金鸡纳碱季铵盐促进的 CO2 与环氧化合物的不对称环加成反应

 开发了钴配合物/金鸡纳碱季铵盐催化剂体系用于催化 CO2 与环氧化合物的不对称环加成反应, 考察了催化剂和助催化剂中阴离子对反应的影响. 结果表明, 该反应可在 667 kPa CO2 压力和室温下进行. 催化剂中不同阴离子的活性次序为 2-硝基苯氧基 > 2,4,6-三硝基苯氧基 > NO3? > OAc? > 三氟乙酸根 ≈ B ? > Cl? >对甲苯磺酸根. 当助催化剂阴离子为 Cl?时反应的 ee 值较高, 而为 Br? 时反应速度较快. 当以 (S,S)-1,2-环己二胺缩 (N,N-双 (3,5-二-叔丁基水杨醛) 钴 (III) 乙酸盐 ((S,S)-A) 结合 N,O-二苄基氯化奎宁 (1a) 作助催化剂时, 得到了 ee 值为 73% 的手性丙烯环碳酸酯.

Cinchona-Derived Quaternary Ammonium Salts-Improved Asymmetric Cycloaddition of CO2 to Epoxides

A new catalyst system, SalenCoX/cinchona-derived quaternary ammonium salts, was developed to catalyze the cycloaddition of CO₂ to epoxides under extremely mild reaction conditions. Chiral propylene carbonate was obtained with good enantioselectivity in the presence of the catalyst. The anions of the catalysts and the cocatalysts evidently affect the activity and enantioselectivity of the reaction. The activity of (S,S)-catalysts in terms of anion is in the order 2-nitrophenoxy > 2,4,6-trinitrophenoxy > NO₃^- > OAc^- > CF₃CO₂^- ≈ Br^- > Cl^- > OTs^-. The cocatalyst with the Cl^- anion gives the highest ee value for propylene carbonate. In contrast, the cocatalyst with the Br^- anion has higher activity. When the catalyst (S,S)-(+)-1,2-cyclohexanediamino(N,N-bis(3,5-di-tert-butyl- salicylidene) cobalt(III) acetate ((S,S)-A) was combined with the cocatalyst N,O-dibenzylquininium chloride (1a) , it gives the highest 73% ee for propylene carbonate.