The excited state of phthalimide anion adds to cyclic, acyclic and aryl-conjugated alkenes in an efficient and regioselective manner to form [2]benzazepine-1,5-diones, substituted at positions 3 and/or 4. The reaction is independent of the ionization potential of the alkene. This process contrasts with the related reactions of N-methylphthalimide or phthalimide, which are limited by the requirement