Chuang Shih-Ching, Islam Aminul, Huang Chih-Wei, Shih Huai-Ting, Cheng Chien-Hong
Department of Chemistry, Tsing Hua University, Hsinchu, Taiwan 300, ROC.
J Org Chem. 2003 May 16;68(10):3811-6. doi: 10.1021/jo030009u.
A novel acid-catalyzed ring expansion of methanofullerenes bearing an alpha-ylidic ester has been investigated. Treatment of dialkyl acetylenedicarboxylate and tricycloalkylphosphine with C(60) led to the isolation of a methanofullerene ylide after passing the reaction mixtures through a basic alumina column. If the reaction mixture was passed through a silica gel column, a cyclopentanofullerene was isolated instead. These new cyclopentanofullerenes consisted of a fused cyclopentanone ring bearing an alpha-hydroxy ester and a phosphonium ylide and were confirmed by their NMR, mass, and X-ray diffraction data. The cyclopentanofullerenes were formed by the ring expansion of the corresponding methanofullerenes in the presence of silica gel. The ring expansion also proceeded by treating methanofullerene with acetic acid in chloroform. On the other hand, the methanofullerenes from RO(2)CCCCO(2)R, PAr(3), and C(60) were stable in silica gel. However, upon heating with acetic acid at 50 degrees C, they underwent ring expansion and dephosphination to give cyclopentenofullerenes. An implicit vinyl cyclopropane ring expansion mechanism was proposed to account for this novel acid-catalyzed rearrangement.
对带有α-叶立德酯的甲烷富勒烯的新型酸催化扩环反应进行了研究。将二烷基乙炔二羧酸酯和三环烷基膦与C(60) 反应，反应混合物通过碱性氧化铝柱后得到一种甲烷富勒烯叶立德。如果反应混合物通过硅胶柱，则会分离出一种环戊烷富勒烯。这些新型环戊烷富勒烯由一个带有α-羟基酯的稠合环戊酮环和一个鏻叶立德组成，并通过它们的核磁共振、质谱和X射线衍射数据得到证实。环戊烷富勒烯是在硅胶存在下由相应的甲烷富勒烯扩环形成的。用乙酸在氯仿中处理甲烷富勒烯也会发生扩环反应。另一方面，由RO(2)CCCCO(2)R、PAr(3) 和C(60) 生成的甲烷富勒烯在硅胶中是稳定的。然而，在50℃下用乙酸加热时，它们会发生扩环和脱膦反应，生成环戊烯富勒烯。提出了一种隐含的乙烯基环丙烷扩环机理来解释这种新型酸催化重排反应。
