Dehydrochlorination of 1-(2-chloroethyl)azoles in aqueous solution of N-methylmorpholine N-oxide

Full text of DOI:10.1134/S1070363216020377

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 2, pp. 414–416. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © G.B. Zakaryan, S.S. Hayotsyan, H.S. Attaryan, G.V. Hasratyan, 2016, published in Zhurnal Obshchei Khimii, 2016, Vol. 86, No. 2,
pp. 337–339.
LETTERS
TO THE EDITOR
Dehydrochlorination of 1-(2-Chloroethyl)azoles
in Aqueous Solution of N-Methylmorpholine N-Oxide
G. B. Zakaryan, S. S. Hayotsyan, H. S. Attaryan, and G. V. Hasratyan
Institute of Organic Chemistry, Scientific Technological Center of Organic and Pharmaceutical Chemistry,
National Academy of Sciences of Armenia, ave. Azatutyan 26, Yerevan, 0014 Armenia
e-mail: shayotsyan@gmail.com
Received August 13, 2015
Keywords: alternative reaction medium, azole, 1-vinylazole, dehydrochlorination
DOI: 10.1134/S1070363216020377
Synthesis of 1-vinylazoles and development of the
relevant, available and easily simulated technological
processes are one of actual issues in organic chemistry
in view of the propensity of the 1-vinylazoles for poly-
merization under conditions of radical initiation and
special properties of the thus produced polymers [1–10].
pyrazoles 1–4, 9, and 11 in an aqueous NMMO
solution in order to investigate the application scopes
of mentioned system. We found that the dehydro-
chlorination of the mentioned compounds occurrs in
this conditions without any phase-transfer catalyst
(Scheme 1).
Dehydrochlorination of 1-(2-chloroethyl)azoles 1–
, 9, and 11 in alcoholic solutions of KOH is among
The patterns revealed in the study of dehydro-
chlorination of 1-(2-chloroethyl)pyrazoles 1–4 for the
phase-transfer catalysis [16] were retained for the
NMMO–water system.
4
the methods of preparation of 1-vinylazoles 5–8, 10,
and 12. However, this method does not afford high
yields of the target compounds and can be hardly
implemented in industry [11–14]. Dehydrochlorination
under conditions of the phase-transfer catalysis is the
alternative to the homogeneous process; however, the
product yield is still low [15–18].
In contrast to the cases of 1-(2-chloroethyl)pyra-
zoles 1–4, dehydrochlorination of 2-chloroethyltriazole
9
and 2-chloroethyltetrazole 11 in an aqueous MMO
solution occurrs under much milder conditions, at 20–
2
5°C (Scheme 2).
Based on the data of mild alkylation of pyrazoles
and 3-nitro-1,2,4-triazole with bromopropyne in
aqueous solution of N-methylmorpholine N-oxide
By the easiness of the dehydrochlorination, the
studied azoles can be arranged in the 11 > 9 > 1 > 2 >
> 4 series, which corresponds with the data in [20]
3
(
NMMO) in the presence of KOH reported in [19], we
studied the dehydrochlorination of 1-(2-chloroethyl)
Scheme 2.
N
N
Scheme 1.
N
N
N
N
N
N
R1
R1
Cl
Cl
_
NMMO H O
9
10
2
N
NMMO, H O
R2
N
R2
2
N
KOH, 80
o
C
N
o
N
KOH, 25 C
N
Cl
N
N
1_
4
5 8
_
N
N
1
2
1
2
1
2
R = R = H (1, 5); R = CH
3
, R = H (2, 6); R = H, R =
3 3
CH (3, 7); R = R = CH (4, 8).
1
2
11
12
4
14

