Chinese Journal of Catalysis ›› 2015, Vol. 36 ›› Issue (1): 33-39.DOI: 10.1016/S1872-2067(14)60243-6

• Articles • Previous Articles     Next Articles

Highly selective partial dehydrogenation of tetrahydroisoquinolines using modified Pd/C

Yue Jia, Mu-Wang Chena, Lei Shia,b, Yong-Gui Zhoua   

  1. a Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    b State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, Liaoning, China
  • Received:2014-10-01 Revised:2014-11-03 Online:2014-12-31 Published:2014-12-31
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21202162) and the State Key Laboratory of Fine Chemicals (KF1110).

Abstract:

A highly selective procedure has been developed for the partial dehydrogenation of 1-substituted-1,2,3,4-tetrahydroisoquinolines over K3PO4·3H2O-modified Pd/C catalyst. This new method provides facile, atom-economical and environmentally friendly access to 1-substituted-3,4-dihydroisoquinolines without the need for stoichiometric amounts of harmful oxidants. The use of standard Pd/C as a catalyst for this process gave poor chemoselectivity. Pleasingly, the use of a K3PO4·3H2O-modified Pd/C catalyst promoted the partial dehydrogenation of 1-substituted-1,2,3,4-tetrahydroisoquinolines with excellent chemoselectivity by suppressing further dehydroaromatization. Furthermore, conducting the reaction under an atmosphere of oxygen led to further improvements in the chemoselectivity of the dehydrogenation, with the ratio of imine to isoquinoline reaching up to 32/1. The heterogenous Pd/C catalyst could also be recycled and reused at least three times with excellent conversion and chemoselectivity, demonstrating the significantly practical potential of this methodology.

Key words: Palladium on carbon, Partial dehydrogenation, Tetrahydroisoquinoline, Imine, Dehydroaromatization