[66662-17-7]  · C9H22OSi2  · 3-Trimethylsilyl-3-trimethylsilyloxy-1-propene  · (MW 202.49)

(homoenolate anion2 and homoenolate dianion3 equivalents; synthesis of acylsilanes)

Physical Data: bp 62 °C/35 mmHg; n20D 1.4228.

Preparative Methods: allyl trimethylsilyl ether is lithiated with s-Butyllithium in THF-HMPA to give a rapidly equilibrating mixture of a carbanion and a silylallyloxy anion (eq 1). Silylation of the mixture with Chlorotrimethylsilane affords 3-trimethylsilyl-3-trimethylsilyloxy-1-propene (1) exclusively. Several other derivatives with bulky substituent(s) on the silyloxy group were also prepared.2

Handling, Storage, and Precautions: use in a fume hood.

Homoenolate Anion Equivalent.

The reaction of (1) with acid chlorides in the presence of Titanium(IV) Chloride affords the corresponding g-keto aldehydes after hydrolysis (eq 2).2 O-Acylation to form the 1-silyl allyl ester (17-30%) competes with the SE alkylation of the double bond. Bulkier silyloxy derivatives give g-keto aldehydes in higher yield.

Homoenolate Dianion Equivalent.

The intermediate in the reaction is believed to be an enol silane and/or enol titanate which gives the expected product with carbon electrophiles such as acetals (eq 3).3

Synthesis of Acylsilanes.

The title reagent (1) and other related derivatives undergo sequential isomerization to a-silylalkenyl ethers upon treatment with Palladium on Carbon which subsequently give acylsilanes by hydrolysis (eq 4).4

Related Reagents.

Allyltrimethylsilane; 1-Ethoxy-1-(trimethylsilyloxy)cyclopropane; 1-Methoxyallyllithium; Trimethylsilylallyllithium.

1. Fieser, M. FF 1980, 8, 485.
2. Hosomi, A.; Hashimoto, H.; Sakurai, H. JOC 1978, 43, 2551.
3. Hosomi, A.; Hashimoto, H.; Kobayashi, H.; Sakurai, H. CL 1979, 245.
4. Hosomi, A.; Hashimoto, H.; Sakurai, H. JOM 1979, 175, Cl.

Hideki Sakaurai

Tohoku University, Sendai, Japan

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