ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 6, pp. 934–935. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © G.I. Borodkin, I.R. Elanov, V.G. Shubin, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 6, pp. 946–947.
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Electrophilic Amination of Methylbenzenes with Sodium Azide
in Trifluoromethanesulfonic Acid
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
e-mail: gibor@nioch.nsc.ru
Received June 2, 2008
DOI: 10.1134/S1070428009060220
We previously found that the nature of solvent and
Lewis acid strongly affects the yield of the amination
products of methylbenzenes in the system NaN3–
MHlgn–HCl [1–4]. The most effective solvents were
methylene chloride and 1,2-dichloroethane [1–3], as
well as ionic liquids [4]. Takeuchi et al. [5] reported on
electrophilic amination of arenes using hydrazoic acid
and CF3SO3H–CF3CO2H–CHCl3 mixture as solvent.
(75% at a ratio of 4:1). Therefore, we used 3 equiv of
trifluoromethanesulfonic acid in the amination of other
methylbenzenes.
Methyl-substituted benzene was added to trifluoro-
methanesulfonic acid, sodium azide was then added to
a molar ratio of 1:3:1, and the mixture was subjected
to ultrasonic irradiation over a period of 8–11 h and
was additionally kept for 4 days at room temperature.
The mixture was then treated with a small amount of
water, excess 30% aqueous sodium hydroxide was
added, the mixture was extracted with diethyl ether,
the extract was dried over MgSO4, and the solvent was
distilled off. The yields of the resulting methyl-sub-
stituted anilines were as follows: from toluene, 66%
(o/m/p ratio 55:9:36); from o-xylene, 70% (ratio of
2,3- and 3,4-dimethylanilines 44:56); from m-xylene,
70% (ratio of 2,4-, 2,6-, and 3,5-dimethylanilines
71:24:5), from p-xylene, 50%; from durene, 21%;
from pentamethylbenzene, 24%. The product composi-
tion was determined by 1H NMR spectroscopy (Bruker
AC-200 and AV-300) and GC–MS (Hewlett–Packard
G 1800A). A Branson 1510 instrument was used for
ultrasonic irradiation.
Ecological and economic aspects force chemists to
minimize amount of solvent and even exclude it while
carrying out chemical reactions [6]. The goal of the
present work was to effect direct amination of arenes
with the system sodium azide–trifluoromethanesul-
fonic acid using stoichiometric or nearly stoichiometric
amounts of the reactants. We previously presumed
[1–4] that the reactive species in electrophilic amina-
tion is nitrenium ion which is generated from sodium
azide and trifluoromethanesulfonic acid according to
the scheme shown below. As follows from this scheme,
the molar ratio CF3SO3H–NaN3 should be equal to 2.
The amination with CF3SO3H–NaN3 taken at the
above ratio was successful only in the case of very
active substrate, mesitylene, and the corresponding
product, 2,4,6-trimethylaniline was obtained in 61%
yield. The yield increased to 72% when the molar ratio
CF3SO3H–NaN3 was raised to 3:1, while further
raising the reactant ratio almost did not affect the yield
Thus we have demonstrated that electrophilic
amination can be successfully performed using stoi-
chiometric amounts of the reactants (CF3SO3H, NaN3,
and arene as substrate).
CF3SO3H
NaN3
+
CF3SO3H
HN3
+
CF3SO3Na
H2NN2 CF3SO3
H2N+ CF3SO3
–N2
NH2
H
NH2
NH2
–H+
Men
Men
Men
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