Synthesis of nitro- and amino-functionalized π-conjugated oligomers incorporating 3,4-ethylenedioxythiophene (EDOT) units

Article abstract of DOI:10.1016/j.tet.2012.10.088

Dissymmetric π-conjugated oligomers incorporating 3,4- ethylenedioxythiophene (EDOT) units and bearing nitro and amino end-groups were synthesized in good yields through Pd-catalyzed Suzuki coupling reactions and direct C-H bond arylation. Their spectrosc

Full text of DOI:10.1016/j.tet.2012.10.088

Tetrahedron xxx (2012) 1e6
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Synthesis of nitro- and amino-functionalized
p
-conjugated oligomers
incorporating 3,4-ethylenedioxythiophene (EDOT) units
*
€
ꢀ
Gaelle Trippe-Allard, Jean-Christophe Lacroix
ꢀ
Nano-Electro-Chemistry Group, Univ Paris Diderot, Sorbonne Paris Cite, ITODYS, UMR 7086 CNRS, 15, rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 July 2012
Received in revised form 5 October 2012
Accepted 10 October 2012
Available online xxx
Dissymmetric
p-conjugated oligomers incorporating 3,4-ethylenedioxythiophene (EDOT) units and
bearing nitro and amino end-groups were synthesized in good yields through Pd-catalyzed Suzuki
coupling reactions and direct CeH bond arylation. Their spectroscopic properties show that they have
a low HOMOeLUMO gap. They are easily oxidized at low potential and could be used in various appli-
cations ranging from photovoltaics to molecular electronics.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Oligothiophene synthesis
Ethylenedioxythiophene
p-Conjugated oligomers
Diazonium precursors
Electrodeposition
1. Introduction
to nitrobenzene and aniline has been synthesized. A second series
mixes EDOT and thiophene units.
Conjugated oligomers based on thiophene(T) are extensively
used in plastic and organic electronics.1,2 Such oligo(T) have been
variously functionalized, and many reviews have described the
2. Results and discussions
2.1. Synthesis
wide range of
p
-conjugated materials derived from oligo (T).3
Poly(3,4-ethylenedioxythiophene) (PEDOT) is an another widely
used thiophene-based polymer.4 It is characterized by a lower ox-
idation potential than poly(T), by a smaller intrinsic band gap and
Among the organometallic reactions often used to synthesize
oligothiophene derivatives, we have chosen the Suzuki reaction,
since good yield, versatility, and easy removal of residual boronic
salts by simple washing with water are reported.
better processability.5 EDOT incorporation into a
p-conjugated
chain enhances the
p-donor ability and extends the properties of
this class of material. Functionalized EDOT oligomers are thus of
general interest. Oligo(EDOT) bearing a terminal amino group is of
particular interest since it can be oxidized to yield an electroactive
dimer or new conductive polymers.6 It can also be transformed into
the diazonium salt and grafted onto an electrode by diazonium salt
electroreduction.7 Such a modified surface associates a low oxida-
tion potential with easy on/off switching of the transport properties
across the grafted layer, and might be used in the design of new
switchable devices8 and metal/molecule/metal junctions in mo-
lecular electronics.9
Boronic derivatives 1 and 2 were firstly prepared from EDOT and
biEDOT, respectively.10 Then, reaction of 4-bromonitro-benzene
with 1 and 2 led to compounds 3 and 4 in 74% and 76% yield, re-
spectively (Scheme 1).
Compound 4 has also been prepared by an alternative one-step
synthetic route using direct CeH arylation of EDOT (Scheme 2).11 In
spite of its potential interest, this method is not often used to
prepare symmetrical oligothiophenes based on EDOT.12 A few ex-
amples of mono arylation leading to unsymmetrical derivatives
have also been reported but with poor to moderate yields (35e55%)
after 8e12 h reaction. Catellani et al.13 achieved satisfactory yields
(72e82%) by increasing the reaction time (24 h). In our case, the
direct arylation reaction between 4-bromonitrobenzene and
a slight excess of biEDOT (1.1 equiv) was performed in DMF at 80 ꢀC
and catalyzed by 10% Pd(OAc)2. The reaction mixture, initially pale
yellow, turned orange after 10 min and red after 1 h, indicating an
increase in the conjugation length. In this way, compound 4
In the present paper, we report the synthesis of various com-
pounds based on EDOT and thiophene units, terminated by aniline
or nitrobenzene. A first series having one to three EDOT units linked
* Corresponding author. Tel.: þ33 157277200; fax: þ33 157277263; e-mail address:
lacroix@univ-paris-diderot.fr (J.-C. Lacroix).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.10.088
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2
compound 7. The synthetic approach is described in Scheme 4.
