Base-Promoted and Copper(I)-Catalyzed Tandem Cyclization-C(sp²)-N Coupling of Vinyl Malononitriles with <i>Ortho</i>-Nitrochalcones: Access to Acridones and their Fused Derivatives

An efficient Cs₂CO₃-promoted and copper(I)-catalyzed double cyclization of <i>ortho</i>-nitrochalcones with vinyl malononitriles for the <i>de novo</i> access to a variety of tri- and tetra-substituted acridones and their fused derivatives with a value-added CN group has been developed for the first time. This one-pot operation proceeds through a Michael-cyclization-aromatization, followed by regioselective <i>ipso</i>-amination via nucleophilic aromatic substitution (S_NAr) reaction, resulting in two C═C bonds and a C-N bond for acridone ring synthesis. This economic strategy based on 100% carbon atoms ensures the successive formation of two rings in a one-pot operation, good to high yields, a wide range of substrates, and good tolerance of functionalities. In addition, acridones were converted into several value-added acridones and acridines, highlighting the synthetic versatility and usefulness of the prepared acridone derivatives.