Thiophene-based donor-acceptor co-oligomers by copper-catalyzed 1,3-dipolar cycloaddition

Article abstract of DOI:10.3762/bjoc.8.76

Herein we present a three-component one-pot procedure to synthesize co-oligomers of a donor-acceptor-donor type, in which thiophene moieties work as donor and 1,2,3-triazoles as acceptor units. In this respect, terminally ethynylated (oligo)thiophenes were coupled to halogenated (oligo)thiophenes in the presence of sodium azide and a copper catalyst. Optoelectronic properties of various thiophene-1,2,3-triazole co-oligomers were investigated by UV-vis spectroscopy and cyclic voltammetry. Several co-oligomers were electropolymerized to the corresponding conjugated polymers.

Full text of DOI:10.3762/bjoc.8.76

Thiophene-based donor–acceptor co-oligomers by
copper-catalyzed 1,3-dipolar cycloaddition
Stefanie Potratz, Amaresh Mishra and Peter Bäuerle*§
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2012, 8, 683–692.
University of Ulm, Institute of Organic Chemistry II and Advanced
Materials, Albert-Einstein-Allee 11, 89081 Ulm, Germany
doi:10.3762/bjoc.8.76
Received: 17 January 2012
Accepted: 17 April 2012
Published: 03 May 2012
Email:
Peter Bäuerle* - peter.baeuerle@uni-ulm.de
* Corresponding author
Associate Editor: H. Ritter
§ Tel: 0049-731-50-22850; Fax: 0049-731-50-22840
© 2012 Potratz et al; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
acetylene; azide; click chemistry; thiophene; triazole
Abstract
Herein we present a three-component one-pot procedure to synthesize co-oligomers of a donor–acceptor–donor type, in which thio-
phene moieties work as donor and 1,2,3-triazoles as acceptor units. In this respect, terminally ethynylated (oligo)thiophenes were
coupled to halogenated (oligo)thiophenes in the presence of sodium azide and a copper catalyst. Optoelectronic properties of
various thiophene-1,2,3-triazole co-oligomers were investigated by UV–vis spectroscopy and cyclic voltammetry. Several
co-oligomers were electropolymerized to the corresponding conjugated polymers.
Introduction
Oligo- and polythiophenes are among the most extensively azides (CuAAC), to regioselectively yield 1,4-disubstituted
investigated organic semiconducting materials used in organic 1H-1,2,3-triazoles [11,12]. In the meanwhile, this type of click
electronics [1-3]. In this respect, various oligomers have been reaction has become very popular and reached high signifi-
developed by using metal-catalyzed Suzuki-, Stille-, Sono- cance in materials synthesis, because high yields and easy to
gashira-, and Kumada-type cross-coupling reactions [4-9]. On purify products are typically obtained [13,14]. The click chem-
the other hand, the so-called “click chemistry”, originally istry approach was successfully employed to synthesize various
reported by Sharpless and co-workers in 2001, has played a oligomers [15-17], catenanes and rotaxanes [18], dendrimers
significant role as a versatile strategy for the rapid and efficient [11,19,20], and polymers [21-23], and was used for DNA
assembly of a pair of functional molecular building blocks labelling [24,25], sensors [26,27], and metal chelates [28-30],
under mild reaction conditions [10]. It guarantees reliable syn- due to the mild reaction conditions and compatibility with a
thesis of the desired products in high yield and purity. Click variety of functional groups. However, the electronic conjuga-
reactions generally involve a Cu(I)-catalyzed version of the tion through the resulting 1,2,3-triazole rings is weak due to
Huisgen 1,3-dipolar cycloaddition of terminal acetylenes and poor electronic communication between the chromophores [21-
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Beilstein J. Org. Chem. 2012, 8, 683–692.
23,31]. It has also been shown that a 1,2,3-triazole can act as a We first used the Fokin protocol [34], which worked well for
strong σ-electron donor [26] or as a weak π-electron acceptor phenyl halides and in which 1.2 equiv of sodium azide,
[15].
10 mol % of cupric sulfate, 10 mol % sodium ascorbate, which
reduces Cu(II) to Cu(I), 10 mol % sodium carbonate and
In this study, we aimed at the combination of electron-rich 20 mol % L-proline as ligand were reacted in the solvent system
(oligo)thiophenes as donors and electron-deficient 1,2,3-tria- DMSO–water at 60 °C. The co-oligomeric product 5 was
zole rings as acceptors to conveniently build up novel obtained in only 10% yield (Table 1, entry 1). When the stabi-
donor–acceptor co-oligomeric and copolymeric materials by lizing ligand was changed to N,N’-dimethylethylenediamine
click chemistry. Thereby, the inherent instability of 2-azidothio- (DMEDA) according to Liang et al. [32] the yield of 1,4-
phene was a problem.
di(thien-2-yl)-1,2,3-triazole (5) was increased to 17% (entry 2).
Careful choice of solvent mixture and temperature finally raised
the yield of 5 to 59% when ethanol–water (7:3) at 50 °C was
Results and discussion
In 2005, Liang et al. [32] described a mild, copper-catalyzed used (entry 4). Lower temperatures gave an incomplete conver-
method to synthesize aromatic azides from halogenated arenes sion of 2-iodothiophene (3), whereas at 95 °C the 2-azidothio-
and sodium azide. We have now transferred this method to the phene eventually decomposed. Therefore, we found that a
synthesis of 3-azidothiophene (2) from 3-iodothiophene (1) in temperature of 50 °C was a good compromise between the re-
excellent yield, which in the following was used for further activity of the halogenated thiophene in the nucleophilic substi-
click reactions to form novel thienyl-1,2,3-triazole co-oligomers tution to 2-azidothiophene, and the stability of the in situ
(Scheme 1). In contrast, 2-azidothiophene could not be obtained formed azido derivative.
by this protocol, because it is inherently instable. This finding
corresponds to the observations of Zanirato et al. that,
Table 1: Variation of solvent mixture and temperature in Cu(I)-
depending on the nature of the substituents, 5-substituted
2-azidothiophenes are more or less instable at elevated tempera-
tures [33].
catalyzed cycloaddition reactions of 2-iodothiophene (3) and
2-ethynylthiophene (4) to form co-oligomer 5.
entry ligand
solvent
T [°C] yield [%]
1
2
3
4
5
6
L-proline DMSO–water (9:1)
DMEDA DMSO–water (9:1)
60
50
10
17
28
59
39
16
DMEDA tert-butanol–water (2:1) 50
DMEDA ethanol–water (7:3)
DMEDA ethanol–water (7:3)
DMEDA ethanol–water (7:3)
50
20
95
Scheme 1: Synthesis of 3-azidothiophene 2.
Under the optimized reaction conditions for the preparation of
In order to overcome this inherent problem, we used a one-pot, di(thien-2-yl)-1,2,3-triazole 5 (2 equiv NaN3, 10 mol %
two-step sequence, whereby an organic azide was generated in copper(I) iodide, 10 mol % sodium ascorbate, 20 mol %
situ from a corresponding halide and immediately consumed in DMEDA, ethanol–water (7:3), 50 °C for 15 h, entry 4) a series
a reaction with copper acetylide [34-36]. Thus, as a model, we of conjugated benzene- and thiophene-1,2,3-triazole
optimized the reaction of 2-halogenothiophene 3 and co-oligomers was synthesized in good to excellent yields
2-ethynylthiophene (4) in the presence of sodium azide and a (Table 2). By systematic variation of the halogenated and the
copper(I) catalyst to yield co-oligomer 1,4-di(thien-2-yl)-1,2,3- ethynylated reagent, general trends could be deduced: (a)
triazole (5) (Scheme 2).
