = 2.4 Hz, 4 H,
Ar), 7.51 (d, 3J = 8.5 Hz, 4 H, Ar), 7.54 (d, 3J = 8.5 Hz, 4 H,
Ar). 13C NMR (75 MHz, CDCl3): δ = 31.2, 31.2 (CH3), 34.9, 34.9
[C(CH3)3], 83.7, 84.3, 95.1, 100.8 (CϵC), 119.7, 120.3 (CAr/Hetar), General Procedure for the Synthesis of 6a,b: The appropriates
125.4, 125.5 (CH), 128.8, 130.1 (CAr/Hetar), 131.3, 131.5 (CH), alkynes (1.2 equiv.) were added simultaneously to a solution of
151.8, 152.3 (CAr). IR (ATR): ν = 3083 (w), 3034 (w), 2957 (m),
PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI (2 mg, 2 mol-%), HP-
2902 (w), 2865 (w), 2188 (w), 1461 (m), 1406 (m), 1392 (w), 1266 (tBu)3BF4 (9 mg, 6 mol-%), and 2 (0.5 mmol, 224 mg) in dioxane
(m), 1106 (m), 1016 (m), 831 (s), 558 (s) cm–1. MS (EI, = 70 eV):
(2 mL) and HN(iPr)2 (0.5 mL). The reaction mixture was stirred
m/z (%) = 756 (38) [M]+, 741 (6), 669 (2), 363 (6), 207 (5), 91 (5), for 20 h at room temperature. After the reaction time was over, the
˜
60 (9). HRMS (EI, 70 eV): calcd. for C52H52Se 756.32287; found
756.323101.
reaction was quenched with brine. The aqueous phase was ex-
tracted with CH2Cl2 (3ϫ). The combined organic extracts were
dried with Na2SO4 and filtered, and the solution was concentrated.
The residue was purified by column chromatography (heptane) to
obtain 6a,b.
2,3,4,5-Tetrakis[(4-fluorophenyl)ethynyl]selenophene (4c): (4-
Fluorophenyl)acetylene (6.0 equiv., 0.360 mg) was added to a solu-
tion of PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI (2 mg, 2 mol-%),
HP(tBu)3BF4 (9 mg, 6 mol-%), and 2 in dioxane (5 mL) and 3,4-Dibromo-2-(phenylethynyl)-5-(m-tolylethynyl)selenophene (6a):
HN(iPr)2 (1 mL). The reaction mixture was stirred for 20 h at room Phenylacetylene (1.2 equiv., 0.07 mL) and m-tolylacetylene
temperature. Quenching with brine, extraction with CH2Cl2, and
purification by column chromatography resulted in 4c (110 mg,
37 %) as a yellow solid, m.p. 190–191 °C. 1H NMR (300 MHz,
(1.2 equiv., 0.08 mL) were added simultaneously to a solution of
PdCl2(CH3CN)2 (4 mg, 3 mol-%), CuI (2 mg, 2 mol-%), HP-
(tBu)3BF4 (9 mg, 6 mol-%), and 2 in dioxane (2 mL) and HN-
Eur. J. Org. Chem. 2013, 2000–2007
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2005

P. Ehlers, T. T. Dang, T. Patonay, A. Villinger, P. Langer
FULL PAPER
(iPr)2 (0.5 mL). The reaction mixture was stirred for 20 h at room
temperature. Purification resulted in 6a (168 mg, 67%) as a brown
solid that also contained a small amount of the symmetrical prod-
2,5-Bis(phenylethynyl)-3,4-bis(m-tolylethynyl)selenophene (7b): m-
Tolylacetylene (3.0 equiv., 0.09 mL) was added to a solution of
PdCl2(CH3CN)2 (4 mg, 6 mol-%), CuI (2 mg, 4 mol-%), HP-
