Au-Catalyzed [2 + 3] Annulation of Enamides with Propargyl Esters: Total Synthesis of Cephalotaxine and Cephalezomine H.
Xiao-Yan MaXian-Tao AnXian-He ZhaoJi-Yuan DuYu-Hua DengXiang-Zhi ZhangChun-An FanPublished in: Organic letters (2017)
A novel Au-catalyzed [2 + 3] annulation reaction of enamides with propargyl esters has been developed, providing a new method for expeditious assembly of synthetically useful functionalized 1-azaspiro[4.4]nonane building blocks. Based on this key annulation, strategic installation of the pivotal azaspirocyclic core, followed by constructing the benzazepine unit via Witkop cyclization, led to the divergent total syntheses of cephalotaxine and cephalezomine H.