A new and highly efficient catalyst for the enantioselective Mukaiyama-Michael reaction between (E)-3-crotonoyl-1,3-oxazolidin-2-one and 2-trimethylsilyloxyfuran
A new and highly efficient catalyst for the enantioselective Mukaiyama-Michael reaction between (E)-3-crotonoyl-1,3-oxazolidin-2-one and 2-trimethylsilyloxyfuran
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DOI：
10.1016/s0040-4020(01)01055-9
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发表时间：
2001-12-17
期刊：
影响因子：
2.1
通讯作者：
Zema, M
中科院分区：
文献类型：
--
作者：
Desimoni, G;Faita, G;Zema, M
2-三甲基硅氧基呋喃与(E)-3-巴豆酰基-1，3-恶唑烷-2-酮之间的Mukaiyama-Michael反应被几种基于双(恶唑啉)或吡啶双(恶唑啉)手性配体和金属阳离子的光学活性配合物立体选择性催化。由新合成的2，6-bis[(4‘R，5’R)-diphenyl-1，3-oxazolin-2‘-yl]吡啶和Eu-Ⅲ、La-Ⅲ、Ce-IV三元化合物合成的催化剂效率很高：非对映选择性完全反，对映体选择性很好(从98%到99%)。用H-1和C-13核磁共振波谱研究了镧的络合物，从机理上揭示了活化底物-催化剂络合物的本质。根据这些结果和PYBOX与La(OTf)(3)络合物的晶体结构，提出了一个立体化学模型，合理地解释了5位取代基的关键作用，适当地放置在配位试剂的硅面上使其看不见。(C)2001爱思唯尔科学有限公司。保留所有权利。
The Mukaiyama-Michael reaction between 2-trimethylsilyloxyfuran and (E)-3-crotonoyl-1,3-oxazolidin-2-one has been stereoselectively catalysed by several optically active complexes based on bis(oxazoline) (box) or pyridine bis(oxazoline) (pybox) chiral ligands and metal cations. The catalysts derived from the newly synthesised 2,6-bis[(4'R,5'R)-diphenyl-1,3-oxazolin-2'-yl] pyridine and the triflates of Eu-III, La-III, Ce-IV were high ly efficient: the diastereoselectivity was entirely anti and the enantioselectivity was excellent (ranging from 98 to > 99%). A mechanistic insight into the nature of the activated substrate-catalyst complex was inferred studying the lanthanum complexes with H-1 and C-13 NMR spectroscopy. Based on these results and on the crystallographic structure of the complex between pybox and La(OTf)(3), a stereochemical model is proposed to rationalise the crucial role of the substituent in position 5, suitably placed to blind the Si-face of the coordinated reagent. (C) 2001 Elsevier Science Ltd. All rights reserved.