ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 10, pp. 1821 1822.
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 Obshchei Khimii, 2007,
Vol. 77, No. 10, pp. 1757 1758.
LETTERS
TO THE EDITOR
Bromination of 1,3-Dimethyl-
and 1,5-Dimethyl-1H-pyrazole-4-carbaldehydes
O. S. Attaryana, G. A. Akopyanb, K. S. Badalyanb, G. G. Minasyanb, G. V. Asratyana
a ARIAK Institute of Applied Chemistry of the Republic of Armenia,
Artashatskoe shosse 5/2, Yerevan, 375053 Armenia
b Institute of Organic Chemistry, National Academy of Sciences of Armenia, Yerevan, Armenia
Received July 13, 2007
DOI: 10.1134/S1070363207100295
Proceeding with the search for synthetic approaches
to 5-bromo-1,3-dimethyl- and 3-bromo-1,5-dimethyl-
pyrazoles [1] we have studied bromination of
1,3-dimethyl- and 1,5-dimethyl-1H-pyrazole-4-carbal-
dehydes (I, II). It was found that the reaction in
aqueous alkali involves substitution of the formyl
group by bromine by the following scheme:
4-Bromo-1,3-dimethyl-1H-pyrazole (III) To a
solution of 12.5 g of 1,3-dimethyl-1H-pyrazole-4-
carbaldehyde (I) in 100 ml of water, 12 g of NaOH
was added and then 16 g of bromine was added drop-
wise at room temperature. The reaction mixture was
then extracted with chloroform (3 50 ml), the extract
was dried over MgSO4, the solvent was removed, and
the residue was distilled in a vacuum to obtain 12 g
(69%) of compound III, bp 45 C (1 mm Hg), nD20
O
1
1.521, d240 1.4059 [1, 4]. IR spectrum, , cm : 1510
C
CH3
Br
CH3
1
Br2
OH
H
(pyrazole ring). H NMR spectrum, , ppm: 2.15 s
N
N
(3H, 3-CH3), 3.81 s (3H, N-CH3), 7.51 s (1H, H4).
Found, %: C 34.38. H 4.31, Br 45.88, N 16.43.
C5H7BrN2. Calculated, %: C 34.31, H 4.02, Br 45.65,
N 16.00.
N
N
CH3
CH3
I
III
O
C
4-Bromo-1,5-dimethyl-1H-pyrazole (IV) was
obtained in a similar way from 12.4 g of 1,5-dimethyl-
1H-pyrazole-4-carbaldehyde (II) and 16 g of bromine.
Yield 11 g (63%), bp 54 C (1 mm Hg), mp 43 C
[1, 4]. IR spectrum, , cm : 1530 (pyrazole ring). H
NMR spectrum, , ppm: 2.25 s (3H, 3-CH3), 3.80 s
(3H, N-CH3), 7.21 s (1H, H4). Found, %: C 34.62,
H 4.42, Br 45.89, N 16.58. C5H7BrN2. Calculated, %:
C 34.31, H 4.02, Br 45.65, N 16.00.
The 1H NMR spectra were taken on a Varian
Mercury-300 spectrometer in DMSO-d6. The IR spec-
tra were obtained on a Specord IR-75 spectrometer in
KBr pellets and in thin layer.
Br
H3C
Br2
OH
H
H3C
N
N
1
1
N
N
CH3
IV
CH3
II
The structure of compounds III and IV was es-
tablished by means of IR and H NMR spectroscopy
and elemental analysis. The H NMR spectrum con-
tains no aldehyde proton signal at 9.78 ppm, and
1
1
1
the IR spectrum shows no bands at 1680 cm related
to the formyl group. The integral intensities of the rest
protons are completely consistent with the suggested
structures.
REFERENCES
1. Attaryan, O.S., Akopyan, G.A., Badalyan, K.S., and
Asratyan, G.V., Zh. Obshch. Khim., 2007, vol. 77,
no. 2, p. 335.
Starting pyrazoles I and I were prepared by known
procedures [2, 3], mp 50 and 60 C, respectively.
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