Faculty of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China.
Department of Polymer Chemistry and Technology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
ACS Macro Lett. 2021 Jun 15;10(6):737-743. doi: 10.1021/acsmacrolett.1c00316. Epub 2021 May 28.
The synthesis of poly(ethylene oxide) (PEO) with amino end group, a key functionality for PEGylation, is a long-standing challenge. Multistep routes based on postmodification or covalent protection have been adopted to circumvent ethoxylation of the amino group by ethylene oxide (EO). Here, we report a noncovalent protection strategy for one-step synthesis of PEO amine. An amino (di)alcohol is mixed with a small amount of mild phosphazene base and excess triethylborane (EtB) before addition of EO. The complexation of the amino group with EtB guarantees that polymerization of EO occurs selectively from the hydroxyl group through the bicomponent metal-free catalysis. Simply by precipitation in diethyl ether, the protective EtB as well as the catalyst can be removed to afford α-amino-ω-hydroxyl PEO with controlled molar mass, low dispersity, and complete end functionality. The effect of initiator structure and retention of EtB on the storage (oxidative) stability of PEO amine is also revealed.
聚环氧乙烷（PEO）的氨基封端基合成是聚乙二醇化的关键功能，这是一个长期存在的挑战。多步路线基于后修饰或共价保护，以避免环氧乙烷（EO）对氨基的乙氧基化。在这里，我们报告了一种非共价保护策略，用于一步合成 PEO 胺。将氨基（二）醇与少量温和的磷杂环戊二烯碱和过量的三乙基硼（EtB）混合，然后加入 EO。氨基与 EtB 的络合确保了 EO 的聚合选择性地从羟基通过双组分无金属催化进行。通过在乙醚中的沉淀，可除去保护 EtB 以及催化剂，从而得到具有受控摩尔质量、低分散度和完全端基功能的α-氨基-ω-羟基 PEO。还揭示了引发剂结构和 EtB 保留对 PEO 胺储存（氧化）稳定性的影响。
