Synthesis of 4,5,6-trisubstituted 2,3-pyridinediones via Mannich reaction and oxidation–Michael addition of 3-hydroxy-2(1H)-pyridinones

4 - Substituted 3-hydroxy-2(1 H )-pyridinones 2 were prepared by Mannich reaction of 3-hydroxy-2(1 H )-pyridinones with secondary amines and formaldehyde. The isolated products were then reacted with aromatic amines in the presence of NaIO 3 as oxidant via oxidation–Michael addition to yield 4,5,6-trisubstituted-2,3-pyridinediones 3 in good yields (80.2–88.9%). The structures of the products were characterized by 1 H NMR, ESI-MS, and IR, and elemental analysis.