Controlled cationic ring-opening polymerization of 1,3-oxazolidine-2-thione derived from L-serine
Controlled cationic ring-opening polymerization of 1,3-oxazolidine-2-thione derived from L-serine
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DOI：
10.1021/ma030320d
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发表时间：
2003-12-16
期刊：
影响因子：
5.5
通讯作者：
Endo, T
中科院分区：
文献类型：
--
作者：
Nagai, A;Miyagawa, T;Endo, T
研究了L-丝氨酸1，3-恶唑烷-2-酮衍生物（S-L）的阳离子开环聚合。以L-丝氨酸甲酯盐酸盐为原料，在三乙胺存在下，与二硫化碳、过氧化氢反应合成了丝氨酸内酯。使用三氟甲磺酸甲酯（TfOMe）、三氟甲磺酸（TfOH）和三氟化硼醚合物（BF3.OEt2）作为引发剂的阳离子聚合以定量产率得到具有聚硫氨酯结构的聚合物。所得聚合物显示出相对于单体的反转比旋光度，其中绝对值的大幅增加表明了高阶结构的可能性。聚合物的分子量由SL与TfOMe的进料比控制，并且其分布恒定地窄（M-w/M-n <1.14），支持聚合的受控特征。研究了TfOMe的反应机理。根据NMR光谱实验，与TfOMe的聚合通过活性链端机制进行，其中质子化的环状内亚氨基硫代碳酸酯2是活性物种。增长步骤涉及S-L对活性物质的亲核攻击。
The cationic ring-opening polymerization of a 1,3-oxazolidine-2-thione derivative (S-L) from L-serine was examined. SL was synthesized by the reaction of L-serine methyl ester hydrochloride with carbon disulfide and hydrogen peroxide in the presence of triethylamine. Cationic polymerizations using methyl trifluoromethanesulfonate (TfOMe), trifluoromethanesulfonic acid (TfOH), and boron trifluoride etherate (BF3.OEt2) as initiators gave polymers with polythiourethane structures in quantitative yields. The obtained polymers showed inverted specific rotations with respect to the monomer, where the large increase of the absolute values suggested the possibility of high-order structures. The molecular weight of the polymer was controlled by the feed ratio of SL to TfOMe and its distribution was constantly narrow (M-w/M-n < 1.14), supporting the controlled character of the polymerization. The reaction mechanism was examined for TfOMe. According to NMR spectroscopic experiments, the polymerization with TfOMe proceeds via an active chain end mechanism in which the protonated cyclic endo iminothiocarbonate 2 is the active species. The propagation step involves a nucleophilic attack of S-L to the active species.