Palladium-Catalyzed Formal (5 + 2) Annulation between ortho-Alkenylanilides and Allenes

2-Alkenyltriflylanilides react with allenes upon treatment with catalytic amounts of Pd(OAc)2 and Cu(II) to give highly valuable 2,3-dihydro-1H-benzo[b]azepines, in good yields, and with very high regio- and diastereoselectivities. Density functional theory (DFT) calculations suggest that the C–H activation of the alkenylanilide involves a classical concerted metalation–deprotonation (CMD) mechanism.