K5CoW12O40·3H2O: Heterogeneous catalyst for the strecker-type aminative cyanation of aldehydes and ketones

Article abstract of DOI:10.1080/00397910701198914

One-step synthesis of α-aminonitriles was successfully carried out by a three-component condensation of aldehydes or ketones, amines, and potassium cyanide in the presence of a catalytic amount of K5CoW12O40·3H2O as an efficient, reusable, and nontoxic catalyst. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701198914

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K CoW O · 3H O: Heterogeneous Catalyst
5
12 40
2
for the Strecker‐Type Aminative Cyanation of
Aldehydes and Ketones
a b
b
Ezzat Rafiee
& Alireza Azad
a
Faculty of Science, Department of Chemistry , Razi University ,
Kermanshah, Iran
b
Kermanshah Oil Refining Company , Kermanshah, Iran
Published online: 13 Oct 2010.
To cite this article: Ezzat Rafiee & Alireza Azad (2007) K CoW O · 3H O: Heterogeneous Catalyst
5
12 40
2
for the Strecker‐Type Aminative Cyanation of Aldehydes and Ketones, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 37:7, 1127-1132, DOI:
10.1080/00397910701198914
To link to this article: http://dx.doi.org/10.1080/00397910701198914
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Synthetic Communications , 37: 1127–1132, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701198914
.
K CoW O
5
3H O: Heterogeneous
2
12 40
Catalyst for the Strecker-Type Aminative
Cyanation of Aldehydes and Ketones
Ezzat Rafiee
Faculty of Science, Department of Chemistry, Razi University,
and Kermanshah Oil Refining Company, Kermanshah, Iran
Alireza Azad
Kermanshah Oil Refining Company, Kermanshah, Iran
Abstract: One-step synthesis of a-aminonitriles was successfully carried out by a
three-component condensation of aldehydes or ketones, amines, and potassium
.
CoW12O40 3H O as an efficient,
cyanide in the presence of a catalytic amount of K
reusable, and nontoxic catalyst.
5 2
Keywords: a-aminonitriles, polyoxometalates, potassium cyanide, Strecker reactions
Applications of polyoxometalates (POMs) have been demonstrated in
different areas, and some of the most relevant properties for technological
[1]
applications rely on solubility, acidity, and redox potential. Heteropoly
compounds with Keggin structure are the most studied class within
[
POMs, and those containing tungsten as addenda atoms exhibit strong
2]
[3]
acidity, high thermal stability, and low oxidation potential, which allow
[4]
them to be used as catalysts in various reactions at moderate temperatures.
[5]
In continuation of our research on the application of POMs in organic
.
synthesis, herein the applicability of K CoW O
5
3H O as an efficient
2
12 40
Received in Poland June 6, 2006
Address correspondence to Ezzat Rafiee, Faculty of Science, Department of
Chemistry, Razi University, Kermanshah 67149, Iran. E-mail: e.rafiei@razi.ac.ir
1
127

1
128
E. Rafiee and A. Azad
catalyst for the synthesis of a-aminonitriles is reported. There are no examples
of the use of POMs as catalyst for the synthesis of a-aminonitriles in the
literature.
a-Aminonitriles are useful intermediates for the synthesis of amino
[
6]
acids
imidazole derivatives. The synthetic route to a-aminonitriles, known the
and nitrogen-containing heterocycles such as thiadiazoles and
[
7]
Strecker reaction, involves the treatment of an aldehyde or a ketone with
[8]
alkaline cyanides and salts of amines. The reaction is usually carried out
in aqueous solution, and the workup procedure is also tedious. If the usual
solvent used (water) could be changed for typical organic solvents (toluene,
dichloromethane, acetonitrile, etc.), the solubility of the organic reagents as
well as the reaction conditions will be improved. This new protocol
.
[
involves the use of an efficient catalyst, K CoW O
5
3H O, budding
2
9–12]
12 40
many of the catalysts reported in the literature (Scheme 1).
After some experimentation with respect to the molar ratio of reactants
and catalyst, the best results were obtained with a 1:1.1:1.5:0.1 molar ratio
of aldehyde (or ketone), amine, KCN, and catalyst. It seems that acetonitrile
is much better solvent than all others tested (such as dichloromethane, tetra-
hydrofuran, and toluene). It is remarkable to note that no improvements in
the reaction rates and yields were observed by increasing the amount of the
catalyst from 10 mol% to 20 mol%, and lesser amount (5 mol%) also
worked with longer reaction times. A series of aliphatic, heterocyclic, and
aromatic aldehydes carrying either electron-donating or electron-withdraw-
ing substitutions are reacted with aromatic, benzylic, aliphatic (both
primary and secondary) amines, giving a-aminonitriles in high to
excellent yields under these optimum conditions (Table 1). Acid-sensitive
aldehydes such as furfural and cinnamaldehyde worked well without the
formation of any side products (Table 1, entries 11–13). Furthermore,
the reaction conditions are mild enough to perform the reaction in the
presence of enolizable aldehydes such as decanal (Table 1, entry 15). To
our knowledge, only a few reports of Strecker reactions with ketones are
[
9,10]
reported,
but as evidenced in Table 1, entries 17–20, ketones gave
moderate yields in short reaction times. These three-component coupling
reactions proceeded efficiently at ambient temperature with high selectivity.
.
In addition, K CoW O
5
3H O can be reused several times with only a
2
12 40
Scheme 1.

