Highly Enantioselective [3+2] Annulation of Indoles with Quinones to Access Structurally Diverse Benzofuroindolines

A facile and efficient method to produce optically pure benzofuroindolines, especially those without 3-substituents that are susceptible to rearomatization, through [3+2] annulation of indoles with quinones is described. The suitable combination of a BOX ligand Cu^II hydrate complex and freshly activated molecular sieves functions to give controllably dynamic release of water, which enables the success of this reaction. This reaction can be performed on a gram scale with only 0.5 mol % catalyst loading.