Bromination of 1,3- and 1,5-dimethyl-1H-pyrazole-4-carbaldehydes

Full text of DOI:10.1134/S1070428007110292

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2007, Vol. 43, No. 11, pp. 1740–1741. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © O.S. Attaryan, G.A. Akopyan, K.S. Badalyan, G.G. Minasyan, G.V. Asratyan, 2007, published in Zhurnal Organicheskoi Khimii,
2
007, Vol. 43, No. 11, p. 1739.
SHORT
COMMUNICATIONS
Bromination of 1,3- and 1,5-Dimethyl-1H-pyrazole-
4-carbaldehydes
a
b
b
b
a
O. S. Attaryan , G. A. Akopyan , K. S. Badalyan , G. G. Minasyan , and G. V. Asratyan
a
ARIAK Institute of Applied Chemistry, Erevan, Armenia
b
Institute of Organic Chemistry, National Academy of Science of Armenia,
ul. Zakariya Sarkavaga 167a, Erevan, 375091 Armenia
Received December 22, 2006
DOI: 10.1134/S1070428007110292
With a view to obtain 5-bromo-1,3-dimethyl-1H-
(0.1 mol), was dissolved in 50 ml of acetic acid, 16 g
(0.1 mol) of bromine was added at 20–25°C, and the
mixture was heated to 100°C and kept for 10 h at that
temperature. After cooling, the mixture was neutralized
with 2 N NaOH and treated with chloroform (100 ml),
pyrazole and 3-bromo-1,5-dimethyl-1H-pyrazole we
tried to perform bromination of 1,3-dimethyl-1H-pyra-
zole-4-carbaldehyde (I) and 1,5-dimethyl-1H-pyra-
zole-4-carbaldehyde (II) with subsequent oxidation
and decarboxylation. Surprisingly, instead of the ex-
pected products III and IV, the bromination of formyl-
pyrazoles I and II gave 4-bromo-1,3-dimethyl-1H-pyr-
azole (V) and 4-bromo-1,5-dimethyl-1H-pyrazole (VI).
The structure of products V and VI was proved by
independent synthesis, bromination of 1,3-dimethyl-
and 1,5-dimethyl-1H-pyrazoles [1], as well as by the
the extract was dried over MgSO , the solvent was
4
removed, and the residue was distilled under reduced
2
0
pressure. Yield 15.7 g (90%), bp 45°C (1 mm), n
=
D
2
4
0
–1
1.5210, d
= 1.5059 [3]. IR spectrum: ν 1510 cm
(pyrazole ring). H NMR spectrum, δ, ppm: 2.15 s
1
(3H, 3-CH ), 3.81 s (3H, 1-CH ), 7.51 s (1H, 5-H).
3
3
Found, %: C 34.48; H 4.51; Br 45.88; N 16.23.
C H BrN . Calculated, %: C 34.31; H 4.02; Br 45.65;
1
data of H NMR and IR spectroscopy and elemental
5
7
2
analysis.
N 16.00.
Initial pyrazolecarbaldehydes I and II were synthe-
sized by the procedures described in [2]; I, mp 50°C;
II; mp 60°C.
4
-Bromo-1,5-dimethyl-1H-pyrazole (VI) was syn-
thesized in a similar way from 12.4 g (0.1 mol) of
,5-dimethyl-1H-pyrazole-4-carbaldehyde (II) and 16 g
1
4
-Bromo-1,3-dimethyl-1H-pyrazole (V). 1,3-Di-
(0.1 mol) of bromine. Yield 14.8 g (85%), bp 52°C
(1 mm), mp 43°C; published data [4]: bp 85°C
methyl-1H-pyrazole-4-carbaldehyde (I), 12.4 g
Me
CHO
Me
Br
Me
CHO
Br
Br , AcOH
2
N
N
N
N
Me
I
N
Me
V
N
Me
III
CHO
Br
Br
CHO
Br , AcOH
2
N
N
N
Me
Me
Me
N
N
N
Me
II
Me
Me
VI
IV
1740

BROMINATION OF 1,3- AND 1,5-DIMETHYL-1H-PYRAZOLE-4-CARBALDEHYDES
1741
–
1
(
10 mm), mp 38°C. IR spectrum: ν 1530 cm (pyra-
REFERENCES
1
zole ring). H NMR spectrum, δ, ppm: 2.25 s
3H, 5-CH ), 3.80 s (3H, 1-CH ), 7.21 s (1H, 3-H).
Found, %: C 34.62; H 4.42; Br 45.89; N 16.58.
C H BrN . Calculated, %: C 34.31; H 4.02; Br 45.65;
1
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p. 1676.
(
3
3
5
7
2
N 16.00.
2
3
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. Andreeva, M.A., Bolonov, M.I., Isaev, Sh.G., Mu-
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1
Mercury instrument operating at 300 MHz from solu-
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p. 65.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 43 No. 11 2007