First transformation of unsaturated fatty esters involving enyne cross-metathesis

Article abstract of DOI:10.1002/adsc.200800726

The ruthenium-catalysed enyne cross-metathesis of several alkyne derivatives with terminal olefins was performed. These reactions were efficiently achieved under mild conditions in dimethyl carbonate, an eco-friendly solvent. A unique one-pot reaction bas

Full text of DOI:10.1002/adsc.200800726

FULL PAPERS
DOI: 10.1002/adsc.200800726
First Transformation of Unsaturated Fatty Esters Involving Enyne
Cross-Metathesis
Virginie Le Ravalec,a Cꢀdric Fischmeister,a and Christian Bruneaua,*
a
UMR 6226 “Sciences Chimiques de Rennes”, CNRS – Universitꢀ de Rennes 1, Catalyse et Organomꢀtalliques, 263
avenue du gꢀnꢀral Leclerc, bꢁtiment 10 C, 35042 Rennes cedex, France
Fax : (+33)-(0)2-2323-6939; phone: (+33)-(0)2-2323-6283; e-mail: christian.bruneau@univ-rennes1.fr
Received: November 21, 2009; Published online: April 7, 2009
Dedicated to Professor Armin de Meijere on the occasion of his 70th birthday.
Abstract: The ruthenium-catalysed enyne cross- mation of renewable unsaturated fatty esters into
metathesis of several alkyne derivatives with termi- valuable conjugated 1,3-dienes of interest for further
nal olefins was performed. These reactions were effi- transformations.
ciently achieved under mild conditions in dimethyl
carbonate, an eco-friendly solvent. A unique one-pot
reaction based on an ethenolysis step followed by an Keywords: enynes; fatty esters; metathesis; renewa-
enyne cross-metathesis allowed the efficient transfor- ble resources; ruthenium
Introduction
Results and Discussion
With the predicted end of the fossil era, the use of re- Until recently, the transformation of fatty esters by
newable resources as a supply of raw materials for metathesis reactions was essentially performed by
the chemical industry is a domain of intense re- self-metathesis leading to internal olefins or by cross-
search.[1] In this context, vegetable fats and oils have metathesis with ethylene leading to terminal ole-
been envisioned as green alternatives to petrochemi- fins.[7,8] To further extend the potential of metathesis
cal compounds.[2] Olefin metathesis[3] is a very power- for the transformation of fatty esters into end-func-
ful tool in organic[4] and polymer synthesis[5] that has tionalised long-chain alkenes, the direct introduction
already shown a high potential for the transformation of functional groups is strongly desired. Thanks to the
of fats and oils.[6–10] Among the transformations development of very active ruthenium catalysts the
achievable by metathetical processes, enyne metathe- introduction of a polar functionality by cross-metathe-
sis[11] has emerged as a valuable route for the synthe- sis with electron-poor olefins such as acrylates[10a,b]
sis of 1,3-dienes. As for the transformation of olefins, and acrylonitriles[10c,d] is now possible. We now report
intramolecular (ring-closing) and intermolecular the transformation of fatty esters by enyne cross-
(cross-metathesis) versions of enyne metathesis are metathesis leading to conjugated 1,3-dienes that can
possible. The intramolecular transformation was first be further transformed via tandem procedures.[11e,16,17]
reported in 1985 with a tungsten catalyst[12] and then
First the reactivity of methyl oleate 1 with internal
with ruthenium complexes[13] followed in 1997 by the or terminal alkynes potentially leading to four differ-
first examples of enyne cross-metathesis.[14] Since that ent products was examined. Second generation
time, several groups have contributed to the develop- Grubbs’ and Hoveyda catalysts II and IV were tested
ment of these transformations[15] but to the best of for this reaction but none of them allowed any con-
our knowledge, the transformation of fatty esters by version of the alkynes even when terminal alkynes
enyne cross-metathesis has not been reported. were used. (Scheme 1).
Herein, we present the first transformation of fatty
As far as we know there is only one example of
esters by an ethenolysis/enyne cross-metathesis se- enyne cross-metathesis involving cyclooctadiene as an
quence leading to bio-resourced 1,3-dienes.
internal alkene and it was shown that catalyst load-
ings of 5 mol% up to 20 mol% were necessary.[15c,e] In
our case, increasing the loading of IV to 10 mol%
failed to promote the cross-metathesis of 1 with al-
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Scheme 1. Cross-metathesis of methyl oleate 1 with alkynes potentially leading to four dienes [Cy=cyclohexyl; IMes=1,3-
bis-(2,4,6-trimethylphenyl)-2-imidazolinylidene].
