Pd-catalyzed synthesis of 9,9-bifluorenylidene derivatives via dual C-H activation of bis-biaryl alkynes

We report a novel Pd-catalyzed alkyne-directed dual C-H activation of bis-biaryl alkynes, which produced important and useful products, 9,9-bifluorenylidene (9,9BF) derivatives, in high yields with a broad range of functional group compatibility. The combination of the PdCl₂ catalyst with the MnO₂ oxidant and PivOH additive is vital for realization of the present catalytic transformation. Mechanistic evidence suggests that this intramolecular arene/alkyne annulation may take place through unusual dual C-H activation followed by annulation with alkynes.