Complexities of Regioselective Ring-Opening vs Transcarbonylation-Driven Structural Metamorphosis during Organocatalytic Polymerizations of Five-Membered Cyclic Carbonate Glucose Monomers
作者:Yidan Shen、Xin Yang、Yue Song、David K. Tran、Hai Wang、Jaye Wilson、Mei Dong、Mariela Vazquez、Guorong Sun、Karen L. Wooley
DOI:10.1021/jacsau.1c00545
日期:2022.2.28
Rigorous investigations of the organobase-catalyzed ring-opening polymerizations (ROPs) of a series of five-membered cyclic carbonate monomers derived from glucose revealed that competing transcarbonylation reactions scrambled the regiochemistries of the polycarbonate backbones. Regioirregular poly(2,3-α-d-glucose carbonate) backbone connectivities were afforded by 1,5,7-triazabicyclo[4.4.0]dec-5-ene
对一系列源自葡萄糖的五元环状碳酸酯单体的有机碱催化开环聚合(ROP)的严格研究表明,竞争的转羰基反应扰乱了聚碳酸酯主链的区域化学。区域不规则聚(2,3-α -d-葡萄糖碳酸酯)主链连接是由具有不同环状缩醛保护的三种单体的1,5,7-三氮杂双环[4.4.0]dec-5-烯(TBD)催化的ROP提供的通过4位和6位进行分组。对分离的单聚体和二聚体进行的小分子研究表明,当反应在室温下进行时,四面体中间体沿着加成-消除机制的途径倾向于 Cx-O2 与 Cx-O3 键断裂。此外,处理分离的 3-单聚体或 2-单聚体,在 3-位或 2-位分别具有从 Cx-O2 或 Cx-O3 键断裂获得的碳酸酯键,得到相同的 74:26 (3- unimer:2-unimer) 比例,证实了在室温下有机碱催化剂存在下,羰基转移反应的发生,优先形成 3-unimer 与 2-unimer。相比之下,-78°C 下的单聚体制备有利于