Synthesis of Unsaturated Nine-Membered Ring Ethers (Δ3-Oxonenes) Containing aZ- orE-Configurated Double Bond: Thermodynamic versus Kinetic Control in Palladium-Catalyzed Allylic Cyclizations

Double stereocontrol is achieved in the Pd-catalyzed cyclization of Δ3-oxonene precursors (see reactions outlined below). The configuration of the olefinic double bond and of the allylic carbon center α to the ether oxygen atom is dictated by the configuration of the double bond in the starting compound (E/Z), the Pd ligand (dppe = Ph2PCH2CH2PPh2), and the reaction time.