Allylations of Chelated Enolates Using Dienyl Substrates

Isomerization-free reactions of dienyl carbonates (1−3) with chelated amino acid ester enolates at −78 °C provide important information concerning the mechanism of these dienylations. The formation of regioisomeric products can be explained by competing S_N2/S_N2‘ reactions, and the product distribution can be influenced by proper choice of the reaction conditions.