Cross-metathesis of vinylsilanes with olefins in the presence of Grubbs' catalyst

Article abstract of DOI:10.1016/S0040-4039(00)02201-2

Effective cross-metathesis of H₂C=C(H)SiR₃, where SiR₃=Si(OMe)₃, Si(OEt)₃, Si(OSiMe₃)₃, with selected olefins in the presence of (PCy₃)₂Cl₂Ru(=CH

Full text of DOI:10.1016/S0040-4039(00)02201-2

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 1175–1178
Cross-metathesis of vinylsilanes with olefins in the presence of
Grubbs’ catalyst
a,b
b
a
a,
Cezary Pietraszuk, Helmut Fischer, Małgorzata Kujawa and Bogdan Marciniec *
a
Faculty of Chemistry, Adam Mickiewicz University, 60-780 Pozna n´ , Poland
b
Fachbereich Chemie, Universit a¨ t Konstanz, Fach M 727, 78457 Konstanz, Germany
Received 18 September 2000; revised 2 November 2000; accepted 29 November 2000
Abstract—Effective cross-metathesis of H CꢀC(H)SiR , where SiR =Si(OMe) , Si(OEt) , Si(OSiMe ) , with selected olefins in the
2
3
3
3
3
3 3
presence of (PCy ) Cl Ru(ꢀCHPh) (I) is described. Treatment of p-substituted styrenes, 1-alkenes and selected allyl derivatives
3
2
2
H CꢀCHCH R% (R%=SiMe , Si(OEt) , Ph, OPh) with an excess of H CꢀC(H)SiR results in the formation of the respective
2
2
3
3
2
3
cross-metathesis products with good yields and selectivities. The metallacarbene mechanism of the process is discussed. © 2001
Elsevier Science Ltd. All rights reserved.
Silyl olefins constitute an important class of compounds
erant ruthenium and molybdenum metathesis catalysts
has opened new opportunities for applying metathesis
in organic synthesis. Important progress has also been
1
widely applied in organic synthesis. Numerous meth-
1
b,c
5
ods for their preparation have been reported.
Cata-
lytic methods include the hydrosilylation of alkynes, the
dehydrogenative silylation of alkenes and the hydro-
made in developing efficient and highly selective cross-
6
metathesis systems.
1c
genation of alkynylsilanes. The catalytic silylation of
olefins by vinylsilanes developed in our group is an
effective and general method for the preparation of
Recently, we reported on the high catalytic activity of
Grubbs’ catalyst in the cross-metathesis of vinylsilanes
2
7
alkenylsilanes. The reaction, which resembles cross-
and vinylsiloxanes with styrene (Scheme 2). High
metathesis, however, proceeds by a non-metallocarbene
yields and selectivities were obtained for vinyltrialkoxy-
and vinyltrisiloxysilanes under very mild conditions
mechanism involving activation of CꢁH and SiꢁCꢀ
3
bonds according to Scheme 1.
(
room temp.).
Scheme 1.
Scheme 2.
Unfortunately, the formation of some amounts of iso-
merization products cannot be avoided when using this
4
method.
In this paper we describe new examples of effective
cross-metathesis of vinyltrialkoxy- and vinyltrisiloxysi-
lanes with aryl-, alkyl-, and allyl-substituted olefins
The development of well-defined, functional group tol-
8
catalyzed by complex I.
*
0
Corresponding author.
The reactions proceeded according to Eq. (1):
040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)02201-2

