Synthesis of Pyridones from Enamines and Cyanoacetic Acids

Article abstract of DOI:10.1007/BF00799955

Reaction of enamines 1a-e with cyanoacetic acids 2a, b in acetic anhydride at about 100 deg C yields the α-cyanoacetylated enamines 3a-g.Under the same conditions methyl 4-cyano-2-(2-pyridyl)-acetoacetate 3h is obtained from methyl 2-pyridylacetate and 2a.Compounds 3 are cyclized in hydrochloric acid yielding the 4-hydroxy-2-pyridones 4; on the other hand in ethanolic sodium ethoxide solution the 2-amino-4-pyridones are obtained.The esters 5a, b and d are saponified to give the acids 7a-c which decarboxylate at 250 deg C to 8a-c. - keywords: 2-Amino-4-pyridones; 4-Hydroxy-2-pyridones; Ritter-Reaction