Ruthenium-catalyzed cross-metathesis between diallylsilanes and electron-deficient olefins

Article abstract of DOI:10.1021/ol0712632

Diallysilanes can be selectively coupled with electron-deficient olefins under cross-metathesis (CM) conditions using the Hoveyda-Grubbs catalyst to produce mono- and/or bis-CM compounds in good yield. The formation of the mono- and the bis-CM compounds depends on the nature of the electron-deficient olefin.

Full text of DOI:10.1021/ol0712632

ORGANIC
LETTERS
2
007
Vol. 9, No. 19
765-3768
Ruthenium-Catalyzed Cross-Metathesis
between Diallylsilanes and
3
Electron-Deficient Olefins
Samir BouzBouz,*,† Lucie Boulard, and Janine Cossy*
Laboratoire de Chimie Organique, ESPCI, CNRS, 10 rue Vauquelin, 75231 Paris
Cedex 05, France
janine.cossy@espci.fr
Received May 29, 2007 (Revised Manuscript Received August 2, 2007)
ABSTRACT
Diallysilanes can be selectively coupled with electron-deficient olefins under cross-metathesis (CM) conditions using the Hoveyda−Grubbs
catalyst to produce mono- and/or bis-CM compounds in good yield. The formation of the mono- and the bis-CM compounds depends on the
nature of the electron-deficient olefin.
During the past decade, olefin metathesis has emerged as a
ω-dienes of type D to generate cyclic olefins of type E.
powerful synthetic tool for the construction of carbon-
carbon double bonds. Recently, it has been demonstrated
Generally, ring-closing metathesis (RCM) is performed under
1
that highly selective cross-coupling can occur between
terminal olefins in the presence of well-defined catalysts such
as [Ru]-I, [Ru]-II, and [Ru]-III (Scheme 1).
Scheme 1. Reaction Conditions and Catalysts for
Ring-Closing Metathesis and Cross-Metathesis
2
3
4
While these catalysts are used to perform selective cross-
coupling reactions (CM) between terminal olefins of type A
5
and B in order to produce olefins of type C, they can also
be used to achieve a ring-closing metathesis (RCM) of
†
Present address: Laboratoire de Chimie Pharmaceutique, UFR M e´ de-
cine et Pharmacie, CNRS, 22 bd, Gambetta, Rouen, France.
(1) For recent reviews, see: (a) Schuster, M.; Blechert, S. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 2067. (b) Grubbs, R. H.; Chang, S. Tetrahedron
1
3
998, 54, 4413. (c) Armstrong, S. K. J. Chem. Soc., Perkin Trans. 1 1998,
71. (d) Phillips, A. J.; Abell, A. D. Aldrichim. Acta 1999, 32, 75. (e)
Blechert, S. Pure Appl. Chem. 1999, 71, 1393. (f) F u¨ rstner, A. Angew.
Chem., Int. Ed. 2000, 39, 3013. (g) Trnka, T. M.; Grubbs, R. H. Acc. Chem.
Res. 2001, 34, 18.(h) Grubbs, R. H. Handbook of Metathesis; Wiley-VCH:
Weinheim, 2003.
(2) (a) Schwab, P.; France, M. B.; Ziller, J. W.; Grubbs, R. H. Angew.
Chem., Int. Ed. Engl. 1995, 34, 2039. (b) Schwab, P.; Grubbs, R. R.; Ziller,
J. W. J. Am. Chem. Soc. 1996, 118, 100.
(3) (a) Huang, J.; Stevens, E. D.; Nolan, S. P.; Petersen, J. L. J. Am.
Chem. Soc. 1999, 121, 2674. (b) Scholl, M.; Trnka, T. M.; Morgan, J. P.;
Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247.
(4) (a) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J., Jr.; Hoveyda,
A. H. J. Am. Chem. Soc. 1999, 121, 791. (b) Garber, S. B.; Kingsbury, J.
S.; Gray, B. L.; Hoveyda, A. H. J. Am. Chem. Soc. 2000, 122, 8168.
(5) For, a recent review on olefin cross-metathesis, see: Connon, S. J.;
Blechert, S. Angew. Chem, Int. Ed. 2003, 42, 1900.
1
0.1021/ol0712632 CCC: $37.00
© 2007 American Chemical Society
Published on Web 08/17/2007

