New monomers for (bi)pyridine-containing polymers


209

New monomers for (bi)pyridine-containing polymers

A. P. Krinochkinab, M. I. Savchuka,  
E. S. Starnovskayaab, Y. K. Shtaitza, D. S. Kopchuk ab, 

I. L. Nikonovab, I. S. Kovalev a, G. V. Zyryanov ab*, 
V. L. Rusinov ab, O. N. Chupakhinab

a Ural Federal University named after the first President of Russia B. N. Yeltsin,  
19 Mira st., Ekaterinburg, 620002, Russian Federation

b I. Ya. Postovsky Institute of Organic Synthesis of RAS (Ural Branch),  
22/20 S. Kovalevskoy/Akademicheskaya st.,  

Ekaterinburg, 620990, Russian Federation
*email: g.v.zyrianov@urfu.ru

Abstract. Convenient methods for the synthesis of three monomers based on func-
tionalized (bi)pyridines with using “1,2,4-triaizine” methodology have been developed.

Keywords: monomers; 1,2,4-triazines; (bi)pyridines; inverse demand Diels-Alder reaction

Received: 09.09.2020. Accepted: 20.12.2020. Published:30.12.2020.

©  Krinochkin A. P., Savchuk M. I., Starnovskaya E. S., Shtaitz Y. K., Kopchuk D. S., 
Nikonov I. L., Kovalev I. S., Zyryanov G. V., Rusinov V. L., Chupakhin O. N., 2020

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Krinochkin A. P., Savchuk M. I., Starnovskaya E. S., Shtaitz Y. K., Kopchuk D. S.,  
Nikonov I. L., Kovalev I. S., Zyryanov G. V., Rusinov V. L., Chupakhin O. N.

Chimica Techno Acta. 2020. Vol. 7, no. 4. P. 209–214.
ISSN 2409–5613

Introduction
(2,2′-Bi)pyridine containing pol-

ymers are of interest from the point of view 
of creating OLED [1, 2] for redox catalytic 
reactions [3], as  electrolyte membrane 
fuel cell application [4] or anode materi-
als components [5]. In this regard, the de-
velopment of  convenient methods for 

the synthesis of compounds with the (poly)
pyridine fragment and suitable for using 
as monomers, is an actual purpose. In this 
article we propose the convenient methods 
for the synthesis of three potential mono-
mers of the (bi)pyridine series.

Experimental part
1H NMR spectra were recorded 

on a  Bruker Avance-400 spectrom-
eter (400  MHz), the  internal standard 
was SiMe4. Mass-spectra (ionization 
type — electrospray) were recorded on a   
MicrOTOF-Q II instrument from Bruker 
Daltonics (Bremen, Germany). Elemental 
analysis was performed on a Perkin Elmer 
PE 2400 II CHN analyzer. The  starting 
4-bromophenylhydrazone 2 was obtained 
according to the described method [11]. 

General procedure for the  synthesis 
of 1,2,4-triazines 3
Hydrazone 2 (605  mg, 2.5 mmol) 

was solved in  ethanol (30 ml) and solu-
tion of the corresponding carbaldehyde 1 
(2.5 mmol) in ethanol (25 ml) was added. 
The  resulting mixture was kept at  room 
temperature for 12 h. The precipitate was 
filtered off, washed with ethanol and dried. 
Then the obtained intermediate was sus-
pended in acetic acid (30 ml) and mixture 
was heated to  reflux two times. Solvent 
was removed under reduced pressure. 



210

Ethanol (30 ml) was added to the residue; 
the resulting crystals of 3 were filtered off, 
washed with ethanol and dried. The crude 
triazines were used directly in the next step 
without additional purification.

6-(4-Bromophenyl)-3-(5-bromopyri-
din-2-yl)-1,2,4-triazine (3a). Yield 630 mg 
(1.60 mmol, 64%). NMR 1H (DMSO-d6, δ, 
ppm): 7.75–7.79 (m, 2H, C6H4Br), 8.23 (dd, 
1H, 3J 8.4 Hz, 4J 2.4 Hz, H-4(py)), 8.25–8.29 
(m, 2H, C6H4Br), 8.49 (d, 1H, 

3J 8.4 Hz, 
H-5(py)), 8.89 (d, 1H, 4J 2.4 Hz, H-6(py)), 
9.52 (s, 1H, H-5). ESI–MS, m/z: 390.92 
(M+H)+.

6-Bromo-2-(6-(4-bromophenyl)-
1,2,4-triazin-3-yl)quinoline (3b). Yield 
800  mg (1.80 mmol, 72%). NMR 1H 
(DMSO-d6, δ, ppm): 7.77–7.83 (m, 2H, 
C6H4Br), 7.92 (dd, 1H, 

3J 8.0 Hz, 4J 2.0 Hz, 
H-7(qui)), 8.15–8.20 (m, 2H, H-5,8(qui)), 
8.30–8.35 (m, 2H, C6H4Br), 8.56 and 8.70 
(both d, 1H, 3J 8.4 Hz, H-3 and H-4 (qui)), 
9.61 (s, 1H, H-5). ESI–MS, m/z: 440.94 
(M+H)+.

