Palladium-Catalyzed Asymmetric Allylic
α-Alkylation of Acyclic Ketones

Significance

While excellent reports for the asymmetric allylic alkylation of cyclic ketones were published recently, the method described here succeeds with acyclic ketone enolates. The use of dioxane is believed to be an important factor for the success of this reaction. Electron-rich aryl rings (in R¹) showed higher enantioselectivities than those with electron-deficient aryl rings. Interestingly, α-branching in R² (i.e. i-Pr) gave a substantial decrease in yield and enantioselectivity (30% yield with 32% ee). The geometry of the starting enolate was important for the absolute sense of stereo­chemistry in the product. When using R¹ = c-Hex and R² = Me the Z form gave 72% yield and 60% ee of the S enantiomer, whereas the E form gave 94% yield and 97% ee of the R enantiomer.