Firstly, intermediate 9, synthesized as previously reported,14 was
iodinated in excellent yield to compound 10. Then, this latter was
reacted with boronic EDOT 1 to give compound 8 in 78% yield
(Scheme 4).
Scheme 1. Synthesis of nitrophenyl-EDOT derivatives using Suzuki coupling.
Scheme 4. Synthesis of nitrophenyl-thiophene-EDOT by Suzuki coupling.
Nitro compounds are pushepull molecules of interest but are
also intermediates for amino derivatives. To this end, all the ni-
trobenzene derivatives were reduced in satisfactory yield by hy-
drazine15 in the presence of Pd/C. The amino compounds are shown
in Scheme 5.
Scheme 2. Synthesis of nitrophenyl-biEDOT derivative using direct CeH arylation.
containing a biEDOT unit was obtained in 72% yield, and no trace of
the symmetrical compound was observed by 1H NMR. Suzuki re-
action and CeH direct arylation of biEDOT led in both cases to
compound 4 in good yields. We have chosen in this work to prepare
other nitrophenyl precursors with boronic intermediates readily
available. The use of direct CeH bond arylations to generate dis-
symmetric functionalized (EDOT)-based oligomers in good yields
will be reported elsewhere.
In order to increase the conjugation length, compound 6 bearing
three EDOT units was synthesized. Two alternative approaches are
possible. That used to generate compounds 3 and 4 requires the
preparation of the boronic terEDOT derivative. An alternative two-
step approach, described in Scheme 3, was preferred. Firstly,
compound 3 was iodinated by reaction with iodine in the presence
of mercuric oxide in 98% yield. The resulting intermediate 5 reacted
then with boronic biEDOT 2 to give terEDOT 6 in good yield (71%)
(Scheme 3).
Scheme 5. Aminophenyl-EDOT derivatives synthesized.
2.2. UVevisible spectroscopy
The UVevisible characteristics of the EDOT-based p-conjugated
molecules bearing nitro groups are summarized in Table 1. All
compounds are colored and display two absorption bands, between
384 and 481 nm, with the lowest energy band the stronger. This
absorption involves the HOMO mainly localized on the EDOT units
and the LUMO more centered on the nitrobenzene unit, as depicted
for compound 4 in Fig. 1 (PM6 calculations). It is thus related to
partial intramolecular charge transfer, and such molecules can be
considered as pushepull systems. Nitrophenyl-bithiophene14 (2-
(4-nitrophenyl)-5,20-bithiophene) 14 was taken as reference to
compare the effect of biEDOT. Changing bithiophene to biEDOT
leads to bathochromic shifts of 45 nm and 49 nm for the main and
the minor peaks, respectively. This behavior is due to the presence
of the electron-donating ethylendioxy groups on the thiophene
units, which decreases the HOMOeLUMO gap of the molecules. In
addition, increasing the number of EDOT units in the chain causes
a bathochromic shift of 54 nm for two EDOTs (4) and 97 nm for
three EDOTs (6) compared to a single EDOT (3). Contrary to several
Conditions: 5% Pd(PPh3)4, 3 eq. Na2CO3, DMF, 110°C
Scheme 3. Increasing the conjugation length of nitrophenyl-EDOT oligomers by Su-
zuki coupling.
A
second family of dissymmetric p-conjugated oligomers
combining EDOT and thiophene units, and bearing the nitroben-
zene end-group was prepared. The first compound has a terminal
thiophene unit. Reaction between the iodide intermediate 5 and
boronic thiophene gives compound 7 in 63% yield.
In order to study the influence of the position of EDOT on the
physical properties of the oligomers, we have also prepared com-
pound 8, in which EDOT and thiophene are permuted compared to
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3
Table 1
and higher HOMOeLUMO gaps than observed for the nitro com-
pounds. Contrary to the nitro precursors 7 and 8, where there is one
EDOT and one thiophene unit, the terminal units have no influence
on the position of the absorption maximum for the amino de-
rivatives 12 and 13. In the case of amino compounds with more
than one EDOT unit, hyperfine structure is observed; this indicates
that there are intramolecular S/O interactions between two ad-
jacent EDOTs even in solution.
UVevisible peak positions of various nitro- and amino-phenyl-EDOT oligomers
(T¼Thiophene, E¼EDOT)a
Nitro compounds
lmax (nm)
Amino compounds
lmax (nm)
2TPhNO2 (14)
EPhNO2 (3)
2EPhNO2 (4)
3EPhNO2 (6)
TEPhNO2 (7)
ETPhNO2 (8)
393, 274
384
438, 323
481, 378
419, 273
412, 316
2TPhNH2 (15)
EPhNH2 (9)
2EPhNH2 (10)
3EPhNH2 (11)
TEPhNH2 (12)
ETPhNH2 (13)
358
309
392, 371, 284
435, 414
367, 275
365
a
lmax in acetonitrile 10ꢁ4 M, except for 3EPhNH2: 10ꢁ5 M.
