Russian Journal of Organic Chemistry, Vol. 40, No. 10, 2004, pp. 1541–1542. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004,
p. 1589.
Original Russian Text Copyright © 2004 by Borodkin, Elanov, Shubin.
SHORT
COMMUNICATIONS
First Example of Using a Ionic Liquid in Electrophilic
Amination of Arenes. Amination of Methylbenzenes
with the System NaN –AlCl –HCl
3
3
G. I. Borodkin, I. R. Elanov, and V. G. Shubin
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
Received May 12, 2004
In the recent years, the use of ionic liquids as
a medium for organic reactions has attracted increasing
interest [1]. Ionic liquids are considered to be “green”
solvents which possess a combination of unique
properties, such as low volatility and toxicity and high
thermal and chemical stability and polarity. The latter
property makes them especially attractive for carrying
out heterolytic reactions, in particular electrophilic
aromatic substitution. Up to now, ionic liquids have
been used in alkylation and acylation according to
Friedel–Crafts [1], halogenation [1–3], sulfonation [4],
and nitration of arenes [1].
m-xylene, and mesitylene) using 1-butyl-3-methyl-
imidazolium chloride ([BMIm]Cl) in a mixture with
AlCl . It is known that treatment of such systems with
3
gaseous hydrogen chloride endows them with super-
acidic properties [7], which is necessary to generate
+
2
NH cations as reactive species (cf. [5, 6]).
Sodium azide, 3.2 mol, was added to 7 g of ionic
liquid [BMIm]Cl–AlCl (molar ratio 3:4), and the
3
mixture was stirred for 1 h at room temperature.
Methylbenzene, 6.4 mol, was then added, and dry
hydrogen chloride was passed through the mixture
over a period of 0.5–1.5 h under stirring. The mixture
was poured onto ice, treated with excess 30% aqueous
sodium hydroxide, and extracted with diethyl ether
The goal of the present work was to examine the
possibility of using ionic liquids as solvents in electro-
philic amination of arenes. The system NaN –AlCl –
(
4×20 ml). The combined extracts were dried over
3
3
MgSO , and the solvent was distilled off. According to
HCl was found to be convenient for this purpose [5, 6].
The best results were obtained with excess aromatic
substrate [5] or 1,2-dichloroethane [6] as solvent. We
performed amination of methylbenzenes (o-xylene,
4
1
the H NMR data, the yields of the corresponding
amines were as follows: from o-xylene, 65% (a 40:60
mixture of 2,3-dimethyl- and 3,4-dimethylanilines);
from m-xylene, 78% (a 71:24:5 mixture of 2,4-di-
methyl-, 2,6-dimethyl-, and 3,5-dimethylanilines);
NaN3
HCl
+
AlCl3
AlCl N3
2
–NaCl
1
from mesitylene, 76%. The H NMR spectra were
2
recorded from solutions in CDCl using Bruker AC-
3
NH N AlCl
NH AlCl4
2
2
2
4
–
N2
200 and WP-200-SY instruments.
Thus, we have demonstrated the possibility of using
ionic liquids as a solvent in electrophilic amination of
arenes.
H
NH2
NH AlCl4
2
+
This study was performed under financial support
by the Russian Foundation for Basic Research (project
nos. 02-03-32431 and 02-03-32881).
Men
Men
NH2
REFERENCES
–
H+
1
. Ionic Liquids in Synthesis, Wasserscheid, P. and
Men
Welton, T., Eds., Weinheim: Wiley, 2003.
1
070-4280/04/4010-1541 © 2004 MAIK “Nauka/Interperiodica”