3-(4-Bromophenyl)-6-(thiophen-
2-yl)-1,2,4-triazine (7). A  mixture 
of  349  mg (1.7 mmol) of  2-bromo-
1-(thiophen-2-yl)ethanone 5, 732 mg (3.4 
mmol) of hydrazide 6 and 25 mL of DMF 
was heated at 120 °C under argon for 10 h. 
The solvent was distilled off under reduced 
pressure, the  residue was treated with 
ethanol, and the  precipitate was filtered 
off. The crude triazine was used directly 
in the next step without addition purifica-
tion. Yield 343 mg (1.08 mmol, 63%). NMR 
1H (DMSO-d6, δ, ppm): 7.27 (dd, 1H, 

3J 5.2 
Hz, 3.8 Hz, H-4(thio)), 7.70–7.76 (m, 2H, 
C6H4Br), 7.27 (dd, 1H, 

3J 5.2 Hz, 4J 0.8 Hz, 
H-5 (thio)), 8.10 (dd, 1H, 3J 3.8 Hz, 4J 0.8 
Hz, H-3(thio)), 8.37–8.42 (m, 2H, C6H4Br), 
9.43 (s, 1H, H-5).

A general procedure for the synthesis 
of (bi)pyridines 4 and 8
The mixture of corresponding 1,2,4-tri-

azine 3 or 7 (0.8 mmol) and 1-morpholi-
nocyclo-pentene (0.64 ml, 4.0 mmol) was 
stirred at 200 °C for 2 h under argon at-
mosphere. Then, the  additional portion 
of  1-morpholinocyclopentene (0.32 ml, 
2.0 mmol) was added and the  resulting 
mixture was stirred for additional 1  h 
at the same conditions. The reaction mass 
was cooled to room temperature. The prod-
ucts were purified by flash chromatography 
(DCM as eluent) and then by recrystalliza-
tion (ethanol).

4-(4-Bromophenyl)-1-(5-bromopyri-
din-2-yl)-6,7-dihydro-5H-cyclopenta[c]
pyridine (4a). Yield 270 mg (0.63 mmol, 
78%). NMR 1H (DMSO-d6, δ, ppm): 2.08 
(m, 2H, CH2-6), 3.04 (t, 2H, 

3J 7.6 Hz, 
CH2-7), 3.46 (t, 2H, 

3J 7.6 Hz, CH2-5), 
7.48–7.54 (m, 2H, C6H4Br), 7.64–7.70 (m, 
2H, C6H4Br), 8.11 (dd, 1H, 

3J 8.4 Hz, 4J 1.6 
Hz, H-4′), 8.30 (d, 1H, 3J 8.4 Hz, H-5′), 8.47 
(s, 1H, H-3), 8.75 (d, 1H, 4J 1.6 Hz, H-6′). 
ESI–MS, m/z: 428.96 (M+H)+. Found, %: 
C 53.19, H 3.39, N 6.40. C19H14Br2N2. Cal-
culated, %: C 53.05, H 3.28, N 6.51.

6-Bromo-2-(4-(4-bromophenyl)-
6,7-dihydro-5H-cyclopenta[c]pyridin-
1-yl)quinoline (4b). Yield 290 mg (0.60 
mmol, 75%). NMR 1H (DMSO-d6, δ, ppm): 
2.14 (m, 2H, CH2-6), 3.08 (t, 2H, 

3J 7.6 
Hz, CH2-7), 3.69 (t, 2H, 

3J 7.6 Hz, CH2-
5), 7.51–7.57 (m, 2H, C6H4Br), 7.66–7.71 
(m, 2H, C6H4Br), 7.86 (dd, 1H, 

3J 8.8 Hz, 
4J 1.6 Hz, H-7(qui)), 8.02 (d, 1H, 3J 8.8 Hz, 
H-8(qui)), (d, 1H, 4J 1.6 Hz, H-5(qui)), 
8.40 and 8.56 (both d, 1H, 3J 8.8 Hz, H-3 
and H-4 (qui)), 8.54 (s, 1H, H-3). ESI–MS, 
m/z: 478.98 (M+H)+. Found, %: C 57.41, H 
3.22, N 8.67. C23H16Br2N2. Calculated, %: C 
57.53, H 3.36, N 8.53.



211

1-(4-Bromophenyl)-4-(thiophen-
2-yl)-6,7-dihydro-5H-c yclopenta[c]
pyridine (8). Yield 228  mg (0.64 mmol, 
80%). NMR 1H (DMSO-d6, δ, ppm): 2.14 
(m, 2H, CH2-6), 3.15 (t, 2H, 

3J 7.6 Hz, CH2-
7), 3.20 (t, 2H, 3J 7.6 Hz, CH2-5), 7.16 (dd, 
1H, 3J 5.2 Hz, 3.8 Hz, H-4(thio)), 7.33 (dd, 
1H, 3J 3.8 Hz, 4J 0.8 Hz, H-3(thio)), 7.41 
(dd, 1H, 3J 5.2 Hz, 4J 0.8 Hz, H-5(thio)), 
7.57–7.62 (m, 2H, C6H4Br), 7.65–7.70 (m, 
2H, C6H4Br), 8.73 (s, 1H, H-3). ESI–MS, 
m/z: 356.01 (M+H)+. Found, %: C 60.53, 
H 3.81, N 4.07. C18H14BrNS. Calculated, 
%: C 60.68, H 3.96, N 3.93.

