Enantioselective Syntheses of Tetrahydroquinolines Based on Iridium-Catalyzed Allylic Substitutions: Total Syntheses of (+)-Angustureine and (-)-Cuspareine

A protecting-group-free two-step approach for the preparation of tetrahydroquinolines has been developed. The procedure involves a highly regio- and enantioselective intermolecular iridium-catalyzed allylic amination followed by one-pot hydroboration and intramolecular SuzukiMiyaura cross-coupling. This method was applied in total syntheses of the alkaloids (+)-angustureine and ()-cuspareine.