Approaches to Open Fullerenes:  Synthesis and Thermal Stability of cis-1 Bis(isobenzofuran) Diels−Alder Adducts of C₆₀

Abstract

In a quest to form wider openings within the cage of the fullerene C60 through controlled bond-breaking reactions, we have examined the double saturation of adjacent C=C bonds within a six-membered ring of C60. We have investigated the double Diels-Alder cycloaddition of two tethered isobenzofurans to the fullerene C60. We obtained cis-1 adducts in good yields after reacting the methylene- or quinoxaline-tethered bis(isobenzofuran) precursors 2a-k with parent 3,6-dihydro-1,2,4,5-tetrazine (3b). The X-ray structure of the methylene-tethered bis(isobenzofuran)-C60 adduct 4b has been obtained; four-eclipsed substituents are held rigidly by the bicyclic addends. The cis-1 bis(isobenzofuran) bisadducts 4b and 4e-j are kinetically far more stable toward thermal retro-Diels-Alder fragmentation than are mono(isobenzofuran) adducts of C60, in solution and in the solid state as determined by 1H NMR spectroscopy or thermogravimetric analysis. A methodology for the reversible solubilization of other fullerene derivatives based on this work is also presented.

Biobased C6-Furans in Organic Synthesis and Industry: Cycloaddition Chemistry as a Key Approach to Aromatic Building Blocks

“…Several methods for generating benzyne for transformations were described (Scheme , methods A, D, C). The resulting substances served as starting compounds for aromatic derivatives. …”

Advances in polymer precursors and bio‐based polymers synthesized from 5‐hydroxymethylfurfural

“…The conversion of (24) to diisocyanates (25) was accomplished in two steps using diazides as the intermediates . Derivatives from (23), such as diols (26) and diamines (27) have also been prepared …”

4.09 Nucleophilic Coupling with Arynes

“…Because of high availability of the starting anthranilic acid derivatives, thermolysis of arenediazonium 2-carboxylates 14 would be a convenient way for the generation of arynes, [87][88][89] and reliability of this method allows its utilization to total synthesis of an antidepressant, sertraline 15 (Scheme 11). 90 Although the explosive nature of 14 is the major disadvantage of this method, in situ generation of 14 by diazotization of anthranilic acids 16 with an alkyl nitrite 91 and the use of stable aryne precursors, 1-(2 0 -carboxyaryl)-3,3-dimethyltriazenes 17, 92 have been recognized as safer alternatives (Scheme 12).…”