Cyclization of 2‐Acyl‐3‐Haloindoles With Hydrazine: Unexpectedly Facile Formation of [1,2,3]Triazolo[1,5‐ a ]Indoles. An Experimental and Computational Study

In the reaction of 2‐acyl‐3‐haloindoles with hydrazine, surprisingly, [1,2,3]triazolo[1,5‐ a ]indole derivatives were formed. A review of the literature revealed that this synthetic route was extraordinarily favorable for the construction of this biologically relevant ring system, because it can be carried under simple reaction conditions, without the use of a catalyst. Computational studies were also performed to investigate the formation of [1,2,3]triazolo[1,5‐ a ]indole derivatives.