Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.
Chem Asian J. 2021 Nov 15;16(22):3599-3603. doi: 10.1002/asia.202100920. Epub 2021 Sep 12.
Exploiting noncovalent π-interactions particularly emerging anion-π interactions to drive efficient catalysis is fascinating. Even with exciting progresses, can anion-π activation operate in water remains elusive. Here we report the design, synthesis and catalytic studies of a class of water-soluble electron-deficient molecular cages and relevant aromatic slide compounds. The prism-like cages contain three divided, long, cationic aromatic walls which constitute three highly electron-deficient V-shape cavities. They were efficiently synthesized in two steps from a parent triformyl cage in gram-scale. Crystal structure showed the π-walls bind to the counter bromide through strong anion-π interactions. Just 5 mol% of cages were effective in catalyzing decarboxylative Aldol reactions of aldehydes and malonic acid half thioesters in water but not in organic solvents, showing a pronounced hydrophobic amplification effect. Meantime, a series of single π-slides resembling the π-wall of the cage performed equally well, while those lacking an extended π-surface were ineffective, highlighting the essential role of electron-deficient π-face on promoting the conversion.
利用非共价 π 相互作用，特别是新兴的阴离子-π 相互作用来驱动高效催化是很吸引人的。尽管已经取得了令人兴奋的进展，但阴离子-π 活化能否在水中进行仍然难以捉摸。在这里，我们报告了一类水溶性缺电子分子笼和相关芳香滑合物的设计、合成和催化研究。这些棱柱状的笼子包含三个分开的、长的、阳离子性的芳香壁，构成了三个高度缺电子的 V 形腔。它们可以从母体三醛基笼一步法在克级规模下高效合成。晶体结构表明，π 壁通过强阴离子-π 相互作用与抗衡溴化物结合。只需 5mol%的笼就可以有效地催化醛和丙二酸半硫酯的脱羧 Aldol 反应在水中进行，但在有机溶剂中不行，显示出明显的疏水性放大效应。同时，一系列类似于笼中π壁的单个π-滑动物同样表现良好，而那些没有扩展的π-表面的则无效，这突出了缺电子π-面在促进转化方面的重要作用。
