Acta Chimica Sinica ›› 2014, Vol. 72 ›› Issue (7): 849-855.DOI: 10.6023/A14040314 Previous Articles     Next Articles

Special Issue: 不对称催化与合成



刘旭, 韩召斌, 王正, 丁奎岭   

  1. 中国科学院上海有机化学研究所 金属有机国家重点实验室 上海 200032
  • 投稿日期:2014-04-23 发布日期:2014-05-29
  • 通讯作者: 丁奎岭
  • 基金资助:
    项目受国家重点基础研究发展计划(973 计划)(No.2010CB833300)、国家自然科学基金(21121062和21232009)、中科院及上海市科委资助.

SpinPHOX/Ir(I) Catalyzed Asymmetric Hydrogenation of (E)-2-(hydroxymethyl)-3-Arylacrylic Acids

Liu Xu, Han Zhaobin, Wang Zheng, Ding Kuiling   

  1. State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032
  • Received:2014-04-23 Published:2014-05-29
  • Supported by:
    Project supported by the Major Basic Research Development Program of China (No. 2010CB833300), the National Natural Science Foundation of China (Nos. 21121062 and 21232009), the Chinese Academy of Sciences, and the Science and Technology Commission of Shanghai Municipality.

Optically active 3-aryl-2-hydroxymethylpropionoic acids are highly useful chiral building blocks for the preparation of some drugs, but so far their asymmetric syntheses are still plagued by modest enantioselectivity and/or limited substrate scope. In the present study, the SpinPHOX/Ir(I) complexes (S,S)-1c and (R,S)-1e have been demonstrated to be highly effective for the asymmetric hydrogenation of (E)-2-(hydroxymethyl)-3-arylacrylic acids, affording the corresponding optically active 3-aryl-2-hydroxymethylpropionoic acids in good to excellent enantiopurities (ee up to 95%). Catalyst screening and reaction optimization with (E)-2-(hydroxymethyl)-3-phenylacrylic acid 2a as the model substrate, revealed that the asymmetric hydrogenation was best conducted in dichloromethane at r.t. under 10 atm of hydrogen with (S,S)-1c as the catalyst, and the presence of 1 equiv. of a suitable organic base (such as triethylamine) was essential for full substrate conversion and excellent product enantioselectivity (94% ee). Evaluation of the substrate scope of the protocol was performed using various 2-hydroxymethyl cinnamic acid derivatives 2a2n with various substituents on the phenyl group. Full conversions and good to high ee values were obtained in most cases, irrespective of the electron-withdrawing or -donating nature of the substituent. Using complex (R,S)-1e as the catalyst under a slightly modified reaction conditions (50 atm H2, 40 ℃), several substrates were hydrogenated in excellent ee values but with the sense of chiral induction opposite to those obtained by using (S,S)-1c. The reaction can be readily scaled up to gram-scale with retention of enantioselectivity. Among the optically enriched hydrogenation products obtained from this procedure, (S)-3a, (R)-3a and (-)-3n can be used as chiral building blocks for the asymmetric synthesis of pharmaceuticals Alvimopan, Ecadotril, and Fasidotril, respectively. Using this protocol, various (E)-2-(hydroxymethyl)-3-arylacrylic acids could be readily hydrogenated in high optical purities, thus providing a facile access to both enantiomers of the chiral 3-aryl-2-hydroxymethylpropionoic acids as well as the relevant chiral drugs.

Key words: iridium(I), SpinPHOX ligands, asymmetric catalysis, hydrogenation, (E)-2-(hydroxymethyl)-3-arylacrylic acid, 2-hydroxymethyl-3-arylpropionic acid