Nickel-catalyzed regio- and stereoselective silylation of terminal alkenes with silacyclobutanes: Facile access to vinylsilanes from alkenes

Article abstract of DOI:10.1021/ja070938t

Treatment of terminal alkenes with silacyclobutanes under nickel catalysis resulted in silylation of the alkenes and yielded the corresponding vinylsilanes in a highly regio- and stereoselective fashion. The reaction provides a facile access to vinylsilan

Full text of DOI:10.1021/ja070938t

Published on Web 04/19/2007
Nickel-Catalyzed Regio- and Stereoselective Silylation of Terminal Alkenes
with Silacyclobutanes: Facile Access to Vinylsilanes from Alkenes
Koji Hirano, Hideki Yorimitsu,* and Koichiro Oshima*
Department of Material Chemistry, Graduate School of Engineering, Kyoto UniVersity, Kyoto-daigaku Katsura,
Nishikyo-ku, Kyoto 615-8510, Japan
Received February 9, 2007; E-mail: oshima@orgrxn.mbox.media.kyoto-u.ac.jp.
Table 1. Silylation with Dimethyl- or Diphenylsilacyclobutanea
Vinylsilanes constitute an important class of compounds in
organosilicon chemistry and in organic synthesis. Transition-metal-
catalyzed hydrosilylation1 and silylmetalation2 are common routes
to vinylsilanes from alkynes. However, the reactions of terminal
alkynes often encounter difficulty in controlling regio- and stereo-
entry
1
R1
3
yield (%), E/Zb
selectivity of the reaction.3 On the other hand, dehydrogenative
silylation of alkenes with hydrosilanes is an attractive alternative
to the reactions mentioned above since vinylsilanes can be
synthesized from alkenes in a highly regio- and stereoselective
fashion. Although iron,4 ruthenium,5 cobalt,6 and rhodium7 com-
plexes are known to catalyze the dehydrogenative silylation of
alkenes with hydrosilanes, the substrates were still limited to
activated alkenes such as R,â-unsaturated esters, styrenes, and 1,5-
dienes. Moreover, the dehydrogenative silylations required a large
excess of alkenes because the alkenes were hydrogen acceptors as
well as substrates to be silylated.
1
2c
1a
1a
1b
1c
1d
1e
1f
1g
1h
1i
CO2CH2Ph
CO2CH2Ph
CO2t-Bu
3a
3a′
3b′
3c
3d
3e
3f
3g
3h
3i
95, >99:1
95, >99:1
95, >99:1
82, 88:12
98, >99:1
99, >99:1
93, >99:1
trace
71, >99:1
93, >99:1
82, >99:1
93, >99:1
81, >99:1
3c
4d,e
5
CONEt2
Ph
6
7
2-MeC6H4
4-MeOC6H4
4-CF3C6H4
2-pyridyl
8
9d
10
11d,f
12d
13d
n-C12H25
1j
1k
1l
CH2SiMe2Ph
(CH2)9OSit-BuMe2
(CH2)9OCOt-Bu
3j
3k
3l
Silacyclobutanes are interesting compounds that have unique
reactivity based on their ring strain and Lewis acidity.8 Therefore,
our group9 and others10 have developed their synthetic utilities.
During the course of our recent studies on the reactivity of
silacyclobutanes under nickel catalysis,11 we have now found nickel-
catalyzed silylation of alkenes with silacyclobutanes. The silylation
provides a new and efficient protocol for regio- and stereoselective
synthesis of (E)-vinylsilanes from a variety of terminal alkenes.
Treatment of benzyl acrylate (1a) and 1,1-dimethylsilacyclobu-
tane (2) in the presence of 5 mol % of Ni(cod)2 and 10 mol % of
P(c-C6H11)3 in toluene at 100 °C provided benzyl (E)-3-(dimeth-
ylpropylsilyl)acrylate (3a) in 95% yield with high regio- and
stereoselectivities (Table 1, entry 1).12 The reaction of 1a with 1,1-
diphenylsilacyclobutane (2′) proceeded without any difficulties to
give 3a′ in 95% yield despite its increased steric hindrance (entry
2). Sterically demanding ester 1b smoothly underwent the silylation
(entry 3). The silylation of R,â-unsaturated amide 1c resulted in
good yield, albeit the product was obtained as a mixture of
stereoisomers (entry 4). Styrene derivatives were converted to the
corresponding silylated products in high yields with high regio-
and stereoselectivity except for electron-deficient 1g (entries 5-8).
