An efficient method for the construction of polysubstituted 4-pyridones via self-condensation of β-keto amides mediated by P(2)O(5) and catalyzed by zinc bromide

A self-condensation cyclization reaction mediated by phosphorus pentoxide (P(2)O(5)) and catalyzed by zinc bromide (ZnBr(2)) is presented for the synthesis of polysubstituted 4-pyridones and 2-pyridones from β-keto amides. A variety of β-keto amides are used in this approach, and a wide range of functionalized 4-pyridones and 2-pyridones were obtained in good to excellent yields. When employing the N-aryl β-keto amides as the substrates in this protocol, 4-pyridones are resulted, however, when using N-aliphatic-substituted β-keto amides as the partners of N-aryl β-keto amides under the same conditions, 2-pyridones are afforded.