Expeditious Synthesis of Phenanthrenes via CuBr2-Catalyzed Coupling of Terminal Alkynes and N-Tosylhydrazones Derived from O-Formyl Biphenyls

A new method for the synthesis of phenanthrenes via ligand-free CuBr2-catalyzed coupling/cyclization of terminal alkynes with N-tosylhydrazones derived from o-formyl biphenyls has been developed. This new synthesis has wide range of functional group compatibility.