Synthesis of N-vinylazoles from vinyl acetate without using mercury catalysts

Article abstract of DOI:10.1134/S1070363207120158

N-Vinyl-substituted pyrazole, 3(5)-methylpyrazole, imidazole, and 1,2,4-triazole were synthesized by addition of the corresponding azoles to vinyl acetate under conditions of phase-transfer catalysis, followed by pyrolysis of N-(1-acetoxyethyl)azoles thus formed at 350-400°C in the presence of water.

Full text of DOI:10.1134/S1070363207120158

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 12, pp. 2176 2178.
Pleiades Publishing, Ltd., 2007.
Original Russian Text
O.S. Attaryan, A.O. Baltayan, R.E. Sagatelyan, K.Ts. Takmazyan, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77,
No. 12, pp. 2031 2033.
Synthesis of N-Vinylazoles from Vinyl Acetate
without Using Mercury Catalysts
a
a
b
b
O. S. Attaryan , A. O. Baltayan , R. E. Sagatelyan , and K. Ts. Takmazyan
a
Institute of Organic Chemistry, National Academy of Sciences of Armenia,
ul. Zakariya Sarkavaga 167a, Yerevan, 375091 Armenia
e-mail: angelabaltayan@mail.ru
b
State University of Engineering of Armenia Republic, Erevan, Armenia
Received June 7, 2007
Abstract N-Vinyl-substituted pyrazole, 3(5)-methylpyrazole, imidazole, and 1,2,4-triazole were synthesized
by addition of the corresponding azoles to vinyl acetate under conditions of phase-transfer catalysis, followed
by pyrolysis of N-(1-acetoxyethyl)azoles thus formed at 350 400 C in the presence of water.
DOI: 10.1134/S1070363207120158
Syntheses of N-vinylazoles on the basis of vinyl
acetate usually imply the use of toxic mercury cata-
lysts [1 11]. With the goal of developing a procedure
for the synthesis of N-vinylazoles from vinyl acetate
in the absence of mercury catalyst we examined
nucleophilic addition of azoles I V to vinyl acetate
under conditions of phase-transfer catalysis, followed
by pyrolysis of the resulting 1-(1-acetoxyethyl)azoles
VI IX. It is known that addition of NH-heterocycles
to vinyl acetate in acetone in the presence of a ca-
talytic amount of potassium hydroxide is not selective:
apart from the target -acetoxyethylazoles, N-acetyl-
pyrazoles are formed [12 15].
We have found that 1-(1-acetoxyethyl)azoles VI
IX can be obtained under conditions of phase-transfer
catalysis in a liquid liquid system [water organic
solvent, K CO , benzyl(triethyl)ammonium chloride].
2
3
Our results showed that the yields of addition prod-
ucts VI IX depend on the azole acidity.
R
R
R
N
N
R
R
N
N
N
O
R
N
H
O
VI, VII
X, XI
O
I III
N
N
N
350 400 C
O
phase-transfer
catalyst
N
O
N
N
H
IV
N
O
VIII
XII
N
N
N
N
N
N
N
N
O
H
V
O
IX
XIII
I, VI, X, R = R = H; II, VII, XI, R = H, R = Me (R = Me, R = H); III, R = R‘ = Me.
176
2

