Based on the conditions for the formation of stable nitroxides, that is, oxidation of a secondary amine which has no α-H, 2-aminoisobutyric acid and diketone were used to react with C60 via 1,3-dipolar cycloaddition to yield fulleropyrrolidine. It is proposed that the compound of bis-fulleropyrrolidines 1 can be synthesized. Furthermore, the bis-fulleropyrrolidines can be oxidized to give a stable bis-nitroxide based on fullerene. However, the results have pointed out that the reactions with C60 only afforded monoadducts 2a after decarboxylation and dehydration perhaps due to steric hindrance.
Shi, Z., Li, Y., Xu, J., Ge, Z., & Zhu, D. (2000). Covalently linked [60,70] fullerenes-nitroxide unit for synthesis and characterization. Journal of Physics and Chemistry of Solids, 61(7), 1095–1099. https://doi.org/10.1016/S0022-3697(99)00367-4