An Efficient and Short Total Synthesis of (−)‐Heliannuol A by Intramolecular Ullmann C−O Coupling for the Construction of an Eight‐Membered Ether Ring

Abstract

AbstractHerein, we report a method for the synthesis of eight‐membered cyclic ethers by a direct C−O bond connection using an intramolecular Ullmann coupling reaction based on our previously published methodology. We found that allelopathically active heliannuol A could be rapidly synthesised using this method. The use of a strongly coordinating 4‐pyrrolidinopyridine ligand accelerates the reaction rate and leads to the C−O coupling reaction of a typically inaccessible sterically bulky tertiary alcohol. Furthermore, this method circumvents the protection and deprotection steps, presenting a new strategy for the syntheses of benzannulated eight‐membered ring structures.