Iodides react better than bromides (5, 6, 8, (9), 10); (b) Due to
Scheme 2: One-pot, two-step procedure to give a dithienyl-1,2,3-triazole co-oligomer 5. See Table 1 for detailed conditions.
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Beilstein J. Org. Chem. 2012, 8, 683–692.
Table 2: Synthesis of 1,4-disubstituted 1,2,3-triazoles from corresponding halides (1 equiv), terminal acetylenes (1 equiv) and sodium azide (2 equiv)
in the presence of copper(I) iodide (10 mol %), sodium ascorbate (10 mol %) and N,N’-dimethylethylenediamine (DMEDA, 20 mol %) in ethanol–water
(7:3) at 50 °C for 15 h. The yields are for pure compounds and are averages of two runs.
product
yield [%]
(halide)
product
yield [%]
(halide)
product
yield [%]
(halide)
87 (I)
42 (Br)
99 (I)a
67 (I)
60 (Br)
25 (I)
62 (I)b
99 (Br)a,b
5
17
18
6
7
90 (I)
61 (I)
0 (I)
12
83 (I)
62 (Br)
67 (I)
33 (I)
13
14
8
9
44 (I)
47 (I)
53 (Br)
19
88 (I)
44 (I)
45 (Br)
72 (I)c
15
16
10
83 (I)
99 (I)
10 (I)
11
20
aReaction in DMSO–water (9:1); breaction at 95 °C; creaction at rt.
the higher stability of 3- versus 2-azidothiophenes, 3-halo- to 15 was observed. The yield was increased with decreasing
genated thiophenes give higher yields than 2-halogenated thio- temperature. Electron-withdrawing ester groups showed an
phenes, 2-substituted benzenes higher yields than thiophenes, opposite tendency. Due to the lower nucleophilicity of ethyl
and thiophenes higher yields than bithiophenes.
5-iodothiophene-2-carboxylate, the conversion to 17 rose with
increasing temperature.
As expected, 3-halogenothiophenes gave higher yields than
2-halogenothiophenes (e.g., 8 and 9), because of the higher Substituents in the 3-position of 2-iodothiophenes gave low or
nucleophilicity in azide formation. Additionally, 3-azidothio- no conversion to 16 and 18, respectively, because of steric
phenes are much more stable than 2-azidothiophenes [37]. In hindrance in the copper-catalyzed azide formation. Twofold
the series of halides, benzenes gave higher yields than mono- reactions were also investigated under the optimized reaction
and bithiophenes; the lowest conversion was observed for the conditions. 1,4-Dihalogenobenzene was reacted with
branched terthiophene to form co-oligomer 19, which is a result 2-ethynylthiophene in excellent yields (Scheme 3). 1,4-
of the instability of the intermediate azide. The electron- Diiodobenzene gave the desired product 21 in 99% yield at
donating methyl group in the 5-position of the thiophene ring 50 °C, whereas 1,4-dibromobenzene was disubstituted at 95 °C
destabilizes the corresponding azide, therefore low conversion in 98% yield.
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Beilstein J. Org. Chem. 2012, 8, 683–692.
UV–vis absorption spectra of co-oligomers 5, 6 and 10–14
revealed absorption bands of the individual subunits (Figure 1,
Table 3). Thus, for triazole 5 an absorption band at 279 nm was
observed, which is rather comparable to the absorption of
2-vinylthiophene (276 nm in ethanol) [38]. The second absorp-
tion band at 256 nm was assigned to the thiophene ring at-
tached to the 1-position of the triazole. The evidence for
intramolecular charge-transfer (ICT) [39] in 5 was investigated
in several solvents with different dielectric constants: n-hexane
(ε = 1.9), THF (ε = 7.6), methanol (ε = 32.6), and acetonitrile
(ε = 37.5). Typically, no ICT was found in the described thio-
phene–triazole co-oligomers, but aggregate formation was
observed in THF and n-hexane due to low solubility. For
derivative 14 an absorption maximum at 353 nm was observed,
which is red-shifted in comparison to that of 12 (λmax =
337 nm) and 13 (λmax = 339 nm). This band is not ascribed to
individual bithienyl subunits, but to a weak conjugation through
the triazole ring, caused by the donor–acceptor–donor system.
Maarseveen et al. recently published synthesis and optical prop-
Scheme 3: Synthesis of 1,4-bis[4-(thiophen-2-yl)-1H-1,2,3-triazol-1-yl]-
benzene 21.
Figure 1: UV–vis spectra of 5, 10 and 11 (a) and 12–14 (b) in dichloromethane ([c] = 5 × 10−5 M) at room temperature.
Table 3: Spectroscopic and electrochemical characterization of 5, 6 and 10–14.
λabs [nm]a
λemmax [nm]
Φ [%]b
Stokes shift [cm−1]c
E0ox [V]d
5
250, 256, 279
250
1.15
1.45
1.13
1.23
0.71
0.89
0.69
6
10
11
12
13
14
248, 256, 279
230, 256
244, 337
403
414
424
6
4 860
5 344
4 744
256, 273, 339
240, 353
10
14
aMaxima in italics (5 × 10−5 M in dichloromethane); bquantum yields determined with respect to DPA [41]; cStokes shift is given for the 0→0* tran-
sition (Δν = νabsmax – νemmax), dirreversible redox process, E0ox determined at I0 = 0.855 × Ip [42].
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Beilstein J. Org. Chem. 2012, 8, 683–692.
erties of 1,2,3-triazole containing co-polymers, suggesting that
triazole rings interrupt conjugation and therefore no interaction
of the various moieties of the polymer was observable [21].
Fluorescence spectra (10−6 M for 12 and 13, 5 × 10−7 M for 14
in dichloromethane, Table 3) of investigated compounds 12–14
showed structured bands due to vibronic splitting. The red-shift
of the emission maximum of 14 in comparison to 12 and 13
confirmed the facts assumed from UV–vis spectra that there
should be weak electronic communication in the oligomers
going through the 1,2,3-triazole ring. Fluorescence quantum
yields of 6 to 14% were determined which are rather high for
bithiophenes (1.8%) [40] and increased with increasing molec-
ular size and conjugation. Obviously, the 1,2,3-triazole ring
stabilizes the excited state by decreasing the probability of non-
radiative deactivation.
Figure 2: HOMO–LUMO energy level diagram for thiophene–triazole
co-oligomers 5, 6, 10–14.
