Synthesis of a Dihydroxylated Open-Cage [70]Fullerene by a Reductive Ring-Closure Reaction.

Upon heating an open-cage diketo C70 derivative in carbon disulfide, the 1,2-dihydroxylated compound was unprecedentedly formed via a reductive ring-closure reaction. The crystallographic analysis of the diketo derivative revealed a benzenoid character on its orifice which suppresses the nucleophilic addition. The 1,2-dihydroxylated derivative could be transformed into a 1,4-substituted one by an acid-catalyzed reaction. The observed unique reactivity of the diketo derivative is inherently different from those of structurally related C70 isomers as well as a C60 analogue.