Regioselective One-Step Synthesis and Topological Chirality of trans-3, trans-3,trans-3 and e,e,e Fullerene-Cyclotriveratrylene Tris-adducts: Discussion on a Topological meso-Form
One-Step Synthesis, Topological Chirality
The C3-symmetrical fullerene-cyclotriveratrylene (CTV) tris-adducts (±)-1 (with a trans-3,trans-3,trans-3 addition pattern) and (±)-2 (with ane,e,e addition pattern) were prepared in 11 and 9% yield, respectively, by the regio- and diastereoselective tether-directed Bingel reaction of C60with the tris-malonate-appended CTV derivative (±)-3 (Scheme). This is the first example for tris-adduct formation by a one-step tether-directedBingel 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 fullerene-centered first reduction potentials in compounds (±)-1and (±)-2 are by 100 mV more negative than those of their corresponding tris[bis(ethoxycarbonyl)methano]fullerene analogs that lack the CTV cap. A particular interest in (±)-1 and (±)-2 arises from the topological chirality of these molecules. A complete topology study is presented, leading to the conclusion that the four possible classical stereoisomers of the e,e,e regioisomer are topologically different, and, therefore, there exist four different topological stereoisomers (Fig. 6). Interestingly, in the case of the trans-3,trans-3,trans-3 tris-adduct, there are four classical stereoisomers but only two topological stereoisomers (Fig. 7). An example of a target molecule representing a topologicalmeso-form is also presented (Fig. 8).
© 2000 Neue Schweizerische Chemische Gesellschaft, Switzerland
Rapenne, G., Crassous, J., Echegoyen, Lourdes E., Echegoyen, L., Flapan, E. and Diederich, F. (2000), Regioselective One-Step Synthesis and Topological Chirality of trans-3, trans-3,trans-3 and e,e,e Fullerene-Cyclotriveratrylene Tris-adducts: Discussion on a Topological meso-Form. HCA, 83: 1209–1223. doi: 10.1002/1522-2675(20000607)83:6<1209::AID-HLCA1209>3.0.CO;2-Y