high dilution conditions, typically around 10-2 M, to favor
the intramolecular coupling of the dienes. In contrast, CM
is performed at higher concentration, 0.25 M, to favor the
intermolecular coupling of the two olefins A and B (Scheme
As it has been demonstrated that allylsilanes are good
coupling partners toward electron-deficient olefins under CM
conditions, and since a Si-C bond is longer than a C-C
7
bond (∼1.89 Å vs 1.54 Å), we reasoned that dimethylallyl-
silane 5 would represent a suitable substrate in the CM.
Dimethyldiallylsilane 5 was first examined and treated with
ethyl acrylate in the presence of the catalyst [Ru]-III at a
concentration of 0.25 M in order to preferentially form CM
products. In contrast to the reaction with ω-dienes 1 and 2,
the reaction with diallylsilane 5 afforded the corresponding
product 6 as the major product (53%) together with bis-CM
product 7 (12%) as a mixture of E,E/Z,Z isomers in a ratio
of 5/1. No trace of the cyclized product was observed and
the starting substrate was completely consumed. In order to
optimize the product ratio between 6 and 7 and to improve
the yields of the CM products, the effect the number of
equivalents of ethyl acrylate has on the CM was examined.
Compound 5 was treated with 1.5 equiv, 3.0 equiv, and 6.0
equiv of ethyl acrylate in the presence of 2.5 mol % of [Ru]-
1).
As olefins F and G can be useful synthetic intermediates,
6
2
particularly when X ) SiR , their synthesis was envisaged
by achieving a CM reaction between ω-dienes of type D
and electron-deficient olefins of type B at a concentration
of 0.25 M in order to favor the CM reaction (Scheme 2).
Scheme 2. Cross-Metathesis between Diallylic Compounds
and Electron-Deficient Olefins: Two Possible Outcomes
2 2
III catalyst, in CH Cl , at rt for 12 h (Table 1).
Table 1. Optimization of the CM in between 5 and Ethyl
Acrylate by Varying the Number of Equivalents of Ethyl
Acrylate
Preliminary studies were performed on ω-dienes 1 and 2
2 2
(0.25 M solution in CH Cl ) with electron-deficient olefins
such as acrolein and ethyl acrylate (3 equiv) in the presence
of catalyst [Ru]-III (2.5 mol %), for 12 h. Under these
conditions, and despite the high concentration used, 1 and 2
were transformed to cyclic olefins 3 and 4 in good to
excellent yields (50-94%) and no trace of the expected CM
products was observed (Scheme 3).
Scheme 3. Reaction of 1 and 2 under CM Conditions
When 5 was treated with 1.5 equiv of ethyl acrylate, mono-
CM product (E)-6 was obtained in 60% yield, accompanied
by bis-CM product 7 (12% yield) as a mixture of E,E/E,Z-
isomers in a ratio of 5/1 (Table 1, entry 1). In the presence
of 3 equiv of ethyl acrylate, 5 was transformed to the mono-
CM compounds (E)-6 in 53% yield and the bis-CM
compound was isolated in 16% yield as a mixture of E,E/
E,Z products in a ratio of 5/1 (Table 1, entry 2). Although
an increase in the number of equivalents of ethyl acrylate (6
equiv) leads to overall improvement in conversion to cross-
metathesis products, the ratio of the mono-CM products to
the bis-CM products appears to favor the bis-CM product
These results suggested that these ω-dienes are not suf-
ficiently reactive to undergo CM and have the predisposition
toward cyclization by RCM. To circumvent the RCM, we
decided to examine a class of substrates with a longer C-X
bond length that should thermodynamically render the
cyclization process more difficult and hence favor CM over
7
RCM.
(Table 1).
Dimethyldiallylsilane 5 turned out to be an excellent cross-
(
6) See, for example: (a) Denmark, S.E.; Coe, D. M.; Pratt, N. E.;
coupling partner, and a good selectivity in the mono-CM
product was obtained when the reaction was performed either
with 1.5 or 3 equiv of ethyl acrylate. Having established
Grieder, B. D. J. Org. Chem. 1994, 59, 6161. (b) Lowe, J. T.; Panek, J. S.
Org. Lett. 2005, 7, 1529 and 3231. (c) Hackman, B. M.; Lambardi, P. J.;
Leighton, J. L. Org. Lett. 2004, 6, 4375. (d) Miles, S. M.; Mardsen, S. P.;
Latherbarrow, R.; Coates, W. J. J. Org. Chem. 2004, 69, 6874.
(
7) Kaiser, E. T.; Panar, M.; Westheimer, F. H. J. Am. Chem. Soc. 1963,
5, 602. (b) Perozzi, E. F.; Michalak, R. S.; Figuly, G. D.; Stevenson, W.
H., III; Dess, D. B.; Ross, M. R.; Marin, J. C. J. Org. Chem. 1981, 46,
049.
8
(8) (a) Thibaudeau, S.; Gouverneur, V. Org. Lett. 2003, 5, 4891. (b)
BouzBouz, S.; De Lemos, E.; Cossy, J. AdV. Synth. Catal. 2002, 344, 637.
(c) Crowe, W. E. Goldberg, D. R. J. Am. Chem. Soc. 1995, 117, 5162.
1
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Org. Lett., Vol. 9, No. 19, 2007

