Reductive Alkylation of α-Keto Imines Catalyzed by PTSA/FeCl3: Synthesis of Indoles and 2,3'-Biindoles.

A simple and efficient method for the synthesis of highly functionalized indoles and biindoles was developed. In the reaction protocol, three components were used in one pot and products were obtained in high yield in an easy workup procedure. The reaction occurred via initial reductive alkylation of α-keto imines, followed by a cyclization process in the presence of PTSA/FeCl3 as catalyst.