DBU-Promoted Cascade Selective Nucleophilic Addition/C-C Bond Cleavage/Hetero-Diels-Alder Reactions of 2-Amino-4H-chromen-4-ones with β-Nitrostyrenes and/or Aryl Aldehydes: Access to 5H-Chromeno[2,3-b]pyridin-5-ones

DBU-promoted cascade selective nucleophilic addition/C-C bond cleavage/hetero-Diels-Alder reactions accompanied by aromatization of substituted 2-amino-4H-chromen-4-ones with substituted beta-nitrostyrenes or with the combined substituted beta-nitrostyrenes and aromatic aldehydes were developed for the synthesis of 2,4-diaryl-substituted 5H-chromeno[2,3-b]pyridin-5-ones. This procedure provides a highly efficient and facile route to functionalized 5H-chromeno[2,3-b]pyridines from readily available substrates under mild reaction conditions.