A pyridine ring did not prevent the reaction (entry 9). It is worth
noting that simple aliphatic terminal alkenes 1i-l participated in
the reaction (entries 10-13). Moreover, silyl, siloxy, and ester
moieties were tolerated under the reaction conditions.
a A mixture of Ni(cod)2 (0.025 mmol), P(c-C6H11)3 (0.050 mmol), 1 (0.50
mmol), and 2 (0.60 mmol) was heated at 100 °C in toluene (5.1 mL) for 12
h. b Isolated yields. E/Z ratios were determined by 1H NMR. c Silacyclobu-
tane 2′ was used instead of 2. d With 1.0 mmol of 2. e Reaction time was
15 h. f Reaction time was 8 h.
Table 2. Silylation with Benzene-Fused Silacyclobutane 4a
entry
1
R1
5
yield (%), E/Zb
1
1d
1i
1m
1n
Ph
n-C12H25
(E)-(CHdCH)Ph
(E)-(CHdCH)(1-Np)
5d
5i
5m
5n
64, >99:1c,d
80, 70:30c,g
70, 83:17
88, 94:6
2e,f
3
4
a A mixture of Ni(cod)2 (0.025 mmol), PPh3 (0.050 mmol), 1 (0.50
mmol), and 4 (0.60 mmol) was heated at 100 °C in toluene (5.1 mL) for 12
h. b Isolated yields. E/Z ratios were determined by 1H NMR. c 1H NMR
yield. d Dimethyl(2-methylphenyl)[(E)-2-phenylethenyl]silane (6d) was also
obtained in 8% yield. e P(c-C6H11)3 was used instead of PPh3. f With 1.0
mmol of 4. g Dimethyl(2-methylphenyl)[(E)-1-tetradecenyl]silane (6i) was
also obtained in 12% yield.
Notably, the benzene-fused silacyclobutane 4 was also the
suitable silylating agent (Table 2). In the reaction with 4, Ni(cod)2/
2PPh3 catalyst system generally gave the better results. Styrene (1d)
reacted with 4 to furnish the benzyldimethylsilyl-substituted styrene
5d regio- and stereoselectively (entry 1). The palladium-catalyzed
Hiyama cross-coupling reaction of 5d with aryl halides would be
available according to the reported procedures.13 Unfortunately, the
reaction of 1i with 4 furnished the silylated product 5i with moderate
stereoselectivity (entry 2). Conjugated 1,3-dienes also took part in
the reaction. While the silylation of (E)-1-phenyl-1,3-butadiene (1m)
took place to produce the corresponding silane 5m in good yield,
5m comprised an 83:17 mixture of (E) and (Z) isomers (entry 3).
A 1-naphthyl (1-Np) substitution led to the improvement of
stereoselectivity (entry 4). As described above, the dienes obtained
could be further converted to the corresponding asymmetrical 1,4-
diaryl-1,3-dienes under palladium catalysis.13
9
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J. AM. CHEM. SOC. 2007, 129, 6094-6095
10.1021/ja070938t CCC: $37.00 © 2007 American Chemical Society

C O M M U N I C A T I O N S
Scheme 1. Plausible Mechanism
Compounds; Rappoport, Z., Apeloig, Y., Eds.; Wiley: Chichester, 1998;
Vol. 2, Part 2, Chapter 29. (c) Corey, Y. J. In AdVances in Silicon
Chemistry; Larson, G. L., Ed.; JAI: Greenwich, CT, 1991; Vol. 1, p 327-
387. (d) Marciniec, B. ComprehensiVe Handbook on Hydrosilylation;
Pergamon Press: Oxford, 1992. (e) Marciniec, B. In Applied Homogeneous
Catalysis with Organometallic Compounds; Cornils, B., Herrmann, W.
