Anion-π Catalysis on Fullerenes

Anion-pi interactions on fullerenes are about as poorly explored as the use of fullerenes in catalysis. However, strong exchange-correlation contributions and the localized pi holes on their surface promise unique selectivities. To elaborate on this promise, tertiary amines are attached nearby. Dependent on their positioning, the resulting stabilization of anionic transition states on fullerenes is shown to accelerate disfavored enolate addition and exo Diels-Alder reactions enantioselectively. The found selectivities are consistent with computational simulations, particularly concerning the discrimination of differently planarized and charge-delocalized enolate tautomers by anion-pi interactions. Enolate-pi interactions on fullerenes are much shorter than standard pi-pi interactions and anion-pi interactions on planar surfaces, and alternative cation-pi interactions are not observed. These findings open new perspectives with regard to anion-pi interactions in general and the use of carbon allotropes in catalysis.