Internal Motions in a Fulleropyrrolidine Tertiary Amide with Axial Chirality

The kinetic parameters for topomerization around the N−CO bond and enantiomerization around the C−CO bond in N-1-naphthoyl fulleropyrrolidine 1 and N-1-naphthoyl pyrrolidine 2 have been determined by dynamic NMR (line shape simulation and selective inversion transfer). The ΔS^≠ values are negligible. The ΔH^# value for topomerization of 1 is smaller with respect to that of 2 by 4.3 kcal mol^-1 (explained by the electron-withdrawing effect of fullerene) and the value for enantiomerization is greater by 1.4 kcal mol^-1 (explained by the greater rigidity of the fulleropyrrolidine ring, as confirmed by ab initio analyses).