2.3. Electrochemical properties
In a preliminary investigation of the redox properties of these
molecules, they were dissolved in 0.1 M LiClO4 acetonitrile solution,
and cyclic voltammetry performed using a carbon working elec-
trode, stainless steel grid counter-electrode and SCE reference. All
compounds were oxidized at low potential with an irreversible
peak (Table 2).
Such low potential peaks can be compared to that of
aminophenyl-bithiophene at 0.59 V. The replacement of two thio-
phenes by two
p-electron donor EDOT units decreases the oxida-
tion potential by 0.23 V. As expected, the increase in the
conjugation length from one EDOT to three EDOT units decreases
Eox from 0.53 V/SCE for compound 9 to 0.20 V for compound 11
(Fig. 2). In the case of the mixed EDOT/thiophene series, there is no
significant difference between aminophenyl derivatives 12 and 13.
Their oxidation potentials are intermediate between those of
aminophenyl-bithiophene 15 and aminophenyl-biEDOT 10, which
correlates with their optical properties.
Fig. 1. UV spectra of 2EPhNO2 (dash line) C¼10ꢁ4 M in acetonitrile, 2EPhNH2 (straight
line) C¼10ꢁ4 M in acetonitrile. Inset HOMO and LUMO of 2EPhNO2.
20
reported examples of oligoEDOT,16 no vibronic fine structure, due to
intramolecular S/O interactions, was observed in the UVevisible
spectra.
10
When the nitrophenyl derivative combines one EDOT and one
thiophene, as in 7 and 8, the main absorption peaks (419 nm and
412 nm for 7 and 8, respectively) are similar and lie between those
for nitrophenyl-bithiophene 14 and nitrophenyl-biEDOT 4. While
the position of the EDOT unit in the structure does not influence the
position of the main transition peak, it has a marked effect on the
wavelength of the minor ones. Indeed, for this band, the terminal
unit seems to be all-important. In compound 7, thiophene is the
terminal unit and the wavelength of the minor peak is similar to
that of nitrophenyl-bithiophene 14. For compound 8, EDOT is the
terminal unit and the wavelength of the minor peak is similar to
that of nitrophenyl-biEDOT 4.
0
-10
-20
-30
-100
0
100
200
300
400
500
600
E (mV/ECS)
Amino derivatives were also characterized by UVevisible
spectroscopy (Table 2). If we compare a nitro precursor and the
corresponding amino derivative, there is a hypsochromic shift of
the absorption maximum close to 45 nm, except for the monoEDOT
compound 9 for which it reaches 75 nm. This decrease is due to the
replacement of the electron-attracting nitro group by a donor
amino function. As a consequence, the pushepull system is
replaced by a push-push system with LUMOs lying at higher energy
Fig. 2. CV of EPhNH2 (in black), 2EPhNH2 (in red), 3EPhNH2 (in green), C¼10ꢁ3 M in
0.1 M LiClO4/acetonitrile, 100 mV sꢁ1/SCE.
Once oxidized, the radical cations of these molecules undergo
coupling reactions and thin electroactive films are easily obtained
using cyclic voltammetry or chronopotentiometry. Indeed, when
a constant current of I¼1.4$10ꢁ6 A is applied in a solution of
3EPhNH2 (5$10ꢁ4 M) and 0.1 M LiClO4 in acetonitrile solution, the
potential of the electrode stabilizes at 0.120 mV indicating that
a conductive material is generated. Fig. 3 shows the electroactivity
of a film (generated during 80 s with a deposition charge
Qd¼0.112 mC) in 0.1 M HClO4/water solution. A reversible redox
systems with Eox¼0.2 V and Ered¼ꢁ0.05 V is clearly observed. The
charge involved in the switching of the film (Qs) is here of 0.1 mC,
that is very close to that used to generate the film. As a consequence
Qs/Qd is around 1 and strongly deviates from a value of 0.1 found
when infinite chains are generated from a monomer or of 0.3 when
the same chains are obtained from a trimer. Such value clearly
shows that the generated insoluble oligomers are constituted of
Table 2
Electrochemical oxidation potential peak of various nitro-phenyl-EDOT oligomers
(T¼Thiophene, E¼EDOT)
Amino compounds
Eox (V/ECS)a
2TPhNH2 (14)
EPhNH2 (9)
2EPhNH2 (10)
3EPhNH2 (11)
TEPhNH2 (12)
ETPhNH2 (13)
0.59
0.53
0.36
0.20
0.48
0.49
a
Eox in acetonitrile 10ꢁ3 M, except for 3EPhNH2: 5$10ꢁ4 M.
