Rapid Assembly of Protoilludane Skeleton through Tandem Catalysis: Total Synthesis of Paesslerin A and Its Structural Revision.

A multicomponent domino reaction involving three mechanistically distinct Tf2NH-catalyzed reactions was developed. The reaction cascade enables the assembly of a skewed 5/6/4 tricyclic motif with migration of the reactive site with the assistance of a catalyst. The tricyclic product was used to achieve the first total synthesis of cytotoxic paesslerin A by regioselective C-H insertion of the sulfonyl carbenoid and base-promoted olefin isomerization. Our results led to the revision of the originally proposed tricyclic structure of paesslerin A.