西班牙加泰罗尼亚化学研究所Pablo Ballester团队报道了极性超芳基扩展杯[4]吡咯容器存在下脂肪族双异腈的水解机制。相关研究成果于2021年2月17日发表在国际知名学术期刊《德国应用化学》。

该研究团队报道了八吡啶超芳基扩展杯[4]吡咯受体与中性双功能脂肪族客体在水中的结合研究。客体具有末端异腈基和甲酰胺基，从而配合物具有包合几何结构和1:1的化学计量比。通过¹H NMR滴定和ITC实验对配合物的热力学和动力学性质进行了表征。双异腈具有独立的反应基团，然而，在受体分子比例为1当量的情况下，水解反应产生非统计组成的混合物，反应速率显著降低。在双异腈具有5个亚甲基的间隔基的情况下，单甲酰胺产品的选择性明显增强。

动力学数据分析表明，所观察到的反应速率和选择性的改变与形成高度稳定的包合物有关，在包合物中异腈对水分子是隐藏的。通过与受体结合，反应底物在本体溶液中的浓度显著降低。反过来，异腈基在结合底物上的水解速率比在本体溶液中的慢。受体具有隔离和保护的双重作用。

附：英文原文

Title: Hydrolysis of Aliphatic Bis‐isonitriles in the Presence of a Polar Super Aryl‐Extended Calix[4]pyrrole Container

Author: Qingqing Sun, Luis Escobar, Pablo Ballester

Issue&Volume: 2021-02-17

Abstract: We report binding studies of an octa‐pyridinium super aryl‐extended calix[4]pyrrole receptor with neutral difunctional aliphatic guests in water. The guests have terminal isonitrile and formamide groups, and the complexes display an inclusion binding geometry and 1:1 stoichiometry. Using  1H NMR titrations and ITC experiments, we characterized the dissimilar thermodynamic and kinetic properties of the complexes. The  bis‐isonitriles possess independent reacting groups, however, in the presence of 1 equiv. of the receptor the hydrolysis reaction produces mixtures of non‐statistical composition and a significant decrease in reaction rates. The selectivity for the  mono‐formamide product is specially enhanced in the case of the  bis‐isonitrile having a spacer with five methylene groups. The analysis of the kinetic data suggests that the observed modifications in reaction rates and selectivity are related to the formation of highly stable inclusion complexes in which the isonitrile is hidden from bulk water molecules. The concentration of the reacting substrates in the bulk solution is substantially reduced by binding to the receptor. In turn, the hydrolysis rates of the isonitrile groups for the bound substrates are slower than in the bulk solution. The receptor acts as both a sequestering and supramolecular protecting group.

DOI: 10.1002/anie.202101499

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202101499