Fullerenes epoxides

Fullerene epoxide, C )0, is formed by the UV irradiation of an oxygenated benzene solution of Cfio The O atom bridges a 6 6 bond of the closed fullerene structure. The same compound is also formed as one of the products of the reaction of Cgo with dimethyldioxirane, Mc2COO (see later). ... 

Nakamura et al. have reported a one-step multiple addition of amine to [60] fullerene [95]. Here, a mixture of [60]fullerene and N-methylpiperazine was irradiated by means of an incandescent lamp in air to give a tetra(amino)fullerene epoxide in excellent yield (Scheme 4.64). 

Finally, the unavoidable fullerenes were, of course, immobilized on solid surfaces. Fullerene, Ceo, and fullerene epoxide formed stable monolayers on water. The limiting molecular surface area was 95 A and a UV/VIS spectrum with bands around 300 nm was observed in LB multilayers on quartz. ... 

Cox, Smith, and coworkers have prepared photochemically the fullerene epoxide C oO, [139], which has since proven to be an important starting material for further functionalizations [77,140]. The photooxidation was effected by irradiating an oxygenated benzene solution of C50 at room temperature for 18 hr, resulting in C O in 7% yield. The photooxidation rate and yield were significantly enhanced in the presence of benzil in the solution for photoirradiation [139]. It has been shown that the Cgo epoxide thus prepared has a 6,6-closed structure (18). 

R495 Y. Tajima, K. Takeshi, Y. Shigemitsu and Y. Numata, Chemistry of Fullerene Epoxides Synthesis, Structure, and Nucleophilic Substitution-Addition Reactivity , Molecules, [online computer file], 2012, 17, 6395. 

Metal-free reactions represent a direct way to study the confinement effects induced by the nanotube itself. Few such reactions have been carried out within CNTs, but notable examples include the formation of linear structures, such as fuUerene [151] and fullerene epoxide oligomers [174], formation of DWCNTs from endohedral fiiUerenes encapsulated in SWCNTs [71,155,156], or from encapsulated ferrocene [165], graphene nanoribbons (GNR) [186,187], the transformation of [Fe(C6oMc5)Cp] into encapsulated C70 [157], or the transformation of adamantane [188] and functionalized diamantine [189] in carbon chains. 

A series of Ceo complexes of the type [Rh(acac)(T 2-C6o)(pyridine)2] have been reported and the X-ray crystal structure with 3,S-dimethylpyridine has been determined. The formation and structural characterisation of the fullerene epoxide complex [Ir(r -C6oO)(CO)Cl(PPh3)2] has been described. The synthesis of [Ir(li2.C6o)(CO)(H)(PPh3)2] has been reported. Multiple additions of Vaska-type iridium complexes to have been shown to result in preferential crystallisation of the "para" double addition products C6o) If(CO)Cl(PR3)2 2l (R = Me, Et). The X-ray crystal structure of [ (112-C84)(CO)Cl(PKi3)2l has been reported . 

Tajima and coworkers obtained a l,4-bis(aryl)-l,4-dihydro[60] fullerene compound (129) from BF3 OEt2 promoted nucleophilic substitution of fullerene epoxide (130) in excellent yield (Equation 78) [81]. 

Direct irradiation of [60]fuUerene 47 in the presence of trimethylamine is reported to yield the adducts 47a and 47b as primary and secondary products (Scheme 29). Only small amounts of these adducts are isolated from complex product mixtures. Formation of 47a is proposed to occur via an electron transfer, proton transfer, radical coupling mechanism similar to that for addition of stilbene and trialky-lamines. Formation of 47b is found to require oxidation of 47a by singlet fuUerene. Direct irradiation of 47 with dimethylamine in the presence of air is reported to result in the formation of the tetra(amino)fullerene epoxide 47c (Scheme 29). Isolated yields as high as 98% are reported for the reaction of N-methylpiperazine. More hindered secondary amines such as EtjNH and primary amines fail to undergo this extraordinary reaction. 

In general, by [2 -1- 1]-photocycloaddition reactions methanofullerenes, fullerene epoxide, and azirid-inofullerenes as the corresponding oxygen and nitrogen analogues with a [6,6]-closed structure are obtained as shown in Figure 28.5. 

FIGURE 28.5 Fullerene derivatives obtained by [2+1 ] -photocycloaddition methanofiillerene, fullerene epoxide, and aziridinofullerene. 

Fullerene epoxide (QqO, 30), the oxygen analogue of the methanofullerene, can be obtained by the extended irradiation of C50 in an oxygen atmosphere as reported by Smith et al. Irradiation of Qowith... 

Similarly, irradiation of tetrasubstituted bis(fulleroid) derivatives 72 in the presence of oxygen affords a 12-membered ring diketone on the surface of the fullerene. In spite of the same 60 n electronic structure as C o, whose photooxygenation leads to the formation of the fullerene epoxide, [2 -I- 2]-cycloaddition of 72 with Oj followed by symmetrical ring opening of the dioxetane 73 predominantly occured to give 74 (Scheme On the contrary, oxidation and Diels-Alder reaction of the mother... 

The synthesis of fullerene epoxides via [2 -I- l]-photoq cloaddition of singlet oxygen has already been discussed (in the section [2 -1- l]-Photocycloaddition ). Alternatively, fullerene oxides can also be obtained by thermolysis or photolysis of the [6,6]-closed ozone adduct of Qq and C70, namely 60 3 75 and C70O3 77.Thermolysis of QqOj yields the fullerene epoxide with a [6,6]-closed structure. In contrast, photolysis resulted in the formation of the [5,6]-open oxidoannulene 76 with an ether structure (Scheme 32). 

---