化学学报 ›› 2012, Vol. 70 ›› Issue (17): 1785-1790.DOI: 10.6023/A12070447 上一篇    下一篇

研究论文

手性氮氧-Ni(II)络合物催化三氟甲基酮酸酯的不对称羰基ene 反应

郑柯, 林丽丽, 冯小明   

  1. 四川大学化学学院 成都 610064
  • 投稿日期:2012-07-20 发布日期:2012-08-29
  • 通讯作者: 冯小明
  • 基金资助:

    项目受国家自然科学基金(Nos. 21021001, 20902060)和“973 计划”(No. 2010CB833300)资助.

Chiral N,N '-Dioxide-Ni(II) Complex Catalyzed Asymmetric Carbonyl-Ene Reaction of Ethyl Trifluoropyruvate

Zheng Ke, Lin Lili, Feng Xiaoming   

  1. College of Chemistry, Sichuan University, Chengdu 610064
  • Received:2012-07-20 Published:2012-08-29
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 21021001, 20902060) and Major Basic Research Program of China (No. 2010CB833300).

本工作对手性氮氧–镍络合物催化剂在不对称羰基ene 反应中的应用进行了深入研究, 通过对配体结构和反应条件的优化, 实现了三氟甲基酮酸酯的不对称羰基ene 反应. 实验发现, 氮氧配体的结构对反应对映选择性有很大影响, 其中酰胺结构中苯环2,6-位大位阻供电取代基对于反应立体选择性控制起着至关重要的作用. 该催化体系有广泛的底物普适性, 对一系列α-甲基烯烃都能得到高达80%~96%的收率和97%~>99% ee 的对映选择性. 同时, 通过对照实验以及对催化剂单晶结构的分析, 提出了可能的反应过渡态, 为该系列催化剂的拓展提供了基础.

关键词: 不对称催化, 手性氮氧金属络合物, ene 反应, 高烯丙基醇,

The optically active homoallylic alcohols are widespread in natural products and have been frequently used as convenient building blocks in organic synthesis. As one of the most efficient synthetic methods to obtain chiral homoallylic alcohols, the asymmetric ene reaction of carbonyl compounds has attracted significant attentions. N,N'-dioxide-amide compounds, which could be easily prepared from chiral amino acids, have been developed into a type of privileged ligand and organocatalyst in various asymmetric reactions. On the other hand, the fluoroorganic compounds are important building blocks for the total synthesis of complex natural products, pharmaceuticals, and plant pesticides due to the unique abilities of the fluorine atom to significantly modify their physicochemical and biological properties. In recent years, the interest of the pharmaceutical industry in trifluoromethyl-containing compounds has grown significantly. In this manuscript, a series of Ni(II)-N,N'-dioxide complexes have been investigated for the asymmetric carbonyl-ene reaction of ethyl trifluoropyruvate. It was found that the electronic and steric characteristics of substituents on the amide moieties of the ligand greatly affected the reaction outcomes. The catalyst L4 with bulky and electron-donating groups at the ortho positions of aniline generated perfect stereoinductive environment. And a wide range of alkenes, including aromatic and aliphatic alkenes, tolerated the reaction well under mild reaction conditions, giving the corresponding trifluoromethyl-substituted allyl alcohols in excellent enantioselectivities (in the range of 97%~>99% ee) with high yields (up to 96%). Furthermore, the X-ray structure of the ligand L4 and the catalyst L4-Ni(II) complex shed light on the stereocontrol of the reaction. A possible transition state has been proposed to explain the origin of activation and asymmetric inductivity.

Key words: asymmetric catalysis, chiral N,N'-dioxide-metal complexes, ene reaction, homoallylic alcohols, nickel