Iridium‐Catalyzed Reductive (3+2) Annulation of Lactams Enabling the Rapid Total Synthesis of (±)‐Eburnamonine

A reductive (3+2) annulation of lactams through an iridium‐catalyzed hydrosilylation and a photoredox coupling with a‐bromoacetic acid is developed. The iridium‐catalyzed hydrosilylation of a lactam carbonyl and subsequent elimination provide a transient cyclic enamine, which undergoes iridium‐catalyzed photoredox coupling with a‐bromoacetic acid in a one‐pot process. The developed conditions show high functional group tolerance, and provide cyclic N,O‐acetals including a quaternary carbon center. The resulting N,O‐acetal allows for use of a variety of acid‐mediated nucleophilic additions via iminium ions to give highly substituted cyclic amines. The developed sequence including the reductive (3+2) annulation and acid‐mediated nucleophilic addition is successfully applied to the four‐step total synthesis of (±)‐eburnamonine.