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

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.