Direct synthesis of spirobifluorenes by formal dehydrative coupling of biaryls and fluorenones

A Tf₂O-mediated, direct dehydrative coupling of (hetero)biaryls and fluorenones proceeds to form the corresponding spirobifluorenes in good to high yields. The reaction system allows the relatively simple nonhalogenated and nonmetalated starting substrates to be directly adopted in the spirocyclisation reaction. In addition, the double cyclisation reaction is easily performed, giving the highly spiro-conjugated aromatic compounds of potent interest in materials chemistry. The preliminary optoelectronic properties of some newly synthesised compounds are also demonstrated.