Diastereoselective and Stereodivergent Synthesis of 2‐Cinnamylpyrrolines Enabled by Photoredox‐Catalyzed Iminoalkenylation of Alkenes

A photoredox‐catalyzed iminoalkenylation of γ‐alkenyl O‐acyl oximes has been developed. Readily available alkenylboronic acids serve as alkenylation reagents, leading to densely functionalized pyrrolines. Both (E)‐ and (Z)‐cinnamylpyrrolines are accessible depending on the reaction solvent. In dichloromethane, (E)‐cinnamylpyrrolines are produced through a photoredox‐mediated single‐electron‐transfer process. In tetrahydrofuran, (Z)‐cinnamylpyrrolines are generated by photocatalytic contra‐thermodynamic E‐to‐Z isomerization of (E)‐cinnamylpyrrolines though an energy‐transfer pathway. Two stereocenters are established with complete diastereoselectivity and only one diastereomer is isolated. A photoredox‐catalyzed iminoalkenylation of γ‐alkenyl O‐acyl oximes has been developed. Readily available alkenylboronic acids serve as alkenylation reagents, leading to densely functionalized pyrrolines. Both (E)‐ and (Z)‐cinnamylpyrrolines are accessible depending on the reaction solvent. Two stereocenters are established with complete diastereoselectivity and only one diastereomer is isolated. PC=photocatalyst, SET=single‐electron transfer, EnT=energy transfer.