Synthesis of 1-amino-2,5-di(2-thienyl)benzenes as potential monomers for the preparation of hybrid polythiophene anionic sensors

Article abstract of DOI:10.1007/s11172-012-0042-5

A convenient method for the synthesis of 1-amino-2,5-di(2-thienyl)benzenes was proposed. The method involves in situ generation of aryne intermediates from 1-halo-2,5-di-(2-thienyl)benzenes in the presence of strong bases followed by reactions of the aryn

Full text of DOI:10.1007/s11172-012-0042-5

Russian Chemical Bulletin, International Edition, Vol. 61, No. 2, pp. 303—307, February, 2012
303
Synthesis of 1ꢀaminoꢀ2,5ꢀdi(2ꢀthienyl)benzenes as potential monomers
for the preparation of hybrid polythiophene anionic sensors*
G. V. Zyryanov,a,b I. S. Kovalev,a I. N. Egorov,a V. L. Rusinov,a and O. N. Chupakhina,b
aB. N. El´tsin Ural Federal University,
19 ul. Mira, 620002 Ekaterinburg, Russian Federation.
Fax: +7 (343) 375 4501. Eꢀmail: gvzyryanov@gmail.com
bI. Ya. Postovsky Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences,
20 ul. S. Kovalevskoi, 620219 Ekaterinburg, Russian Federation.
Fax: +7 (343) 374 1189. Eꢀmail: chupakhin@ios.uran.ru chupakhin@ios.uran.ru
A convenient method for the synthesis of 1ꢀaminoꢀ2,5ꢀdi(2ꢀthienyl)benzenes was proꢀ
posed. The method involves in situ generation of aryne intermediates from 1ꢀhaloꢀ2,5ꢀdiꢀ
(2ꢀthienyl)benzenes in the presence of strong bases followed by reactions of the arynes with
polyfunctional primary and secondary amines. The products obtained in 75—85% yields are
promising monomers for the preparation of polythiophene anionic sensors. Polymerization of
dibrominated 1ꢀpiperidinoꢀ2,5ꢀdi(2ꢀthienyl)benzene gave the corresponding poly[(bithioꢀ
phenediyl)(phenylene)].
Key words: amination, aryne, poly[(bithiophenediyl)(phenylene)], crossꢀcoupling.
In the last three decades, polythiophenes have found
wide use as active components of transistors,1 electroluꢀ
minescent devices,2 solar panels,3 photochemical resisꢀ
tors,4 nonlinear optic devices,5 solar cell components,6
diodes,7 and chemical sensors.8 Polythiophenes themselves
and polythiopheneꢀbased materials tend to be applied in
two main ways. In static polymer materials prepared by
common methods, the conducting properties of polyꢀ
thiophenes9 are employed with retention of other properꢀ
ties of polymer materials. In dynamic materials, an optiꢀ
cal or electrical signal is altered by applying an electric
potential or an external stimulus. In this context, the synꢀ
thesis of anionic sensors based on polythiophenes or hyꢀ
brid polymers containing aromatic and heteroaromatic
(thiophene) fragments is of particular interest. Organic
and inorganic anions penetrate into the environment via
food additives,10 synthetic detergents,11 drugs,12 organic
fertilizers,13 etc. Monitoring of the level of organic and
inorganic anions in human blood is a promising tool for
early diagnostics of serious diseases.14
anionic sensors. Having this in mind, here we tried to
introduce cyclic and acyclic amino groups into 1,4ꢀdiꢀ
(2ꢀthienyl)benzene for subsequent polymerization of the
resulting monomers.
We employed the Buchwald—Hartwig amination17 for
direct crossꢀcoupling of 1ꢀiodoꢀ or 1ꢀbromoꢀ2,5ꢀdi(2ꢀthiꢀ
enyl)benzenes with amines as the most promising methꢀ
od. To do this, we obtained 1ꢀiodoꢀ2,5ꢀdi(2ꢀthienyl)ꢀ
benzene (1a) according to a known procedure.18 Howevꢀ
er, its attempted modification with an amino function
under standard amination conditions led only to 1,4ꢀdi(2ꢀ
thienyl)benzene 2 as a major product (Scheme 1). 1ꢀBromoꢀ
2,5ꢀdi(2ꢀthienyl)benzene (1b) reacted in a similar way.
