Rhodium(I)-Catalyzed Allenic Carbocyclization Reaction Affording δ- and ε-Lactams

This letter extends the scope of the rhodium(I)-catalyzed allenic Alder-ene carbocyclization reaction to the preparation of δ- and ε-lactams from amides. A variety of allenic propiolamides were cycloisomerized to give a number of unsaturated δ-lactams. In addition, allenic propargylamides give good yields of the corresponding ε-lactams. Formation of lactams possessing these ring sizes has rarely been accomplished via transition-metal-catalyzed carbon−carbon bond forming strategies. Thus, this approach provides an alternative strategy for synthesizing these substructures.