Laboratorium für Organische Chemie, ETH-Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland.
J Am Chem Soc. 2012 Dec 19;134(50):20242-5. doi: 10.1021/ja309550z. Epub 2012 Dec 11.
The 1,3-dipolar cycloaddition of an azomethine ylide (Prato reaction) with M(3)N@I(h)-C(80) (denoted as M(3)N@C(80); M = Sc, Lu, Y, Gd) was carried out to obtain fulleropyrrolidinebis(carboxylic acid) derivatives as scaffolds for the preparation of various functionalized M(3)N@C(80) materials. The formation of two monoadduct isomers (the [6,6]- and [5,6]-adducts) were detected by HPLC and identified by NMR and vis/NIR spectroscopies. In each Prato reaction with M(3)N@C(80), the initial addition gave a [6,6]-adduct of the I(h)-C(80) cage, and subsequently, a [5,6]-adduct was obtained by complete or partial thermal isomerization via a rearrangement reaction. The reaction rate of the latter thermal conversion of the adducts was dependent on the size of the metal cluster inside C(80), and interestingly, in the reactions of Y(3)N@C(80) and Gd(3)N@C(80), this conversion was found to be reversible for the first time. Detailed kinetic studies provided the enthalpy and entropy barriers for the reactions of the adducts of Lu(3)N@C(80), Y(3)N@C(80), and Gd(3)N@C(80). The utility of the obtained Prato adducts was confirmed by preparation of a highly water-soluble Gd(3)N@C(80) derivative.
氮宾与 M(3)N@I(h)-C(80)（表示为 M(3)N@C(80)；M = Sc、Lu、Y、Gd）的 1,3-偶极环加成（Prato 反应）被用来获得富勒吡咯烷二羧酸衍生物作为制备各种功能化 M(3)N@C(80)材料的支架。通过 HPLC 检测到两种单加成异构体（[6,6]-和[5,6]-加成物）的形成，并通过 NMR 和可见/近红外光谱学进行了鉴定。在与 M(3)N@C(80)的每个 Prato 反应中，初始加成得到 I(h)-C(80)笼的[6,6]-加成物，随后通过重排反应完全或部分热异构化得到[5,6]-加成物。后者加成物的热转化反应速率取决于 C(80)内部金属簇的大小，有趣的是，在 Y(3)N@C(80)和 Gd(3)N@C(80)的反应中，这种转化首次被发现是可逆的。详细的动力学研究提供了 Lu(3)N@C(80)、Y(3)N@C(80)和 Gd(3)N@C(80)加成物反应的焓和熵垒。通过制备高度水溶性的 Gd(3)N@C(80)衍生物，证实了获得的 Prato 加成物的实用性。
