非手性调控主链构象的静态螺旋聚取代苯乙炔的合成及不对称催化性能

The helix is the central structural motif in biological macromolecules and is also the ubiquitous object in nature. In order to mimic biological helices and explore its potential applications in materials science, plenty of helical polymers have been synthesized and attracted much attentions of scientists, especially for poly(substituted phenylacetylene)s due to its unique properties. To the best of our knowledge, most of helical poly(substituted phenylacetylene)s were induced by chiral groups to form helical structures and used at least two kinds of chiral compounds to control helical main-chain conformation. Therefore, it is of great challenge to synthesis of a new type of static helical poly(substituted phenylacetylene)s without any chiral groups and with controllable helical main-chain conformation through achiral conditions, and further explore its applications. This study intends to introduce a new type of static helical poly(substituted phenylacetylene)s without any chiral groups and with controllable helical main-chain conformation through helical-sense-selective polymerization. Two opposite optically active polymers can be obtained through only changing achiral conditions of polymerization. Meanwhile, investigation of its asymmetric catalytic activity through introduction of imines or monophosphorus groups. The purpose of this study is not only laying the foundation for preparation of new polymer catalyst with alternative methods and strategies, but also creating new strategies for chirality-transfer from main-chain helical polymer to organic molecule.

具有螺旋结构的生物高分子在生命体系中普遍存在并扮演重要角色。为模拟生物螺旋结构并探索其应用，人工合成具有螺旋结构的聚合物已成为研究热点之一，其中螺旋苯乙炔由于其独特的性质而备受关注。目前，现有的螺旋苯乙炔的合成及主链调控方法通常需要通过多种手性基团参与来实现，然而不含有手性基团的静态螺旋聚乙炔的合成及非手性调控主链螺旋构象尤其具有挑战性，而且进一步拓展此类聚乙炔的应用亟待探索。本项目拟利用螺旋选择性聚合制备一类不含任何手性基团且主链构象可控的静态螺旋聚取代苯乙炔，通过对改变聚合条件中非手性因素的研究，实现调控新型静态螺旋聚合物主链螺旋构象，得到光学活性相反的聚合物。与此同时，将亚胺或单磷基团引入此类螺旋聚合物侧链考察其不对称催化性能。期望通过本项目的实施为新型手性聚合物催化剂的制备提供可借鉴的方法，同时发展一种将螺旋主链的宏观手性传递给小分子化合物的新型手性传递策略。

具有光学活性的螺旋聚合物已在异构体识别，不对称催化以及液晶材料等领域展现出独特的性质。合成螺旋构象可控且具有规整构象的螺旋聚合物并确立调控方法对手性传递过程中出现的翻转、放大等现象的理解认识具有重大意义。本研究重点研究了螺旋聚取代苯乙炔主链螺旋构象的调控方法及不对称催化性能。相关的内容与结果如下：1. 合成一系列新型的含有两个羟基的单取代苯乙炔单体，通过不对称诱导聚合构建出主链具有螺旋构象，侧链含有手性基团的单手螺旋聚苯乙炔，此螺旋聚合物在溶液状态下构象能够保持，并且当加入HMPA改变溶液极性时螺旋聚合物主链螺旋构象发生改变。通过调节HMPA的含量改变溶剂极性构筑了主链螺旋构象可发生可逆调控的聚取代苯乙炔手性开关；2.基于非手性苯乙炔单体我们发现了5种自发不对称聚合反应，反应过程中无任何外界化学或物理手性源，所得聚合物在溶液中显示出一定的光学活性。大量聚合反应统计结果表明所得聚合物的两种螺旋构象呈现出随机分布的趋势即所得两种构象的比例接近于1:1。同时探讨了5类聚合反应控制螺旋构象的方法3.基于羟基的上TBS保护基与脱TBS保护基策略，通过活性聚合与手性诱导结合的方法法构筑了主链同时具有cis-cisoidal和cis-transoidal多重复杂螺旋构象的单手螺旋聚取代苯乙炔。使用本方法克服了传统此类含双羟基聚合物无法进行活性聚合的劣势，首次利用活性聚合反应得到分子量分散度低，螺旋构象在溶剂中稳定的单手螺旋聚苯乙炔，并在此基础上构建出非均相固体催化剂，其结构与形貌已通过IR与SEM等手段进行表征。同时该催化剂可高效、高对映选择性的催化不对称双羰基烯烃与甲亚胺叶立德的独特的1,3-偶极[3+2]环加成反应、甲亚胺叶立德与MBH醋酸酯的不对称串联共轭加成-消除反应以及硅氢化合物的硅醚化反应并且催化剂具有良好的回收性能。