The subsequent recyclization of compound 155 occurs upon treatment with acetic anhydride, leading to the formation of the methylene sultam 156. Further transformations involve the addition of the cyanide anion to the double C=C bond, resulting in the formation of dicyanoester 157. This compound undergoes hydrolysis and decarboxylation reactions to give the spirocyclic succinimide 158. Throughout these transformations, the nitrile group exhibits desirable properties, including its electron-withdrawing nature, the presence of an electrophilic center, and nucleophilic reactivity.