Oxidation of aldehydes and ketones into carboxylic acids and esters using 4-amino-2-chloroperbenzoic acid supported on silica gel

Article abstract of DOI:10.1081/SCC-200054215

4-Amino-2-chloroperbenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of aldehydes and ketones to the corresponding carboxylic acids and esters. Copyright Taylor & Francis, Inc.

Full text of DOI:10.1081/SCC-200054215

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Oxidation of Aldehydes and Ketones
into Carboxylic Acids and Esters Using
4‐Amino‐2‐Chloroperbenzoic Acid Supported
on Silica Gel
a
b
a
Mohammed M. Hashemi , Dadkhoda Ghazanfari , Yousef Ahmadibeni
,
a
b
Zahed Karimi‐Jaberi & Ali Ezabadi
a
Department of Chemistry , Sharif University of Technology , Tehran, Iran
Department of Chemistry, Science and Research Branch , Islamic Azad
b
University , Tehran, Iran
Published online: 16 Aug 2006.
To cite this article: Mohammed M. Hashemi , Dadkhoda Ghazanfari , Yousef Ahmadibeni , Zahed
Karimi‐Jaberi & Ali Ezabadi (2005) Oxidation of Aldehydes and Ketones into Carboxylic Acids and Esters
Using 4‐Amino‐2‐Chloroperbenzoic Acid Supported on Silica Gel, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 35:8, 1103-1107, DOI: 10.1081/
SCC-200054215
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Synthetic Communications , 35: 1103–1107, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200054215
Oxidation of Aldehydes and Ketones into
Carboxylic Acids and Esters Using
4
-Amino-2-Chloroperbenzoic Acid
Supported on Silica Gel
Mohammed M. Hashemi
Department of Chemistry, Sharif University of Technology, Tehran, Iran
Dadkhoda Ghazanfari
Department of Chemistry, Science and Research Branch, Islamic Azad
University, Tehran, Iran
Yousef Ahmadibeni and Zahed Karimi-Jaberi
Department of Chemistry, Sharif University of Technology, Tehran, Iran
Ali Ezabadi
Department of Chemistry, Science and Research Branch, Islamic Azad
University, Tehran, Iran
Abstract: 4-Amino-2-chloroperbenzoic acid supported on silica gel was found to
be a versatile and efficient oxidant for the oxidation of aldehydes and ketones to the
corresponding carboxylic acids and esters.
Keywords: Oxidation, 4-amino-2-chloroperbenzoic acid, aldehydes, ketones
Traditionally, solids, especially chromatographic adsorbents, have been used
in reactions to provide a surface on which a reagent spread out. Empirically,
Received in the U.K. October 4, 2002
Address correspondence to Mohammed M. Hashemi, Department of Chemistry,
Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran. E-mail:
mhashemi@sharif.edu

1
104
M. M. Hashemi et al.
such procedures were often found to provide high yields under mild
conditions. The ease of setup and workup was often matched only by the clean-
[
1,2]
liness of the reactions.
choice of the solid, except to make sure that it offered ample active surface.
However, little thought appeared to go into the
[3]
Progress in surface science, the improved understanding of heteroge-
nous catalysis, and the availability of numerous new solids provide opportu-
nities for better design of catalysts as well as supported reagents, which
can lead to enhanced performance in these processes. Microporous solids
such as silica gel offer a wide range of active sites for supporting reagents
and most can often be regenerated if deactivated during a reaction.
Silica gel as an inorganic support has been used in various chemical
[
1–6]
reactions.
However, there are few examples of chemical reactions for
supporting organic molecules on silica gel as oxidizing agents.
The oxidation of aldehydes to corresponding carboxylic acid and
Baeyer–Villiger oxidation of ketones has been widely investigated and
[7]
numerous procedures are known.
In course of our systematic study on the development of supported
[8–18]
reagents and catalysts for the oxidation of organic compounds,
we
herein report a novel heterogeneous oxidant based on 4-amino-2-chloroper-
benzoic acid supported on silica gel through Si-N bonding as an efficient
and convenient oxidant for the oxidation of aldehydes and ketones to the
corresponding carboxylic acids and esters in good yields (Scheme 1). Silica-
gel-supported 4-amino-2-chloroperbenzoic acid can be prepared in the
reaction of 4-amino-2-chlorobenzoic acid with activated silica gel (by Si-N
bond formation), which is then oxidized to 4-amino-2-chloroperbenzoic
acid using hydrogen peroxide as an oxidant.
The oxidation of aldehydes and ketones is performed in dichloromethane
as solvent and workup is a simple extraction and separation of the heterogeneous
supported oxidant by filtration. Removal of the solvent, followed by purifica-
tion of products by column chromatography, gives carboxylic acids and esters
in good yields. Representative reaction times and yields are given in Table 1.
Table 2 shows reusability of this heterogeneous supported-oxidant system
after we replicated oxidation of benzaldehyde to benzoic acid three times. In
each experiment, the supported 4-amino-2-chlorobenzoic acid was recovered
quantitatively.
In summary, mild reaction conditions, good yields, ease of workup, and
reusability of supported reagent are the most significant benefits of this method.
Scheme 1.

