Russian Journal of Organic Chemistry, Vol. 37, No. 12, 2001, pp. 1795 1796. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 12,
2001, p. 1876.
Original Russian Text Copyright
2001 by Levkovskaya, Bozhenkov, Malyushenko, Mirskova.
SHORT
COMMUNICATIONS
Dedicated to Academician M.G.Voronkov on occasion of his 80th birthday
Synthesis of Pyrazole Derivatives
from 1,1-Dimethylhydrazine and Chlorovinyl Ketones
G. G. Levkovskaya, G. V. Bozhenkov, R. N. Malyushenko, and A. N. Mirskova
Faworskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail:ggl@irioch.irk.ru
Received October 27, 2000
We previously showed [1] that 2,2-dichlorovinyl
ketones react with 1,1-dimethylhydrazine to give the
corresponding 3-substituted 5-chloro-1-methylpyra-
zoles. We now report on a new way to pyrazole
derivatives which can be obtained in up to 70% yield
from accessible 2-chlorovinyl methyl ketone and
2-chlorovinyl chloromethyl ketone [2, 3] and 1,1-di-
methylhydrazine.
molecular attack by the nucleophilic dimethylamino
group on the -carbon atom of the vinyl group.
N,N-Dimethylpyrazolium chloride thus formed
undergoes transquaternization by the action of the
second dimethylhydrazine molecule.
3-Chloromethyl-1-methylpyrazole. To a solution
of 1.2 g of 1,1-dimethylhydrazine in 50 100 ml of
dry diethyl ether we slowly added 1.39 g of 1,4-di-
chloro-3-buten-2-one at such a rate that the mixture
did not boil. When the exothermic reaction was com-
plete, the mixture was stirred for 0.5 2 h. The yield
of trimethylhydrazinium chloride (which precipitated
from the mixture) was 0.96 g (88%). mp 261 262 C
{published data [4]: mp 245 C with decomposition
(from EtOH EtOAc)}. The filtrate was evaporated,
and the product was purified by column chromatog-
raphy on silica gel or by distillation. Yield 0.91 g
(70%). bp 146 148 C, n2D0 1.5275. H NMR spec-
1
trum, , ppm: 7.324, 7.319 (4-H), 6.278 and 6.274
(5-H), 4.58 (CH2Cl), 3.86 (CH3N). 13C NMR
spectrum, C, ppm: 148.37 (C3), 130.97 (C5), 105.08
(C4), 76.83 (CH2Cl), 38.62 (CH3N). Found, %:
C 45.78; H 5.24; N 21.47. C5H7ClN2. Calculated,
%: C 45.99; H 5.40; N 21.45.
R = Me, CH2Cl.
The reactions were carried out at a reactant ratio
of 1: 2 in an organic solvent and were accompanied
by heat evolution. The second product was 1,1,1-tri-
methylhydrazinium chloride which was isolated in
90% yield. When the reaction was performed with
equimolar amounts of the reactants, we also obtained
the corresponding pyrazole and trimethylhydrazinium
chloride, but the conversion of the initial chlorovinyl
ketone was smaller. The scheme of the process is
likely to include initial formation of 2-chlorovinyl
ketone dimethylhydrazone, followed by intra-
1,3-Dimethylpyrazole. Following the above proce-
dure, from 1.2 g of 1,1-dimethylhydrazine and 1.04 g
of 4-chloro-3-buten-2-one in 50 100 ml of dry hexane
we obtained 0.9 g of trimethylhydrazinium chloride
and 0.84 g (64%) of 1,3-dimethylpyrazole. bp 136
138 C, n2D0 1.4674 [5], d240 0.9626 [5].
The NMR spectra were recorded on a Bruker DPX-
400 spectrometer in CDCl3 using tetramethylsilane as
internal reference.
1070-4280/01/3712-1795$25.00 2001 MAIK Nauka/ Interperiodica
Levkovskaya
