Ring Expansion of the Fullerene Core by Highly Regioselective Formation of Diazafulleroids

Fullerenes with enlarged openings such as diazafulleroid 1 are obtained by twofold addition of azides to C60. Even after cleavage of the two 5–6 bonds and introduction of the imino bridges, the π-electron system of C60 remains intact. Compound 1 contains three seven-membered rings and one eleven-membered ring, and may hold the key to the synthesis of endohedral fullerenes under mild conditions.