A modified preparation procedure for carbon nanotube-confined Nd/Na heterobimetallic catalyst for anti-selective catalytic asymmetric nitroaldol reactions.
A modified preparation procedure for carbon nanotube-confined Nd/Na heterobimetallic catalyst for anti-selective catalytic asymmetric nitroaldol reactions.
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DOI：
10.1021/jo402042s
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发表时间：
2013-11
期刊：
影响因子：
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通讯作者：
D. Sureshkumar;Kazuki Hashimoto;N. Kumagai;M. Shibasaki
中科院分区：
文献类型：
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作者：
D. Sureshkumar;Kazuki Hashimoto;N. Kumagai;M. Shibasaki
在迄今为止开发的大量不对称催化剂中，可回收的不对称金属基催化剂是罕见的实体。最近，我们发现，自组装金属基不对称催化剂和多壁碳纳米管（MWNTs）的组合产生了一种高活性和可回收的催化剂，其中催化活性的金属络合物分散在MWNTs网络中。在此，我们描述了一种改进的制备方法以及限制在MWNT中的Nd/Na杂双金属配合物的全部细节。促进自组装的催化剂与MWNTs避免了牺牲使用过量的手性配体形成的杂环配合物，提高了负载率的催化剂组分。将85%的催化剂组分引入到MWNTs上以产生受限催化剂，这是一种高效且可回收的反选择性不对称硝基醛醇反应催化剂。总结了制备催化剂以获得可重复的催化性能所需的注意事项。在光学活性的1，2-硝基烷醇的合成中显示出优于不含MWNTs的原型催化剂的上级催化特性，所述光学活性的1，2-硝基烷醇是用于合成治疗剂的关键中间体。
A recyclable asymmetric metal-based catalyst is a rare entity among the vast collection of asymmetric catalysts developed so far. Recently we found that the combination of a self-assembling metal-based asymmetric catalyst and multiwalled carbon nanotubes (MWNTs) produced a highly active and recyclable catalyst in which the catalytically active metal complex was dispersed in the MWNT network. Herein we describe an improved preparation procedure and full details of a Nd/Na heterobimetallic complex confined in MWNTs. Facilitated self-assembly of the catalyst with MWNTs avoided the sacrificial use of excess chiral ligand for the formation of the heterobimetallic complex, improving the loading ratio of the catalyst components. Eighty-five percent of the catalyst components were incorporated onto MWNTs to produce the confined catalyst, which was a highly efficient and recyclable catalyst for the anti-selective asymmetric nitroaldol reaction. The requisite precautions for the catalyst preparation to elicit reproducible catalytic performance are summarized. Superior catalytic profiles over the prototype catalyst without MWNTs were revealed in the synthesis of optically active 1,2-nitroalkanols, which are key intermediates for the synthesis of therapeutics.