SYNTHESIS OF N-VINYLAZOLES FROM VINYL ACETATE
2177
Imidazole (IV) (pK 6.95 [16]) is a stronger base
proton addition) than 3,5-dimethylpyrazole (III) (pKa
1 g of benzyl(triethyl)ammonium chloride (BTEAC)
under stirring at room temperature. The mixture was
stirred for 2 h and extracted with chloroform, and the
a
(
4
.38 [17]) and a stronger acid (pK 14.52) than 3,5-
a
dimethylpyrazole (pK 22.0) upon deprotonation. Due
extract was dried over MgSO . The solvent was
removed and the residue was subjected to fractional
distillation under reduced pressure.
a
4
to their amphoteric character, their reactions are
largely determined by acid base properties of the
medium. Acid base equilibrium of azoles may be
displaced toward either conjugate base or conjugate
acid. Under the given conditions, 3,5-dimethylpyra-
zole remains neutral, and no addition occurs even at
1
-(1H-Pyrazol-1-yl)ethyl acetate (VI). Yield
2
0
20
7
5.0%, bp 64 C (1 mm), n = 1.4670, d4 = 1.0731.
D
1
H NMR spectrum (DMSO-d , 300 MHz), , ppm
6
5
0 60 C. Unlike 3,5-dimethylpyrazole (III), pyrazole
(J, Hz): 1.80 d (3H, CHCH , J = 6.2), 2.05 s (3H,
3
(I) (pK 14.04 [17]) adds to vinyl acetate with a fairly
COCH ), 6.22 d. d (1H, 4-H, J = 1.9), 6.78 q (1H,
a
3
high yield (75.0%), while the reactivity of 3(5)-me-
CHCH , J = 6.2), 7.42 d (1H, 5-H, J = 1.9), 7.69 d
3
thylpyrazole (II) (pK 18.5 [17]) occupies an inter-
(1H, 3-H, J = 2.3). Found, %: C 54.81; H 6.83; N
a
mediate place (yield of the addition product 40%). No
success was achieved by prolonging the reactions with
pyrazoles II and III by a factor of 6, for the process
was accompanied by hydrolysis of vinyl acetate. As
18.62. C H N O . Calculated, %: C 54.55; H 6.49;
7
10
2
2
N 18.18.
1
-[3(5)-Methyl-1H-pyrazol-1-yl]ethyl acetate
20
(
VII). Yield 35.0%, bp 84 85 C (1 mm), n
.4759, d4 = 1.0838. H NMR spectrum (DMSO-d ,
00 MHz), , ppm (J, Hz): 1.80 d (3H, CHCH , J =
.2), 2.04 s (3H, COCH ), 2.25 s [3H, 3(5)-CH ],
.0 d (1H, 4-H, J = 2.2), 6.63 q (1H, CHCH , J =
.2), 7.22 7.51 d [1H, 5(3)-H, J = 2.2]. Found, %:
=
D
expected, the addition of 1,2,4-triazole (V) (pK 15.4)
20
1
a
1
3
6
6
6
6
[
17] to vinyl acetate gave the corresponding acetoxy-
3
ethyltriazole in a fairly high yield (90%). Thus, re-
duced acidity hinders generation of azolate ion and
hence the addition process.
3
3
3
1
C 57.69; H 7.51; N 16.50. C H N O . Calculated, %:
In the H NMR spectra of compounds VI IX, we
8
12
2
2
C 57.14; H 7.14; N 16.67.
observed a quartet at 6.63 6.87 ppm from the NCH
proton; this indicates that the examined azoles add to
vinyl acetate exclusively at the -carbon atom at the
double bond.
1
-(1H-Imidazol-1-yl)ethyl acetate (VIII). Yield
9
(
0.0% (30%, no catalyst was added), bp 106 C
2 mm), nD = 1.4784, d4 = 1.1224. H NMR spec-
20
20
1
trum (DMSO-d , 300 MHz), , ppm (J, Hz): 1.77 d
6
(
(
1
3H, CHCH , J = 6.3), 2.04 s (3H, COCH ), 6.71 q
3
3
1H, CHCH , J = 6.3), 6.86 d.d (1H, 4-H, J = 1.5,
3
.2), 7.14 d.d (1H, 5-H, J = 1.5, 1.2), 7.66 t (1H, 2-H,
J = 1.2). Found, %: C 54.32; H 6.23; N 18.35.
C H N O . Calculated, %: C 54.55; H 6.49; N 18.18.
7
10
2
2
reaction in the absence of water. Presumably, the
presence of water prevents tarring. The physical
constants and other parameters of N-vinylazoles X
XIII were in agreement with published data.
1-(1H-1,2,4-triazol-1-yl)ethyl acetate (IX). Yield
80.0% (25%, no catalyst was added), bp 105 C
(1 mm), n2 = 1.4635, d4 = 1.1972. H NMR spec-
0
20
1
D
trum (DMSO-d , 300 MHz), , ppm (J, Hz): 1.80 d
6
(
3H, CHCH , J = 6.2), 2.05 s (3H, COCH ), 6.87 q
3
3
EXPERIMENTAL
(1H, CHCH , J = 6.2), 7.81 s (1H, 3-H), 8.46 s (1H,
3
5
-H). Found, %: C 46.02; H 5.35; N 27.34. C H N
6 9 3
The IR spectra were recorded on a Specord 75 IR
spectrometer from thin films (neat). The H NMR
O . Calculated, %: C 46.45; H 5.81; N 27.09.
2
1
Thermal decomposition of 1-(1-acetoxyethyl)-
azoles VI IX (general procedure). An aqueous solu-
tion of 1-(1-acetoxyethyl)azoles VI IX was slowly
spectra were measured on a Mercury 300 Vx spectrom-
eter at 300.077 MHz. GLC analysis was performed
on an LKhM-8MD chromatograph (1-m column
packed with 10% of Carbowax-20M on Inerton AW-
1
supplied (at a rate of 0.5 ml min ) into a Pyrex tube
1
heated to 350 400 C. The products were collected in
a receiver cooled with ice water, a 2 N aqueous solu-
tion of sodium carbonate was added, the mixture was
thoroughly extracted with chloroform, the extract was
dried over magnesium sulfate, the solvent was dis-
tilled off, and the residue was subjected to fractional
distillation under reduced pressure.
HMDS; carrier gas helium, flow rate 40 ml min ;
detector temperature 220 C).
General procedure for the addition of azoles
I V to vinyl acetate. Vinyl acetate, 13 ml, was added
dropwise to a mixture of 0.1 mol of azole I V,
0
.1 mol of potassium carbonate, 50 ml of water, and
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 12 2007

