Gao Cong, Li Dongying, Xie Aiting, Lyu Yanchao, Sun Qingqing, Han Jie, Guo Rong
School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, Jiangsu 225002, China.
Henan Institute of Chemistry, Henan Academy of Sciences, No. 56 Hongzhuan Road, Zhengzhou 450003, China.
Langmuir. 2024 Dec 17;40(50):26771-26778. doi: 10.1021/acs.langmuir.4c04060. Epub 2024 Dec 2.
Rational control over the morphologies of supramolecular assemblies for asymmetric catalysis with enhanced enantioselectivity represents a pivotal challenge in the realm of synthetic chemistry and material technology. Herein, Cu(II) ion-mediated supramolecular nanostructures assembled from chiral amino acid-based amphiphiles (l/d-AlaC) are fabricated as chiral catalysts for Diels-Alder cycloaddition between aza-chalcone and cyclopentadiene. In particular, compared with the supramolecular nanosheet formed by l/d-AlaC without Cu(II) ions, we found that the l/d-alanine chiral amphiphile can form supramolecular nanotubes with a multilayer structure and with the thickness of the tubular wall about 15 nm through the transition from a nanoribbon to tubular structure in the presence of Cu(II) ions. Consequently, the catalytic enantioselectivity of Diels-Alder was improved from 6% (nanosheet) to 49% (nanotube), attributed to the curved surface of the nanotube structure, which provides a preferential chiral environment and high density of the catalytic center to favor the chirality transfer. Our study presented in this work offers valuable insights for designing chiral supramolecular catalysts with a higher enantioselectivity driven by a metal ions-mediated nanostructure.
合理控制超分子组装体的形态以实现具有增强对映选择性的不对称催化，是合成化学和材料技术领域的一项关键挑战。在此，由基于手性氨基酸的两亲分子（l/d-AlaC）组装而成的铜（II）离子介导的超分子纳米结构被制备为氮杂查尔酮与环戊二烯之间狄尔斯-阿尔德环加成反应的手性催化剂。特别是，与无铜（II）离子时由l/d-AlaC形成的超分子纳米片相比，我们发现l/d-丙氨酸手性两亲分子在铜（II）离子存在下可通过从纳米带向管状结构的转变形成具有多层结构且管壁厚度约为15 nm的超分子纳米管。因此，狄尔斯-阿尔德反应的催化对映选择性从6%（纳米片）提高到了49%（纳米管），这归因于纳米管结构的曲面，其提供了优先的手性环境和高密度的催化中心以利于手性转移。我们在这项工作中展示的研究为设计由金属离子介导的纳米结构驱动的具有更高对映选择性的手性超分子催化剂提供了有价值的见解。