Scheme 2. One-pot ethenolysis/cross enyne metathesis.
kynes 2 and 6, and only afforded products resulting
from the self-metathesis of methyl oleate. To over-
come this problem, we turned our attention to the
one-pot ethenolysis/enyne cross-metathesis of methyl
oleate 1 (Scheme 2).
Previous work in our group had shown that com-
plex III was the most efficient catalyst to perform the
ethenolysis of methyl oleate whereas catalysts II and
IV resulted in unworkable mixtures of products due
to a self-metathesis reaction of 1 and to double bond
migration.[8a] Typically, catalyst III (2.5 mol%) al-
lowed the ethenolysis of 1, in dimethyl carbonate
(DMC) used as an eco-friendly solvent,[18] at room
temperature under 1 bar of ethylene leading with
Scheme 3. Enyne cross-metathesis of n-decene with the sym-
metrical alkyne 2
93% conversion to n-decene and methyl 9-decenoate reaction was found to proceed efficiently under mild
without double bond isomerisation and less than 4% conditions using a low catalyst loading and it was also
of self-metathesis products.
shown that catalysts II and IV displayed similar per-
With the first step of the one-pot sequence secured, formances.
Interestingly, reaction monitoring
we focused our efforts towards the optimisation of (Figure 1) showed that the formation of 4 was minor
the enyne cross-metathesis by using n-decene and var- as long as the alkyne was not fully consumed, hence
ious terminal and internal alkynes. To initiate our in- highlighting a favoured enyne cross-metathesis trans-
vestigations, we examined the cross-metathesis of n- formation with regard to an olefin metathesis reac-
decene with alkyne 2 (Scheme 3).
tion. It is also important to note that the reaction
This reaction was initially performed in toluene could be performed with only a two-fold excess of n-
using catalyst II and an excess of alkene. The expect- decene, which contrasts with previous intermolecular
ed formation of 3 was observed along with the forma- enyne metathesis reactions where larger excess of
tion of 4 resulting from the self-metathesis of n- alkene were used.[20]
decene and 5 resulting from the cross-metathesis of 2
The scope of the reaction was extended to other in-
with the in situ generated ethylene.[19] In this metathe- ternal and terminal functional alkynes using the opti-
sis reaction, we have also found that dimethyl carbon- mised experimental conditions. The reactions pro-
ate provided similarly good results as toluene or di- ceeded efficiently for several substrates but different
chloromethane and was selected as the solvent of reactivities were observed with internal and terminal
choice for this project. As summarised in Table 1 the alkynes. Substitution of internal alkynes at the propar-
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Table 1. Enyne cross-metathesis of n-decene with the symmetrical alkyne 2.
Entry Catalyst (mol%) 2 [equiv.] Solvent
Temp. [8C] Time [h] Conv. [%][a] Yield of 3 [%][a] Z/E[a]
1
2
3
4
5
6
II (5)
II (1)
II (1)
II (1)
II (1)
IV (1)
4
2
2
2
2
2
toluene
toluene
CH2Cl2
dimethyl carbonate r.t.
dimethyl carbonate 40
dimethyl carbonate 40
80
40
40
3
100
100
100
100
100
100
98
97
97
97
95
95
0.5/1
0.6
0.6
2.5
0.5
0.6
0.56/1
0.66/1
0.63/1
0.64/1
0.63/1
[a]
Determined by gas chromatography of the crude products.
decenoate=50%). The same one-pot sequence re-
peated with the internal alkyne 2 led to products 3
and 24 (Figure 2) obtained again in high yields, 45%
and 53%, respectively (GC yields).
