Bidentate Lewis Acid Catalyzed Domino Diels–Alder Reaction of Phthalazine for the Synthesis of Bridged Oligocyclic Tetrahydro­naphthalenes

A domino process consisting of an inverse and a normal electron-demand Diels–Alder reaction is presented for the formation of bridged tri- and tetracyclic 1,2,3,4-tetra­hydro­naph­thalenes catalyzed by a bidentate Lewis acid. The products were synthesized in a one-pot reaction from commercially available starting materials and contain up to six stereogenic centers. The tetrahydro­naph­thalenes were isolated as single diastereomers and are derivatives of phenyl­ethylamine, which is well-known as a scaffold of amphetamine or dopamine.