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

Abstract

Double stereocontrol is achieved in the Pd-catalyzed cyclization of Δ -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 = Ph PCH CH PPh ), and the reaction time.

Asymmetric Total Synthesis of (+)-Intricenyne via an Endocyclization Route to Oxocane Skeleton

“…The oxocane 6 would be effectively constructed by the substrate-controlled Pd(0)-catalyzed endocyclization of allylic acetate 7 , which should be certainly established for our reliable strategy. In particular, the α,α′- cis -stereochemistry of the oxocane system could be effectively controlled by our synthetic route. , The cyclization precursor 7 possessing three stereogenic centers can be convergently prepared by the coupling of epoxide 8 with alkoxybutanol 9 via an acid-catalyzed regio- and diastereoselective epoxide ring opening reaction …”