Based on the mechanism postulated for this reaction,19
one can assume that the steric hindrances at a palladium
intermediate preclude subsequent addition of an amine
and hence favor the ꢀtransfer of the hydrogen atom
(ꢀH shift), yielding dehalogenated product 2 (Scheme 2).
While investigating possible causes of such low reacꢀ
tivities of compounds 1a,b, we found that heating of comꢀ
pound 1b with piperidine in toluene in the presence of
strong bases (KOBut or NaNH2), which are not common
bases used under the conditions of the Buchwald reacꢀ
tion, and a decreased amount of the catalyst Pd(OAc)2
(0.2 mol.%) unexpectedly gives amination product 3a in
50—65% yields, product 2 being formed only in trace
amounts (Scheme 3). Moreover, the yield of compound
3a in the absence of the catalyst increased to 85%. We
assumed that a strong base favors the in situ formation of
an aryne intermediate that reacts with piperidine to give
In addition, cationic complexes of polythiophenes have
been used for detection of anions (e.g., iodide anions in
water15). At the same time, cyclic and acyclic polyfuncꢀ
tional amines are very common anionic receptors for orꢀ
ganic and inorganic anions.16
Therefore, by combining polyfunctional amines and
polythiophenes, one could design efficient polyfunctional
* Dedicated to Academician of the Russian Academy of Sciences
V. N. Charushin on the occasion of his 60th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 302—306, February, 2012.
1066ꢀ5285/12/6102ꢀ303 © 2012 Springer Science+Business Media, Inc.

304
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 2, February, 2012
Zyryanov et al.
Scheme 1
i. Base/P ligand, solvent.
Scheme 2
Scheme 3
product 3a. To verify this assumption, we carried out the
above reaction in the presence of an excess of anthracene,
a known trap for aryne intermediates, and obtained 3´,6´ꢀdiꢀ
(2ꢀthienyl)ꢀ9,10ꢀdihydroꢀ9,10ꢀ[2´,1´]benzoanthracene
(triptycene)20 4 in 35% yield as a result of the Diels—Alder
reaction of aryne with anthracene (Scheme 3).
To find out whether it is possible to obtain aminoꢀ
containing thienylphenylene polymers, we functionalized
compound 3a by roomꢀtemperature bromination of its
thiophene moieties with Nꢀbromosuccinimide in DMF.
The Yamamoto polymerization21 of the resulting diꢀ
bromide 5 by heating in toluene in the presence of equimoꢀ
lar amounts of bis(cyclooctadiene)nickel(0) (Ni(COD)2),
cyclooctaꢀ1,5ꢀdiene, and 2,2´ꢀbipyridine gave aminoꢀ
functionalized poly[(bithiophenediyl)(phenylene)] 6
(Scheme 4).
Further optimization of the conditions for the syntheꢀ
sis of compounds 3 revealed that 1ꢀchloroꢀ2,5ꢀdi(2ꢀthiꢀ
enyl)benzene (1c) is their most convenient precursor,
which can be prepared in 80% yield by the Stille crossꢀ
coupling22 of 1ꢀchloroꢀ2,5ꢀdiiodobenzene with 2ꢀ(triꢀ
methylstannyl)thiophene (Scheme 5).
i. Toluene, 140 C.
Heating of compound 1c with amines in toluene in the
presence of KOBut or NaNH2 gave amination products
3a—d in high yields (see Scheme 5, Table 1). Note that
both primary and secondary polyfunctional amines can be
used in this reaction.
To sum up, we demonstrated that sterically hindered
1ꢀhaloꢀ2,5ꢀdi(2ꢀthienyl)benzenes can be aminated with
primary or secondary polyfunctional amines via the aryne
mechanism. We obtained 1ꢀaminoꢀ2,5ꢀdi(2ꢀthienyl)ꢀ

Synthesis of 1ꢀaminoꢀ2,5ꢀdi(2ꢀthienyl)benzenes
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 2, February, 2012
305
Scheme 4
i. DMF, 0—25 C; ii. Toluene, 90 C.
