Transformation of β-nitrostyrenes to carboxylic acids using amberlyst A-26 supported hydroperoxide

Article abstract of DOI:10.1007/s007060200089

Nitrostyrenes are conveniently converted to the corresponding carboxylic acids in high yields at room temperature with Amberlyst A-26 supported hydroperoxide which is prepared in situ from 35% hydrogen peroxide and amberlyst A-26 (OH^-).

Full text of DOI:10.1007/s007060200089

Monatshefte f u r Chemie 133, 1193±1196 ꢀ2002)
Transformation of b-Nitrostyrenes
to Carboxylic Acids Using Amberlyst
A-26 Supported Hydroperoxide
Moslem M. Lakouraj1 , Barahman Movassagh
and Kyumars Bahrami
;Ã
2;Ã
,
2
1
Institute of Chemistry, Mazandaran University, 47415 Babolsar, Iran
Department of Chemistry, Razi University, 67149 Kermanshah, Iran
2
Summary. Nitrostyrenes are conveniently converted to the corresponding carboxylic acids in high
yields at room temperature with Amberlyst A-26 supported hydroperoxide which is prepared in situ
À
from 35% hydrogen peroxide and amberlyst A-26 ꢀOH ).
Keywords. Nitrostyrenes; Amberlyst A-26; Carboxylic acids; Hydroperoxide.
Introduction
Oxidative cleavage of carbon±carbon double bonds resulting in the formation of
carboxylic acids is of importance in organic chemistry [1]. It is usually accom-
plished with potassium permanganate or tetraalkylammonium permanganate [2],
potassium dichromate in sulfuric acid [3], chromium trioxide in sulfuric acid or
acetic acid [4], sodium hypochlorite [5], ruthenium tetroxide=sodium periodate [6],
and ozonolysis [7]. Over the past two decades, nitroalkenes have been found to be
important intermediates both in industry and in organic chemistry [8]. However, to
the best of our knowledge, neither homogeneous nor heterogeneous oxidations of
nitroalkenes have been reported.
More recently, we have described an ef®cient method for the selective conver-
sion of nitriles to amides and convenient epoxidation of ꢀ,ꢁ-unsaturated ketones
using Amberlyst A-26 supported hydroperoxide [9]. In connection with our re-
search in this area we have investigated the synthetic potential of this polymeric
oxidizing agent for the epoxidation of nitrostyrenes.
Results and Discussion
Surprisingly enough, upon reaction of nitrostyrenes with Amberlyst A-26, carbon±
carbon double bond scission was exclusively observed instead of epoxidation
ꢀ
Scheme 1).
à Corresponding authors. E-mail: mlakouraj@yahoo.com

1
194
M. M. Lakouraj et al.
Scheme 1
‡
À a
Table 1. Conversion of ꢁ-nitrostyrenes to carboxylic acids with Q OOH
b,c
Yield=%
Entry
Ar
t=h
1
2
3
4
5
6
C H
6
10
12
92
91
94
93
95
86
5
4-MeC H
6
4
4-ClC H
6
9.5
4
4-BrC H
6
10
9
4
3-BrC H
6
4
4-PhC H
6
8
4
7
8
9
0
1
2
3
4
5
4-NO
C H
6
789
2
4
4
4
3-NO C H
2
7.5
8
84
82
0
6
2-NO C H
2
6
1
1
1
1
1
1
H NC H
6 4
18
2
ꢀMe) N±C H
6 4
18
10
14
15
12
0
2
2-Naphthyl
89
82
78
83
4-MeOC H
6
4
3,4-ꢀMeO) C H
2
6
3
3-MeOC H
6
4
a
À
Reactions were conducted in dioxane using a ratio of substrate:H O :A-26 ꢀOH ) ˆ 1:4:0.1;
2
2
1
b
c
yields refer to isolated products; all products were characterized by IR, H NMR, and comparison
with authentic samples
A number of examples illustrating this new and convenient procedure for the
oxidation of nitrostyrenes to the corresponding carboxylic acids are summarized
in Table 1. Reactions were performed in 1,4-dioxane by stirring the nitrostyrenes
and commercial 35% hydrogen peroxide in the presence of catalytic amounts of
À
Amberlyst A-26 ꢀOH -form) at room temperature. The work-up is exceedingly
simple and involves merely ®ltration; the yields are high to excellent. However,
nitrostyrenes containing strong electron donating groups at the aromatic ring sys-
tem ꢀTable 1, entries 10 and 11) failed to give any acid, even when the reaction
mixtures were stirred for 18 h. As an explanation of this result we propose that the
charged resonance form in Eq. ꢀ1) strongly decreases the reactivity of the carbon±
carbon double bond toward hydroperoxide ion attack.

Carboxylic Acids from ꢁ-Nitrostyrenes
1195
In the case of 1-nitro-2-ꢀꢁ-naphthyl) ethylene ꢀTable 1, entry 12), 2-naphthal-
dehyde is obtained exclusively. It is worth mentioning that the carbon±carbon
double bond in styrene, ꢀ-methylstyrene, stilbene, methyl methacrylate, and acryl-
amide remains intact under the conditions applied. Therefore, the presence of a
nitro substituent at the carbon±carbon double bond seems essential for the trans-
formation described.
In summary, this method can be used for effective carbon±carbon double bond
cleavage of nitrostyrenes to carboxylic acids under mild conditions. In addition, the
insolubility of the reagent in the reaction media and simple work-up are advantages
of this procedure.
Experimental
1
IR spectra were obtained using a Shimadzu 470 instrument. H NMR spectra were recorded on a JEOL
JNM-PMX 60 MHz NMR spectrometer employing TMS as internal standard. Nitrostyrenes were
À
prepared by a standard method [10]. Amberlyst A-26 ꢀOH -form) was purchased from Merck or
prepared by exchange reaction of the chloride form of the resin with 1.0 N aqueous NaOH. All
products were characterized by comparison of their spectroscopic and physical data with those of
known samples.
General procedure
3
To a suspension of 4.85 mmol nitrostyrene in 5 cm 1,4-dioxane and 0.48mmol amberlyst A-26 ꢀwet,
À
OH -form), 19.4mmol H O ꢀ35% w=v solution) were added. After a few minutes, the reaction
2
2
mixture was stirred magnetically at room temperature for 7±15 h. The progress of the reaction was
monitored by TLC ꢀeluent:n-hexane:acetone ˆ 2:1). After completion of the reaction the mixture was
3
®
ltered. The solid material was washed with 1,4-dioxane ꢀ2Â 5 cm ). Removal of the solvent under
reduced pressure produced the corresponding acid in good yield and almost pure form.
Acknowledgments
We are grateful to the Razi University Research Council for ®nancial support and to the Institute of
Chemistry of Mazandaran University for complementary assistance.
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M. M. Lakouraj et al.: Carboxylic Acids from ꢁ-Nitrostyrenes
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th
[
Received October 5, 2001. Accepted November 28, 2001