In both reactions involving terminal or internal al-
kynes, the expected dienes were obtained in a mixture
of several compounds containing unreacted methyl
oleate 1, terminal olefins (n-decene, methyl 9-decen-
AHCTUNGTREGoNNUN ate) and self-metathesis products 4 and 22. Although
these products were present in small quantities and
isolable owing to different polarities and boiling
points, it would be interesting to find alternative
routes for a cleaner production of the desired conju-
gated dienes. An elegant route would be to perform
the one-pot sequence starting from a symmetrical
Figure 1. Reaction profile as product ratio=f(t). Ratios de-
termined by integration vs internal standard.
gylic position totally inhibited the reactions (Table 2, olefin obtained by self-metathesis of methyl oleate[6,7]
entries 1–4) whereas this substitution was found to be or from fermentation of oleic acid.[21] Thus, the diester
necessary for the transformation of terminal alkynes 22 was engaged in a one-pot sequence as previously
(Table 2, entries 5–9). If the lack of reactivity of sub- described for methyl oleate 1 (Scheme 5).
strates 7 and 8 might be attributed to steric hindrance
As shown in Scheme 5, 22 was first transformed by
resulting in the self-metathesis of n-decene only, sub- ethenolysis into methyl 9-decenoate, which was fur-
strates 12 and 13 were found to inhibit any metathesis ther engaged in an enyne cross-metathesis with 9 or 2.
reactions. It is noteworthy that the cross-metathesis Thus, using the bio-resourced fatty diester 22, dienes
with monosubstituted propargylic esters and carbon- 24 and 25 were obtained in high yields and selectivi-
ACHTUNGTRENNUNG
Next, the one-pot ethenolysis/cross-metathesis of consisted in the desired product, the unreacted start-
methyl oleate 1 was performed in dimethyl carbonate ing diester 22 and the intermediate methyl 9-decen-
using the Hoveyda catalyst III for the ethenolysis step
ACHTUNGTRENoNUNG ate as minor products. The dienes 24 and 25 were
and Grubbs catalyst II for the cross-metathesis of the easily purified by column chromatography and isolat-
generated olefins with alkynes. Catalyst II and the ed in 90% and 81% yields, respectively.
alkyne derivative were directly added to the crude re-
action mixture after the ethenolysis was completed
(Scheme 4).
Conclusions
As depicted in Scheme 4 the ethenolysis step fur-
nished n-decene and methyl 9-decenoate in equal pro- In conclusion, we have shown that the enyne cross-
portions and small amounts of self-metathesis prod- metathesis of long-chain terminal olefins resulting
ucts 4 (3%) and 22 (2%). Based on the products ratio from ethenolysis of unsaturated fatty esters could be
measured by gas chromatography, the ethenolysis re- efficiently and selectively performed under mild con-
action furnished 1.7 equiv. of terminal olefins, which ditions in an eco-friendly solvent. The scope of the re-
were reacted with one equiv. of alkyne. This led to action was extended to several internal and terminal
the formation of the desired products 18 and 23 both alkynes bearing functional groups providing an access
in high 48% yield measured by gas chromatography to various functional dienes. This transformation was
with internal calibration (maximum theoretical yield included in a one-pot ethenolysis/enyne cross-meta-
assuming equal reactivity of n-decene and methyl 9- thesis sequence performed from renewable unsaturat-
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Table 2. Cross-metathesis of alkynes with n-decene.[a]
Entry
Alkyne
Product
Conversion/yield[b]
Z/E[c]
1
100/97/94
100/96/70
0.64/1
2
3
0.85/1
–
4
–
5
6
7
8
100/91/80
100/98/79
100/93/70
E>99%[d]
0.34/1
0.4/1[d]
–
–
9
[a]
Catalyst II, (1 mol%), alkyne (0.3 mmol), n-decene (0.6 mmol) dimethyl carbonate (2.5 mL), 408C, 2 h.
Conversion/GC yield/isolated yield (%).
[b]
[c]
[d]
Determined by gas chromatography.
1
Determined by H NMR (isolated product).
ed fatty esters. The expected dienes were formed into functional compounds or intermediates of inter-
starting from methyl oleate together with small est for further transformations.
amounts of internal alkenes resulting from secondary
self metathesis reactions. The use of a symmetrical
diester provides an important advantage as it facili-
tates the purification of the expected dienes. This new
Experimental Section
reaction sequence based on two efficient catalytic
metathesis reactions provides a useful method in
All reactions were carried out under an inert atmosphere of
argon using Schlenck tube techniques. Solvents were freshly
oleochemistry for the transformation of natural oils distilled and dried prior to use according to classical proce-
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First Transformation of Unsaturated Fatty Esters Involving Enyne Cross-Metathesis
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Scheme 4. One-pot ethenolysis/enyne cross-metathesis of methyl oleate 1 with propargyl carbonate 10 (Z/E determined by
GC of the crude products).