Comparable to the optical properties, cyclic voltammetry of 5,
6, and 10–14 revealed redox transitions of the individual thio- phene unit in 12 and a quaterthiophene in 13. Electrochemical
phene moieties (Table 3). Thus, cyclic voltammograms (CV) of polymerization of 14 performed on a platinum working elec-
5 and 10 (5 × 10−3 M in dichloromethane/tetrabutylammonium trode in the range of −0.9 to 0.8 V versus Fc/Fc+ within 30
hexafluorophosphate (TBAPF6, 0.1 M, 100 mV s−1) showed cycles is displayed in Figure 3 (monomer 14: red, polymeriza-
characteristic oxidation waves of the 2-vinylthiophene subunit tion: gray, polymer film: blue). Because of similar oxidation
at 1.15 V and 1.13 V vs Fc/Fc+, respectively. For co-oligomer potentials for both bithienyl subunits in 14 the formation of
11, the oxidation potential was significantly higher (1.23 V) and higher co-oligomers and co-polymers can be expected and the
indicates formation of a radical cation localized on the thio- oxidation onset was located at −0.17 V. Therefore, comparable
phene subunits. In the negative regime, no reduction wave for electronic structures in the oligo- and polymers are responsible
the 1,2,3-triazole unit could be observed.
for this redox behavior.
From the optoelectronic data we deduced a HOMO–LUMO
energy level diagram including band gaps for the novel
donor–acceptor materials 5, 6 and 10–14 (Figure 2). HOMO
values were taken from the onset of oxidation and the internal
reference Fc/Fc+ was set to −5.1 eV versus vacuum. The
LUMO values were calculated by taking the optical band gaps
into account, which were taken from the absorption onset at the
lowest energy band. As a trend it can be seen that 3-thienyl
derivative 11 has the largest band gap (4.04 eV), because the
thiophenes are linked to the triazole by unfavorable β-connec-
tions. The gap successively decreases the more extended the
conjugated π-system is and approaches 3.11 eV for α-connected
bithienyl derivative 14.
Oxidative oligo- and polymerization of derivatives 12–14 was
carried out by potentiodynamic cycling in the appropriate
potential range. The films, which were deposited on the
platinum working electrode within 30 cycles, were investigated
in monomer-free dichloromethane solution. The CVs indicated
Figure 3: Cyclic voltammogram of bithienyl-triazole 14 in
dichloromethane/TBAPF6 (0.1 M) versus Fc/Fc+ at 100 mV s−1 (red:
monomer 14, gray: during polymerization, blue: polymer film).
that only dimers of 12 and 13 were formed, which showed Conclusion
quasi-reversible oxidation waves at 0.28 V and 0.68 V versus In summary, a series of novel thiophene-1,2,3-triazole
Fc/Fc+, respectively, corresponding to a divinyl-quaterthio- co-oligomers was synthesized in good to excellent yields by a
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Beilstein J. Org. Chem. 2012, 8, 683–692.
three-component two-step procedure using copper-catalyzed secondary electrode. All potentials were internally referenced to
[3 + 2]-Huisgen cycloaddition reactions. Spectroscopic and the ferrocene/ferricenium couple. For the measurements, the
redox properties of selected donor–acceptor–donor derivatives electroactive species were used in freshly distilled and degassed
were investigated, in which thiophene units act as donors and dichloromethane and 0.1 M tetrabutylammonium hexafluo-
triazoles as acceptors. As a general result we find that weak rophosphate (TBAPF6, Fluka), which was twice recrystallized
electronic conjugation through the 1,2,3-triazole ring is opera- from ethanol and dried under vacuum prior to use. 5'-Iodo-5,5''-
tive.
bis(trimethylsilyl)-[2,2':3',2''terthiophene] and 2-[5,5"-
bis(trimethylsilyl)-[2,2':3',2"-terthien]-5'-yl]ethynyl-1-trimethyl-
silane were synthesized according to the literature [44].
Experimental
General information
All reactions were carried out under an inert atmosphere of 3-Azidothiophene (2): In a mixture of ethanol (2.8 mL) and
argon. All chemicals were used as received without further water (1.2 mL) 3-iodothiophene (1, 0.22 mL, 2 mmol),
purification unless otherwise specified. Thin-layer chromatog- copper(I) iodide (38 mg, 0.2 mmol), sodium ascorbate (20 mg,
raphy (TLC) was carried out on silica gel 60 F254 aluminium 0.1 mmol), sodium azide (0.26 g, 4 mmol), and DMEDA (0.03
plates (Merck). Developed plates were dried and examined mL, 0.3 mmol) were dissolved and heated under refluxed under
under a UV lamp. Preparative-column chromatography was argon until TLC (silica/DCM) showed complete consumption
carried out on glass columns of different diameters packed with of the starting material. After five hours the cooled brown mix-
silica gel, Merck 60 (40–63 µm). Gas chromatography (GC) ture was diluted with water (10 mL) and ethyl acetate (10 mL).
was carried out using a Varian CP-3800 gas chromatograph. The aqueous phase was extracted with ethyl acetate (2 times,
Helium 5.0 was used as the carrier gas; signals were examined 10 mL). After the organic phases were washed with brine
by a flame-ionization detector (FID). Gas-chromatog- (15 mL) they were dried over sodium sulfate and evaporated to
raphy–mass-spectrometry (GC–MS) measurements were dryness in vacuum at room temperature. Because of the insta-
executed with a Varian 3800. Helium 5.0 was used as the bility of the product on silica it was used without further purifi-
carrier gas; mass spectra were recorded on a Varian Saturn cation. The NMR data was consistent with literature data [45].
2000. Ions were generated by electron impact (EI). Melting 1H NMR (400 MHz, CDCl3) δ 6.79 (dd, J = 1.5 and 3.2 Hz,
points were determined in a Büchi B-545 apparatus and are 1H), 6.82 (dd, J = 1.4 and 5.2 Hz, 1H), 7.30 (dd, J = 3.2 and 5.1
uncorrected. NMR spectra were recorded in CDCl3, DMSO-d6 Hz, 1H).
or THF-d8 on a Bruker AMX 400 at 400 MHz (1H nuclei) and
General procedure for the synthesis of 1,4-
100 MHz (13C nuclei), respectively. Chemical shifts are
denoted in δ units (ppm) and are referenced to the solvent signal disubstituted 1H-1,2,3-triazoles
(7.26 ppm for CDCl3, 2.50 ppm for DMSO-d6 and 1.73 for Halide (1 equiv) and terminal acetylene (1 equiv) were
THF-d8). The splitting patterns are designated as follows: s dissolved in an ethanol/water mixture (4 mL, 7:3). After the
(singlet), d (doublet), t (triplet), m (multiplet). Mass spectra addition of sodium azide (2 equiv), sodium ascorbate
were measured at Finnigan MAT, SSQ 7000 by CI and Bruker (10 mol %), N,N’-dimethylethylenediamine (DMEDA,
Daltonics REFLEX III by MALDI-TOF. Elemental analysis for 20 mol %) and copper(I) iodide (10 mol %), the mixture was
C, H and N were determined at Elementar Vario EL and for S at stirred in a closed Schlenk tube at 50 °C for about 15 hours. The
Carlo Erba 1104. High-resolution mass spectra were measured cooled mixture was poured into 50 mL ice–water. If the prod-
on a micrOTOF-Q 43 with electron spray ionization (ESI) and uct precipitated (method A) it was filtered off and washed with
atmospheric-pressure chemical ionization (APCI). UV–vis NH4OH (25 %) and water. The dried product was purified by
spectra were taken on a Perkin-Elmer Lambda 19 in 1 cm column chromatography. The non-precipitating products
cuvettes. Fluorescence spectra were measured with a Perkin- (method B) were treated with 10 mL NH4OH (25 %). The
Elmer LS 55 in 1 cm cuvettes. Fluorescence quantum yields aqueous solution was washed three times with 50 mL ethyl
were determined with respect to 9,10-diphenylanthracene acetate. After the organic phase was dried over sodium sulfate,
(DPA, Φ = 0.9 in dichloromethane) [43]. Cyclic voltammetry the crude product was concentrated at the rotary evaporator and
experiments were performed with a computer-controlled EG&G purified on silica.
