Tris adducts

Nitromethane is the most reactive nitroalkane that favors strong reaction to the tris adduct (see Nitroalcohols). 

Conjugated dienes yield mono-adducts with dihalocarbenes at the more electron-rich C=C bond further reaction at the less reactive bond may also occur [e.g. 4,8,19, 23, 31, 37, 49, 62, 69, 94]. Cycloheptatriene yields the syn- and nnti-1,2 5,6-bis-adducts (14.5 and 22.9%) and the syn-1,2 5,6-ann -3,4-tris-adduct with dichloro-carbene [62], The facile reaction of cyclopropylethenes with dihalocarbenes produces dicyclopropyl compounds [53, 117]. Isoprene reacts with chloro(phenylthio)carbene across the more reactive 1,2-bond (51%) [146]. 

Beuerle F, Chronakis N, Hirsch A (2005) Regioselective synthesis and zone selective deprotection of [60]fullerene tris-adducts with an e,e,e addition pattern. Chem. Commun. 3676-3678. 

Marchesan S, Da Ros T, Prato M (2005) Isolation and characterization of nine tris-adducts of N-methylfulleropyrrolidine derivatives. J. Org. Chem. 70 4706 1713. 

The cytotoxic and photocytotoxic effects of two water-soluble fullerene derivatives, a dendritic CL mono-adduct and the malonic acid CL tris-adduct were tested on Jurkat cells when irradiated with UVA or UVB light (Rancan et al., 2002). The cell death was mainly caused by membrane damage and it was UV dose-dependent. Tris-malonic acid fullerene was found to be more phototoxic than the dendritic derivative. This result is in contrast to the singlet oxygen quantum yields determined for the two compounds. 

Rancan F, Rosan S, Boehm F, Cantrell A, Brellreich M, Schoenberger H, Hirsch A, Moussa F (2002) Cytotoxicity and photocytotoxicity of a dendritic C(60) mono-adduct and a malonic acid C(60) tris-adduct on Jurkat cells. J Photochem Photobiol B 67 157-162. 

Various bis-and tris-adducts discussed so far, such as 6-13, belong to one of these subgroups. However, when achiral addends such as malonates are used the... 

The relative configuration within the precursor trisadducts is retained in the inherently chiral C -symmetrical hexakisadducts, while the absolute configuration has changed. The Cotton effects of such hexakisadducts are much less pronounced than those of their precursor tris-adducts, since the local symmetry of the fullerene core is very close to Tjj. 

The first example of a tether remote functionalization was the synthesis of the tris-64 (Scheme 10.14) [75,78]. For this purpose the computer-aided chemically designed addend 63 was allowed to undergo a successive nucleophilic cyclopropanation/ [4-1-2] cycloaddition sequence yielding the tris-adduct 64 in 60% yield with complete regio selectivity. Subsequent cyclopropanation of the remaining octahedral sites with a large excess of diethyl bromomalonate and DBU afforded the hexakisadduct 65... 

Fig. 22 C2-symmetrical C76 diastereoisomer (S, s/ A)-S4, C2v-Cys tris-adduct ( )-55 and, C2-symmetrical monoadduct (56) of achiral Did-CzA.

The redox properties of two bis-adduct and four tris-adduct derivatives of Cyg (see (55) in Fig. 22) have also been reported [44]. In all cases, at least four one-electron reduction steps and one oxidation are observed. All reductions occur at more negative potentials than those of the pristine cage, while the oxidation is facilitated. The first one-electron reduction is reversible, but the second one is irreversible for half of the derivatives. In fact, the second reduction results in a chemical transformation leading to the observation of the parent cage redox... 

The removal of methano addends from fuUerenes using CPE is an efficient and versatile procedure, which has heen successfully employed in the separation of enantiomers and constitutional isomers of the higher fullerenes, for the isomerization of his- and tris-adducts of Ceo, and more recently, for the selective removal of one addend in the presence of another. 

Reactions of the silyldiazonium compounds with Cgo were examined30. To the toluene solution of Cgo was slowly added the silyldiazonium compounds at room temperature and the products obtained were separated by gel permeation chromatography (equation 19). The yields of the mono-, bis- and tris-adducts are given in Table 7. The 1 H-NMR chemical shift of the methine proton and the 2,3Jq p[ coupling constants with the Cgo carbon support the methanoannulene structure (51). 

Unlike the reversed shift of the emission band compared to the dihydrogen addend type, the singlet lifetime in the bis- and tris(bis-(ethoxycarbonyl)-methylene) derivatives is increased comparable to the former multiple adducts. The values range from 1.7 to 3.1 ns (tris-adduct), depending on the distorted T7-electron system of the fullerene core [67,108], In comparison to C6o, the fluorescence quantum yield for the malonic ester hexaadduct is increased by the factor 10 (30 X 10 4) [67,111], In the case of both pyrrolidino hexa-adducts (Th 14 and D3 15, Fig. 13), the effect is remarkably higher. The fluorescence quantum yields are increased about 100-fold (-0.02) compared to C6o. On the other hand, the singlet lifetime is only partly increased with -3.5 ns [111,112],... 

The search for alternatives to the stepwise addition of new addends to a mono-, bis-, or tris-adduct of Cr,o for the preparation of highly functionalized fullerenes has been a challenge since the beginning of fullerene chemistry. Here we present the principal approaches introduced to control the regiochemistry of multiple additions to fullerenes by the use of tethered addend systems. The tethered macro-cyclization method proved to be a major breakthrough and has provided relatively facile access to otherwise strongly disfavored addition patterns. 

Tris-adduct Formation by Tether-directed Binge Addition... 

In contrast to the large number of bis-adducts generated through a tether-directed methodology, only a few examples of tris-adducts have been described [19,45,46],... 

Figure 10 Regioselective one-step synthesis of topologically chiral trans-3,trans-3,trans-3 and e,e,e [60]fullerene-cyclotriveratrylene tris-adducts.

Figure 11 Synthesis of the e,e,e (35) and trans-4,trans-4,trans-4 (36) tris-adducts.

Hirsch and co-workers last year introduced a new concept for the tether-directed multifunctionalization of Cgo> with the use of cyclo-[n]-octylmalonates such as 34 (Figure 11) [50], As a result of the identical spacer lengths in these macrocycles, only bis- and tris-adducts with rotational symmetry are formed. The reaction of cyclo-[3]-octylmalonate (34) with Cgo leads to the e,e,e isomer 35 with high regioselectivity and excellent yield (94%). Additionally, 6% of... 

Figure 28 Formation of C2-symmetric bis-adducts of C78 from electrolysis of tris-adduct ( )-74.

Figure 29 Cyclic voltammogram in CH2C12(+0.1 M Bu4NPF6) under vacuum, scan rate 100 mV s 1 for the tris-adduct ( )-74 and the retro-Bingel product ( )-75.

Covalently-bound addition complexes have been shown to result from the reactions of a wide variety of aromatic compounds, activated by one or more nitro-groups, with bases or other nucleophilic species. In some cases di-adducts or tri-adducts are also formed by the addition of more than one molecule of base. There is considerable current interest in these adducts and this article will be concerned with their structures and stoichiometries and with the factors governing their stabilities. The second section deals with the spectroscopic and chemical studies which have been used in structural elucidations. Some general principles... 

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