.
K CoW O
5
3H O
2
1129
12 40
.
2
O40 3H O-catalyzed synthesis of a-aminonitriles
Table 1.
K
5
CoW12
Aldehyde/ketone
Benzaldehyde
a
Time (min) Yield (%) Ref.
b
Entry
Amine
1
2
3
4
5
6
7
8
9
Aniline
50
65
80
60
60
40
55
15
60
20
45
50
90
30
95
95
90
86
85
98
91
92
87
88
74
97
80
94
[4g]
[4d]
[4g]
[3b]
[3b]
[3b]
[3b]
[4g]
[4d]
[4g]
[4a]
[4g]
[4g]
[4d]
Benzaldehyde
Benzaldehyde
Benzaldehyde
Benzylamine
Butylamine
Isobutylamine
m-Methoxybenzaldehyde Aniline
m-Methoxybenzaldehyde Benzylamine
m-Methoxybenzaldehyde Butylamine
p-Chlorobenzaldehyde
p-Nitrobenzaldehyde
p-Methylbenzaldehyde
Furfural
Aniline
Aniline
1
1
1
1
1
0
1
2
3
4
Aniline
Aniline
Furfural
Cinamaldehyde
Thiophene-2-
Benzylamine
Aniline
Benzylamine
carboxaldehyde
Decanal
15
16
17
18
19
20
21
Aniline
45
110
30
77
90
51
67
46
[4d]
[3b]
[3b]
[3b]
[3b]
[3b]
[4g]
Benzaldehyde
Cyclohexanone
Cyclohexanone
Morpholine
Benzylamine
Butylamine
140
100
300
50
m-Methyl cyclohexanone Benzylamine
m-Methyl cyclohexanone Morpholine
70
c
80
Benzaldehyde
Aniline
a
Isolated yield.
b
Products were characterized by comparison of their spectroscopic data with those
reported in the literature.
c
After ten successive runs.
slight decrease in the activity, simply by filtering the catalyst, washing with
acetone, and drying (Table 1, entry 21). We believe that because of the pro-
tection of the central cobalt ion with inert oxygen atoms, amines, even those
with strong complexation ability, could not attach the cobalt ion and deac-
tivate it. However, such deactivation has been previously reported for metal
triflate and CeCl as catalysts. In another experiment, when the filtered
3
solution containing the catalyst was used after 6 months of storage, it was
observed that the catalyst was quite active, demonstrating that
.
K CoW O
5
3H O is stable and does not undergo any deterioration.
2
12 40
.
In summary K CoW O
5
3H O can be regarded as an efficient, environ-
2
12 40
mentally friendly, cheap, nontoxic, and reusable catalyst. Also this method is
clean, practical, simple, mild, and applicable to a wide scope of structural
types for synthesis of a-aminonitriles in short reaction times and high to
excellent yields with very easy workup.

1
130
E. Rafiee and A. Azad
EXPERIMENTAL
.
K CoW O
5
3H O was prepared according to the previously reported
2
12 40
5a]
[
procedure. All products were identified by comparison of their physical
and spectroscopic data with authentic samples prepared in according with
[
9]
the procedures in the literature.
General Procedure for the Preparation of a-Aminonitriles
A mixture of aldehyde (1 mmol), amin (1.1 mmol), KCN (1.5 mmol), and
.
K CoW O
5
3H O (0.1 mmol) in acetonitrile (3 mL) was stirred at room
2
12 40
temperature for an appropriate time (Table 1). After completion of the
reaction, as indicated by thin-layer chromatography (TLC), the reaction
mixture was filtered and washed with acetonitrile (2 Â 10 mL). The
combined organic layers were dried over anhydrous Na SO , concentrated
2
4
in vacuum, and purified by column chromatography on silica gel (ethyl
acetate–hexane, 1:9) to afford pure a-aminonitrile.
ACKNOWLEDGMENT
The authors thank the Razi University Research Council and Kermanshah Oil
Refining Company for support of this work.
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