Enantioselective Synthesis of Endohedral Metallofullerenes

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• 作者：Koji Sawai ; Yuta Takano ; Marta Izquierdo ; Salvatore Filippone ; Nazario Mart铆n ; Zdenek Slanina ; Naomi Mizorogi ; Markus Waelchli ; Takahiro Tsuchiya ; Takeshi Akasaka ; Shigeru Nagase
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：November 9, 2011
• 年：2011
• 卷：133
• 期：44
• 页码：17746-17752
• 全文大小：987K
• 年卷期：v.133,no.44(November 9, 2011)
• ISSN：1520-5126

文摘

Endohedral metallofullerenes are promising materials in biomedical and material sciences. In particular, they are of interest as agents for magnetic resonance imaging (MRI), photovoltaic devices, and semimetallic components. The synthesis of chiral endofullerenes represents one step further in the potential use of these carbon allotropes; however, this step has not been addressed so far. In this regard, enantiopure endofullerenes are expected to open new avenues in fields in which chirality is a key issue. Here, the synthesis and characterization of the first chiral endohedral metallofullerenes, namely, chiral bis-adducts of La@C₇₂, are reported. Eight optically active isomers were obtained by enantioselective 1,3-dipolar cycloaddition of a N-metalated azomethine ylide onto a non-isolated-pentagon rule metallofullerene derivative, La@C₇₂(C₆H₃Cl₂), catalyzed by a copper chiral complex. The chiral bis-adducts of La@C₇₂, isolated by nonchiral HPLC, showed optical purities as high as 98% as revealed by the remarkable positive or negative Cotton effects observed in the circular dichroic spectra.