Fluka and used as received. Compounds 2 and 12 were pur-
chased from Alfa Aesar and Acros organics, respectively,
and used as received. Compounds 9 and 11 were prepared
according to reported procedures.[22] Sample products were
characterised by NMR analysis using Bruker 200 dpx and
Bruker avance 300 MHz NMR spectrometers. Gas chroma-
tography analyses were performed on a Shimadzu 2014 gas
chromatograph with internal calibration. GC/MS analyses
were performed on a Shimadzu QP2010 apparatus.
Figure 2. Products of the one pot ethenolysis/enyne cross-
metathesis of methyl oleate 1 with the alkyne 2 (Z/E deter-
mined by GC of the crude products).
General Procedure for the Preparation of Propargylic
Compounds
dures; over CaH2 for dichloromethane, Na for THF and tol-
uene. Dimethyl carbonate was purchased from Alfa Aesar
and stored over 4 A molecular sieves after distillation.
Ruthenium catalysts were purchased from Aldrich and
stored under argon. Methyl oleate 1 was purchased from
Ethyl prop-2-yn-1-yl carbonate (13): To a stirred solution of
prop-2-yn-1-ol (2.3 mL, 42.8 mmol, 1.0 equiv.), dimethylami-
nopyridine (30 mg, 0.25 mmol) and triethylamine (9.1 mL,
64.2 mmol, 1.5 equiv.) in CH2Cl2 (60 mL) at 08C was added
Scheme 5. One-pot ethenolysis/enyne cross-metathesis of diester 22 with terminal and internal alkynes (Z/E determined by
1H NMR of the isolated products).
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dropwise ethyl chloroformate[23] (6.1 mL, 64.2 mmol,
1.5 equiv.). The reaction mixture was stirred overnight
(15 h) at room temperature. The reaction mixture was
quenched with saturated NH4Cl and extracted with AcOEt.
The combined extracts were washed with brine and the or-
ganic layer was separated and dried over anhydrous Na2SO4.
The solvent was carefully evaporated (product very volatile)
under vacuum (rotatory evaporator). The residue obtained
was then purified by distillation or chromatographed on
silica gel with pentane/diethyl ether (90:10 v/v) as eluent to
give propargylic carbonate 13 as a colourless oil; yield:
C18H30O4: 310.2144; elemental anal. calcd. for C18H30O4: C
69.64, H 9.74; found: C 69.37, H 9.73.
3-{[(Ethoxycarbonyl)oxy]methyl}-2-methylidenedodec-3-
en-1-yl ethyl carbonate (14): Compound 14 was obtained as
a mixture of isomers. Isomers were identified by analogy to
3. Silica gel purification was found to modify the Z/E ratio.
Z/E: crude (gas chromatography): 0.85/1; purified product
(gas chromatography): 0.34/1, (1H NMR): 0.35/1. Yield:
70%. 1H NMR (300 MHz, CDCl3): d=5.86 (t, J=7.4 Hz,
0.35H), 5.72 (t, J=7.4 Hz, 1.00H), 5.37 (s, 0.95H), 5.32 (s,
0.33H), 5.28 (s, 0.32H), 5.06 (s, 0.98H), 4.87 (s, 0.68H), 4.80
(s, 0.64H), 4.66 (s, 1.90H), 4.63 (s, 1.92H), 4.22–4.14 (m,
4.72H), 2.25 (q, J=7.5 Hz, 0.63H), 2.08 (q, J=7.3 Hz,
1.94H), 1.32–1.25 (m, 22.87H), 0.87 (t, J=7.0 Hz, 4.17H);
13C NMR (75 MHz, CDCl3): d=155.1, 155.0, 139.8, 135.9,
132.8, 118.0, 115.5, 77.4, 71.0, 68.9, 64.3, 64.2, 64.1, 63.0, 32.0,
29.7, 29.6, 29.4, 29.3, 28.9, 22.8, 14.4, 14.3; HR-MS: m/z=
190.1724 [MÀ2C3H6O3]+, calcd. for C20H34O6: 370.2355; ele-
mental anal. calcd. for C20H34O6: C 64.84, H 9.25; found: C
64.60, H 9.21.
