Gold-Catalyzed Asymmetric Intramolecular Cyclization of N-Allenamides for the Synthesis of Chiral Tetrahydrocarbolines

The highly enantioselective gold-catalyzed intramolecular cyclization of N-allenamides was implemented utilizing a designed chiral sulfinamide phosphine ligand (PC-Phos), which, of note, represents the first example of highly enantioselective intramolecular cyclization of N-allenamides. The practicality of this reaction was validated in the total synthesis of (R)-Desbromoarborescidine A and formal synthesis of (R)-Desbromoarborescidine C and (R)-Deplancheine. Moreover, the catalyst system PC-Phos/AuNTf2 proved to be specifically efficient to promote the desymmetrization of N-allenamides in excellent yields with satisfactory ees.