Li Li-Ping, Ye Bao-Hui
MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University , Guangzhou 510275, China.
Inorg Chem. 2017 Sep 5;56(17):10717-10723. doi: 10.1021/acs.inorgchem.7b01681. Epub 2017 Aug 15.
A three-component protocol involving enantiopure Δ-Ir(ppy)(MeCN) (ppy is 2-phenylpyridine) and salicylaldehyde as chiral auxiliaries was successfully applied to discriminate the absolute configuration and determine the enantiopurity of primary amines and amine alcohols via H NMR spectroscopy. The assembly reaction is rapid and quantitative, generating a pair of diastereomers that can be determined directly without physical separation. Single crystal structural analyses indicate that the shielding effects on the ligands imposed by a pair of diastereomers are different and generate sufficient resolution NMR signals for identification. The enhancement of stability via chelating coordination to Ir(III) ion and more than one pair of diastereotopic resonances in different detection regions of the three-component protocol ensure a high degree of accuracy in quantifying the ee value of chiral amines. The absolute errors in the ee determinations by H NMR spectroscopy in different detection windows are within 2.0%. The linear relationship between the experimentally measured ee values and the gravimetrically prepared samples is found to be excellent. This finding would provide a complementary method for the discrimination and determination of the enantiopurity of chiral primary amines and amine alcohols in the screening of asymmetric reactions.
一种包含对映体纯的Δ-Ir(ppy)(MeCN)（ppy为2-苯基吡啶）和水杨醛作为手性助剂的三组分方案，通过¹H NMR光谱成功应用于区分伯胺和胺醇的绝对构型并测定其对映体纯度。组装反应迅速且定量，生成一对无需物理分离即可直接测定的非对映异构体。单晶结构分析表明，一对非对映异构体对配体施加的屏蔽效应不同，并产生足够分辨率的NMR信号用于鉴定。通过与Ir(III)离子螯合配位提高稳定性以及三组分方案在不同检测区域中不止一对非对映异位共振，确保了在手性胺对映体过量值（ee值）定量方面的高度准确性。通过¹H NMR光谱在不同检测窗口中进行ee测定的绝对误差在2.0%以内。发现实验测量的ee值与重量法制备的样品之间的线性关系非常好。这一发现将为不对称反应筛选中手性伯胺和胺醇对映体纯度的区分和测定提供一种补充方法。