2-Methylene-1-phenyldodec-3-en-1-yl acetate (17): Prod-
uct 17 was obtained as the single E isomer. 1H NMR
(300 MHz, CDCl3): <it>d</it>=7.38–7.27 (m, 5H), 6.52
(s, 1H), 5.98 (d, J=16.2 Hz, 1H), 5.68 (dt, J=6.7 Hz, J=
16.1 Hz, 1H), 5.21 (s, 1H), 5.18 (s, 1H), 2.11 (s, 3H), 1.99
(q, J=6.8 Hz, 2H), 1.31–1.22 (m, 12H), 0.88 (t, J=6.9 Hz,
3H); 13C NMR (75 MHz, CDCl3): <it>d</it>=170.1,
144.3, 138.8, 133.2, 128.6, 128.5, 128.3 127.8, 114.2, 100.13,
77.4, 75.1, 33.2, 32.0, 29.6, 29.4, 29.2, 29.1, 22.8, 21.4, 14.3;
HR-MS: m/z=337.2140 [M+Na]+, calcd. for C21H30O2:
314.2246; elemental anal. cal. for C17H30O3: C 80.21, H 9.62;
found: C 80.34, H 9.55.
1
5.26 g (96%). H NMR (300 MHz, CDCl3): d=4.68 (d, J=
2.5 Hz, 2H), 4.19 (q, J=7.1 Hz, 2H), 2.50 (t, J=2.5 Hz,
1H), 1.28 (t, J=7.1 Hz, 3H); 13C NMR (75 MHz, CDCl3)
d=154.6, 77.16, 75.6, 64.6, 55.1, 14.3.
But-2-yne-1,4-diyl diethyl biscarbonate (6): Yield: 93%.
1H NMR (300 MHz, CDCl3): d=4.76 (s, 4H), 4.22 (q, J=
7.0 Hz, 4H), 1.31 (t, J=7.0 Hz, 6H); 13C NMR (75 MHz,
CDCl3): d=154.6, 81.0, 64.7, 55.3, 14.3.
Diethyl hex-3-yne-2,5-diyl diacetate (7): Yield: 76%;
1H NMR (300 MHz, CDCl3): d=5.47 (q, J=6.6 Hz, 2H),
2.06 (s, 6H), 1.47 (d, J=6.6 Hz, 6H); 13C NMR (75 MHz,
CDCl3): d=169.8, 83.1, 60.2, 21.4, 21.2.
Diethyl hex-3-yne-2,5-diyl biscarbonate (8): Yield: 90%;
1H NMR (300 MHz, CDCl3): d=5.35 (q, J=6.6 Hz, 2H),
4.21 (q, J=7.1 Hz, 4H), 1.52 (d, J=6.6 Hz, 6H), 1.31 (t, J=
7.1, 6H); 13C NMR (75 MHz, CDCl3): d=154.2, 83.4, 64.4,
64.0, 21.4, 14.4.
Ethyl 1-methylprop-2-yn-1-yl carbonate (10): Yield: 93%;
1H NMR (300 MHz, CDCl3): d=5.29 (q, J=6.6 Hz, 1H),
4.21 (q, J=7.1 Hz, 2H), 2.49 (s, 1H), 1.55 (d, J=6.6 Hz,
3H), 1.31 (t, J=6.6 Hz, 3H); 13C NMR (75 MHz, CDCl3)
154.3, 81.6, 73.8, 64.4, 63.9, 21.4, 14.3.
Ethyl-2-methylene-1-methyldodec-3-en-1-yl
carbonate
(18): Product 18 was obtained as a mixture of isomers. Silica
gel purification was found to modify the Z/E ratio. Z/E
crude (gas chromatography): 0.34/1; purified product (gas
chromatography): 0.52/1, (1H NMR): 0.55/1. Yield: 79%.
1H NMR (300 MHz, CDCl3): d=6.01 (d, J=16.1 Hz,
1.00H), 5.84–5.75 (m, 1.55H), 5.64 (dt, J=7.1 Hz, J=
11.7 Hz, 0.61H), 5.40 (q, J=6.5 Hz, 0.98H), 5.27 (s, 0.59H),
5.19–5.12 (m, 1.52H), 5.04 (s, 0.94H), 4.99 (s, 0.57H), 4.22–
4.15 (m, 2.91H), 2.19 (q, J=7.2 Hz, 1.15H), 2.09 (q, J=
7.0 Hz, 1.88H), 1.45–1.26 (m, 28.57H), 0.88 (t, J=6.9 Hz,
5.14H); 13C NMR (75 MHz, CDCl3): d=154.7, 146.2, 135.7,
132.0, 128.6, 125.2, 114.0, 112.3, 77.0, 74.0, 64.0, 63.9, 33.3,
32.0, 30.1, 29.7, 29.6, 29.5, 29.4, 29.3, 28.9, 22.8, 20.7, 19.9,
14.4, 14.3; HR-MS: m/z=192.1890 [MÀC3H6O3]+, calculat-
ed for C17H30O3: 282.2195; elemental anal. calcd. for
C17H30O3: C 72.30, H 10.71; found: C 72.43, H 10.78.