optimal reaction conditions, we proceeded to explore other
electron-deficient olefin partners of type B (3 equiv) with
ω-diene 5, in the presence of catalyst [Ru]-III (2.5 mol %)
the bis-CM product 9 (14% yield) (Table 2, entry 2). When
ω-diene 5 was treated with acrylic acid and acrolein, only
the corresponding mono-CM compounds 10 and 11 were
isolated in 44% and 48% yield, respectively (Table 2, entries
3 and 4). It is worth noting that when 5 was reacted with
acrylonitrile, only a trace of the mono-CM product 12 was
2 2
(rt, CH Cl ). In all cases, the isolated major products were
the mono-CM products (Table 2, entries 1-5). Ethyl vinyl
ketone was found to react with 5 to produce mono-CM
product 8 as the major compound (57%), accompanied by
1
detected by H NMR (Table 2, entry 5). Due to the volatility
of mono-CM products 6, 8, and 11, their isolation was
problematic, and to overcome this difficulty, diphenyldial-
lylsilane 13 was used as an alternative substrate for the CM
with electron-deficient olefins.
Table 2. CM between Diallylsilanes and Various
Electron-Deficient Olefins
Diphenyldiallylsilane 13 was treated with ethyl acrylate,
ethyl vinyl ketone, and acrolein as the coupling partners in
the presence of catalyst [Ru]-III (2.5 mol %). When 13 was
reacted with ethyl acrylate, mono-CM product 14 was
isolated in 5% yield and bis-CM product 15 was produced
in 87% yield with a (E,E)/(E,Z) ratio of 40/1 (Table 2, entry
6
). By using ethyl vinyl ketone and acrolein, the mono-CM
products 16 and 17 were the only isolated products in 61%
and 68% yield, respectively (Table 2, entries 7 and 8).
The cross-coupling metathesis between dimethyl-/diphe-
nyldiallylsilanes was selective when ethyl vinyl ketone,
acrylic acid, and acrolein were used, as the mono-CM
compounds were the only isolated compounds. On the
contrary, when ethyl acrylate was employed, the reaction
was not as selective as when the other electron-deficient
olefins were used, and the mono- and/or the bis-CM products
were formed (Table 2, entries 1 and 6).
The methodology can be elaborated to synthesize non-
symmetric bis-CM products from mono-CM compounds.
This was demonstrated when compound 16 was treated with
3
equiv of ethyl acrylate. After 12 h, compound 18 was
isolated in 28% yield and 30% of starting material 16 was
recovered. A better result was obtained when 14 was treated
with ethyl vinyl ketone as the starting material was com-
pletely consumed and the nonsymmetric bis-CM product 18
was isolated in 91% yield, suggesting that compound 14 is
more reactive than compound 16 in the CM process (Scheme
4
).
Scheme 4. Reaction of the Mono-CM Products with
Electron-Deficient Olefins
One of the main consideration for the formation of the
mono-/bis-CM products from ω-dienes is the predisposition
of the starting material to cyclize (Scheme 5).
Org. Lett., Vol. 9, No. 19, 2007
3767

