In an effort to develop a novel cascade approach to access tetrahydro-3,4'-biisoquinoline, we hypothesized that intermediate 1a, which could be easy made through a Suzuki coupling from the corresponding bromobenzylcarbamate and 2-(2-ethoxyvinyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 10 could give iminium I under acidic condition (Scheme 2). I could be in equilibrium with the corresponding enamine II through an imine to enamine tautomerization step in order to start the cascade process. 8 In fact, we rationalized that as soon as II is generated, it will immediately react with I leading to intermediate III. The later can undergo another iminium/enamine equilibrium to give IV. Finally, in the presence of air, IV can be oxidized to the desired tetrahydro-3,4'biisoquinoline 2a.