Selective syntheses of vinylenedithiathiophenes (VDTTs) and dithieno[2,3-b;2′,3′-d]thiophenes (DTTs); Building blocks for π-conjugated systems

Article abstract of DOI:10.1016/j.tet.2011.11.059

Selective syntheses of 3,4-vinylenedithiathiophenes (VDTTs) and dithieno[2,3-b;2′,3′-d]thiophenes (DTTs), having Ph, 4-CH ₃OC₆H₄, 4-BrC₆H₄, 4-NO₂C₆H₄ and 4-(CH₃

Full text of DOI:10.1016/j.tet.2011.11.059

Tetrahedron 68 (2012) 1216e1222
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Selective syntheses of vinylenedithiathiophenes (VDTTs) and dithieno
[2,3-b;20,30-d]thiophenes (DTTs); building blocks for
p-conjugated systems
Ipek Osken a, Onur Sahin a, Ali S. Gundogan a, Hakan Bildirir a, Asli Capan a, Erdal Ertas b,
,
,c,
*
Mehmet S. Eroglu c d, John D. Wallis e, Kevser Topal c, Turan Ozturk a
a Istanbul Technical University, Department of Chemistry, Maslak, 34469 Istanbul, Turkey
b Tubitak, Marmara Research Centre, FI, 41470 Gebze-Kocaeli, Turkey
c Tubitak-UME, 41470 Gebze-Kocaeli, Turkey
d Marmara University, Department of Chemical Engineering, Istanbul, Turkey
e School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, UK
a r t i c l e i n f o
a b s t r a c t
Selective syntheses of 3,4-vinylenedithiathiophenes (VDTTs) and dithieno[2,3-b;20,30-d]thiophenes
(DTTs), having Ph, 4-CH3OC6H4, 4-BrC6H4, 4-NO2C6H4 and 4-(CH3)2NC6H4 groups, were achieved through
the reaction of 1,8-diketone with phosphorus decasulfide (P4S10). The reaction could be shifted between
VDTT and DTT by adding base (sodium bicarbonate) or acid (para-toluenesulfonic acid), respectively, to
the reaction mixture. While the VDTTs were obtained in moderate yields, an important achievement has
been made with the syntheses of the DTTs, obtaining them in higher yields compared with the previous
report. Polymers of the VDTTs, which are the analogues of ethylenedioxythiophene, EDOT, were prepared
using FeCl3. Unfortunately, all attempts for their electropolymerization failed. Spin density calculations
Article history:
Received 10 August 2011
Received in revised form 1 November 2011
Accepted 21 November 2011
Available online 27 November 2011
Keywords:
Vinylenedithiathiophene
Dithienothiophene
revealed that none of the VDTTs had a significant positive spin density at the ‘a’ carbon atoms of the
Phosphorus decasulfide (P4S10
)
thiophene ring. Considering their solubility and functional groups, which could be further derivatized,
they are useful building blocks for the preparation of new organic materials.
Ó 2011 Elsevier Ltd. All rights reserved.
Ethylenedioxythiophene
1. Introduction
p-conjugated systems including polymers. Development of such
useful materials has long been the subject of various research
groups. Examples include introduction of alkyl and alkoxy chains to
carbons 3- and 4- of thiophene 2,14e20 extension of the ethylene
bridge of EDOT 3,2,5,21,22 replacing the bridge with an aromatic or
vinyl group 4,23,24 5,25 respectively, substitution of the oxygens of
EDOT with sulfur 6e10,26ꢀ28 and replacement of thiophene sulfur
of EDOT with selenium.29 Such efforts have contributed to the
understanding of EDOT at the molecular level and to the de-
velopment of new synthetic methodologies.
The presence of alkoxy groups 2 rather than alkyl chains at
carbons 3- and 4- of the thiophene ring was found to cause less
steric hindrance,14e17 which is more apparent with PEDOT. It has
a smaller optical gap and displays remarkable stability. While the
electropolymerization of the monomers, having alkoxy chains and
rings 2, 3 are easier, introduction of an aromatic group 4 makes it
considerably more difficult,23,24 and in the case of a vinyl group 5,25
electropolymerization was not achieved, but with its dimer, it was
successful. In agreement with the experimental results, the radical
cation SOMO coefficients of 4 were reported to be localized on the
dioxane ring, which is also suggested for 5.
Although the discovery of 3,4-ethylenedioxythiophene (EDOT)
goes back to the 1960s,1 it has been in the forefront of the con-
struction of linearly p
-conjugated systems since the 1990s.2e10 This
is particularly due to its exceptional hole injection property, optical
transparency, high conductivity and stability, which have led to its
involvement in various applications, such as anti-static coatings,
electrolytic capacitors and optoelectronic devices for light-emitting
diodes and solar cells.11e13 It was revealed that polymers of EDOT,
polyethylenedioxythiophene (pEDOT) display high thermal stabil-
ity, high conductivity and form highly stable pale blue transparent
films upon doping, while it is a dark blue material in its undoped
state, which enable pEDOT to be highly suitable for electrochromic
applications.
