[5180-98-8]  · C7H20OSi2  · (Methoxydimethylsilyl)(trimethylsilyl)methane  · (MW 176.45)

(Peterson alkenation reagent; synthesis of vinyl silanes from aldehydes and ketones1)

Physical Data: bp 150-152 °C,2 54-58 °C/20 mmHg.3

Solubility: sol common organic solvents (THF, Et2O, CH2Cl2, pentane, etc.)

Analysis of Reagent Purity: 1H NMR (CDCl3) d 3.38 (s, 3 H), 0.10 (s, 6 H), 0.02 (s, 9 H), -0.14 (s, 2 H); 13C NMR (CDCl3) d 49.94, 4.14, 1.13, 0.03.3

Preparative Methods: prepared in 75% yield by treatment of MeOSiMe3 with t-Butyllithium in pentane at -78 °C to ambient temperature followed by addition of Chlorotrimethylsilane at 0 °C.2 Alternatively, the reagent is prepared in 34% yield by treatment of Trimethylsilylmethylmagnesium Chloride with Dichlorodimethylsilane followed by LiOMe in THF.3

Handling, Storage, and Precautions: use in a well-ventilated fume hood. Contact with the eyes and skin should be avoided.

Peterson Alkenation Reactions.4

The synthesis of vinylsilanes via alkenation reactions of [bis(trimethylsilyl)methyl]lithium is restricted to nonenolizable aldehydes and ketones.5 However, [(methoxydimethylsilyl)(trimethylsilyl)methyl]lithium (1), generated from the title reagent by treatment with t-Butyllithium in pentane at rt, undergoes Peterson alkenation with aldehydes and ketones to give vinylsilanes in good yield (eq 1). Interestingly, the methoxydimethylsilyl unit is preferentially eliminated from the b-hydroxydisilane intermediate. Alkenation reactions of (1) with aldehydes and unsymmetrical ketones are only moderately stereoselective (eqs 2 and 3).

Avery and co-workers have applied this methodology to the synthesis of vinylsilane intermediates utilized in syntheses of artemisinin analogs (eqs 4 and 5).6 The low efficiency of these Peterson alkenation reactions (31-50%) suggests that the relatively hindered carbonyl groups undergo competitive deprotonation by the anion (1).

Related Reagents.

Bis(trimethylsilyl)methane; Tris(trimethylsilyl)methane.

1. Bates, T. F.; Thomas, R. D. JOC 1989, 54, 1784.
2. Bates, T. F.; Thomas, R. D. JOM 1989, 359, 285.
3. Bain, S.; Ijadi-Maghsoodi, S.; Barton, T. J. JACS 1988, 110, 2611.
4. (a) Ager, D. J. OR 1990, 38, 1. (b) Kelly, S. E. COS 1991, 1, 729. (c) Chan, T.-H. COS 1991, 2, 595. (d) Colvin, E. W. Silicon Reagents in Organic Synthesis; Academic: New York, 1988; p 63.
5. (a) Grobel, B. T.; Seebach, D. AG(E) 1974, 13, 83. (b) Grobel, B. T.; Seebach, D. CB 1977, 110, 852. (c) Sakurai, H.; Nishiwaki, K.; Kira, M. TL 1973, 4193.
6. (a) Avery, M. A.; Chong, W. K. M.; Bupp, J. E. CC 1990, 1487. (b) Avery, M. A.; Chong, W. K. M.; Detre, G. TL 1990, 31, 1779.

William R. Roush

Indiana University, Bloomington, IN, USA

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