The First Fulleropyrrolidine Derivative of Sc3N@C80:  Pronounced Chemical Shift Differences of the Geminal Protons on the Pyrrolidine Ring

The first pyrrolidine adduct on Sc3N@C80 was synthesized and fully characterized. Addition of the N-ethylazomethine ylide occurs regioselectively on a [5,6] double bond on the surface of the icosahedral symmetry Sc3N@C80, exactly in the same position as that described previously for a Diels−Alder adduct of the same compound. 11a,b This addition pattern results in symmetric pyrrolidine carbons and unsymmetric geminal hydrogens on the pyrrolidine ring, as confirmed by 1H and 13C NMR spectroscopy, especially by HMQC. The shielding environment experienced by these geminal hydrogens differs by 1.26 ppm, indicative of pronounced ring current effects on the surface of this endohedral fullerene. This represents the first fully characterized pyrrolidine adduct on an endohedral metallofullerene.