Synthesis of Substituted Phenanthrene by Iron(III)-Catalyzed Intramolecular Alkyne–Carbonyl Metathesis

An efficient synthesis of functionalized phenanthrenes has been developed for the first time involving an iron(III)-catalyzed intramolecular coupling of 2'-alkynyl-biphenyl-2-carbaldehydes. A broad range of functionalized phenanthrene derivatives could be obtained in the present method in moderate to good yields with high chemo- and regioselectivity. This transformation can also be applied to the synthesis of an angularly fused tetracyclic compound. This method offers several advantages such as high selectivity, mild reaction conditions, and easy availability of starting materials.