Expeditious Preparation of Open‐Cage Fullerenes by Rhodium(I)‐Catalyzed [2+2+2] Cycloaddition of Diynes and C 60 : An Experimental and Theoretical Study

A novel methodology to transform C 60 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 C 60 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 C 60 fullerene derivatives by employing catalytic methods.