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4
temperature during 1 h. Triisopropylborate (21 mL, 3 equiv) is
40
20
0
added and the reaction mixture is allowed to warm to room tem-
perature. After 2.5 h, a solution of pinacol (10.6 g) in THF (30 mL)
was added. The reaction is stirred during 30 min and then the
solvent was removed in vacuo. The residue dissolved in diethyl
ether is washed twice with water and dried over magnesium sul-
fate. The solvent is removed in vacuo. The product is used without
further purification.
4.2.1.1. 4,4,5,5-Tetramethyl-2-thiophen-2-yl-1,3,2-dioxaboro-la-
ne. This compound was prepared by the general procedure for the
synthesis of boronic ester, starting with 30 mmol of thiophene. Yield:
5.3 g, 85%. White powder.1H NMR (CDCl3):1.36 (s,12H, CH3); 7.20 (dd,
1H, 3.6, and 4.8 Hz); 7.64 (d, 1H, 4.8 Hz); 7.66 (d,1H, 3.6 Hz). 13C NMR
(CDCl3): 24.8 (CH3); 84.1; 128.2; 132.4; 137.2. MS (Mþꢂ): 210.
-20
-500
0
500
4.2.1.2. 2-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-5-yl)-4,4,5,5-
tetramethyl-2-thiophen-2-yl-1,3,2-dioxaborolane 1. This compound
was prepared by the general procedure for the synthesis of boronic
ester starting with 50 mmol of EDOT. Yield: 11.13 g, 85%. White
powder. 1H NMR (CDCl3): 1.34 (s, 12H, CH3); 4.17e4.20 (m, 2H);
4.29e4.31 (m, 2H); 6.63 (s, 1H). 13C NMR (CDCl3): 24.7 (CH3); 64.3
(CH2eO); 65.1 (CH2eO); 83.8 (CeOB); 107.5 (CHedot); 142.3 (CIV-O);
149.0 (CIVeO). MS (Mþꢂ): 268.
E (mV/SCE)
Fig. 3. CV of a GC bare electrode (in gray) and a GC modified electrode after deposition
by chronoamperometry of 3EPhNH2 (in black) (I¼1.4$10ꢁ6 A, t¼80 s) in 0.1 M LiClO4/
0.1 M HClO4/water, 100 mV sꢁ1/SCE.
a small and finite numbers of 3EPhNH2 units and suggests that
mainly dimers with a plausible structure close to H2NPh(E)6PhNH2
are obtained.
4.2.1.3. 4,4,5,5-Tetramethyl-2-(2,20,3,30-tetrahydro-5,50-bithieno
[3,4-b][1,4]dioxin-5-yl)-1,3,2-dioxaborolane 2. This compound was
prepared by the general procedure for the synthesis of boronic
ester, starting with 10 mmol of bi-EDOT. Yield: 3.94 g, 93%. Green
solid. 1H NMR (CDCl3): 1.28 (s, 12H, CH3); 4.23e4.25 (m, 2H);
4.32e4.34 (m, 6H); 6.31 (s, 1H). 13C NMR (CDCl3): 24.5 (CH3); 64.6
(CH2eO); 65.0 (CH2eO); 83.2 (CeOB); 97.5; 109.9; 137.0; 141.2. MS
(Mþꢂ): 408.
3. Conclusion
In summary, nitro- and amino-functionalized
oligomers incorporating EDOT units have been synthesized in good
yields. Dissymmetric -conjugated oligomers bearing nitro end-
groups have lower HOMOeLUMO gaps than those with amino
end-groups; the latter have low oxidation potentials ranging from
0.20 V to 0.53 V/SCE and lead easily to thin electroactive films. Such
molecules are of wide interest in materials science, in the design of
new switchable devices and metal/molecule/metal junctions, and
more generally in molecular and organic electronics.17
p-conjugated
p
4.2.2. General procedure for iodation of thiophene derivatives. To
a suspension of thiophene derivative (8 mmol) in acetic acid
(150 mL) is added mercuric oxide (1.04 equiv, 8.32 mmol) and io-
dine (1.02 equiv, 8.16 mmol). The mixture is degassed in an ultra-
sounds bath during 20 min and then stirred overnight. The
precipitate is filtered and then dissolved in dichloromethane. The
organic phase is washed successively by a solution of potassium
iodide, a solution of sodium hydrogenocarbonate and water. After
drying over magnesium sulfate, the solvent is removed in vacuo.
The product is used without further purification.
