ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 4, pp. 874–875. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © A.O. Baltayan, V.I. Rstakyan, S.K. Antanosyan, G.A. Akopyan, O.S. Attaryan, G.V. Asratyan, 2009, published in Zhurnal Obshchei
Khimii, 2009, Vol. 79, No. 4, pp. 701–702.
LETTERS
TO THE EDITOR
Bromination of 1,3-Dimethyl-
and 1,5-Dimethyl-4-hydroxymethylpyrazoles
A. O. Baltayan, V. I. Rstakyan, S. K. Antanosyan,
G. A. Akopyan, O. S. Attaryan, and G. V. Asratyan
Institute of Applied Chemistry “Ariak,”
Artashatskoye shosse 5/2, Yerevan, 375053 Armenia,
e-mail: angelabaltayan@mail.ru
Received November 6, 2008
DOI: 10.1134/S1070363209040367
Ambiguous behavior in the bromination of 4-
formylpyrazoles [1, 2] and 4-pyrazolecarboxylic acids
[3] was mentioned earlier. In the presence of sodium
hydroxide the reaction proceeds as substitution of
carbonyl (carboxy) group with the bromine atom.
The structure of compounds ΙΙΙ and IV was
established on the basis of Н NMR and IR spec-
troscopy and elemental analysis data.
1
1
In the Н NMR spectra signals of methyl and
hydroxy group protons at δ 4.20 and 3.97 ppm are
absent. Integral intensities of the others protons
correspond fully to the structures of 1,3-dimethyl- and
1,5-dimethyl-4-bromopyrazoles ΙΙΙ and IV.
4-Hydroxymethylpyrazole hydroxy group seems to
be a convenient functional substituent for purposeful
synthetic transformations [4].
1,3-Dimethyl-4-bromopyrazole (III). To
a
In continuation of the search for synthetic pathways
to 1,3-dimethyl-5-bromo- and 1,5-dimethyl-3-bromo-
pyrazoles we studied in this work the bromination of
1,3-dimethyl- and 1,5-dimethyl-4-hydroxymethyl-
pyrazoles I and II [1–3, 5]. The results of the
investigation show that bromination of 4-hydroxy-
methylpyrazoles in the water–alkali medium leads to
substitution of hydroxymethyl group with the bromine
atom:
mixture of 13.0 g of 1,3-dimethyl-4-hydroxymethyl-
pyrazole I, 100 ml of water, and 12 g of sodium
hydroxide was added dropwise 16 g of bromine at
room temperature within 1 h. Then the product was
extracted with chloroform (3×50 ml) and dried over
MgSO4. When the solvent was removed, the residue
was distilled in vacuum. Yield 12.6 g (72%), bp 47°C
(1 mm Hg), nD20 1.5210 [1, 6]. IR spectrum, ν, cm–1:
1510 (ring). 1Н NMR spectrum, δ, ppm: 2.14 s (3H, 3-
CH3), 3.80 s (3H, N–CH3), 7.50 s (1H, 5-H). Found,
%: С 34.26; Н 4.35; Br 45.80; N 16.43. С5Н7BrN2.
Calculated, %: С 34.29; Н 4.00; Br 45.71; N 16.00.
HO
Me
Br
Me
N
N
N
1.5-Dimethyl-4-bromopyrazole (ΙV) was prepared
similarly from 13.0 g of 1,5-dimethyl-4-hydroxyme-
thylpyrazole ΙΙ. Yield 11.4 (65%), bp 53°C (1 mm Hg),
N
Me
Br2
Me
I
mp 43°C [1, 6]. IR spectrum, ν, cm–1: 1530 (ring). Н
1
III
HO
NaOH
Br
NMR spectrum, δ, ppm: 2.25 s (3H, 5-CH3), 3.80 s
(3H, N–CH3), 7.21 s (1H, 3-H). Found, %: С 34.71; Н
4.48; Br 45.82; N 16.57. С5Н7BrN2. Calculated, %: С
34.29; Н 4.00; Br 45.71; N 16.00.
N
Me
N
N
Me
N
Me
Me
II
The IR spectra were taken on a Specord-75 IR
spectrophotometer (KBr pellets, film). The Н NMR
1
IV
874