Synthesis of Central Chirality-Containing Triarylmethanols and Triarylmethyl Radicals with Extraordinarily Stable Configurations
Synthesis of Central Chirality-Containing Triarylmethanols and Triarylmethyl Radicals with Extraordinarily Stable Configurations
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具有非常稳定构型的含中心手性的三芳基甲醇和三芳基甲基自由基的合成
DOI：
10.1021/acs.joc.9b01675
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发表时间：
2019
影响因子：
3.6
通讯作者：
Liu Yangping
中科院分区：
文献类型：
--
作者：
Li Yingchun;Zhai Weixiang;Liao Yongfang;Nie Jiangping;Han Guifang;Song Yuguang;Li Shaoyong;Hou Jingli;Liu Yangping
三芳基甲醇具有螺旋桨状构象，具有右旋（P）或左旋（M）构型。本文通过在侧链上引入两个顺式羟基，得到了四个新的具有两个手性中心的三芳基甲醇立体异构体。这四个立体异构体很容易被分离成两对螺旋桨形的对映异构体的硅胶柱色谱法，如所示的NMR和X-射线晶体学研究。高效液相色谱（HPLC）研究表明，羟基轴承的三芳基甲醇的配置是更稳定的比bulkytert-butyl二甲基甲硅烷基保护的前体，不一致的一般策略，其中空间排斥是主要负责的构型稳定性。同样，两个羟基轴承四硫代三芳基甲基（TAM）自由基也表现出优异的构型稳定性，因此可通过CS-HPLC分离成四个立体异构体。有趣的是，三芳基的螺旋手性（MorP）和侧链的中心手性（RandS）对它们的电子顺磁共振性质几乎没有影响。我们的研究提供了一种新的策略来构建构型稳定的三芳基化合物，并证明了TAM基团上的侧链是其结构修饰的一个新位点。
Triarylmethanol adopts a propeller-shaped conformation with either right-handed (P) or left-handed (M) configuration. Herein, new triarylmethanols with two chiral centers were obtained via introduction of twocis-hydroxyl groups on the side chains, affording four stereoisomers. These four stereoisomers were easily separated by silica gel column chromatography into two pairs of propeller-shaped enantiomers, as shown by NMR and X-ray crystallographic studies. High-performance liquid chromatography (HPLC) studies showed that the configurations of the hydroxyl-bearing triarylmethanols are much more stable than those of the bulkytert-butyldimethylsilyl-protected precursors, inconsistent with the general strategy in which the steric repulsion is largely responsible for the configurational stability. Similarly, two hydroxyl-bearing tetrathiatriarylmethyl (TAM) radicals also exhibit excellent configurational stability and are thus separable by CS-HPLC into four stereoisomers. Interestingly, both helical chirality from triaryl group (MorP) and central chirality (RandS) on the side chain have little effect on their electron paramagnetic resonance properties. Our present study provides a new strategy to construct configurationally stable triaryl compounds and demonstrates that the side chain on TAM radicals is a new site for their structural modifications.