It is obvious that the presence of a strong electron-donating
ethylenedioxy bridge situated between carbons 3- and 4- of the
thiophene ring causes enormous improvements in the properties,
which are more apparent when it is used as a building block for
Even more interesting results were obtained with the sulfur
analogues of EDOT 6e10. While the electropolymerization was
* Corresponding author. Tel.: þ90 212 285 6994; fax: þ212 285 6386; e-mail
address: ozturktur@itu.edu.tr (T. Ozturk).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.11.059

I. Osken et al. / Tetrahedron 68 (2012) 1216e1222
1217
successful with 6e8, which are the analogues having ethyl-
2. Results and discussion
2.1. Synthesis
mercapto chains, 9 and 10 did not yield electropolymerizations.
These results were similarly explained by the fact that 9 and 10 did
not have a significant positive spin density at both carbons 2- and
5- of the thiophene rings.28 On the other hand, unsuccessful elec-
tropolymerization of a monomer does not mean that a similar re-
sult will be obtained with its dimer. The dimer 5 gave a successful
electropolymerization. Additionally, such molecules are also suit-
Synthesis of 11aed was achieved by employing the 1,8-diketone
ring formation reaction disclosed earlier for the syntheses of
substituted DTTs 14aed.38,39 Although, in the previous report,38
DTTs were described as being the sole products of the reaction of
the diketones 13 with phosphorus decasulfide (P4S10) and Law-
esson’s reagent (LR) in refluxing toluene, our in-depth study un-
covered second products, substituted VDTTs 11, which are
analogues of EDOT 1 (Scheme 1). Moreover, an extensive study of
the reaction, applying different reaction conditions, such as
able as versatile building blocks for
p-conjugated systems other
than polymers.6,9e11,18
So far, a limited number of vinylenedithiathiophenes (VDTT)
have appeared in the literature as parts of various systems such
tetrathiafulvalene,30e32 tetrathianaphthalene33 and acenaph-
thodithiin.34 Moreover, the reaction of thienopentathiepin with
dimethyl acetylenedicarboxylate (DMAD) gave the tetra-
substituted VDTT 12.35 In this study, selective syntheses of VDTTs
11aee, as major products along with dithieno[2,3-b;20,30-d]tho-
phenes (DTT) 14aed, applying the method developed by our group,
(1,8-diketone ring formation reaction),36,37 are disclosed. Proper-
ties of the VDTTs and their polymers, pVDTT 24, are reported.
R
R
O
S
O
S
S
S
P4S10,
dioxane or
11a-d
+
S
toluene,
reflux
S
13a-d
R
R
14a-d
Scheme 1. Synthesis of VDTTs 11aed.
refluxing the diketones in toluene or dioxane with P4S10 in the
presence of p-toluenesulfonic acid, sodium bicarbonate and neutral
pH revealed the best conditions for the best yields for DTTs and
VDTTs (Table 1). Refluxing the diketones 13aed in toluene in the
presence of acid gave the best yields for DTTs 14aed in between 53
and 95 %, along with trace of the VDTTs 11aec, except 11d, which
Table 1
Reaction conditions and yields for the synthesis of VDTTs 11aed and DTTs 14aed
Reagent Solvent
Acid/base T, oC
11a (%) 14a (%) Total
conversion (%)
(R ¼ H)
P4S10
Toluene
Dioxane
e
Reflux 26
Trace
30
Reflux 21
36
29
87
e
55
87
30
21
36
46
p-TSA
NaHCO3
e
e
p-TSA
NaHCO3
e
46
e
Reagent Solvent
Acid/base T, oC
11b (%) 14b (%) Total
conversion (%)
(R ¼ MeO)
P4S10
Toluene
Dioxane
e
Reflux 24
Trace
26
Reflux 35
30
27
75
12
10
Trace
10
51
75
38
45
30
67
p-TSA
NaHCO3
e
p-TSA
NaHCO3
57
Reagent Solvent
Acid/base T, o
C
11c (%) 14c (%) Total
conversion (%)
(R ¼ Br)
P4S10
Toluene
Dioxane
e
Reflux
5
37
95
22
Trace
5
42
95
35
20
17
27
p-TSA
NaHCO3
e
Trace
13
Reflux 20
p-TSA
NaHCO3
12
27
Trace
Reagent Solvent
Acid/base T, oC
11d (%) 14d (%) Total
conversion (%)
(R ¼ NO2)
P4S10
Toluene
Dioxane
e
Reflux 40
35
53
e
75
58
56
40
23
68
p-TSA
NaHCO3
e
5
56
Reflux 25
12
15
11
23
p-TSA
NaHCO3
45

1218
I. Osken et al. / Tetrahedron 68 (2012) 1216e1222
formed in a very low yield, 5%. On the other hand, when the reaction
was performed in a basic medium, NaHCO3, VDTTs,11a, c and d were
obtained as the sole products in moderate yields, 27e57 %, except
11b, which was obtained along with the minor product of 14b (10%).
