The design and synthesis of a new family of siderophores based on cyclotriveratrylene is described. The ligands consist of a C3-cyclotriveratrylene unit provided with three arms (spacers) ending with hydroxamate, catecholate, bipyridine, or iminopyridine units suitable for the octahedral coordination of transition metals and particularly for the complexation of iron(II) and iron(III).
Regioselective one-step synthesis of trans-3,trans-3,trans-3 and e,e,e [60]fullerene tris-adducts directed by a C3-symmetrical cyclotriveratrylene tether
The first covalent cyclotriveratrylene (CTV)–C60 adducts were prepared by the tether-directed Bingel reaction, which gave the two C3-symmetrical trans-3,trans-3,trans-3 and e,e,e tris-adducts with a high degree of regioselectivity.
Regioselectivity in Tether-Directed Remote Functionalization - The Addition of a Cyclotriveratrylene-Based Trimalonate to C60 Revisited
作者:Agnieszka Kraszewska、Pablo Rivera-Fuentes、Gwénaël Rapenne、Jeanne Crassous、Ana G. Petrovic、José Lorenzo Alonso-Gómez、Elisa Huerta、François Diederich、Carlo Thilgen
DOI:10.1002/ejoc.201000396
日期:——
The Bingel addition of a trimalonate derived from a chiral, cyclotriveratrylene (CTV)-based tripodal tether to C60 was reinvestigated. The present use of enantiomerically pure (P)and (M)-configured CTV units in the tether allowed the isolation of a total of four enantiomerically pure C3-symmetric trisadducts of [60]fullerene (two from each CTV enantiomer). With the support of NMR and UV/Vis spectroscopy
The C-3-symmetrical [60]fullerene-cyclotriveratrylene (CTV) tris-adducts (+/-)-1 (with a trans-3,trans-3,trans-3 addition pattern) and (+/-)-2 (with an e,e,e addition pattern) were prepared in 11 and 9% yield, respectively, by the regio- and diastereoselective tether-directed Bingel reaction of C-60 with the tris-malonate-appended CTV derivative (+/-)-3 (Scheme). This is the first example for tris-adduct formation by a one-step tether-directed Bingel 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 (+/-)-1 and (+/-)-2 are by 100 mV more negative than those of their corresponding tris[bis(ethoxycarbonyl)methano][60]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 topological meso-form is also presented (Fig. 8).