Rapid Access to 3-(Aminomethyl)isoquinoline-Fused Polycyclic Compounds by Copper-Catalyzed Four-Component Coupling, Cascade Cyclization, and Oxidation

A novel copper-catalyzed synthesis of 3-(aminomethyl)isoquinoline-fused polycyclic compounds, through four-component coupling, cyclization, and oxidation, has been developed. A Mannich-type reaction of 2-ethynylbenzaldehyde with paraformaldehyde and a secondary amine followed by treatment with a diamine component gave tricyclic isoquinolines through cascade cyclization and oxidation. Construction of fused isoquinolines of various ring sizes is also presented.