Cross-metathesis of biosourced fatty acid derivatives: A step further toward improved reactivity

Article abstract of DOI:10.1002/cssc.201403170

The improved catalytic conversion of bioresources, namely unsaturated fatty acid derivatives, is presented. The targeted reaction is ruthenium-catalyzed cross-metathesis with functionalized olefins (α,β-unsaturated esters), that affords shorter diesters. These can be used as biosourced (pre)monomers for the production of polyesters. It is demonstrated that switch from terminal to internal cross-metathesis partners (that is, from methyl acrylate to methyl crotonate) allows use of ppm-level catalyst loadings, while retaining high productivity and selectivity. This was exemplified on a commercial biosourced fatty acid methyl esters mixture, using minimal purification of the substrate, on a 50 g scale. We propose that this improved catalytic behavior is due to the sole presence of more stable alkylidene intermediates, as the notoriously unstable ruthenium methylidene species are not formed using an internal functionalized olefin.

Full text of DOI:10.1002/cssc.201403170

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DOI: 10.1002/cssc.201403170
Cross-Metathesis of Biosourced Fatty Acid Derivatives:
A Step Further Toward Improved Reactivity
Paul Vignon,[a] Tom Vancompernolle,[a] Jean-Luc Couturier,[b] Jean-Luc Dubois,[c]
Andrꢀ Mortreux,[a] and Rꢀgis M. Gauvin*[a]
The improved catalytic conversion of bioresources, namely un-
saturated fatty acid derivatives, is presented. The targeted re-
action is ruthenium-catalyzed cross-metathesis with functional-
ized olefins (a,b-unsaturated esters), that affords shorter die-
sters. These can be used as biosourced (pre)monomers for the
production of polyesters. It is demonstrated that switch from
terminal to internal cross-metathesis partners (that is, from
methyl acrylate to methyl crotonate) allows use of ppm-level
catalyst loadings, while retaining high productivity and selec-
tivity. This was exemplified on a commercial biosourced fatty
acid methyl esters mixture, using minimal purification of the
substrate, on a 50 g scale. We propose that this improved cata-
lytic behavior is due to the sole presence of more stable alkyli-
dene intermediates, as the notoriously unstable ruthenium
methylidene species are not formed using an internal function-
alized olefin.
These combine high activity and selectivity along with toler-
ance toward impurities, a most crucial feature when consider-
ing their use in biomass-derived chemicals, the purity of which
is occasionally problematic. Self-metathesis of FAMEs was
probed very early on,[5] and over the years, much effort was
devoted into their upgrading by cross-metathesis with ethyl-
ene.[6] Following on seminal work,[7] further improvement in
catalytic systems design triggered the use of electron-deficient
cross-metathesis partners such as acrylates or acrylonitrile:
when applied to fatty acid derivatives, this affords an efficient
entry into a,w-bifunctional molecules, such as diesters,[8] ester-
nitrile[9] or ester-amine[10] that have found application as mono-
mers for polyesters or polyamides production.[11]
It was shown by Bruneau’s team that efficient cross-meta-
thesis with such substrates as methyl acrylate (Scheme 1, R=
H) or acrylonitrile implies the use of second generation meta-
thesis catalysts with low catalysts loadings, provided that slow
The use of renewable raw materials by the chemical
industry is nowadays increasingly important, as ex-
emplified by the emerging concept of the biorefi-
nery.[1] Synthetic chemists are pushed towards
a change of paradigm from petroleum- to biomass-
derived chemicals. Thus, triglycerides extracted from
plant oils are a source of fatty acid derivatives, such
as their methyl esters [fatty acid methyl esters
Scheme 1. Cross-metathesis of methyl oleate (1) with terminal and internal functional-
ized olefin.