Aldehydes and Ketones into Carboxylic Acids and Esters
1105
Table 1. Oxidation of aldehydes and ketones with silica-gel-supported 4-amino-2-
chloroperbenzoic acid
Mp or Bp 8C
Time
(h)
Yield
b
(%)
a
[19]
Substrate
Product
Found Reported
C
6
H
5
CHO
4
6
6
4
4
C
6
H
5
CO
2
H
90
72
75
92
78
78
77
70
82
61
121
145
239
183
75
122.4
146
241
2
4
4
-(NO )C
2
6
H
4
CHO
2-(NO )C
2
6
H
4
2
CO H
-(NO )C H CHO
2
4-(NO )C H CO H
2
6
4
6
4
2
-(CH O)C
3
6
H
4
CHO
4-(CH
3
O)C
6
H
4
CO
2
H
184–186
76
141
C
6
H
5
CH
2
CHO
C
6
H
5
CH
2
CO
2
H
C H CHO
4.5 C H CO H
140
161
194.5
70
2
2
5
2
2
5
2
C
H
5
CH
2
CHO
H
4.5
5
C
H
5
CH
2
CO
2
5
H
162.5
196.7
69
CH
3
COC
6
5
3 2 6
CH CO C H
C H COC H
6
5
C H CO C H
6 5 2 6
5
6
5
5
CH COC H
3
7
CH CO C H
2 2 5
76
77
2
5
3
a 1
All compounds were fully characterized by their mp or bp, and IR and H-NMR
spectra.
b
Yields refer to pure isolated products.
EXPERIMENTAL
Activation of Silica Gel
Chromatographic-grade silica gel (10 g, 70–230 mesh) was heated in an
electric furnace at 6808C for 3 h. Then, it was cooled to room temperature
to obtain 9.3 g of activated silica gel.
Support of 4-Amino-2-Chlorobenzoic Acid on Activated Silica Gel
To a stirring solution of 4-amino-2-chloro benzoic acid (3.43 g, 20 mmol) in
1
00 mL of ethyl acetate, activated silica gel (9.3 g) was added, and the
a
Table 2. Reusability of silica-gel-supported 4-amino-2-chloroperbenzoic acid
Entry
Substrate
Product
Yield (%)
1
2
3
C
C
6
H
H
5
CHO
CHO
C
C
6
H
H
5
CO
CO
2
H
H
90
85
83
6
5
6
5
2
C H CHO
6
C H CO H
6 5 2
5
a
All reactions were carried out under the typical procedure.

1
106
M. M. Hashemi et al.
mixture was refluxed with stirring for 20 h. Then, the mixture was cooled to
room temperature and filtered. The solid material was continously extracted
with ethyl acetate in a Soxhlet apparatus for 14 h to extract the probable
unreacted 4-amino-2-chlorobenzoic acid. Then, it was filtered and dried
in an oven at 808C for 5 h to yield 11.34 g silica-gel-supported 4-amino-2-
chlorobenzoic acid. 4-Amino-2-chlorobenzoic acid (2.04 g, 11.2 mmol) was
supported on 9.30 g of activated silica gel.
Oxidation of Silica-Gel-Supported 4-Amino-2-Chlorobenzoic Acid
to the Corresponding Peracid
Silica-gel-supported 4-amino-2-chloro benzoic acid (8.33 g) that contained
1
.50 g of 4-amino-2-chlorobenzoic acid was added to a stirring solution of
commercial 30% hydrogen peroxide at room temperature and the reaction
mixture was stirred for 9 h. Then, it was filtered through a sintered-glass
funnel. The residue was washed with 5 Â 20 mL of distilled water and the
solid material was dried at room temperature in vacuum (40 torr) to obtain
8
.46 g of silica-gel-supported 4-amino-2-chloroperbenzoic acid. In the
21
2
1
IR spectrum of this supported reagent, signals at 890 cm and 1560 cm
correspond to Si-N stretching bond energy.
Oxidation of Benzaldehyde to Benzoic Acid, Typical Procedure
Benzaldehyde (0.53 g, 5.0 mmol) was disolved in 60 mL of dichloromethane
and one drop of hydrochloric acid (0.1 N) was added to this solution. Then,
silica-gel-supported 4-amino-2-chloroperbenzoic acid (6.20 g containing
6.3 mmol of 4-amino-2-chloroperbenzoic acid) was added, and the mixture
was stirred at room temperature for 4 h. The progress of the reaction was
monitored by TLC. Then, the reaction mixture was filtered and the residue
was washed with 2 Â 10 mL of dichloromethane. The filtrate was evaporated
to give the crude solid product, which was purified by column chromatography
on silica gel (methanol-dichloromethane, 4:1, v/v) to obtain 0.55 g (4.5 mmol,
90% yield) of pure benzoic acid.
Reusability of Silica-Gel-Supported 4-Amino-2-
Chloroperbenzoic Acid
After using silica-gel-supported 4-amino-2-chloroperbenzoic acid as an
oxidant for the oxidation of aldehydes and ketones, it can be reconverted to
corresponding peracid derivative by treatment with hydrogen peroxide. In a
typical procedure, silica-gel-supported 4-amino-2-chloroperbenzoic acid

Aldehydes and Ketones into Carboxylic Acids and Esters
1107
was reoxidized after the first use for the oxidation of benzaldehyde to benzoic
acid with hydrogen peroxide according to the mentioned procedure and was
used again for the oxidation of benzaldehyde to benzoic acid. The second
and third use of this procedure for the oxidation of benzaldehyde to benzoic
acid showed little decrease in the reaction yields, (see Table 2).
The silica-gel-supported 4-amino-2-chlorobenzoic acid was retrieved
quantitatively after each experiment.
ACKNOWLEDGMENT
Financial support from the Research Council of Science and Research Branch
of Islamic Azad University is gratefully acknowledged.
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