Oxygenophilic Lewis Acid Promoted Synthesis of 2-Arylindoles from Anilines and Cyanoepoxides in Alcohol.

A convenient synthetic method to indoles from anilines and cyanoepoxides was developed under the catalysis of BF3·OEt2 or AlCl3 in alcohols. The reaction involves a tandem reaction of the regiospecific ring-opening of cyanoepoxides with anilines, elimination of cyanide, intramolecular aromatic electrophilic substitution, and water elimination. The Lewis acid generated protic acid is an efficient catalyst. The method features readily accessible starting materials, wide substrate scope, transition-metal-free environment, and regiospecificity in the ring-opening of cyanoepoxides.