Hydrotalcite catalysis: Heterogeneous epoxidation of olefins using hydrogen peroxide in the presence of nitriles

Article abstract of DOI:10.1039/a707655j

The layered hydrotalcite, Mg₁₀Al₂(OH)₂₄CO₃, acts as an efficient base catalyst for the epoxidation of various olefins using hydrogen peroxide in the presence of benzonitrile and with MeOH as solvent.

Full text of DOI:10.1039/a707655j

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Hydrotalcite catalysis: heterogeneous epoxidation of olefins using hydrogen
peroxide in the presence of nitriles
Shinji Ueno, Kazuya Yamaguchi, Kazushi Yoshida, Kohki Ebitani and Kiyotomi Kaneda*
Department of Chemical Science and Engineering, Graduate School of Engineering Science, Osaka University, 1–3
Machikaneyama, Toyonaka, Osaka 560, Japan
The layered hydrotalcite, Mg10Al
2
(OH)24CO
3
, acts as an
drying the hydrotalcites at 110 °C, they were stored in air and
used without further pretreatment.†
In the presence of Mg10Al (OH)24CO , oxidations of cyclo-
2 3
efficient base catalyst for the epoxidation of various olefins
using hydrogen peroxide in the presence of benzonitrile and
with MeOH as solvent.
hexene using hydrogen peroxide with benzonitrile were carried
out in various solvents such as methanol, benzene, toluene and
1,2-dichloroethane.‡ MeOH gave the highest yield of cyclohex-
ene oxide. However, the oxidation hardly occurred in the
absence of benzonitrile. Table 1 shows the catalytic effect of
various hydrotalcites on the epoxidation of cyclohexene using
benzonitrile in MeOH. Yields of cyclohexene oxide increased
with increasing heat of benzoic acid adsorption on the
hydrotalcites. The basicity of these hydrotalcites was estimated
by a measurement of calorimetric heats of benzoic acid
Hydrotalcites consist of Brucite-like layers having positive
charge with anionic species in the interlayer, forming neutral
materials.1 Combination of different elements, changing the
element ratios in the Brucite-like layer and selection of different
anionic species can tune up the basicity of the hydrotalcites and
,2
3
the interlayer distance. Recently, we found that hydrotalcites
show high catalytic activities for the Baeyer–Villiger oxidation
of various ketones using a combined oxidant of molecular
oxygen and benzaldehyde or MCPBA; the surface hydroxy
groups of the hydrotalcites acted as basic sites to promote the
above oxidations.4 Here, in relation to our studies on the base
catalysis of hydrotalcites, we report that the heterogeneous
epoxidation of various olefins using hydrogen peroxide is
catalysed by hydrotalcites to give the corresponding epoxides
7
adsorption using microdifferential scanning calorimetry. It is
likely that the basic hydroxy groups of the hydrotalcites play an
important role in the epoxidation. Bases such as NaOH and
–7
KOH catalyse the epoxidation of olefins using hydrogen
peroxide in the presence of nitriles.1
4,15
However, NaOH was
not an effective base for our epoxidation.§
[
eqn. (1)].
Table 2 shows results of the oxidation of olefins with
benzonitrile in MeOH. Common linear and cyclic olefins such
as oct-1-ene and cyclohexene gave the corresponding epoxides
as sole products in excellent yield, respectively (entries 1–7).
Norbornene gave only exo-norbornene oxide in quantitative
yield (entry 8). Remarkably, styrene was oxidized to give
styrene oxide in a high yield without formation of other
