First enantiomerically pure C70-adducts with a non-inherently chiral addition pattern

Abstract

By addition of an enantiomerically pure nitrile oxide to C₇₀, four chiral isoxazolo[70]fullerene isomers were prepared and isolated in pure state: two constitutional isomers resulting from addition to one of the bonds radiating from the polar pentagons, and a constitutionally different pair of diastereoisomers resulting from addition to a hexagon–hexagon fusion site parallel to the equator of the fullerene. After elimination of the stereogenic center from the side chain, the former two adducts become achiral, while the latter two are separately transformed into enantiomeric fullerene derivatives with a non-inherently chiral addition pattern as sole stereogenic element. In the present work, chiral [70]fullerene derivatives with a non-inherently chiral functionalisation pattern were isolated in enantiomerically pure form for the first time. Their absolute configuration was assigned based on the good agreement between experimental circular dichroism (CD) data and CD spectra calculated using the ZINDO method.