Decarboxylation of Aza-Annulation Products as a Synthetic Route to 3-Pyrrolin-2-ones and 1,2,3,4-Tetrahydropyridin-2-ones.

Aza-annulation of enamines derived from β-ketoesters with maleic and itaconic anhydrides proceeds with excellent diastereoselectivity to provide functionalized γ- and δ-lactams. Further hydrolysis of the aza-annulation products resulted in dicarboxylic acids that underwent spontaneous decarboxylation under ambient conditions. The decarboxylation of β-γ unsaturated carboxylic acids with an electron-rich enamide C═C bond proceeds with the migration of the C═C bond and serves as a practical synthetic entry into 3-pyrrolin-2-ones and 1,2,3,4-tetrahydropyridin-2-ones.