Upon the first subsequent functionalizations, the rotation of the fullerene in the complex is impeded, thus effectively deactivating reactive sites masked by the host. For the synthesis of the tetrakis-diethylmalonate-C60 adduct with 4 equiv. of diethyl bromomalonate, the ite calculated is 99% from rnormal and rexp of 20% and 99%, respectively. It is noteworthy that this shadow mask strategy not only allows iteroselective control but also regioselective control of the products. In the case exemplified in Figure , the shadow mask permits only the formation of the tetrakis-e,e,e,e-adduct as ultimate product but other shadow masks were used to access different regio-and iteroselectivities. Figure . Regio-and iteroselective tetra-functionalization of fullerene C60 via a shadow-mask strategy. There are 30 equally reactive sites on the starting C60.