Kinetic control in the synthesis of a Möbius tris ((ethynyl)[5] helicene) macrocycle using alkyne metathesis

X Jiang, JD Laffoon, D Chen… - Journal of the …, 2020 - ACS Publications
X Jiang, JD Laffoon, D Chen, S Pérez-Estrada, AS Danis, J Rodríguez-López
Journal of the American Chemical Society, 2020ACS Publications
The synthesis of conjugated Möbius molecules remains elusive since twisted and
macrocyclic structures are low-entropy species sporting their own synthetic challenges. Here
we report the synthesis of a Möbius macrocycle in 84% yield via alkyne metathesis of 2, 13-
bis (propynyl)[5] helicene. MALDI-MS, NMR spectroscopy, and X-ray diffraction indicated a
trimeric product of twofold symmetry with PPM/MMP configurations in the helicene subunits.
Alternatively, a threefold-symmetric PPP/MMM structure was determined by DFT calculations …
The synthesis of conjugated Möbius molecules remains elusive since twisted and macrocyclic structures are low-entropy species sporting their own synthetic challenges. Here we report the synthesis of a Möbius macrocycle in 84% yield via alkyne metathesis of 2,13-bis(propynyl)[5]helicene. MALDI-MS, NMR spectroscopy, and X-ray diffraction indicated a trimeric product of twofold symmetry with PPM/MMP configurations in the helicene subunits. Alternatively, a threefold-symmetric PPP/MMM structure was determined by DFT calculations to be more thermodynamically stable, illustrating remarkable kinetic selectivity for this alkyne metathesis cyclooligomerization. Computational studies provided insight into the kinetic selectivity, demonstrating a difference of 15.4 kcal/mol between the activation barriers for the PPM/MMP and PPP/MMM diastereodetermining steps. Computational (ACID and EDDB) and experimental (UV–vis and fluorescence spectroscopy and cyclic voltammetry) studies revealed weak conjugation between the alkyne and adjacent helicene groups as well as the lack of significant global aromaticity. Separation of the PPM and MMP enantiomers was achieved via chiral HPLC at the analytical scale.
ACS Publications
以上显示的是最相近的搜索结果。 查看全部搜索结果

Google学术搜索按钮

example.edu/paper.pdf
查找
获取 PDF 文件
引用
References