Scheme 5
tified by physicochemical methods. We found that 1ꢀpipꢀ
eridinoꢀ2,5ꢀdi(2ꢀthienyl)benzene 3a can be polymerized
into an aminoꢀfunctionalized thienylphenylene polymer.
Experimental
The starting materials and Ni(COD)2 were prepared accordꢀ
ing to known procedures; the other starting materials were used
as purchased. TLC analysis was performed on Silica gel 60F254
plates (Merck); spots were visualized under UV light. Products
were purified by column chromatography on Silica gel 60 (Merck).
1H NMR spectra were recorded on a Bruker WHꢀ250 instruꢀ
ment. Melting points were determined on a Boetius instrument.
Mass spectra of polymer 6 were measured on a MicrOTOFꢀQ II
mass spectrometer (Bruker Daltonics, Bremen, Germany) (ESI)
equipped with a sixꢀport valve and a kd Scientific system for
direct inlet probe (flow rate 180 L h). The mass spectrometer
was controlled by the micrOTOFcontrol 2.3 patch 1 and HyStar
3.2 software (Bruker Daltonics). The operating parameters of
the mass spectrometer were as follows: rated resolution 17 500,
positive ion mode, m/z scan range 50—8000 Da, ion source capꢀ
illary voltage 4500 V, glass capillary outlet voltage 166 V, sprayꢀ
ing gas pressure 0.8 bar, drying gas flow rate 4 L min–1, gas
heater temperature 250 C, averaging setting 3, summation setꢀ
ting 5000 (corresponding to a spectrum per second), ion travel
time 70 s, and radio frequency of the hexapole 100 Vpp.
i. Pd(PPh3)4, toluene, 110 C; ii. Base, toluene, 140 C.
benzenes in high yields as monomers for the synthesis of
polythiophene anionic receptors. The in situ generated
aryne intermediate was isolated as its derivative 4 and idenꢀ
Table 1. Synthesis of compounds 3a—d
Amine
Base
Product
Yield (%)
KOBut
NaNH2
3a
3a
55
85
1ꢀChloroꢀ2,5ꢀdi(2ꢀthienyl)benzene (1c). 2ꢀ(Trimethylstanꢀ
nyl)thiophene (0.750 g, 3 mmol) and Pd(PPh3)4 (0.110 g,
0.10 mmol) were added under argon to a solution of 1ꢀchloroꢀ
2,5ꢀdiiodobenzene23 (0.364 g, 1 mmol) in dry toluene (25 mL).
The reaction mixture was stirred at 110 C for 24 h. On cooling,
silica gel (10 g) was added and the mixture was stirred and conꢀ
centrated under reduced pressure. The resulting silica gel was
transferred on top of a column packed with silica gel. The prodꢀ
uct was separated by column chromatography with 30% CH2Cl2
in hexane as an eluent and recrystallized from MeOH—CH2Cl2
(1 : 1). The yield of compound 1c was 85%, colorless crysꢀ
KOBut
NaNH2
3b
3b
75
86
KOBut
3c
80
1
tals, m.p. 75 C. H NMR (250 MHz, CDCl3), : 7.75 (s, 1 H,
KOBut
NaNH2
3d
3d
85
85
Ph); 7.54—7.59 (m, 2 H, Ph); 7.42—7.46 (m, 2 H, CHthiophene);
7.34—7.38 (m, 2 H, CHthiophene); 7.12—7.16 (m, 2 H, CHthiophene).
Found (%): C, 60.80; H, 2.99. C14H9ClS2. Calculated (%):
C, 60.75; H, 3.28.

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Zyryanov et al.
