Selective reduction of nitro compounds using CeY zeolite under microwaves

Article abstract of DOI:10.5012/jkcs.2010.54.01.055

Aliphatic and aromatic nitro compounds were selectively reduced to their corresponding amino derivatives in good yields using formic acid and CeY zeolite under monomode reactor. This system is found to be compatible with several sensitive functionalities. Beside the recycling result showed it had a long catalyst lifetime and could maintain activity even after being used for 20 cycles.

Full text of DOI:10.5012/jkcs.2010.54.01.055

Journal of the Korean Chemical Society
2
010, Vol. 54, No. 1
Printed in the Republic of Korea
DOI 10.5012/jkcs.2010.54.01.055
#
마이크로웨이브와CeY Zeolite를이용한니트로화합물의선택적인환원반응
Kapil Arya* and Anshu Dandia†
Department of Applied science, D. C. R. University, Murthal, Sonepat, Haryana, India-131039
†
Department of Chemistry, University of Rajasthan, Jaipur, India-302004
(
접수 2009. 12. 14; 수정 2010. 1. 19; 게재확정2010. 1. 21)
Selective Reduction of Nitro Compounds Using CeY Zeolite Under Microwaves
Kapil Arya* and Anshu Dandia†
Department of Applied science, D. C. R. University, Murthal, Sonepat, Haryana, India-131039
*
E-mail: aryakapil2001@yahoo.com
†
Department of Chemistry, University of Rajasthan, Jaipur, India-302004
(
Received December 14, 2009; Revised January 19, 2010; Accepted January 21, 2010)
요약. 포화 그리고 방향족 니트로화합물은 monomode reactor로 CeY zeolite와 formic acid를 사용하여 반응시키면 아민 치환
체를좋은수율로선택적으로환원된다. 이반응은몇개의민감한작용기를가진화합물에적합하다. 회수한촉매를20회이
상사용후에도 촉매의활성을계속유지하였다.
주제어: CeY zeolite, 마이크로웨이브, 환원, 니트로 화합물
ABSTRACT. Aliphatic and aromatic nitro compounds were selectively reduced to their corresponding amino derivatives in good yields
using formic acid and CeY zeolite under monomode reactor. This system is found to be compatible with several sensitive functionalities.
Beside the recycling result showed it had a long catalyst lifetime and could maintain activity even after being used for 20 cycles.
Keywords: CeY zeolite, Monomode reactor, Microwaves, Reduction, Nitro compounds
1
1-13
INTRODUCTION
compounds,
which are traditionally reduced by high pre-
14
ssure. Though the most general methodology for this con-
15
In recent decade, using an applicable industrial catalyst that
is eco-friendly, green and simply recycled in the reaction
mixtures has been under attention. Thus, green chemistry has
been defined as a set of principles that reduces or eliminates
the use or generation of hazardous substances throughout the
version is catalytic hydrogenation as it is an economical and
effective method, particularly in large scale reactions, the re-
action has a limited utility in the presence of other reducible
16
functional groups. The selective reduction of nitro group in
presence of other reducible functional groups were also achiev-
ed using metal based reduction systems. However, the selec-
tive reduction of the nitro group in presence of carbonyl group
could not easily be attainable under these conditions. In order
to overcome these difficulties, zeolite especially CeY as catal-
ysts meet the requirement for organic transformation taking
into account their environmental advantage.
1
17
entire life of chemical materials. If one compares the tech-
nology with medical care, Green/Sustainable Chemistry (GSC)
focuses on precaution (or prevention) rather than diagnosis and
1
2
cure. Along this line, Zeolites as a catalyst which are nontoxic,
highly acidic and basic nature, high thermal stability and specific
shape selectivity have found more attention.
1
8
Rapid and selective reduction of nitro compounds is of im-
portance for the preparation of amino derivatives in organic
synthesis, particularly when a molecule has other reducible
Therefore we became interested in a possibility of the selec-
tive reduction of nitro groups in presence of other reducible
functional groups including carbonyl groups and halides. Herein,
we report various nitro compounds are selectively and readily
reduced to their corresponding amino derivatives in presence of
other functional groups using zeolites and formic acid under
microwaves.
Now days MW has been employed not only to decrease re-
action times but also to improve yields. MWs constitute a very
original procedure for heating materials, clearly different from
3-7
substituents. Numerous new reagents have been developed
8-10
for the reduction of aromatic nitro compounds, however,
little attention has been paid to the reduction of aliphatic nitro
#
Paper presented in10th International Electronic Conference on
Synthetic Organic Chemistry (ECSOC-10). 1-30 November 2006.
http:/www.mdpi.org/ecsoc-10/e004
-55-

