New Syntheses with Soybean Oil as Renewable
Feedstock for the Chemical Industry
Jürgen O. Metzger,* Ursula Biermann,* Sandra Fürmeier,* Marcel S.F. Lie
Ken Jie **
* University of Oldenburg, Department of Chemistry, P.O. Box 2503
D-26111 Oldenburg, Germany, e-mail: juergen.metzger@uni-oldenburg.de
** Department of Chemistry, The University of Hong Kong, Pokfulam Road,
Hong Kong, SAR, China
Linoleic acid (1), methyl linoleate (3) and the corresponding epoxy fatty ester (6), which was obtained by transesterification of epoxidized
soybean oil, were functionalized at the C,C-double bonds or by transformation of the epoxy functionality. Here we present the syntheses of
bisepithio derivative 7 and bisaziridine 9 derived from methyl linoleate. The ethylaluminium sesquichloride (Et3Al2Cl3)-induced addition of
formaldehyde to the unsaturated system afforded the ω-hydroxycarboxylic acid 2 with conjugated double bonds, while in the presence of
AlCl3 alkyl substituted 4-chlorotetrahydropyrans 4 and 5 were formed.
Sustainable development had become the key ideal fo the 21th century. In
the search for sustainable chemistry, considerable importance is being
attached to renewable raw materials which exploit the synthetic capabilities
of nature.1 Oils and fats of vegetable and animal origin make up the
greatest proportion of the current consumption of renewable raw materials
in the chemical industry, since they offer to chemistry a large number of
possibilities for applications which can be rarely met by petrochemistry.
During the last few years modern synthetic methods have been applied
extensively to fatty compounds for the selective functionalization of the
C,C-double bond of unsaturated fatty compounds and gave a large
number of novel fatty compounds from which interesting properties are
expected.2 We are reporting here our results on chemical transformations
of soybean oil.
ω-Hydroxycarboxylic acids which are of interest as polyester components
can be synthesized with high selectivity by ene additions of formaldehyde
to unsaturated fatty compounds.2 The Et3Al2Cl3-induced reaction with
linoleic acid (1) afforded the ω-hydroxycarboxylic acid 2 with conjugated
double bonds (Fig.1).
12
9
1
1. (CH2O)n, Et3Al2Cl3, CH2Cl2
2h, r.t.
3
(CH2O)n
AlCl3, CH2Cl2
24 h, r. t.
Cl
O
4
OCH3
12
O
+
Cl
Cl
O
5
OCH3
O
O
+ regioisomers
methyl linoleate : paraformaldehyde : AlCl3 = 2 : 8 : 1
Fig. 2 AlCl3-induded addition of formaldehyde to methyl linoleate.
CH3(CH2)4
OH
9
OCH3
O
O
O
12
6
O
(CH2)7COOCH3
+ anti-diastereomer
racemate
+ NaN3, NH4Cl,
EtOH, H2O
+ P C6H4-P(C6H5)2,
THF
90%
N3
OH
CH3(CH2)4
68%
(CH2)7COOCH3
OH
7
H
N
H
N
8
(CH2)7COOCH3
+ anti-diastereomer
racemate
CH3(CH2)4
2. H2O
N3
+ regioisomers
+ diastereomers
P C6H4-P(C6H5)2 = polymer-bound triphenylphosphine
OH
2
12
10
O
OH
linoleic acid : paraformaldehyde : Et3Al2Cl3 = 1 : 4 :1
Fig.1
Ethylaluminium sequichloride induced ene reaction of linoleic
acid and paraformaldehyde.
Formaldehyde and higher aldehydes react with unsaturated fatty
compounds in the presence of aluminium chloride to form the
corresponding alkylsubstituted 4-chlorotetrahydropyrans. The reaction of
methyl linoleate (3) and four equivalents of formaldehyde yielded a mixture
of the alkylsubstituted mono- 4 and di-4-chlorotetrahydropyran 5 as main
products (Fig.2).
By means of simple industrial reaction, soybean oil is epoxidized. The
epoxidized soybean oil was easily transesterified in the presence of a
heterogeneous basic catalyst (Süd-Chemie) to give epoxidized methyl
linoleate (methyl cis-9,10;cis-12,13-diepoxyoctadecanoate 6).
Epoxidized compounds are reactive substrates for a number of interesting
follow up processes. We synthesized i.e. methyl cis-9,10;cis-12,13diepiminooctadecanoate (8) in two steps starting from 6 via the
corresponding azido alcohol 7 (Fig. 3).3 Compound 8 showed remarkable
cytotoxic, antitumor-promoting and good neuroprotective effects.
Fig. 3 Synthesis of bisaziridine 8 derived from linoleic acid.
The respective methyl cis-9,10;cis-12,13-diepithiooctadecanoate (9) (Fig.4)
was obtained by substitution of the epoxy functionality by treatment of 6
with dimethylthioformamide to give the epithio derivative 9 which is an
interesting intermediate in the synthesis of heterocyclic and highly
functionalized fatty compounds.4
(CH3)2NCSH, CF3COOH
6
63%
S
S
O
OCH3
9
Fig. 4 Synthesis of methyl cis-9,10-cis-12,13-diepithiooctadecanoate
(9).
[1] M. Eissen, J.O. Metzger, E. Schmitt, U. Schneidewind, Angew. Chem. Int. Ed.
2002, 414-436.
[2] U. Biermann, W. Friedt, S. Lang, W. Lühs, G.Machmüller, J.O. Metzger, Mark
Rüsch gen. Klaas, H. Schäfer and M.P. Schneider, Angew. Chem. Int. Ed. 2000,
39, 2206-2224.
[3] J.O. Metzger, S. Fürmeier, Eur. J. Org. Chem. 1999, 661-664.
[4] M.S.F. Lie Ken Jie, Y.F. Zheng, Chem.Phys.Lipids 1988, 49, 167-178.