DEHYDROCHLORINATION OF 1-(2-CHLOROETHYL)AZOLES
415
2
0
Scheme 3.
8.0 g (74%), bp 55°C (10 mmHg), n 1.5200 [21]. IR
D
–
1
1
spectrum, ν, cm : 1530 (ring), 1640 (C=C). H NMR
OHC
OHC
spectrum, δ, ppm (J, Hz): 2.20 s (3H, 5-CH ), 4.80 d.d
3
_
NMMO H O
2
(1H, =CH , J = 9.3, 1.5), 5.45 d.d (1H, =CH , J = 15.7,
2
2
N
N
o
KOH, 80 C
1.5), 5.95 d (1H, 4-H, J = 2.0), 6.90 d.d (1H, NC=H,
J = 15.7, 9.3), 7.28 d (1H, 3-H, J = 2.2).
N
N
Cl
1
3
14
1
-Vinyl-3,5-dimethylpyrazole (8) was prepared
similarly from 15.8 g (0.1 mol) of 1-(2-chloroethyl)-
,5-dimethylpyrazole 4; reaction duration was of 4 h.
on the increasing of the acceptor inductive effect of the
hetero-ring by the increasing of the number of
heteroatoms in the last. The effect leads to the facilita-
tion of deprotonation on the N-substituent.
3
20
Yield 7.9 g (65%), bp 70°C (10 mmHg), n 1.5180
16]. IR spectrum, ν, cm : 1540 (ring), 1640 (C=C).
H NMR spectrum, δ, ppm (J, Hz): 2.11 s (3H, 3-CH3),
D
–
1
[
1
2
5
6
.33 s (3H, 5-CH ), 4.42 d.d (1H, =CH , J = 9.5, 1.5),
3 2
Dehydrochlorination is further facilitated by the
presence of the formyl group at position 4 of the
pyrazole cycle: dehydrochlorination of 4-formyl-
pyrazole 13 was complete within 15 min at 80°C. For
comparison, dehydrochlorination at room temperature
occurred similarly to the case of 1-(2-chloroethyl)-
triazole 9, being complete within 5 h (Scheme 3).
.22 d.d (1H, =CH , J = 15.3, 1.5), 5.67 s (1H, 4-H),
2
.33 d.d (1H, NC=H, J = 15.3, 9.5).
1
-Vinyl-1,2,4-triazole (10). A mixture of 13.1 g
(
(
0.1 mol) of 1-(2-chloroethyl)-1,2,4-triazole 9, 11.2 g
0.2 mol) of KOH, and 50 mL of 50 wt% of aqueous
MMO solution was vigorously stirred during 5 h at
20–25°C and then extracted with chloroform. After
removal of chloroform, the residue was distilled in
vacuum. Yield 6.6 g (70%), bp 58°C (1 mmHg), n
1.5200 [15]. IR spectrum, ν, cm : 1500 (ring), 1640
In summary, 50 wt % aqueous solution of MMO
can serve as the alternative reaction medium foe
dehydrochlorination of a series of 1-(2-chloroethyl)-
azoles.
2
D
0
–
1
1
(
(
C=C). H NMR spectrum, δ, ppm (J, Hz): 5.00 d.d
1H, =CH , J = 9.0, 1.5), 5.78 d.d (1H, =CH , J = 15.8,
1-Vinylpyrazole (5). A mixture of 13.02 g (0.1 mol)
2
2
of 1-(2-chloroethyl)pyrazole 1, 11.2 g (0.2 mol) of KOH,
and 50 mL of 50 wt% aqueous solution of MMO was
vigorously stirred during 2 h at 80°C. After cooling to
ambient, the reaction mixture was extracted with
chloroform. The solvent was removed, and the residue
was distilled in vacuum. Yield 7.0 g (75%), bp 63°C
1
3
.5), 7.12 d.d (1H, NC=H, J = 15.8, 9.0), 7.92 s (1H,
-H), 8.38 s (1H, 5-H).
2
-Vinyltetrazole (12) was prepared similarly from
1
3.2 g (0.1 mol) of 2-(2-chloroethyl)tetrazole 11; reac-
tion duration was of 2 h. Yield 8.2 g (85%), bp 63°C
2
0
–1
(
1
50 mmHg), nD 1.5160 [16]. IR spectrum, ν, cm :
20
–1
(
60 mmHg), nD 1.4830 [18]. IR spectrum, ν, cm :
1
520 (ring), 1640 (C=C). H NMR spectrum, δ, ppm
1
1
490 (ring), 1640 (C=C). H NMR spectrum, δ, ppm
(
(
J, Hz): 5.00 d.d (1H, =CH , J = 9.0, 1.5), 5.52 d.d
2
(
(
J, Hz): 5.43 d.d (1H, =CH , J = 8.7, 1.3), 6.22 d.d
1H, =CH , J = 15.6, 1.3), 7.62 d.d (1H, NC=H, J =
2
1H, =CH , J = 15.8, 1.5), 6.26 t (1H, 4-H, J = 2.2),
2
2
7
.12 d.d (1H, NC=H, J = 15.8, 9.0), 7.50 d (1H, 3-H,
1
5.6, 8.7), 8.70 br. s (1H, 5-H).
J = 2.4), 7.58 d (1H, 5-H, J = 2.0).
1
-Vinyl-4-formylpyrazole (14) was prepared simi-
1
-Vinyl-3-methylpyrazole (6) was prepared simi-
larly to pyrazole 5 from 15.8 g (0.1 mol) of 1-(2-
chloroethyl)-4-formylpyrazole 13; reaction duration
was of 15 min. Yield 8.7 g (72%), bp 90°C (3 mmHg),
larly from 14.4 g (0.1 mol) of 1-(2-chloroethyl)-3-
methylpyrazole 2; reaction duration was of 3 h. Yield
.6 g (80%), bp 50°C (10 mmHg), n 1.5150 [21]. IR
spectrum, ν, cm : 1530 (ring), 1640 (C=C). H NMR
spectrum, δ, ppm (J, Hz): 2.16 s (3H, 3-CH ), 4.76 d.d
1H, =CH , J = 9.2, 1.5), 5.42 d.d (1H, =CH , J = 15.7,
.5), 5.85 d (1H, 4-H, J = 2.0), 6.92 d.d (1H, NC=H,
J = 15.7, 9.3), 7.42 d (1H, 5-H, J = 2.3).
2
D
0
8
2
0
–1
–
1
1
nD 1.5640 [22]. IR spectrum, ν, cm : 1520 (ring),
1
1
640 (C=C). H NMR spectrum, δ, ppm (J, Hz): 4.98
d.d (1H, =CH , J = 9.0, 1.0), 5.77 d.d (1H, =CH , J =
5.5, 1.0), 7.19 d.d (1H, =CH, J = 15.5, 9.0), 7.96 s
1H, 3-H), 8.56 s (1H, 5-H), 8.83 s (1H, CHO).
3
2
2
(
1
2
2
1
(
1
1
-Vinyl-5-methylpyrazole (7) was prepared simi-
Н NMR spectra were recorded using a Varian
larly from 14.4 g (0.1 mol) of 1-(2-chloroethyl)-5-
methylpyrazole 3; reaction duration was of 2.5 h. Yield
Mercury-300VX (300.05 Hz) instrument at 300 K in
the solutions in DMSO-d –CCl (1 : 3) with TMS as
6
4
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 2 2016

4
16
ZAKARYAN et al.
internal reference. IR spectra were recorded using a
Specord 75 IR instrument (suspension in Vaseline oil
or thin film).
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