A facile access to [60]fullerene-fused δ-lactones: unexpected reaction pathway of benzenediazonium-2-carboxylates controlled by organic bases
作者:Guan-Wu Wang、Bo Zhu
DOI:10.1039/b820395d
日期:——
The reaction of [60]fullerene with anthranilic acids and isoamyl nitrite in the presence of triethylamine unexpectedly afforded [60]fullerene-fused δ-lactones, which would be difficult to be prepared by other known methods; the organic base played a crucial role in the unusual reaction pathway.
[reaction: see text]. The [2 + 2] cycloaddition between [60]fullerene and benzyne generated from 4,5-dimethoxyanthranilic acid (4) afforded bisadducts 5 along with the monoadduct. All of the eight possible regioisomers were first isolated by HPLC and then characterized on the basis of MS, NMR, UV-vis, and CD spectroscopies.
Cycloaddition is one of the best-studied types of reactions in the organic chemistry of fullerenes, engendering [6,6]-closed adducts in the vast majority of cases. Notwithstanding that a formation of open fulleroid structures is undoubtedly of theoretical interest, no one has demonstrated the conformation of [5,6]-open fulleroid via the direct cycloadditions. Here, we establish that cycloaddition between C-60 and benzyne in situ generated from 2-amino-4,5-dibutoxybenzoic acid affords a new type of elusive [5,6]-open structure that is characterized on the basis of NMR, UV-vis spectroscopy, and cyclic voltammetry. Additionally, from density functional theory (DFT) calculations for possible [5,6]-open and [6,6]-closed adducts induced of benzyne-C-60 reaction, as expected, features such as the charge distributions, binding characteristics, and frontier molecular orbital levels, are affected by the different binding modes in C-60 cage. (C) 2013 Published by Elsevier Ltd.