2178
ATTARYAN et al.
1
-Vinyl-1H-pyrazole (X) was obtained from
7. Kofman, T.P. and Kartseva, G.Yu., Russ. J. Org.
Chem., 2001, vol. 37, no. 5, p. 707.
1
(
5.4 g of compound VI. Yield 55%, bp 63 C
50 mm), n2 = 1.5163 [3]. Found, %: C 63.37;
0
D
8. Lopyrev, V.A., Kuznetsova, N.P., Myachina, G.F.,
H 6.75; N 29.31. C H N . Calculated, %: C 63.83;
5
6
2
and Ermakova, T.G., Khim. Geterotsikl. Soedin.,
H 6.38; N 29.79.
(5)-Methyl-1-vinyl-1H-pyrazole (XI) was ob-
tained from 16.8 g of compound VII. Yield 60%,
1
983, no. 11, p. 1535.
3
9. Sirotkina, E.E., Filimonov, V.D., and Sazanova, Z.P.,
Russ. J. Org. Chem., 1973, vol. 9, p. 387.
2
0
bp 50 55 C (10 mm), n = 1.5175 [18]. Found, %:
10. Vereshchagin, L.I., Buzilova, S.R., Mityukova, T.K.,
Proidakov, A.G., Kizhnyaev, V.N., Il’ina, V.V., Su-
khanov, G.T., Gareev, G.A., and Bagers, A.K.,
Zh. Org. Khim., 1986, vol. 22, no. 9, p. 1979.
D
C 66.32; H 7.83; N 25.41. C H N . Calculated, %:
6
8
2
C 66.66; H 7.41; N 25.93.
-Vinyl-1H-imidazole (XII) was obtained from
5.42 g of compound VIII. Yield 52%, bp 71 C
1
1
1. Lebedev, N.P. and Kalaus, I.V., Khim. Geterotsikl.
Soedin., 1989, no. 6, p. 856.
1
3 mm), n2 = 1.5300 [19]. Found, %: C 63.70;
0
(
D
H 6.49; N 29.38. C H N . Calculated, %: C 63.83; H
12. Furukawa, Y., Onishi, A., and Tsuruta, T., J. Chem.
Soc. Jpn., Ind. Chem. Sect., 1957, vol. 60, p. 170.
5
6
2
6
.38; N 29.79.
-Vinyl-1H-1,2,4-triazole (XIII) was obtained
from 15.5 g of compound IX. Yield 58%, bp 58 C
1
3. Shekhirev, Yu.P., Lopapinskii, V.P., Sutyagin, V.M.,
and Tuzovskaya, S.A., Khim. Geterotsikl. Soedin.,
1983, no. 11, p. 1504.
1
10 mm), n2 = 1.5200 [20]. Found, %: C 50.31; H
0
(
D
1
4. Attaryan, O.S., Asratyan, G.V., Darbinyan, E.G., and
Matsoyan, E.G., Russ. J. Org. Chem., 1988, vol. 24,
no. 6, p. 1339.
5
5
.80; N 43.98. C H N . Calculated, %: C 50.53; H
4 5 3
.26; N 44.21.
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