A possible explanation of such a selective synthesis could be
that, in the DTT case, when the reaction was conducted in acid,
similar to the mechanism reported earlier,38 attack from the oxo
group of the diketone 13 to the phosphorus of the protonated P2S5
15 takes place to generate a highly electrophilic centre next to the
oxygen 16, to which an attack from the thiophene ring results in the
formation of a fused thiophene ring through the intermediate 17
(Scheme 2). The DTTs 14aed are obtained after the formation of the
second fused thiophene ring, following a similar mechanism. At
this point, it is important to mention that our previous experience
indicated that refluxing the diketone 13 in toluene without P4S10 or
LR in the absence or presence of acid gave only starting material,
which means that, in this mechanism, the presence of P4S10 is vi-
tal.38 On the other hand, when the reaction is conducted in a basic
environment, the VDTTs 11aed form predominantly, for which two
mechanisms could be suggested (Scheme 3). In the first one, as in
the mechanism suggested above, an attack on the electrophilic
centre 18, this time not from the thiophene ring but from the sulfur
in the chain leads to the formation of the intermediate 1,4-dithiane
19, further rearrangement of which gives the VDTT 11. In the second
mechanism, as it was reported earlier,38a after the oxo groups were
converted to thiones by P4S10, an attack from the thione sulfur 20 to
the electrophilic centre of the other thione can form a nine-mem-
bered ring 21 (Scheme 3). The rearrangement of such a large ring
results in the formation of the 1,4-dithiin ring 22, further rear-
rangement of which leads to the formation of the VDTT 11. More-
over, while at higher temperatures, in refluxing toluene, there is
a tendency of formation of DTT, at lower temperatures, in refluxing
dioxane, tendency goes towards VDTT (Table 1).
Mechanism 1.
S
P
S
S
P
S
O
R
O
R
S
S
S
S
VDTT 11
S
19
S
18
Mechanism 2.
R
R
S
R
R
R
R
S
S
S
H
S
S
-H2S
S
S
S
S
S
22
S
21
S
20
VDTT 11
Scheme 3. Possible reaction mechanisms for the formation of VDTTs 11aed.
SH
HS
S
O
P
S
S
S
O
S
S
P
R
R
S
S
13
15
16
S
S
Scheme 4. Synthesis of VDTT 11e.
SH
P
14
DTT
O
S
R
S
17
Scheme 2. Possible reaction mechanism for the formation of DTTs 14aed.
The nitro group of the VDTT 11d was reduced to the amine 23
with FeCl3/HCl (Scheme 4). As it was clear that this compound was
not stable enough, (the colour of which goes dark brown in a couple
of hours, possibly due to easy oxidizability of para aminophenyl
moiety), the crude product was methylated with methyl iodide
without further purification to give 25% of 11e, starting from 11d. As
the DTTs were prepared earlier and their properties were in-
vestigated separately,38aec this study concentrated on the poly-
merization and explanation of some properties of the VDTTs.
Fig. 1. X-ray structure of 4-MeOC6H4VDTT 11b.
is flexed by 45.6ꢁ about the axis through the two dithiin sulfur
atoms. The CeS bonds in the thiophene ring (1.714(5)e1.727(4) A)
ꢀ
2.2. X-ray studies
are notably shorter than the CeS bonds in the dithiin ring
(1.761(4)e1.782(5) A) in accord with the aromatic character of the
ꢀ
The structure of 11b having a 4-MeOC6H4 group was determined
thiophene ring. The phenyl ring is prevented from fully conjugating
by X-ray crystallography measurements (Fig. 1). The bicyclic system
with the dithiin ring by 1,6-interactions of its ortho hydrogen atoms

I. Osken et al. / Tetrahedron 68 (2012) 1216e1222
1219
with hydrogen and sulfur atoms of the dithiin ring, so that the
torsion about the aryl-dithiin bond is 34ꢁ.
to 300 ꢁC, which could be due to Ar adsorption at the surface. While
the polymers with R¼H 24a, R¼Br 24c and R¼(CH3)2N 24e groups
had nearly the same thermal stability, the polymer with R¼NO2
24d was found to be the least thermally stable one.
