A metal-free
oxidative intramolecular dearomative spirocyclization
of indole-3-formyl-2-carboxamides has been developed for the first
time, affording spiropseudoindoxyls in good yields. This domino process
proceeds through sequential oxidation, decarboxylation and ipso-arylation. The unique feature of this approach includes
the compatibility of N-protected-indole-2-carboxamides.
Further, a hitherto unknown rearrangement of spiropseudoindoxyls to
indoloquinolones has been achieved. The synthetic utility of this
strategy has also been showcased by the construction of a natural
alkaloid, isocryptolepine.