Thiourea‐Catalyzed Asymmetric Michael Addition of Carbazolones to 2‐Chloroacrylonitrile: Total Synthesis of 5,22‐Dioxokopsane,Kopsinidine C,and Demethoxycarbonylkopsin

A modified Takemoto catalyst enabled the asymmetric Michael addition of carbazolones to 2‐chloroacrylonitrile to afford 3,3‐disubstituted carbazolones with excellent enantioselectivity. This method was successfully applied to total syntheses of three Kopsia alkaloids which featured an unprecedented Mn^III‐mediated oxidative cyclization to create the caged ring system and a SmI₂‐mediated reductive coupling as key steps.