Synthesis of Dendritic Branches with Peripheral Fullerene Subunits
Highly soluble dendritic branches with two, four, eight or 16 methanofullerene subunits at their peripheries and carboxylic acid functions at their focal points have been prepared by a convergent approach. Starting from a methanofullerene derivative possessing a tert-butyl ester function, the successive dendrimer generations were obtained by repetition of a reaction sequence involving cleavage of the tert-butyl ester moiety under acidic conditions, followed by a DCC-mediated esterification reaction with an A2B building block possessing two benzylic alcohol functions and a tert-butyl ester group. This repetitive synthetic sequence is very efficient and allowed the dendritic growth up to the fifth-generation derivative, containing 16 peripheral fullerene subunits. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)