Novel, Chiral, and Enantiopure C ₂ ?Symmetric Thioureas Promote Asymmetric Protio?Pictet?Spengler Reactions by Anion?Binding Catalysis

Although anion-binding processes are well-known for their crucial role in molecular recognition, they have only recently been utilized catalysis. Herein, a new class of chiral, enantiopure C2-symmetrical thioureas that, combination with 4-methoxybenzoic acid, promotes the enantioselective protio-Pictet-Spengler reaction to provide unprotected tetrahydro-?-carbolines good yields (40–93 %) and moderate-to-high enantioselectivities (34–95 % ee) one step from tryptamine aldehyde derivatives is described. The formation chiral catalyst-anion complex was explored by 1H NMR.