Non-catalytic alkylation of benzylamine with 1,3,5-trimethyl-1H-pyrazol-4- ylmethanol

Full text of DOI:10.1134/S1070363213060352

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 6, pp. 1178–1179. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © H.S. Attaryan, V.I. Rstakyan, S.S. Hayotsyan, G.V. Asratyan, 2013, published in Zhurnal Obshchei Khimii, 2013, Vol. 83, No. 6,
pp. 1048–1049.
LETTERS
TO THE EDITOR
Non-catalytic Alkylation of Benzylamine
with 1,3,5-Trimethyl-1H-pyrazol-4-ylmethanol
H. S. Attaryan, V. I. Rstakyan, S. S. Hayotsyan, and G. V. Asratyan
Institute of Organic Chemistry, Research and Technology Center of Organic and Pharmaceutical Chemistry,
National Academy of Sciences of Armenia, pr. Azatutyana 26, Yerevan, 0014 Armenia
e-mail: vrstakyan@gmail.com
Received July 16, 2012
DOI: 10.1134/S1070363213060352
We previously showed [1] that non-catalytic
alkylation of aniline with 1,3,5-trimethyl-1H-pyrazol-
4-ylmethanol (I) involves the nitrogen atom of aniline
with formation of the corresponding N-pyrazolyl-
methyl derivative, whereas no C-alkylated derivative
was isolated. We presumed that the alkyla-tion of
benzylamine with 1,3,5-trimethyl-1H-pyrazol-4-yl-
methanol (I) should also lead N-alkylation product.
The reaction was carried out by heating com-pound I
with a large excess of benzylamine at the boiling point
in the absence of solvent and catalyst. As a result,
instead of the expected N-(pyrazolylmethyl)-
benzylamine II, from the reaction mixture, by vacuum
distillation, we isolated dipyrazolylmethane (IV) and
NH
Me
H2N
OH
Me
N
Me
II
N
Δ
N
+
Me
Me
N
Me
Me
N
Me
I
O
N
Me
Me
_H2O
N
N
Me Me
III
Me
N Me
Me
N
CH2O
Me
_CH2O
N
N
Me
Me
IV
N
H2C
N
CH2
HC
N
CH3
PhCH2NH2
+
CH3NH2
VII
V
VI
1178

NON-CATALYTIC ALKYLATION OF BENZYLAMINE
1179
N-benzylidenebenzylamine (VII). The formation path
of bis(1,3,5-trimethyl-1H-pyrazol-4-yl)methane (IV)
was studied by us in detail in [2].
reflux. After removal of excess benzylamine, the
residues was distilled under reduced pressure to isolate
1.5 g (64%) of compound VII with bp 140°C (2 mm),
nD20 = 1.600 [5]. H NMR spectrum, δ, ppm: 4.78 d
1
Thus we have shown that compound I in the reac-
tion with benzylamine acts as a source of formal-
dehyde [2] rather than as alkylating agent (in contrary
to the reactions with phenol and aniline [1, 3]).
Formaldehyde generated in situ reacts with benzyl-
amine to produce intermediate N-methylidenebenzyl-
amine (V), triadic prototropic rearrangement of the
latter yields N-benzylidenemethanamine (VI) [4], and
the final amine exchange reaction between VI and
benzylamine leads to compound VII via elimination of
methanamine.
(2H, CH2, J = 1.3), 7.17–7.32 m (5H, C6H5), 7.37–7.42
m (3H, Ph), 7.73–7.78 m (2H, Ph), 8.40 t (1H, N=CH,
J = 1.3). Found, %: C 86.45; H 6.20; N 7.43. C14H13N.
Calculated, %: C 86.15; H 6.66; N 7.07. In addition,
2.3 g (50%) of dipyrazolylmethane IV [2] was isolated
from the reaction mixture; mp 87°C (from petroleum
ether).
The IR spectra were recorded on a Specord 75 IR
1
spectrometer from thin films. The H NMR spectra
were measured on a Varian Mercury-300 instrument at
300 MHz using DMSO-d6 as solvent.
The structure of VII was confirmed by the IR and
1H NMR data. The IR spectrum of VII character-
istically contained absorption bands due to stretching
vibrations of the HC=N bond at 1640 cm–1 and
benzene ring at 1500–1600 cm–1. In the 1H NMR spec-
trum of VII, the CH2 group gave a signal at δ 4.82 ppm,
the HC=N proton resonated in a weak field (δ 8.40 ppm),
and aromatic proton signals were observed in the
region δ 7.2–7.82 ppm.
REFERENCES
1. Attaryan, H.S., Rstakyan, V.I., Hayotsyan, S.S., and
Asratyan, G.V., Russ. J. Gen. Chem., 2012, vol. 82, no. 1,
p. 172.
2. Baltayan, A.O., Rstakyan, V.I., Attaryan, O.S., and
Asratyan, G.V., Russ. J. Gen. Chem., 2010, vol. 80, no. 6,
p. 1206.
3. Attaryan, O.S., Gevorkyan, A.A., Antanosyan, S.K.,
Panosyan, G.A., and Asratyan, G.V., Russ. J. Gen. Chem.,
2008, vol. 78, no. 3, p. 506.
4. Baddar, T.G. and Iskander, Z., Nature, 1951, vol. 167,
p. 1069.
N-Benzylidenebenzylamine (VII) and bis(1,3,5-
trimethyl-1H-pyrazol-4-yl)methane (IV). A mixture
of 43 g of benzylamine and 6 g of 1,3,5-trimethyl-1H-
pyrazol-4-ylmethanol (I) was heated for 4–5 h under
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 6 2013