Co(NO3)2•6H2O/左乙拉西坦催化转化CO2

Co(NO3)2?6H2O/levetiracetam catalytic conversion of CO2

摘要:

环碳酸酯在聚合物及有机合成、锂电池等诸多领域得到了广泛应用，可由环氧化物与CO2反应得到。为更高效简洁合成环碳酸酯化合物，尚需开发高性能催化体系。六水合硝酸钴/左乙拉西坦L1耦合体系可高效催化环氧化物与CO2反应，合成系列环碳酸酯。以氧化苯乙烯与CO2反应为模版，用单变量方法对影响反应的因素进行优化，得到最佳条件为：氧化苯乙烯为1.0 mmol、CO2为0.1 MPa、六水合硝酸钴为0.05 mmol、左乙拉西坦为0.05 mmol、四丁基溴化铵（TBAB）为0.02 mmol、反应温度100 ℃、反应时间6 h。该方法还可用于苯丙炔酸、苯甲酸及2,4-喹唑啉二酮的合成。基于实验结果及参阅相关文献，提出了合理反应机理：L1可通过氢键及与钴盐配位形成络合物活化环氧化物，并于TBAB作用下生成易转化过渡态，进而与CO2反应，经分子内环化反应得到环碳酸酯。此方法不仅可实现环碳酸酯高效合成，还拓宽了药物应用范围。

Abstract:

Cyclic carbonates are widely used in numerous fields, such as polymers, organic synthesis, lithium batteries, and could be synthesized from epoxides and CO2. A series of cyclic carbonates were synthesized through the combined system of Co(NO3)2?6H2O and levetiracetam-catalyzed reaction between epoxides and CO2. After examining the reaction conditions via univariate experiments, the best conditions were showed as follows: styrene oxide (1 mmol), CO2 pressure 0.1 MPa, Co(NO3)2?6H2O (0.05 mmol), levetiracetam (0.1 mmol), TBAB (0.02 mol), 100 ℃, 6 h. This method could be also used to synthesize phenylpropiolic acid, benzoyleneurea and benzoic acid. Base on the results of experiments and referred to relevant literatures, the reaction mechanism was proposed: L1 activated epoxides through hydrogen bonding and coordinating with cobalt salts to form complexes, following to react with CO2 to from easily convertible transition state with the aid of TBAB, and providing cyclic carbonate through intramolecular cyclization. This method not only was efficiently used to prepare cyclic carbonate, but also expanded the scope of drug application.