Structural effects on thermal rearrangement of fulleroids to methanofullerenes. The prominent role of cyclopropyl vs aryl substituent

The kinetics of the thermal rearrangement of a series of novel cyclopropyl-substituted [5,6] open fulleroids to the [6,6] closed methanofullerenes have been investigated in comparison with the aryl-substituted homologues. The cyclopropyl group markedly accelerated the rates due to the stereoelectronically favorable pi-conjugative effects in the radical-like [1,5] shift of the transient [5,6] closed isomers, overriding the geometrically constrained aryl group.