Fullerenes reactions, with

Formazane formation 335 f. Frieswell-Green mechanism 400 f. Fullerenes, reaction with ArNj 188 6-Fulvenone 136 Furan... 

Several studies have demonstrated the successful incoriDoration of [60]fullerene into polymeric stmctures by following two general concepts (i) in-chain addition, so called pearl necklace type polymers or (ii) on-chain addition pendant polymers. Pendant copolymers emerge predominantly from the controlled mono- and multiple functionalization of the fullerene core with different amine-, azide-, ethylene propylene terjDolymer, polystyrene, poly(oxyethylene) and poly(oxypropylene) precursors [63,64,65,66,62 and 66]. On the other hand, (-CggPd-) polymers of the pearl necklace type were fonned via the periodic linkage of [60]fullerene and Pd monomer units after their initial reaction with thep-xy y ene diradical [69,70 and 71]. 

There are several reviews on the rapidly growing field of fullerene reactions, e. g. by Olah et al. (1993). For reactions of C60 with diazoalkanes see Zollinger, 1995, Sec. 8.4. 

The mechanism for the formation of complex hydrocarbons through fullerenes is loosely taken from Helden et al.119 and Hunter et al.,120 and is depicted in Figure 2. As in the work of Thaddeus,117 linear carbon clusters grow via carbon insertion and radiative association reactions, although in this case a large number of additional reactions involving neutral atoms such as C, O, and H and neutral molecules such as H2 are also included. Reactions with H and H2 serve to produce... 

Fullerene is nitrated with N204 to give hexanitro[60]fiillerene C60(NO2)4, which undergoes SNAr reaction with various nucleophiles.32... 

An alternative synthetic approach, first developed by Bingel225 allowed the efficient nucleophilic cyclopropanation of fullerenes via their reaction with bromomalonate derivatives in the presence of base. This approach, the most reliable method for the synthesis of functionalized methanofullerenes, combined the advantages of mild... 

Figure 15.9 The reaction of the amine-blocked derivative of 3-hydroxypropylamine with ethylmalonyl chloride gives an ethylmalonate-protected-amine compound, which can be used in the Bingel reaction to create an amine group on a fullerene surface. Reaction with Cfl in the presence of I2 and DBU gives the cyclopropanation product that can be deprotected with TFA to yield the free amine.

Isaacs, L., Wehrsig, A., and Diederich, F. (1993) Improved purification of C60 and formation of S- and 7i-homoaromatic methano-bridged fullerenes by reaction with alkyl diazoacetates. Helv. Chim. Acta 76, 1231-1250. 

Novel pyrazine-containing cydoadducts 80a-c were synthesized by Diels-Alder reaction of [60]fullerene with the corresponding 2,3-bis(bromomethyl)pyrazine derivatives 79a-c (Scheme 9.23) [73] the 2,3-pyrazinoquinodimethanes were trapped as the Diels-Alder adducts by reaction with [60]fullerene under reflux in o-dichloroben-zene (ODCB) as solvent with classical heating and under the action of microwave ir-... 

The scope of the reaction has been demonstrated by the preparation of a series of isoxazolo[60]fullerenes 198 (Scheme 9.61) [109]. The nitrile oxides were prepared from the corresponding oximes by reaction with NBS or NCS and subsequent treatment of the mixture with triethylamine under microwave irradiation. 

SCHEME 12. Diels-Alder reactions with fullerenes as dienophiles... 

Second, fullerene C6o was involved in the standard reaction with very reactive nitronate CH2=N(0)0SiMe3 (362b). 

Photochemical digermation reactions of fullerene[60] with a tetragermacyclobutane140,141 and a digermacyclopropane142 have been reported. 

Organometallic compounds, 14 550-551 25 71. See also Organometallics carbides contrasted, 4 648 as initiators, 14 256-257 iridium, 19 649-650 molybdenum(III), 17 27 osmium, 19 642-643 palladium, 19 652 platinum, 19 656-657 reaction with carbonyl groups, 10 505-506 rhodium, 19 645-646 ruthenium, 19 639 sodium in manufacture of, 22 777 titanium(IV), 25 105-120 Organometallic fullerene derivatives,... 

Diels-Alder reactions have been used to synthesize and functionalize polymers, as reported by several groups. Rotello and coworkers112, for example, covalently attached [60]fullerene to furan and cyclopentadiene substituted resins. The reaction with the furan substituted resin proved reversible. The resin was recovered by heating the fullerene functionalized resin. 