4. Experimental section
4.1. General
Reagents including EDOT, thiophene, triisopropylborate, pina-
col, 4-bromonitrobenzene, palladium catalyst, n-butyllithium and
hydrazine are commercially available. Bi-EDOT18 and 1-(thien-2-
yl)-4-nitrobenzene14 were synthesized according to the literature.
THF is distilled, under argon, over sodium and benzophenone.
Other solvents were used without purification. Reactions were
controlled by TLC (aluminum plates coated with silica gel, Merck
60, F-254) and UV light was used to show the spots. Purification by
4.2.2.1. 1-(5-Iodothien-2-yl)-4-nitrobenzene 9. This compound
was prepared by the general iodation procedure, starting with
7 mmol of thiophene derivative. Yield: 2.10 g, 90%. Yellow powder.
1H NMR (CDCl3): 7.13 (d, 1 H, 3.6 Hz); 7.30 (d, 1 H, 3.6 Hz); 7.66 (d,
1H, 8.4 Hz, Hc); 8.23 (d, 1H, 8.4 Hz, Hb). 13C NMR (CDCl3): 76.1 (Ch);
124.5 (Cc); 125.9 (Cb); 127.0 (Cf); 138.5 (Cg); 139.4 (Ca); 146.9 (Cd);
147.5 (Ce). MS (Mþ) 331.
chromatography was carried out using silica gel 60 (63e210 mm)
from VWR. 1H and 13C NMR spectra were recorded on a Bruker
Avance III 300 MHz or 400 MHz instrument. The chemical shifts are
calibrated on the reference value of the solvent.19 Mass spectrum
was recorded on Finigan 5890 coupled to DSQ1 spectrometer by
electronic impact (EI). The high-resolution mass spectra were car-
ried out by the service of CNRS in Vernaison. UVevisible spectra
were recorded on a Cary 500 spectrometer and cyclic voltammetry
was performed on a potentiostat CH Instrument 660.
4.2.2.2. 1-(5-Iodo-3,4-ethylenedioxythien-2-yl)-4-nitrobenzene
5. This compound was prepared by the general iodation procedure,
starting with 6.57 mmol of EDOT derivative. Yield: 2.52 g, 98%.
Yellow powder. 1H NMR (CDCl3): 4.37 (m, 4H); 7.78 (d, 1H, 9.2 Hz);
8.21 (d, 1H, 9.2 Hz). 13C NMR (CDCl3): 52.1 (Ch); 64.9 and 64.9 (Cf
0
0
and Cg ); 120.4 (Ce); 124.2 (Cb); 125.7 (Cc); 139.0 (Ca); 139.6 (Cf or
Cg); 145.0 (Cf or Cg); 145.7 (Cd). MS (Mþ) 389.
4.2. Synthetic procedure
4.2.3. General procedure for the Suzuki coupling reaction. The bo-
ronic compound (2 mmol), the iodo derivative (2 mmol), the sodium
carbonate (3 equiv, 6 mmol), tetrakis(triphenylphosphine) palla-
dium (0) (5%) are successively introduced into a Schlenck containing
25 mL of DMF. The reaction mixture is heated at 110 ꢀC from 2 to 3
4.2.1. General procedure for the synthesis of boronic ester. Under Ar,
a stirred solution of thiophenic compound (30 mmol) in distilled
THF (100 mL) is cooled to ꢁ78 ꢀC. A 2.5 M solution of butyllithium
(12 mL, 1 equiv) is added dropwise and the solution is stirred at this
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5
days. After return at room temperature, the solvent is removed in
vacuo. The brown residue is dissolved in dichloromethane, washed
twice with water, dried over magnesium sulfate and concentrated.
The crude product is purified by chromatography.
acetate (1.76 g, 18 mmol, 3 equiv), and tetrabuytyl-ammonium
bromide (1.93 g, 6 mmol) were successively introduced into
a Schlenck containing 20 mL of DMF. After complete dissolution,
palladium acetate (134 mg, 0.6 mmol, 0.1 equiv) was added and the
reaction mixture was heated at 80 ꢀC during 1 h. After return to
room temperature, ethanol was added and the red suspension was
cooled. The precipitate was filtered and washed with cold ethanol.
The nitro compound was then used without further purification.
Yield: 72% (1.74 g).
