Efficient synthesis of 2,5-dicarbonyl derivatives of 3,4-ethylenedithiothiophene (EDTT) via addition-elimination reaction

Article abstract of DOI:10.1016/j.tet.2017.08.026

Derivatives of 3,4-ethylenedithiothiophene (EDTT) are reported starting from tetrabromothiophene. Selective 2,5-dilithiation followed by reaction with a range of aldehydes gives diols as mixtures of diastereomers. Only the 2 and 5 positions in thiophene react leaving the 3,4-bromides for further elaboration. The diols are oxidised to their corresponding diketones using activated MnO₂. Reaction with 1,2-ethanedithiol, by addition-elimination, provides access to novel monomers for the preparation of conjugated copolymers of 3,4-ethylenedithiothiophene (EDTT). A range of these monomers can be attained by applying the synthesis of a series of ketones applicable to further synthesis of π-extended thiophene-based organic semiconductors. Finally, this new route was compared to 3,4-ethylenedioxythiophene (EDOT) dialdehyde derivatives synthesised by an alternative to literature chemistry.

Full text of DOI:10.1016/j.tet.2017.08.026

Accepted Manuscript
Efficient synthesis of 2,5-dicarbonyl derivatives of 3,4-ethylenedithiothiophene (EDTT)
via addition-elimination reaction
Mustafa A-jabbar Al-jumaili, Simon Woodward
PII:
S0040-4020(17)30857-8
10.1016/j.tet.2017.08.026
TET 28920
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 20 April 2017
Revised Date: 4 August 2017
Accepted Date: 14 August 2017
Please cite this article as: Al-jumaili MA-j, Woodward S, Efficient synthesis of 2,5-dicarbonyl derivatives
of 3,4-ethylenedithiothiophene (EDTT) via addition-elimination reaction, Tetrahedron (2017), doi:
10.1016/j.tet.2017.08.026.
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Efficient synthesis of 2,5-dicarbonyl derivatives of
3,4-ethylenedithiothiophene (EDTT) via addition-
elimination reaction
Mustafa A-jabbar Al-jumailia,b and Simon Woodwarda,*
Leave this area blank for abstract info.
a GSK Carbon Neutral Laboratories for Sustainable Chemistry, University of Nottingham, Jubilee Campus, Nottingham NG7 2TU, UK.
b Ministry of Planning in Iraq, Central Organization for Standardization and Quality Control, Baghdad, Al-Jadriya, Iraq.

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Efficient synthesis of 2,5-dicarbonyl derivatives of 3,4-ethylenedithiothiophene
(EDTT) via addition-elimination reaction
Mustafa A-jabbar Al-jumailia,b and Simon Woodwarda,
a GSK Carbon Neutral Laboratories for Sustainable Chemistry, University of Nottingham, Jubilee Campus, Nottingham NG7 2TU, United Kingdom.
b Ministry of Planning in Iraq, Central Organization for Standardization and Quality Control, Iraq, Baghdad, Al-Jadriya
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Derivatives of 3,4-ethylenedithiothiophene (EDTT) are reported starting from
tetrabromothiophene. Selective 2,5-dilithiation followed by reaction with a range of aldehydes
gives diols as mixtures of diastereomers. Only the 2 and 5 positions in thiophene react leaving
the 3,4-bromides for further elaboration. The diols are oxidised to their corresponding diketones
using activated MnO2. Reaction with 1,2-ethanedithiol, by addition-elimination, provides access
to novel monomers for the preparation of conjugated copolymers of 3,4-ethylenedithiothiophene
(EDTT). A range of these monomers can be attained by applying the synthesis of a series of
ketones applicable to further synthesis of π-extended thiophene-based organic semiconductors.
Finally, this new route was compared to 3,4-ethylenedioxythiophene (EDOT) dialdehyde
derivatives synthesised by an alternative to literature chemistry.
Available online
Keywords:
addition-elimination reaction
3,4-ethylenedithiothiophene
1,2-ethanedithiol
organic semiconductors
EDTT
2009 Elsevier Ltd. All rights reserved
.
———
* Corresponding author. E-mail address:
simon.woodward@nottingham.ac.uk (S.
Woodward).

2
Tetrahedron
ACCEPTED MANUSCRIPT
1. Introduction
2. Results and discussion
From their initial mainstream uptake in the early 1980s
oligothiophenes have risen to become one of the most privileged
structures in the organic semi-conducting materials area.1,2 By
appropriate choice of thiophene substituents and microstructure
(e.g. degree of oligomerisation, connectivity, use of additives,
etc.) the resultant materials’ (opto)electrical properties can be
modulated with a high degree of precision. This ability to tune
thiophene-based materials for a specific application has led to
their widespread use in organic photovoltaics (OPV),3 organic
field effect transistors (OFET),4 sensors5 and particularly in
electrochromic/electroluminescent (OLED)6 applications. Such
‘modular-materials’ approaches have created an insatiable
appetite for new thiophene sub-units from materials chemists for
their inclusion into oligo(poly)thiophene structures as evidenced
by the thousands of papers that have appeared in this area in the
last 10 years. In particular, derivatives of 3,4-
ethylenedioxythiophene (EDOT) 1 have proved popular targets
as this monomer is easily polymerised to PEDOT-based
polymers 37 whose formulation with polymer supported
sulfonates (PEDOT-PSS) now forms the backbone of many
transparent electrode technologies. Recently, new thermoelectric
(TE) applications for PEDOT-based materials have emerged,8
potentially allowing direct conversion of waste heat into
electrical power. For optimal TE devices the use of bulk, rather
than thin film, configurations would be preferred (to maximise
power-from-heat recovery). Although the low band gap of
PEDOT-PSS (1.6 eV) favours high electrical conductivity9 (vital
for TE applications) the physical properties of current PEDOT-
PSS co-polymers (solubility, mp) are less favourable for
fabrication of bulk (mm) rather than thin film (~100 nm) devices.
