One-Pot Synthesis of -Fused Benzimidazo-β-carbolines through Sequential Propargylation/-Cycloisomerization Approach.

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

Domino alkyne insertion/aldol reaction/aromatization of 2-alkynyl indole-3-carbaldehyde with 1,3-diketones: entry to 2-indolyl phenols.

A novel one-pot base-promoted insertion of indolyl 2-alkynes into a C-C single bond of 1,3-diketones, followed by intramolecular aldol reaction and dehydrative aromatization is described. This reaction cascade leads to the construction of 2-indolyl phenols involving the formation of the C1-C2 and C3-C4 bonds of phenols resulting from the formal insertion process with a good substrate scope. Further, these bifunctional compounds were used in a novel arylative annulation in the presence of Grignard reagents to provide chromeno-indole frameworks.