Regiochemistry of Copper(I)-Mediated Cyclization Reactions of Halo-dienamides

Reaction of 2-substituted dienamides with catalytic amounts of copper halide/tripyridylamine (TPA) furnishes either 5-exo or 6-endo products with the outcome dependent upon the radical initiating unit. Reaction of 3-substituted dienamides produces β-lactams via a 4-exo cyclization with termination of the reaction occurring via either halogen atom transfer, trapping with oxygen, elimination, or radical−radical coupling depending upon the diene.