Synthetic access to poly-substituted 6-alkoxyindoles from 1,3-cyclohexanediones and nitroolefins through facile aromatization reaction.
6-Alkoxy-3-arylindoles were efficiently prepared from 1,3-cyclohexanedione enol ethers and beta-nitrostyrenes. Michael addition using the kinetically generated enolate, followed by Zn reduction of a nitro group of the resulting adducts produced the nitrones which were then treated with acetic anhydride to induce aromatization by dehydration and N-acetylation, which furnished the desired indoles by the DDQ oxidation. This methodology provides an easy entry toward various poly-substituted 6-alkoxyindoles.