Directed synthesis of 2-spiroindolines from indole derivatives by formic acid-induced N-acyliminium ion-conjugated diene spirocyclization

Synthesis of 2-spiroindolines from 2-substituted indole derivatives via acid-induced N-acyliminium ion-conjugated diene spirocyclization was demonstrated. This methodology can be used to direct transformations of 2-substituted indole moieties into 3-nonsubstituted-2-spiroindoline skeletons.