An organocatalyst system, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and ⁿBu₄NCl, was developed for the conversion of CO₂ and internal epoxides to the corresponding disubstituted cyclic carbonates under rather mild conditions (1–4 atm of CO₂ and 100–120 °C). Catalyst screening revealed that small Cl⁻ opens epoxide rings more effectively than larger Br⁻ and I⁻ do when used as the counter anion of ⁿBu₄N⁺, suggesting that the steric hindrance of the internal epoxides is a factor. A practical and economical alternative system, DBU and ⁿBuCl, is also presented.

中文翻译：

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由CO ₂与内部环氧化物之间的环加成反应制得的二取代碳酸酯的有机催化剂体系

开发了有机催化剂体系1,8-二氮杂双环[5.4.0]十一碳-7-烯（DBU）和ⁿ Bu ₄ NCl，用于在相当温和的条件下将CO ₂和内部环氧化物转化为相应的二取代的环状碳酸酯（ 1-4个大气压的CO ₂和100-120°C）。催化剂筛选揭示了小氯^-大于溴更有效地打开环氧化物的环^-和我^-作为抗衡阴离子不使用时^Ñ卜₄ Ñ ⁺，这表明内部环氧化物的空间位阻是一个因素。还提出了一种实用且经济的替代系统DBU和ⁿ BuCl。