We considered the possibility that derivatives of the sulfur
analogue of EDOT, that is EDTT 2, might prove of utility in
seeking more processible entities. Both EDTT itself and PEDTT
are known versatile components in organic materials chemistry.10
Although the band gap of PEDTT 4 is greater (2.2 eV) than
PEDOT, building in functionality to allow the creation of
vinyligous linkages at the 2,5-postitions of EDTT 2 should allow
band gap reduction, as similar synergies have been noted in
related structures.11 The positioning of suitable groups to promote
solubility and processability of bulk samples is also desirable.
2.1. Synthetic routes to derivatives of EDTT
Our initial study focused on methods to quickly and reliably
attain 2,5-derivatives of 3,4-ethylenedithiothiophene (EDTT) 2
starting
from
the
readily
available
crystalline
tetrabromothiophene 5 (Scheme 2).
Scheme 2. Synthetic route to ketothiophenes. Reagents and
conditions: (i) THF/ nBuLi, RCHO, -78 to -20 °C, 3 h; (ii), MnO2
(10 equiv.), CH2Cl2, 40 °C, 16 h; (iii) 1,2-ethanedithiol (2.2
equiv.), DMF, Na2CO3, 16 h, r.t.
Tetrabromothiophene 5 is easily prepared on large scales by
bromination of thiophene in 73% yield, the HBr by-product is
conveniently quenched by collecting the off-gas into a suitable
water trap. The activated 2,5 positions of 5 are cleanly exchanged
with nBuLi at -78 °C. While rearrangements (the so called
“halogen dance”12) can take place at higher temperatures,
reactive electrophiles are expected to intercept the dilithiated
intermediate cleanly. Relatively few investigations have
employed
this
strategy
but
examples
with:
chlorotrimethylsilane,13 a limited number of aldehydes14 and acyl
chlorides15 are known. However, the reported yields can be poor
in such procedures.
From a practical perspective, addition of the aldehyde at -78 °C
followed by warming to -20 °C affords the maximum yield of 6a-
Scheme 1. The structures of EDOT 1 and EDTT 2 and their
derived polymers PEDOT 3 and PEDTT 4.
e
(35-82%) by minimising organolithium rearrangement.
Compounds 6a-e are attained as a diastereomeric mixture but the
syn and anti diastereomers could be separated by careful column
chromatography. Each of the diastereomeric compounds 6a-e
could be converted into the corresponding ketones 7a-e using
activated MnO2, in refluxing dichloromethane. Simple overnight
reaction is required to attain complete conversion. Ketones 8 are
easily isolated by column chromatography as they appear as
bright yellow bands. The resulting micro-crystalline yellow
solids show spectra in accord with the proposed formulation. The
presence of two keto functions allows potentially many
condensation polymers to be accessed related, in part, to EDTT 2
and PEDTT 4.
Consequently, two main points are investigated in this paper.
Firstly, the synthesis of new polymer precursors based on EDTT
2 that might have lower band gap potentials (essential for organic
materials applications) even if these are based on PEDTT-like
structures. Secondly, the potential structure of the new polymers
should allow for the improved solubility characteristics required
for many applications. Two general strategies are employed here
in to target monomers for new polymers having small HOMO–
LUMO energy differences and good solubility in the different
solvents. The first involves increasing the conjugation of
polymers by inserting an alkenyl unit (C=C) into the structure of
the polymers, to attain a lower band gap. The second strategy
involves strategic placement of alkyl groups whereby the side
chain will increase the polymer solubility and thus improve its
processability.
For comparison, the closest literature method for the synthesis of
EDTT 2 we could identify is shown in Scheme 3.16 This approach
requires two steps from 9 to add the bis-thioether in 86% overall
yield. In our approach (Scheme 2), compounds 8a-c require only

3
one step to install the same thioether. By the reaction of 1,2-
ethanedithiol with compounds 7a-c (in DMF and over 2 days in
the presence of Na2CO3) more modest yields of 71, 50 and 45%
are attained for 8a-c respectively. For further comparison, the
parent 2, and its S,O-analogue, can be also prepared from 9 by
the chemistry of Roncali.17
are attractive species for the future synthesis of many
ACCEPTED MANUSCRIPT
thiophene-based semiconductor polymers. Additionally, we have
reported a new route for the synthesis of the 2,5-diformyl
derivative of 3,4-ethylenedioxythiophene (EDOT), the key
intermediate 14 is obtained using ultra-cheap Na2S.9H2O in just
three steps. Finally, nitrile to formyl conversion proceeds cleanly
in near quantitative yield.
4. Experimental
General. All reagents and solvents were purchased from Sigma-
Aldrich and were used as supplied unless otherwise stated.
Tetrahydrofuran was freshly distilled under argon from
sodium/benzophenone. Aldehydes were distilled before use.