Information from the Cambridge Crystallographic Database40
shows that the degree of flexing of this fused dithiin ring is similar
to that observed in 1,4-dithiins which are fused on one or both sides
to the C2eC
bond of a thiophene or benzothiophene (range
3
2.4. Absorption and CV measurements of VDTTs and pVDTTs
44.7e49.1ꢁ),37,41 or in a 1,4-dithiin fused to a 1,3-dithiole-2-thione
(42.6e52.4ꢁ).42 In contrast fusion on both sides to the C3eC4 bond
of a 2,5-dioxo-2,5-dihydrothiophene render the 1,4-dithiin ring al-
most planar, as observed for other dithiins fused to quinones.43
All the VDTTs displayed the characteristic absorption peak of
EDOT at around 290 nm, but they differ from EDOT with additional
absorption peaks around 341 (11a), 344 (11b), 312, 411 (11d), 353
(11c) and 337 (11e) (Fig. 2). Their absorption measurements showed
lower Eg values than EDOT (Table 3). Considering the groups on the
phenyl rings of the VDTTs, while the VDTT 11e, having a dimethyla-
mino, displayed the highest Eg of 3.20 eV, the VDTT 11d with NO2
exhibited the lowest Eg of 2.53 eV, which could be due to extended
electron delocalization over the nitro group. Then, the Eg trend could
be summarized from the most electron donating to the most elec-
tron withdrawing; 11e>11b>11a>11c>11d. On the other hand,
absorption (Fig. 3) and CV (Table 3) measurements of the polymers
24aec indicated that they have Eg values between 3.00e2.61 eV and
2.30e2.00 eV, respectively, which are well above pEDOT. Although
the similar Eg trend, i.e., higher gaps with electron donating groups
and lower gaps with electron withdrawing groups, were observed
with the polymers 24aec, as their gaps close to each other and they
have different molecular weights, it is difficult to make a clear
comment about their Eg trend at this point. n- and p-doping char-
acters of the polymers are listed in Table 3, including their oxidation
and reduction onsets, HOMO and LUMO calculations and absorption
and electrochemical Eg values.
2.3. Polymerization
Unfortunately, all our attempts to electropolymerize the VDTTs
11 were unsuccessful. Such behaviour was also observed with the
thiophene derivatives 5,25 9 and 10,28 spin density calculations of
which indicated that neither of them had significant positive spin
density at the ‘
ization. Similar results were obtained from calculations with the
VDTTs 11, which revealed that their spin densities at the ‘ ’ carbons
of the thiophene rings are either negative or too low for polymer-
ization (see Supplementary data). Then, the polymerization was
successfully performed chemically using FeCl3 in CHCl3 at room
temperature, except 24d, which required reflux, possibly due to its
strong electron withdrawing nitro group (Scheme 5). The average
molecular weights of the resultant polymers, Mw, were determined
by static light scattering technique and listed in Table 2 along with
their dn/dc values.
a’ carbon atoms of the thiophene ring for polymer-
a
R
FeCl3/CH3CN
11a-e
S
S
rt, 24 h
(reflux for 11d)
n
S
24a R= H
24b R= MeO
24c R= Br
24d R= NO2
24e R= (CH3)2N
Scheme 5. Polymerization of VDTTs 11aee.
Thermal gravity analysis of the polymers showed that they lose
weight between 200 and 500 ꢁC, which could be due to their main
chain decomposition (See Supplementary data). This result was
supported by endothermic decomposition peaks obtained from
DSC measurements in the same temperature range. The polymer,
having R¼CH3O group 17b looks the most thermally stable one
among all the polymers, which had only 8% weight-loss at 500 ꢁC
and nearly 80% char residue and 20% weight-loss at 900 ꢁC.
Moreover, its TG curve showed a slow increase in sample weight up
Fig. 2. Absorption spectra of EDOT 1 and VDTTs 11aee in DCM solution.
Oxidation potentials of the VDTTs 11aee were studied by cyclic
voltammetry in DCM containing TBABF4 (Fig. 4). Their oxidation
potentials followed the order of the electron releasing effect of their
substituted groups, i.e., (CH3)2N, CH3O, H, Br, NO2, from the lowest
oxidation potential to the highest one. That is, among all the VDTTs,
the one with strong electron donating group, (CH3)2N, had the
lowest and irreversible oxidation potential with a peak at 0.84 V.
