Fullerene methylene bridged

Figure 4.7 Electronic-absorption spectra recorded in toluene of a mixture of (ethoxycarbonyl)-methylene-bridged fullerenes 114 with the relative ratio (1 1 3) (—), of pure isomer 114a (- ), and of Qq (—) [129. ...

Dimers with two methylene bridges and a cyclobutane fusion were synthesized by thermolysis of ethoxycarbonylmethano-l,2-dihydro[60]fullerene. They have a similar structure as 328 [374],... 

Addition of a-diazoketones derived from (W, A )-tartaric and (S )-glutamic acids, followed by dinitrogen extrusion, afforded enantiomerically pure 1,2-methano[60]fullerenes with an acylated methylene bridge.441 Bestmann and co-workers showed that these adducts can be thermally rearranged to substituted fullerene-fused dihydrofurans. 

In addition to the dumbbell-type structure 3, fullerene dimer structures having the two fullerene cages connected by a single bond and a methylene or an oxa bridge such as 7a and 7b are possible, and have been actually reported... 

Figure 4.6 Chemical shifts for the bridgehead C atoms and the methylene H-atoms and coupling constants j(CH) for the methano bridge C atoms in H2 for isomers 113a and 113b. The corresponding C atoms resonate in the region between 130 and 150 ppm together with all other sp -carbons of the fullerene sphere. For the 1,6-addition adduct of with (p-methoxy-phenyl)diazomethane, the peak position of the bridgehead C atoms was found by HETCOR analysis to be 138.65 ppm [110. ...

Cycloaddition of diazoalkanes to 6-6 bonds was among the first reactions tested on the carbon cages41 and affords isolable fullerene-fused pyrazolines as primary adducts. Photochemically induced extrusion of N2 from the latter yields 6-6-closed methanofullerenes having the functionalized bond embedded in a cyclopropane substructure, whereas the thermal process affords 6-5 open homofullerenes in which a methylene group is bridging the open junction between a six- and a five-membered ring.15-17... 

The simplest polycycles stem from two triply-bridged points. These systems are exemplified by Trost et al. s 4,8-dihydrodibenzo[oi,g7z]pentalene (69) [87, 88], a precursor for a purturbed [12]annulene dianion, and Mislow et al. s double-bridged biphenyl derivatives (generally shown as 70) [89], where X is methylene, carbonyl, or various heteroatoms. Other longer bridged biphenyls include the triple-bridged cyclophanes 71 made by Hubert and Dale [90], their unsym-metrical relatives by Cram and Reeves [91], and the recent polyalkynyl cyclo-phane (72) made by Rubin et al. [92], a proposed fullerene precursor. 

For example, irradiation of the Qo diazomethane adduct resulted in the formation of the [6,6]-closed cyclopropane QiHj, accompanied by the [5,6]-open fuUeroid. The two isomers cannot be converted neither photochemicaUy or therm ally.Upon photolysis and thermolysis of C70 pyrazolino derivatives 79a-c synthesized by addition of diazomethane to C70, four isomeric methylene derivatives of C70 are obtained. Irradiation of the pyrazolines leads to a mixture of the two isomeric [6,6]-bridged methano-fullerenes 81a and 81b, while the thermal reaction gives rise to the formation of the [5,6] -bridged isomers 80a and 80b (Scheme 35). ... 

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