Evaporation of the solvents was completed by rotary evaporation
under reduced pressure. All temperatures refer to those of the
cooling and heating baths used. Cooling of the reactions was
achieved using a Haake DC50-K75 refrigerated circulator. Thin
layer chromatography was performed on foil-backed plates plated
with Merck Silica gel 60 F254. The plates were visualised using
ultraviolet light and basic aqueous KMnO4. Liquid
chromatography was carried out using flash column with specific
solvent systems. All proton spectra were referenced to CDCl3 (δ
= 7.27 ppm) or acetone-d6 (δ = 2.05 ppm) as an internal standard.
All 13C NMR samples were proton-decoupled and referenced to
CDCl3 (δ = 77.0 ppm), acetone-d6 (δ = 29.9 ppm) or DMSO-d6 (δ
= 39.5 ppm). Coupling constants (J) are quoted in Hertz. Infrared
Scheme 3. One comparitive route for EDTT 2.16
2.2. Synthetic routes to derivatives of EDOT
In the last few years 3,4-ethylenedioxythiophene (EDOT) 1 and
its derivatives have become very important commercial
compounds for the preparation of new organic materials.7,18
However, most commercial routes to EDOT use S(CH2CO2Me)2
and rely on late stage (wasteful) decarboxylation of the ester
units. We wondered if a nitrile group was used instead if this
could provide access to 2,5-disubstituted aldehydes closely
related to our diketo-EDTT species 8. This new route to
derivatives of EDOT has been investigated as shown in Scheme
4.
spectra were recorded with
a Varian FTS-7000 FT-IR
spectrometer using (ATR) operating at room temperature. Mass
spectrometry was performed using a Bruker MicroTOF or VG
Micromass AutoSpec spectrometers using electrospray (ESI),
electron impact (EI) ionization modes; theoretical HRMS
molecular weights were determined these instrument’s software.
The starting materials tetrabromothiophene 5, 2,2'-
thiodiacetonitrile 12 and activated MnO2 were prepared by
modifications of literature procedures but are described here for
clarity. Activated MnO2 was prepared by a literature method.21
4.1. Tetrabromothiophene (5)
Compound 5 was prepared by modification of a literature
methods.22 Thiophene (10.6 g, 0.127 mol) dissolved in
chloroform (8 mL) was treated with a solution of bromine (24
mL, 0.46 mol) in chloroform (8 mL) that was added dropwise
over 50 minutes at 0 °C. The resulting dark mixture was stirred
overnight at room temperature, then additional bromine (9.0 mL,
0.17 mol) was then added and the mixture refluxed (70 °C, 57 h).
After the reaction had cooled to room temperature, saturated
potassium hydroxide solution (100 mL) was added over a 10-
minute period and the mixture refluxed again (105 °C, 18 h). The
reaction was stopped and allowed to cool to room temperature.
Scheme 4. Synthetic route for the derivatives of EDOT.
The intermediate 13 is prepared in two steps, the first uses the
ultra-cheap starting material Na2S.9H2O for alkylation with
chloroacetonitrile 11 in DME to yield compound 12 near
quantitatively and in excellent purity which allows its use without
purification. Subsequent reaction of 12 and diethyl oxalate
prepares the potassium salt 13, which is also used directly
without further purification, to access the dinitrile 14 in modest
yield. However, 14 is easily isolated analytically pure after a
simple filtration through a silica plug. Finally, 14 was converted
to the corresponding aldehyde 15 by its treatment with DIBAL-H
at 0 °C in anhydrous toluene. Compound 15 is already recognised
as an important intermediate in the synthesis of thiophene-based
semiconductor polymers.19,20
The 2,3,4,5-tetrabromothiophene
5
was extracted with
dichloromethane, and dried over MgSO4, and solvent removed.
The crude compound was attained as analytically pure colourless
crystalline needles (39.6 g, 99.0 mmol, 78%); m.p. 114-115 °C
(lit.22 116-118 oC); 13C NMR (100 MHz, CDCl3) δC 117.1, 110.4;
MS (EI): m/z 400 (M+), found 395.6467 C4SBr4 requires
395.6448 (79Br). These properties were in accord with the
literature.22
3. Conclusions
4.2. General preparation of the diols (6), representative
procedure,
(6a)
1,1'-(3,4-dibromothiophene-2,5-diyl)bis(1-ethanol)
We have successfully found a new route to homologs of 3,4-
ethylenedithiothiophene (EDTT) 2 having ketone functionalities
at the 2,5-positions. From tetrabromothiophene 5, monomers 8a-
c were obtained in three steps. In addition, the monomers 8a-c

4
Tetrahedron
ACCEPTED MANUSCRIPT
1
To a solution of tetrabromothiophene 5 (1.10 g, 2.75 mmol) in
pentane:EtOAc); m.p. 82-84 °C; H NMR (400 MHz, CDCl3) δH
5.24 (s, 2H, 2 × OH), 4.93 (m, 2H, 2 × CH), 1.64 -1.36 (m, 16H,
2 × CH2CH2CH2CH2), 0.92 (t, J = 7.3 Hz, 6H, 2 × CH3); 13C
NMR (100 MHz, CDCl3) δC 144.2, 108.0, 70.1, 38.7, 31.5, 25.8,
22.8, 14.2; IR(ATR) (cm-1) νmax 3296, 2954, 2921, 2851, 1642,
1464, 1367, 1316, 1248, 1182, 1164, 1058, 971, 927, 769; MS
(ESI): found 442.0007, calcd. for C16H26Br2O2S (79Br) 442.0000.
