First indium trichloride catalyzed self-addition of indoles: One pot synthesis of indolylindolines

Indole (1), 5-methoxyindole (1c) and their N-substituted derivatives undergo self-addition to afford indolylindoline derivatives 2a-e and trimers 4a-e in fairly good yield in the presence of catalytic amount (20 mol%) of anhyd indium trichloride.