oxidation products, e.g. acetophenone and benzaldehyde (entry
O
H2O2, PhCN
C
C
C
C
(1)
Mg10Al2(OH)24CO3, MeOH, 60 °C
There are few reports concerning the oxidation of olefins by
hydrotalcite catalysts using hydrogen peroxide.8–11 Shape
selective epoxidation was observed in the case of poly-
oxometalate-intercalated hydrotalcites. But diols and oxolanes
were formed to some degree by successive cleavage of the
epoxides. Notably, our oxidation system using hydrotalcites
exculsively gives epoxides without other products.
9
1
). In the case of an a,b-unsaturated ketone, cyclohex-2-en-
-one, the epoxidation exclusively occurred without formation
of the Baeyer–Villiger oxidation products (entry 10). This
epoxidation proceeds stereospecifically with retention of con-
figuration at the double bonds (entries 2 and 3).
Various hydrotalcites used in Table 1 were prepared by the
Interestingly, we found that adding sodium dodecyl sulfate
and sodium dodecylbenzene sulfate to the above oxidation
system markedly increased the rates of the epoxidation;
cyclooctene oxide was obtained quantitatively within 2 h.¶ This
epoxidation consists of two phases; the olefin and nitrile are in
the organic phase, while the hydrogen peroxide and hydrotalcite
are in the aqueous phase. The above additives might act as a
surfactant to form reverse micelles (aqueous phase in organic
medium), which helps to increase contact area of the interface
between the two phases. The detailed role of the additives in this
epoxidation system is under investigation in our laboratory.
This epoxidation involves the following two steps; (i)
formation of peroxycarboximidic acid by the reaction of a
nitrile with hydrogen peroxide, and (ii) oxygen transfer from
peroxycarboximidic acid to olefin, in which step (i) is promoted
literature procedures.1
talcites are in good agreement with literature values. After
,12,13
Elemental analyses for the hydro-
Table 1 The epoxidation of cyclohexene catalysed by various hydrotalcites
and NaOH using H
a
2 2
O and benzonitrile
Heat of
Adsorption /
c
Conversion Yield
(%)
b
21
Catalyst
(%)
J g
Mg10Al
2
(OH)24CO
3
100
80
69
58
95
20
< 99
79
67
14.0
8.1
6.3
5.1
—
Mg
Mg
Mg
5
6
6
Al(OH)11CO
3
Al
Al
2
2
(OH)16CO
(OH)16SO
3
4
54
53
15
d
e
NaOH
Without catalyst
—
by bases. It is likely that the hydrotalcite acts as a solid base
14
and promotes the formation of peroxycarboximidic acid,
leading to high yields of the epoxides.
a
Reaction conditions: cyclohexene (3.9 mmol), benzonitrile (10.5 mmol),
(2.4 ml), 60 °C, 24 h.
Yields of epoxides were determined by GC analysis using internal
2 2
hydrotalcite (0.05 g), MeOH 10 (ml), 30% aq. H O
In conclusion, we have developed an efficient heterogeneous
catalyst system utilising hydrotalcites for epoxidation and using
a combined oxidant of aqueous hydrogen peroxide and
benzonitrile. The solid hydrotalcites are easily separated from
the reaction mixture via filtration, which makes the work-up
procedure simple. The hydrotalcite can be reused without an
b
standards, based on the olefins. c The basicity of the hydrotalcites was
estimated by calorimetric heats of benzoic acid adsorption. NaOH was
d
equivalent to the amount of hydroxy functions in hydrotalcites (1.5 mmol).
e
Ring opening products of the epoxide, e.g. cyclohexane-1,2-diol and
-methoxycyclohexan-1-ol, were formed.
2
Chem. Commun., 1998
295