4.2.3.1. 2-(4-Nitrophenyl)-3,4-ethylenedioxythiophene
3. This
compound was prepared by the general Suzuki procedure starting
with 15 mmol of boronic derivative. Yield: 2.79g, 70%. Yellow pow-
1
0
0
der. H NMR (CDCl3): 4.28e4.40 (m, 2H, Hg ); 4.37e4.40 (m, 2H, Hf );
6.48 (s, 1H, Hh); 7.86 (d, 9.0 Hz, 2H, Hc); 8.17 (d, 9.0 Hz, 2H, Hb). 13
C
0
0
NMR (CDCl3): 64.3 (OCg H2); 65.1 (OCf H2); 101.0 (Ch); 124.1 (Cb);
4.2.5. General procedure for reduction of nitro in amino function. To
the nitro derivative (0.86 mmol) dissolved in THF (20 mL), palla-
dium (10%) on coal (0.086 mmol, 10%) and hydrazine (1 mL) is
added. The reaction mixture is refluxed during 4 h. After return at
room temperature, the suspension is filtered over Celite and then
the solvent is removed in vacuo. The residue dissolved in
dichloromethane is washed with water and dried over magnesium
sulfate. The product is then used without further purification.
125.7 (Cc); 139.8 (Ca); 140.9 (Cg); 142.9 (Cf); 145.8 (Cd). MS (Mþꢂ):
263. UV (CH3CN) (lmax (nm)), [log
(L molꢁ1 cmꢁ1)]: 384 [4.26].
3
4.2.3.2. 2-(4-Nitrophenyl)-3,4,30,40-bis(ethylenedioxy)-5,20-bi-
thiophene 4. This compound was prepared by the general Suzuki
procedure starting with 2 mmol of boronic derivative. The product
was purified by chromatography on silica gel using petroleum
ether/dichloromethane 3/7 as eluent. Yield: 316.3 mg, 36%. Dark
powder. 1H NMR (CDCl3): 4.23e4.27 (m, 2H, OCH2); 4.36e4.40 (m,
6H, 3x OCH2); 6.36 (s, 1H, Hl); 7.84 (d, 9.2 Hz, 2H, Hc); 8.17 (d, 9.2 Hz,
2H, Hb). 13C NMR (CDCl3): 63.9, 64.0, 64.4, and 64.7 (4ꢃ OCH2); 98.6
(Cl); 108.8, 111.5, 111.7 (Ce, Ch and Ci); 123.4 (Cb); 124.7 (Cc); 136.7,
137.4, 139.8, 140.7 (Cf, Cg, Cj, Ck); 139.3 (Ca); 144.4 (Cb); 145.0 (Cd).
Mass exact C18H13NO6NaS2 [MþNaþ]: calculated: 426.0082, found:
4.2.5.1. 2-(4-Aminophenyl)-3,4-ethylenedioxythiophene 9. This
compound was prepared by the general reduction procedure
starting with 0.65 mmol of nitro derivative. Yield: 130 mg, 86%.
1
0
White powder. H NMR (CDCl3): 4.23e4.25 (m, 2H, OCHf 2);
0
4.27e4.29 (m, 2H, OCHg ); 6.20 (s, 1H, Hh); 6.69 (d, 2H, 8.8 Hz, CHb);
13
0
7.51 (d, 2H, 8.8 Hz, CHc). C NMR (CDCl3): 64.5 (OCf H2); 64.7
(L molꢁ1 cmꢁ1)]: 438
(OCg H2); 95.7 (Ch); 115.2 (Cb); 118.1 (Ce); 123.8 (Ca); 127.4 (Cc);
0
426.0093. UV (CH3CN) (lmax (nm)), [log
3
[4.52], 323 [4.20].
136.7 (Cg); 142.2 (Cf); 145.2 (Cd). UV (CH3CN) (lmax (nm)): 309.
4.2.3.3. 2-(4-Nitrophenyl)-3,4,30,40,300,400-ter(ethylenedioxy)-
5,20,50,200-terthiophene 6. This compound was prepared by the
general Suzuki procedure starting with 1.2 mmol of boronic de-
rivative. The product was purified by chromatography on alumina
using dichloromethane as eluent. Yield: 465 mg, 71%. Dark powder.
1H NMR (CDCl3): 4.26 (m, 2H, OCH2); 4.30e4.50 (m, 10H, 5ꢃ OCH2);
6.33 (s, 1H, CHp); 7.86 (d, 2H, 8.8 Hz, CHc); 8.19 (d, 2H, 8.8 Hz, CHb).
Mass exact C24H17NO8S3 [MþHþ]: calculated: 543.0116, found:
4.2.5.2. 2-(4-Aminophenyl)-3,4,30,40-bis(ethylenedioxy)-5,20-bi-
thiophene 10. This compound was prepared by the general re-
duction procedure starting with 0.44 mmol of nitro derivative.
