FeCl₃-Mediated Oxidative Spirocyclization of Difluorenylidene Diarylethanes Leading to Dispiro[fluorene-9,5′-indeno[2,1-a]indene-10′,9″-fluorene]s

A novel FeCl₃-mediated oxidative spirocyclization for construction of a new class of di-spirolinked π-conjugated molecules, dispiro[fluorene-9,5′-indeno[2,1-a]indene-10′,9″-fluorene]s (DSFIIFs), has been reported. The combination of FeCl₃ with FeO(OH) triggered an unprecedented double one-electron oxidation of difluorenylidene diarylethanes to afford the corresponding dispirocycles in high yields. The highest fluorescence quantum yield was up to 0.94 in solution. This protocol is also applicable to the synthesis of the non-spirolinked dihydroindenoindenes.