PAR 273 potentiostat in a three-electrode single-compartment
cell (2 mL). The platinum working electrode consisted of a 1,4-Di(thien-2-yl)-1H-1,2,3-triazole (5): 2-Iodothiophene
platinum wire sealed in a soft glass tube with a surface area of A (0.11 mL, 1 mmol) or 2-bromothiophene (0.10 mL, 1 mmol),
= 0.785 mm2, which was polished down to 0.5 µm with Buehler 2-ethynylthiophene (0.11 mg, 1 mmol), sodium azide (130 mg,
polishing paste prior to use. The counter electrode consisted of 2 mmol), copper(I) iodide (19 mg, 0.1 mmol), sodium ascor-
a platinum wire and the reference electrode was an Ag/AgCl bate (20 mg, 0.1 mmol), DMEDA (20 µL, 0.2 mmol). Method
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Beilstein J. Org. Chem. 2012, 8, 683–692.
A gave the white product in 0.161 g (0.69 mmol, 69%) from Hz, 1H), 7.48 (t, J = 7.7 Hz, 2H), 7.49 (dd, J = 3.3 and 5.4 Hz,
2-iodothiophene and 0.186 g (0.80 mmol, 60%) from 1H), 7.53 (dd, J = 1.5 and 5.3 Hz, 1H), 7.61 (dd, J = 1.4 and 3.2
2-bromothiophene. mp 125–126 °C (from toluene); 1H NMR Hz, 1H), 7.90 (d, J = 7.1 Hz, 2H), 8.10 (s, 1H); 13C NMR (100
(400 MHz, CDCl3) δ 7.06 (dd, J = 3.8 and 5.5 Hz, 1H), 7.11 MHz, CDCl3) δ 114.14, 117.93, 120.85, 125.89, 127.29,
(dd, J = 3.6 and 5.1 Hz, 1H), 7.25 (dd, J = 1.4 and 5.5 Hz, 1H), 128.45, 128.92, 130.15, 148.01, 154.99; Anal. calcd for
7.29 (dd, J = 1.4 and 3.8 Hz, 1H), 7.35 (dd, J = 1.1 and 5.1 Hz, C12H9N3S: C, 63.41; H, 3.99; N, 18.49; S, 14.11; found: C,
1H), 7.48 (dd, J = 1,1 and 3.6 Hz, 1H), 8.00 (s, 1H); 13C NMR 63.51; H, 4.15; N, 18.46; S, 14.35; CIMS m/z: (M + H) 228, (M
(100 MHz, CDCl3) δ 118.30, 118.35, 122.98, 124.80, 125.59, − N2) 199, (M − C4H3N2S) 116.
126.29, 126.32, 132.04; CIMS m/z: (M + H) 234, (M − N2) 206;
Anal. calcd for C10H7N3S2: C, 51.48; H, 3.02; N, 18.01; S, 4-Phenyl-1-(thien-2-yl)-1H-1,2,3-triazole (9): 2-Iodothio-
27.49; found: C, 51.54; H, 3.13; N, 17.92; S, 26.87.
phene (3, 0.11 mL, 1 mmol) or 2-bromothiophene (3, 0.10 mL,
1 mmol), phenylacetylene (0.11 mL, 1 mmol), sodium azide
1,4-Diphenyl-1H-1,2,3-triazole (6): Iodobenzene (0.11 mL, (130 mg, 2 mmol), copper(I) iodide (19 mg, 0.1 mmol), sodium
1 mmol) or bromobenzene (0.11 mL, 1 mmol), phenylacetylene ascorbate (20 mg, 0.1 mmol), DMEDA (20 µL, 0.2 mmol).
(0.11 mL, 1 mmol), sodium azide (0.13 g, 2 mmol), copper(I) According to method A the colorless product was obtained in
iodide (19 mg, 0.1 mmol), sodium ascorbate (20 mg, 0.1 mmol), 111 mg (0.49 mmol, 49%) from 2-iodothiophene and 120 mg
DMEDA (20 µL, 0.2 mmol). Method A gave triazole 6 in (0.53 mmol, 53%) from 2-bromothiophene. mp 140–141 °C
0.199 g (0.90 mmol, 90%) from iodobenzene and in 0.923 g (from EE/n-hexane); 1H NMR (400 MHz, CDCl3) δ 7.07 (dd, J
(0.42 mmol, 42%) from bromobenzene as a white solid. = 1.4 and 5.5 Hz, 1H), 7.30 (dd, J = 1.4 and 3.8 Hz, 1H), 7.39
Changing the solvent to DMSO–water (9:1) gave 6 in 0.22 g (t, J = 7.4 Hz, 1H), 7.47 (t, J = 7.5 Hz, 2H), 7.89 (d, J = 7.1 Hz,
(0.99 mol, 99%) from iodothiophene at 60 °C and bromoben- 2H), 8.10 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 118.18,
zene at 95 °C, respectively. The analytical data correspond to 118.85, 122.83, 125.93, 126.28, 128.57, 128.93, 129.89, 138.43,
literature data [21]. 1H NMR (400 MHz, CDCl3) δ 7.37 (m, 148.30; CIMS m/z: (M + H) 228, (M − N2) 199; Anal. calcd for
1H), 7.47 (m, 3H), 7.56 (m, 2H), 7.80 (m, 2H), 7.92 (m, 2H), C12H9N3S: C, 63.41; H, 3.99; N, 18.49; S, 14.11; found: C,
8.15 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 120.6, 125.9, 63.48; H, 4.03; N, 18.58; S, 13.92.
128.4, 128.8, 128.9, 129.8.
