Novel base-catalysed formation of benzo[b]furano[60]- and -[70]fullerenes

Reaction of C60Cl6 with phenol in the presence of aq. KOH and under nitrogen, produces benzo[b]furano[2',3' : 1,2][60]fullerene arising from substitution/elimination occurring across the 1,2-positions of the hexachloro precursor. Use of either 4-fluorophenol or 4-methoxyphenol produces the corresponding fluoro- and methoxy-substituted derivatives. Reaction with an excess of phenolic reagent results in nucleophilic replacement of some of the other chloro addends in the precursor by phenoxy groups, which may also participate in oxidative ring closure. C70Cl10 reacts with phenol in the presence of aq. KOH to give benzo[b]furano[2',3' : 7,8][70]fullerene. The corresponding reaction of aniline with C60Cl6 produces derivatives of benzo[b]pyrrolo[2',3' : 1,2][60]fullerene, but thiophenol does not react. Removal of eclipsing steric hindrance accounts for the ready ring-closure formation of the cycloadducts across bonds containing adjacent chlorines.