Yield: 124 mg, 76%. Red powder. 1H NMR (CDCl3): 3.70e3.73 (large
s, 2H); 4.24e4.27 (m, 2H); 4.33e4.37 (m, 6H); 6.27 (s, 1H); 6.69 (d,
2H, 8.4 Hz); 7.55 (d, 2H, 8.4 Hz). 13C NMR (CDCl3): 64.6, 64.6, 64.9,
and 65.0 (4ꢃ CH2O); 97.3 (ClH); 106.2 (Ci or Ch); 110.2 (Ci or Ch);
115.2 (CbH); 115.8 (Ce); 123.7 (Ca); 127.3 (CcH); 136.3, 136.7, 137.5,
and 141.3 (Cf, Cg, Cj and Ck); 145.0 (Cd). Mass exact C18H15NO4NaS2
[MþHþ]: calculated: 374.0521, found: 374.0515. UV (CH3CN) (lmax
(nm)): 392, 371, 284.
543.0126. UV (CH3CN) (lmax (nm)), [log
3
(L molꢁ1 cmꢁ1)]: 481
[4.17], 378 [3.84].
4.2.3.4. 2-(4-Nitrophenyl)-3,4-ethylenedioxy-5,20-bithiophene
7. This compound was prepared by the general Suzuki procedure
starting with 2 mmol of boronic derivative. Yield: 690 mg, 63%.
Orange powder. 1H NMR (CDCl3): 4.43 (s, 4H, 2ꢃ OCH2); 7.08 (dd,
1H, 3.2 and 5.2 Hz, CHk); 7.30 (d, 1H, 5.2 Hz, CHl); 7.34 (d, 1H, 3.2 Hz,
CHj); 7.86 (d, 1H, 8.8 Hz, CHc); 8.18 (d, 1H, 8.8 Hz, CHb). 13C NMR
(CDCl3): 64.7 and 65.0 (2ꢃ OCH2); 112.1 (Ce); 113.8 (Ci); 124.0 (Cj);
124.1 (Cb); 125.0 (Cl); 125.6 (Cc); 127.4 (Ck); 133.9 (Ch); 137.9 and
140.9 (Cf and Cg); 139.4 (Ca); 145.3 (Cd). Mass exact C16H11NO4S2
[Mþꢂ]: calculated: 345.0130, found: 345.0139. UV (CH3CN) (lmax
4.2.5.3. 2-(4-Aminophenyl)-3,4,30,40,300,400-ter(ethylenedioxy)-
5,20,50,200-terthiophene 11. This compound was prepared by the
general reduction procedure starting with 0.11 mmol of nitro de-
rivative. Yield: 56 mg, quantitative. Red powder. 1H NMR (CDCl3):
4.21e4.40 (m, 12H); 6.27 (s, 1H, CHp); 6.68 (d, 2H, 7.6 Hz, CHb); 7.55
(d, 2H, 7.6 Hz, CHc). Mass exact: C24H19NO6S3 [MþHþ] calculated:
513.0374, found: 513.0371. UV (CH3CN) (lmax (nm)): 435, 314.
4.2.5.4. 2-(4-Aminophenyl)-3,4-ethylenedioxy-5,20-bithiophe-ne
12. This compound was prepared by the general reduction pro-
cedure starting with 0.86 mmol of nitro derivative. Yield: 270 mg,
95%. Yellow powder. 1H NMR (CDCl3): 4.32e4.35 (m, 2H); 4.37e4.39
(m, 2H); 6.70 (d, 2H, 8.8 Hz, Hb); 7.02 (dd, 1H, 3.6 and 5.0 Hz, Hk);
7.20 (d, 1H, 5.0 Hz, Hl); 7.22 (d, 1H, 3.6 Hz, Hj); 7.53 (d, 2H, 8.8 Hz,
Hc). 13C NMR (CDCl3): 64.6 and 64.9 (2ꢃ OCH2); 108.3 (Ce or Ch);
115.2 (Cb); 115.5 (Ca); 122.3 (Cj); 123.3 (Cl); 127.1(Ck); 127.3 (Cc);
135.0 (Ci); 136.7 (Cf or Cg); 137.9 (Cf or Cg); 145.3 (Cd). Mass exact
(nm)), [log
3
(L molꢁ1 cmꢁ1)]: 419 [4.44], 273.
4.2.3.5. 2-(4-Nitrophenyl)-30,40-ethylenedioxy-5,20-bithiophe-ne
8. This compound was prepared by the general Suzuki procedure
starting with 4 mmol of boronic derivative. Yield: 1.38g, 78%. Orange
powder. 1H NMR (CDCl3): 4.28e4.31 (m, 2H, OCH2); 4.40e4.42 (m,
2H, OCH2); 6.23 (s, 1H, Hl); 7.25 (d, 4.0 Hz, 2H, Hf or Hg); 7.41 (d,
4.0 Hz, 2H, Hf or Hg); 7.73 (d, 8.8 Hz, 2H, Hc); 8.24 (d, 8.8 Hz, 2H, Hb).
13C NMR (CDCl3): 64.6 and 65.2 (2ꢃ OCH2); 98.1 (Cl); 111.7 and 138.4
(Cj and Ck); 123.9 and 126.0 (Cf and Cg); 124.5 (Cb); 125.4 (Cc); 137.6
and 139.0 (Ch and Ci); 140.6 (Ca); 142.0 (Ce); 146.3 (Cd). C16H11NO4S2
[MþHþ]. Mass exact: calculated: 345.0130, found: 345.0145. UV
C
16H9NO2S2 [MþHþ]: calculated: 316.0466, found: 316.0466. UV
(CH3CN) (lmax (nm)): 367, 275.
