Synthesis of Piperidinone and Azepanone Fused Indoles via a Wagner–Meerwein Type 1,2-Amide Migration of 2-Spiropseudoindoxyls

Spiropseudoindoxyls were synthesized by using a gold(III)-catalyzed intramolecular nitroalkyne redox–dipolar cycloaddition cascade. These compounds were then transformed into novel piperidinone and azepanone fused indoles via a straightforward hydrogenation. The reaction mechanism of this ring expansion is believed to proceed through a rare Wagner–Meerwein type 1,2-amide migration.