1
176
C. Pietraszuk et al. / Tetrahedron Letters 42 (2001) 1175–1178
(1)
Table 1. Cross-metathesis of vinylsilanes with selected olefins
H CꢀCHSiR3
Olefin
Conversion of olefin
Yield of (isolated yield of) (E+Z)
R%HCꢀCHSiR3 [%]
E/Z
Yield of R%HCꢀCHR% [%]
2
a
(
vinylsilane) [%]
a
a
a
a
H CꢀCHSi(OEt)3
4-Cl-Styrene
Styrene
4-Me-Styrene
4-OMe-styrene
1-Hexene
72 (100)
68, 95 , (85)
E
E
E
E
9/1
10/1
10/1
10/1
E
15/1
10/1
5/1
Traces
Traces
Traces
Traces
10
8
7
5
Traces
0
Traces
Traces
2
a
a
H CꢀCHSi(OEt)3
70 (100)
67, 95 , (88)
2
b
b
H CꢀCHSi(OEt)3
100
100
100
80
95
2
b
b
H CꢀCHSi(OEt)3
95
2
H CꢀCHSi(OEt)3
75
60
2
H CꢀCHSi(OMe)3
1-Hexene
2
H CꢀCHSi(OSiMe ) 1-Hexene
90
75
100
75
85
72, (67)
60
95, (88)
71
2
3 3
H CꢀCHSi(OEt)3
1-Decene
2
H CꢀCHSi(OEt)3
Allyl-SiMe3
Allyl-Si(OEt)3
Allyl-Ph
2
H CꢀCHSi(OEt)3
2
H CꢀCHSi(OEt)3
68
72
2
H CꢀCHSi(OEt)3
Allyl-OPh
80
2
−
2
Reaction conditions: [(PCy ) Cl Ru(ꢀCHPh)]:[H CꢀCHSiR ]:[olefin]=5×10 :5:1; CH Cl , reflux, 3 h.
3
2
2
2
3
2
2
a
−2
[
Ru]:[H CꢀCHSiR ]:[olefin]=5×10 :1:3.
2 3
b
1
h.
9
The results obtained are summarized in Table 1. Prod-
Compound II then reacts with the olefin H CꢀC(H)R%
2
10
ucts were isolated and characterized spectroscopically.
to give the alkenylidene complex III and ethylene. This
reaction is a part of the commonly accepted metathesis
14
Since vinylsilanes were found to be inactive for the
conversion to self-metathesis products, the vinylsilanes
could be used in excess. Thus, it was possible to mini-
mize the role of competitive olefin self-metathesis.
mechanism. The competitive reaction of II with vinyl-
trialkoxy or vinyltrisiloxysilane leads to an exchange of
methylidene units but does not produce the silylcarbene
7
11
7
complex. By reaction of vinylsilane with III the cross-
Efficient reactions were observed for p-substituted
styrenes, 1-alkenes, phenyl-, phenoxy-, trimethylsilyl-,
and triethoxysilyl-substituted allyl compounds. In con-
12
trast, no reaction was observed for allylamine, allyl-
1
3
methyl thioether and allyl chloride. In earlier studies
these functional groups containing allyl derivatives
were found to deactivate Grubbs’ type carbene com-
plexes. Vinylsilanes containing one or more methyl
substituents at silicon gave only traces or no cross-
metathesis products. Similar results were obtained in
7
the reactions with styrene. Removal of ethylene was
found to be crucial for an increase of reaction
7
efficiency. A high metathesis conversion was achieved
by effective stirring and heating of the reaction mixture
in CH Cl to a gentle reflux. All reactions proceeded
2
2
highly stereoselectively with a strong preference for the
formation of the E isomer. The reactions of vinylsilanes
7
with substituted styrenes as well as with the unsubsti-
tuted styrene and with allyltrimethylsilane even
afforded exclusively (within detection limits) the E
isomer.
7
Based on the results of our earlier study, a metallacar-
bene mechanism for these cross-metathesis reactions is
postulated (Scheme 3).
The benzylidene complex I reacts with vinylsilane to
Scheme 3. Proposed catalytic cycle for the cross-metathesis of
vinylsilanes with olefins.
7
form the methylidene complex II and silylstyrene.