4.2.5.5. 2-(4-Aminophenyl)-30,40-ethylenedioxy-5,20-bithio-phene
13. This compound was prepared by the general reduction pro-
cedure starting with 0.6 mmol of nitro derivative. Yield: 189 mg,
83%. Yellow powder. 1H NMR (CDCl3): 4.76 (s, 2H); 4.25e4.27 (m,
(CH3CN) (lmax (nm)), [log
(L molꢁ1 cmꢁ1)]: 412 [4.40], 316 [3.92].
3
4.2.4. Alternative procedure to prepare 2-(4-nitrophenyl)-3,4,30,40-
bis(ethylenedioxy)-5,20-bithiophene. BiEDOT (1.87 g, 6.6 mmol,
1.1 equiv), 4-bromonitrobenzene (1.21 g, 6 mmol), potassium
0
0
2H, Hj ); 4.34e4.37 (m, 2H, Hk ); 6.20 (s, 1H, Hl); 6.68 (d, 2H, 8.8 Hz,
Hb); 7.06 (d, 1H, 4.0 Hz, Hf), 7.14 (d, 1H, 4.0 Hz, Hg); 7.41 (d, 2H,
ꢀ
Please cite this article in press as: Trippe-Allard, G.; Lacroix, J.-C., Tetrahedron (2012), http://dx.doi.org/10.1016/j.tet.2012.10.088

ꢀ
G. Trippe-Allard, J.-C. Lacroix / Tetrahedron xxx (2012) 1e6
6
8.8 Hz, Hc). 13C NMR (CDCl3): 64.6 (OCj H2); 65.0 (Ck H2); 96.5 (Cl);
112.6 (Ci); 115.3 (Cb); 121.3 (Cf); 123.8 (Cg); 125.0 (Ca); 126.8(Cc);
132.4 (Ch); 137.2 (Ck); 141.9 (Cj); 143.2 (Ce); 145.9 (Cd). Mass exact:
Ellinger, S.; McCarley, T. D.; Reynolds, J. R. Chem. Mater. 2012, 24, 255; (c) Dyer,
0
0
A. L.; Craig, M. R.; Babiarz, J. E.; Kiyak, K.; Reynolds, J. R. Macromolecules 2010,
ꢁ
43, 4460; (d) Turbiez, M.; Frere, P.; Blanchard, P.; Roncali, J. Tetrahedron 2005,
61, 5521.
C
16H9NO2S2 [MþHþ] calculated: 316.0466, found: 316.0461. UV
ꢁ
6. (a) Lacroix, J. C.; Garcia, P.; Audiere, J. P.; Clement, R.; Kahn, O. New J. Chem.
1990, 14, 87; (b) Genies, E. M.; Tsintavis, C. J. Electroanal. Chem. 1985, 195, 109.
7. (a) Belanger, D.; Pinson, J. Chem. Soc. Rev. 2011, 40, 3995; (b) Mahouche-Chergui,
S.; Gam-Derouich, S.; Mangeney, C.; Chehimi, M. M. Chem. Soc. Rev. 2011, 40,
4143.
(CH3CN) (lmax (nm)): 365.
Acknowledgements
ꢀ
8. (a) Fave, C.; Leroux, Y.; Trippe, G.; Randriamahazaka, H.; Noel, V.; Lacroix, J.-C. J.
Am. Chem. Soc. 2007, 129, 1890; (b) Stockhausen, V.; Ghilane, J.; Martin, P.;
Trippe-Allard, G.; Randriamahazaka, H.; Lacroix, J. C. J. Am. Chem. Soc. 2009, 131,
14920; (c) Santos, L.; Ghilane, J.; Martin, P.; Lacaze, P. C.; Randriamahazaka, H.;
This work was supported by the ANR-08-blan-0186-01. Dr. J.S.
Lomas is warmly thanked for editing the manuscript.
ꢀ
Lacroix, J.-C. J. Am. Chem. Soc. 2010, 132, 1690.
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Please cite this article in press as: Trippe-Allard, G.; Lacroix, J.-C., Tetrahedron (2012), http://dx.doi.org/10.1016/j.tet.2012.10.088