Tris(trimethylsilyl)methane1

(Me3Si)3CH

[1068-69-5]  · C10H28Si3  · Tris(trimethylsilyl)methane  · (MW 232.65)

(precursor of (Me3Si)3CLi, useful to introduce bulky tris(trimethylsilyl)methyl (trisyl) group; Peterson alkenation reagent)

Physical Data: bp 219 °C, 93-95 °C/13.5 mmHg; d 0.836 g cm-3; n20D 1.4657.

Solubility: sol common organic solvents.

Analysis of Reagent Purity: 1H NMR.

Purification: by distillation.

Preparative Methods: the reaction of Chlorotrimethylsilane, Lithium metal, and Chloroform in THF gives tris(trimethylsilyl)methane.2

Handling, Storage, and Precautions: can be stored in a glass bottle.

Synthesis of Tris(trimethylsilyl)methyl Bromide.3

Tris(trimethylsilyl)methyl bromide (trisyl bromide) can be prepared in 75% yield by photochemical bromination of neat tris(trimethylsilyl)methane at 180-190 °C in less than 5 h (eq 1).

Trisyl bromide is very reactive toward lithium, magnesium, and phenyllithium to give the corresponding organometallic reagents. These reagents are useful in the Peterson alkenation reaction.

Metalation.

Tris(trimethylsilyl)methyllithium can be prepared by metalation of tris(trimethylsilyl)methane by Methyllithium in a mixture of diethyl ether and THF (eq 2).4 An improved procedure is described as follows. To a solution of tris(trimethylsilyl)methane in THF is added a solution of MeLi (10% excess) in diethyl ether with stirring under nitrogen. The diethyl ether is distilled off and the residual solution is boiled under reflux under nitrogen. After 2 h, about 95% of tris(trimethylsilyl)methane is converted to tris(trimethylsilyl)methyllithium. Tris(trimethylsilyl)methyllithium is important for the introduction of (Me3Si)3C (trisyl) groups, and for use in Peterson alkenations (eq 3).

Formation of Bis(trimethylsilyl)methyllithium.

The carbon-silicon bond of tris(trimethylsilyl)methane can be cleaved by lithium methoxide in HMPA to form bis(trimethylsilyl)methyllithium, which subsequently reacts with carbonyl compounds to form alkenes (eq 4).5

Similar cleavage of the Si-C bond occurs with fluoride ion. The in situ reaction with carbonyl compounds gives the corresponding alkenes. Thus the reaction of tris(trimethylsilyl)methane with nonenolizable carbonyl compounds in the presence of Tris(dimethylamino)sulfonium Difluorotrimethylsilicate (TASF) gives the corresponding alkenes in excellent yield (eq 5).6

Related Reagents.

Bis(trimethylsilyl)methane.


1. FF 1975, 5, 617.
2. Merker, R. L.; Scott, M. J. JOM 1965, 4, 98.
3. Smith, C. L.; James, L. M.; Sibley, K. L. OM 1992, 11, 2938.
4. Cook, M. A.; Eaborn, C.; Jukes, A. E.; Walton, D. R. M. JOM 1970, 24, 529.
5. Sakurai, H.; Nishiwaki, K.; Kira, M. TL 1973, 4193.
6. Palomo, C.; Aizpurua, J. M.; García, J. M.; Ganboa, I.; Cossio, F. P.; Lecea, B.; López, C. JOC 1990, 55, 2498.

Hideki Sakurai

Tohoku University, Sendai, Japan



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