[77425-85-5]  · C16H38SiSn  · Tri-n-butyl(trimethylsilylmethyl)stannane  · (MW 377.34)

(precursor to trimethylsilylmethyllithium; methylenation of aldehydes and ketones)

Alternate Name: tributyl(trimethylsilylmethyl)tin.

Physical Data: bp (distillation) 146 °C/2.5 mmHg.

Preparative Methods: is conveniently prepared by the action of Tri-n-butylstannyllithium on (Chloromethyl)trimethylsilane in THF/hexane at 0 °C.1 Alternatively, Trimethylsilylmethylmagnesium Chloride can be treated with Tri-n-butylchlorostannane in refluxing ether.2 Excellent yields (>90%) may be realized by either method.

Handling, Storage, and Precautions: organotin compounds should be considered toxic and should be handled with appropriate care. Use in a fume hood.

Precursor for Trimethylsilylmethyllithium.

Trimethylsilylmethyllithium is a useful reagent for methylenation of aldehydes and ketones (Peterson alkenation),3 for preparation of a-silyl ketones from carboxylic acids, esters, and acid chlorides,4 and for further elaboration to synthetically useful organometallic reagents.5-7 The utility of this versatile organolithium reagent is enhanced by its ready availability from a stable precursor. Peterson reported that tributyl(trimethylsilylmethyl)tin did not undergo transmetalation with n-Butyllithium in hexane at 25 °C and that addition of N,N,N,N-Tetramethylethylenediamine (TMEDA) resulted in minor improvement. Seitz and Zapata1 observed a solvent dependency in the transmetalation reaction and were able to define conditions for rapid and complete conversion of tributyl(trimethylsilylmethyl)tin to trimethyl(silylmethyl)lithium (eq 1).

Methylenation of Carbonyl Compounds.

Tributyl(trimethylsilylmethyl)tin was the reagent of choice in Peterson alkenation of a complex and sterically encumbered decalone derivative (eq 2).8 Methylenetriphenylphosphorane (the Wittig reagent) is often less effective in the case of hindered ketones.

1. Seitz, D. E.; Zapata, A. TL 1980, 21, 3451.
2. Ager, D. J.; Cooke, G. E.; East, M. B.; Mole, S. J.; Rampersaud, A.; Webb, V. J. OM 1986, 5, 1906.
3. Peterson, D. J. JOC 1968, 33, 780.
4. (a) Ruden, R. A.; Gaffney, B. L. SC 1975, 5, 15 (b) Demuth, M. HCA 1978, 61, 3136. (c) Seitz, D. E.; Zapata, A. S 1981, 557.
5. Soderquist, J. A.; Santiago, B. TL 1989, 30, 5693.
6. Anderson, M. B.; Fuchs, P. L. SC 1987, 17, 621.
7. (a) Tessier-Youngs, C.; Beachley, O. T., Jr. Inorg. Synth. 1986, 24, 92 (b) Saulnier, M. G.; Kalow, J. F.; Tun, M. M.; Langley, D. R.; Vyas, D. M. JACS 1989, 111, 8320.
8. Pratt, D. V.; Hopkins, P. B. JOC 1988, 53, 5885.

Larry C. Blaszczak

Lilly Research Laboratories, Indianapolis, IN, USA

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