Interestingly, although the VDTT with an electron donating
methoxy group had the second lowest oxidation potential, contrary
to the rest of the VDTTs, it had two quasi-reversible oxidation peaks
at 1.14 and 1.29 V. In line with the electron withdrawing effect of
the substituted groups, while the VDTT, having the strongest
electron withdrawing nitro group, had the highest oxidation
Table 2
The dn/dc and Mw values of the polymers 24aee
Polymers
dn/dc mLgꢀ1
Mw (g molꢀ1
)
Mn (g molꢀ1
)
Mw/Mn
24a
24b
24c
24d
24e
0.230
0.214
0.204
0.220
0.201
277.000
51.000
102.000
215.000
69.000
232.000
39.000
57.000
160.000
32.000
1.197
1.306
1.777
1.344
2.156

1220
I. Osken et al. / Tetrahedron 68 (2012) 1216e1222
Table 3
Spectral and electrochemical data
Monomers
11aee Eg (eV)
CV Monomers
11aee Eox (V)
Polymers
24aee Eg (eV)
Polymers
CV polymers
CV polymers
24aee Ered,onset (V)
HOMOb (eV)
LUMOb (eV)
a
a
24aee Egb [eV]
24aee E.ox,onset (V)
EDOT 1
R¼(CH3)2N
R¼CH3O
R¼H
4.13
3.20
3.14
3.10
3.03
2.53
d
d
d
d
d
0.84
1.14, 1.29
1.32
1.37
1.42
2.98
3.00
2.66
2.74
2.61
2.25
2.30
2.01
2.18
2.00
1.55
1.50
1.13
1.08
1.50
ꢀ0.70
ꢀ0.80
ꢀ0.88
ꢀ1.10
ꢀ0.50
ꢀ5.10
ꢀ5.20
ꢀ5.28
ꢀ5.50
ꢀ4.90
ꢀ2.85
ꢀ2.90
ꢀ3.27
ꢀ3.32
ꢀ2.90
R¼Br
R¼NO2
a
From the red edge of the absorption in DCM (monomers) and THF (polymers).
From the difference between the onsets of the oxidation and reduction processes.
b
applying the reaction of 1,8-diketones with P4S10. Employment of
different reaction conditions, i.e., acidic and basic, and different
solvents, such as toluene and dioxane, affect the selectivity and the
yields of the products. While acidic conditions favour the formation
of the DTT in higher yields, use of a basic medium selectively leads
to the production of VDTT in moderate yields. In agreement with
the spin density calculations of the VDTTs, attempts at their elec-
tropolymerization failed. On the other hand, as they are interesting
building blocks for
p-conjugated systems, their polymers were
prepared with FeCl3. The polymers demonstrated high solubility in
common organic solvents due to their functional groups, and
showed high thermal stability. While the pVDTT (R¼NO2) was the
least thermally stable polymer (starts to decompose around
200 ꢁC), the most thermally stable one was determined to be the
pVDTT with a dimethylamino group, which loses only 8% weight at
500 ꢁC and 20% at 900 ꢁC. The Eg measurements indicated that as
the VDTTs had lower gaps compare with EDOT, their polymers,
pVDTTs, showed higher gaps than pEDOT.
Fig. 3. Absorption spectra of pVDTTs 24aee in THF solution.
Although the materials, VDTT and pVDTT, developed in this
study are not superior compare with EDOT and its polymer pEDOT,
respectively, an interesting series of VDTTs, which could be useful
building blocks for
p-conjugated systems, considering their good
physical properties, solubility and various functional groups they
have, has been disclosed. Additionally, syntheses of a series of
previously reported DTTs were achieved with higher yields.
4. Experimental section
4.1. General
Chemicals were purchased from Acros, Aldrich and Merck and
used without further purification unless otherwise stated. Phos-
phorus decasulfide was purchased from MERCK and used without
further purification. 1H and 13C NMR spectra were recorded on
a Varian model NMR. Proton and carbon chemical shifts are re-
ported in parts per million downfield from tetramethylsilane, TMS.
Mass spectra were recorded on Bruker MICROTOFQ and Thermo
LCQ-Deca ion trap mass instruments. Specific refractive index in-
crement (dn/dc) values were determined using Optilab rEXÔ model
differential refractometer (Wyatt Technology Corporation), equip-
ped with temperature controller (4 ꢁCe50 ꢁC regulated with
Fig. 4. Cyclic voltammograms of VDTTs 11aee (1.0ꢂ10ꢀ3 M) in 0.1 M TBABF4/CH2Cl2
þ/ꢀ0.005 ꢁC), 7.4
mL flow cell volume and high-powered LED light
with
electrodes.
a , Pt working, Pt counter and Ag/AgCl reference
scan rate of 100 mV sꢀ1
source at 690 nm. Polymer concentrations were in the range of
0.5e2.5 mg/mL in THF and the measurements were carried out at
25 ꢁC. All the samples were filtered through 0.20 m filter prior to
use. The GPC set-up (TD-GPC) with an Agilent 1200 model isocratic
pump, four Waters Styragel columns (guard, HR 5E, HR 4, HR 3 and
HR 2), and a Viscotek TDA 302 triple detector (RI, dual laser light
potential at 1.42 V, the VDTTs having no substituted group, R¼H, or
a bromine substituent had quasi-reversible oxidation potentials of
1.32 and 1.37 V, respectively.
3. Conclusion
scattering (LS) (
l
¼670 nm, 90ꢁ and 7ꢁ)) and a differential pressure
viscometer was used to measure the absolute molecular weights in
THF with a flow rate of 0.5 mL/min at 35 ꢁC. All three detectors were
calibrated with a PS standard having narrow molecular weight
Syntheses of
a
series of EDOT analogues, vinyl-
enedithiathiophenes (VDTT), have been achieved along with pre-
viously reported dithienothiophenes (DTT) in higher yields, by
distribution (Mn¼115,000 g/mol, Mw/Mn¼1.02, [ ]¼0.519 dL/g at
h

I. Osken et al. / Tetrahedron 68 (2012) 1216e1222
1221
35 ꢁC in THF, dn/dc¼0.185 mL/g) provided by Viscotek company.
