A simple and highly active catalytic process for ring-opening alternating copolymerization (ROAC) of cyclic anhydrides and epoxides still remains a key challenge. Herein, we have described an effective group of versatile and low-toxic zinc dicarbyl/amine Lewis pairs for the ROAC. The facile route showed a high catalytic activity (TOF ≤ 210 h⁻¹ at 110 °C) and perfectly alternating selectivity (>99%). An unexpected highly regioselective ring-opening of asymmetric epoxides (PO, ECH and SO) was also achieved by the combination of zinc alkyls (or aryls) and amines. Of note, deprotonation side reaction of α-H of anhydrides with organic bases was uncovered, and subsequently was inhibited by using nonpolar solvents and Lewis acid/base pairs. Thus, an array of polyesters was synthesized by the coupling of various anhydrides (PA, CHA, SA and NA) and epoxides (CHO, PO, ECH and SO) using the same Lewis pairs. Furthermore, variable temperature ¹H NMR spectral and MALDI TOF MS analyses were performed to understand the possible mechanism and microstructure. The experimental results indicated that zwitterionic alkoxide and carboxylate intermediates alternately formed to enhance the ester repeat units in chain initiation and propagation. This work provides a simple and green catalytic strategy to prepare diversified polyesters from the ROAC process of cyclic anhydrides and epoxides with considerable catalytic activity and alternating selectivity.

中文翻译：

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Lewis对用于环状酸酐和环氧化物的开环交替共聚

用于环酐和环氧化物的开环交替共聚（ROAC）的简单且高活性的催化方法仍然是关键的挑战。在本文中，我们描述了有效的一组通用且低毒的ROAC对二羰基/胺路易斯锌。简便的路线表现出高催化活性（TOF≤210 h ^-1在110°C下）和完美交替的选择性（> 99％）。通过烷基锌（或芳基）和胺的组合，还实现了意外的非对称环氧化物（PO，ECH和SO）的高度区域选择性开环。值得注意的是，未发现酸酐的α-H与有机碱的去质子化副反应，随后通过使用非极性溶剂和路易斯酸/碱对来抑制。因此，使用相同的路易斯对，通过将各种酸酐（PA，CHA，SA和NA）和环氧化物（CHO，PO，ECH和SO）偶联来合成一系列聚酯。此外，可变温度¹进行1 H NMR光谱和MALDI TOF MS分析，以了解可能的机理和微观结构。实验结果表明，两性离子醇盐和羧酸盐中间体交替形成，以增强链引发和扩散中的酯重复单元。这项工作提供了一种简单且绿色的催化策略，可通过ROAC环酐和环氧化物的ROAC工艺制备多样化的聚酯，并具有相当大的催化活性和交替选择性。