General Procedure for the Preparation of New 1,3-
Diene Compounds
3-[(Acetyloxy)methyl]-2-methylenedodec-3-en-1-yl acetate
(3): A dried Schlenk tube was loaded with 2.5 mg of II
(0.003 mmol, 1 mol%), 50 mg of 2 (0.295 mmol, 1.0 equiv.)
and 2.5 mL of dimethyl carbonate. 110 mL of 1-decene
(0.590 mmol, 2.0 equiv.) and 26 mL of hexadecane (internal
standard) were then introduced into the stirred solution.
The reaction mixture was heated at 408C for a period of
40 min (until all 1,4-diacetoxy but-2-yne was consumed).
The solvent was evaporated under vacuum to give a dark
coloured oil. This oil was then purified by chromatography
on silica gel with diethyl ether/petroleum ether (98:2 v/v) as
the eluant to give 3 as a colorless oil; yield: 86.5 mg (94%).
Compound 3 was obtained as a mixture of isomers. Isomers
were identified by NOESY experiments. Silica gel purifica-
tion was found to modify the Z/E ratio. Z/E crude (gas
chromatography): 0.64/1; purified product (gas chromatogra-
Ethyl-2-methylene-1-phenyldodec-3-en-1-yl
carbonate
(19): Product 19 was obtained as a mixture of isomers. Z/E
crude (1H NMR): 0.4/1; purified product (1H NMR): 0.43/1.
1
Yield: 70%. H NMR (300 MHz, CDCl3): d=7.42–7.28 (m,
1
phy): 0.25/1, (1H NMR): 0.26/1. H NMR (300 MHz, CDCl3):
6.89H), 6.34 (s, 1.00H), 6.05 (s, 0.38H), 5.98 (d, J=16.0 Hz,
1.02H), 5.76–5.66 (m, 1.44H), 5.55 (dt, J=7.1 Hz, J=
11.6 Hz, 0.44H), 5.45 (s, 0.41H), 5.27 (s, 1.05H), 5.25 (s,
1.04H), 5.13 (s, 0.40H), 4.25–4.17 (m, 2.85), 2.14 (q, J=
6.6 Hz, 0.81H), 2.02 (q, J=6.9 Hz, 2.05H), 1.36–1.24 (m,
22.57H), 0.91 (t, J=6.9 Hz, 4.41H); 13C NMR (75 MHz,
CDCl3): d=154.6, 143.9, 143.0, 138.2, 135.9, 133.2, 128.6,
128.5, 128.4, 128.3, 127.7, 127.3, 125.3, 114.9, 114.2, 100.1,
81.5, 78.9, 64.3, 33.2, 32.0, 29.9, 29.6, 29.5, 29.4, 29.3, 29.2,
d=5.82 (t, J=7.5 Hz, 0.26H), 5.66 (t, J=7.4 Hz, 1.00H),
5.31 (s, 1.01H), 5.25 (s, 0.23H), 5.22 (s, 0.23H), 5.00 (s,
1.00H), 4.81 (s, 0.45H), 4.75 (s, 0.45H), 4.60 (s, 1.93H), 4.57
(s, 1.93H), 1.26 (m, 0.41H), 2.11–2.04 (m, 8.72H), 1.33–1.25
(m, 14.75H), 0.87 (t, J=6.9 Hz, 3.87H); 13C NMR (75 MHz,
CDCl3): d=170.8, 170.6, 140.6, 134.8, 133.5, 117.2, 68.0, 65.9,
32.0, 29.8, 29.6, 29.5, 29.4, 28.9, 22.8, 21.1, 21.0, 14.3; HR-
MS: m/z=190.1722 [MÀ2CH3COOH]+, calcd. for
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First Transformation of Unsaturated Fatty Esters Involving Enyne Cross-Metathesis
FULL PAPERS
29.1, 28.9, 22.8, 14.4, 14.3; HR-MS: m/z=344.2380 [M]+,
calcd. for C22H32O3: 344.2351; elemental anal. calcd. for
C22H32O3: C 76.70, H 9.36; found: C 76.24, H 9.38.
