Hosomi, A., Endo, M., Sakurai, H. Chemistry of organosilicon compounds. 91. Allylsilanes as synthetic intermediates. II. Synthesis of homoallyl ethers from allylsilanes and acetals promoted by titanium tetrachloride. Chem. Lett. 1976, 941-942.
Hosomi, A., Sakurai, H. Chemistry of organosilicon compounds. 89. Syntheses of γ,δ-unsaturated alcohols from allysilanes and carbonyl compounds in the presence of titanium tetrachloride. Tetrahedron. Lett. 1976, 1295-1298.
The Sakurai allylation (often called the Hosomi-Sakurai reactions) was first reported utilizing stoichiometric amounts of titanium chloride in the presence of an allylsilane and either an aldehyde or ketone to yield the corresponding homoallylic alcohol. The Sakurai reaction has been carried out with various electrophiles in addition to aldehydes and ketones including acetals, ketals, α,β-unsaturated aldehydes and ketones, epoxides and acid chlorides. Low temperatures (-78-25C) are often employed and the reaction is often carried out in dichloromethane under an inert atmosphere. A high degree of regioselectivity is observed with the electrophile attacking the C3 terminus of the allylsilane. In the case of α,β-unsaturated aldehydes reaction occurs at the carbonyl group however for α,β-unsaturated ketones a conjugate addition takes place.
1. The carbonyl is activated by the Lewis acid
2. A carbon carbon bond is formed via attack of the allylsilane.
3. Loss of trimethylsillyl group results in the double bond.