Synthesis of Aminophenanthrenes and Benzoquinolines via Hauser–Kraus Annulation of Sulfonyl Phthalide with Rauhut–Currier Adducts of Nitroalkenes

Abstract

The Hauser-Kraus reaction of sulfonyl phthalide with nitroalkene derivatives provides access to aminophenanthrenes, including phenanthrene-substituted amino acids and benzoquinolines. The intermediate quinones bearing a key ketoalkyl moiety undergoes facile intramolecular enamine cyclization. Interestingly, enamines derived from primary and secondary amines undergo cyclization via C-centered nucleophilic attack to provide aminophenanthrenes, whereas those derived from ammonia undergo cyclization via N-centered nucleophilic attack leading to benzoquinolines. A one-pot protocol for the direct transformation of phthalides and nitroalkene derivatives to aminophenanthrenes and benzoquinolines has also been developed.