Method for the Synthesis of Amine-Functionalized Fullerenes Involving SET-Promoted Photoaddition Reactions of α-Silylamines

A novel method for the preparation of structurally diverse fullerene derivatives, which relies on the use of single electron transfer (SET)-promoted photochemical reactions between fullerene C-60 and alpha-trimethylsilylamines, has been developed. Photoirradiation of 10% EtOH toluene solutions containing C-60 and alpha-silylamines leads to high-yielding, regioselective formation of 1,2-adducts that arise through a pathway in which sequential SET-desilylation occurs to generate alpha-amino and C-60 anion radical pair intermediates, which undergo C-C bond formation. Protonation of generated alpha-aminofullerene anions gives rise to formation of monoaddition products that possess functionalized alpha-aminomethyl-substituted 1,2-dihydrofullerene structures. Observations made in this effort show that the use of EtOH in the solvent mixture is critical for efficient photoproduct formation. In contrast to typical thermal and photochemical strategies devised previously for the preparation of fullerene derivatives, the new photochemical approach takes place under mild conditions and does not require the use of excess amounts of substrates. Thus, the method developed in this study could broaden the scope of fullerene chemistry by providing a simple photochemical strategy for large-scale preparation of highly substituted fullerene derivatives. Finally, the alpha-aminomethyl-substituted 1,2-dihydrofullerene photoadducts are observed to undergo photoinduced fragmentation reactions to produce C-60 and the corresponding N-methylamines.