5
6
Kapil Arya and Anshu Dandia
the classical ways. The reduction on reaction times are attri-
buted to be a result of both temperature and pressure effects
and supposed specific effects of the radiation, such as improv-
ed homogeneity in temperature, a faster temperature rise, and
nitro compounds in the presence of other functional groups. The
reaction can easily be applicable to a large scale synthesis of
aniline compounds as the reaction set-up, sequence and work-up
is simple and straightforward. Therefore this procedure does
bear a general use for a large scale preparation of aromatic
amines specifically in cases where selective, rapid, mild reduc-
tion is required.
#
# 19,20
possible modifications of activation parameters ∆H and ∆S .
Several reviews have been published covering various aspects
2
1,22
of microwave-assisted chemistry.
We believe that the time saved by using microwaves is po-
tentially important in traditional organic synthesis but could be
of even greater importance in high-speed combinatorial and
medicinal chemistry as well as industrial scale production of
chemicals. As part of our program aimed at achieving simple
and environmentally compatible synthetic methodologies, we
wish to report a selective, rapid and mild method of reduction
of aliphatic and aromatic nitro compounds to the corresponding
amino derivatives using CeY zeolite and formic acid in aqueous
media under microwave irradiation (Scheme 1). This new
system reduced with ease a wide variety of nitro compounds
directly to the corresponding amines and many functional groups
can be tolerated. When formic acid was replaced by ammonium
formate the reduction proceeded effectively and the products
were obtained in almost comparable yields.
EXPERIMENTAL
All melting points were taken on a Büchi-Tottoli capillary
apparatus and are uncorrected; Microwave dielectric heating
was performed in a Smith Creator single mode microwave cavity
Personal Chemistry from Biotage GmbH, Germany, and pro-
ducing continuous irradiation at 2.45 GHz. The reaction vessel
23
TM
was a round-bottomed 100mm Duran glass tube with a Schott
GL 18 screw cap, provided with Teflon septa as a pressure relief
device. All the products were characterized by comparison of
24
their spectral data and mixed m.p. with the reported ones.
Some of the products such as methylamine, ethylamine and
propylamine, could not be checked by TLC and melting points
2
5
and evaluated by GC. CeY zeolite was prepared by metal
cation exchange on NaY zeolite according to the known method
o
and activated before use by heating at 550 C for 4 hrs.
RESULT AND DISCUSSION
The reduction of nitro group in presence of CeY zeolite and
General procedure
HCOOH or HCOONH
4
was completed within 3 ~ 10 min. TLC
A suspension of an appropriate nitro compounds (5 mmol)
and CeY zeolite (2 mg) were finely ground with a mortar and
pestle. 90% HCOOH (2.5 mL) or ammonium formate (0.5 g)
(2) was added to this mixture in a Pyrex glass vial, which was
placed in a screw capped Teflon vessel. Microwave irradiation
and IR monitored the course of the reaction. All the compounds
reduced (Table 1) by this system were obtained in good yield
(
80 ~ 92%).
As an initial attempt to find out an optimal reaction condition,
o
a variety of experimental procedures were examined for Nitro-
methane and Nitroethane (Table 1, Entry 1 and 2) by changing
reaction medium and conditions (Tables 2). Finally, in order to
check the possible intervention of specific (non-thermal) MW
effects, the results obtained under MW were compared to con-
ventional heating using toluene and DMF as solvent. The re-
action, in the case of Entry 1 and 2, has been carried out using
preheated oil bath, under the same conditions as under MW
was applied for 3 ~ 10 min at 140 C. After the completion of
reaction (TLC analysis), recyclable zeolite was separated by
filtration after eluting the product with ethanol under reduced
pressure and the residue washed with saturated NaCl solution
to remove ammonium formate give pure product in high yield
(Table 2).
Effect of recycling experiment on yield
After the reaction was completed, the reaction mixture was
centrifuged and separated to provide wet solid catalyst in order
to reuse the catalyst and to study the catalyst time and stability.
To each sample, fresh nitro compound (Entry 1, Table 1) and
formic acid was added into same amounts as in the initial re-
action.
(
time, temperature, vessel) (Table 2). Reactions proceeding with
considerable low yields under similar thermal conditions show-
ed there is existence of specific MW effect. The reaction was
also tried with or without using CeY zeolite. No desirable con-
version to the product showed catalytic effect of CeY zeolite.
These results indicate that CeY zeolite catalyzed using formic
acid a versatile reducing system for wide variety of aromatic
Fig. 1 summarizes the experimental results, which indicate
the CeY catalyzed yield of final product was in excess of 90%
every 2 h each time. The CeY catalyst maintained sustained
activity even after being used for 20 cycles and yield was only
slightly decreased.
CeY Zeolite
X-NO2 + HCOOH/HCOONH4
X-NH2
MW, 3 - 10 min, 80 - 90%
1
2
3
From the economic point of view, the cost of the catalyst
Scheme 1
Journal of the Korean Chemical Society

