Approaches to open fullerenes: Synthesis and kinetic stability of Diels-Alder adducts of substituted isobenzofurans and C60

Shih-Ching Chuang, Michael Sander, Thibaut Jarrosson, Scott James, Eugene Rozumov, Saeed I. Khan, Yves Rubin*

*Corresponding author for this work

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

(Chemical Equation Presented) We have examined the reactions of 1,3-disubstituted isobenzofurans with the fullerene C60 in the context of an approach to open a large orifice on the fullerene framework. A variety of substituted isobenzofurans (6a-h), generated from the reaction of 1,4-substituted 1,4-epoxynaphthalenes 3a-h with 3,6-bis(2-pyridyl)-1,2,4,5- tetrazine (4a) or 1,2,4,5-tetrazine (4b), were added to C60 to afford the Diels-Alder adducts 7a-h. The thermal stability of these adducts toward retro-Diels-Alder fragmentation differs greatly in solution from that in the solid state. In solution, the relatively facile retro-Diels-Alder fragmentation of monoadducts 7a and 7c, to give C60 and the free isobenzofurans 6a and 6c, have rate constants (and activation barriers) of k = 9.29 × 10-5 s-1 at 70°C (Ea = 32.6 kcal mol -1) and k = 1.36 × 10-4 s-1 at 40°C (Ea = 33.7 kcal mol-1), respectively, indicating that the addition of isobenzofurans to C60 is readily reversible at those temperatures. In the solid state, thermogravimetric analysis of adduct 7a indicates that its decomposition occurs only within the temperature range of 220-300°C. As a result, these compounds can be stored at room temperature in the solid state for several weeks without significant decomposition but have to be handled within several hours in solution.

Original languageEnglish
Pages (from-to)2716-2723
Number of pages8
JournalJournal of Organic Chemistry
Volume72
Issue number8
DOIs
StatePublished - 13 Apr 2007

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