1,4ꢀDi(2ꢀthienyl)benzene (2). The catalyst Pd(OAc)2 or
N,NꢀBis(2ꢀaminoethyl)ꢀN´ꢀ[2,5ꢀdi(2ꢀthienyl)phenyl]ethaneꢀ
1,2ꢀdiamine 3d. Yield 80% (A), oil. 1H NMR (250 MHz, CDCl3),
: 7.30—7.39 (m, 2 H, Ph); 6.99—7.03 (m, 1 H, Ph); 7.24—7.28
(m, 2 H, CHthiophene); 7.19—7.20 (m, 1 H, CHthiophene); 7.13—7.16
(m, 1 H, CHthiophene); 7.09—7.11 (m, 1 H, CHthiophene); 6.90
(br.s, 1 H, CHthiophene); 3.25 (t, 2 H, CH2, J = 6.0 Hz); 2.76
(t, 2 H, CH2, J = 6.0 Hz); 2.48 (t, 4 H, 2 CH2, J = 6.0 Hz); 2.48
(t, 4 H, 2 CH2, J = 6.0 Hz); 1.17 (br.s, 4 H, 2 NH2). 13C NMR
(75 MHz, CDCl3), : 146.1, 144.8, 140.6, 135.4, 131.4, 127.8,
127.5, 126.2, 125.6, 124.6, 123.1, 119.2, 114.7, 108.2, 57.0, 53.5,
41.3, 39.9. Found (%): C, 61.86; H, 7.02; N, 14.44. C20H26N4S2.
Calculated (%): C, 62.14; H, 6.78; N, 14.49.
3´,6´ꢀDi(2ꢀthienyl)ꢀ9,10ꢀdihydroꢀ9,10[1´,2´]ꢀbenzenoanthraꢀ
cene (4). Potassium tertꢀbutoxide (1.12 g, 10 mmol) and anꢀ
thracene (1.0 g, 5.60 mmol) were added under argon to a soluꢀ
tion of compound 1 (X = I, Br, or Cl) (0.5 mmol) in dry toluene
(30 mL). The reaction mixture was stirred at 140 C for 22 h and
diluted with water (10 mL). The product was extracted from the
organic layer with ethyl acetate (3×10 mL). The combined exꢀ
tracts were washed with water (2×10 mL) and brine (10 mL),
dried over CaCl2, filtered, and evaporated to dryness under reꢀ
duced pressure. The product was separated as a colorless precipꢀ
itate by column chromatography on silica gel with 10% acetone
in hexane as an eluent. Yield 32%, m.p. >250 C. 1H NMR
(250 MHz, CDCl3), : 7.48—7.50 (m, 2 H, Ph); 7.39—7.42
(m, 4 H, C6H4), 7.24—7.26 (m, 2 H, CHthiophene); 7.19—7.21
(m, 2 H, CHthiophene); 7.05 (m, 2 H, CHthiophene); 7.02—7.05
(m, 4 H, C6H4); 6.03 (s, 2 H, CH). 13C NMR (75 MHz, CDCl3),
: 145.2, 144.1, 141.6, 130.0, 127.5, 126.8, 126.8, 125.8, 125.3,
123.8, 50.8. Found (%): C, 80.59; H, 4.24. C28H18S2. Calculatꢀ
ed (%): C, 80.34; H, 4.33.
1ꢀ[2,5ꢀBis(5ꢀbromoꢀ2ꢀthienyl)phenyl]piperidine 5. A solution
of freshly recrystallized 1ꢀbromosuccinimide (0.400 g, 2.27 mmol)
in dry DMF (5 mL) was added dropwise under argon at –20 C
to a solution of compound 3a (0.325 g, 1 mmol) in dry DMF
(10 mL). The reaction mixture was stirred at –20 C for 1 h and
at room temperature for 12 h and poured into cooled water
(50 mL). The product was extracted with ethyl acetate (2×30 mL).
