A simple and general approach for the synthesis of highly functionalized 6-oxo-1,6-dihydropyridines

A variety of 5-cyano-4-methylthio-6-oxo-1,6-dihydropyridine-3-carboxylates have been efficiently synthesized in a one-pot reaction from N-alkyl and N-aryl derivatives of 2-cyano-3,3-bis(methylthio)acrylamides and selected β-keto esters. The reaction proceeds via potassium hydrogen carbonate mediated conjugate addition of a β-keto ester to 2-cyano-3,3-bis(methylthio)acrylamide followed by loss of methyl mercaptan and subsequent intramolecular condensation of amide group with the acyl carbonyl group. The mechanism of the reaction has been established by isolation of the 2-acetyl-4-cyano-5-amino-3-(methylthio)-5-oxopent-3-enoate intermediate and its independent cyclization to the desired 6-oxo-1,6-dihydropyridine.