One-Pot Synthesis of N‑Fused Benzimidazo-β-carbolines through Sequential Propargylation/aza-Cycloisomerization Approach

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.