Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (17): 1785-1790.DOI: 10.6023/A12070447 Previous Articles     Next Articles

Full Papers

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).

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