Biocompatible and biodegradable polyphosphoesters derived from the ring-opening polymerization (ROP) of phosphate esters have drawn increasing attention because of their potential applications in clinical and therapeutic fields. The related knowledge of the ROP mechanism, however, is very limited to date. Herein, the ROP of 2-isobutoxy-2-oxo-1,3,2-dioxaphospholane (iBP) catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or the combination of DBU/thiourea (TU, 1-[3,5-bis(trifluoromethyl)phenyl]-3-cyclohexylthiourea) was computationally studied. It is found that DBU plays the roles of both activating BnOH as an initiator and transporting protons in the two-component DBU/BnOH system. In the three-component (DBU/TU/BnOH) system, two possible mechanisms, viz., DBU- and TU-induced iBP ring-opening, were explored. In the former mechanism, DBU acts as a proton relay and TU is an activator of iBP, whereas protonated DBU serves as a counter cation and TU stabilizes an oxygen-containing anion via hydrogen bond interactions in the latter case. In comparison, the DBU/TU/BnOH cooperatively catalyzed ROP of iBP is more thermodynamically and kinetically favorable than that catalyzed by the two-component DBU/BnOH, which could be mainly ascribed to a more activated P–O bond in iBP by the dual activation role of TU.

中文翻译：

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DBU和TU协同诱导磷酸酯的开环聚合：机理研究

源自磷酸酯的开环聚合（ROP）的生物相容性和可生物降解的聚磷酸酯因其在临床和治疗领域的潜在应用而受到越来越多的关注。但是，到目前为止，ROP机制的相关知识非常有限。在此，由1,8-二氮杂双环[5.4.0]十一碳-7-烯（DBU）或DBU /硫脲的组合催化的2-异丁氧基-2-氧代-1,3,2-二氧杂膦烷（iBP）的ROP （TU，1- [3，5-双（三氟甲基）苯基] -3-环己基硫脲）进行了计算研究。发现在两个组分的DBU / BnOH体系中，DBU既起活化BnOH作为引发剂的作用，又起运输质子的作用。在三组件（DBU / TU / BnOH）系统中，有两种可能的机制，即。，探索了DBU和TU诱导的iBP开环。在前一种机制中，DBU充当质子中继，TU充当iBP的活化剂，而质子化的DBU充当抗衡阳离子，而TU则通过氢键相互作用稳定含氧阴离子。相比之下，DBU / TU / BnOH协同催化的iBP的ROP在热力学和动力学上比双组分DBU / BnOH催化的ROP更热力学和动力学上的优势，这主要归因于iBP中双键的P-O键更活化TU的激活作用。