The bis-adducts of the [5,6]-fullerene C60 and anthracene

Five regioisomeric bis-adducts of anthracene and the [5,6]-fullerene C60 were prepared by Diels–Alder reactions of the monoadduct in solution. The structures of the five bis-adducts were determined by spectroscopic and/or crystallographic means and were found to be the five (out of eight) possible constitutional isomers, in which the two anthracene addends do not occupy the same hemisphere of the fullerene core. The regioselectivity of the formation of bis-adducts by [4+2]-cycloaddition reactions of anthracene and C60 differs from that of the nucleophilic cyclopropanation of C60 or of the dipolar [3+2]-cycloaddition with azomethine ylides.