마이크로웨이브와CeY Zeolite를 이용한 니트로화합물의 선택적인 환원반응
57
Table 1. CeY catalyzed reduction of nitro compounds
Reaction time (min)
HCOOH HCOONH
Isolated Yield (%)
Entry
X
Product
4
HCOOH
HCOONH
4
1
2
3
4
5
6
7
8
9
Nitromethane
6
3
Methylamine
85
80
86
83
88
80
90
90
90
91
90
90
90
90
91
89
90
90
90
91
90
90
91
88
90
92
91
90
89
90
78
73
68
75
83
76
88
82
85
87
82
77
83
83
88
86
84
84
88
90
86
88
85
79
81
85
90
83
85
80
Nitroethane
7
7
6
Ethylamine
1-Nitropropane
5
n-Propylamine
1-Nitrobutane
7
5
n-Butylamine
2-Nitroethyl ethanoate
1-Nitromethyl butanoate
Nitrobenzene
7
5
2-Aminoethyl ethanoate
1-Aminomethyl butanoate
Aniline
5
5
7
7
2,3,4-Nitrophenol
5 - 7
10
5 - 7
2,3,4-Aminophenol
2,4-Diaminophenol
2,3,4-Aminotoluene
1,4-Diaminotoluene
2,3-Phenylenediamine
1,2-Naphthylamine
2,4-Aminoanisole
2,4-Dinitrophenol
8
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
2,3,4-Nitrotoluene
1,4-Dinitrobenzene
2,3-Dinitrobenzene
1,2-Nitronaphthalene
2,4-Nitroanisole
7 - 10
10
5 - 9
6
9
7
9
5 - 10
5 - 10
5 - 10
6 - 10
9
8 - 10
2,3,4-Nitroaniline
5 - 10
2,3,4-Phenylenediamine
2,4-Aminobenzaldehyde
2,4-Aminoacetophenone
4-Aminobenzophenone
4-Aminobenzamide
4-Aminophenylacetate
2,3,4-Aminobenzoic acid
2,3,4-Chloroaniline
2,3,4-Bromoaniline
3-Iodoaniline
2,4-Nitrobenzaldehyde
2,4-Nitroacetophenone
4-Nitrobenzophenone
4-Nitrobenzamide
4-Nitrophenylacetate
2,3,4-Nitrobenzoic acid
2,3,4-Nitrochlorobenzene
2,3,4-Nitrobromobenzene
3-Nitroiodobenzene
4-Nitrocinnamic acid
4-Nitrobenzonitrile
4-Nitrophenylacetonitrile
4-Nitrophenethylalcohol
3,5-Dinitrosalicylic acid
4-Nitroacetanilide
4 - 10
6
7
8
9
8
10
5
5 - 8
7 - 9
7 - 9
8
4 - 9
6 - 7
3 - 6
3
9
4
4-Aminocinnamic acid
4-Aminobenzonitrile
4-Aminophenylacetonitrile
4-Aminophenethylalcohol
3,5-Diaminosalicylic acid
4-Aminoacetanilide
10
7
10
8
10
10
7
10
9
5
Table 2. Comparative study of the reduction of nitro compounds (Entry 1 and 2) using CeY zeolite as catalyst
o
a
Entry
1
Reaction Medium
HCOOH
Zeolite
Reaction conditions
Reaction temperature ( C)
Time (min)
Yield (%)
-
MW
MW
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
120
30
30
Nil
Nil
Nil
Nil
85
HCOONH
HCOOH
4
4
4
-
-
Relux
720
720
6
HCOONH
HCOOH
-
Relux
CeY
CeY
CeY
CeY
CeY
CeY
-
MW
HCOONH
HCOOH
MW
3
78
Reflux in Toluene
Reflux in DMF
Reflux in Toluene
Reflux in DMF
MW
240
260
300
310
30
52
HCOOH
45
HCOONH
HCOONH
HCOOH
4
48
4
44
2
Nil
Nil
Nil
Nil
80
HCOONH
HCOOH
4
4
4
-
MW
30
-
Reflux
720
720
7
HCOONH
HCOOH
-
Reflux
CeY
CeY
CeY
CeY
CeY
CeY
MW
HCOONH
HCOOH
MW
6
73
Reflux in Toluene
Reflux in DMF
Reflux in Toluene
Reflux in DMF
260
300
375
400
46
HCOOH
44
HCOONH
HCOONH
4
40
4
38
a
Isolated yield
2010, Vol. 54, No. 1

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Kapil Arya and Anshu Dandia
1
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