A Tandem Oxidative Annulation Strategy for the Synthesis of Tetracyclic 3‑Spirooxindole Benzofuranones

A simple and efficient method was developed for the construction of the medicinally important tetracyclic 3-spirooxindole benzofuranones. In this highly atom- and step-economical one-pot protocol, one quaternary carbon center, two new cycles, and four new bonds (C–C/C–O/C–N) were formed under simple ligand-free copper-catalyzed conditions through a novel tandem oxidative annulation strategy.