Iodine-Catalyzed One-Pot Synthesis of 6H-Indoloquinoline Derivatives

Significance

A method for the synthesis of 6H-indolo[2,3-b]quinoline by reaction of indole 3-aldehyde with anilines under iodine-catalyzed conditions at high temperatures is reported. The yields of the products are dependent on the catalytic amount and the optimum concentration of iodine determined to be 10 mol%. The maximum yield of indoloquinoline derivatives was observed when more than two equivalents of the anilines were used. For R = H, Me, or Br, no significant ­difference in yields of products was observed. α- And β-naphthylamines afforded the best yields. Modest yields were attributed to the decomposition of the Schiff base intermediates under the high-temperature reaction conditions.