The combined extracts were dried with Na2SO4 and concentratꢀ
ed on a rotary evaporator. The residue was purified by column
chromatography on silica gel with 10% ethyl acetate in hexane
as an eluent. Compound 5 was isolated as a colorless crystalline
powder, m.p. 112 C (decomp.). 1H NMR (250 MHz, tetrachloꢀ
roethaneꢀd2), : 7.41—7.44 (m, 2 H, Ph); 7.30 (s, 1 H, Ph); 7.17
Pd2(dba)3 (2—5 mol.%), the P ligand (10 mol.%), a base
(3 mmol), and an appropriate amine (3 mmol) were added under
argon to a solution of 1ꢀiodoꢀ or 1ꢀbromoꢀ2,5ꢀdi(2ꢀthienyl)ꢀ
benzene 1 (0.5 mmol) in dry toluene (10 mL). The reaction
mixture was stirred at 140 C for 22 h and diluted with water
(10 mL). The product was extracted from the organic layer with
ethyl acetate (3×10 mL). The combined extracts were washed
with water (2×10 mL) and brine (10 mL), dried over CaCl2,
filtered, and evaporated to dryness under reduced pressure. The
product was separated by column chromatography on silica gel
with 10% acetone in hexane as an eluent. The physicochemical
and spectroscopic characteristics of the resulting colorless preꢀ
cipitate agree with the literature data.24
Synthesis of compounds 3a—d (general procedure). Potassiꢀ
um tertꢀbutoxide (1.12 g, 10 mmol) (method A) or sodium amide
(0.390 g, 10 mmol) (method B) and an appropriate amine
(5 mmol) were added under argon to a solution of 1ꢀchloroꢀ2,5ꢀ
di(2ꢀthienyl)benzene (1c) (0.276 g, 1 mmol) in dry toluene
(20 mL). The reaction mixture was stirred at 140 C for 22 h and
diluted with water (10 mL). The product was extracted from the
organic layer with ethyl acetate (3×10 mL). The combined exꢀ
tracts were washed with brine (2×10 mL), dried over CaCl2,
filtered, and evaporated to dryness under reduced pressure.
The product as a colorless crystalline or amorphous precipitate
was separated by column chromatography on silica gel with
MeOH—NH4OH—CH2Cl2 (5 : 0.5 : 72) as an eluent.
1ꢀ[2,5ꢀDi(2ꢀthienyl)phenyl]piperidine (3a). Yield 55% (A),
85% (B), m.p. 78 C (from hexane). 1H NMR (250 MHz,
CDCl3), : 7.52 (d, 1 H, Ph, J = 7.5 Hz); 7.51—7.52 (m, 1 H,
Ph); 7.39 (br.s, 1 H, Ph); 7.28—7.34 (m, 4 H, CHthiophene);
7.07—7.12 (m, 2 H, CHthiophene); 2.91 (t, 4 H, (CH2)2, J = 5.1 Hz);
1.56—1.63 (m, 2 H, CH2); 1.72—1.79 (m, 4 H, (CH2)2).
13C NMR (75 MHz, CDCl3), : 151.7, 144.3, 141.2, 134.1, 129.8,
128.8, 127.9, 126.2, 125.9, 124.8, 124.7, 123.0, 121.0, 117.9,
77.2, 53.8, 25.9, 24.2. Found (%): C, 70.03; H, 6.23; N, 4.14.
C19H19NS2. Calculated (%): C, 70.11; H, 5.88; N, 4.30.
1ꢀ[2,5ꢀDi(2ꢀthienyl)phenyl]ꢀ1,4,8,11ꢀtetraazacyclotetraꢀ
1
decane 3b. Yield 75% (A), 86% (B), oil. H NMR (250 MHz,
CDCl3), : 7.49—7.52 (m, 2 H, Ph); 7.38—7.42 (m, 3 H, Ph +
+ CHthiophene); 7.28—7.34 (m, 2 H, CHthiophene); 7.08—7.12
(m, 2 H, CHthiophene); 3.16 (t, 2 H, CH2, J = 5.7 Hz); 2.99—3.03
(m, 2 H, CH2); 2.67—2.83 (m, 10 H, 5 CH2); 2.52 (t, 2 H, CH2,
J = 5.4 Hz); 2.18 (s, 3 H, NH); 1.77 (t, 2 H, CH2, J = 5.4 Hz);
1.67 (t, 2 H, CH2, J = 5.4 Hz). 13C NMR (75 MHz, CDCl3), :
149.8, 143.9, 140.9, 134.5, 131.6, 131.2, 128.0, 126.7, 126.6,
125.8, 124.9, 123.2, 122.1, 120.9, 77.1, 56.7, 48.7, 48.0, 47.2,
46.6, 45.3, 30.8, 26.5. Found (%): C, 65.12; H, 8.00. C24H32N4S2.
Calculated (%): C, 65.41; H, 7.72.