(tBu)3BF4 (9 mg, 6 mol-%), and 3a (0.25 mmol, 112 mg) in dioxane
1
uct, m.p. 122–123 °C. H NMR (300 MHz, CDCl3): δ = 2.35 (s, 3
H, CH3), 7.16–7.27 (m, 2 H, Ph/Ar), 7.34–7.37 (m, 5 H, Ph/Ar), (2 mL) and HN(iPr)2 (0.5 mL). The reaction mixture was stirred for
7.53–7.56 (m, 2 H, Ph/Ar). 13C NMR (75 MHz, CDCl3): δ = 21.2
(CH3), 83.1, 83.1, 83.3, 83.3, 100.7, 100.8, 101.0, 101.1 (CϵC),
119.4, 119.4, 119.6, 119.6, 121.9, 121.9, 122.1, 122.1, 123.7, 123.9,
124.0 (CAr/Hetar), 128.4, 128.5, 128.7, 129.2, 130.2, 131.6, 132.1
20 h at room temperature. Quenching with brine, extraction with
CH2Cl2, and purification by column chromatography resulted in 7b
(83 mg, 60%) as a red solid, m.p. 109–111 °C. 1H NMR (300 MHz,
CDCl3): δ = 2.31 (s, 6 H, CH3), 7.13–7.25 (m, 4 H, Ph/Ar), 7.33–
7.36 (m, 6 H, Ph/Ar), 7.39–7.42 (m, 4 H, Ph/Ar), 7.54–7.57 (m, 4
(CH), 138.2 (CAr/Hetar). IR (ATR): ν = 3051 (w), 3017 (w), 2919
˜
(m), 2850 (w), 2197 (m), 1510 (m), 1440 (m), 1298 (br., m), 751 (s), H, Ph/Ar). 13C NMR (75 MHz, CDCl3): δ = 21.2 (CH3), 84.1, 84.5,
684 (s) cm–1. MS (EI, = 70 eV): m/z (%) = 504 (100) [M]+, 424 (1),
95.6, 100.7 (CϵC), 122.7, 123.0 (CPh/Ar), 128.3, 128.5, 128.8, 128.9,
344 (9), 264 (58), 252 (8), 132 (27). HRMS (EI, 70 eV): calcd. for 129.5 (CHPh/Ar), 130.4 (CPh/Ar), 131.6, 132.4 (CHPh/Ar), 138.0
C21H12Br2Se 501.84655; found 501.846370.
(CPh/Ar). IR (ATR): ν = 3054 (w), 3017 (w), 2945 (w), 2916 (w),
˜
2853 (w), 1595 (m), 1484 (m), 1440 (m), 776 (s), 751 (s), 685 (s)
cm–1. MS (EI, = 70 eV): m/z (%) = 560 (100) [M]+, 544 (4), 463 (6),
280 (7), 231 (6), 178 (6), 149 (6). HRMS (EI, 70 eV): calcd. for
C38H24Se 560.10377; found 560.107147.
3,4-Dibromo-2-[(4-tert-butylphenyl)ethynyl]-5-(m-tolylethynyl)-
selenophene (6b):[1] (4-tert-Butylphenyl)acetylene (1.2 equiv.,
120 mg) and m-tolylacetylene (1.2 equiv., 0.08 mL) were added at
the same time to a solution of PdCl2(CH3CN)2 (4 mg, 3 mol-%),
CuI (2 mg, 2 mol-%), HP(tBu)3BF4 (9 mg, 6 mol-%), and 2 in diox-
ane (2 mL) and HN(iPr)2 (0.5 mL). The reaction mixture was
stirred for 20 h at room temperature. Purification resulted in 6b
(168 mg, 67 %) as a brown solid, m.p. 79–80 °C. 1H NMR
3,3Ј-[3,4-Bis(m-tolylethynyl)selenophene-2,5-diyl]bis(prop-2-yne-
3,1-diyl) Diacetate (7c): m-Tolylacetylene (3.0 equiv., 0.096 mL) was
added to a solution of PdCl2(CH3CN)2 (4 mg, 6 mol-%), CuI
(2 mg, 4 mol-%), HP(tBu)3 BF4 (9 mg, 6 mol-%), and 3j
(300 MHz, CDCl3): δ = 1.34 [s, 9 H, C(CH3)3], 2.37 (s, 3 H, CH3), (0.25 mmol, 120 mg) in dioxane (2 mL) and HN(iPr)2 (0.5 mL).
7.19–7.29 (m, 2 H, Ar), 7.38–7.41 (m, 4 H, Ar), 7.46–7.52 (m, 2 H, The reaction mixture was stirred for 20 h at room temperature.