4-(Thien-2-yl)-1-(thien-3-yl)-1H-1,2,3-triazole (10): 3-Iodoth-
1-Phenyl-4-(thien-2-yl)-1H-1,2,3-triazole (7): Iodobenzene iophene (1, 0.13 mL, 1 mmol) or 3-bromothiophene (0.10 mL,
(0.11 mL, 1 mmol), 2-ethynylthiophene (4, 0.11 g, 1 mmol), 1 mmol), 2-ethynylthiophene (4, 0.11 mg, 1 mmol), sodium
sodium azide (130 mg, 2 mmol), copper(I) iodide (19 mg, azide (130 mg, 2 mmol), copper(I) iodide (19 mg, 0.1 mmol),
0.1 mmol), sodium ascorbate (20 mg, 0.1 mmol), DMEDA sodium ascorbate (20 mg, 0.1 mmol), DMEDA (20 µL,
(20 µL, 0.2 mmol). Method A gave the colorless product in 0.2 mmol). According to method A the off-white product was
213.6 mg (940 µmol, 94%). mp 136–137 °C (from EE–n- obtained in 0.231 g (0.99 mmol, 99%) from 3-iodothiophene
hexane); 1H NMR (400 MHz, CDCl3) δ 7.12 (dd, J = 3.6 and and 0.11 g (0.47 mmol, 47%) from 3-bromothiophene. mp
5.1 Hz, 1H), 7.35 (dd, J = 1.1 and 5.1 Hz, 1H), 7.47 (t, J = 7.3 157–158 °C (from EE/n-hexane); 1H NMR (400 MHz, CDCl3)
Hz, 1H), 7.49 (dd, J = 1.1 and 3.3 Hz, 1H), 7.56 (t, J = 7.7 Hz, δ 7.14 (dd, J = 3.6 and 5.1 Hz, 1H), 7.37 (dd, J = 1.1 and 5.1
2H), 7.78 (d, J = 7.4 Hz, 2H), 8.11 (s, 1H); 13C NMR (100 Hz, 1H), 7.49 (dd, J = 1.1 and 3.5 Hz, 1H), 7.51 (dd, J = 2.5 and
MHz, CDCl3) δ 117.06, 120.57, 124.56, 125.38, 127.71, 5.6 Hz, 1H), 7.53 (dd, J = 1.6 and 5.3 Hz, 1H), 7.62 (dd, J = 1.6
128.88, 129.80, 132.50, 136.93, 143.52; Anal. calcd for and 3.1 Hz, 1H), 8.04 (s, 1H); 13C NMR (100 MHz, CDCl3) δ
C12H9N3S: C, 63.41; H, 3.99; N, 18.49; S, 14.11; found: C, 100.00, 114.31, 117.41, 120.83, 124.61, 125.42, 127.35,
63.40; H, 4.07; N, 18.44; S, 14.43; CIMS m/z: (M + H) 228, (M 127.71; CIMS m/z: (M + H) 234, (M − N2) 206, (M −
− N2) 199.
C4H3N2S) 122; HRMS–ESI (m/z): (M + Na) calcd for
C10H7N3NaS2, 255.9974; found, 255.9981; (M + H) calcd for
4-Phenyl-1-(thien-3-yl)-1H-1,2,3-triazole (8): 3-Iodothio- C10H8N3S2, 234.0154; found, 234.0157.
phene (1, 0.13 mL, 1 mmol), phenylacetylene (0.11 mL,
1 mmol), sodium azide (130 mg, 2 mmol), copper(I) iodide (19 1,4-Di(thien-3-yl)-1H-1,2,3-triazole (11): 3-Iodothiophene (1,
mg, 0.1 mmol), sodium ascorbate (20 mg, 0.1 mmol), DMEDA 0.11 mL, 1 mmol), 3-ethynylthiophene (0.11 mg, 1 mmol),
(20 µL, 0.2 mmol). Method A gave the pure off-white product sodium azide (130 mg, 2 mmol), copper(I) iodide (19 mg,
in 0.186 g (0.82 mmol, 82%) from 3-iodothiophene and 0.145 g 0.1 mmol), sodium ascorbate (20 mg, 0.1 mmol), DMEDA
(0.64 mmol, 64%) from 3-bromothiophene. mp 168–169 °C (20 µL, 0.2 mmol). The product was obtained, according to
(EE/n-hexane); 1H NMR (400 MHz, CDCl3) δ 7.37 (t, J = 7.3 method A, in 0.23 g (0.99 mmol, 99%) from 3-iodothiophene.
689

Beilstein J. Org. Chem. 2012, 8, 683–692.
mp 206–207 °C (from EE); 1H NMR (400 MHz, CDCl3) δ 7.42 235–236 °C dec (from DCM/petrol ether); 1H NMR (400 MHz,
(dd, J = 3.0 and 5.0 Hz, 1H), 7.48 (dd, J = 3.1 and 5.3 Hz, 1H), DMSO-d6) δ 7.13 (dd, J = 3.6 and 5.0 Hz, 1H), 7.15 (dd, J = 3.6
7.51 (m, 2H), 7.60 (dd, J = 1.5 and 3.1 Hz, 1H), 7.76 (dd, J = and 5.1 Hz, 1H), 7.36 (d, J = 3.7 Hz, 1H), 7.37 (d, J = 3.2 Hz,
1.2 and 3.0 Hz, 1H), 8.01 (s, 1H); 13C NMR (100 MHz, CDCl3) 1H), 7.40 (dd, J = 0.9 and 3.5 Hz, 1H), 7.44 (dd, J = 1.0 and 3.6
δ 114.13, 117.73, 120.86, 121.63, 125.83, 126.51, 127.31; Anal. Hz, 1H), 7.48 (d, J = 3.8 Hz, 1H), 7.54 (d, J = 4.0 Hz, 1H), 7.56
calcd for C10H7N3S2: C, 51.48; H, 3.02; N, 18.01; S, 27.49; (dd, J = 0.9 and 5.1 Hz, 1H), 7.61 (dd, J = 1.0 and 5.1 Hz, 1H),
found: C, 51.58; H, 3.11; N, 17.98; S, 27.73; CIMS m/z: (M + 9.25 (s, 1H); 13C NMR (100 MHz, DMSO-d6) δ 115.79,
H) 234, (M − N2) 206, (M − C4H3N2S) 122.
119.39, 119.96, 123.52, 124.97, 125.21, 125.60, 126.35, 126.97,
128.95, 129.02, 130.91, 134.14, 135.61, 135.90, 136.48, 136.86,
4-(2,2'-Bithien-5-yl)-1-(thien-2-yl)-1H-1,2,3-triazole (12): 142.86; CIMS m/z: (M + H) 399, (M − N2) 371; HRMS–ESI
2-Iodothiophene (3, 0.11 mL, 1 mmol), 5-ethynyl-2,2'-bithio- (m/z): (M + Na) calcd for C18H11N3NaS4, 419.9728; found,
phene (190 mg, 1 mmol), sodium azide (130 mg, 2 mmol), 419.9716; (M + H) calcd for C18H12N3S4, 397.9909; found,
copper(I) iodide (19 mg, 0.1 mmol), sodium ascorbate (20 mg, 397.9907.
