<i>N</i>-Heterocyclic Carbene-Catalyzed [3 + 3] Annulation of Enals with Aminonaphthoquinones for the Synthesis of Functionalized Aza-anthraquinones

Rapid construction of functionalized aza-anthraquinones has been successfully developed via NHC-catalyzed formal [3 + 3] annulation of 2-aminoquinones with enals. This reaction features several advantages, such as readily available starting materials, mild reaction conditions, and flexible product transformations. The study on the atroposelective version of this strategy was also carried out, and several C–N axial chiral aza-anthraquinones were synthesized in moderate yields with moderate to good enantioselectivities.