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.