Addition of Azomethine Ylides: Fulleropyrrolidines

Although extensively studied in the last decade, the fullerenes continue to be a most exciting and promising challenge in current chemical research. After a first phase characterized by theoretical, physical and physicochemical studies, a well established “organic chemistry of the fullerenes” developed in a very rapid progression to the point that, currently, a wide variety of functionalized fullerenes are available through simple and accessible synthetic routes [1,2]. Among the many reactions that were successfully developed, the 1,3-dipolar cycloaddition of azomethine ylides provides a valuable synthetic procedure for the preparation of functionalized fullerenes [3–5]. The product of the reaction, named fulleropyrrolidine because a pyrrolidine ring is fused to a ring-junction of a fullerene, retains the basic properties of the parent fullerene and can be used as a starting material for further functionalization. Whereas monofunctionalization of the highly symmetrical [60]fullerene affords a single fulleropyrrolidine, the same addition to [70]fullerene [6, 7] gives rise to mixtures of regioisomers. For this reason, current fulleropyrrolidine syntheses are predominantly carried out using [60]fullerene.