ISSN 1070-4280, Russian Journal of Organic Chemistry, 2013, Vol. 49, No. 6, p. 933. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © V.M. Ismailov, F.N. Nagiev, N.N. Yusubov, 2013, published in Zhurnal Organicheskoi Khimii, 2013, Vol. 49, No. 6, p. 946.
SHORT
COMMUNICATIONS
Convenient Synthesis
of 3-Amino-2-hydroxy-5-methylbenzenesulfonic Acid
V. M. Ismailov, F. N. Nagiev, and N. N. Yusubov
Baku State University, ul. Z. Khalilova 23, Baku, AZ-1148, Azerbaijan
e-mail: niftali-yusubov@rambler.ru
Received August 28, 2012
DOI: 10.1134/S1070428013060249
Amino-substituted benzenesulfonic acids are im-
portant building blocks for the synthesis of pharma-
cologically active derivatives of sulfanilic acid.
Under analogous conditions, 2,5-dimethoxyphenyl
methyl ketone oxime was converted into 2,5-dime-
thoxyaniline, but no sulfonation was observed.
4
-Aminobenzenesulfonic acids are commonly prepared
Scheme 2.
by sulfonation of aniline with sulfuric acid. This proce-
dure is applicable to the synthesis of 4- and 2-amino-
benzenesulfoinic acids.
OH
OH
N
OH
H
N
Me
H
2
SO
4
Me
We have found a new method for the preparation of
O
O
3
2
-aminobenzenesulfonic acid derivative via reaction of
-hydroxy-5-methylphenyl methyl ketone oxime with
Me
Me
excess sulfuric acid. By heating that oxime and
6
2
OH
H
0% sulfuric acid in an inert solvent over a period of
h we obtained 3-amino-2-hydroxy-5-methylbenzene-
Me
N
SO H
H
2
SO
4
3
H
2
I
O
sulfonic acid (I) (Scheme 1).
Me
Scheme 1.
OH
Me
Scheme 3.
OH
N
OH
OH
OH
Me
H
2
N
3
SO H
H SO , 60–80°C
2
4
H N
SO H
H N
SO3
2
3
3
H O
2
·
H O
2
Me
Me
Me
I
3
-Amino-2-hydroxy-5-methylbenzenesulfonic
acid (I). A mixture of 16.5 g (0.1 mol) of 2-hydroxy-
-methylphenyl methyl ketone oxime in 20 ml of
The reaction is likely to involve Beckmann rear-
rangement of the initial oxime with formation of the
corresponding acetanilide which undergoes sulfonation
at the ortho position with respect to the hydroxy group
and hydrolysis of the amide group (Scheme 2).
5
aqueous acetone and 9.8 g (0.1 mol) of 60% sulfuric
acid was heated for 2 h under reflux. After removal of
acetone, crystals separated from the aqueous phase and
were filtered off, mp >300°C (decomp.); the product
was insoluble in organic solvents and soluble in hot
water. Found, %: N 7.11; S 15.34. C H O NS. Calcu-
1
13
According to the H and C NMR data, compound
I was isolated as an inner salt containing one solvate
1
water molecule (Scheme 3). The H NMR spectrum of
7
9
4
I contained two singlets at δ 7.09 and 7.32 ppm due to
aromatic protons, a singlet at δ 2.15 ppm from the
methyl protons, and broadened signals at 3.8, 9.5,
lated, %: N 6.89; S 15.76.
1
The H NMR spectra were recorded on a Bruker
A-300 spectrometer at 300 MHz using tetramethyl-
11.1 ppm, which were assigned to protons in the am-
monium and OH groups and hydration water.
silane as internal reference and CDCl as solvent.
3
9
33