Spirocyclic Dihydropyridines by Electrophile-Induced Dearomatizing Cyclization of N‑Alkenyl Pyridinecarboxamides

On treatment with acylating or sulfonylating agents, N-alkenyl pyridine carboxamides (N-pyridinecarbonyl enamines) undergo a dearomatizing cyclization initiated by pyridine acylation and followed by intramolecular trapping of the resulting pyridinium cation. The products are spirocyclic dihydropyridines which may be further elaborated to spirocyclic heterocycles with drug-like features.