Ar). 13C NMR (75 MHz, CDCl3): δ = 21.2 (CH3), 31.1 [C(CH3)3], Quenching with brine, extraction with CH2Cl2, and purification by
34.9 [C(CH3)3], 82.8, 82.8, 83.0, 83.0, 100.6, 100.7, 100.7, 100.8
(CϵC), 119.1, 119.1, 119.3, 119.4, 121.9, 123.7, 123.9, 124.0
column chromatography resulted in 7c (30 mg, 22%) as a red solid,
m.p. 82–84 °C. 1H NMR (300 MHz, CDCl3): δ = 2.16, 2.37 (s, 6
(CAr/Hetar), 125.4, 125.5, 128.4, 128.7, 130.1, 130.2, 131.4, 132.1, H, CH3), 5.02 (s, 4 H, CH2), 7.18–7.29 (m, 4 H, Ar), 7.41–7.43 (m,
132.2, 132.9 (CH), 138.2, 152.7, 152.7 (CAr/Hetar). IR (ATR): ν =
4 H, Ar). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.2 (CH3), 52.8
(CH2), 80.4, 83.9, 94.2, 95.5 (CϵC), 122.6 (CAr/Hetar), 128.3, 129.0,
129.7 (CH), 131.4 (CAr/Hetar), 132.5 (CH), 138.0 (CAr/Hetar), 170.1
˜
3083 (w), 3053 (w), 3033 (w), 2958 (s), 2903 (m), 2865 (m), 2196
(m), 1521 (m), 1266 (m), 832 (s), 780 (s), 687 (s), 559 (s) cm–1. MS
(EI, = 70 eV): m/z (%) = 560 (93) [M]+, 545 (57), 515 (13), 368 (11),
304 (15), 273 (83), 256 (100), 207 (14). HRMS (EI, 70 eV): calcd.
for C25H20Br2Se 557.90915; found 557.909427.
(C=O). IR (ATR): ν = 3021 (w), 2954 (w), 2921 (m), 2852 (m),
˜
2202 (w), 1740 (br., s), 1373 (br., m), 1211 (br., s), 1021 (br., s), 782
(m), 688 (m) cm–1. MS (EI, = 70 eV): m/z (%) = 552 (100) [M]+,
493 (5), 450 (25), 421 (13), 407 (9), 341 (11), 326 (13), 163 (4).
HRMS (ESI): calcd. for C32H24NaO4Se [M + Na]+ 575.07345;
found 547.07341.
General Procedure for the Synthesis of 7a–d: The appropriate alkyne
(3.0 equiv.) was added to a solution of PdCl2(CH3CN)2 (4 mg,
6 mol-%), CuI (2 mg, 4 mol-%), HP(tBu)3BF4 (9 mg, 6 mol-%), and
3 (0.25 mmol) in dioxane (2 mL) and HN(iPr)2 (0.5 mL). The reac-
tion mixture was stirred for 20 h at room temperature. After the
reaction time was over, the reaction was quenched with brine. The
aqueous phase was extracted with CH2Cl2 (3ϫ). The combined
organic extracts were dried with Na2SO4 and filtered, and the solu-
tion was concentrated. The residue was purified by column
chromatography to obtain 7a–d.
3,3Ј-[2,5-Bis(m-tolylethynyl)selenophene-3,4-diyl]bis(prop-2-yne-
3,1-diyl) Diacetate (7d): m-Tolylacetylene (3.0 equiv., 0.096 mL)
was added to a solution of PdCl2(CH3CN)2 (4 mg, 6 mol-%), CuI
(2 mg, 4 mol-%), HP(tBu)3 BF4 (9 mg, 6 mol-%), and 3b
(0.25 mmol, 129 mg) in dioxane (2 mL) and HN(iPr)2 (0.5 mL).
The reaction mixture was stirred for 20 h at room temperature.
Quenching with brine, extraction with CH2Cl2, and purification by
column chromatography resulted in 7d (109 mg, 82%) as a red so-
3,3Ј-[2,5-Bis(phenylethynyl)selenophene-3,4-diyl]bis(prop-2-yne-3,1-
diyl) Diacetate (7a): Propargyl acetate (3.0 equiv., 0.074 mL) was
added to a solution of PdCl2(CH3CN)2 (4 mg, 6 mol-%), CuI
(2 mg, 4 mol-%), HP(tBu)3 BF4 (9 mg, 6 mol-%), and 3a
(0.25 mmol, 112 mg) in dioxane (2 mL) and HN(iPr)2 (0.5 mL).
