One-Pot Synthesis of Functionalized [6–5–6–6–3] Heteropentacyclic Indolo[3,2,1- <i>de</i> ][1,5]naphthyridine-Fused Scaffold via Multistep Cascade Annulation with α-Aryl Vinylsulfoniums

Herein, we develop a simple and straightforward method to access a [6-5-6-6-3] heteropentacyclic indolo[3,2,1-<i>de</i>][1,5]naphthyridine-fused scaffold through multistep cascade reactions involving α-aryl vinylsulfoniums. Under mild reaction conditions, the reaction is applicable to β-carboline-based chalcones and 1-carbonyl-9<i>H</i>-β-carbolines, delivering the indolo[3,2,1-<i>de</i>][1,5]naphthyridine-fused cyclopropane and oxiranes in moderate to excellent isolated yields. In addition, the scale-up synthesis, derivatizations of products, and late-stage functionalization of bioactive molecules also demonstrated the potential utility of this method. Particularly, a preliminary biological evaluation exhibited moderate to good cytotoxicity in vitro against multiple types of tumor cells.