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The first sequential acid-catalyzed propargylation/base-mediated aza -cycloisomerization between indolyl-benzimidazoles and propargylic alcohols is described. This protocol enables the one-pot construction of N -fused benzimidazo-β-carbolines in good yields. The synthetic utility of this approach is demonstrated by the assembly of an aza -helicene and also by a gram-scale reaction.

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.