An Eco‐Friendly Route to <i>N</i>‐Arylindoles by Iron‐Catalyzed [2+2+2] Cycloaddition of Diynes with (Indol‐1‐yl)alkynes

Abstract

Abstract A new pathway to the synthesis of N ‐arylindoles has been developed that proceeds through an iron‐catalyzed [2+2+2] cycloaddition reaction between diynes and indole‐ N ‐alkynes. The reaction is carried out in ethanol and employs a catalyst system that consists of iron(II) chloride tetrahydrate as the metal source, 2‐[(2,6‐diisopropylphenyl)iminomethyl]pyridine (dipimp) as the ligand, and zinc as the reducing agent. The method provides efficient access to 3‐carbonyl/ester‐substituted (indol‐1‐yl)arenes in good to excellent yields under green reaction conditions, and these products are structurally similar to other N ‐arylindole derivatives with potential medicinal value.