dry THF (9 mL) under argon, nBuLi (3.77 mL, 1.5 M in hexane,
5.66 mmol) was added dropwise at -78 °C. Excess acetaldehyde
(0.5 mL) was added at -78 °C. The temperature of the mixture
was allowed to warm slowly during 2 h from (-78 to -25 °C). The
reaction was quenched with water (8 mL), extracted with EtOAc,
dried (MgSO4) and evaporated to a brown oil. Flash column
chromatography (7:3 pentane:EtOAc) yielded a colourless solid
(0.696 g, 77%) as a mixture of diastereomers (1:1); Rf values
0.37, 0.44 (7:3 pentane:EtOAc); the m.p. for the mixture of
4.6. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(octan-1-ol) (6e)
1
diastereomers is 96-110 °C; H NMR (400 MHz, acetone-d6) δH
Preparation from tetrabromothiophene 5 (3.00 g, 7.50 mmol,
nBuLi (11.0 mL, 1.5 M in hexane, 16.51 mmol) and n-octanal
(2.40 g, 18.76 mmol). The yellow crude product was purified by
flash column chromatography (9:1 light petroleum:EtOAc) to
yield a yellow oil as a (2:1) mixture of diastereomers (1.46 g,
40%); Rf values 0.30, 0.20 (9:1 light petroleum:EtOAc); 1H NMR
(400 MHz, CDCl3) δH 5.06-5.02 (m, 2H, 2 × CH), 1.83-1.77 (m,
4H, 2 × CH2), 1.31 (m, 20H, 2 × CH2CH2CH2CH2CH2), 0.88 (t, J
= 6.9 Hz, 6H, 2 × CH3) ), the OH signals ~δH2.4 were often not
clearly observed due to exchange;; 13C NMR (100 MHz, CDCl3)
δC 142.8, 110.1, 70.6, 38.1, 31.9, 29.4, 29.3, 25.7, 22.8, 14.2;
IR(ATR) (cm-1) νmax 3331, 2954, 2922, 2853, 1463, 1315, 1168,
1050, 1019, 907, 765; MS (ESI): found 496.0619, calcd. for
C20H34Br2O2S 496.0640.
5.16-5.10 (m, 2H, CH3CH), 4.89-4.88 (m, 2H, OH), 1.46-1.44
(m, 6H, CHCH3); 13C NMR (100 MHz, acetone-d6) δC 146.0,
107.9, 66.9, 24.8; IR(ATR) (cm-1) νmax 3285, 2974, 2925, 1436,
1397, 1368, 1329, 1273, 1177, 1088, 1061, 983, 885, 861, 764;
MS (ESI): found 329.8747, calcd. for C8H10Br2O2S 329.8748
(79Br).
4.3. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(1-propanol) (6b)
Using tetrabromothiophene 5 (0.50 g, 1.25 mmol) in dry THF
(3.2 mL) under argon, nBuLi (1.8 mL, 1.5 M in hexane, 2.75
mmol) was added dropwise at
(0.27 mL, 3.75 mmol) was added at
the mixture was warmed slowly during 3 h from (
The reaction was quenched with water (5 mL) extracted with
EtOAc, dried (MgSO4), and evaporated to a brown crude product
purified by flash column chromatography (8.5:1.5 light
petroleum:EtOAc) yielding a yellow oil (0.215 g, 50%) as
mixture of diastereomers (2:1); Rf values 0.10, 0.07 (17:3 light
-
78 °C. Then excess propanal
78 °C. The temperature of
78 to 65 °C).
-
-
-
4.7. General procedure for oxidation of compounds (6a-e) to
corresponding ketone
Diols 6 (1.41 mmol) were dissolved in dichloromethane (20 mL),
and activated MnO2 (10 molar equivalents) added. The dark
21
1
black suspension was stirred (16 h) at 40-45 °C. Completion of
the reaction was determined by TLC. After filtration through
Celite, the reaction mixture was concentrated in vacuo to afford
the corresponding ketone products as pale solids in about 90%
yield. These products were >98% pure by 1H NMR spectroscopy
and used without further purification.
petroleum:EtOAc); H NMR (400 MHz, CDCl3) δH 4.89 (m, 2H,
CH), 1.73-1.65 (m, 4H, CH2), 1.00 (t, J = 7.3 Hz, 6H), the OH
signals were not observed due to exchange; 13C NMR (100 MHz,
CDCl3) δC 143.9, 108.7, 71.6, 32.0, 10.4; IR(ATR) (cm-1) νmax
3313, 2964, 2930, 2874, 1458, 1378, 1319, 1319, 1171, 1089,
1041, 971, 868; MS (ESI): found 355.9092, calcd. for
C10H14Br2O2S (79Br) 355.9075.
4.8. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(ethan-1-one) (7a)
4.4. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(3-methylbutanol)
(6c)
Prepared from diol 6a (55 mg, 0.16 mmol) to obtain compound
7a as a colourless solid (47 mg, 87%). Rf 0.84 (7:3
o
1
pentane/EtOAc), m.p.168-170 C [lit.20 173-174 °C]; H NMR
(400 MHz, CDCl3) δH 2.74 (s, 6H, 2 × CH3); 13C NMR (100
MHz, CDCl3) δC 189.7, 142.7, 119.4, 29.9; IR(ATR) (cm-1) νmax
2919, 2852, 1649, 1474, 1414, 1353, 1240, 1044, 1029, 949, 870,
802, 666; MS (ESI): found 325.8431, calcd. for C8H6Br2O2S
(79Br) 325.8435.
