Cascade electrophilic iodocyclization: efficient preparation of 4-iodomethyl substituted tetrahydro-β-carbolines and formal synthesis of oxopropaline G.

4-Iodomethyl substituted tetrahydro-β-carbolines, the core structure of numerous natural products and bioactive molecules, are readily prepared via I2-promoted cascade electrophilic cyclization. The reactivity differences of olefins and alkynes ensure that the reaction proceeds smoothly. This methodology was successfully applied to the formal synthesis of oxopropaline G.