[Bis(2-pyridyldimethylsilyl)methyl]lithium

[356062-49-2]  · C15H21LiN2Si2  · (MW 292.45)

(reagent used for the preparation of vinylsilanes from carbonyl compounds)

Solubility: soluble in diethyl ether.

Form Supplied in: prepared in situ and used directly.

Analysis of Reagent Purity: NMR.

Preparative Methods: deprotonation of bis(2-pyridyldimethylsilyl)methane by n-butyllithium in dry Et2O at -78 °C under argon.

Handling, Storage, and Precautions: sensitive to air and moisture.

Introduction

The Peterson-type olefination reaction has emerged as an extremely useful method for the preparation of alkenes from carbonyl compounds.1,2 Synthetically useful vinylsilanes can be prepared by using the Peterson-type olefination reaction of bis(silyl)methylmetal with carbonyl compounds.3-5 Among the various reported bis(silyl)methylmetals, [bis(2-pyridyldimethylsilyl)methyl]lithium is an extremely efficient reagent for the stereoselective preparation of vinylsilane.6

Preparation of [Bis(2-pyridyldimethylsilyl)methyl]lithium

The synthesis of the starting material bis(2-pyridyldimethylsilyl) methane can be easily accomplished in one-pot by the deprotonation of 2-pyridyltrimethylsilane with t-BuLi followed by reaction with 2-pyridyldimethylsilane (1).7,8 The subsequent generation of [bis(2-pyridyldimethylsilyl)methyl]lithium is easily accomplished by the deprotonation of bis(2-pyridyldimethylsilyl) methane with n-butyllithium in dry diethyl ether (2).6

Reaction of [bis(2-pyridyldimethylsilyl)methyl]lithium with Carbonyl Compounds

The Peterson-type reaction of [bis(2-pyridyldimethylsilyl)methyl]lithium with primary, secondary, and tertiary aliphatic and aromatic aldehydes produces the corresponding 2-pyridyl-substituted vinylsilanes in essentially quantitative yields (entries 1-7, 1, 3).6 The reaction is also applicable to sterically hindered aldehydes (entries 3 and 6) and di-aldehyde (entry 7). The reactions with ketones give disubstituted vinylsilanes with somewhat lower yields (entries 8-10). The reaction can be applied to the stereoselective synthesis of dienylsilanes as well (entries 11-13). In all cases, the reaction occurs in a complete stereoselective fashion (>99% E).

Synthetic Transformations of 2-Pyridyl-substituted Vinylsilane

2-Pyridyl-substituted vinylsilanes can be converted into other vinylsilanes. Subjection of 2-pyridyl-substituted vinylsilanes to potassium fluoride/methanol leads to the formation of methoxy(vinyl)silanes by pyridyl-silyl bond cleavage (4).9 The resultant methoxysilanes can be further allowed to react with Grignard reagents such as phenylmagnesium bromide to give the corresponding vinylsilanes that are commonly used for various transformations (4).10

More practically, 2-pyridyl-substituted vinylsilanes themselves can be directly subjected to the reactions with various electrophiles. For example, treatment of 2-pyridyl-substituted vinylsilanes with acid chlorides in the presence of aluminum chloride affords the corresponding a,b-unsaturated enones (5).11 The reaction of 2-pyridyl-substituted vinylsilanes with bromine and subsequent treatment with sodium methoxide affords the corresponding vinyl bromides (6).11

Related Reagents.

n-Butyllithium; potassium fluoride; phenylmagnesium bromide; aluminum chloride; bromine; sodium methoxide.


1. Peterson, D. J., J. Org. Chem. 1968, 33, 780.
2. Ager, D. J., Org. React. 1990, 38, 1.
3. Gröbel, B. T.; Seebach, D., Angew. Chem., Int. Ed. Engl. 1974, 13, 83.
4. Hudrlik, P. F.; Agwaramgbo, E. L. O.; Hudrlik, A. M., J. Org. Chem. 1989, 54, 5613.
5. (a) Sakurai, H.; Nishiwaki, K.; Kira, M., Tetrahedron Lett. 1973, 4193. (b) Hartzell, S. L.; Rathke, M. W., Tetrahedron Lett. 1976, 2737. (c) Sachdev, K., Tetrahedron Lett. 1976, 4041. (d) Carter, M. J.; Fleming, I., J. Chem. Soc., Chem. Commun. 1976, 679. (e) Seyferth, D.; Lefferts, J. L.; Lambert, R. L., Jr, J. Organomet. Chem. 1977, 142, 39. (f) Seebach, D.; Bürstinghaus, R.; Gröbel, B. T.; Kolb, M., Liebigs Ann. Chem. 1977, 830. (g) Gröbel, B. T.; Seebach, D., Chem. Ber. 1977, 110, 852. (h) Isobe, M.; Kitamura, M.; Goto, T., Tetrahedron Lett. 1979, 3465. (i) Fleming, I.; Pearce, A., J. Chem. Soc., Perkin Trans. 1 1980, 2485. (j) Sato, Y.; Takeuchi, S., Synthesis 1983, 734. (k) Ager, D. J., J. Org. Chem. 1984, 49, 168. (l) Takeda, T.; Ando, K.; Mamada, A.; Fujiwara, T., Chem. Lett. 1985, 1149. (m) Ager, D. J.; East, M. B., J. Org. Chem. 1986, 51, 3983. (n) Inoue, S.; Sato, Y., Organometallics 1986, 5, 1197. (o) Terao, Y.; Aono M.; Takahashi, I.; Achiwa, K., Chem. Lett. 1986, 2089. (p) Marchand, A. P.; Huang, C.; Kaya, R.; Baker, A. D.; Jemmis, E. D.; Dixon, D. A., J. Am. Chem. Soc. 1987, 109, 7095. (q) Kira, M.; Hino, T.; Kubota, Y.; Matsuyama, N.; Sakurai, H., Tetrahedron Lett. 1988, 29, 6939.
6. Itami, K.; Nokami, T.; Yoshida, J., Org. Lett. 2000, 2, 1299.
7. Itami, K.; Mitsudo, K.; Yoshida, J., Tetrahedron Lett. 1999, 40, 5533.
8. Itami, K.; Mitsudo, K.; Yoshida, J., Tetrahedron Lett. 1999, 40, 5537.
9. Itami, K.; Mitsudo, K.; Yoshida, J., J. Org. Chem. 1999, 64, 8709.
10. (a) Fleming, I.; Dunogués, J.; Smither, R., Org. React. 1989, 37, 57. (b) Larson, G. L., J. Organomet. Chem. 1992, 422, 1. (c) Fleming, I.; Barbero, A.; Walter, D., Chem. Rev. 1997, 97, 2063.
11. Itami, K., Mitsudo, K.; Kamei, T.; Koike, T.; Nokami, T.; Yoshida, J., J. Am. Chem. Soc. 2000, 122, 12013.

Jun-ichi Yoshida & Kenichiro Itami

Kyoto University, Yoshida, Kyoto, Japan



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