Efficient Synthesis of C_2v‐Symmetrical Pentakisadducts of C₆₀ as Versatile Building Blocks for Fullerene Architectures that Involve a Mixed Octahedral Addition Pattern

Abstract

We report here on the selective synthesis of fullerene pentakisadducts 3 with an incomplete octahedral addition pattern by means of mixed [5:1]hexakisadducts 1 that involve an isoxazoline moiety as a protection group. The isoxazoline addend can be cleanly cleaved by irradiation with light. By using this protection-deprotection strategy, a variety of fullerene pentakisadducts 3 were synthesized in 29-44% overall yield without the need of HPLC purification. This novel photolytic deprotection of 1 can be explained by an initial electron transfer that leads to a biradical, which can easily eliminate the isoxazoline added. The very efficient and straightforward syntheses of the bisfullerene 4 and the globular hexakisadduct 7, each of which involves mixed octahedral addition patterns, clearly demonstrate the advantage of fullerene pentakisadducts 3 as suitable precursors for the construction of highly functional and complex [5:1]hexakisadduct architectures. Complete structural characterization of all new compounds was carried out by MALDI mass spectrometry, UV/Vis, FTIR, (1)H NMR and (13)C NMR spectroscopy, as well as X-ray diffraction.

Hierarchically Ordered Self‐Assembly of Amphiphilic Bifullerenes

“…The general synthesis of the new compounds was accomplished by connecting the corresponding [5.0] pentakis‐adducts of C 60 5 to a cyclic bismalonate,6 which has two free binding sites available for the targeted cyclopropanation of the remaining octahedral [6,6] double bonds of the fullerenes (Figure 1). In the case of symmetric bifullerenes, such as 1 or 2 , both pentakis‐precursors can be attached simultaneously.…”

Highly Efficient Synthesis of Globular (Bola)amphiphilic [5:1]Hexakisadducts of C60

“…The structural characterization was completed by using 1 H NMR and IR spectroscopy. For the synthesis of the mixed [5:1]hexakisadducts 9 a and 9 d-f, the corresponding pentakisadducts 2 b-d [11] were subjected to a cyclopropanation reaction with malonates 7 a or 7 c, respectively, in the presence of CBr 4 and DBU in toluene (Scheme 3). After a reaction time of three days, the hexakisadducts could be isolated in yields of 83-97 % (based on consumed pentakisadduct) by using flash chromatography.…”

“…These molecules are very appealing building blocks for the synthesis of complex and otherwise difficult to synthesize fullerene architectures involving a mixed octahedral addition pattern (local T h -symmetry). [1,2,11] This is due to the fact that an addition Abstract: We report on the very facile access of a new family of amphiphilic and bola-amphiphilic fullerene [5:1]hexakisadducts 9 a-f and 11 a-e. The key point for this successful approach is the use of C 2v -symmetrical fullerene pentakisadduct precursors 2 b-f allowing for the completely regioselective addition of a sixth malonate addend to complete the octahedral [5:1] addition pattern.…”

“…[8][9][10] Recently, we introduced a simple method for the selective synthesis of C 2v -symmetrical pentakisadducts 2 with an incomplete octahedral addition pattern. [11] The facile access to these interesting molecules was achieved by using an isoxazoline addend as a protection group. After completion of the octahedral addition pattern, the protection group can easily be removed by irradiation with light.…”

“…[1] By using fullerene pentakisadducts for a "convergent" reaction the synthesis of 1 was considerably improved both in yield and simplicity of the purification. [11] We report now on the very efficient synthesis of a new family of amphiphilic and bola-amphiphilic fullerene [5:1]hexakisadducts starting from C 2v -symmetric pentakisadducts 2 that contain a specific combination of neutral, cationic, and anionic addends in octahedral positions.…”