Palladium-Catalyzed C-H Arylation/Arene Dearomatization Domino Reaction: Expeditious Access to Spiro[4,5]fluorenes.

A palladium-catalyzed C-H arylation/arene dearomatization of α-aryl-β-naphthol with o -dihalobenzenes was realized in a redox-neutral manner. This bimolecular domino reaction was initiated by an in situ-formed Pd(II) species generated from the dihalobenzene, followed by phenolic-group-directed C-H activation, biaryl cross-coupling, and naphthol dearomatization, thus rendering the rapid assembly of a class of spiro[4,5]fluorenes in high yields with good chemoselectivity. Remarkably, malononitrile-derived spirofluorene 6 was found to exhibit mechanoresponsive luminescence, which can be applied to optical memory devices.