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.

Automated summary

A novel method for the synthesis of N-substituted indoles under additive and base-free conditions is reported. The method utilizes a one-pot cascade approach with water as the only stoichiometric byproduct. The catalytic system used in this transformation exhibits high efficiency. A diverse range of N-alkylated indoles can be synthesized using various substrates.