(d, 2 H, CHthiophene, J = 4.0 Hz); 6.99 (d, 2 H, CHthiophene
,
J = 3.9 Hz); 2.85 (t, 4 H, 2 CH2, J = 5.0 Hz); 1.60—1.65 (m, 4 H,
2 CH2); 1.45—1.53 (m, 2 H, CH2). Found (%): C, 46.99; H, 3.22;
N, 3.05. C19H17Br2NS2. Calculated (%): C, 47.22; H, 3.55;
N, 2.90.
Tri(tertꢀbutyl) 11ꢀ[2,5ꢀdi(2ꢀthienyl)phenyl]ꢀ1,4,8,11ꢀtetraꢀ
azacyclotetradecaneꢀ1,4,8ꢀtricarboxylate 3c. Yield 80% (A), oil.
1H NMR (250 MHz, CDCl3), : 7.52 (d, 1 H, Ph, J = 6.5 Hz);
7.48 (s, 1 H, Ph); 7.28—7.39 (m, 5 H, Ph + CHthiophene);
7.06—7.12 (m, 2 H, CHthiophene); 3.30—3.43 (m, 14 H, 7 CH2);
2.85—2.95 (m, 2 H, CH2); 1.84—1.95 (m, 4 H, 2 CH2); 1.50 (s, 9 H,
Me3C); 1.46 (s, 9 H, Me3C); 1.38 (s, 9 H, Me3C). 13C NMR
(75 MHz, CDCl3), : 155.5, 149.3, 143.8, 140.5, 134.4, 128.0,
130.4, 126.3, 126.2, 125.6, 124.9, 123.3, 122.1, 79.8, 79.6, 77.1,
53.3, 50.2, 47.1, 46.6, 28.5, 28.5, 28.4, 25.9. Found (%): C, 62.99;
H, 7.44; N, 13.06. C39H56N4O6S2. Calculated (%): C, 63.21;
H, 7.62; N, 12.95.
Poly[(2,2´ꢀbithiopheneꢀ5,5´ꢀdiyl)(2ꢀpiperidinoꢀ1,4ꢀphenylꢀ
ene)] (6). Cyclooctaꢀ1,5ꢀdiene (0.5 mL), 2,2´ꢀbipyridine (0.156 g,
1 mmol), and freshly prepared Ni(COD)225 (1 mmol) were addꢀ
ed under argon to a solution of compound 5 (0.483 g, 1 mmol) in
a mixture of dry DMF (5 mL) and toluene (30 mL). The resultꢀ
ing solution was heated at 90 C for 72 h. The resulting suspenꢀ
sion was filtered and the mother liquor was evaporated to dryꢀ
ness in vacuo. The solid residue was dissolved in dry THF (20 mL)
and reprecipitated with MeOH (5—10 mL). The precipitate of
the polymer was filtered off and washed with MeOH. This proꢀ
cedure was repeated several times for better purification of the
product. The yield of polymer 6 was 0.250 g, violetꢀbrown fibers.

Synthesis of 1ꢀaminoꢀ2,5ꢀdi(2ꢀthienyl)benzenes
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 2, February, 2012
307
1H NMR (250 MHz, tetrachloroethaneꢀd2), : 7.38—7.44 (m, 2 H,
Ph); 7.30—7.32 (br.s, 1 H, Ph); 7.12—7.20 (m, 2 H, CHthiophene);
6.95—7.10 (m, 2 H, CHthiophene); 2.80—2.85 (m, 4 H, 2 CH2);
1.61—1.66 (m, 4 H, 2 CH2); 1.43—1.52 (m, 2 H, CH2). ESI MS,
m/z (%): [M + H]+ 7757.24 (100%). C456H411N24S48. Calculatꢀ
ed for C456H411N24S48: M+ = 7756.95 (24 monomer units).
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This work was financially supported by the Council
on Grants at the President of the Russian Federation
(State Support Program for Leading Scientific Schools,
Grant NShꢀ65261.2010.3) and the Ministry of Education
and Science of the Russian Federation (State Contract
Nos 02.740.11.0260 and 14.740.11.1020).
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Received February 1, 2011;
in revised form May 3, 2011