芳香取代基结构对螺旋聚乙炔高效液相色谱手性固定相手性识别性能的影响

设计合成了3种源于脯氨酸的手性乙炔基单体——(S)-2-乙炔基-N-芳香胺基甲酰基吡咯烷. 在氯化降冰片二烯铑二聚体{Rh(nbd)Cl]₂}-三乙胺催化下, 3种单体被转化为相应的光学活性螺旋聚合物. 用高效液相色谱评估了3种聚合物作为手性固定相(CSPs)对9种底物的手性识别性能. 以正己烷/异丙醇(体积比9∶1)为流动相时, 3种聚合物对3对种氢键给体分子苯偶姻(α=1.35~1.44)、 三氟-1-(9-蒽基)乙醇(α=1.11~1.53)、 2,2′-二羟基-1,1′-联萘(α=1.09~1.11)及乙酰丙酮钴(α=1.84~2.38)表现出很好的手性识别能力; 当以正己烷为流动相时, 3种聚合物都能立体选择性地识别氢键给体分子2,2-二甲基-1-苯基-1-丙醇(α=1.12~1.22), 聚(S)-2-乙炔基-N-(2′-萘基胺基甲酰基)吡咯烷]能识别氢键受体分子2-苯基环己酮(α=1.11). 结合核磁共振波谱、 拉曼光谱、 旋光测试、 紫外吸收光谱和圆二色光谱及液相色谱等方法, 系统研究了芳香侧基结构与连接位置对聚合物螺旋构象和对映体选择性拆分能力的影响. 分子对接模拟结果表明, 1-萘基的空间位阻大于2-萘基且可促进形成更强的分子内氢键, 不利于大尺寸底物(如联萘酚)的手性拆分. 与苯基相比, 引入萘基有利于增强聚合物与底物间的π-π相互作用, 提高聚合物的立体选择性和手性识别能力.

Effect of Aromatic Substituent on Chiral Recognition of Helical Polyacetylene-based Chiral Stationary Phases for High-Performance Liquid Chromatography

Three proline-derived acetylene monomers，（S）-2-ethynyl-N-aromatic carbamoyl pyrrolidine， were synthesized and polymerized under the catalysis of （bicyclo［2.2.1］hepta-2，5-diene）chlororhodium（I） dimer and triethyeamine｛［Rh（nbd）Cl］₂-Et₃N｝. The chiral recognition ability of the resultant optically active helical polymers as chiral stationary phases（CSPs） toward nine substitutes was evaluated by high-performance liquid chromatography. These polymers displayed satisfactory enantioseparation ability for three hydrogen-bond（HB） donating molecules， benzoin（α=1.35—1.44）， 2，2，2-trifluoro-1-（9′-anthryl）ethanol（α=1.11—1.53）， and 1，1′-bi（2-naphthol）（α=1.09—1.11）， as well as cobalt（Ⅲ） acetylacetonate（α=1.84—2.38） when the mixture of hexane and isopropanol（volume ratio 9∶1） was used as the eluent. Whereas， when pure hexane was employed as the eluent， 2，2-dimethyl-1-phenyl-1-propanol（α=1.12—1.22） was stereoselectively discriminated by three polymers and 2-phenylcyclohexanone（α=1.11） by poly［（S）-2-ethynyl-N-（2′-naphthyl carbamoyl） pyrrolidine］. Based on NMR， Raman spectra， polarimetry， UV-Vis absorption and circular dichroism spectra， along with liquid chromatography， the correlations between aromatic structure and linking position with polymeric helical conformation as well as optical resolving power were investigated. Molecular docking results suggested that the 1-naphthyl group exhibited larger steric effect over 2-naphthyl group， and facilitated the formation of stronger intramolecular HBs， which impeded chiral discrimination toward giant racemates（such as 1，1′-binaphthyl-2，2′-diol）. Compared to phenyl， naphthyl favored the enantioselective π-π interactions between polymers and enantiomers， enhancing the selectivity of steric fit and chiral resolving power of CSPs.