Post-Functionalization of Supramolecular Polymers on Surface and the Chiral Assembly-Induced Enantioselective Reaction
Post-Functionalization of Supramolecular Polymers on Surface and the Chiral Assembly-Induced Enantioselective Reaction
复制标题
超分子聚合物表面后官能化及手性组装诱导的对映选择性反应
DOI：
10.1002/anie.202016395
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发表时间：
2021-04-07
影响因子：
16.6
通讯作者：
Liu, Pei-Nian
中科院分区：
文献类型：
--
作者：
Li, Deng-Yuan;Zhu, Ya-Cheng;Liu, Pei-Nian
尽管后官能化被广泛用于将不同的官能团引入溶液中的超分子聚合物（SP）中，但表面上的 SP 的后官能化仍未得到探索。在这里，我们通过 Au(111) 上的交叉偶联反应实现了源自 5,10,15-三-(4-吡啶基)-20-溴苯基卟啉 (Br-TPyP) 的两种 SP 的表面后功能化。由 Br-TPyP 预形成的梯形 Cu 配位 SP 通过与 4-乙烯基-1,1'-联苯的 Heck 反应进行功能化。在没有 Cu 的情况下，Br-TPyP 通过自组装形成两种对映异构体的手性 SP，并通过与 4-异氰基-1,1'-联苯 (ICBP) 的不同交叉偶联反应进行功能化。令人惊讶的是，该反应被发现是由 SP 的手性诱导的对映选择性表面反应。机理分析和DFT计算表明，在Br-TPyP脱溴和第一次ICBP加成后，由于空间位阻，第二步加成步骤中ICBP对手性SP中间体仅允许一个攻击方向，从而保证了反应的高对映选择性。
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.