Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University Binhai New City, Fuzhou, 350507, China.
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.
Angew Chem Int Ed Engl. 2023 Jun 5;62(23):e202302266. doi: 10.1002/anie.202302266. Epub 2023 Apr 28.
Chiral shape-persistent molecular nanocarbons are promising chiroptical materials; their synthesis, however, remains a big challenge. Herein, we report the facile synthesis and chiral resolution of a double-stranded figure-eight carbon nanobelt 1 in which two [5]helicene units are fused together. Two synthetic routes were developed, and, in particular, a strategy involving Suzuki coupling-mediated macrocyclization followed by Bi(OTf) -catalyzed cyclization of vinyl ether turned out to be the most efficient. The structure of 1 was confirmed by X-ray crystallographic analysis. The isolated (P,P)- and (M,M)- enantiomers show persistent chiroptical properties with relatively large dissymmetric factors (|g |=5.4×10 and |g |=1.0×10 ), which can be explained by the effective electron delocalization along the fully conjugated belt and the unique D symmetry. 1 exhibits local aromatic character with a dominant structure containing eight Clar's aromatic sextet rings.
手性形状保持分子纳米碳是很有前途的手性光学材料；然而，它们的合成仍然是一个巨大的挑战。在此，我们报告了一种双链[8]字形碳纳米带 1 的简便合成和手性拆分，其中两个[5]螺旋芴单元融合在一起。开发了两种合成路线，特别是涉及 Suzuki 偶联介导的大环化，然后是 Bi(OTf)催化的乙烯基醚环化的策略被证明是最有效的。通过 X 射线晶体学分析确定了 1 的结构。分离得到的（P，P）-和（M，M）-对映体具有持久的手性光学性质，具有较大的不对称因子（|g|=5.4×10 和 |g|=1.0×10），这可以通过沿完全共轭带的有效电子离域和独特的 D 对称性来解释。1 表现出局部芳香特征，含有八个 Clar 的芳香六元环的主导结构。