Preparation from tetrabromothiophene 5 (2.00 g, 5.00 mmol,
nBuLi (6.9 mL, 1.6
M in hexane, 11.0 mmol) and
methylbutyraldehyde (1.29 g, 15.0 mmol). The brown crude
product was purified by flash column chromatography (85:15
light petroleum:EtOAc) to yield a pale yellow solid as a (2:1)
mixture of diastereomers (1.70 g, 82%); Rf values 0.31, 0.15
1
(85:15 light petroleum:EtOAc); m.p. 112-113 °C; H NMR (400
MHz, CDCl3) δH 5.14-5.13 (m, 2H, 2 × CHOH), 2.22 (br, 2H, 2 ×
OH),1.82-1.57 (m, 6H, 2 × CH2, 2 × CH); 1.04-0.96 (m, 12H, 4 ×
CH3); 13C NMR (100 MHz, CDCl3) δC 143.1, 110.0, 68.8, 47.2,
24.9, 23.3, 22.1; IR(ATR) (cm-1) νmax 3220, 2955, 2923, 2868,
1743, 1467, 1384, 1367, 1236, 1180, 1108, 1067, 846, 767, 679,
595; MS (ESI): found 413.9688, calcd. for C14H22Br2O2S
413.9687 (79Br).
4.9. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(propan-1-one) (7b)
Prepared from diol 6b (45 mg, 0.12 mmol) to obtain compound
8b as a colorless solid (35 mg, 0.10 mmol, 82% ) Rf 0.70 (17:3
o
1
light petroleum:EtOAc); m.p.118-120 C; H NMR (400 MHz,
CDCl3) δH 3.10 (q, J = 7.1, 4H, 2 × CH2), 1.24 (t, J = 7.1, 6H, 2 ×
CH3) 13C NMR (100 MHz, CDCl3) δC 192.8, 141.9, 118.9, 35.5,
8.0; IR(ATR) (cm-1) νmax 2983, 2932, 2878, 1651, 1451, 1401,
1379, 1348, 1275, 1184, 1083, 923, 890, 869; MS (ESI): MS
(ESI): found 351.8751, calcd. for C10H10Br2O2S (79Br) 351.8762.
4.5. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(1-hexanol)(6d)
Preparation from tetrabromothiophene 5 (1.00 g, 2.50 mmol,
nBuLi (3.7 mL, 1.5 M in hexane, 5.50 mmol) and n-hexanal (0.9
mL, ca. 0.75 g, 7.5 mmol). The brown crude product was purified
by flash column chromatography (85:15 light petroleum:EtOAc)
to yield of pale yellow solid as (1:1) mixture of diastereomers
4.10. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(3-methylbutan-1-
one) (7c)
Prepared from diol 6c (0.50 g, 1.20 mmol) to obtain compound
7c as a colourless solid (0.44 g, 90%); Rf 0.90 (8.5:1.5 light
(0.80 g, 72%) as colourless solid; Rf
0.66, 0.37 (6:1

5
o
1
petroleum:EtOAc); m.p. 97-99 C; H NMR (400 MHz, CDCl3)
δH 2.92 (d, J = 6.7 Hz, 4H, 2 × CH2), 2.30 (m, 2H, 2 × CH), 1.01
(d, J = 6.7 Hz, 12H, 4 × CH3); 13C NMR (400 MHz, CDCl3) δC
192.0, 141.9, 119.0, 50.5, 25.2, 22.7; IR(ATR) (cm-1) νmax 2956,
2930, 2871, 1649, 1470, 1423, 1393, 1362, 1183, 1098, 1120,
1098, 984, 805, 767; MS (ESI): found 407.9384, calcd. for
C14H18Br2O2S (79Br) 407.9388.
was extracted with ethyl acetate (3 × 4 mL) and the organic
ACCEPTED MANUSCRIPT
layer was then washed with (2 M HCl) until DMF free. The
organic extracts were dried with MgSO4 and concentrated in
vacuo. The crude product was then purified by flash column
chromatography (9:1 light petroleum:EtOAc) giving a pale
yellow solid (75.0 mg, 57%); Rf
0.47 (9:1 light
1
petroleum:EtOAc); m.p. 59-60 °C; H NMR (400 MHz, CDCl3)
δH 3.22 (s, 4H, 2 × CH2), 2.28 (t, J = 7.2 Hz, 4H, 2 × CH2), 1.74-
1.70 (m, 4H, 2 × CH2), 1.34-1.31 (m, 8H, 2 × CH2CH2), 0.91 (t, J
= 7.2, 6H, 2 × CH3); 13C NMR (100 MHz, CDCl3) δC 193.3,
136.4, 133.2, 41.2, 31.5, 26.5, 24.3, 22.6, 14.1; IR(ATR) (cm-1)
νmax 2954, 2933, 2859, 1641, 1463, 1447, 1417, 1366, 1315,
1275, 1247, 1184, 1164, 973, 848, 730; MS (EI): m/z found
370.1095, calcd. for C18H26O2S3 370.1086.
4.11. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(hexan-1-one) (7d)
Prepared from diol 6d (0.52 g, 1.18 mmol) to obtain compound
7c as a colourless solid (0.45 g, 87%); m.p. 71-72 C; Rf 0.87
(8:1 light petroleum:EtOAc); H NMR (400 MHz, CDCl3) δH
o
1
3.05 (t, J = 7.3 Hz, 4H, 2 × CH2), 1.75 (m, 4H, 2 × CH2), 1.37
(m, 8H, 2 × CH2CH2), 0.91 (t, J = 7.3 Hz, 6H, 2×CH3); 13C NMR
(100 MHz, CDCl3) δC 192.5, 141.9, 118.9, 41.9, 31.4, 23.8, 22.6,
14.0. IR(ATR) (cm-1) νmax 2950, 2918, 2867, 1666, 1461, 1426,
1396, 1370, 1246, 1173, 952, 870, 848, 72; MS (ESI): found
435.9707, calcd. for C16H22Br2O2S (79Br) 435.9700.
