A Facile and Divergent Synthesis of Substituted Pyridine-2,4(1H,3H)-diones and 4H-Thiopyran-4-ones from α-Alkenoyl-α-carbamoyl Ketene-S,S-acetals

Abstract

A facile and 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-2,4(1H,3H)-diones in high yields, whereas in the presence of Na2S·9H2O in DMF at 75°C, tandem intermolecular and intramolecular thia-nucleophilic vinyl substitution reactions, a formal [5C + 1S] annulation, occurred to produce the corresponding substituted 4H-thiopyran-4-ones in good yields.