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2 2
using H O
and benzonitrilea
Table 2 The epoxidation of various olefins catalysed by Mg10Al
2
(OH)24CO
3
Conversion
(%)
Entry
Substrate
Product
Yield (%)b
O
1
95
95
O
O
2c
100
94
96
93
95
3c
O
4d
100
O
O
5
6
7
100
100
99
>99
94
O
95
O
8
9
100
97
>99
only exo )
(
O
Ph
92
84
Ph
O
O
1
0
1
O
84
90
OH
OH
1
89
O
(
syn : anti = 80 : 20 )
a
b
Reaction conditions: olefin (3.9 mmol), benzonitrile (10.5 mmol), Mg10Al
2 3 2 2
(OH)24CO (0.05 g), MeOH (10 ml), 30% aq. H O (2.4 ml), 60 °C, 24 h.
c
Yields of epoxides were determined by GC analysis using internal standards, based on the olefins. The relative epoxidation rate of cis- and trans-oct-2-ene
d
was 1.5, which is similar to that of MCPBA. 30 °C.
appreciable loss of catalytic activity. This system should prove
useful for many base-catalysed selective oxidations.
1 F. Cavani, F. Trifiro and A. Voccari, Catal. Today, 1991, 11, 173.
2
3
4
K. A. Carrado and A. Kostapapas, Solid State Ionics, 1988, 26, 77.
S. Miyata, Clays. Clay Miner., 1983, 31, 305.
K. Kaneda, S. Ueno and T. Imanaka, J. Chem. Soc., Chem. Commun.,
Notes and References
1
994, 797.
*
†
E-mail: kaneda@cheng.es.osaka-u.ac.jp
A typical procedure for the epoxidation of cyclooctene: Into a reaction
5 K. Kaneda, S. Ueno and T. Imanaka, J. Mol. Catal.,1995, 102, 135.
6 K. Kaneda and T. Yamashita, Tetrahedron Lett., 1996, 37, 4555.
7 S. Ueno, K. Ebitani, A. Ookubo and K. Kaneda, Appl. Surf. Sci., 1997,
121/122, 366.
8 T. Tatsumi, K. Yamamoto, H. Tajima and H. Tominaga, Chem. Lett.,
1992, 815.
9 B. F. Sels, D. E. D. Vos and P. A. Jacob, Tetrahedron Lett., 1996, 37,
8557.
10 C. Cativiela, F. Figueras, J. M. Fraile, J. I. Garc ´ı a and J. A. Mayoral,
Tetrahedron Lett., 1995, 36, 4125 .
11 J. M. Fraile, J. I. Garc ´ı a, J. A. Mayoral and F. Figueras, Tetrahedron
Lett., 1996, 37, 5995 .
12 W. T. Reichle, S. Y. Kang and D. S. Everhordt, J. Catal., 1986, 101,
352.
13 M. A. Drezdson, Inorg. Chem., 1988, 27, 4628.
14 G. B. Payne, P. H. Deming, and P. H. Williams, J. Org. Chem., 1961, 26,
651.
vessel with a reflux condenser were successively placed the hydrotalcite of
Mg10Al (OH)24CO (0.15 g), MeOH (40 ml), cyclooctene (14 mmol),
benzonitrile (17 mmol) and 30% aq. H (7.5 ml). The resulting mixture
was stirred at 60 °C for 24 h. The hydrotalcite was separated by filtration
and the filtrate was treated with MnO (0.03 g) to decompose the remaining
. GC analysis of the filtrate showed a quantitative yield of cyclooctene
oxide. The filtrate was diluted with deionized water (50 ml) and extracted
with CHCl (50 ml 3 3). The extract was concentrated under reduced
pressure and subjected to a silica gel chromatography using a mixture of
n-hexane–Et O (40:1, v/v) as an eluent to give cyclooctene oxide (1.5 g,
7% yield). The isolated hydrotalcite can be reused without loosing its high
catalytic activity.
The order for yields of cyclohexene oxide using different nitrile
compounds is as follows; benzonitrile > acetonitrile > propionitrile.
Under our reaction conditions, use of NaOH in place of the hydrotalcites
resulted in a 53% yield of cyclohexene oxides, as shown in Table 1.
Use of cationic surfactants, e.g. cetylpyridinium chloride monohydrate
2
3
O
2 2
2
2 2
H O
3
2
8
‡
§
15 G. B. Payne, Tetrahedron, 1962, 18, 763.
¶
and tetra-n-propylammonium bromide, did not increase yields of cyclo-
octene oxide.
Received in Cambridge, UK, 23rd October 1997; 7/07655J
296
Chem. Commun., 1998