Data were collected by using Omni-Sec version 4.5 software from
Viscotek Company. Thermal analyses (TA) of the polymers were
conducted by PerkineElmer Thermal Analyzer System equipped
with Pyris 6 model thermogravimetry and Jude Differential Scan-
ning calorimetry (DSC) systems. Cyclic voltammograms were
recorded using CH Instrument Model Electrochemical Analyzer. A
three-electrode cell was used in all experiments. UVevis spectra
14a3 as light yellow solids, 11a, mp 101e102 ꢁC; [Found: C, 58.36; H,
2.88. C12H8S3 requires. C, 58.06; H, 3.22%]; Rf (hexane) 0.27; dH
(600 MHz, CDCl3) 6.55 (1H, s), 6.94 (1H, d, J 3 Hz), 7.05 (1H, d, J
3 Hz), 7.35e7.29 (3H, m), 7.55 (2H, dd, J 7.2, 1.6 Hz); dC (150 MHz,
CDCl3) 137.7, 136.6, 130.1, 129.5, 128.7, 128.6, 126.5, 119.0, 118.2,
116.0; m/z (APCIMS) 249 (Mþþ1).
4.2.5. 4-Methoxyphenylvinylenedithiathiophene (11b) and 3,5-bis(4-
methoxyphenyl)dithieno[3,2-b:20,30-d]thiophene (14b). Purification
of the crude product by flash chromatography (3:1 hexane/
dichloromethane) gave the title compounds 11b and 14b38 as white
solids, 11b, mp 135e136 ꢁC; [Found: C, 55.82; H, 3.15. C13H10OS3
requires. C, 56.11; H, 3.59%]; Rf (3:1 hexane/dichloromethane) 0.4;
dH (600 MHz, CDCl3) 7.47 (2H, d, J 8.8 Hz), 7.04 (1H, d, J 3.2 Hz), 6.96
(1H, d, J 3.2 Hz), 6.87 (2H, d, J 8.8 Hz), 6.45 (1H, s), 3.82 (3H, s); dC
(150 MHz, CDCl3) 160.0, 137.5, 131.1, 130.6, 129.5, 128.0, 118.8, 118.0,
114.0, 113.9, 54.6; m/z (APCIMS) 279 (Mþþ1).
were recorded on
spectrophotometer.
a
Hitachi UOO80D model UVevisible
4.1.1. Syntheses of 1,8-diketones (13). Syntheses of the 1,8-
diketones were performed following the method presented in
Ref. 23 with a modification that in place of n-BuLi, in this study, t-
BuLi was used, which resulted in the improvement of the yields to
65e75%.
4.2. General methods for the synthesis of VDTTs and DTTs
using P4S10
4.2.6. 4-Bromophenylvinylenedithiathiophene (11c) and 3,5-bis(4-
bromophenyl)dithieno[3,2-b:20,30-d]thiophene (14c). Purification of
the crude product by flash chromatography (10:1 hexane/
dichloromethane) gave the title compounds 11c and 14c38 as light
orange and orange solids, respectively, 11c, mp 113e114 ꢁC; [Found:
C, 44.35; H, 2.48. C12H7BrS3 requires. C, 44.03; H, 2.14%]; Rf (10:1
hexane/dichloromethane) 0.68; dH (600 MHz, acetone-d6) 6.89 (1H,
s), 7.26 (1H, d, J 3 Hz), 7.34 (1H, d, J 3 Hz), 7.52 (2H, d, J 8.8 Hz), 7.58
(2H, d, J 8.8 Hz); dC (150 MHz, acetone-d6) 117.5, 118.1, 120.0, 122.1,
127.7,128.0,128.3,128.8,131.8,132.1,133.9,136.7; m/z (APCIMS) 329
(Mþþ2).
4.2.1. Neutral reaction. To a solution of P4S10 (0.91 g, 2.04 mmol) in
toluene (100 mL), refluxed for 30 min, was added a hot (around
70 ꢁC) solution of 1,8-diketone 13c (0.5 g, 0.93 mmol), dissolved in
toluene (40 mL), using a pastor pipette. The mixture was refluxed
for 4 h. The solvent was evaporated under reduced pressure and the
mixture was extracted with CH2Cl2 and washed with water. The
organic layer was dried (Na2SO4), filtered and the solvent was
evaporated under reduced pressure. The crude product was puri-
fied by column chromatography to obtain the VDTT 11c and the DTT
14c, as first and second products, respectively.
