Synthesis of Indole Derivatives via Aryl Triazole Ring-Opening and Subsequent Cyclization.

A metal-free two-step synthetic approach for obtaining indole derivatives from aryl triazole fragment-containing compounds has been developed. In the first step, the Dimroth equilibrium, followed by nitrogen extrusion, Wolff rearrangement, and amine nucleophile addition, leads to the formation of -aryl ethene-1,1-diamines. In the second step, the latter intermediates are cyclized into the target 1-indoles in the presence of iodine. The developed method ensures the synthesis of indoles that possess -substituents at the indole 2 position. Depending on the applied -nucleophile, the indolization step provides a selectivity either towards 1-indoles or 1-aryl-1-indoles.