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 CuBr(2)-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.