Regioselective one-step synthesis and topological chirality of trans-3, trans-3,trans-3 and e,e,e [60]fullerene-cyclotriveratrylene tris-adducts: Discussion on a topological meso-form

The C-3-symmetrical [60]fullerene-cyclotriveratrylene (CTV) tris-adducts (/-)-1 (with a trans-3,trans-3,trans-3 addition pattern) and (+/-)-2 (with a n e,e,e addition pattern) were prepared in 11 and 9% yield, respectively, b y the regio- and diastereoselective tether-directed Bingel reaction of C-60 with the tris-malonate-appended CTV derivative (+/-)-3 (Scheme). This is t he first example for tris-adduct formation by a one-step tether-directed Bi ngel addition. Interchromophoric interactions between the electron-rich CTV cap and the electron-attracting fullerene moiety have a profound effect on the electrochemical behavior of the C-sphere (Fig. 4 and Table 1). The ful lerene-centered first reduction potentials in compounds (+/-)-1 and (+/-)-2 are by 100 mV more negative than those of their corresponding tris[bis(eth oxycarbonyl)methano][60]fullerene analogs that lack the CTV cap. A particul ar interest in (+/-)-1 and (+/-)-2 arises from the topological chirality of these molecules. A complete topology study is presented, leading to the co nclusion that the four possible classical stereoisomers of the e,e,e regioi somer are topologically different, and, therefore, there exist four differe nt topological stereoisomers (Fig. 6). Interestingly, in the case of the tr ans-3,trans-3,trans-3 tris-adduct, there are four classical stereoisomers b ut only two topological stereoisomers (Fig. 7). An example of a target mole cule representing a topological meso-form is also presented (Fig. 8).