Stereoselective Synthesis of Benzo[]quinolizidines via Aerobic DDQ-Catalyzed Allylation and Reductive Cyclization.

Stereoselective synthesis of C-substituted benzo[]quinolizidines via redox-controlled catalytic C-C-bond-forming reactions was carried out. Aerobic DDQ-catalyzed allylation of -Cbz tetrahydroisoquinolines efficiently provided α-allylated products , which were transformed to enones via cross-metathesis reactions using the second-generation Hoveyda-Grubbs catalyst. Palladium-catalyzed hydrogenation of prompted alkene reduction, protecting group removal, and intramolecular reductive amination in one step to afford the desired benzo[]quinolizidines as single diastereomers.