Reductive Benzylation of Singly Bonded 1,2,4,15-C₆₀ Dimers with an Oxazoline or Imidazoline Heterocycle: Unexpected Formation of 1,2,3,16-C₆₀ Adducts and Insights into the Reactivity of Singly Bonded C₆₀ Dimers

Abstract

Upon reduction, singly bonded 1,2,4,15-C60 dimers with an oxazoline or imidazoline heterocycle dissociate into monoanionic 1,2,4-C60 intermediates, which surprisingly leads to the formation of 1,2,3,16-C60 rather than 1,2,4,15-C60 adducts of the original configuration by further benzylation, even though the analogue of dibenzylated C60 oxazoline with a 1,2,4,15-configuration is stable and has been obtained. These results are corroborated by computational calculations, which rationalize the reaction and clarify the structure of the 1,2,3,16-C60 adducts, providing new insights into the intrinsic reactivity of singly bonded C60 dimers.

Successively Regioselective Electrosynthesis and Electron Transport Property of Stable Multiply Functionalized [60]Fullerene Derivatives

“…[60]Fulleroindolines 1a-c were synthesized according to our reported procedure [43]. The cyclic voltammograms (CVs) of 1a-c were very similar and showed an irreversible second redox process (Figures S1-S3), hinting that the C-N bond cleavage occurred after receiving two electrons [25][26][27][28][29]38]. It turned out that the reaction of the dianionic species of 1a-c with phthaloyl chloride indeed afforded the desired cis-3′ regioisomers 2a-c.…”

“…Only one isomeric monocycloadduct is usually formed, up to 8 regioisomeric biscycloadducts have been isolated from cycloaddition reactions of C 60 [8]. On the other hand, the regioisomers of tetrafunctionalized C 60 derivatives reported most commonly are 1,2,3,4-isomers (A) [9][10][11][12][13][14], 1,4,11,15-isomers (B) [15][16][17][18], 1,2,4,15-isomers (C) [19][20][21][22][23], and 1,2,3,16-isomers (D) [24][25][26][27][28][29], while for the hexafunctionalized C 60 derivatives, the most frequently encountered regioisomers are 1,2,3,4,5,6-isomers (E) [30][31][32] and 1,2,4,11,15,30-isomers (F) [15][16][17][18][33][34][35] (Figure 1). Although the elegant templated multifunctionalizations of fullerenes have been devised to realize high regioselectivity [8,36], the regiocontrol on the formation of a specific isomer of biscycloadducts and multicycloadducts is still a daunting task.…”

“…The electrophilic-to-nucleophilic reactivity reversal of fullerenes and their derivatives caused by electrochemical reduction opens a new territory in fullerene chemistry and has demonstrated increasing importance in the efficient synthesis of novel fullerene derivatives [37], including the abovementioned types A, C, and D [11,19,[25][26][27][28][29]. It was interestingly found that the same dianionic [60]fulleroindoline (1a 2-, vide infra) behaved differently toward alkylating and acylating reagents.…”

Electrochemically Promoted Benzylation of [60]Fullerooxazolidinone

“…Later, they obtained two 1,2,3,16-adduct isomers and one 1,2,3,4-adduct isomer by reductive benzylation of fulleroimidazoline [37]. In 2015, Gao and coworkers obtained 1,2,3,16-adducts by electrochemical benzylation of singly bonded 1,2,4,15-C 60 dimers with an oxazoline or imidazoline moiety [38]. Among the various fullerene derivatives, fullerooxazolidinone derivatives are of interest because the carbamic moiety is fused to the fullerene skeleton via two heteroatoms.…”

Regiocontrolled Electrosynthesis of [60]Fullerene Bisadducts: Photovoltaic Performance and Crystal Structures of C60 o-Quinodimethane Bisadducts

“…The reactions involving anionic fullerene species have shown a good regiocontrol for multifunctionalization via the charge-directed mechanism. − It is therefore of interest to investigate the regioselectivity of C 60 bisfunctionalization by controlled potential bulk electrolysis (CPE), which generates anionic fullerene species electrochemically. ,− Herein, we report the electrosynthesis of C 60 (QM) 2 starting from the dianion of C 60 QM (C 60 o -quinodimethane monoadduct). In contrast to the traditional Diels–Alder approach, ,, the CPE method resulted in fewer regioisomers, facilitating the purification of the C 60 (QM) 2 isomers.…”