Synthesis of quinoxalines
Bioinspired ortho-quinone catalysts have been applied to oxidative synthesis of benzimidazoles, quinoxalines and benzoxazoles from primary amines in high yields under mild conditions with oxygen as the terminal oxidant.
R. Zhang, Y. Qin, L. Zhang, S. Luo, Org. Lett., 2017, 19, 5629-5632.
Aerobic oxidation of deoxybenzoins is efficiently catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) with air as the sole oxidant to give the corresponding benzils in excellent yields. The process has been successfully extended to a one-pot synthesis of quinoxalines from benzyl ketones and aromatic 1,2-diamines.
C. Qi, H. Jiang, L. Huang, Z. Chen, H. Chen, Synthesis, 2011, 387-396.
Copper-catalyzed condensation and C-N bond formation of 2-iodoanilenes, arylacetaldehydes, and sodium azide, in a one-pot three-component reaction enables the synthesis of quinoxalines in good yields. Under optimized reaction conditions, starting materials were reacted in the presence of CuI, K2CO3 in DMSO at 80°C for 20 hours.
H. Yuan, K. Li, Y. Chen, Y. Wang, J. Cui, B. Chen, Synlett, 2013, 24, 2315-2319.
A copper-catalyzed cycloamination of α-Csp3-H bond of N-aryl ketimines with sodium azide provides an efficient access to quinoxalines. The reaction features mild conditions and a broad functional group tolerance.
T. Chen, X. Chen, J. Wei, D. Lin, Y. Xie, W. Zeng, Org. Lett., 2016, 18, 2078-2081.
A convenient synthesis of substituted quinoxalines in good yields from o-phenylenediamines and ynones via Michael addition, dehydration condensation, and base-promoted C-α-CH2-extrusion under metal-free conditions features high regioselectivity, efficiency, and environmental friendliness.
J. Shen, X. Wang, X. Lin, Z. Yang, G. Cheng, X. Cui, Org. Lett., 2016, 18, 1378-1381.
One-pot two-step cyanide-mediated sequential reactions of ortho-phenylenediamines with aldehydes under aerobic oxidation conditions afford 2-aminoquinoxalines in high yields. Various substrates, including aliphatic aldehydes bearing acidic α-protons, are applicable.
Y.-H. Cho, K.-H. Kim, C.-H. Cheon, J. Org. Chem., 2014, 79, 901-907.
The combination of Pd/PTABS enables an exceptionally mild and highly efficient catalytic amination of chloroheteroarenes with secondary amines at ambient temperature.
S. S. M. Bandaru, S. Bhilare, N. Chrysochos, V. Gayakhe, I. Trentin, C. Schulzke, A. R. Kapdi, Org. Lett., 2018, 20, 473-476.