Reaction of C60F18 with diethyl bromomalonate: diversion of the Bingel reaction and formation of the first 18π annulenic fullerene

Xian-Wen Wei; Anthony G. Avent; Olga V. Boltalina; Adam D. Darwish; Patrick W. Fowler; John P. B. Sandall; Joan M. Street; Roger Taylor

doi:10.1039/B105921C

Reaction of C₆₀F₁₈ with diethyl bromomalonate: diversion of the Bingel reaction and formation of the first 18π annulenic fullerene†

Xian-Wen Wei,^a Anthony G. Avent,^a Olga V. Boltalina,^b Adam D. Darwish,^a Patrick W. Fowler,^c John P. B. Sandall,^c Joan M. Street^d and Roger Taylor*^a

Author affiliations

* Corresponding authors

^a The Chemistry Laboratory, CPES School, Sussex University, Brighton, UK

^b Chemistry Department, Moscow State University, Moscow 119899, Russia

^c School of Chemistry, Exeter University, Exeter, UK

^d Chemistry Department, The University, Southampton, UK

Abstract

Reaction of C₆₀F₁₈ with diethyl bromomalonate in the presence of DBU results in the nucleophilic replacement of either one, two, or three of the most accessible fluorine atoms by CBr(CO₂Et)₂ moieties, in preference to formation of a cyclopropanated derivative (the normal Bingel reaction). Substitution that takes place δ to the departing fluorine, is the first proven example of S_N2′ substitution in a fullerene, and appears to be sterically driven. The ratio of mono-/poly-substitution products can be controlled by varying the rate of addition of the DBU and the molar ratio between C₆₀F₁₈ and the other reagents. The tri-substituted product is an [18]annulene, has an intense emerald-green colour ascribable to the electron delocalisation in the (equatorial) annulene belt (bond length variation 0.018 Å), and has C_3v symmetry. This is the first example on an annulenic fullerene (moreover of an all-trans annulene or trannulene). The extent of substitution in each compound is identified from the fluorinated fragments (C₆₀F₁₅, C₆₀F₁₆, and C₆₀F₁₇, respectively, for tri-, di-, and mono-substitution) in the EI mass spectra, and by their ¹H and ¹⁹F NMR spectra. The structure of the tri-substituted [18]annulene was confirmed by single crystal X-ray diffraction. Normal Bingel cycloaddition also takes place between C₆₀F₁₈ and diethyl malonate–DBU in CBr₄, to give C₆₀F₁₈C(CO₂Et)₂ and C₆₀F₁₆C(CO₂Et)₂ in relatively low yields. Calculations indicate a critical size of substituent required to produce δ-substitution, rather than ipso-substitution of the departing fluorine.

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Article information

DOI: https://doi.org/10.1039/B105921C
Article type: Paper
Submitted: 04 Jul 2001
Accepted: 26 Oct 2001
First published: 05 Dec 2001

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J. Chem. Soc., Perkin Trans. 2, 2002, 41-46

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Reaction of C₆₀F₁₈ with diethyl bromomalonate: diversion of the Bingel reaction and formation of the first 18π annulenic fullerene

X. Wei, A. G. Avent, O. V. Boltalina, A. D. Darwish, P. W. Fowler, J. P. B. Sandall, J. M. Street and R. Taylor, J. Chem. Soc., Perkin Trans. 2, 2002, 41 DOI: 10.1039/B105921C

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Journal of the Chemical Society, Perkin Transactions 2