Aqueous hydrolysis of pyrazol-1-ylacetates

Full text of DOI:10.1134/S107036321205026X

ISSN 1070-3632, Russian Journal of General Chemistry, 2012, Vol. 82, No. 5, p. 946. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © K.S. Badalyan, A.G. Asratyan, O.S. Attaryan, 2012, published in Zhurnal Obshchei Khimii, 2012, Vol. 82, No. 5, pp. 876–877.
LETTERS
TO THE EDITOR
Aqueous Hydrolysis of Pyrazol-1-ylacetates
K. S. Badalyan, A. G. Asratyan, and O. S. Attaryan
Institute of Organic Chemistry, National Academy of Sciences of Armenia, pr. Azatutyan, 26, Yerevan, 00014 Armenia
e-mail: ani_hasratyan@mail.ru
Received November 10, 2011
DOI: 10.1134/S107036321205026X
The pyrazole esters (n = 2) are known to be
hydrolyzed in the presence of bases [1–3]. We found
that pyrazole esters I–III (n = 1) are hydrolyzed with
water in the absence of bases.
15 h. Yield 2.8 g (68%). The isomers molar ratio is
3:5–3:1, respectively. White crystals, mp 160–163°C
–1
(water). IR spectrum, ν, cm : 1530 (ring), 1680 (C=O),
1
3
100–3400 (COOH). Н NMR spectrum (DMSO-d ),
6
R1
R1
δ, ppm (J, Hz): 2.19 s (3H, 3-CH ), 2.22 s (3H, 5-CH ),
3 3
4
.70 s and 4.73 s (2H, N-CH ), 5.98 d (1Н, 4-Н, J 2.2),
2
Δ
N
N
7.2 d (1Н, 3-Н, J 1.8), 7.4 d (1Н, 5-Н, J 2.2), 12.60
br.s (1Н, ОН). Found, %: С 51.12; Н 5.64; N 20.35.
С Н N О . Calculated, %: С 51.42; Н 5.71; N 20.00.
R2
I−III
H O
R2
2
N
N
O
O
CH −C
CH −C
2
2
6
8
2
2
OC H5
IV−VI
OH
1
2
3
,5-Dimethylpyrazol-1-ylacetic acid (VI) was pre-
1
2
1
2
3
I, IV, R = R = H; II, V, R = CH , R = H and R = H,
R = CH ; III, VI, R = R = CH .
3 3
2
1
2
pared similarly from 5 g of the ester III, the reaction
time is 25 h. Yield 2.7 g (65%). White crystals, mp 188–
–1
This behavior of the esters I–III is apparently caused
by the negative inductive effect of pyrazole ring. This
is supported by the fact that the reaction time increases
190°C (water) [5]. IR spectrum, ν, cm : 1540 (ring), 1700
1
(C=O), 3300–3400 (ОН). Н NMR spectrum (DMSO-d ),
6
δ, ppm (J, Hz): 2.11 s (3H, 3-CH ), 2.18 s (3H, 5-CH ),
3
3
2
.5 times when passing from compound I to compound
4.63 s (2H, NCH ), 5.71 s (1Н, 4-Н), 12.57 br.s (1Н,
2
III. Another important fact which must be taken into
account when considering the mutual influence of the
directly bonded atoms is the proximity of the pyrazole
ring to the carbonyl carbon. As the distance between
the atoms increases (n = 2), the electrophilicity of the
carbonyl carbon decreases, therefore the stability of
esters with respect to water increases.
ОН). Found, %: С 54.85; Н 6.73; N 18.32. С Н N О .
7
10
2
2
Calculated, %: С 54.54; Н 6.49; Br 45.71; N 18.18.
The IR spectra were registered on a Specord IR-75
1
instrument from KBr pellets. The Н NMR spectra
were recorded on a Varian Mercury-300 spectrometer
in DMSO-d . The initial pyrazol-1-ylacetates I–III
6
were obtained by the known methods [4]; ethyl
2
0
pyrazol-1-ylacetate (I): bp 95–98°C (3 mm Hg), nD
Pyrazol-1-ylacetic acid (IV). A mixture of 5 g of
compound I and 25 ml of water was heated at 100ºC
for 10 h. After cooling, the mixture was alkalinized
with an aqueous solution of Na CO and extracted with
1
1
.4690; ethyl 3(5)-methylpyrazol-1-ylacetate (II): bp
2
0
04–108°C (3 mm Hg), n 1.4620 [the isomers ratio
D
is (3:5)–(4:1)]; ethyl 3,5-dimethylpyrazol-1-ylacetate
2
3
2
0
(
III): bp 110–115°C (3 mm Hg), n 1.4700.
D
5
0 ml of ether. The aqueous solution was evaporated to
a half volume and neutralized with hydrochloric acid.
The resulting crystals were filtered off. Yield 2.5 g
REFERENCES
1
.
Attaryan, O.S., Baltayan, A.O., and Matsoyan, S.G.,
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Asratyan, G.V., and Matsoyan, S.G., Zh. Obshch.
Khim., 2006, vol. 76, no. 11, p. 1901.
(
70%), white crystals, mp 175–178°C (water). IR spec-
–
1
trum, ν, cm : 1530 (ring), 1700 (C=O), 3100–3400
1
(
COOH). Н NMR spectrum (DMSO-d ), δ, ppm (J,
6
Hz): 4.84 s (2H, CH ), 6.19 d.d (1H, 4-Н, J 2.3, 1.8),
2
3
.
Attaryan, O.S., Baltayan, A.O., and Matsoyan, S.G., Zh.
Obshch. Khim., 2007, vol. 77, no. 2, p. 325.
Giles, D., Parnell, E.W., and Renwick, J.D., J. Chem.
Soc., 1966, no. 13, p. 1179.
7
.34 d (1H, 5-H, J 1.8), 7.57 d (1Н, 3-Н, J 2.3), 12.63
br.s (1Н, ОН). Found, %: С 47.85; Н 4.38; N 22.51.
С Н N О . Calculated, %: С 47.61; Н 4.76; N 22.22.
4
.
5
6
2
2
3(5)-Methylpyrazol-1-ylacetic acid (V) was obtained
5. Nam, N.L., Grandberg, I.I., and Sorokin, V.I., Khim.
Geterotsikl. Soed., 1998, no. 3, p. 416.
similarly from 5 g of the ester II, the reaction time was
9
46