Anionic [4 + 3] Heteroannulation of 2-Azidoacrylates: A Modular Synthesis of 2-Benzazepin-1-ones.

2-Azidoacrylates undergo [4+3] annulation with phthalides under anionic conditions at low temperatures to furnish 5-hydroxy-2-benzazepinones, the formation of which represents a new concept for the construction of azepines as well as a new reactivity of 2-azidoacrylates.