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

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.