Synthesis of Spiro‐polycyclic Indolin‐3‐ones from Arylamine and Styrylglyoxal via Copper‐Mediated Sequential Annulation

Comprehensive Summary Structurally novel spiro‐fused hexacycles, containing three indole‐related structural domains: indolinone, indoline and indole, have been created by a sequential annulation of arylamine and styrylglyoxal. Up to five chemical bonds and three densely arranged rings are concurrently forged in this one‐step protocol. Copper‐catalyzed aerobic oxidation proceeds mechanistically through the entire domino sequence, incorporating an unusual radical‐polar crossover between the styrene and arylamine. Spiro‐indene‐indolin‐3‐one motifs are selectively obtained by simple manipulation of the substitution pattern of styrylglyoxal.