Stereoselective cationic polymerization of vinyl ethers by easily and finely tunable titanium complexes prepared from tartrate-derived diols: isospecific polymerization and recognition of chiral side chains
Stereoselective cationic polymerization of vinyl ethers by easily and finely tunable titanium complexes prepared from tartrate-derived diols: isospecific polymerization and recognition of chiral side chains
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DOI：
10.1039/d0py00343c
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发表时间：
2020-05
影响因子：
4.6
通讯作者：
Hironobu Watanabe;Takuya Yamamoto;Arihiro Kanazawa;S. Aoshima
中科院分区：
文献类型：
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作者：
Hironobu Watanabe;Takuya Yamamoto;Arihiro Kanazawa;S. Aoshima
从天然丰富的酒石酸中提取的α，α,α ',α ' -四芳基-1,3-二恶唑烷-4,5-二甲醇（TADDOL）钛配合物，被证明是乙烯基醚（VEs）立体选择性阳离子聚合的高效催化剂。用TADDOL、TiCl4和异丁基VE单体简单混合制备的引发体系聚合制得等规聚（异丁基VE） （m = 90%）。正丙基VE （m = 83%）和2-苯乙基VE （m = 94%）的聚合也获得了较高的等规性。此外，手性TADDOLate钛催化剂还能识别VE上的手性悬垂基团，如龙脑基VE和薄荷基VE。从（R，R）-和（S，S）- taddols中得到了具有显著不同立体规则的聚合物，这表明在阳离子聚合中，VEs的手性悬垂基团可以与手性催化剂产生“匹配/不匹配”相互作用。钛中心、TADDOL取代基和单体结构最有可能对立体控制负责。这些定义明确的钛TADDOLates，可以用各种取代基简单而经济地制备，将为设计立体选择性阳离子聚合催化剂提供平台。
Titanium complexes of α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL), derived from naturally abundant tartaric acid, were demonstrated to function as highly effective catalysts for the stereoselective cationic polymerization of vinyl ethers (VEs). Isotactic poly(isobutyl VE) (m = 90%) was generated via polymerization using an initiating system prepared by simply mixing TADDOL, TiCl4, and isobutyl VE monomer. High isotacticity was also attained in the polymerization of other VEs, such as n-propyl VE (m = 83%) and 2-phenylethyl VE (m = 94%). In addition, the chiral titanium TADDOLate catalyst recognized chiral pendant groups on VEs such as bornyl VE and menthyl VE. Polymers with dramatically different stereoregularities were obtained from (R,R)- and (S,S)-TADDOLs, which indicates that the chiral pendant groups of the VEs can induce “match/mismatch” interactions with the chiral catalysts in this cationic polymerization. The titanium center, the TADDOL substituents, and the monomer structure were most likely responsible for the stereocontrol. These well-defined titanium TADDOLates, which can be prepared easily and economically with various substituents, will provide a platform for designing stereoselective cationic polymerization catalysts.