Pentamethylcyclopentadiene adducts of [60]- and [70]- fullerene

Abstract

Pentamethylcyclopentadiene reacts with [60]- and [70]-fullerene to form Diels–Alder monoadducts, characterised by ¹H and ¹³C NMR spectroscopy, in which the methyl group attached to the single carbon bridge points away from the cage. Cycloaddition to [70]fullerene takes place across the 1,9-bond adjacent to the pentagonal cap. The pentamethyl adducts are less prone to undergo the retro Diels–Alder reaction than their non-methylated counterparts. The ¹H NMR spectra provide further confirmation that [70]fullerene is less electron withdrawing than [60]fullerene.