Synthesis of 2,3-Dihydro-4-pyridones and 4-Pyridones by the Cyclization Reaction of Ester-Tethered Enaminones.

2,3-Dihydro-4-pyridone skeleton is an important building block in organic synthesis because it features several reaction sites with nucleophilic or electrophilic properties. Herein, we disclose a method for its formation by intramolecular cyclization of ester-tethered enaminones, which can easily be synthesized from readily available materials, such as amines, activated alkynes, and activated alkenes. 2,3-Dihydro-4-pyridones have been isolated in 41-90% yields. We also demonstrate the transformation of these heterocycles into another important class of compounds, 4-pyridones, by utilizing 2,3,5,6-tetrachloro--benzoquinone (chloranil) as an oxidizing agent. The latter products were isolated in 65-94% yields.