Expeditious Preparation of Open‐Cage Fullerenes by Rhodium(I)‐Catalyzed [2+2+2] Cycloaddition of Diynes and C60: An Experimental and Theoretical Study

AbstractA novel methodology to transform C60 into a variety of open‐cage fullerene derivatives by employing rhodium(I) catalysis has been developed. This transformation encompasses a partially intermolecular [2+2+2] cycloaddition reaction between diynes 1 and C60 to deliver a cyclohexadiene‐fused fullerene, which concomitantly undergoes a formal [4+4]/retro‐[2+2+2] rearrangement to deliver open‐cage fullerenes 2. Most notably, this process occurs without the need of photoexcitation. The complete mechanism of this transformation has been rationalized by DFT calculations, which indicate that, after [2+2+2] cycloaddition, the cyclohexadiene‐fused intermediate evolves into the final product through a Rh‐catalyzed di‐π‐methane rearrangement followed by a retro‐[2+2+2] cycloaddition. The obtained open‐cage fullerenes can be derivatized by Suzuki–Miyaura cross‐coupling or subjected to ring expansion to deliver a 12‐membered ring orifice in the fullerene structure. Overall, the methodology presented constitutes a straightforward entry to functional open‐cage C60 fullerene derivatives by employing catalytic methods.