divergent synthesis of substituted pyridine-2,4(1H,3H)-diones and 4H-thiopyran-4-ones from readily available α-alkenoyl-α-carbamoyl ketene-S,S-acetals has been developed. Subjected to N,N-dimethylformamide at 125°C, α-alkenoyl-α-carbamoyl ketene-S,S-acetals underwent an intramolecular aza-nucleophilic vinyl substitution reaction, a formal [5C + 1N] annulation, to give the corresponding substituted pyridine-2