Palladium-Catalyzed Formal (5 + 2) Annulation between <i>ortho</i>-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-1<i>H</i>-benzo­[<i>b</i>]­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