4.15. 1,1'-(3,4-(ethylenedithio)thiophene-2,5-diyl)bis(octan-1-
one) (8c)
Neat 1,2-ethanedithiol (83 mg, 0.9 mmol) was added to a
solution of 7c (194 mg, 0.39 mmol) and Na2CO3 (104 mg, 0.98
mmol) in dry DMF (4 mL) at room temperature. The mixture was
then stirred for (40 h) until a precipitate formed. The mixture was
extracted with ethyl acetate (4 × 10 mL) and the organic layer
was then washed with (2 M HCl) until DMF free. The extracts
were dried (MgSO4) and concntrated in vacuo. The crude product
was purified by flash column chromatography (9:1 light
petroleum:EtOAc) giving a butter cream yellow solid (75 mg,
4.12. 1,1'-(3,4-dibromothiophene-2,5-diyl)bis(octan-1-one) (7e)
Prepared from diol 6e (0.29 g, 0.58 mmol) to obtain compound
7e as a faint yellow solid (0.23 g, 0.465 mmol, 80 %). Rf 0.74
(9:1 light petroleum:EtOAc); m.p. 48-50 °C; 1H NMR (500 MHz,
CDCl3) δH 3.05 (t, J = 6.7 Hz, 4H, 2 × CH2), 1.76-1.71 (m, 4H, 2
× CH2), 1.38-1.25 (m, 16H, 2 × CH2CH2CH2CH2CH2), 0.88 (t, J
= 6.7 Hz, 6H, 2 × CH3); 13C NMR (125 MHz, CDCl3) δC 192.6,
141.9, 119.0, 41.9, 31.8, 29.2, 29.2, 24.2, 22.7, 14.2; IR(ATR)
(cm-1) νmax 2954, 2916, 2847, 1666, 1559, 1470, 1269, 1222,
1171, 770, 727; MS (ESI): found 492.0300, calcd. for
C20H30Br2O2S (79Br) 492.0300.
1
45%); Rf 0.26 (9:1 light petroleum:EtOAc); m.p. 65-67 °C; H
NMR (400 MHz, CDCl3) δH 3.20 (s, 4H, 2 × CH2), 2.20 (t, J =
7.4 Hz, 4H, 2 × CH2), 1.76-1.69 (m, 4H, 2 × CH2), 1.34-1.29 (m,
16H, 2 × CH2CH2CH2CH2CH2), 0.86 (t, J = 7.4, 6H, 2 × CH3);
13C NMR (100 MHz, CDCl3) δC 193.2, 136.3, 133.1, 41.2, 31.8,
29.3, 29.1, 26.5, 24.5, 22.7, 14.2; IR (ATR) (cm-1) νmax 2953,
2928, 2850, 1646, 1465, 1444, 1418, 1404, 1368, 1354, 1316,
1298, 1250, 1181, 1166, 1099, 1057, 1021, 970; MS (EI): found
426.1721, calcd. for C22H34O2S3 426.1721.
4.13. 1,1'-(3,4-(ethylenedithio)thiophene-2,5-diyl)bis(3-
methylbutan-1-one) (8a)
4.16. 2,2'-Thiodiacetonitrile (12)
Neat 1,2-ethanedithiol (0.84 g, 9.01 mmol) was added slowly to a
solution of (7c) (1.68 g, 4.10 mmol) and Na2CO3 (1.00 g, 9.44
mmol) in dry DMF (20.5 mL) and the mixture was stirred at
room temperature under an atmosphere of argon. After (64 h) the
mixture was extracted with ethyl acetate (3 × 100 mL). The
organic layer was washed with 2 M HCl (3 × 30 mL) and then
dried with MgSO4, filtered and concentrated under reduced
pressure. Purification was achieved by flash column
chromatography (18:1 light petroleum:EtOAc) to afford 8a
(0.991 g, 2.89 mmol, 70%) as yellow microcrystals; Rf 0.26
Solid Na2S.9H2O (10.8 g, 45.01 mmol) was dissolved in DME
(35 mL), and chloroacetonitrile (4.77 g, 63.2 mmol) was then
added. The mixture was allowed to stir at r.t. over (16 h). Water
was added and the compound was extracted from chloroform (3
× 40 mL). The organic layer was dried (MgSO4) and the solvent
removed. Elution through a silica plug (1:1 EtOAc:pentane)
yielded compound 16 as a colorless oil (3.24 g, 28.9 mmol,
1
91%); H NMR (400 MHz, CDCl3) δH 3.57 (s, 4H); 13C NMR
(100 MHz, CDCl3) δC 114.9, 17.5; IR(ATR) (cm-1) νmax 2970,
2929, 2246, 1399, 1174, 922; MS (EI): found 112.0089, calcd.
for C4H4N2S requires 112.0089. The above values are concordant
with literature data.23
1
(18:1 light petroleum:EtOAc); m.p. 99-100 °C; H NMR (400
MHz, CDCl3) δH 3.21 (s, 4H, 2 × CH2), 2.69 (d, J = 6.7 Hz, 4H, 2
× CH2CO), 2.36-2.28 (m, 2H, 2 × CH), 1.00 (d, J = 6.7 Hz, 12H,
4 × CH3); 13C NMR (100 MHz, CDCl3) δC 192.9, 136.4, 133.5,
50.1, 26.5, 25.7, 22.8; IR(ATR) (cm-1) νmax 2951, 2871, 1728,
1654, 1442, 1411, 1398, 1362, 1278, 1183, 1035, 956, 917, 880,
688; MS (EI): found 342.0785, calcd. for C16H22O2S3 342.0782.