0.1 mmol), DMEDA (20 µL, 0.2 mmol). The greenish-white
product was obtained by method A in 195 mg (0.62 mmol, 1-(5-Methylthien-2-yl)-4-(thien-2-yl)-1H-1,2,3-triazole (15):
62%). mp 159–160 °C dec (from toluene); 1H NMR (400 MHz, 2-Methyl-5-iodothiophene (224 mg, 1 mmol), 2-ethynylthio-
CDCl3) δ 7.04 (dd, J = 3.8 and 5.2 Hz, 1H), 7.06 (dd, J = 3.7 phene (0.11 mg, 1 mmol), sodium azide (130 mg, 2 mmol),
and 5.6 Hz, 1H), 7.17 (d, J = 3.8 Hz, 1H), 7.23 (dd, J = 1.3 and copper(I) iodide (19 mg, 0.1 mmol), sodium ascorbate (20 mg,
3.7 Hz, 1H), 7.24 (dd, J = 1.1 and 2.1 Hz, 1H), 7.26 (m, 1H), 0.1 mmol), DMEDA (20 µL, 0.2 mmol). According to method
7.29 (dd, J = 1.4 and 3.8 Hz, 1H), 7.37 (d, J = 3.8 Hz, 1H), 8.00 A the pure white product was obtained in 168 mg (0.68 mmol,
(s, 1H); 13C NMR (100 MHz, CDCl3) δ 18.16, 118.39, 123.04, 68%). mp 112 °C dec (from methanol); 1H NMR (400 MHz,
124.08, 124.23, 124.78, 125.38, 126.33, 127.95, 130.67, 136.99, CDCl3) δ 2.52 (d, J = 1.0 Hz, 3H), 6.70 (dd, J = 1.1 and 3.7 Hz,
137.62, 143.11; Anal. calcd for C14H9N3S3: C, 53.31; H, 2.88; 1H), 7.06 (dd, J = 3.7 Hz, 1H), 7.11 (dd, J = 3.6 and 5.1 Hz,
N, 13.32; S, 30.49; found: C, 53.27; H, 3.00; N, 13.24; S, 30.32; 1H), 7.34 (dd, J = 1.1 and 5.1 Hz, 1H), 7.45 (dd, J = 1.1 and 3.6
CIMS m/z: (M + H) 316, (M − N2) 288.
Hz, 1H), 7.95 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 15.41,
18.08, 118.41, 124.05, 124.68, 125.48, 127.70, 132.19, 144.63,
1-(2,2'-Bithien-5-yl)-4-(thien-2-yl)-1H-1,2,3-triazole (13): 160.35, 160.56; Anal. calcd for C11H9N3S2: C, 53.42; H, 3.67;
5-Iodo-2,2'-bithiophene (317 mg, 1 mmol), 2-ethynylthiophene N, 16.99; found: C, 53.17; H, 3.81; N, 16.76; CIMS m/z: (M +
(0.11 mg, 1 mmol), sodium azide (130 mg, 2 mmol), copper(I) H) 248, (M − N2) 220; HRMS–ESI (m/z): (M + Na) calcd for
iodide (19 mg, 0.1 mmol), sodium ascorbate (20 mg, 0.1 mmol), C11H9N3NaS2, 270.0130; found, 270.0139; (M + H) calcd for
DMEDA (20 µL, 0.2 mmol). The pure greenish-white product C11H10N3S2, 248.0311; found, 248.0323.
was obtained by method A in 211 mg (0.67 mmol, 67%). mp
173–174 °C (from toluene); 1H NMR (400 MHz, CDCl3) δ 7.06 1-(3-Methylthien-2-yl)-4-(thien-2-yl)-1H-1,2,3-triazole (16):
(dd, J = 3.6 and 5.1 Hz, 1H), 7.09 (d, J = 4.0 Hz, 1H), 7.12 (dd, 2-Iodo-3-methylthiophene (224 mg, 1 mmol), 2-ethynylthio-
J = 3.6 and 5.1 Hz, 1H), 7.18 (d, J = 4.0 Hz, 1H), 7.23 (dd, J = phene (0.11 mg, 1 mmol), sodium azide (130 mg, 2 mmol),
1.1 and 3.6 Hz, 1H), 7.29 (dd, J = 1.1 and 5.1 Hz, 1H), 7.36 (dd, copper(I) iodide (19 mg, 0.1 mmol), sodium ascorbate (20 mg,
J = 1.1 and 5.1 Hz, 1H), 7.48 (dd, J = 1.1 and 3.6 Hz, 1H), 8.02 0.1 mmol), DMEDA (20 µL, 0.2 mmol). The product was
(s, 1H); 13C NMR (100 MHz, CDCl3) δ 117.79, 118.45, 122.29, obtained according to method B as an oil in 29.6 mg
124.64, 124.87, 125.50, 125.67, 127.76, 128.05, 131.95, (0.12 mmol, 12%). 1H NMR (400 MHz, CDCl3) δ 2.26 (s, 3H),
135.89; CIMS m/z: (M+) 316, (M − N2) 288; HRMS–ESI (m/z): 6.91 (d, J = 5.6 Hz, 1H), 7.12 (dd, J = 3.6 and 5.1 Hz, 2H), 7.24
(M + Na) calcd for C14H9N3NaS3, 337.9851; found, 337.9847; (d, J =5.5 Hz, 1H), 7.34 (dd, J = 1.1 and 5.1 Hz, 1H), 7.46 (dd,
(M + H) calcd for C14H10N3S3, 316.0031; found, 316.0026.
J = 1.0 and 3.6 Hz, 1H), 7.90 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ 13.47, 121.12, 123.27, 124.67, 125.50, 127.74,
1,4-Di(2,2'-bithien-5-yl)-1H-1,2,3-triazole (14): 5-Iodo-2,2'- 129.20, 132.26, 132.91, 142.89; CIMS m/z: (M + H) 248, (M −
bithiophene (0.92 g, 1 mmol), 5-ethynyl-2,2'-bithiophene N2) 219; HRMS–ESI (m/z): (M + Na) calcd for C11H9N3NaS2,
(0.19 mg, 1 mmol), sodium azide (130 mg, 2 mmol), copper(I) 270.0130; found, 270.0124.
iodide (19 mg, 0.1 mmol), sodium ascorbate (20 mg, 0.1 mmol),
DMEDA (20 µL, 0.2 mmol). The pure orange product was Ethyl 5-(4-(thien-2-yl)-1H-1,2,3-triazol-1-yl)thiophene-2-
obtained by method B in 131 mg (0.33 mmol, 33%). The carboxylate (17): Ethyl 2-iodo-5-thiophenecarboxylate
extraction with ethyl acetate failed because of the low solu- (345 mg, 1 mmol), 2-ethynylthiophene (0.11 mg, 1 mmol),
bility of the product. It was therefore extracted with THF. mp sodium azide (130 mg, 2 mmol), copper(I) iodide (19 mg,
690

Beilstein J. Org. Chem. 2012, 8, 683–692.
0.1 mmol), sodium ascorbate (20 mg, 0.1 mmol), DMEDA 1H), 8.02 (s, 1H); 13C NMR (100 MHz, CDCl3) δ −0.09, −0.04,
(20 µL, 0.2 mmol). According to procedure B the product was 118.29, 118.40, 123.06, 126.34, 127.47, 127.86, 128.94, 130.28,
obtained as a colorless solid in 186 mg (0.61 mmol, 61%). mp 131.73, 132.29, 134.20, 138.13, 139.79, 140.87, 142.30, 142.50,
135 °C dec (from DCM/petrol ether); 1H NMR (400 MHz, 142.76; CIMS m/z: (M + H) 542, (M − N2) 513, (M −
CDCl3) δ 1.40 (t, J = 7.1 Hz, 3H), 4.39 (q, J = 7.1 Hz, 2H), 7.13 Si(CH3)3) 470, (M − N2Si(CH3)3) 441, (M − 2Si(CH3)3) 398;
(dd, J = 3.6 and 5.1 Hz, 1H), 7.28 (d, J = 4.1 Hz, 1H), 7.37 (dd, HRMS–ESI (m/z): (M + Na) calcd. for C24H27N3NaS4Si2,
J = 1.1 and 5.1 Hz, 1H), 7.49 (dd, J = 1.1 and 3.6 Hz, 1H), 7.74 564.0519; found, 564.0514.
