Chem. J. Chinese Universities ›› 2020, Vol. 41 ›› Issue (10): 2239.doi: 10.7503/cjcu20200333

• Article • Previous Articles     Next Articles

Synthesis of 1,2,3,4-Tetrahydroquinoxalines Through a One-pot Tandem Reaction Involving Cyclization and Hydrogenation of Imine and Amide Moieties

PAN Yixiao1, LI Yanwen1, HAN Jiahong1, ZHAO Haoqiang1, FENG Yu2, DING Xiangyuan1, XU Lijin1(), FAN Qinghua2(), SHI Qian3   

  1. 1.Department of Chemistry,Renmin University of China,Beijing 100872,China
    2.Institute of Chemistry,Chinese Academy of Sciences,Beijing 100190,China
    3.College of Chemistry and Materials Engineering,Wenzhou University,Wenzhou 325035,China
  • Received:2020-06-08 Online:2020-10-10 Published:2020-10-08
  • Contact: XU Lijin,FAN Qinghua E-mail:20050062@ruc.edu.cn;fanqh@iccas.ac.cn
  • Supported by:
    Supported by the National Natural Science Foundation of China(No. 21772238) and the Science and Technology Program of Guangzhou City, China(Nos. 201510010080, 201604016037).

Abstract:

Efficient synthesis of 1,2,3,4-tetrahydroquinoxalines from readily available 1,2-diaminobenzenes and α-ketoesters via a one-pot tandem process that combines cyclization and Ru-catalyzed hydrogenation of imine and amide moieties is reported. Using the catalyst consisting of in situ generated ruthenium/triphos complex and HBF4 co-catalyst, a range of structurally diverse 2-substituted 1,2,3,4-tetrahydroquinoxalines were prepared in good to excellent yields, and various functional groups including those are reduction-sensitive were well tolerated. The reaction could stop at 3,4-dihydroquinoxalin-2(1H)-one stage under a lower hydrogen pressure in the absence of any co-catalyst. Mechanistic studies revealed that the ruthenium catalyst works exclusively for the reduction of imine and amide moieties, and the choice of a Bronsted acid co-catalyst is crucial to the successful deoxygenative hydrogenation of amide moiety. It is believed that the activation of the amide moiety with the Bronsted acid co-catalyst is involved in the catalytic process.

Key words: Tetrahydroquinoxaline, Cyclization, Imine, Amide, Hydrogenation

CLC Number: 

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