4.2.7. 4-Nitrophenylvinylenedithiathiophene (11d) and 3,5-bis(4-
nitrophenyl)dithieno[3,2-b:20,30-d]thiophene (14d). Purification of
the crude product by flash chromatography (7:1, 5:1, 3:1, 2:1 and
1:1, successively, hexane/dichloromethane) gave the title com-
pounds 11d and 14d38 as orange powder and white solid, re-
spectively, 11d, mp 106.5e107 ꢁC; [Found: C, 48.91; H, 2.02.
C12H7NO2S3 requires. C, 49.14; H: 2.39%]; Rf (3:1 hexane/EtOAc)
0.69; dH (600 MHz, acetone-d6) 8.27 (2H, d, J 8.8 Hz), 7.87 (2H, d, J
8.8 Hz), 7.35 (1H, d, J 3 Hz), 7.34 (1H, d, J 3 Hz), 7.22 (1H, s); dC
(150 MHz, acetone-d6) 205.0, 147.4, 143.2, 132.1, 127.9, 127.4, 126.8,
124.7, 121.2, 120.3, 119.3, 116.6; m/z (APCIMS) 293 (Mþ).
4.2.2. In the presence of p-TSA. To a mixture of P4S10 (0.91 g,
2.04 mmol) and p-TSA (in equal gram with P4S10), dissolved in
toluene (100 mL) and refluxed for 30 min, was added a hot solution
(around 70 ꢁC) 1,8-diketone 13c (0.5 g, 0.93 mmol), dissolved in
toluene (40 mL), using pastor pipette. The mixture was then
refluxed for 4 h. The solvent was evaporated under reduced pres-
sure and the mixture was extracted with CH2Cl2 and washed with
NaHCO3. The organic layer was dried (Na2SO4), filtered and the
solvent was evaporated under reduced pressure. The crude mate-
rial was sonicated and heated in boiling ethanol (30e35 mL) and
cooled to room temperature. The solid material was filtered to
obtain the DTT 14c. The solvent of the filtrate was evaporated and
the remaining was purified by column chromatography to yield the
VDTTs 11c and the DTTs, if any remained, as first and second
products, respectively.
4.2.8. 4-Aminophenylvinylenedithiathiophene (23). To a solution of
4-NO2C6H4VDTT 11d (0.22 g, 0.76 mmol) dissolved in ethanol
(12 mL) and heated to 95 ꢁC were successively added iron powder
(0.45 g, 8.17 mmol), water (3 mL) and HCl (12 M, 60 mL). The mix-
ture was stirred at the same temperature for 2 h and then filtered as
hot. The solvent was evaporated and the residue was dissolved in
minimum amount of dichloromethane and precipitated in hexane/
dichloromethane (5:1) to obtain the title compound 23. No further
purification was performed as it is found that 23 decomposes on
silica column and on standing. FTIR 3459, 3366 (eNH2).
4.2.3. In the presence of NaHCO3. To a mixture of P4S10 (0.44 g,
0.99 mmol) and NaHCO3 (in equal gram with P4S10), dissolved in
toluene (65 mL) and refluxed for 30 min, was added a hot solution
(around 70 ꢁC) 1,8-diketone 13c (0.24 g, 0.45 mmol), dissolved in
toluene (30 mL), using a pastor pipette. The mixture was refluxed
for 4 h and then the solvent was evaporated under reduced pres-
sure. The mixture was extracted with CH2Cl2 and washed with
water. The organic layer was dried (Na2SO4), filtered and the sol-
vent was evaporated under reduced pressure. The crude product
was purified by column chromatography to obtain the VDTTs 11c
and the DTTs 14c, as first and second products, respectively.
In the case of the reaction of 1,8-diketone 13d with P4S10 in the
presence of both p-TSA and NaHCO3, the mol ratio of P4S10 was kept
as 3.5 times of 13d, and the weights of p-TSA and NaHCO3 were
4.2.9. 4-Dimethylaminophenylvinylenedithiathiophene (11e). To the
mixture of 4-NH2C6H4VDTT 23 (0.21 g, 0.8 mmol) and K2CO3
(0.22 g, 1.59 mmol) in DMF (dry, 10 mL) was added CH3I (100 mL,
1.61 mmol) was added. The mixture was then heated to 115 ꢁC and
stirred for 1 h. The crude product was extracted with CH2Cl2 and
the organic layer was dried over Na2SO4, filtered and the solvent
was evaporated under reduced pressure. Purification of the crude
product by flash chromatography (10:1 hexane/dichloromethane)
gave the title compound 11e (78.0 mg, 25% from 11d) as grey-green
solid, mp 144.5e146 ꢁC; Rf (3:1 hexane/EtOAc) 0.68; dH (600 MHz,
acetone-d6) 7.44 (2H, d, J 8.8 Hz), 7.33 (1H, d, J 3 Hz), 7.23 (1H, d, J
3 Hz), 6.73 (2H, d, J 8.8 Hz), 6.57 (1H, s), 2.97 (6H, s); dC (150 MHz,
acetone-d6) 136.8, 136.0, 130.0, 129.9, 127.0, 119.4, 118.1, 116.3, 112.0,
equal to the weight of P4S10
.
