Remote functionalization of C60 with enantiomerically pure cyclo-[2]-malonate tethers bearing C12 and C14 spacers: Synthetic access to bisadducts of C60 with the inherently chiral trans-3 addition pattern

Abstract

In this Article, we describe the synthesis of two optically pure diols bearing a 1,2-diol moiety masked as an isopropylidene acetal group and long alkyl chains comprised of 12 and 14 carbon atoms, respectively. The synthetic methodology that was developed offers a general way for the synthesis of optically pure diols with long alkyl chains. Diols (-)-4 and (-)-9 were subjected to a condensation reaction with malonyl dichloride to afford two cyclo-[2]-malonate tethers that were separated by column chromatography in optically pure form. The bismalonates (-)-4b and (-)-9b proved to be excellent tethers for the regioselective Bingel functionalization of C60, furnishing in a regioselective manner the corresponding f,sC and f,sA trans-3 bisadducts with low diastereoselectivity but in very good to excellent total yields. In both cases, the formed trans-3 bisadducts were isolated in pure form by simple column chromatography and were fully characterized. The successful acetal deprotection of the synthesized trans-3 bisadducts afforded quantitatively the corresponding polyalcohols, which represent novel chiral fullerene compounds equipped with glycol moieties. © 2013 American Chemical Society.