Scheme 5. Possible Reaction Pathways for the Formation of
Scheme 6. CM of 13, 19, and 20 with Ethyl Acrylate
the Mono-CM Product
The mono-CM products can be the result of a direct cross-
metathesis reaction between the diallylsilanes of type H and
an electron-deficient olefin via intermediate I, but we cannot
rule out that a fast RCM reaction may take place to produce
an unsaturated cyclic silane intermediate of type J which
can then undergo a ring-opening metathesis (ROM) to
generate the same intermediate I as five-membered cyclic
7
silane can be opened easily (Scheme 5). In order to verify
if I could be produced from cyclic intermediate J, 19 has to
be synthesized and treated with [Ru]-III catalyst in the
presence of ethyl acrylate (Scheme 6).
a
The ratio of products was determined by GC/MS.
When compound 13 was treated with catalyst [Ru]-III (2.5
2 2
mol %) in CH Cl at rt for 12 h, 19 was not formed, and
produce mono-CM products and/or bis-CM compounds in
good yields and the ratio of the mono-CM and bis-CM
products depends on the nature of the electron-deficient olefin
partners. The mono-CM products of type F and the bis-CM
products of type G are readily accessible from diallylsilanes
and can be useful synthetic intermediates.
In conclusion, and according to these results, it appears
that the cross-metathesis reaction of diallysilanes with
electron-deficient olefins in the presence of Ru-[III], can
produce an intermediate of type I; however, the formation
of intermediate I’ (Scheme 5) cannot be excluded in the
formation of the mono- and bis-CM products.
dimer 20 was obtained in 10% yield (Scheme 6, eq 1). This
result suggests that the mono- and bis-CM products are not
generated through the cyclic intermediate J. Furthermore,
when cyclic olefin 19 [prepared from 13 in the presence of
[
Ru]-II (2.5 mol %) in CH
subjected to the ring-opening metathesis (ROM) with ethyl
acrylate in the presence of [Ru]-III (2.5 mol %) in CH Cl
2 2
Cl for 12 h, 75% yield] was
2
2
at rt for 12 h, the GC/MS analysis of the crude mixture
showed three compounds: mono-CM product 14, bis-CM
compound 15, and starting material 19 in a ratio of 8/26/66
(Scheme 6, eq 2). This result indicates that 19 is not
participating or only has a minor contribution to the
formation of the mono- and the bis-CM compounds (Table
Acknowledgment. Rhodia is gratefully acknowledged for
financial support. L.B. thanks Rhodia and the CNRS for a
grant. We thank Dr. Fisher and Dr. Trimmer from Materia
2, entry 6), thus ruling out a RCM-ROM process in the
synthesis of dienes K. However, we cannot exclude that bis-
CM product 15 comes from dimer 20 as the treatment of
the dimer with ethyl acrylate (3 equiv) and [Ru]-III (2.5 mol
(US) for a generous gift of Hoveyda-Grubbs catalyst.
Supporting Information Available: Experimental pro-
%
) (CH
eq 3).
We have shown that under the cross-metathesis conditions
[Ru]-III, CH Cl , rt, 12 h, c ) 0.25 M), diallylsilanes can
be selectively coupled with electron-deficient olefins to
2 2
Cl , rt, 12 h) produced 15 in 90% yield (Scheme 6,
cedures and characterization data for compounds. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(
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