Palladium-Catalyzed Synthesis of Substituted Phenanthrenes via a C–H Annulation of 2-Biaryl Triflates with Alkynes

A new palladium-catalyzed efficient method for the synthesis of substituted 9,10-phenanthrenes from 2-biaryl triflates with alkynes has been developed. This method provides a great opportunity to prepare various symmetrical and unsymmetrical phenanthrene derivatives in good yields. This reaction proceeds via C-OTf bond cleavage and alkyne insertion followed by C-H annulation.