Enantioselective resolution copolymerization of racemic internal epoxides with carbon dioxide (CO₂) is a challenging issue because of their poor reactivity and complicated regio/stereoselectivity. Herein, we describe the first enantioselective resolution copolymerization of racemic aromatic 2,3-disubstituted cis-epoxides and CO₂ using enantiopure dinuclear cobalt(III) complexes as catalyst under mild conditions, affording the corresponding polycarbonates with completely alternating structure and good enantioselectivity in the range of 70% to 97% ee. The isotactic polycarbonate from β-methylstyrene oxide is a typical semicrystalline material, possessing a melting point of 241 ^oC; while other isotactic-enriched copolymers from 2,3-disubstituted cis-epoxides bearing a substitute group on the aromatic ring are amorphous, having glass transition temperatures between 86 ^oC and 124 ^oC. Interestingly, the copolymer selectivity is correlated well with the Hammett substituent constant, and the highest polymer selectivity of 98% was found in the system using the epoxides bearing an electron-donating group on the benzene ring.

中文翻译：

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双核钴 (III) 催化剂介导的外消旋 2,3-二取代顺式环氧化物与 CO2 的对映选择性拆分共聚反应†

外消旋内环氧化物与二氧化碳 (CO ₂ ) 的对映选择性拆分共聚是一个具有挑战性的问题，因为它们的反应性差且区域/立体选择性复杂。在此，我们描述了在温和条件下使用对映纯双核钴 (III) 配合物作为催化剂，外消旋芳族 2,3-二取代顺式环氧化物和 CO ₂的首次对映选择性拆分共聚，得到了相应的具有完全交替结构和良好对映选择性的聚碳酸酯。 70% 到 97% ee 的范围。β-甲基氧化苯乙烯的全同立构聚碳酸酯是典型的半结晶材料，熔点为 241 ^oC; 而来自芳环上带有取代基的2,3-二取代顺式环氧化物的其他全同立构浓缩共聚物是无定形的，玻璃化转变温度介于 86 ^o C 和 124 ^o C之间。有趣的是，共聚物的选择性与 Hammett 相关性很好取代基常数，并且在使用苯环上带有给电子基团的环氧化物的体系中发现最高的聚合物选择性为 98%。