1-(4-Bromophenyl)-4-(5-bromothio-
phen-2-yl)-6,7-dihydro-5H-cyclopenta[c]
pyridine (9). Pyridine 8 (307  mg, 0.86 

mmol) was dissolved in DMF (30 mL). N-
Bromosuccinimide (184  mg, 1.0 mmol) 
was added and the  resulting mixture 
was stirred for 8  h at  50 ºC. Then water 
(100  mL) was added to  the  mixture and 
precipitate formed was filtered off. The ana-
lytical sample was obtained by recrystalli-
zation (ethanol). Yield 329 mg (0.76 mmol, 
88%). NMR 1H (CDCl3, δ, ppm): 2.19 (m, 
2H, CH2-6), 3.17 (t, 2H, 

3J 7.6 Hz, CH2-
7), 3.20 (t, 2H, 3J 7.6 Hz, CH2-5), 7.10 and 
7.13 (d, 1H, 3J 3.8 Hz, H-3 and H-4 (thio)), 
7.61–7.65 (m, 2H, C6H4Br), 7.67–7.71 (m, 
2H, C6H4Br), 8.69 (s, 1H, H-3). ESI–MS, 
m/z: 433.92 (M+H)+. Found, %: C 49.53, 
H 3.14, N 3.39. C18H13Br2NS. Calculated, 
%: C 49.68, H 3.01, N 3.22.

Results and discussion
The “1,2,4-triazine” methodology has 

been used for the preparation of the target 
compounds [7–9]. In particular, we used 
the  modified synthetic route previously 
used for preparation of the luminophores 
of 2,2’-bipyridine [10] and 2-(2-pyridyl)
quinoluine series [11]. Namely, heterocy-
clization [6] of the corresponding commer-
cially available aldehydes 1a,b and hydra-
zone of 4’-bromoisonitrosoacetophenone 
2 [11] allowed to obtain the 1,2,4-triazine 

precursors 3, which are also of  interest 
as  monomers (Scheme  1). The  further 
solvent-free inverse demand Diels-Alder 
reaction with 1-morpholinocyclopentene 
[12] allowed to synthesize compounds 4 
of  2,2’-bipyridine and 2-(2-pyridyl)qui-
noluine series.

We have also suggested an  approach 
for obtaining the  monomer of  mono-
pyridine series. In this case we also used 
the “1,2,4-triazine” methodology. Namely, 

Br

N

N
OH

NH2

N
O

Br

N
O

Br

N

N
N

N

Br

N

N
N

N

Br

Br

Br

N
N

Br

N
N

Br

Br

Br

1a

1b

2

3a

3b

4a

4b

i

i

ii

ii

Scheme 1. Reagents and conditions: i) 12 h, r.t. / EtOH, then AcOH, 118 °C, 5 min; ii) 
1-morpholinocyclopentene, 200 °C, neat, 3 h.



212

the  condensation of  2-bromoacetylthio-
phene 5 with two equivalents of hydrazide 
of 4-bromobenzoic acid 6 allowed to ob-
tain the triazine precursor 7 (Scheme 2). 
This heterocyclization has been known 
for a long time [13]. In this case reaction 
was realized during heating in DMF with 
no sodium acetate [14, 15]. The  further 
solvent-free inverse demand Diels-Alder 
reaction [12] with 1-morpholinocyclo-
pentene allowed to obtain the condendes 
pyridine 8. For preparation of monomer 
9 we used the bromination of thiophene 
ring of compound 8 at position C5 by N-
bromosuccinimide in DMF. This reaction 

is a well-known effective method [16, 17]. 
For the full conversion of compound 8 to 9 
it is necessary the heating reaction mass 
at 50 °C.

The structure of compounds 4 and 9 was 
confirmed by data of NMR 1Н, mass-spec-
trometry and elemental analysis. The char-
acteristics of compounds 4 correlate with 
ones for the previously published similar 
compounds [10, 11]. For compound 9 there 
are the signals of protons of thiophene ring 
as two doublets, protons of cyclopentene 
fragment, protons of 4-bromophenyl moi-
ety, as well as proton of 6,7-dihydro-5H-
cyclopenta[c]pyridine as singlet.

Conclusions
In conclusion, we have reported herein 

effective synthetic protocols for the prep-
aration of  functionalized (bi)pyridines 

as  potential monomers for the  further 
synthesis of (bi)pyridines-based polymers 
for different applications.

Acknowledgements
This work was supported by  the  Russian Foundation for Basic Research (Grant 

#19-53-55002) and Grants Council of  the  President of  the  Russian Federation 
(no. NSh-2700.2020.3).

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213

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