Regioselectivity in Tether‐Directed Remote Functionalization – The Addition of a Cyclotriveratrylene‐Based Trimalonate to C₆₀ Revisited

Abstract

The Bingel addition of a trimalonate derived from a chiral, cyclotriveratrylene (CTV)-based tripodal tether to C 60 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 C 3 -symmetric trisadducts of [60]fullerene (two from each CTV enantiomer). With the support of NMR and UV/Vis spectroscopy, electronic (ECD) and vibrational (VCD) circular dichroism spectroscopic analysis (comparison to ECD data of known compounds and to ECD and VCD data calculated by TD-DFT or

Prediction of the experimental regioselectivity of C60 fullerene bis‐adducts

“…A side product, cis‐3 (12.9%), was predicted to be formed, but this is not observed experimentally . Among the possible glycinate–glycinate (5mem5mem) products, the trans‐4 regioisomer was predicted to be the most stable (48.2%) in accordance with the experimental data . Nonetheless, the trans‐3 (27.1%) and e‐face (24.6%) were also predicted as possible products even though the secondary experimental product is the cis‐3 bis‐adduct.…”

“…This is indeed true not only for the second but for successive additions to the fullerene core . However, if the second addend is carried by a tether already attached to the fullerene cage, then the kinetic regioisomer is not necessarily obtained …”

A study towards the regioselective synthesis of the e,e,e trisadduct of C60 via the [4+2] Diels-Alder reaction with tethers bearing ortho-quinodimethane precursors

“…The tether-directed remote functionalization method has been successfully applied for the synthesis of C 3 -symmetrical trisadducts of C 60 by the groups of Diederich, 6 Hirsch, [7][8][9][10][11][12] Nierengarten 13-15 and ours. [16][17][18] Opened-and closed-structure tethers equipped with three malonate groups were utilized for this purpose and all possible C 3 -symmetrical addition patterns have been accessed except the cis-1,cis-1,cis-1 (all-cis-1) which is not energetically favored owing to the steric hindrance of the addends.…”

“…[16][17][18] Opened-and closed-structure tethers equipped with three malonate groups were utilized for this purpose and all possible C 3 -symmetrical addition patterns have been accessed except the cis-1,cis-1,cis-1 (all-cis-1) which is not energetically favored owing to the steric hindrance of the addends. In all these cases, the covalent functionalization was performed by the Bingel cyclopropanation of the reactive [6,6]-double bonds of C 60 , a widely used derivatization method in fullerene chemistry. A disadvantage of the Bingel reaction is the reversibility under reductive (chemical and electrochemical) conditions [19][20][21] [Scheme 2, (a)], a limiting factor for possible applications of C 60 trisadducts in electron transfer processes mimicking the photosynthetic system.…”

The intermolecular anthracene-transfer in a regiospecific antipodal C60 difunctionalization

“…49,50 The molecular features of the fullerenes as polyunsaturated spherical carbon compounds have attracted particular attention to the synthesis of di-and multi-functionalized derivatives with high regio-and stereo-control. 8,[51][52][53][54][55][56][57] Sequential addition reactions to create multi-adducts with exceptional architectures were presented, [57][58][59][60][61][62][63] including reactions between C 60 and anthracenes, where mono-, 16-18, 21, 26, 64 bis-, 19,[64][65][66][67][68] and specific tris-adducts were reported. 63,69 The kinetic and thermodynamic driving forces for the formation of specific bis-and tris-adducts has become a much discussed issue.…”