Inverse Electron Demand Diels-Alder Reaction on MN@C (M=Lu, Sc): Reactivity and Reversibility Enable Chemical Separation of Metallofullerenes.

Endohedral metallofullerenes are chemically more inert compared to empty fullerenes, primarily due to their intramolecular electron transfer. In this work, we report an inverse electron demand Diels-Alder (IEDDA) reaction on MN@C (M=Lu, Sc), where they show significantly higher reactivity than empty fullerenes. The molecular structures of the [4+2] cycloadducts were unambiguously characterized. Moreover, the cycloadducts can fully revert to pristine MN@C via retro-cycloaddition upon thermal treatment. With the unusual reactivity and reversibility, the IEDDA reaction enables an effective separation approach for metallofullerenes from their soot extracts, opening path to efficient and economical scale-up synthesis of metallofullerenes in laboratory and industrial settings.