Nickel-Catalyzed Direct Synthesis of N -Substituted Indoles from Amino Alcohols and Alcohols.

A one-pot cascade approach for the synthesis of N -substituted indoles from amino alcohols and alcohols under additive and base-free conditions with the liberation of water as the only stoichiometric byproduct is reported. The commercially available bench-stable Ni(OTf) 2 salt in combination with 1,2-bis(dicyclohexylphosphino)ethane (dcype) is very effective for this unprecedented catalytic transformation. A broad range of substrates including aromatic and aliphatic primary alcohols, cyclic and acyclic secondary alcohols, and various substituted 2-aminophenyl ethyl alcohols are employed in the reaction conditions to provide a diverse range of N -alkylated indoles. Mechanistic studies revealed that the reaction proceeds through tandem N -alkylation via hydrogen autotransfer followed by the cyclization of N -alkylated alcohol intermediate.