Solvent Effects in the Electrophilic Amination of Mesitylene with the System NaN3-AlCl3-HCl

Full text of DOI:10.1023/A:1026046304607

Russian Journal of Organic Chemistry, Vol. 39, No. 5, 2003, pp. 747 749. Translated from Zhurnal Organicheskoi Khimii, Vol. 39, No. 5, 2003,
pp. 793 794.
Original Russian Text Copyright
2003 by Borodkin, Popov, Pokrovskii, Shubin.
SHORT
COMMUNICATIONS
Solvent Effects in the Electrophilic Amination of Mesitylene
*
with the System NaN AlCl HCl
3
3
1,2
1,2
1
1
G. I. Borodkin , S. A. Popov , L. M. Pokrovskii , and V. G. Shubin
1
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
2
Novosibirsk State University, Novosibirsk, Russia
Received July 5, 2002
Substitution of hydrogen in an aromatic ring by
amino group is usually a two-step process which
implies introduction of a temporary functional group
or atom [2 4]. In the recent years, an interest has
grown in direct electrophilic amination of arenes (see
excess aromatic substrate was used as solvent. When
the reaction was carried out in hexane, the yield of
aromatic amine was lower, while 1,2-dichloroethane
and nitromethane were shown [7] to be inappropriate
solvents because of strong complex formation with
the catalytic system.
[
5, 6] and references therein). A convenient reagent
for direct electrophilic amination is sodium azide
which is used under conditions of acid catalysis [7].
Olah et al. [7] studied electrophilic amination of
benzene and its derivatives with the system NaN3
The goal of the present work was to study solvent
effect in the direct electrophilic amination of
mesitylene with the system NaN AlCl HCl. The
most probable mechanisms of this reaction are shown
in Scheme 1 (cf. [7]). According to this scheme, in
3
3
AlCl HCl. The best results were obtained when
3
Scheme 1.
_
*
___________
For preliminary communication, see [1].
1
070-4280/03/3905-0747$25.00 2003 MAIK Nauka/Interperiodica

