Specificity of acid hydrolysis of 2-benzylidenehydrazino-4,6- dimethylpyrimidine

Full text of DOI:10.1134/S1070363209040355

ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 4, pp. 872–873. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © A.V. Erkin, V.I. Krutikov, 2009, published in Zhurnal Obshchei Khimii, 2009, Vol. 79, No. 4, pp. 699–700.
LETTERS
TO THE EDITOR
Specificity of Acid Hydrolysis of 2-Benzylidenehydrazino-
4,6-dimethylpyrimidine
A. V. Erkin and V. I. Krutikov
St. Petersburg State Institute of Technology, Moskovskii pr. 26, St. Petersburg, 190013 Russia
e-mail: kruerk@yandex.ru
Received May 29, 2008
DOI: 10.1134/S1070363209040355
We examined a procedure for the synthesis of 2-
hydrazino-4,6-dimethylpyrimidine (I), which differs
from the traditional method [1]. The procedure is
based on acid hydrolysis of readily accessible 2-
benzylidenehydrazino-4,6-dimethylpyrimidine (II). Com-
pound II can be obtained by high-temperature
condensation of benzylideneaminoguanidine with pen-
tane-2,4-dione under solvent-free conditions. However,
the hydrolysis of benzylidenehydrazine II gave no
expected product I, but resulted in partial formation of
2-hydrazino-4-methyl-6-(2-phenylethenyl)-pyrimidine
(III) despite continuous removal of liberated
benzaldehyde from the reaction zone.
stretching vibrations of double bond conjugated with
aromatic ring (1581 cm–1), and out-of-plane bending
vibrations of C–H bonds at the trans-ethylene bond
(968 cm–1). Compound III displayed in the UV
spectrum a very strong asymmetric absorption band
with its maximum at λ 297 nm (logε 4.33) and a
shoulder at about λ 340 nm (logε 4.12), originating
from π–π and p–π* transitions in the entire conjugation
system. The presence of an unsubstituted hydrazino
group in molecule III was confirmed by the formation
of a brightly colored condensation product with
ninhydrin.
2-Benzylidenehydrazino-4,6-dimethylpyrimidine
(II). A mixture of 16.2 g of benzylideneamino-
guanidine and 10 g of pentane-2,4-dione was heated to
135°C and was vigorously stirred for 30 min at that
temperature. The resulting semicrystalline material
was ground with 300 ml of water, and the precipitate
was filtered off, washed with water, recrystallized from
70% ethanol, and dried for 10 h at 70°C. Yield 11 g
(49%), mp 164°C; published data [2]: mp 161°C; Rf
0.74. 1H NMR spectrum, δ, ppm: 2.31 s (6H, Me), 6.49
s (1H, CH), 7.25–7.68 m (5H, Ph), 8.05 s (1H, NH),
10.91 s (1H, CH=N).
Me
N
Ph
N
N
N
Me
H
II
Me
N
H2N
N
H
N
Ph
2-Hydrazino-4-methyl-6-(2-phenylethenyl)pyrim-
idine (III). A solution of 4.52 g of benzylidene-
hydrazine II in dilute (1:1) hydrochloric acid was
heated to the boiling point, and direct steam was
passed through the solution over a period of 2 h with
simultaneous removal of liberated benzaldehyde. The
mixture was filtered, the filtrate was evaporated to
dryness under reduced pressure, the residue was
dissolved in 60 ml of water, and the solution was
filtered and made persistently alkaline by adding 25%
III
The structure of styryl-substituted pyrimidine III
1
was confirmed by spectral and analytical data. Its H
NMR spectrum contained a broadened singlet at about
δ 4.1 ppm due to protons in the primary amino group,
and protons at the exocyclic double C=C bond
resonated as doublets at δ 6.9–7.0 and 7.7–7.8 ppm. In
the IR spectrum of III we observed absorption bands
corresponding to N–H bending vibrations (1636 cm–1),
872

SPECIFICITY OF ACID HYDROLYSIS
873
aqueous ammonia. An oily material separated and was
ground with 20 ml of water, and the precipitate was
filtered off and dried in air. We thus isolated 0.76 g
(17%) of crude pyrimidine III. An analytical sample
was obtained by double recrystallization from benzene,
followed by recrystallization from benzene–hexane
(5:4) and drying under reduced pressure. Yield 178 mg
(3.9%), mp 154°C, Rf 0.83. 1H NMR spectrum, δ, ppm:
2.30 s (3H, Me), 4.13 br.s (2H, NH2), 6.57 s (1H, CH),
6.97 d (1H, CH=CH), 7.28–7.60 m (5H, Ph), 7.76 d
(1H, CH=CH), 7.81 br.s (1H, NH). Found, %: C 69.09;
H 6.31; N 24.33. C13H14N4. Calculated, %: C 69.00; H
6.24; N 24.76.
measured in KBr on a Shimadzu FTIR-8400S
instrument. The UV spectra were obtained on an SF-26
spectrophotometer from solutions in ethanol with a
concentration of ~10–4 M. The elemental composition
was determined on a Leco CHNS-932 CHN analyzer.
The purity of the products was checked by TLC on
Silufol UV-254 plates using butan-1-ol–acetic acid–
water (1:1:1) as eluent; spots were visualized under
UV light.
REFERENCES
1. Boarland, M.P.V., McOmie, J.F.W., and Timms, R.N.,
J. Chem. Soc., 1952, no. 12, p. 4691.
1
The H NMR spectra were recorded on a Bruker
2. Bower, J.D. and Doyle, F.P., J. Chem. Soc., 1957, no. 2,
AC-400 spectrometer at 400.13 MHz using DMSO-d6
as solvent and reference. The IR spectra were
p. 727.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 4 2009