Synthesis of Bis(indolyl)methane Derivatives by Acid-Catalyzed Reactions of Indoles with Vinyl Ethers

Abstract

2,2-Bis(indol-3-yl)propane derivatives have been synthesized by the reaction of 3-nonsubstituted indoles with 2-methoxypropene in dichloromethane in the presence of a catalytic amount of (±)-camphor-10-sulfonic acid. The similar treatment of 3-substituted indoles with 2-methoxypropene under the same conditions has resulted in the formation of 2,2-bis(indol-2-yl)propanes. The reaction of 3-substituted indoles with ethoxyethene has afforded bis(indol-1-yl)ethanes. Subsequently, 3-substituted indoles have proved to react with excess vinyl ethers under the same conditions to afford the corresponding 1-(1-alkoxyalkyl)indoles.