Synthesis
The general procedure for the synthesis of 2-chloro-7-nitroquinoxaline from 7-nitro-2(1H)-quinoxalinone was as follows: in a round-bottomed flask, 7-nitroquinoxalin-2-ol (12.73 g, 67 mmol) was dissolved in 20 mL of phosphorochloridic acid (POCl3), and the mixture was heated and refluxed for 3 hours. Upon completion of the reaction, the reaction mixture was quenched by slowly pouring it into a stirred ice-water mixture. Subsequently, the precipitate was collected by filtration and washed with cold water to give 13.43 g of red to cherry colored solid product in 96% yield. The melting point of the product was 183-186 °C (literature value: 185-189 °C). Analyzed by ATR/FTIR spectroscopy, the main absorption peaks were located at 3092, 3048, 1682, 1525, 1350 and 740 cm1. 1H NMR (200 MHz, DMSO-d6) δ: 9.22 (s, 1H, H3), 8.88 (d, 1H, J = 3.0 Hz, H8), 8.59 (dd, 1H, J = 2.0 , 9.0 Hz, H6), 8.39 (d, 1H, J = 9.0 Hz, H5).13C NMR (100 MHz, DMSO-d6) δ: 149.2, 148.8, 148.3, 142.8, 140.2, 130.9, 124.1, 123.9.DEPT-135 (100 MHz, DMSO-d6) δ : 148.8, 130.9, 124.1, 123.9. mass spectrometry analysis showed molecular ion peaks of 209.1 and 211.1.
References
[1] Journal of the Brazilian Chemical Society, 2017, vol. 28, # 10, p. 1874 - 1878
[2] Tetrahedron Letters, 1991, vol. 32, # 10, p. 1311 - 1314
[3] Journal of Medicinal Chemistry, 2016, vol. 59, # 13, p. 6169 - 6186
[4] Journal of Medicinal Chemistry, 2011, vol. 54, # 13, p. 4508 - 4522
