Copper-catalyzed N-alkylation of indoles by N-tosylhydrazones

An efficient method for the direct N-alkylation of indoles via copper-catalyzed reductive cross coupling between N-tosylhydrazones and indole reagents has been developed. The reaction was performed in the presence of copper iodide and potassium hydroxide by utilization of tri(p-tolyl)phosphine as a ligand. A wide variety of N-alkylated indoles were obtained in moderate to good yields. The application of the current method to the synthesis of biologically active N-alkylated indole derivatives has also been demonstrated.