Regiochemistry of [70]fullerene:: Preparation of C70(OOtBu)n, (n = 2, 4, 6, 8, 10) through both equatorial and cyclopentadienyl addition modes

[GRAPHICS] tert-Butylperoxy radicals add to [70]fullerene to form a mixture of adducts C-70((OOBu)-Bu-t)(n) (n = 2, 4, 6, 8, 10). Four isomers were isolated for the bis-adduct with the two tert-butylperoxo groups attached at 1,2-, 5,6-, 7,23-, and 2,5-positions, respectively. Two isomers were isolated for the tetrakis-adduct with the tert-butylperoxo groups located along the equator in C-s symmetry and on the side in C-1 symmetry, respectively. Similarly, two isomers were isolated for the hexakis-adducts with a structure related to the tetrakis-adducts, one of which has the cyclopentadienyl substructure. No isomer was detected for the octakis- and decakis-adducts. The C-s-symmetric octakis- and C-2-symmetric decakis-adducts have all the tert-butylperoxo groups located along the equator. The decakis-adduct is the major product under optimized conditions. The compounds were characterized by their spectroscopic data. Chemical correlation through further addition of tert-butylperoxy radicals to isolated pure derivatives confirmed the structure assignment. Mechanisms of the tert-butylperoxy radical addition to C-70 follow two pathways: equatorial addition along the belt and cyclopentadienyl addition on the side.