Organic Process Research & Development 1999, 3, 101−103
Epoxidation of Terminal Alkenes with Oxygen and 2-Ethyl Hexanal, without
Added Catalyst or Solvent
Christel Lehtinen* and G o¨ sta Brunow
Laboratory of Organic Chemistry, Department of Chemistry, UniVersity of Helsinki, P.O. Box 55,
FIN-00014 UniVersity of Helsinki, Finland
Abstract:
Scheme 1. Epoxidation of alkenes with oxygen aldehyde as
coreactant
Two terminal alkenes, 1-decene and methyl 10-undecenoate,
were epoxidized with oxygen using 2-ethyl hexanal as coreactant
without any added solvent. Under optimal conditions, the yield
of methyl 10,11-epoxyundecanoate was 98.7%. 2-Ethyl hexanal
was oxidized mainly to 2-ethyl hexanoic acid and also formed
some byproducts. The tested metal complexes retarded the
epoxidation reaction slightly and increased the amount of
byproducts of 2-ethyl hexanal.
Table 1. Epoxidation of 1-decene (experiments 1-8) and
methyl 10-undecenoate (experiments 9-12) with procedure
A
epoxide (%)
solvent aldehyde/
reaction
c
expt T (°C)
(mL)
alkene
at 6 h final time (h)
Introduction
1
2
3
4
5
6
7
8
9
0
1
rt
rt
20
20
20
20
10
3/1a
4.9
16.2
47.9
59.3
63
45.4
19.0
42
7.5
24
22
21
24
24
6
8
6
24
24
The epoxidation of alkenes by molecular oxygen in the
presence of a catalyst and aldehyde has been intensively
studied (Scheme 1).1
a
6/1
6.9
21.6
31.9
41.2
21.6
19.0
38.7
38.7
34.0
18.4
a
40
40
40
40
40
60
60
40
40
6/1
6/1
6/1
-15
b
Several research groups have also
b
reported on epoxidation procedures in the absence of
b
6/1
16-19
catalyst.
In both the presence and the absence of catalyst,
b
4.5/1
4.5/1b
the solvent is thought to be essential for the reaction.
Chlorinated or perfluorinated solvents are recommended
because of their capacity to dissolve molecular oxygen.
However, chlorinated solvents constitute a serious envi-
ronmental problem in large-scale production, and perfluor-
inated solvents do not always allow reactions to be performed
in a homogeneous phase. In view of these drawbacks, we
b
4.5/1
38.7
54.6
32.5
b
1
1
10
6/1
6/1
b
a
Aldehyde, 2-methyl propanal. b Aldehyde, 2-ethyl hexanal. c The aldehyde/
alkene ratio is the final ratio of added substances.
set out to test 2-ethyl hexanal as solvent because the oxidation
product of the aldehyde, 2-ethyl hexanoic acid, is itself in
industrial use. In these preliminary experiments, the reaction
proceeded well without additional solvent. A practical
method for preparative isolation of the product is still under
investigation.
*
To whom correspondence should be addressed. E-mail: Christel.Lehtinen@
Helsinki.fi. Fax: +358-9-191 40366. Phone: +358-9-191 40345.
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(
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Results and Discussion
We chose to carry out the air epoxidations on two
representative terminal alkenes, 1-decene and methyl 10-
undecenoate, using 2-ethyl hexanal and 2-methyl propanal
as aldehydes. The influence of solvent and metal complexes
was studied as well as the mode of addition of the reactants
at different temperatures. The results are summarized in
Tables 1 and 2.
We found that, under proper conditions, these terminal
alkenes can be epoxidized in good to excellent yields using
air oxidation with 2-ethyl hexanal as aldehyde, without added
solvent or catalyst. Although terminal alkenes react more
sluggishly in epoxidation reactions than do internal ones, this
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(
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(
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(
(
(
1
0,11-epoxyundecanoate at 98.7%. 2-Ethyl hexanal is less
volatile than the 2-methyl propanal often used in this type
1
0.1021/op980075b CCC: $18.00 © 1999 American Chemical Society and Royal Society of Chemistry
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