Silver(I) Triflate‐Catalyzed Protocol for the Post‐Ugi Synthesis of Spiroindolines

A silver(I) triflate‐catalyzed protocol for the post‐Ugi synthesis of tetracyclic spiroindolines has been developed. The protocol worked best for indole‐3‐carbaldehyde‐derived Ugi adducts obtained using anilines and 3‐aryl propiolic acids. Thus, it is complementary to the previous cationic gold‐catalyzed procedure that was developed for analogues Ugi substrates derived from aliphatic amines and 3‐alkyl propiolic acids. Furthermore, we have demonstrated that under our new settings this domino Friedel‐Crafts ipso cyclization / imine trapping process could be efficiently combined with the preceding four‐component Ugi reaction into a two‐step one‐pot transformation.