Journal of the American Chemical Society, Vol.138, No.27, 8364-8367, 2016
Fused Dibenzo[a,m]rubicene: A New Bowl-Shaped Subunit of C-70 Containing Two Pentagons
Total synthetic approaches of fullerenes are the holy grail for organic chemistry. So far, the main attempts have focused on the synthesis of the buckmin-sterfullerene C-60. In contrast, access to subunits of the homologue C-70 remains challenging. Here, we demonstrate an efficient bottom-up strategy toward a novel bowl-shaped polycyclic aromatic hydrocarbons (PAH) C34 with two pentagons. This PAH represents a subunit for C-70 and of other higher fullerenes. The bowl-shaped structure was unambiguously determined by X-ray crystallography. A bowl-to-bowl inversion for a C-70 fragment in solution was investigated by dynamic NMR analysis, showing a bowl-to-bowl inversion energy (Delta G double dagger) of 16.7 kcal mol(-1), which is further corroborated by DFT calculations.