Calcium iodide (CaI2) catalyzes cycloaddition reaction in Nenitzescu synthesis to afford 5-hydroxyindoles from corresponding quinones and enamines. This method introduces CaI2 as a catalyst in performing this type of condensation reaction for the first time and presents advantages in using nontoxic metal, work-up simplicity, functional group tolerance, and can compete with other methods to overcome the current problems such as low yield and polymerization side reactions.