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Highly Asymmetric and Anionic Polymerizations of Achiral Methacrylate by Using Axially Chiral Ligands

使用轴向手性配体进行非手性甲基丙烯酸酯的高度不对称和阴离子聚合

基本信息

批准号：
61470105
负责人：
SUDA Hiroshi
金额：
$ 2.88万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

The asymmetric polymerization of achiral methacrylates having bulky ester groups was achieved successfully by using the following chiral anionic initiators. Thus, we synthesized optically active tetramethylethylenediamine (TMEDA) derivatives modified with C_2-chiral substituents derived from tartaric acid having asymmetric carbons, or more preferentially from atropisomeric biphenyls and binaphthyls. These ligands were complexed effectively to various organolithium compounds. The resulting chiral complexes polymerized triphenylmethyl methacrylate (TrMA) in toluene at -78゜C. The produced polymers showed high optical rotations owing to the helical conformation, which was formed with high stereosectivity through the polymerization. The rotation values and senses of the polymers were strongly depending upon the structures of the used ligands. Although reaher complicated stereochemical product/ligand correlations were observed, they were consistently explained in terms of the stereoelectronic interaction between the propagating end of the polymer chain and the chiral ligand complexed to the counter lithium cation. One of the most effective ligands was a biphenyl-monosubstituted TMEDA. Its lithium complexes served as effective initiators for the polymerization of not only TrMA but also its 2- pyridyl derivative. The polymers produced quantitatively had almost pure one-handed heliciy, and have so limited molecular weights as to be easily soluble in tetrahydrofuran. The optically active and solvent-soluble polymers were useful as chiral packing materials for HPLC. On the other hand, when less bulky methacrylates of methyl and benzyl alcohols were polymerized with the above initiators, the produced isotactic polymers showed negligible rotations. From this result, we now consider that such poly(ester)s can't form helical conformation being enough stable in solutions.

采用以下手性阴离子引发剂成功地实现了具有大体积酯基的非手性甲基丙烯酸酯的不对称聚合。因此，我们合成了具有光学活性的四甲基乙二胺（TMEDA）衍生物，其C_2-手性取代基来自具有不对称碳的酒石酸，或更优选来自阻转异构联苯和联萘。这些配体有效地配合到各种有机锂化合物。所得的手性复合物在甲苯中在-78 ° C下聚合甲基丙烯酸三苯基甲酯（TrMA）。所制备的聚合物显示出高的旋光度由于螺旋构象，这是通过聚合形成的高立体异构性。聚合物的旋光值和旋光方向强烈依赖于所用配体的结构。虽然reaher复杂的立体化学产品/配体的相关性进行了观察，他们始终解释的立体电子之间的相互作用的聚合物链的传播端和手性配体络合的抗衡锂阳离子。最有效的配体之一是联苯单取代的TMEDA。它的锂配合物作为有效的引发剂，不仅为TrMA的聚合，而且其2-吡啶衍生物。定量生产的聚合物具有几乎纯的单手螺旋性，并且具有如此有限的分子量以致于易于溶于四氢呋喃。该聚合物具有旋光活性和溶剂可溶性，可用作高效液相色谱手性填充材料。另一方面，当用上述引发剂聚合体积较小的甲醇和苄醇的甲基丙烯酸酯时，所产生的全同立构聚合物显示出可忽略的旋转。从这个结果，我们现在认为，这种聚酯不能形成螺旋构象是足够稳定的溶液中。