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

asymmetric polymerization of achiral methacrylates having bulky ester groups was achieved成功使用following chiral anionic initiators. Thus，we synthesized optically active t etramethylethylenediamine (tmeda) derivatives modified withc_2 -chiral substituents derived from tartaric acid having asymmetric carbons，或更多preferentially from atropisomeric biphenyls and binaphthyls.这些ligands都是complexedeffectively to various organolithium compounds. The resulting chiral complexes聚合triphenylmethyl methacrylate (TrMA) in toluene at -78 C. The produced polymers showed high opticalrotations owing to the helical conformation，which was formed with high stereosectivity through the polymerization. the rotation values andpolymers senses of the strongly depending upon the structures of the used ligands. Althoughreaher complicated stereochemical product/ligand correlations were observed他们被consistently explained in terms of the stereoelectronic interaction between the推广end of the polymer chain and the chiral ligand complexed to the counter lithium cation.一个最有效的ligands was a biphenyl-monosubstituted TMEDA. Its lithium complexes servedas effective initiators for the polymerization of不只是TrMA，但也有其2- pyridyl derivative。polymers produced quantitatively had almost pure one-handed heliciy，已经有有限的molecular weights as to be easily soluble in tetrahydrofuran. The opticallyactive and solvent-soluble polymers是用于HPLC的主要包装材料，在其他方面贪污,when less bulky methacrylates of methyl and benzyl alcohols were polymerized with the aboveinitiators, the produced isotactic polymers showed negligible rotations. From这个结果，we now consider that such poly(ester)s can't form helical conformation being enough stable insolutions。

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.