(FAMEs)].[2] Depending on the selected crop, these
can comprise a given degree of unsaturation, which
provides a handle for chemical transformation and
for their further upgrade into higher value chemicals.[3] Due to
the above-mentioned need for improved biomass transforma-
tion, constant efforts have been devoted to the functionaliza-
tion of the FAME derivatives. In this context, olefin metathesis
plays a key role as a powerful, versatile reaction, mostly thanks
to the spectacular development of ruthenium catalysts.[4]
addition of the catalyst was carried out.[12] With these terminal
olefins as cross-partners, ruthenium-methylidene fragments are
formed during metathesis. Most often, the formation of such
fragments leads to the degradation of the catalyst.[13] It may
thus be of interest to overcome such a problem through the
use of internal olefin derivatives (Scheme 1, R=alkyl). Indeed,
this strategy was successfully followed by Patel and co-workers
for non-functionalized alkenes: switching from ethylene to in-
ternal olefin such as 2-butene has a most beneficial influence
on productivity toward cross-metathesis of biosourced fatty
acid derivatives.[14] In this contribution we will demonstrate
how a switch from terminal to internal electron-deficient olefin
derivatives can afford bifunctionalized products with improved
yields from a biosourced FAMEs mixture.
[a] Dr. P. Vignon, T. Vancompernolle, Prof. A. Mortreux, Dr. R. M. Gauvin
UCCS (CNRS-UMR 8181)
Universitꢀ Lille Nord de France, USTL-ENSCL
59652 Villeneuve d’Ascq (France)
E-mail: regis.gauvin@enscl-lille.fr
[b] Dr. J.-L. Couturier
ARKEMA, Centre de Recherche Rhꢁne Alpes
Pierre Bꢀnite, 69493 cedex (France)
[c] Dr. J.-L. Dubois
Our investigations were initiated on the benchmark methyl
oleate substrate (1), prior to extension to actual biosourced
FAME mixtures. Even though reactant purification was shown
to have a major impact on conversion,[15] we chose to merely
ARKEMA, Direction Recherche et Dꢀveloppement
420, rue Estienne d’Orves, 92705 Colombes (France)
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cssc.201403170.
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degas and percolate 1 over activated alumina to remain close
to industry-relevant conditions.
90% (Table 1, entry 5). However, lower loadings of catalyst lead
to a decrease in both conversion and selectivity, showing the
limits of these catalysts in our conditions (Table 1, entries 7 and
8). Worth mentioning is that 3 ppm of catalyst were able to
achieve a productive turnover number (TON) of approximately
19000, that is into cross-meta-
The cross-metathesis of methyl oleate 1 with an excess of
methyl acrylate (4 equiv) was performed in toluene at 608C
with Umicore catalysts M31 and M51 (Figure 1) to give four
thesis products (entry 8), which
indicates the robustness of this
system. Additionally, we checked
that first generation catalyst M1
does not afford any cross-meta-
thesis products, as reported in
the literature.
To assess the influence of the
Figure 1. Commercially available ruthenium catalysts M1, M31, and M51.
double-bond substitution, we
probed the use of methyl croto-
products as a mixture of E (major) and Z isomers (Scheme 1).
Among these four products, two originate from the cross-
metathesis reaction (CM, 2 and 3, Scheme 1), and two from
self-metathesis (SM) of methyl oleate and of 4-H and 5-H (6
and 7, Scheme 2). As previously reported, vinylidene-terminat-
ed products 4-H and 5-H are not detected.[8]
nate as the cross-metathesis partner. Thus, cross-metathesis of
1 with methyl crotonate in excess (4 equiv) was performed
under the same conditions than previously with catalysts M31
and M51.
In the first place, we observed that switching to an internal
olefin has no detrimental effect on reactivity for both catalysts.
Significant beneficial effects are even obtained for
catalyst M31 on both conversion and selectivity
(Table 2, entries 1–3). About 5 times higher produc-
tive TON is achieved by switching from methyl acry-
late to methyl crotonate using 29 ppm of M31
(Table 2, entry 3). Decreasing the loading to 3 ppm
leads to low conversion of methyl oleate, with poor
selectivity (Table 2, entry 4).
Scheme 2. Self-metathesis of methyl oleate.