The photo-induced single and double Diels-Alder reactions between [60]fullerene and 9-methylanthracene (212) which gave 213 and 214 were performed in the solid state by Mikami and colleagues (equation 60)141. The Diels-Alder reaction was considered to proceed following a photo-induced electron transfer from 9-methylanthracene to fullerene. The higher ionization potential of anthracene should explain its inreactivity toward the cycloaddition reaction with [60]fullerene. 

Cheng and coworkers142 reported the first Diels-Alder reactions of fullerenes with dienes having an electron-withdrawing group at C(l). The reactions with [60]fullerene proceeded at elevated temperatures to afford the corresponding adducts with moderate yields. The adducts appeared to be more stable than the adducts of electron-rich dienes. 

Daub and colleagues have also described the cycloaddition reaction of 534 with [60]full-erene (209) (equation 157)319 and [70]fullerene320, which were the first [8 + 2] cycloaddition reactions with fullerenes described in the literature. Reaction with [60]fullerene afforded 546 as the main product with a yield of more than 90%. On the basis of the results of previous cycloadditions performed with fullerenes, it was assumed that it was a 6,6-double bond which had reacted with 533, [60]fullerene adding to the less hindered site of 534. 

Enes et al. (2006) recently presented new fulleropyrrolidines bearing one or two 3,5-di-tert-bvAy 1-4-hydroxyphcny 1 units, the EPR studies of which demonstrated that these derivatives are antioxidants. In this case, the presence of the fullerene unit seems to play a marginal role in the reaction with peroxyl radicals, which is governed by the phenol portion. Despite this, the presence of C60 should contribute to scavenge radicals in hypoxic conditions, where alkyl radicals could be the main oxidative products to be removed. 

In two recent reports (Mroz et al., 2007b Tegos et al., 2005) we studied the photosensitizer properties of two series of three functionalized fullerene compounds, one series with polar diserinol groups (BF1-BF3), and a second series of three compounds with quaternary pyrrolidinium groups (BF4-BF6) (Fig. 4.5). The bis-substituted and tris-substituted fullerenes are actually mixtures of regioisomers of the same molecular formula due to reaction with different double bonds. We asked the question whether the photodynamic effects displayed by these compounds operated... 

Reaction with MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide, Sigma ) was carried out in 96-well plate at 37 °C in thermostat (Carmichael et al., 1987). The cells were incubated for 0.5, 2, and 5 h in RPMI1640 medium in the presence or absence of fullerenes C60 samples, then MTT was added, and incubation continued for 2h. The content of generated formazane was evaluated by spectrophotometry at the wavelength of X = 570 nm at the digital spectrophotometer IFCO-2 (ABOTEK, Russia). 

Taking into account that ROS produced by irradiated fullerenes C60 may act only in the radius of their short diffusion existence, one may suppose that cytotoxic effect is determined by the interaction of fullerene C60 with the surface of cells and initiation of chain reactions of free radical peroxidation in membranes. That is why the influence of photoexcited fullerene C60 on the course of LPO process was studied and evaluated by the content of generated primary (diene conjugates) and final (Schiff bases) products. The content of diene conjugates in thymocytes was 17.7 4.2, inEAC cells was 21.1 1.3, andinL1210 was 12.8 3.1 nM/mg protein, and Schiff bases -56 7.9,46.5 4.5, and 36.6 4.6 rel. units/mg protein, respectively, and did not alter during 1 h incubation of the cells. 

Covalent functionalization of fullerenes has also been used to obtain surface-modified fullerenes that are more compatible to polymer matrices in order to fabricate composites. In this context, four basic strategies were developed. The first one allows the fullerenes to react during the monomer polymerization, so that the fullerene can be attached to the polymer chain [111, 112]. Second, an already synthesized polymer is treated using specific conditions that allow the chemical reaction with fullerenes [113,114]. Third, the fullerenes are chemically bonded to a monomer which is polymerized or co-polymerized to obtain the modified monomer [115,116]. Fourth, a dendrimer can be synthesized around a fullerene which then acts as a nucleus [117,118]. 

Prakash, Chlorination and bromination of fullerenes. Nucleophilic methoxylation of polychlorofullerenes and their aluminum trichloride catalyzed friedel-crafts reaction with aromatics to polyarylfullerenes, Journal of American Chemical Society, vol. 113, pp. 9385-9387,1991. 

---