Synthetically useful β, γ-unsaturated carbonyl compounds having a quaternary carbon at the α-position were prepared with high stereoselectivity by the reaction of a dienolate anion derived from α, β-unsaturated imide having a chiral auxiliary and electrophiles (ethyl acetate and allyl iodide as the C2 and C3 unit, respectively). This method was applied to a short asymmetric synthesis of (+)-ethosuximide.
