Total syntheses of chelidonine and norchelidonine via an enamide-benzyne-[2 + 2] cycloaddition cascade.

Total syntheses of chelidonine and norchelidonine featuring an enamide-benzyne-[2 + 2] cycloaddition initiated cascade is described. The cascade includes a pericyclic ring-opening and intramolecular Diels-Alder reaction.