Pd-Catalyzed Tandem Synthesis of Polysubstituted Pyridines Using β-Enamino Esters and β-Ketodinitriles

A novel and efficient method for the synthesis of multifunctionalized pyridines has been developed through a chemoselective [3 + 3] cycloaddition of β-enamino esters with β-ketodinitriles using a combination of Pd(OAc)₂, CuBr₂, and AgOAc in DMF at 60 °C for 24 h. This transformation proceeds via sequential C-N and C-C bond formation involving nucleophilic addition, intramolecular cyclization, and subsequent aromatization. The protocol exhibits a broad substrate scope, good functional group tolerance, and further demonstrates a postsynthetic modification, highlighting its synthetic utility.