Iridium-Catalyzed Intermolecular Allylic Etherification with Aliphatic Alkoxides:Asymmetric Synthesis of Dihydropyrans and Dihydrofurans

摘要

Elimination and racemization limit the synthesis of sterically hindered ethers,such as alpha-chiral ethers,by the Willamson synthesis.Enantioselective transition-metal-catalyzed allylic substitution could be used to prepare these materials from achiral or racemic allylic electrophiles,but intermolecular enantioselective reactions of allylic acetates or carbonates with alkoxides are limited.Enantioselective reactions of phenoxides are well documented,but no metal catalyzes intermolecular enantioselective allylations of alkoxides with broad scope.