N-Iodosuccinimide-Promoted Synthesis of Indolo[3,2-c]quinolizines via Cascade Intramolecular C–N Bond Formation/Aromatization with 3-(1H-Indol-3-yl)-2-(pyridin-2-yl)propanoates

An NIS-promoted cascade of intramolecular C-N bond formation/aromatization with 3-(1H-indol-3-yl)-2-(pyridin-2-yl)propanoates is described for synthesizing a polycyclic indole skeleton, indolo[3,2-c]quinolizine, as well as 1,9-dihydropyrazolo[4',3':5,6]pyrido[2,3-b]indole. The advantages of this protocol include accessible starting materials, mild conditions, simple operation, and good yields. Indolo[3,2-c]quinolizines exhibited good fluorescence properties and effective staining for live cells, targeting lysosomes and mitochondria. Additionally, the products showed significant antiproliferative activity against tumor cells in the MTT assay.