[66662-17-7] · C9H22OSi2 · 3-Trimethylsilyl-3-trimethylsilyloxy-1-propene · (MW 202.49)
Physical Data: bp 62 °C/35 mmHg; n
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.
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.
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
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
Tohoku University, Sendai, Japan