Convenient Synthesis of Tetrahydro‐γ‐carbolines and Tetrahydroquinolines through a Chemo‐ and Regioselectivity Switch by a Brønsted Acid Catalyzed, One‐Pot, Multicomponent Reaction

An efficient, one‐pot, multicomponent reaction of aldehydes 1, p‐methoxyaniline (2a), and 2‐vinylindoles 3 was developed. This approach provides a practical approach to synthetically and biologically significant tetrahydro‐γ‐carboline and tetrahydroquinoline derivatives in good yields through a chemo‐ and regioselectivity switch, which can be tuned by simply changing the substituent on the indole component under identical reaction conditions.