7
48
BORODKIN et al.
Conversions of mesitylene ( )a in the amination with
the system NaN3 AlCl3 HCl and solvent parameters
data in table show that the conversion of mesitylene
falls down in the series CH Cl > CHCl > CCl ,
2
2
3
4
(
dielectric constants
and donor numbers DN)
ClCH CH Cl > Cl CHCHCl , and CH Cl > CH Br ,
which are consistent with the assumption that NH2
ion is the reactive intermediate species.
Apart of the number of heavy atoms N in solvent
molecule, the conversion of mesitylene should depend
on dielectric constant of the solvent. This follows
from the existence of the two-parameter correlation
2 2 2 2 2 2 2 2
+
Solvent
[10]
1.89
1.92
2.02
4.70
8.9
DN [8]
Hexane
0
0
0
0.40
0.44
0.47
0.23
0.65
0.10
0.86
0.42
0.31
0.44
<0.04
<0.04
0
Heptane
Cyclohexane
CHCl3
CH Cl2
= (0.29 0.08) + (0.067 0.010)
(0.107 0.023)NCl;
2
CCl4
2.23
10.4
0
0.1
r = 0.97, s = 0.08, n = 9;
ClCH CH Cl
2
2
Cl CHCHCl2
8.2
7.93
6.7
2
where is the mole fraction of 2,4,6-trimethylaniline,
and NCl is the number of chlorine atoms in solvent
molecule. A considerable contribution of the term
including , which characterizes solvent polarity, is
consistent with the above presumed ionic mechanism.
General procedure for direct electrophilic
amination of mesitylene with the system NaN3
b
ClCH CCl3
2
CH Br2
2
THF
PhNO2
7.32
35
20.0
4.4
Sulfolane
CH Cl MeNO
2
44
14.8
2.7c
c
38.6
0.02
2
2
AlCl HCl. A suspension of 3.65 mmol of dry
3
(
1: 1, v/v)
sodium and 3.65 mmol of anhydrous AlCl in 3.5 ml
3
a
of appropriate dry solvent was stirred for 20 h at
room temperature. Mesitylene, 7.3 mmol, was added,
and dry hydrogen chloride was passed through the
mixture at 20 25 C over a period of 2 h. The mixture
was poured onto ice, treated with excess concentrated
aqueous sodium hydroxide, and extracted with diethyl
ether (3 15 ml). The extract was dried over MgSO4,
and the solvent was distilled off. The product com-
position was determined by H NMR spectroscopy
and gas chromatography mass spectrometry.
This study was financially supported by the Rus-
sian Foundation for Basic Research (project no. 02-
stands for the mole fraction of 2,4,6-trimethylaniline
relative to NaN ; given are averaged values determined from
3
1
the H NMR and GC MS data.
b
c
At 40 C [11].
Parameters of MeNO2 are given.
the first stage sodium azide reacts with aluminum
chloride; therefore, solvents capable of coordinating
to AlCl hamper the process. In fact, solvent with
1
3
a large donor number (DN > 2, according to Gutmann
[
8]) ensure low conversion of mesitylene (see table).
The reactive species may be diazonium (I) or nitre-
nium cation (II), and the reaction of the former with
mesitylene could give two -complexes A and B.
03-32431).
REFERENCES
According to AM1 quantum-chemical calculations,
-
complex A is less stable than isomeric -complex B
1
2
.
.
Borodkin, G.I., Popov, S.A., and Shubin, V.G., Int.
Conf. Reaction Mechanisms and Organic Inter-
mediates. Book of Abstracts, St. Petersburg, 2001,
p. 87; Borodkin, G.I., Popov, S.A., and Shubin, V.G.,
Abstracts of Papers, Mezhdunarodnaya konferentsiya
Sovremennye problemy organicheskoi khimii (Int.
Conf. Current Problems of Organic Chemistry ),
Novosibirsk: Sib. Otd. Ross. Akad. Nauk, 2001, p. 71.
Lindsey, R.J., Comprehensive Organic Chemistry,
Barton, D. and Ollis, W.D., Eds., Oxford: Pergamon,
1979, vol. 2. Translated under the title Obshchaya
organicheskaya khimiya, Moscow: Khimiya, 1982,
vol. 3, p. 168.
(
H = 979.3 and 801.9 kJ/mol, respectively); there-
f
fore, the formation of complex B is more favorable.
-
bond (3.25 ), so that it resembles -complex C.
The latter is formed by reaction of nitrenium ion II
with mesitylene. It is known that the ground state of
2
Complex B is characterized by a very long H N N2
+
2
NH ion is triplet; its energy is by 125.9 kJ/mol lower
than that of the singlet state [9]. Taking into account
that the formation of -complex C requires singlet
state of nitrenium ion, the conversion of mesitylene
should depend on the probability for singlet triplet
inversion of the cation. This probability should
increase with rise in the number of heavy atoms in
solvent molecule and their atomic number [5]. The
3. Methoden der organischen Chemie (Houben Weyl),
Stuttgart: Georg Thieme, 1957, vol. XI/1, p. 21.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 5 2003

SOLVENT EFFECTS IN THE ELECTROPHILIC AMINATION OF MESITYLENE
749
4
5
6
7
.
.
.
.
Krohn, K., Nachr. Chem. Tech. Lab., 1987, vol. 35,
p. 1047.
Translated under the title Khimiya koordinatsionnykh
soedinenii v nevodnykh rastvorakh, Moscow: Mir,
1
971, p. 22.
Simonova, T.P., Nefedov, V.D., Toropova, M.A., and
Kirillov, N.F., Usp. Khim., 1992, vol. 61, p. 1061.
9
.
Gibson, S.T., Greene, J.P., and Berkowitz, J.,
J. Chem. Phys., 1985, vol. 83, p. 4319.
Takeuchi, H., Taniguchi, T., and Ueda, T., J. Chem.
Soc., Perkin Trans. 2, 2000, p. 295.
1
1
0. Gordon, A.J. and Ford, R.A., The Chemist’s Compa-
nion, New York: Wiley, 1972. Translated under the
title Sputnik khimika, Moscow: Mir, 1976, p. 11,
Mertens, A., Lammertsma, K., Arvanaghi, M., and
Olah, G.A., J. Am. Chem. Soc., 1983, vol. 105,
p. 5657.
1. Promyshlennye khlororganicheskie produkty. Spra-
vochnik (Large-Scale Organochlorine Products.
Reference Book), Oshin, L.A., Ed., Moscow:
Khimiya, 1978, p. 145.
8
.
Gutmann, V., Coordination Chemistry in Non-
aqueous Solutions, New York: Springer, 1968.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 5 2003