The McMurry coupling of 2,7-diformylfluorene affords a dimer, anti-[2.2](2,7)-fluorenophanediene, and a trimer, [2.2.2](2,7)-fluorenophanetriene, as cyclic oligomers. X-Ray crystallography of the dimer establishes its strained, layered structure with anti-conformation. While the fluorenyl groups of the dimer do not show any sign of rotation in the variable temperature 1H NMR spectra up to 120 °C, those of the trimer are fast rotating even at −50 °C. Treatment of the dimer and trimer with KH in DMSO furnished the respective dianion and trianion that are stable at room temperature in the solutions. While the trianion shows substantial conjugation through the etheno bridges, the dianion shows little conjugation through the etheno bridges and almost no proton–deuterium exchange of the fluorenyl C9-H with the solvent DMSO-d6 probably due to stereospecific protonation–deprotonation associated with the tightly layered structure.
通过 2,7-二甲酰基
芴的麦克莫里偶联,得到了一种二聚体--反[2.2](2,7)-
芴二烯和一种三聚体--[2.2.2](2,7)-
芴三烯,它们是环状低聚物。二聚体的 X 射线晶体学研究确定了其具有反构象的应变分层结构。在高达 120 °C 的变温 1H NMR 光谱中,二聚体的
芴基团没有任何旋转迹象,而三聚体的
芴基团即使在 -50 °C 时也会快速旋转。在
二甲基亚砜中用 KH 处理二聚体和三聚体,可得到各自的二阴离子和三阴离子,它们在室温溶液中稳定存在。三阴离子通过
乙烯桥显示出大量的共轭作用,而二阴离子通过
乙烯桥显示出很少的共轭作用,
芴基 C9-H 与溶剂
DMSO-d6 几乎没有质子-
氘交换,这可能是由于与紧密分层结构相关的立体特异性质子化-质子交换所致。