Synthesis of Phenanthrenes and Naphthoquinone Fused Benzoxepines via Hauser–Kraus Annulation of Sulfonylphthalide with Morita–Baylis–Hillman Adducts of Nitroalkenes

Abstract

The Hauser–Kraus annulation of sulfonylphthalide with Morita–Baylis–Hillman (MBH) adducts of nitroalkenes provides access to phenanthrenes and naphthoquinone fused dihydrobenzoxepines. The H–K annulation results in naphthoquinones bearing a key alcohol group in protected form, which leads to naphthoquinone fused tetracyclic oxepines upon reaction with formaldehyde. These alcohols yield functionalized phenanthrenes via oxidation and [3 + 3] annulation with β-ketoesters.