Asymmetric and Enantiomer-Selective Polymerization of Phenyl-2-pyridyl-o-tolylmethyl Methacrylate
Asymmetric and Enantiomer-Selective Polymerization of Phenyl-2-pyridyl-o-tolylmethyl Methacrylate
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甲基丙烯酸苯基-2-吡啶基-邻甲苯基甲酯的不对称和对映体选择性聚合
DOI：
10.1295/polymj.19.897
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
K. Hatada
中科院分区：
文献类型：
--
作者：
E. Yashima;Y. Okamoto;K. Hatada
研究了手性阴离子引发剂2，3-二甲氧基-1，4-二（二甲氨基）丁烷（DDB）与芴基锂或N，N′-二苯基乙二胺单锂酰胺的配合物在甲苯中于−78°C下对大体积外消旋单体甲基丙烯酸苯基-2-吡啶基邻甲苯基甲酯（PPyTMA）的对映体选择性聚合。当（−）-DDB用作手性配体时，（−）-异构体优先于（+）-异构体被消耗，并且获得高度全同立构的聚合物。引发剂在较小体积的外消旋甲基丙烯酸酯（如甲基丙烯酸1-苯乙酯和甲基丙烯酸1，2-二苯基乙酯）的聚合中没有表现出对映体选择性，这提供了无规聚合物。对映体选择性随着转化率增加至约25%。e.e.在约25%转化率的阶段，聚合单体的转化率接近100%。这归因于高度全同立构聚（PPyTMA）在聚合早期阶段的刚性单手螺旋构象。在与甲基丙烯酸三苯甲酯（TrMA）的不对称共聚中，选择性没有降低，但在与体积较小的甲基丙烯酸酯的共聚中，选择性大大降低。前者形成共全同立构聚合物，后者形成无规立构共聚物。
The enantiomer-selective (asymmetric selective or stereoelective) polymerization of a bulky racemic monomer phenyl-2-pyridyl-o-tolylmethyl methacrylate (PPyTMA) was investigated with chiral anionic initiators, the complexes of 2,3-dimethoxy-1,4-bis(dimethylamino)butane (DDB) with fluorenyllithium or N,N′-diphenylethylenediamine monolithium amide, in toluene at −78°C. (−)-Isomer was consumed preferentially over (+)-isomer when (−)-DDB was used as a chiral ligand and a highly isotactic polymer was obtained. The initiators showed no enantiomer selectivity in the polymerization of less bulky racemic methacrylates, such as 1-phenylethyl methacrylate and 1,2-diphenylethyl methacrylate which afforded atactic polymers. Enantiomer selectivity increased with conversion up to about 25%. The e.e. of the polymerized monomer at a stage of about 25% conversion was nearly 100%. This was ascribed to a rigid one-handed helical conformation of highly isotactic poly(PPyTMA) at the early stage of the polymerization. The selectivity did not decrease in the asymmetric copolymerization with tri-phenylmethyl methacrylate (TrMA), but greatly decreased in the copolymerization with the less bulky methacrylates. The former copolymerization formed a coisotactic polymer and the latter atactic copolymers.