Synthesis of Indolo[1,2-b]indazole Derivatives via Copper(I)-Catalyzed Intramolecular Amination Reaction

A versatile method for preparation of indolo[1,2-b]indazole derivatives was developed by using an intramolecular amination reaction of 1-aminoindoline derivatives in reaction with CuI/PHAN/K2CO3 (250 mol%) in 1,4-dioxane at 105 °C. The method provides indoles fused with indazole rings in good yields.