Anal. Calcd. for C16H22O2S3 C: 56.10; H, 6.47 % found C: 55.97,
H: 6.78%.
4.17. Potassium 2,5-dicyanothiophene-3,4-bis(olate) (13)
To dry tBuOK (8.0 g, 71.3 mmol) in dry THF (95 mL), a solution
of 12 (4.00 g, 35.6 mmol) in THF (43 mL) was added dropwise
at 0 °C. The mixture was stirred for 5 minutes and then added a
solution of diethyl oxalate (5.21 g, 35.66 mmol) in dry THF (40
mL) at 0 °C. After 30 minutes stirring at 0 °C the precipitate was
collected by vacuum filtration and washed with diethyl ether and
THF to obtain 13 as a brown powder (7.26 g, 84%); 13C NMR
(100 MHz, DMSO-d6) δC 174.9, 122.8, 65.7; IR (ATR) (cm-1)
νmax 2168, 1712, 1518, 1315, 1229, 1019, 764, 592. The
compound was used as obtained directly.
4.14. 1,1'-(3,4-(ethylenedithio)thiophene-2,5-diyl) bis(hexan-1-
one) (8b)
Neat 1,2-ethanedithiol (83.0 mg, 0.89 mmol) was added to a
solution of 7b (156 mg, 0.36 mmol) and Na2CO3 (94 mg, 0.89
mmol) in dry DMF (1.8 mL) and the mixture was stired at room
temperature under an atmosphere of argon (40 h). The mixture

6
Tetrahedron
4. (a) Nielsen, C. B.; McCulloch, I.; Prog. Poly. Sci. 2013, 38, 2053-2069.
4.18. 3,4-Ethylenedioxythiophene-2,5-dicarbonitrile (14)
ACCEPTED MANUSCRIPT
(b) Olivier, Y.; Niedzialek, D.; Lemaur, V.; Pisula, W.; Müllen, K.;
Koldemir, U.; Reynolds, J. R.; Lazzaroni, R.; Cornil, J.; Beljonne, D.;
Adv. Mater. 2014, 26, 2119-2136.
5. Huynh, T.-P.; Sharma, P. S.; Sosnowska, M.; D'Souza, F.; Kutner, W.;
Prog. Poly. Sci. 2015, 47, 1-25.
6. (a) Beaujuge, P. M.; Reynolds, J. R.; Chem. Rev. 2010, 110, 268-320. (b)
Beaujuge, P. M.; Amb, C. M.; Reynolds, J. R.; Acc. Chem. Res. 2010, 43,
1396-1407. (c) Grimsdale, A. C.; Chan, K. L.; Martin, R. L.; Jokisz, P.
G.; Holmes, A. B.; Chem. Rev. 2009, 109, 897-1091.
7. Overviews of PDOT: (a) Groenendaal, L. B.; Jonas, F. H.; Freitag, D.;
Pielartzik, H.; Reynolds, J. R.; Adv. Mater. 2000, 12, 481-494. (b)
Roncali, J.; Blanchard, P.; Frère, P.; J. Mater. Chem. 2005, 15, 1589-
1610. (c) Kirchmeyer, S.; Reuter, K.; J. Mater. Chem. 2005, 15, 2077-
2088.
8. For overviews of this area see: (a) Taroni, P. J.; Hoces, I.; Stingelin, N.;
Heeney, M.; Bilotti, E.; Isrl. J. Chem. 2014, 54, 534-552. (b) Cowen, L.
M.; Atoyo, J.; Carnie, M. J.; Baran, D.; Schroeder, B. C.; ECS J. Solid
State Sci. Technol. 2017, 6, N3080-N3088 and citations thereof.
9. For example, electrical conductivities >4000 S cm-1 are known: Kim, N.;
Kee, S.; Lee, S. H.; Lee, B. H.; Kahng, Y. H.; Jo, Y.-R.; Kim, B.-J.; Lee,
K.; Adv. Mater. 2014, 26, 2109.
10. (a) Wang, C.; Schindler, J. L.; Kannewurf, C. R.; Kanatzidis, M. G.;
Chem. Mater. 1995, 7, 58-68. (b) Turbiez, M.; Frère, P.; Allain, M.;
Gallego-Planas, N.; Roncali, J.; Macromolecules 2005, 38, 6806-6812.
11. For heteroatom and vinyligous modifications see for example: (a)
Poverenov, E.; Sheynin, Y.; Zamoshchik, N.; Patra, A.; Leitus, G.;
Perepichka, I. F.; Bendikov, M.; J. Mater. Chem. 2012, 22, 14645-14655.
(b) Montcada, N. F.; Domínguez, R.; Pelado, B.; De La Cruz, P.;
Palomares, E.; Langa, F.; J. Mat. Chem. A 2015, 3, 11340-11348. (c)
Burrezo, P. M.; Pelado, B.; Ortiz, R. P.; De La Cruz, P.; Navarrete, J.
T. L.; Langa, F.; Casado, J.; Chem. Eur. J. 2015, 21, 1713-1725. (d)
Akoudad, S.; Frere, P.; Mercier, N.; Roncali, J.; J. Org. Chem. 1999,
64, 4267-4272.