C. Pietraszuk et al. / Tetrahedron Letters 42 (2001) 1175–1178
1177
metathesis product is formed. The relatively high cata-
lyst concentration that has to be used is a consequence
of the instability of the methylidene complex II under
3. Marciniec, B.; Pietraszuk, C. Organometallics 1997, 16,
4320–4326.
4. Foltynowicz, Z. Pol. J. Chem. 1993, 67, 1–7.
5. For recent reviews, see: (a) Ivin, K. J.; Mol, J. C. Olefin
Metathesis and Metathesis Polymerization; Academic:
San Diego, 1997; (b) Alkene Metathesis in Organic Syn-
thesis; F u¨ rstner, A., Ed.; Springer: Berlin, 1998; (c)
Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413–
4450.
6. For recent reviews, see: (a) Gibson, S. E.; Keen, S. P. In
Alkene Metathesis in Organic Synthesis; F u¨ rstner, A.,
Ed.; Springer: Berlin, 1998; pp. 155–181; (b) Blechert, S.
Pure Appl. Chem. 1999, 71, 1393–1399; (c) Roy, R.; Das,
S. K. Chem. Commun. 2000, 519–529.
1
5
the conditions used. A detailed analysis of the reac-
tion mixture indicates that, in addition to cross-
metathesis and olefin metathesis products, also minor
amounts of silylstyrenes—and for the reactions of
vinyltrialkoxysilane—traces of tetraalkoxysilane (alkyl
orthosilicate) are produced. The formation of silylstyre-
nes (Scheme 3) in the reaction of vinylsilanes with I has
7
been described earlier in more detail and confirms the
mechanistic scheme proposed above. Traces of Si(OR)4
found in the reaction mixture are presumably formed
1
6
by catalytic redistribution at silicon. Double-bond
migration (olefin isomerization) was not observed in the
starting olefins or in the cross-metathesis products. This
confirms that, under the conditions used, hydride com-
plexes are not generated in situ. Thus, cross-metathesis
offers the advantage of avoiding olefin isomerization
whereas in most other catalytic systems involving
hydride catalysts isomerization is inevitable. The gener-
ation of RuꢁH complexes in systems containing initially
catalyst I at temperatures ]60°C was reported very
7. Pietraszuk, C.; Marciniec, B.; Fischer, H. Organometallics
2000, 19, 913–917.
8. While this manuscript was under preparation, another
example of effective cross-metathesis of vinyltriethoxysi-
lane with 5-hexen-1-yl acetate was reported, see: Chatter-
jee, A. K.; Morgan, J. P.; Scholl, M.; Grubbs, R. H. J.
Am. Chem. Soc. 2000, 122, 3783–3784.
9. General procedure for the catalytic cross-metathesis
An oven dried flask equipped with a condenser and a
magnetic stirring bar was charged under argon with
CH Cl (5 ml), decane or dodecane (internal standard),
1
7
recently.
2
2
−
3
In conclusion, the efficient and selective cross-metathe-
sis of vinyltrialkoxy- and trisiloxysilanes with p-substi-
tuted styrene-, 1-alkene-, and allyl-derivatives in the
presence of (PCy ) Cl Ru(ꢀCHPh) (I) offers an interest-
vinylsilane (vinylsiloxane) (3.14×10 mol) and the respec-
tive olefin (6.28×10 mol). The reaction mixture was
−
4
stirred and heated in a water bath to maintain a gentle
−
5
reflux. Then ruthenium benzylidene complex I (3.14×10
3
2
2
ing route to unsaturated organosilicon compounds. In
addition, the successful reactions with
mol) was added and the reaction was controlled by GC.
Analyses were made before and 3 hours after the addition
of the complex.
H CꢀC(H)Si(OSiMe) demonstrate the potential of this
2
3
process for modification of poly(vinyl)siloxanes.
Representative procedure for the synthesis of alkenylsilanes
The reaction was carried out as described above with
catalyst, reagents and solvent in ten times greater
amounts. No standard was added. Reaction time: 3 h.
Then solvent was removed under atmospheric pressure.
The product was isolated by vacuum distillation with the
use of an efficient column (yields are included in Table 1).
0. Spectroscopic data of the selected new products:
Acknowledgements
C.P. acknowledges a research grant from the Alexander
von Humboldt Foundation. This work was also sup-
ported by a grant no. T09A 139 19 from the State
Committee for Scientific Research (Poland).
1
1
E-(EtO) SiCHꢀC(H)CH SiMe : H NMR (CDCl , ppm,
3
2
3
3
coupling constants in Hz), l: 0.00 (s, 9 H, SiMe ); 1.21 (t,
3
J=6.9, 9 H, 3×CH ); 1.69 (dd, J=8.0, 1.4, 2 H, CH Si);
3
2
3
.78 (q, J=6.9, 6 H, 3×SiOCH ); 5.19 (dt, J=18.7, 1.4, 1
2
13
H, ꢀCHSi), 6.41 (dt, J=18.7, 8.0 Hz, 1 H, ꢀCH).
NMR (CDCl , ppm) l: −2.02 (SiMe ); 18.21 (CH ); 28.89
C
References
3 3 3
(
CH Si); 58.27 (OCH ); 116.75 (ꢀCHSi); 151.02 (ꢀCH).
2
2
1
. (a) Chan, T. H.; Fleming, I. Synthesis 1979, 761–786; (b)
Colvin, E. W. Silicon Reagents in Organic Synthesis;
Academic: London, 1988; Chapter 3; (c) The Chemistry
of Organosilicon Compounds; Patai, S.; Rappoport, Z.,
Eds.; Wiley: Chichester, 1998.
. (a) Marciniec, B.; Rzejak, L.; Gulinski, J.; Foltynowicz,
Z.; Urbaniak, W. J. Mol. Catal. A: Chem. 1988, 46,
MS, m/z (%): 73 (97), 79 (14), 119 (46), 133 (45), 135 (44),
143 (34), 158 (64), 159 (68), 163 (100), 187 (51), 207 (49),
232 (44), 233 (77), 261 (54), 276 (M , 51); M found=
276.15656, calculated for C H O Si =276.15771.
E-(Me SiO) SiCHꢀC(H)C H : H NMR (CDCl , ppm,
coupling constants in Hz), l: 0.10 (s, 27 H, SiMe ); 0.90
(t, J=6.8, 3 H, CH ); 1.26–1.44 (m, 4 H, 2×CH ); 2.07–
+
+
1
2
28
1
3
2
3
3
4
9
3
2
3
3
2
3
29–340; (b) Foltynowicz, Z.; Marciniec, B. J.
2.14 (m, 2 H, CH ); 5.36 (dt, J=18.4, 1.6, 1 H, ꢀCHSi);
13
2
Organomet. Chem. 1989, 376, 15–20; (c) Foltynowicz, Z.;
Marciniec, B.; Pietraszuk, C. J. Mol. Catal. A: Chem.
6.20 (dt, J=18.4, 6.3, 1 H, ꢀCH). C NMR (CDCl3,
ppm) l: 1.74 (SiMe ); 13.92 (CH ); 22.21 (CH ); 30.62
3
3
2
1
991, 65, 113–125; (d) Marciniec, B.; Pietraszuk, C.;
Foltynowicz, Z. J. Mol. Catal. A: Chem. 1992, 76, 307–
17; (e) Marciniec, B.; Pietraszuk, C. J. Organomet.
(CH ); 36.05 (CH ); 123.79 (ꢀCHSi); 150.24 (ꢀCH). MS,
2
2
m/z (%): 59 (8), 73 (100), 191 (8), 193 (24), 207 (45), 295
+
3
(14), 363 (23), 378 (M , 1).
1
Chem. 1993, 447, 163–166; (f) Marciniec, B.; Pietraszuk,
C.; Foltynowicz, Z. J. Appl. Organomet. Chem. 1993, 7,
E-(EtO) SiCHꢀC(H)C H Cl: H NMR (CDCl , ppm,
3
6
4
3
coupling constants in Hz), l: 1.26 (t, J=6.8, 9 H, CH3);
5
39–541.
3.88 (q, J=6.8, 6 H, CH O); 6.14 (d, J=19.2, 1 H,
2