(d, J = 4.1 Hz, 1H), 8.05 (s, 1H); 13C NMR (100 MHz, CDCl3)
δ 14.29, 61.75, 117.45, 117.50, 125.14, 125.94, 127.82, 130.61, 1,4-Phenylene-bis(4'-(thien-2''-yl)-1'H-1',2',3'-triazol-1'-yl)
131.55, 132.44, 143.87, 161.49; Anal calcd for C13H11N3O2S2: (21): 1,4-Diiodobenzene (330 mg, 1 mmol) or 1,4-dibromoben-
C, 51.13; H, 3.63; N, 13.76; S, 21.00; found: C, 51.12; H, 3.71; zene (236 mg, 1 mmol), 2-ethynylthiophene (0.22 mg, 2 mmol),
N, 13.72; S, 21.07; CIMS m/z: (M + H) 306, (M − N2) 278, (M sodium azide (260 mg, 4 mmol), cupric sulfate pentahydrate
− C2H5N2) 250.
(50 mg, 0.2 mmol), sodium ascorbate (40 mg, 0.2 mmol),
DMEDA (40 µL, 0.4 mmol). The reaction was performed in
Ethyl 2-(4-(thien-2-yl)-1H-1,2,3-triazol-1-yl)thiophene-3- DMSO–water (9:1). 1,4-Diiodobenzene yielded in 372 mg
carboxylate (18): Ethyl 2-iodo-3-thiophenecarboxylate (0.99 mmol, 99%) at 50 °C, from 1,4-dibromobenzene the
(345 mg, 1 mmol), 2-ethynylthiophene (0.11 mg, 1 mmol), disubstituted product was obtained in 368.5 mg (0.98 mmol,
sodium azide (130 mg, 2 mmol), copper(I) iodide (19 mg, 98%) at 95 °C. mp 310 °C dec (from toluene); 1H NMR (400
0.1 mmol), sodium ascorbate (20 mg, 0.1 mmol), DMEDA MHz, THF-d8) δ 7.09 (dd, J = 3.6 and 5.1 Hz, 2H), 7.41 (dd, J
(20 µL, 0.2 mmol). According to procedure B no product could = 1.1 and 5.1 Hz, 2H), 7.50 (dd, J = 1.1 and 3.6 Hz, 2H), 8.15
be isolated.
(s, 4H), 8.77 (s, 2H); 13C NMR (100 MHz, DMSO-d6) δ
100.00, 119.47, 121.89, 125.26, 126.59, 128.56, 132.63, 136.68,
1-[5,5''-Bis(trimethylsilyl)-[2,2':3',2''-terthien]-5'-yl]-4- 143.41; CIMS m/z: (M + H) 377, (M − N2) 349, (M − N4) 320;
(thien-2-yl)-1H-1,2,3-triazole (19): 5'-Iodo-5,5"- HRMS–ESI (m/z): (M + Na) calcd for C18H12N6NaS2,
bis(trimethylsilyl)-[2,2':3',2"-terthiophene] (259 mg, 0.5 mmol), 399.0457; found, 399.0452.
2-ethynylthiophene (54 mg, 0.5 mmol), sodium azide (65 mg,
References
1. Mishra, A.; Ma, C.-Q.; Bäuerle, P. Chem. Rev. 2009, 109, 1141–1276.
1 mmol), copper(I) iodide (10 mg, 50 µmol), sodium ascorbate
(10 mg, 50 µmol), DMEDA (10 µL, 0.1 mmol). By method B
doi:10.1021/cr8004229
the product was obtained in 111 mg (0.205 mmol, 41%) as
2. Perepichka, I. F.; Perepichka, D. F., Eds. Handbook of
yellowish needles. mp 119–120 °C (from petrol ether);
Thiophene-Based Materials: Applications in Organic Electronics and
1H NMR (400 MHz, CDCl3) δ 0.32 (2 × s, 18H), 7.11 (dd, J =
Photonics; Wiley-VCH: Weinheim, Germany, 2009.
3.7 and 5.2 Hz, 1H), 7.13–7.16 (m, 3H), 7.22 (d, J = 3.4 Hz,
1H), 7.34 (s, 1H), 7.35 (dd, J = 1.0 and 5.1 Hz, 1H), 7.48 (dd, J
= 1.0 and 3.5 Hz, 1H), 8.03 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ −0.15, −0.1, 117.52, 120.04, 124.89, 125.68, 127.75,
128.21, 128.67, 129.62, 130.77, 131.91, 134.21, 135.88, 138.46,
141.37, 141.55, 143.18, 143.45, 143.53, 145.41; HRMS–ESI
(m/z): (M + Na) calcd for C24H27N3NaS4Si2, 564.0519; found,
564.0513.
3. Müllen, K.; Wegner, G., Eds. Electronic Materials: The Oligomer
Approach; Wiley-VCH: Weinheim, Germany, 1998.
4. Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508–524.
doi:10.1002/anie.198605081
5. Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457–2483.
doi:10.1021/cr00039a007
6. Littke, A. F.; Fu, G. C. Angew. Chem., Int. Ed. 2002, 41, 4176–4211.
doi:10.1002/1521-3773(20021115)41:22<4176::AID-ANIE4176>3.0.CO
;2-U
7. Doucet, H.; Hierso, J.-C. Angew. Chem., Int. Ed. 2007, 46, 834–871.
doi:10.1002/anie.200602761
4-[5,5''-Bis(trimethylsilyl)-[2,2':3',2''-terthien]-5'-yl]-1-
(thien-2-yl)-1H-1,2,3-triazole (20): 2-Iodothiophene (0.03 mL,
0.25 mmol), 2-[5,5"-bis(trimethylsilyl)-[2,2':3',2"-terthien]-5'-
yl]ethynyl-1-trimethylsilane (125 mg, 0.3 mmol), sodium azide
(35 mg, 0.5 mmol), copper(I) iodide (5 mg, 25 µmol), sodium
ascorbate (5 mg, 25 µmol), DMEDA (5 µL, 50 µmol). By
method A the product was obtained as yellow solid in 124 mg
(0.23 mmol, 92%). mp 129–130 °C (from petrol ether);
1H NMR (400 MHz, CDCl3) δ 0.32 (2 × s, 18H), 7.07 (dd, J =
3.8 and 5.4 Hz, 1H), 7.12–7.15 (m, 3H), 7.21 (d, J = 3.5 Hz,
1H), 7.25 (m, 1H), 7.29 (dd, J = 1.3 and 3.8 Hz, 1H), 7.52 (s,
8. Negishi, E.; Anastasia, L. Chem. Rev. 2003, 103, 1979–2018.
doi:10.1021/cr020377i
9. de Meijere, A.; Diederich, F., Eds. Metal-Catalyzed Cross-Coupling
Reactions; Wiley-VCH: Weinheim, Germany, 2004.
10.Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Angew. Chem., Int. Ed. 2001,
40, 2004–2021.
doi:10.1002/1521-3773(20010601)40:11<2004::AID-ANIE2004>3.0.CO
;2-5
Angew. Chem. 2001, 113, 2056–2075.
doi:10.1002/1521-3757(20010601)113:11<2056::AID-ANGE2056>3.3.