4.2.4. Phenylvinylenedithiathiophene (11a) and 3,5-diphenyldithieno
[3,2-b; 20,30-d]thiophene (14a). Purification of the crude product by
flash chromatography (hexane) gave the title compounds 11a and

1222
I. Osken et al. / Tetrahedron 68 (2012) 1216e1222
111.1, 39.8; HRESIMS: Mþþ1, found 292.0283. C14H13NS3 requires
2. Heywang, G.; Jonas, F. Adv. Mater. 1992, 4, 116e118.
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4.3. General method for the syntheses of the polymers
ꢁ
6. Roncali, J.; Blanchard, P.; Frere, P. J. Mater. Chem. 2005, 15, 1589e1610.
To a solution of FeCl3 (anhydrous, 0.47 g, 2.9 mol) dissolved in
CHCl3 (dry, 30 mL) and stirred for 30 min at room temperature
under nitrogen was added 11b (200 mg, 0.72 mmol) dissolved in
CHCl3 (dry, 25 mL), dropwise. The color change to black was ob-
served immediately. The mixture was stirred at room temperature
overnight. The crude product was filtered through Celite. The sol-
vent was evaporated under reduced pressure and the crude prod-
uct was precipitated from methanol, filtered and washed with cold
methanol. The greenish residue was subjected to Soxhlet extraction
with methanol, acetone and CHCl3 to obtain the polymer free from
the oligomers and the monomers. The material dissolved in CHCl3
was characterized to be the pure polymer 24b (black brown, 94 mg,
42%). Molecular weights of the polymers are listed in Table 1. Fe
content of all the polymers was determined as 3<1000%. All the
polymers showed emission at 313 nm in THF (excited at 265 nm).
Yields: 24a 30%, 24b 28%, 24c 35%, 24d 25%, 24e 40%.
Polymerization of the VDTT 11d was achieved at refluxing
CHCl3, as it was not polymerized at room temperature. Analyses of
the polymers. p(C6H5VDTT): Calculated for C12H6S3 C: 58.50, H:
2.43; Found C: 57.75, H: 1.98. p(CH3OC6H4VDTT): Calculated for
C13H8OS3 C: 56.49, H: 2.92; Found C: 56.02, H: 2.46.
p(BrC6H4VDTT): Calculated for C12H5BrS3 C: 44.32, H: 1.54; Found
C: 44.85, H: 1.73. p(NO2C6H4VDTT): Calculated for C12H5NO2S3 C:
49.46, H: 1.73; Found C: 48.98, H: 1.34. p((CH3)2NC6H4VDTT): Cal-
culated for C14H11NS3 C: 58.12, H: 3.83; Found C: 58.87, H: 4.12.
7. Groenendaal, L.; Jonas, F.; Freitag, D.; Pielartzik, H.; Reynolds, J. R. Adv. Mater
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2007.
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4.4. X-ray
Chem. 2004, 14, 1396e1400.
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Crystal data: C13H10OS3 11b, Mr¼278.39, monoclinic,
ꢁ
¼94.790(4)ꢁ,
ꢀ
a¼20.0230(17), b¼7.6890(7), c¼7.8267(7) A,
b
2002, 4, 607e609.
3
ꢀ
V¼1200.77(18) A , space group P21/c, Z¼4,
r
¼1.54 g cmꢀ3, T¼120 K,
ꢁ
27. Turbiez, M.; Frere, P.; Allain, M.; Gallego-Planas, N.; Roncali, J. Macromolecules
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m
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l
(Mo K
gt; 2
a
)¼0.71073 A,
¼0.59 mmꢀ1, 2621 reflections, 2193 with I
s
(I), R1¼0.051, wR1¼0.130. The structure was solved with
1231e1238.
SHELXS-97 and refined with SHELXL-97.44 The structure is twinned
by 180ꢁ about the reciprocal c axis, with 1:1 ratio between the two
orientations.
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We thank Prof Esma Sezer of ITU for her useful discussions of
electrochemical measurements, the UK National Crystallography
Service, University of Southampton, for a dataset and Istanbul
Technical University, Turkey, The Scientific and Technological Re-
search Council of Turkey (108T941) and Unsped Global Lojistik for
financial supports. We acknowledge NationalCenter for High Per-
formance Computing (UYBHM) for the computer time provided.
Supplementary data
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CV studies, computational method, TG curves and fluorescence
spectra of the polymers, X-ray data for MeOC6H4VDTT (cif file) and
spectral data of the new compounds. Supplementary data related to
this article can be found online at doi:10.1016/j.tet.2011.11.059.
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