1
178
C. Pietraszuk et al. / Tetrahedron Letters 42 (2001) 1175–1178
CHSi); 7.35 (d, J=19.2, 1 H, ꢀCH); 7.31–7.39 (m, 4H, 12. Fu, G. C.; Nguyen, S. B.; Grubbs, R. H. J. Am. Chem.
13
ꢀ
C H Cl). C NMR (CDCl , ppm) l: 18.2 (CH ); 58.6
Soc. 1993, 115, 9856–9857.
6
4
3
3
(
CH O); 118.6 (ꢀCHSi); 127.9, 128.7, 134.4, 136.0
13. (a) Armstrong, S. K.; Christie, B. A. Tetrahedron Lett.
1996, 37, 9373–9376; (b) Shon, Y.-S.; Lee, T. R. Tetra-
hedron Lett. 1997, 38, 1283–1286.
2
(C H Cl); 147.6 (ꢀCH). MS, m/z (%): 79 (16), 91 (8),
6
4
1
07 (10), 115 (11), 119 (34), 135 (11), 163 (100), 164
(
11), 179 (2), 181 (1), 195 (1), 225 (2), 255 (0.3), 300
14. For the mechanism of olefin metathesis, see: (a) Heris-
son, J. L.; Chauvin, Y. Makromol. Chem. 1971, 141,
161. The mechanism for ruthenium carbene complexes
is discussed in: (b) Dias, E. L.; Nguyen, S. B.; Grubbs,
R. H. J. Am. Chem. Soc. 1997, 119, 3887–3897.
15. Ulman, M.; Grubbs, R. H. J. Org. Chem. 1999, 64,
7202–7207.
16. Curtis, M. D.; Epstein, P. S. Adv. Organomet. Chem.
1981, 19, 213.
17. Marciniec, B.; Kujawa, M.; Pietraszuk, C. New J.
+
+
(M , 0.2);
M
found=300.09478, calculated for
C H ClO Si=300.09485
14
21
3
1
1. A good yield to selectivity balance was obtained for a
fivefold excess of vinylsilane. Larger excesses such as
0:1 result in a complete elimination of olefin self-
1
metathesis product but also slow down the rate of
cross-metathesis. Different results were obtained for sty-
rene and 4-chlorostyrene for which better yields (with
no drop of selectivity) were obtained for [vinylsi-
lane]:[styrene]=1:3.
Chem. 2000, 24, 671–675.
.