Biscycloaddition to [60]Fullerene: Regioselectivity and Its Control with Templates

Compared to [60]fullerene monoadducts, there have been far fewer examples of the investigation of bisadducts, mainly due to the difficulties in their isolation and characterization. Unless appropriate templates are employed, bisadditions generally proceed with low regioselectivity, resulting in the formation of complex regioisomeric mixtures. This account deals with the regioselectivity in typical bisadditions in the absence of templates and the spectroscopic features available for the characterization of the bisadducts produced. The observed regioselectivity can be reasonably explained by a combination of the steric reasons and the coefficients of frontier orbitals in the corresponding monoadducts. Although it depends on the reactive species whether HOMO or LUMO is involved, e isomer is always preferable. In order to accomplish regioselective synthesis of bisadducts, several research groups have developed a synthetic methodology by using tethers as covalent templates. This account describes the regioselectivity in bisadditions accomplished by templating tethers, mainly focusing on Diels-Alder reactions.