Asymmetric polymerization using chirally modified Lewis acid

光学活性合成聚合物引起了人们的广泛关注。在聚合物主链上产生良好控制的构型手性对于开发合成光学活性聚合物的新方法是非常必要的。出现了许多优异的不对称C-C键形成反应。因此，获得具有主链手性的光学活性聚合物的最有希望的方法之一是基于重复不对称C-C键形成反应的聚合。我们重点研究了两个重要的亲核加成反应，樱井-细井烯丙基化反应和Mukaiyama醛醇反应。这些反应是构建碳-碳键的有力方法，并有可能产生新的立体中心。在这项研究中，我们研究了基于重复烯丙基化和醛醇反应的新的不对称聚合。对于不对称烯丙基化聚合，我们制备了双烯丙基硅烷和二醛作为新单体。这些单体发生聚合得到相应的聚合物，这些聚合物具有独特的主链结构，包含羟基和外亚甲基。酒石酸衍生的手性（酰基）硼烷是不对称烯丙基化聚合的优良催化剂。利用手性（酰基）硼烷进行烯丙基硅烷与乙醛的模型反应表明，在不对称聚合过程中会产生高水平的不对称诱导。不对称Mukaiyama醛醇反应也可用于合成光学活性聚合物。我们制备了双（硅烯醇醚）、双（硅烯醛缩醛）和双（硅烯醛缩醛）作为不对称醛醇聚合的单体。这些单体与二醛在手性Lewis酸催化剂的存在下反应顺利，得到了光学活性的聚β-羟基羰基，其中最有效的手性催化剂是由n -磺酰化氨基酸和硼烷合成的恶唑硼烷酮。其中一些手性聚合物可以降解成低分子量的手性化合物，用手性高效液相色谱法分析了聚合过程中的不对称诱导作用。聚合过程中的不对称诱导与烯醇硅烷与醛的不对称反应模型中的不对称诱导几乎相同。少

Optically active synthetic polymers have attracted considerable attention. Generation of well-controlled configurational chirality in the polymer main chain is highly desired for development of new methodologies for the synthesis of optically active polymers. A number of excellent asymmetric C-C bond formation reactions have appeared. Thus, one of the most promising ways to obtain optically active polymers having main chain chirality is polymerization based on repetitive asymmetric C-C bond forming reactions. We have focused on two important nucleophilic addition reactions, Sakurai-Hosomi allylation and Mukaiyama aldol reaction. These reactions are powerful method for the construction of C-C bonds together with the possibility of creating a new stereogenic center. In this study we have investigated the new asymmetric polymerizations based on repetitive allylation and aldol reaction.For asymmetric allylation polymerization, we prepared bis (allylsilane) s and dialdehydes as new monomers … More . Polymerization of these monomers took place to give the corresponding polymers that have a unique main chain structure containing hydroxy and exo methylene groups. Chiral (acyloxy) borane derived from tartaric acid is an excellent catalyst for the asymmetric allylation polymerization. Model reaction between allylsilane and aldehyde using the chiral (acyloxy) borane revealed that high level of asymmetric induction would occur during asymmetric polymerization.Asymmetric Mukaiyama aldol reaction can be also applied to the synthesis of optically active polymers. We have prepared bis (silyl enol ether) s, bis (silyl ketene acetal), and bis (sily lketene thioacetal) s as monomers of asymmetric aldol polymerization. Reaction between these monomers and dialdehydes occurred smoothly in the presence of chiral Lewis acid catalyst to afford optically active poly (β-hydroxy carbonyl) s. One of the most efficient chiral catalyst is oxazaborolidinone derived from N-sulfonylated amino acid and borane. Some of these chiral polymers could be degraded to give a low-molecular-weight chiral compounds, which were analyzed by chiral HPLC to determine the asymmetric induction during polymerization. Asymmetric induction during polymerization is almost the same as that in the model asymmetric reaction between enolsilane and aldehyde. Less