Enantioselective Synthesis of Medium‐Sized Lactams via Chiral α,β‐Unsaturated Acylammonium Salts

Medium‐sized lactams are important structural motifs found in a variety of bioactive compounds and natural products but are challenging to prepare, especially in optically active form. A Michael addition/proton transfer/lactamization organocascade process is described that delivers medium‐sized lactams, including azepanones, benzazepinones, azocanones, and benzazocinones, in high enantiopurity through the intermediacy of chiral α,β‐unsaturated acylammonium salts. An unexpected indoline synthesis was also uncovered, and the benzazocinone skeleton was transformed into other complex heterocyclic derivatives, including spiroglutarimides, isoquinolinones, and δ‐lactones. Eine Reaktionskaskade aus Michael‐Addition, Protonentransfer und Lactamisierung ergab über α,β‐ungesättigte Acylammonium‐Intermediate verschiedene Lactame – z. B. Azepanone, Benzazepinone, Azocanone und Benzazocinone – mit hoher Enantioselektivität. Die Benzazocinone wurden in Spiroglutarimide und Isochinoline überführt. Zudem wurde durch das Abfangen eines tetraedrischen Intermediats ein Indolin erzeugt.