PCy₃‐Catalyzed Ring Expansion of Aziridinofullerenes with CO₂ and Aryl Isocyanates: Evidence for a Two Consecutive Nucleophilic Substitution Pathway on the Fullerene Cage

A PCy3-catalyzed ring-expansion reaction of aziridine-fused fullerenes (aziridinofullerenes) through the insertion of CO2 and aryl isocyanates is disclosed. The reaction allows for CO2 fixation by aziridinofullerenes, producing oxazolidinone-fused fullerenes (oxazolidinofullerenes) in high yields, whereas treatment with aryl isocyanates led to a new fullerene family-imidazolidinone-fused fullerenes (imidazolidinofullerenes)-in good to high yields. Furthermore, a mechanistically related unprecedented fullerenyl phosphonium salt was successfully isolated. Using the isolated salt, mechanistic studies were also investigated.