M51 is more effective than M31, achieving higher conver-
sion and selectivity (Table 1). Even at a low catalyst loading,
such as 260 ppm (0.026%), M51 afforded almost complete
conversion with selectivity for cross-metathesis products over
Regarding M51, there again, the beneficial effect appears at
low catalyst loading. Higher loadings afford good catalytic per-
formances as observed with methyl acrylate (Table 2, entries 5
and 6). However at 26 ppm loading, a productive TON of more
than 35000 is reached (Table 2, entry 7), which is sig-
nificantly better than with methyl acrylate (TON of
13800 , Table 1, entry 7). Decreasing the loading to
3 ppm again leads to a drop in conversion leading
Table 1. Cross-metathesis between 1 and methyl acrylate.[a]
Entry
Catalyst loading
C[b,c]
[%]
Selectivity [%]
TON
Productive
mainly to self-metathesis products before the occur-
rence of the cross reaction,[9] though this still corre-
sponds to a productive TON of approximately 28300
(Table 2, entry 8). Regarding the underlying mecha-
nistic issues, these results indicate a better tolerance
of the ruthenium ethylidene towards decomposition
in comparison the methylidene derivative, whether
intrinsic to the stability of these species[16] or due to
impurities within the substrates and reagents.
CM[c,d]
SM[c,e]
TON[f]
160
1
2
3
4
5
6
7
8
M31
0.29%
M31
290 ppm
M31
29 ppm
M31
3 ppm
M51
0.26%
M51
260 ppm
M51
26 ppm
M51
74
63
58
11
99
96
69
33
63
37
60
70
87
4
260
40
30
13
96
92
52
15
2170
20000
36600
380
870
6000
4770
365
Having demonstrated the interest of cross-meta-
thesis with an internal functionalized olefin, we
moved on to a biosourced substrate, namely Lubrir-
ob 201.01, provided by Novance. This fatty methyl
esters mixture is composed of saturated compounds
(8.6%), along with methyl linoleate (7.3%) and
methyl oleate as the major unsaturated species
(83.6%). Under metathesis conditions, the last two
substrates will give rise to their respective self- and
cross-metathesis products (See Supporting Informa-
8
3690
3400
13800
19000
48
85
26500
127000
2.6 ppm
[a] Conditions: 0.51 mmol 1, 4 equiv of MA, 608C, 4 h, 2 mL toluene. [b] Conversion of
1. [c] Determined by GC using tetradecane as internal standard. [d] Selectivity in
cross-metathesis products. [e] Selectivity in self-metathesis products. [f] Turnover num-
bers in cross-metathesis products.
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Table 2. Cross-metathesis between 1 and methyl crotonate.[a]
Table 3. Cross-metathesis between Lubrirob and methyl acrylate (MA) or
methyl crotonate (MC).[a]
Entry Catalyst loading C[b,c] Selectivity [%]
TON
Productive
TON[f]
[%]
CM[c,d]
SM[c,e]
Entry Catalyst Partner Conversion Selectivity [%] TON Productive
loading
[%][b,c]
CM[c,d] SM[c,e]
TON[f]
1
2
3
4
5
6
7
8
M31
0.29%
M31
290 ppm
M31
29 ppm
M31
3 ppm
M51
2600 ppm
M51
260 ppm
M51
26 ppm
M51
96
97
3
330
3300
320
1
2
3
4
5
260 ppm MA
26 ppm MA
260 ppm MC
100 ppm MC
26 ppm MC
78
1
94
95
9
59
0
97
96
0
38
100
5
4
100
3000 1770
97
96
26
96
95
96
53
97
97
4
3
3
3200
390
0
3615 3400
9500 9120
33000 31100
3620
0
96
3
88500
420
3470
360
[a] Conditions: 150 mg Lubrirob 201.01, M51 catalyst, 4 equiv methyl ac-
rylate or methyl crotonate, 608C, 4 h, 2 mL toluene. [b] Conversion of
methyl oleate and methyl linoleate. [c] Determined by GC using tetrade-
cane as internal standard [d] Selectivity in cross-metathesis products.
[e] Selectivity in self-metathesis products. [f] Turnover numbers in cross-
metathesis products.
97
99
96
16
1
3640
3600
4
37000 35450
177700 28300
84
3 ppm
to 96% (1 and methyl linoleate), with high selectivity toward
cross-metathesis products (97%). Separation of diester 2 (E
isomer) was achieved by automated chromatography, afford-
ing the compound in 84% isolated yield based on the initial
content in 1 and methyl linoleate. The identity and purity of 2
was checked by GC, GC-MS and NMR (see Supporting Informa-
tion). As a comparison, under identical reaction conditions, the
use of methyl acrylate only afforded a productive TON of
about 1700 for cross-metathesis products compared to 9100
when methyl crotonate was used.
