Asymmetric bisosmylation of C[sub 60]. Novel chiral [pi]-systems

We report the asymmetric bisosmylation of C[sub 60], yielding enantiomerically enriched chiral (C[sub 2]) isomers, and an analysis of the novel chiral band-shaped [pi]-systems of these fullerene derivatives by circular dichroism (CD) spectroscopy. The regiochemistry and stereochemistry of the bisosmylation of C[sub 60] are affected by the ligands on osmium. Both osmyl groups add to the fusion of two six-membered rings, with the first group directing the second oxidation away from the proximate hemisphere. The tendency of the second osmyl group to add away from the first is only marginally increased by bulkier ligands on osmium. The chemistry, demonstrating enantioselective reactions on a fullerene surface, and the osmylation of C[sub 70], demonstrating the regioselective osmylation of a higher fullerene, provided the basis for the kinetic resolution of the chiral fullerenes C[sub 76]. C[sub 78], and C[sub 84] by asymmetric osmylation. 12 refs., 2 figs., 1 tab.