The reaction mixture was stirred for 20 h at room temperature.
Quenching with brine, extraction with CH2Cl2, and purification by
column chromatography resulted in 7a (83 mg, 60%) as a red solid,
m.p. 130–131 °C. 1H NMR (300 MHz, CDCl3): δ = 2.12 (s, 6 H,
CH3), 7.36 7.38 (m, 6 H, Ph), 7.55–7.58 (m, 4 H, Ph). 13C NMR
(75 MHz, CDCl3): δ = 20.8 (CH3), 52.8 (CH2), 80.9, 83.4, 88.5,
101.1 (CϵC), 122.4 (CPh/Hetar), 128.5 (CH), 128.8 (CPh/Hetar), 129.1
1
lid, m.p. 107–109 °C. H NMR (300 MHz, CDCl3): δ = 2.16, 2.36
(s, 6 H, CH3), 4.99 (s, 4 H, CH2), 7.17–7.28 (m, 4 H, Ar), 7.35–
7.38 (m, 4 H, Ar). 13C NMR (75 MHz, CDCl3): δ = 20.8, 21.2
(CH3), 52.8 (CH2), 81.0, 83.1, 88.4, 101.3 (CϵC), 122.2 (CAr/Hetar),
128.4 (CH), 128.7 (CAr/Hetar), 128.8, 130.1 (CH), 130.8 (CAr/Hetar),
132.2 (CH), 138.2 (CAr/Hetar), 170.2 (C=O). IR (ATR): ν = 3020
˜
(w), 2975 (w), 2945 (w), 2920 (w), 2854 (w), 2218 (w), 2189 (w),
1743 (s), 1425 (m), 1366 (m), 1212 (s) cm–1. MS (EI, = 70 eV): m/z
(%) = 552 (100) [M]+, 492 (6), 492 (6), 450 (28), 421 (14), 407 (11),
341 (13), 326 (17), 163 (6). HRMS (ESI): calcd. for C32H24NaO4Se
[M + Na]+ 575.07345; found 547.07317.
(CH), 130.8 (CPh/Hetar), 131.7 (CH), 170.2 (C=O). IR (ATR): ν = 3,4-Bis(4-methoxyphenyl)-2,5-bis(phenylethynyl)selenophene (8): (4-
˜
3065 (w), 3034 (w), 2977 (w), 2924 (w), 2852 (w), 2218 (w), 2192
Methoxyphenyl)boronic acid (3.0 equiv., 114 mg) was added to a
(m), 1745 (s), 1365 (m), 1267 (m), 1209 (s), 755 (s), 688 (s) cm–1. solution of Pd(OAc)2, dicyclohexyl(2Ј,4Ј,6Ј-triisopropylbiphenyl-2-
MS (EI, = 70 eV): m/z (%) = 524 (100) [M]+, 464 (9), 422 (37), 393
(44), 313 (76), 300 (9), 162 (14). HRMS (ESI): calcd. for
C30H20NaO4Se [M + Na]+ 547.04212; found 547.04168.
yl)phosphane (3.6 mg, 6 mol-%), K3PO4 (3.0 equiv., 160 mg), and
3a (0.25 mmol, 122 mg) in dioxane (1 mL) and water (0.1 mL). The
reaction was stirred for 8 h at 80 °C. After this time, the reaction
2006
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2013, 2000–2007

Synthesis of Alkynylated Selenophenes
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was quenched with brine and extracted with ethyl acetate, and the
crude material was purified by column chromatography. Product 8
1
(128 mg, 95%) was isolated as a yellow solid, m.p. 149–150 °C. H
3
NMR (300 MHz, CDCl3): δ = 3.79 (s, 6 H, OCH3), 6.80 (d, J =
3
8.8 Hz, 4 H, Ph/Ar), 7.18 (d, J = 8.9 Hz, 4 H, Ph/Ar), 7.28–7.30
(m, 6 H, Ph/Ar), 7.35–7.38 (m, 4 H, Ph/Ar). 13C NMR (75 MHz,
CDCl3): δ = 55.2 (OCH3), 85.6,97.0 (CϵC), 113.1 (CH), 123.1,
123.6 (CAr/Hetar), 128.3 (CH), 129.0 (CAr/Hetar), 131.2, 131.5 (CH),
147.2 (CAr), 158.7 (CAr). IR (ATR): ν = 3056 (w), 3004 (w), 2963
˜
[13] S. H. Abdel-Hafez, Russ. J. Org. Chem. 2005, 41, 396; Zh. Org.
