Asymmetric polymerization using chirally modified Lewis acid

光学活性合成聚合物已经引起了相当大的关注。在聚合物主链中产生良好控制的构型手性对于开发用于合成光学活性聚合物的新方法是高度期望的。已经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前途的方法之一是基于重复的不对称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：Sakurai-Hosomi烯丙基化反应和Mukaiyama羟醛缩合反应。这些反应是构建C-C键的有力方法，并有可能产生新的立体中心。本论文研究了基于重复烯丙基化反应和Aldol反应的新型不对称聚合反应，在不对称烯丙基化反应中，我们合成了双烯丙基硅烷和二醛作为新的单体 ...更多信息 .这些单体的聚合反应发生，得到相应的聚合物，具有独特的主链结构，含有羟基和外亚甲基基团。酒石酸衍生的手性（酰氧基）硼烷是不对称烯丙基化聚合的优良催化剂。以手性（酰氧基）硼烷为催化剂的烯丙基硅烷与醛的模型反应表明，在不对称聚合过程中，不对称诱导作用显著，不对称Mukaiyama aldol反应也可应用于光学活性聚合物的合成。合成了双硅烯醇醚、双硅烯酮缩醛和双硅烯酮硫缩醛作为不对称羟醛聚合的单体。在手性刘易斯酸催化下，这些单体与二醛顺利反应，得到光学活性的聚β-羟基羰基化合物。其中最有效的手性催化剂是由N-磺酰化氨基酸和硼烷衍生的恶唑硼烷酮。这些手性聚合物中的一些可以降解得到低分子量的手性化合物，通过手性HPLC分析，以确定聚合过程中的不对称诱导。聚合过程中的不对称诱导与烯醇硅烷和醛之间的模型不对称反应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