Organocatalytic Conjugate-Addition Polymerization of Linear and Cyclic Acrylic Monomers by N-Heterocyclic Carbenes: Mechanisms of Chain Initiation, Propagation, and Termination
作者:Yuetao Zhang、Meghan Schmitt、Laura Falivene、Lucia Caporaso、Luigi Cavallo、Eugene Y.-X. Chen
DOI:10.1021/ja4088677
日期:2013.11.27
experimental and theoretical/computational investigations into the mechanisms of chain initiation, propagation, and termination of the recently discovered N-heterocyclic carbene (NHC)-mediated organocatalytic conjugate-addition polymerization of acrylic monomers. The current study specifically focuses on three commonly used NHCs of vastly different nucleophilicity, 1,3-di-tert-butylimidazolin-2-ylidene
这一贡献全面介绍了对最近发现的 N-杂环卡宾 (NHC) 介导的丙烯酸单体有机催化共轭加成聚合的链引发、增长和终止机制的实验和理论/计算研究。目前的研究特别关注三种亲核性截然不同的常用 NHC,1,3-二叔丁基咪唑啉-2-亚基 (I(t)Bu)、1,3-二甲基咪唑啉-2-亚基 (IMes) 和1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene (TPT),以及两种代表性的丙烯酸单体,线性甲基丙烯酸甲酯 (MMA) 及其环状类似物,生物质-衍生的可再生 γ-甲基-α-亚甲基-γ-丁内酯 (MMBL)。对于 MMA,NHC 结构对它促进的三种类型的反应表现出极好的选择性:IMes 形成烯胺(单单体加成),TPT 形成二聚(尾对尾),I(t)Bu 聚合。对于 MMBL,所有三种 NHC 都不促进二聚化,而是聚合,聚合活性对 NHC 结构和溶剂极性高度敏感。因此,I(t)Bu