Efficient synthesis of C2v-symmetrical pentakisadducts of C60 as versatile building blocks for fullerene architectures that involve a mixed octahedral addition pattern.
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.
Department of Chemistry and Pharmacy & Interdisciplinary Center of Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestrasse 42, 91054 Erlangen, Germany.
Frank
F
Hörmann
Wolfgang
W
Donaubauer
Frank
F
Hampel
Andreas
A
Hirsch
D002851:Chromatography, High Pressure Liquid; D003500:Cyclization; D037741:Fullerenes / Q000737:chemistry*; D007555:Isoxazoles / Q000737:chemistry*; D015394:Molecular Structure; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014961:X-Ray Diffraction
D037741:Fullerenes; D007555:Isoxazoles