Pallova Lenka, Gauthier Etienne S, Abella Laura, Jean Marion, Vanthuyne Nicolas, Dorcet Vincent, Vendier Laure, Autschbach Jochen, Crassous Jeanne, Bastin Stéphanie, César Vincent
LCC-CNRS, Université de Toulouse, CNRS, 31077, Toulouse, France.
Institut des Sciences Chimiques de Rennes, UMR 6226, Institut de Physique de Rennes, UMR 6251, Campus de Beaulieu, CNRS-Université de Rennes 1, 35042, Rennes Cedex, France.
Chemistry. 2021 May 17;27(28):7722-7730. doi: 10.1002/chem.202100150. Epub 2021 Apr 30.
The straightforward, multigram-scale synthesis of the partially saturated H -fluoreno[n]helicenes (n=5 or 7) featuring a central, overcrowded alkene is described. The key cyclization step was based on an intramolecular McMurry reaction from the corresponding 1,5-diketones. Chiral stationary phase HPLC analysis and isomer separation indicate that each helicenic compound is constituted of three diastereoisomers at room temperature, i. e. the configurationally stable (R,R,P)/(S,S,M) pair of enantiomers and an apparently achiral compound resulting from the rapid interconversion between the (R,S,P) and (S,R,M) enantiomers. The partially saturated H -fluoreno[n]helicenes are oxidatively aromatized to give an efficient access to the corresponding fluoreno[n]helicenes. The chiroptical properties (vibrational and electronic circular dichroism) of the chiral, enantiopure compounds have been measured and analyzed by quantum-chemical calculations, confirming their helicoidal nature.
本文描述了一种直接的、多克规模的合成方法，用于合成具有中心拥挤烯烃的部分饱和H-芴并[n]螺旋烯（n = 5或7）。关键的环化步骤基于相应1,5-二酮的分子内麦克默里反应。手性固定相高效液相色谱分析和异构体分离表明，每种螺旋烯化合物在室温下由三种非对映异构体组成，即构型稳定的（R,R,P）/（S,S,M）对映体对以及由（R,S,P）和（S,R,M）对映体之间快速相互转化产生的明显非手性化合物。部分饱和的H-芴并[n]螺旋烯经氧化芳构化后可有效得到相应的芴并[n]螺旋烯。通过量子化学计算对手性对映体纯化合物的手性光学性质（振动和电子圆二色性）进行了测量和分析，证实了它们的螺旋结构性质。