A., Eds.; Wiley-VCH Verlag GmbH: Weinheim, Germany, 2002; Vol.
1, p 491-512.
(2) (a) Fleming, I.; Newton, T. W.; Roessler, F. J. Chem. Soc., Perkin Trans.
1 1981, 2527-2532. (b) Hayami, H.; Sato, M.; Kanemoto, S.; Morizawa,
Y.; Oshima, K.; Nozaki, H. J. Am. Chem. Soc. 1983, 105, 4491-4492.
(c) Okuda, Y.; Wakamatsu, K.; Tu¨ckmantel, W.; Oshima, K.; Nozaki, H.
Tetrahedron Lett. 1985, 26, 4629-4632. (d) Fugami, K.; Hibino, J.;
Nakatsukasa, S.; Matsubara, S.; Oshima, K.; Utimoto, K.; Nozaki, H.
Tetrahedron 1988, 44, 4277-4292. (e) Suginome, M.; Nakamura, H.;
Ito, Y. Chem. Commun. 1996, 2777-2778. (f) Nakamura, S.; Uchiyama,
M.; Ohwada, T. J. Am. Chem. Soc. 2004, 126, 11146-11147.
(3) Recent advances in regio- and stereoselective hydrosilylation of terminal
alkynes. (a) Takeuchi, R.; Nitta, S.; Watanabe, D. J. Org. Chem. 1995,
60, 3045-3051. (b) Kawanami, Y.; Sonoda, Y.; Mori, T.; Yamamoto, K.
Org. Lett. 2002, 4, 2825-2827. (c) Maifeld, S. V.; Tran, M. N.; Lee, D.
Tetrahedron Lett. 2004, 46, 105-108. (d) Sato, A.; Kinoshita, H.;
Shinokubo, H.; Oshima, K. Org. Lett. 2004, 6, 2217-2220. (e) Aneetha,
H.; Wu, W.; Verkade, J. G. Organometallics 2005, 24, 2590-2596.
(4) Kakiuchi, F.; Tanaka, Y.; Chatani, N.; Murai, S. J. Organomet. Chem.
1993, 456, 45-47.
Scheme 2
(5) Seki, Y.; Takeshita, K.; Kawamoto, K.; Murai, S.; Sonoda, N. Angew.
Chem., Int. Ed. Engl. 1980, 19, 928.
(6) Takeshita, K.; Seki, Y.; Kawamoto, K.; Murai, S.; Sonoda, N. J. Org.
Chem. 1987, 52, 4864-4868.
(7) (a) Kakiuchi, F.; Nogami, K.; Chatani, N.; Seki, Y.; Murai, S. Organo-
metallics 1993, 12, 4748-4750. (b) Takeuchi, R.; Yasue, H. Organome-
tallics 1996, 15, 2098-2102.
We are tempted to assume the reaction mechanism for the
silylation of alkenes with silacyclobutanes as follows (Scheme 1).
Initial oxidative addition of silacyclobutanes to zerovalent nickel
species 7 followed by insertion of alkene 1 to the Si-Ni bond of
8 gives the nickelasilacycle 9.14 In the case of the benzene-fused
silacyclobutane 4, the oxidative addition of sp2C-Si bond to Ni-
(0) is preferable to that of the benzylic sp3C-Si bond.15 Subsequent
â-H elimination16 followed by reductive elimination produces 3 or
5 along with the starting zerovalent nickel complex to complete
the catalytic cycle. The result of the silylation of deuterio-1f was
consistent with our plausible mechanism (Scheme 2).
In conclusion, we have found the efficient nickel catalyst system
for silylation of terminal alkenes with silacyclobutanes. The reaction
provides a facile and straightforward access to vinylsilanes from
terminal alkenes in a highly regio- and stereoselective fashion.
Further studies to improve the catalytic turnover and frequency
parameter are currently underway.
(8) Gordon, M. S.; Boatz, J. A.; Walsh, R. J. Phys. Chem. 1989, 93, 1584-
1585.
