Synthesis of Novel Symmetric Cyclic Indole-tetramers

The reaction of 5-bromoindolin-2-one with phosphoryl chloride in chlorobenzene gave a novel symmetric isomer of a cyclic indole-tetramer.This novel isomer was used in Suzuki-Miyaura coupling reaction to give tetraarylated derivatives of the cyclic indole-tetramer.Bergman and Ekulund reported that liner 2, 3-linked indole tetramer (2) was prepared when bisindole (1) which was synthesized from N-methyl-2-iodoindole, and N-methylindolin-2-one treated with phosporyl chloride 6 (Scheme 1).