Efficient palladium-catalyzed C(sp2)–H activation towards the synthesis of fluorenes

A facile protocol for the synthesis of fluorene derivatives has been developed through palladium-catalyzed cyclization of 2′-halo-diarylmethanes via activation of arylic C–H bonds. The reactions occurred smoothly and allowed both electron-rich and electron-deficient substrates to convert into their corresponding fluorenes in good to excellent yields. Studies revealed that this Pd-catalyzed cyclization was also available for the substrates of 2′-chloro-diarylmethanes and no catalyst poisoning occurred for 2′-iodo-diphenylmethane.