有机化学 ›› 2023, Vol. 43 ›› Issue (1): 244-253.DOI: 10.6023/cjoc202206026 上一篇    下一篇

研究论文

轴向嫁接型温度响应性手性salen MnIII聚合物的制备及在纯水相烯烃不对称环氧化反应中的应用

韩彪a,b, 张瑶瑶a,*(), 陈舒晗a,b, 赵梦鸽a, 李楠a, 李维双a, 朱磊a,*()   

  1. a 湖北工程学院化学与材料科学学院 湖北孝感 432000
    b 湖北大学材料科学与工程学院 武汉 430062
  • 收稿日期:2022-06-16 修回日期:2022-08-01 发布日期:2022-08-25
  • 通讯作者: 张瑶瑶, 朱磊
  • 基金资助:
    湖北省教育厅中青年人才(Q20212704); 国家自然科学基金(22108065); 国家自然科学基金(21774029)

Preparation of Axially Grafted Temperature-Responsive Chiral Salen MnIII and Application in Asymmetric Epoxidation of Olefins in Water

Biao Hana,b, Yaoyao Zhanga(), Shuhan Chena,b, Mengge Zhaoa, Nan Lia, Weishuang Lia, Lei Zhua()   

  1. a School of Chemistry and Materials Science, Hubei Engineering University, Xiaogan, Hubei 432000
    b School of Materials Science and Engineering, Hubei University, Wuhan 430062
  • Received:2022-06-16 Revised:2022-08-01 Published:2022-08-25
  • Contact: Yaoyao Zhang, Lei Zhu
  • Supported by:
    Hubei Provincial Education Department Youth and Middle-Aged Talents Project(Q20212704); National Natural Science Foundation of China(22108065); National Natural Science Foundation of China(21774029)

以不同比例的N-异丙基丙烯酰胺(NIPAAm)和N,N-二甲基丙烯酰胺(DMAM)为反应单体, 偶氮二异丁腈为链引发剂, 巯基乙胺盐酸盐为链转移剂, 制备出一系列温度响应性聚合物(聚N-异丙基丙烯酰胺-co-N,N-二甲基丙烯酰胺, PNxDy). 再与传统手性salen MnIII配合物进行轴向嫁接, 得到多种形貌轴向嫁接型温度响应性手性salen MnIII聚合物PNxDyMn. 通过系列表征研究聚合物的温敏性、结构以及形貌, 并发现该类温度响应性手性聚合物在纯水相中, 能高效催化烯烃不对称环氧化反应的进行, 仅需0.5 mol% PN75D5Mn催化反应30 min, 即可以99%的收率、76%的对映选择性实现底物茚的转化, 转换频率(TOF)值高达396/h. 底物苯乙烯5 min转化率高达99%, TOF值为2376/h. 结合表征和实验, 证明PNxDyMn在水中可自组装形成纳米反应器, 限域效应加速了反应进行. 反应结束后, 升温至最低临界温度(LCST)以上, PNxDyMn表现出疏水特性, 从水相析出后回收并进行重复使用, 反应与分离过程中无需使用任何有机溶剂.

关键词: 轴向嫁接, 温度响应性, 手性salen MnIII配合物, 水相烯烃不对称环氧化, 回收及重复使用

A series of temperature-responsive polymers (poly N-isopropylacrylamide-co-N,N-dimethylacrylamide, PNxDy) were prepared by using N-isopropylacrylamide (NIPAAm) and N,N-dimethylacrylamide (DMAM) as reaction monomers, azobisisobutyronitrile as chain initiator, and mercaptoethylamine hydrochlorides as chain transfer agents. Then, a novel thermoresponsive surfactant-type chiral salen MnIII catalyst PNxDyMn was developed by axially grafting “smart” polymer (PNxDy) onto the metal center of a neat chiral salen MnIII complex. The temperature-sensitivity, structure and morphology of the polymers were studied through a series of characterizations, and it was found that these temperature-responsive chiral polymers can efficiently catalyze the asymmetric epoxidation of olefins in pure water. Only 0.5 mol% PN75D5Mn was sufficient to exhibit extremely high activity (conversion>99%) with up to 76% enantioselectivity and turnover frequency (TOF) (396/h) for a substrate of indene in water. The conversion rate of the substrate styrene was as high as 99% in 5 min, and the TOF value reached 2376/h. Characterization and experiments proved that PNxDyMn can self-assemble into nanoreactors for the asymmetric epoxidation of olefin in water, leading to an acceleration of reaction and causing selective effects. After reaction, the PNxDyMn exhibited hydrophobic properties upon heating above its lower critical solution temperature (LCST), and precipitated from the aqueous system for recovery. It can be recycled and reused for seven times without significant loss of activity, and no organic solvents were required for the reaction and separation process.

Key words: axial-grafting, temperature-responsive, chiral salen MnIII complex, asymmetric epoxidation of olefin in water, recycle and reuse