Dynamic ligand exchange of the lanthanide complex leading to structural and functional transformation: One-pot sequential catalytic asymmetric epoxidation-regioselective epoxide-opening process
Dynamic ligand exchange of the lanthanide complex leading to structural and functional transformation: One-pot sequential catalytic asymmetric epoxidation-regioselective epoxide-opening process
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DOI：
10.1021/ja043770
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发表时间：
2005-02-23
影响因子：
15
通讯作者：
Shibasaki, M
中科院分区：
文献类型：
--
作者：
Tosaki, SY;Tsuji, R;Shibasaki, M
本文描述了稀土络合物的特性，它易于发生动态的配体交换，并可在原位改变其结构和功能。在Sm-(S)-联苯醚-Ph3As=O(1：1：1)络合物1(2-10mol%)的催化下，各种a，β-不饱和酰胺2催化不对称环氧化反应完成后，直接向反应混合物中加入Me3SiN3，可在室温下平滑地打开环氧化合物，得到相应的反-β-叠氮-α-羟基酰胺4，总收率高达99%，区域选择性完全，对映体过量(高达99%)。连续过程成功的关键是通过动态配体交换原位生成高活性的叠氮化钐配合物。原位红外光谱和其他实验提供了强有力的证据，证明生成了Samariurn叠氮化物络合物。此外，酰胺部分相对较高的Lewis碱度对环氧化反应和环氧化物开环反应的高活性起到了关键作用。还描述了其他亲核试剂，如硫或碳的亲核剂的检查，以及环氧化物开环产物的转化。
The characteristic property of the lanthanide complex, which easily undergoes a dynamic ligand exchange and alters its structure and function in situ, is described. After the completion of the catalytic asymmetric epoxidation of various a,beta-unsaturated amides 2 in the presence of the Sm-(S)-BINOL-Ph3As=O (1:1:1) complex 1 (2-10 mol %), the addition of Me3SiN3 directly to the reaction mixture led to smooth epoxide-opening at room temperature, affording the corresponding anti-beta-azido-alpha-hydroxyamide 4 in excellent overall yield (up to 99%) with complete regioselectivity and excellent enantiomeric excess (up to >99%). The key to the success of the sequential process was the in situ generation of the highly reactive samarium azide complex through dynamic ligand exchange. In situ IR spectroscopy and other experiments provided strong evidence that the samariurn azide complex was generated. In addition, the relatively high Lewis basicity of the amide moiety had a key role in the high reactivity of both the epoxidation and the epoxide-opening reactions. Examinations of other nucleophiles such as sulfur or carbon nucleophiles as well as transformations of epoxide-opened products are also described.