Mechanistic Insight into the Stereochemical Control of Lactide Polymerization by Salan-Aluminum Catalysts
Mechanistic Insight into the Stereochemical Control of Lactide Polymerization by Salan-Aluminum Catalysts
复制标题
DOI：
10.1002/anie.201503111
复制
发表时间：
2015-12-01
影响因子：
16.6
通讯作者：
Kol, Moshe
中科院分区：
文献类型：
--
作者：
Press, Konstantin;Goldberg, Israel;Kol, Moshe
围绕 2,2'-联吡咯烷核心组装的手性 Salan 配体的烷基铝配合物形成具有相同 N 供体构型的单一非对映体。添加苯甲醇后形成用于丙交酯聚合的活性催化剂。在外消旋丙交酯（rac-LA）聚合中，对映体铝物质之间的聚合基交换对聚乳酸（PLA）的立构规整度具有显着影响：未取代的萨兰配体的对映体纯催化剂产生全同立构PLA，而外消旋催化剂表现出较低的立体控制性。氯取代萨兰配体的对映体纯催化剂导致PLA具有轻微的杂规度倾向，而外消旋催化剂导致PLA遵循插入/自抑制/交换机制几乎完美的杂规度。
Alkyl aluminum complexes of chiral salan ligands assembled around the 2,2'-bipyrrolidine core form as single diastereomers that have identical configurations of the N donors. Active catalysts for the polymerization of lactide were formed upon the addition of benzyl alcohol. Polymeryl exchange between enantiomorphous aluminum species had a dramatic effect on the tacticity of the poly(lactic acid) (PLA) in the polymerization of racemic lactide (rac-LA): The enantiomerically pure catalyst of the nonsubstituted salan ligand led to isotactic PLA, and the racemic catalyst exhibited lower stereocontrol. The enantiomerically pure catalyst of the chloro-substituted salan ligand led to PLA with a slight tendency toward heterotacticity, whereas the racemic catalyst led to PLA of almost perfect heterotacticity following an insertion/auto-inhibition/exchange mechanism.