Under an argon atmosphere potassium salt 13 (0.50 g, 2.06
mmol) was dissolved in anhydrous DMF (1.5 mL) at room
temperature, and dry potassium carbonate (0.11 g, 0.83 mmol)
added followed by tetrabutylammonium bromide (35 mg, 0.10
mmol). The mixture was heated to 135 °C and 1,2-dichloroethane
(0.41 g, 4.13 mmol) added dropwise. After stirring at 135 °C (5
h) the reaction was stopped and allowed to cool down. The
mixture was extracted with ethyl acetate (3 ×10 mL), washed
with 5% w/w LiCl(aq) solution (3 ×10 mL) and the combined
organic extracts dried (MgSO4) and concentrated in vacuo to
afford the crude product. Filtering through a silica plug with a
dichloroethane wash yielded, on removal of the solvent, 14 (0.13
g, 35%) obtained as
a colourless solid, Rf 0.68 (1:1
EtOAc:hexane) 1H NMR (400 MHz, CDCl3): δH 4.42 (s, 4H, 2 ×
CH2), 13C NMR (100 MHz, CDCl3): δC 147.8, 110.6, 91.3, 65.2.
IR (ATR) (cm-1) νmax 2946, 2215, 1632, 1504, 1449, 1078, 914,
843, 806 cm–1. MS (EI): found 191.9988, calcd. for
C8H4N2O2S191.9993.
4.19. 3,4-Ethylenedioxythiophene-2,5- dicarbaldehyde (15)
A solution of DIBAL-H (1.08 mL, 1.2 M 20% wt. in toluene)
was added dropwise at 0 °C to a solution of 14 (100 mg, 0.52
mmol) in dry toluene (5.2 mL). The reaction was stirred (30
minutes) at 0 °C until the starting material was consumed as
judged by TLC analysis. The reaction mixture was quenched
with (1 M, HCl) and extracted with ethyl acetate (3 × 10 mL) and
dried (MgSO4), the solvent was evaporated to yield the desired
dialdehyde 15 (83 mg, 80%) as a tan brown solid. Rf 0.64
12. Schnurch, M.; Spina, M.; Khan, A. F., Mihovilovic, M. D.; Stanetty, P.,
Chem. Soc. Rev., 2007, 36, 1046-1057.
13. Pang, H.; Skabara, P. J.; Gordeyev, S.; McDouall, J.; Coles, S. J.;
Hursthouse, M. B.; Chem. Mater. 2007, 19, 301-307.
14. (a) Benz, S.; Macchione, M. , Verolet, Q. , Mareda, J. ,Sakai, Naomi N. ,
Matile, S. , J. Am. Chem. Soc. 2016, 138, 9093-9096. (b) He, M.; Zhang,
F.; J. Org. Chem. 2007, 72, 442-451.
15. (a) Lin, H.; Xu, W.; Zhu, D. J. Mat Chem., 20, 2010, 884-890. (b) Tùng,
D. T.; Tuân, D. T.; Rasool, N.; Villinger, A.; Reinke, H.; Fischer, C.;
Langer, P.; Adv. Synth. Catal. 2009, 351, 1595–1609.
1
(EtOAc); H NMR (400 MHz, CDCl3) δH 10.04 (s, 2H, 2 ×
CHO), 4.45 (s, 4H, 2 × CH2); 13C NMR (100 MHz, CDCl3) δC
181.0, 147.4, 124.2, 65.0; IR(ATR) (cm-1) νmax 2953, 2922, 2851,
1662, 1643, 1260, 1230; MS (EI): found 197.9987, calcd. for
C8H6O4S 197.9987. These values are consistent with published
literature.11d
16. Chen, S.; Lu, B.; Duan, X.; Xu, J.; J. Poly. Sci. 2012, 50, 1967-1978.
17. (a) Blanchard, P.; Jousselme, B.; Frère, P.; Roncali, J.; J. Org. Chem.
2002, 67, 3961-3964. (b) Blanchard, P.; Cappon, A.; Levillain, E.;
Nicolas, Y.; Frère, P.; Roncali; J.; Org. Lett. 2002, 4, 607-609.
18. Groenendaal, L.; Zotti, G.; Aubert, P.-H.; Waybright, S. M.; Reynolds, J.
R.; Adv. Mater. 2003, 15, 855-879.
19. Mohanakrishnan, A. K.; Hucke, A.; Lyon, M. A.; Lakshmikantham, M.
V.; Cava, M. P. Tetrahedron 1999, 55, 11745-11754.
20. Present attempts to prepare the 3,4-ethylenedithio analogue of 15 (i.e. 8,
R = H) are complicated by dithioacetal formation and other competing
reactions.
21. Fuchs, P. L.; Charette, A. B.; Rovis, T.; Bode, J. W. , Wiley, Essential
Reagents for Organic Synthesis, Wiley, New York ISBN: 978-1-119-
27830-6, 2016, pp. 250.
22. (a) Araki, K.; Endo, H.; Masuda, G.; Ogawa, T.; Chem. Eur. J. 2004, 10,
3331-3340. (b) Honciuc, A.; Metzger, R. M.; Gong, A.; Spangler, C. W.;
J. Am. Chem. Soc. 2007, 129, 8310-8319.
Acknowledgements
One of us (MA) would like to thank The Higher Committee for
Education Development in Iraq (HCED-Iraq) for the providing of
a scholarship. The University of Nottingham is acknowledged for
additional support.
Supplementary data
Supplementary data associated with this article can be found in
the online version, at http://
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