Easy access to unprecedented mixed functionalized dihydrofullerenes C60RH and C60RR′: the C602– anion route

Abstract

Functionalized mixed dihydrofullerenes C 60 RH and C 60 RR 0 are easily obtained from reactions between C 60 2À anion and halo derivatives RX and R 0 X. The key step consists in the selective reaction of the intermediate [C 60 R] À ion, as soon as it is formed, with either CF 3 CO 2 H or R 0 X. This process is made possible thanks to the very fast single electron transfer (SET) reaction between C 60 2À and RX. Functionalized dihydrofullerenes C 60 RH thus prepared are also shown to be very good starting compounds for obtaining various C 60 RR 0 derivatives.The continuously expanding interest in the chemistry of C 60 , 1 since the production of this compound on the macroscopic scale, 2 arises in particular from the outstanding properties exhibited by C 60 organoderivatives in various fields such as photovoltaïsm, 3 nonlinear optics, 4 artificial photosynthesis, 5 organic materials, 6 biology and medicine. 7 In most cases so far, the functionalization of C 60 , due to its electron-deficient polyolefinic character, 8 is achieved through two main pathways: 9 nucleophilic additions, as exemplified by the Bingel cyclopropanation reaction, 10 and cycloadditions among which [4 + 2] Diels-Alder and pyrrolidino[60]fullerene formation 11 processes are most often used. Recently the latter synthesis strategy was extended to the formation of isoxazolo[60]fullerenes 12a and pyrazolino[60]fullerenes. 12b On the other hand, as might be expected, reactions of organic electrophiles are rare and require very specific conditions. 13 In this context, our interest was first focused on the reaction of C 60 2À anion 14 with organic electrophiles, following first results reported by Kadish et al. 15 Recently we have shown that C 60 2À anion can be easily and selectively generated in acetonitrile from reduction of C 60 by means of excess sodium methanethiolate. Then, after addition of monoiodo-or diiodoalkanes, RI or I(CH 2 ) n I (n ¼ 3, 4), into this medium the expected alkylation of C 60 2À took place easily, leading to the corresponding adducts C 60 R 2 or fused cycloadducts C 60 (CH 2 ) n in very good yields. 16 Compared to the results of Kadish et al., two points emerged from our work: the very simple chemical generation of C 60 2À anion and the much higher regioselectivity observed in the formation of the adducts C 60 Me 2 , the 1,2-:1,4-isomer molar ratio being 9:1 instead of 1.4:1. We also extended our process to various halogenated derivatives possessing another functional group, thus giving rise to new functionalized C 60 derivatives, such as the fused cyclopentanone C 60 (CH 2 ) 2 CO, which can be used as new building blocks in C 60 chemistry. 17 These results prompted us to study the following problem: would it be possible, starting from C 60 2À anion, to obtain mixed adducts C 60 RR 0 in which the R and R 0 groups may be different functional groups? So far, to our knowledge, only mixed alkylation of C 60 2À has been reported in the literature. 18 It was shown in this work that C 60 ( t Bu)(CH 2 Ph) and C 60 ( t Bu)(H) co...

Selective addition to [60]fullerene of two different radicals generated from Mn(iii)-based radical reaction

“…In addition, the 1 H NMR signal arising from the methine group bonded to C 60 in 4e appeared at an unexpectedly high field (2.70 and 2.41 ppm for isomers A and B, respectively), which may be attributed to the magnetic anisotropy effect on the methine proton caused by the phenyl group. 32 The conformations of 4e calculated by the PM3 method revealed that the methine proton is very close to the phenyl group and lies in the shielding region of the phenyl ring (Fig. 1).…”

Reactions of C702– with Organic Halides Revisited: Unusual Magnetic Equivalence for the Diastereotopic Methylene Protons in 2,5-(PhCH2)2C70

“…The reactions of anionic fullerene species − are important supplements to the reactions of neutral fullerenes . Neutral fullerenes are quite electron-deficient as evidenced by the electrochemical study, where C 60 and C 70 undergo six consecutive one-electron transfer reductions, and they are typically involved in the reactions with nucleophiles .…”

Functionalization of [60]fullerene through the anionic route

“…Furthermore, it has to be mentioned that the regiochemistry of the second addition is very selective, since in these three adducts both CH 2 CO 2 R 1 and R′ groups are only in the 1,4-positions on the C 60 core [19].…”

“…RX) [19]. By comparison, under strictly identical experimental conditions, the bis-adducts (CH 2 CO 2 R 1 ) 2 C 60 2i-k were obtained in 15-20% yield after 24-h reaction.…”

“…A good candidate is benzyl chloride C 6 H 5 CH 2 Cl, which was already shown to be a weak reagent towards C 60 2-anion in THF [12]. Thus, we observed in a test experiment that the [(C 6 H 5 CH 2 )C 60 ] -anion is produced in acetonitrile between C 60 2-anion and benzyl chloride upon heating at 50°C for 3 h. A further addition of excess methyl chloroformate ClCO 2 Me, a priori more reactive than benzyl chloride, allowed to obtain the pure 1,4-(CH 2 -C 6 H 5 )(CO 2 Me)C 60 14 derivative in 15% yield [19] (Scheme 12).…”