Methyl-10,11-bis[(acetyloxy)methyl]dodeca-9,11-dienoate
(24): A Schlenk flask (100 mL capacity) was loaded with
4.4 mg of catalyst III (0.007 mmol, 2.5 mol%), 0.110 g of die-
ster 22, 26 mL of hexadecane (internal standard) and 2.5 mL
of dimethylcarbonate. The solution was stirred for 3 h at
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room temperature before addition of 50 mg of
2
(0.295 mmol, 1.0 equiv.) and 2.5 mg of catalyst II
(0.003 mmol, 1 mol%). The reaction mixture was then
heated at 408C for a period of 30–40 min (until all 1,4-diace-
toxybut-2-yne was consumed). After cooling to to room
temperature and solvent evaporation the dark crude oil was
purified by chromatography on silica gel with diethyl ether/
petroleum ether (95:5 v/v) as the eluant to give 24 as a clear
oil; yield: 94.5 mg (90%). Product 24 was obtained as a mix-
ture of isomers. Silica gel purification was found to modify
the Z/E ratio. Z/E crude (gas chromatography): 0.95/1; puri-
1
fied product, (1H NMR): 0.6/1. H NMR (300 MHz, CDCl3):
d=5.81 (t, J=7.5 Hz, 0.60H), 5.65 (t, J=7.3 Hz, 1.00H),
5.31 (s, 1.04H), 5.25 (s, 0.56H), 5.22 (s, 0.57H), 4.99 (s,
1.02H), 4.80 (s, 1.14H), 4.75 (s, 1.11H), 4.60 (s, 1.95H), 4.57
(s, 1.98H), 3.66 (s, 4.58H), 2.32–2.18 (m, 3.17H), 2.08–2.04
(m, 12.24H), 1.63–1.58 (m, 3.30H), 1.29 (m, 9.78H);
13C NMR (75 MHz, CDCl3): d=174.4, 170.8, 170.6, 141.4,
140.6, 139.6, 135.4, 134.6, 133.6, 131.7, 117.1, 114.64, 77.4,
67.9, 65.9, 65.4, 59.9, 51.6, 34.2, 29.7, 29.6, 29.2, 28.9, 28.5,
25.1, 21.1, 21.0; HR-MS: m/z=377.1938 [M+Na]+, calcd.
for C19H30O6: m/z=354.2042; elemental anal. calcd. for
C19H30O6: C 64.39, H 8.53; found: C 64.46, H 8.69.
Ethyl
11-[(acetyloxy)ACTHNGUTERNNU(G phenyl)methyl]dodeca-9,11-dien-
oate (25): Product 25 was obtained as a mixture of isomers.
Z/E determined by 1H NMR (pure product): 0.2/1. Yield:
1
81%. H NMR (300 MHz, CDCl3): d=7.39–7.28 (m, 6.06H),
6.51 (s, 1.00H), 6.22 (s, 0.20H), 5.97 (d, J=16.1 Hz, 1.02H),
5.67 (dt, J=6.9 Hz, J=16.0 Hz, 1.24H), 5.51 (dt, J=7.0 Hz,
J=11.6 Hz, 0.23H), 5.37 (s, 0.24H), 5.21 (s, 1.02H), 5.18 (s,
1.02H), 5.08 (s, 0.21H), 3.66 (s, 3.73H), 2.31–2.269 (m,
2.52H), 2.12–2.11 (m, 4.06H), 1.99 (q, J=7.0 Hz, 2.05H),
1.61–1.56 (m, 2.55H), 1.30–1.16 (m, 10.02H); 13C NMR
(75 MHz, CDCl3): d=174.4, 170.0, 144.2, 138.7, 133.0, 128.7,
128.5, 128.4, 128.3, 127.8, 127.3, 114.2, 100.1, 75.1, 51.6, 34.2,
33.1, 29.2, 29.1, 28.9, 25.0, 21.4; HR-MS: m/z=381.2037
[M+Na]+, calcd. for C22H30O4: 358.2144; elemental anal.
calcd. for C22H30O4: C 73.71, H 8.44; found: C 73.54, H 8.49.
Acknowledgements
The authors are grateful to the CNRS and to the Rꢀgion Bre-
tagne for a PhD grant to VLR, and wish to thank the Euro-
pean Commission (NoE IDECAT, NMP3-CT-2005-011730)
for support.
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Adv. Synth. Catal. 2009, 351, 1115 – 1122