CO;2-N
691

Beilstein J. Org. Chem. 2012, 8, 683–692.
11.Wu, P.; Feldman, A. K.; Nugent, A. K.; Hawker, C. J.; Scheel, A.;
Voit, B.; Pyun, J.; Fréchet, J. M. J.; Sharpless, K. B.; Fokin, V. V.
Angew. Chem., Int. Ed. 2004, 43, 3928–3932.
36.Chittaboina, S.; Xie, F.; Wang, Q. Tetrahedron Lett. 2005, 46,
2331–2336. doi:10.1016/j.tetlet.2005.01.175
37.Spagnolo, P.; Zanirato, P. J. Org. Chem. 1978, 43, 3539–3541.
doi:10.1021/jo00412a027
doi:10.1002/anie.200454078
12.Bock, V. D.; Hiemstra, H.; van Maarseveen, J. H. Eur. J. Org. Chem.
2006, 51–68. doi:10.1002/ejoc.200500483
38.Cymermann-Craig, J.; Harrisson, R. J. Aust. J. Chem. 1955, 8,
378–384. doi:10.1071/CH9550378
13.Lutz, J.-F. Angew. Chem., Int. Ed. 2007, 46, 1018–1025.
doi:10.1002/anie.200604050
39.Jenekhe, S. A.; Lu, L.; Alam, M. M. Macromolecules 2001, 34,
7315–7324. doi:10.1021/ma0100448
Angew. Chem. 2007, 119, 1036–1043. doi:10.1002/ange.200604050
14.Wu, P.; Fokin, V. V. Aldrichimica Acta 2007, 40, 7–17.
15.Parent, M.; Mongin, O.; Kamada, K.; Katan, C.; Blanchard-Desce, M.
Chem. Commun. 2005, 2029–2031. doi:10.1039/b419491h
16.Kappe, C. O.; Van der Eycken, E. Chem. Soc. Rev. 2010, 39,
1280–1290. doi:10.1039/b901973c
40.Garcia, P.; Pernaut, J. M.; Hapiot, P.; Wintgens, V.; Valat, P.;
Garnier, F.; Delabouglise, D. J. Phys. Chem. 1993, 97, 513–516.
doi:10.1021/j100104a040
41.Luker, T. J.; Beaton, H. G.; Whiting, M.; Mete, A.; Cheshire, D. R.
Tetrahedron Lett. 2000, 41, 7731–7735.
doi:10.1016/S0040-4039(00)01307-1
17.de Miguel, G.; Wielopolski, M.; Schuster, D. I.; Fazio, M. A.; Lee, O. P.;
Haley, C. K.; Ortiz, A. L.; Echegoyen, L.; Clark, T.; Guldi, D. M.
J. Am. Chem. Soc. 2011, 133, 13036–13054. doi:10.1021/ja202485s
18.Hänni, K. D.; Leigh, D. A. Chem. Soc. Rev. 2010, 39, 1240–1251.
doi:10.1039/b901974j
42.Adams, R. N. Electrochemistry at Solid Electrodes; Dekker: New York,
1969; pp 143–169.
43.Eaton, D. F. Pure Appl. Chem. 1988, 60, 1107–1114.
doi:10.1351/pac198860071107
44.Mishra, A.; Ma, C.-Q.; Janssen, R. A. J.; Bäuerle, P. Chem.–Eur. J.
2009, 15, 13521–13534. doi:10.1002/chem.200901242
45.Spinelli, D.; Zanirato, P. J. Chem. Soc., Perkin Trans. 2 1993,
1129–1133. doi:10.1039/p29930001129
19.Malkoch, M.; Schleicher, K.; Drockenmuller, E.; Hawker, C. J.;
Russell, T. P.; Wu, P.; Fokin, V. V. Macromolecules 2005, 38,
3663–3678. doi:10.1021/ma047657f
20.Ornelas, C.; Aranzaes, J. R.; Cloutet, E.; Alves, S.; Astruc, D.
Angew. Chem., Int. Ed. 2007, 46, 872–877.
doi:10.1002/anie.200602858
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Angew. Chem. 2007, 119, 890–895. doi:10.1002/ange.200602858
21.van Steenis, D. J. V. C.; David, O. R. P.; van Strijdonck, G. P. F.;
van Maarseveen, J. H.; Reek, J. N. H. Chem. Commun. 2005,
4333–4335. doi:10.1039/b507776a
This is an Open Access article under the terms of the
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(http://creativecommons.org/licenses/by/2.0), which
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22.Nagarjuna, G.; Yurt, S.; Jadhav, K. G.; Venkataraman, D.
Macromolecules 2010, 43, 8045–8050. doi:10.1021/ma101657e
23.Golas, P. L.; Matyjaszewski, K. Chem. Soc. Rev. 2010, 39, 1338–1354.
doi:10.1039/b901978m
24.Burley, G. A.; Gierlich, J.; Mofid, M. R.; Nir, H.; Tal, S.; Eichen, Y.;
Carell, T. J. Am. Chem. Soc. 2006, 128, 1398–1399.
doi:10.1021/ja055517v
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
25.El-Sagheer, A. H.; Brown, T. Chem. Soc. Rev. 2010, 39, 1388–1405.
doi:10.1039/b901971p
(http://www.beilstein-journals.org/bjoc)
26.Zhou, Z.; Fahrni, C. J. J. Am. Chem. Soc. 2004, 126, 8862–8863.
doi:10.1021/ja049684r
The definitive version of this article is the electronic one
which can be found at:
27.Lau, Y. H.; Rutledge, P. J.; Watkinson, M.; Todd, M. H.
Chem. Soc. Rev. 2011, 40, 2848–2866. doi:10.1039/c0cs00143k
28.Struthers, H.; Mindt, T. L.; Schibli, R. Dalton Trans. 2010, 39, 675–696.
doi:10.1039/b912608b
doi:10.3762/bjoc.8.76
29.Happ, B.; Escudero, D.; Hager, M. D.; Friebe, C.; Winter, A.; Görls, H.;
Altuntas, E.; González, L.; Schubert, U. S. J. Org. Chem. 2010, 75,
4025–4038. doi:10.1021/jo100286r
30.Stengel, I.; Mishra, A.; Pootrakulchote, N.; Moon, S.-J.;
Zakeeruddin, S. M.; Grätzel, M.; Bäuerle, P. J. Mater. Chem. 2011, 21,
3726–3734. doi:10.1039/c0jm03750h
31.Wild, A.; Friebe, C.; Winter, A.; Hager, M. D.; Grummt, U.-W.;
Schubert, U. S. Eur. J. Org. Chem. 2010, 1859–1868.
doi:10.1002/ejoc.200901112
32.Andersen, J.; Madsen, U.; Björkling, F.; Liang, X. Synlett 2005,
2209–2213. doi:10.1055/s-2005-872248
33.Valenti, F.; Zanirato, P. J. Chem. Soc., Perkin Trans. 2 1999, 623–628.
doi:10.1039/a807350c
34.Feldmann, A. K.; Colasson, B.; Fokin, V. V. Org. Lett. 2004, 6,
3897–3899. doi:10.1021/ol048859z
35.Kacprzak, K. Synlett 2005, 6, 943–946. doi:10.1055/s-2005-864809
692