Khim. 2005, 41, 406.
(w), 2929 (w), 2835 (w), 2536 (w), 1605 (m), 1504 (br., m), 1245 (s),
1174 (s), 1029 (s) cm–1. MS (EI, = 70 eV): m/z (%) = 544 (100)
[M]+, 512 (4), 469 (3), 376 (4), 272 (3), 187 (5), 69 (9). HRMS (EI,
70 eV): calcd. for C34H24O2Se 544.09360; found 544.094275.
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Biomol. Chem. 2011, 9, 6963; b) E. G. A. Notaras, N. T. Lucas,
M. G. Humphrey, A. C. Willis, A. D. Rae, Organometallics
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Glimsdal, M. Lindgren, C. Lopes, L. Boman, P. Norman, Mol.
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E. P. Levanova, G. G. Levkovskaja, Chem. Eur. J. 2009, 15,
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795.
3,4-Bis(phenylethynyl)-2,5-di(p-tolyl)selenophene (10): Phenylacet-
ylene (3.0 equiv., 0.08 mL) was added to
a solution of
PdCl2(CH3CN)2 (2 mg, 3 mol-%), CuI (1 mg, 2 mol-%), dicyclo-
hexyl(2Ј,4Ј,6Ј-triisopropylbiphenyl-2-yl)phosphane (7 mg, 6 mol-
%), and 9 (0.25 mmol, 117 mg) in dioxane (5 mL) and HN(iPr)2
(1.0 mL). The reaction mixture was stirred for 10 h at 80 °C.
Quenching with brine, extraction with CH2Cl2, and purification by
column chromatography resulted in 10 (30 mg, 24%) as a yellow
1
solid, m.p. 195–197 °C. H NMR (300 MHz, CDCl3): δ = 2.41 (s,
3
6 H, CH3), 7.26 (d, J = 8.1 Hz, 4 H, Ph/Ar), 7.31–7.34 (m, 6 H,
3
Ph/Ar), 7.50–7.53 (m, 4 H, Ph/Ar), 7.82 (d, J = 8.1 Hz, 4 H, Ph/
Ar). 13C NMR (75 MHz, CDCl3): δ = 21.4 (CH3), 86.7, 92.7
(CϵC), 122.7, 123.6 (CAr/Hetar), 128.1, 128.4, 129.4, 131.5
(CHAr/Ph), 132.6, 138.5, 149.9 (CAr/Hetar). IR (ATR): ν = 3055 (w),
˜
3018 (w), 2918 (w), 2852 (w), 1596 (w), 1499 (m), 1458 (m), 1440
(m), 818 (m), 749 (s), 684 (s) cm–1. MS (EI, = 70 eV): m/z (%) =
512 (100) [M]+, 494 (5), 432 (24), 416 (13), 339 (5), 200 (15). HRMS
(EI, 70 eV): calcd. for C34H24Se 512.104981; found 512.104981.
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Supporting Information (see footnote on the first page of this arti-
cle): Copies of NMR spectra.
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Acknowledgments
[18] M. Hussain, R. A. Khera, T. H. Nguyen, P. Langer, Org. Bio-
mol. Chem. 2011, 9, 370.
Financial support by the State of Vietnam (MOET scholarship to
T. T. D.) and by the Federate State of Mecklenburg-Vorpommern is
gratefully acknowledged. Financial support by the European Social
Fund (EFRE program) is also acknowledged. The work was also
supported by theEuropean Social Fund, European Regional Devel-
opment Fund, New Hungary Development Plan (project TÁMOP-
4.2.1/B-09/KONV-2010-007).
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Received: October 29, 2012
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Published Online: February 8, 2013
Eur. J. Org. Chem. 2013, 2000–2007
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2007