华东理工大学刘培念团队揭示了超分子聚合物表面后功能化及手性组装诱导的对映选择性反应机制。相关研究成果于2021年2月25日发表在《德国应用化学》。

尽管后功能化被广泛用于在溶液中向超分子聚合物（SPs）中引入不同的官能团，但表面上SPs的后功能化仍然没有被探索。

该文中，研究人员通过在Au（111）上的交叉偶联反应实现了5,10,15-三（4-吡啶基）-20-溴苯基卟啉（Br-TPyP）衍生的两种SP的表面后功能化。通过与4-乙烯基-1,1'-联苯的Heck反应，对由Br-TPyP制备的梯状铜配位SPs进行了功能化。在没有Cu的情况下，Br‐TPyP通过自组装形成手性SPs作为两种对映体，并通过与4-异氰基-1,1'-联苯（ICBP）的发散交叉偶联反应实现功能化。

令人惊讶的是，这一反应被发现是由SPs的手性诱导的对映选择性表面反应。机理分析和密度泛函理论计算表明，Br‐TPyP脱溴和第一次加成ICBP后，由于空间位阻的存在，第二次加成只允许ICBP对手性SP中间体的一个攻击方向，从而保证了反应的高对映选择性。

附：英文原文

Title: Post‐Functionalization of Supramolecular Polymers on Surface and the Chiral Assembly‐Induced Enantioselective Reaction

Author: Deng-Yuan Li, Ya-Cheng Zhu, Shi-Wen Li, Chen-Hui Shu, Pei Nian Liu

Issue&Volume: 2021-02-25

Abstract: Although post‐functionalization is extensively used to introduce diverse functional groups into supramolecular polymers (SPs) in solution, post–functionalization of SPs on surfaces still remains unexplored. Here we achieved the on‐surface post‐functionalization of two SPs derived from 5,10,15‐tri‐(4‐pyridyl)‐20‐bromophenyl porphyrin (Br‐TPyP) via cross‐coupling reactions on Au(111). The ladder‐shaped, Cu‐coordinated SPs preformed from Br‐TPyP were functionalized through Heck reaction with 4‐vinyl‐1,1'‐biphenyl. In the absence of Cu, Br‐TPyP formed chiral SPs as two enantiomers via self‐assembly, which were functionalized via divergent cross‐coupling reaction with 4‐isocyano‐1,1'‐biphenyl (ICBP). Surprisingly, this reaction was discovered as an enantioselective on‐surface reaction induced by the chirality of SPs. Mechanistic analysis and DFT calculations indicated that after debromination of Br‐TPyP and the first addition of ICBP, only one attack direction of ICBP to the chiral SP intermediate is permissive in the second addition step due to the steric hindrance, which guaranteed the high enantioselectivity of the reaction.

DOI: 10.1002/anie.202016395

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202016395