Chinese Journal of Catalysis ›› 2018, Vol. 39 ›› Issue (11): 1746-1752.DOI: 10.1016/S1872-2067(18)63151-1

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Unsupported nanoporous palladium-catalyzed chemoselective hydrogenation of quinolines:Heterolytic cleavage of H2 molecule

Ye Lua, Yoshinori Yamamotoa,b,c, Abdulrahman I. Almansourd, Natarajan Arumugamd, Raju Suresh Kumard, Ming Baoa   

  1. a State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116023, Liaoning, China;
    b Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan;
    c Research Organization of Science and Technology, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan;
    d Department of Chemistry, College of Sciences, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia
  • Received:2018-06-26 Revised:2018-07-29 Online:2018-11-18 Published:2018-09-01
  • Contact: 10.1016/S1872-2067(18)63151-1
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21573032, 21773021), the Fundamental Research Funds for the Central Universities (DUT17ZD212), and the International Scientific Partnership Program ISPP at King Saud University for funding this research work through ISPP#0048.

Abstract:

An efficient and highly chemoselective heterogeneous catalyst system for quinoline hydrogenation was developed using unsupported nanoporous palladium (PdNPore). The PdNPore-catalyzed chemoselective hydrogenation of quinoline proceeded smoothly under mild reaction conditions (low H2 pressure and temperature) to yield 1,2,3,4-tetrahydroquinolines (py-THQs) in satisfactory to excellent yields. Various synthetically useful functional groups, such as halogen, hydroxyl, formyl, ethoxycarbonyl, and aminocarbonyl groups, remained intact during the quinoline hydrogenation. No palladium was leached from PdNPore during the hydrogenation reaction. Moreover, the catalyst was easily recovered and reused without any loss of catalytic activity. The results of kinetic, deuterium-hydrogen exchange, and deuterium-labeling experiments indicated that the present hydrogenation involves heterolytic H2 splitting on the surface of the catalyst.

Key words: Nanoporous materials, Palladium, Quinolines, Chemoselective hydrogenation, Heterogeneous catalyst