(9) (a) Matsumoto, K.; Oshima, K.; Utimoto, K. Tetrahedron Lett. 1990, 31,
6055-6058. (b) Matsumoto, K.; Miura, K.; Oshima, K.; Utimoto, K.
Tetrahedron Lett. 1991, 32, 6383-6386. (c) Matsumoto, K.; Miura, K.;
Oshima, K.; Utimoto, K. Tetrahedron Lett. 1992, 33, 7031-7034. (d)
Matsumoto, K.; Yokoo, T.; Oshima, K.; Utimoto, K.; Rahman, N. A. Bull.
Chem. Soc. Jpn. 1994, 67, 1694-1700. (e) Matsumoto, K.; Oshima, K.;
Utimoto, K. J. Org. Chem. 1994, 59, 7152-7155. (f) Okada, K.;
Matsumoto, K.; Oshima, K.; Utimoto, K. Tetrahedron Lett. 1995, 36,
8067-8070.
(10) (a) Sakurai, H.; Imai, T. Chem. Lett. 1975, 891-894. (b) Denmark, S.
E.; Griedel, B. D.; Coe, D. E.; Schnute, M. E. J. Am. Chem. Soc. 1994,
116, 7026-7043. (c) Tanaka, Y.; Yamashita, H.; Tanaka, M. Organo-
metallics 1996, 15, 1524-1526. (d) Bhanu, P. S. C.; Tanaka, Y.;
Yamashita, H.; Tanaka, M. Chem. Commun. 1996, 1865-1866. (e)
Hatanaka, Y.; Watanabe, M.; Onozawa, S.; Tanaka, M.; Sakurai, H. J.
Org. Chem. 1998, 63, 422-423. (f) Tanaka, Y.; Nishigaki, A.; Kimura,
Y.; Yamashita, M. Appl. Organomet. Chem. 2001, 15, 667-670. (g)
Sunderhaus, J. D.; Lam, H.; Dudley, B. Org. Lett. 2003, 5, 4571-4573.
(11) Hirano, K.; Yorimitsu, H.; Oshima, K. Org. Lett. 2006, 8, 483-485.
(12) See Supporting Information for the optimization studies.
(13) (a) Hatanaka, Y.; Hiyama, T. J. Org. Chem. 1989, 54, 268-270. (b) Trost,
B. M.; Machaek, M. R.; Ball, Z. T. Org. Lett. 2003, 5, 1895-1898. (c)
Denmark, S. E.; Tymonko, S. A. J. Am. Chem. Soc. 2005, 127, 8004-
8005.
Acknowledgment. This work was supported by Grants-in-Aid
for Scientific Research from MEXT, Japan. K.H. acknowledges
JSPS for financial support.
(14) Silacyclobutanes were found to undergo oxidative addition to platinum,
palladium, and cobalt complexes. (a) Yamashita, H.; Tanaka, M.; Honda,
K. J. Am. Chem. Soc. 1995, 117, 8873-8874. (b) Tanaka, Y.; Yamashita,
H.; Shimada, S.; Tanaka, M. Organometallics 1997, 16, 3246-3248. (c)
Agenet, N.; Mirebeau, J.-H.; Petit, M.; Thouvenot, R.; Gandon, V.;
Malacria, M.; Aubert, C. Organometallics 2007, 26, 819-830.
(15) The oxidative addition of the benzylic sp3 C-Si bond to Ni(0) would
cause the formations of 6d and 6i (Table 2, entries 1 and 2) (see Supporting
Information for details).
Supporting Information Available: Experimental details, char-
acterization data for new compounds. This material is available free
of charge via the Internet at http://pubs.acs.org.
References
(16) The â-H elimination in a similar seven-membered palladasilacycle was
suggested (see ref 9d).
(1) (a) Hiyama, T.; Kusamoto, T. In ComprehensiVe Organic Synthesis; Trost,
B. M., Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 8, Chapter
3.12. (b) Ojima, I.; Li, Z.; Zhu, J. In The Chemistry of Organosilicon
JA070938T
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