Preparation of a 12-Membered Open-Cage Fullerendione through Silane/Borane-Promoted Formation of Ketal Moieties and Oxidation of a Vicinal Fullerendiol

[60]Fullerene mixed peroxide C60 (OH)(Cl)(OOtBu) reacts with PhMe2SiH/B(C6F5)3 to give oxahomofullerene. Mechanistic investigation indicates that the hydroxyl group in the central pentagon ring is essential to convert the tert-butylperoxo group into a ketal moiety. Migration of the silyl group and transformation of the siloxy group into a phenyl group are observed in the deprotection of the fullerene bound siloxy group. A 12-membered open-cage fullerendione was obtained through oxidation of a [6,6]-fullerendiol. This orifice could be closed to form ketal/hemiketal moieties by BF3-catalyzed reaction with methanol. All of the new fullerene derivatives were characterized by spectroscopic data, and structure of the open-cage fullerendione was also confirmed by single-crystal X-ray analysis.