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 photoredox-mediated a 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.