Potassium, fluoride doped on alumina: An efficient catalyst for conversion of aldoximes into nitriles

Article abstract of DOI:10.1081/SCC-200051052

Potassium fluoride loaded on alumina catalyzed the dehydration of alkyl and aryl aldoximes into nitriles in good to high yields.

Full text of DOI:10.1081/SCC-200051052

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Potassium Fluoride Doped on Alumina: An
Efficient Catalyst for Conversion of Aldoximes
Into Nitriles
a
a
Barahman Movassagh & Salman Shokri
a
Department of Chemistry, K. N. Toosi University of Technology, Tehran,
Iran
Published online: 20 Aug 2006.
To cite this article: Barahman Movassagh & Salman Shokri (2005) Potassium Fluoride Doped on Alumina:
An Efficient Catalyst for Conversion of Aldoximes Into Nitriles, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 35:6, 887-890, DOI: 10.1081/SCC-200051052
To link to this article: http://dx.doi.org/10.1081/SCC-200051052
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Synthetic Communications , 35: 887–890, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200051052
Potassium Fluoride Doped on Alumina:
An Efficient Catalyst for Conversion of
Aldoximes Into Nitriles
Barahman Movassagh and Salman Shokri
Department of Chemistry, K. N. Toosi University of Technology,
Tehran, Iran
Abstract: Potassium fluoride loaded on alumina catalyzed the dehydration of alkyl
and aryl aldoximes into nitriles in good to high yields.
2 3
Keywords: Aldoximes, dehydration, KF/Al O , nitriles
INTRODUCTION
The importance of nitriles as useful precursors for the synthesis of amides,
amines, carboxylic acids, and ketones is well established. Furthermore,
nitriles are key constituents in numerous natural products, and they also
serve as intermediates for agricultural chemicals, dyes, pharmaceuticals,
[
1]
and material sciences. Since the manufacture of organic nitriles via the
classical nucleophilic substitution route using highly toxic inorganic
cyanides may prove to be environmentally threatening, the dehydration of
aldoximes with an appropriate dehydrating agent would be an alternative
[
1,2]
approach to nitriles.
been introduced for the dehydration of aldoximes to nitriles.
In the past 40 years, a number of reagents have
[2–9]
In
and
[10]
addition, studies on enzymatic systems, i.e., aldoxime dehydratases
[
11]
cytochrome P450,
and their applications to nitrile synthesis have been
Received in India on November 25, 2004
Address correspondence to Barahman Movassagh, Department of Chemistry, K. N.
Toosi University of Technology, P.O. Box 15875-4416, Tehran, Iran. E-mail:
bmovass1178@yahoo.com

8
88
B. Movassagh and S. Shokri
Scheme 1.
reported. However, the search for simpler but efficient methods continued and
we illustrate the usefulness of potassium fluoride loaded on alumina catalyst
(
denoted as KF/Al O hereafter) for achieving this conversion.
2 3
KF/Al O is a versatile base that has found applications in a large number
2
3
[
12]
of organic reactions.
To our knowledge, no studies are known in literature
exploiting the above system for dehydration of aldoxime to nitrile.
The heterogeneous dehydration reaction involves stirring the aldoxime
with KF (40% by weight)/Al O in dry N,N-dimethylformamide (DMF) at
2
3
858C to afford the corresponding nitriles in good to high yields (Scheme 1).
The method is general and is applicable to alkyl, aralkyl, and aryl
aldoximes. The results of our experiments are compiled in Table 1. The
yield of nitriles are in the range 64–92%. The reaction is highly dependent
on the choice of solvent. For instance, the conversion of benzaldoxime into
benzonitrile (entry 5, Table 1) in toluene (at 808C), acetonitrile (at 808C),
a
2 3
Table 1. Preparation of nitriles from aldoximes with KF/Al O
Reaction
time (h)
b
Entry
R
Yield (%)
1
2
3
4
5
6
7
8
9
4-MeOC
4-MeC
2-MeOC H
6
H
4
4
8
7
90
82
85
87
78
88
92
86
64
81
80
74
83
70
72
6
H
4
11
9
6
4-NH
Ph
3-NO C H
2 6 4
C H
6
8
2
6
4
3-MeC
6
H
4
6
3-BrC
4-CNC H
6
H
4
9
2
6
4
1
1
1
1
1
1
0
1
2
3
4
5
1-Naphthyl
PhCH
CH 55 CH–CH
7
2
12
10
8.5
9
2
2
CH CH CH
3
3
3
2
2
CH
CH
(CH
(CH
2
)
)
3
CH
2
2
7
CH
2
9
a
All prepared nitriles are known in literature and were characterized by comparison
of their physical and spectral data with those of authentic samples.
b
Yield of isolated pure product.

Potassium Fluoride Doped on Alumina
889
THF (at 668C), and MeOH (at 658C) did not take place even after 24 h,
whereas in DMF the reaction is complete at 858C within 6 h.
In conclusion, an efficient alternative to nitrile synthesis from dehydration
of aldoximes, using the KF/Al O system, has been developed that features a
2
3
simple reaction procedure, facile work-up, ready availability of the reagent,
and high yields of the product.
EXPERIMENTAL
Melting points were determined on an Electrothermal 9100 apparatus. IR
1
spectra were obtained using a Shimadzu IR-408 instrument. H-NMR
spectra were recorded on a Jeol JNM-EX90A in CDCl solutions. KF/
3
Al O was prepared as follows: KF (3 g) was dissolved in water (20 mL),
2
3
mixed with neutral chromatographic alumina (4.5 g), and then stirred for
0 min at room temperature. After evaporation of water under reduced
2
pressure, the modified alumina was dried at 1608C for 8 h.
General Procedure for Preparation of Nitriles
A solution of aldoxime (1 mmol) and KF/Al O (7.25 g, 40% by weight) in
2
3
dry DMF (10 mL) was stirred at 858C for the appropriate time (Table 1).
After completion of the reaction, DMF was removed in vacuo, dichloro-
methane (20 mL) was added, and filtered; the filtrate was washed with water
(
2 Â 10 mL) and dried over anhydrous sodium sulfate. The solvent was
evaporated to give the corresponding nitrile, which was purified by prepara-
tive thin layer chromatography (silica gel, eluent petroleum ether : ethyl
acetate ¼ 3 : 1).
ACKNOWLEDGMENT
The financial assistance of the K. N. Toosi University of Technology Research
Council is gratefully acknowledged.
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