Synthesis of Spiroindolenines by Iodine‐Mediated Dearomative Aza‐Spirocyclization of Indoles

A transition‐metal‐free dearomative aza‐spirocyclization reaction of 2,3‐disubstituted indoles is established by using molecular iodine under basic conditions. The required substrates were prepared via sequential Fisher indole synthesis and sulfonylation. This dearomatization reaction is amenable to gram‐scale synthesis, and provides access to various spiroindolenine derivatives from indole sulfonamide precursors.