Dissecting the Gold(I)-Catalyzed Carboaminations of N‑Allyl Tetrahydro-β-carbolines to Allenes

N-Allyl tetrahydro-β-carbolines undergo gold-catalyzed cyclizations that lead to tetracyclic compounds, resulting from both ring closure and the transfer of the allylic group from the nitrogen to the carbon backbone. The final skeleton obtained depends on the nature of both the R2 group of the allene and the R3 group of the allylic residue. Mechanistic studies and DFT calculations allowed the determination of all the mechanistic pathways involved in these processes, stemming from a common intermediate that evolves differently according to the substituents nature.