A regiospecific bis-adduct of C70 with anthracene was prepared with unusually high yield (68%) by the Diels-Alder reaction in the absence of solvent (melt). The structure of the bis-adduct was an unexpected 12 o'clock isomer, as determined by single crystal X-ray diffraction, thermal gravimetric analysis (TGA) and spectroscopy.

The efficient preparation of monoadducts of [60]fullerene and seven anthracenes (anthracene, 1-methylanthracene, 2-methylanthracene, 9-methylanthracene, 9,10-dimethylanthracene, 2,3,6,7-tetramethylanthracene, and 2,6-di-tert-butylanthracene) by cycloaddition in solution is described. The seven mono-adducts of [60]fullerene and the anthracenes were characterized spectroscopically and were obtained in good yields as crystalline solids. The monoadducts of [60]fullerene and anthracene, 1-methylanthracene, 2-methylanthracene and 9,10-dimethylanthracene crystallized directly from the reaction mixture. The thermolytic decomposition at 180 degrees C of the crystalline monoadducts of [60]fullerene and anthracene, 1-methylanthracene, 9-methylanthracene and 9,10-dimethylanthracene all gave rise to the specific formation of a roughly 1:1 mixture of [60]fullerene and the corresponding antipodal bisadducts ("trans-1"-bisadducts) of [60]fullerene and the anthracenes. In contrast, the crystalline monoadducts of [60]fullerene and the anthracene derivatives 2-methylanthracene, 2,3,6,7-tetramethylanthracene and 2,6-di-tert-butylanthracene all decomposed to [60]fullerene and anthracenes (without detectable formation of bisadducts) upon heating in the solid state to temperatures of 180 to 240 degrees C. The formation of the antipodal bisadducts from thermolytic decomposition of crystalline samples of the monoadducts was rationalized by topochemical control.

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Antipodal (trans-1) Diels-Alder bis-adducts 3 and 7 ± 9 of [5,6]fullerene-C 60 -I h (1) with some anthracenes were prepared highly regioselectively by heating mixtures of the solid 1 and anthracene or of (one of) three alkyl-substituted anthracenes in the absence of solvents (Scheme 2). Other bis-cycloadducts were not detected, but lesser amounts of mono-cycloadducts 2 and 4 ± 6, respectively, were also formed. Heating of solvent-free mixtures of 1 and three other alkyl-substituted anthracenes did not result in a detectable amount of (antipodal) bis-cycloadducts. The antipodal bis-adduct 7 of 1 and of 1-methylanthracene was analyzed by X-ray crystallography. The preparative outcome of heating of anthracenes and solid 1 parallels the result of the heating of the corresponding crystalline mono-adducts of anthracenes and 1. Both approaches reveal a remarkably consistent dependence of the reaction upon the presence and position of alkyl substituents at the anthracene unit. The regioselective assembly of antipodal bis-adducts from anthracene(s) and 1 cannot be rationalized by their (inherent molecular) stability, but it indicates the crucial control of the lattice. Introduction. ± Fullerenes, the spherical C-molecules [1 ± 3], are fascinating targets of chemistry, which also have enriched several other areas of the natural sciences [4 ± 6]. The original synthetic interests concerned the preparation of a variety of uniformly (mono)functionalized fullerenes [4] [6 ± 8]. More recently, the regio-and stereoselectivity of multifunctionalization reactions of the fullerenes has become a central focus, for the purpose of exploiting the spherical and polyunsaturated nature of the fullerenes [5] [6] [9 ± 12]. Several elegant synthetic strategies were developed, among these, Diederichs method of tether-directed remote functionalization [5] [9] and the reversible template-directed activation of fullerenes, used by Hirsch, Rubin, and others [6c] [10] [12c] [13].The high symmetry and pronounced dienophilic reactivity of the electrophilic [5,6]fullerene C 60 (1) rendered 1 an attractive target for a variety of [4 2]-cycloaddition reactions, which were found to occur at one of the 30 equivalent (6,6)-bonds of 1 exclusively [5] [6]. Cyclic dienes, anthracenes, and other polycyclic aromatics proved to represent useful addends in mono-and multiple cycloaddition processes with C 60 [8] [12] [14]. The mono-adduct 2 (9',10'-dihydro[9,10]ethanoanthra [11',12': 1,9][5,6]fullerene-C 60 -I h ) of anthracene and of C 60 can easily be prepared

Tris(9',10]ethanoanthracene [11',12': 1,9;11'',12'': 16,17;11''',12''': 30,31]) [5,6]fullerene C 60 , the orthogonal (e,e,e)-tris-adduct of C 60 and 9,10-dimethylanthracene, was obtained from [4 þ 2]-cycloaddition (Diels -Alder reaction) at room temperature. The thermally unstable orange red (e,e,e)-tris-adduct was purified by chromatography and was isolated in the form of red monoclinic crystals. Its C 3 -symmetric addition pattern was established spectroscopically. Its structure could be further investigated by single crystal X-ray diffraction. The (e,e,e)-tris-adduct of C 60 and 9,10-dimethylanthracene has earlier been suggested as intermediate and reversibly formed critical component in template directed addition reactions of C 60 . This previously elusive compound has now been isolated and structurally characterized.Introduction. -The discovery of the fullerenes [1] and of an efficient method to produce substantial amounts of these spherical carbon molecules [2] has opened a new era of chemistry [1] [3 -5] and has paved the way to synthetic, spectroscopic, and structural studies [6]. One major goal of these studies concerned the exploration of methods to achieve specific exohedral modifications of the symmetric spherical C- . In other cases, the thermal reversibility was exploited to achieve reversible attachment of fullerenes to solid support [19].As the highly symmetrical C-sphere provided by the [5,6]fullerene 1 represents a unique basis for building up three dimensional molecular structures by multiple exohedral functionalization, particular attention was paid to the problem of regioselectivity in functionalization reactions [7] [8]. The underlying need for regiocontrol has provoked extensive studies on i) the patterns of the inherent reactivity of [5,6]fullerene