[a] Conditions: 0.51 mmol 1, 4 equiv methyl crotonate, 608C, 4 h, 2 mL
toluene. [b] Conversion of 1. [c] Determined by GC using tetradecane as
internal standard. [d] Selectivity in cross-metathesis (CM) products. [e] Se-
lectivity in self-metathesis (SM) products. [f] Turnover numbers in cross-
metathesis products.
tion for expected metathesis products). However, these will
eventually comprise the same functionalized products 2 and 4-
R, resulting from the =CH(CH2)7CO2Me fragment they hold in
common. To ease analytical issues, methyl linoleate self- and
cross-metathesis products have been identified from dedicated
metathesis reactions (see Supporting Information).
In conclusion, we have shown that cross-metathesis of
methyl oleate with a functionalized olefin can be improved by
a switch from terminal to internal alkene cross-partner. We also
have demonstrated that cross-metathesis of biosourced com-
pounds that have been subjected to minimal purification can
be efficiently carried out with this approach, to achieve a pro-
ductive TON of approximately 9100. Thus, a valuable diester
compound can be accessed with high purity in high yield,
using low catalyst loading and solvent free-conditions, from
a commercial biosourced FAME mixture.
Our study focused on M51 as this is the most efficient cata-
lyst for the considered cross-metathesis reactions. The conver-
sion of Lubrirob indicated thereafter will concern methyl
oleate and methyl linoleate substrates. Self- and cross-meta-
thesis of the other minor unsaturated compounds may occur,
leading to a small amount of several products, which have
only been detected as traces in the reaction mixtures. In the
presence of 4 equivalents of methyl acrylate and using M51 at
a loading of 260 ppm, Lubrirob is as efficiently converted as 1,
with a productive TON of about 1800. However, the use of
lower catalyst loading results in severe conversion and selectiv-
ity drop, which was less obvious with pure methyl oleate
(Table 3, entries 1 and 2). Switching to methyl crotonate for
the cross-metathesis cleavage again proved to be beneficial:
260 ppm of M51 afford excellent conversion and selectivity of
Lubrirob, up to the levels obtained with pure methyl oleate
(Table 3, entry 3). Further decrease in catalyst loading down to
100 ppm is still possible without compromise in catalytic per-
formances, as productive TON reaches about 9100 (Table 3,
entry 4). The use of lower catalyst loading leads to a drastic de-
crease in conversion and selectivity (Table 3, entry 5).
Acknowledgements
The research leading to these results has received funding from
the European Union Seventh Framework Programme (FP7/2007-
2013) under grant agreement n8 241718 EuroBioRef. Umicore is
acknowledged for the gift of catalysts. Novance is thanked for
providing a sample of Lubrirob 201.01. We also thank the CNRS
and the French Ministry of Higher Education for their financial
support.
Keywords: cross-metathesis · fatty acid methyl esters · methyl
crotonate · methyl oleate · ruthenium catalyst
On these grounds, we demonstrated the efficiency of our
approach in a large scale synthesis using 50 g of Lubrirob, with
100 ppm of M51 (11 mg), under similar reaction conditions
(4 equivalents of methyl crotonate, 608C, 4 h). The reaction
was performed in bulk, as avoiding use of solvent is beneficial
in terms of green chemistry. The substrate was converted up
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Published online on && &&, 0000
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P. Vignon, T. Vancompernolle,
J.-L. Couturier, J.-L. Dubois, A. Mortreux,
R. M. Gauvin*
&& – &&
Cross-Metathesis of Biosourced Fatty
Acid Derivatives: A Step Further
Toward Improved Reactivity
Howdy, partner! The use of internal
functionalized olefins as partners in the
cross-metathesis of biosourced fatty
acid methyl esters affords a monomer
for polyester synthesis with high effi-
ciency, despite low catalytic loading and
minimal substrate purification.
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ChemSusChem 0000, 00, 1 – 4
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