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.