Regioselective construction of pyrido[1,2,3-<i>de</i>]quinoxaline-2,5-diones through acid-mediated post-Ugi rearrangements

We report a robust method for preparing uniquely functionalized pyrido[1,2,3-<i>de</i>]quinoxaline-2,5-diones from alkynamide-containing Ugi adducts under acidic conditions. This single-step process proceeds through spirocyclization of Ugi adducts followed by intramolecular condensation and ring expansion in a highly regioselective manner. Mechanistic studies and DFT calculations were performed to establish the reaction path and possible intermediates.