Synthesis
70% nitric acid (19.5 mL, 437.4 mmol, 2.0 eq.) was slowly added dropwise to a suspension of glacial acetic acid (400 mL) of hydroquinone dibenzyl ether (63.5 g, 218.7 mmol, 1.0 eq.) at 0 °C. The reaction mixture was kept stirred at 0 °C for 3 hours. Subsequently, the reaction solution was poured into water (1500 mL) and the precipitate precipitated was collected by filtration. The precipitate was washed with water (1500 mL), dissolved in chloroform (300 mL), dried over magnesium sulfate, and concentrated under reduced pressure to give the nitro compound 1,4-dibenzyloxy-2-nitrobenzene (73.04 g, 100% yield) as a yellow solid. The melting point was 80-81 °C (literature value: 80-81 °C). NMR hydrogen spectrum (400 MHz, CDCl3) δ: 7.49 (1H, d, J=3.0 Hz, H-3), 7.46-7.30 (10H, m, OCH2Ph), 7.12 (1H, dd, J=9.2, 3.1 Hz, H-5), 7.05 (1H, d, J=9.2 Hz, H-6), 5.18 (2H, s, CH2), 5.05 (2H, s, CH2). NMR carbon spectrum (101 MHz, CDCl3) δ: 152.30 (C), 146.39 (C), 135.97 (C), 135.88 (C), 128.75 (CH), 128.70 (CH), 128.37 (CH), 128.22 (CH), 127.59 (CH), 127.15 (CH), 121.54 (CH), 117.24, 111.18 (CH), 72.10 (CH2), 70.94 (CH2). Infrared spectrum (ATR, cm-1): 1520 (NO2), 1497 (CAr-CAr), 1341 (NO2). Mass spectrum (ESI): m/z 358 [M+Na]+, 100%. High Resolution Mass Spectrometry (HRMS): measured value 358.1034, calculated value 356.1050 for C20H17NNaO4. Spectral data are in agreement with literature reports.
References
[1] Tetrahedron, 2015, vol. 71, # 51, p. 9571 - 9578
[2] Letters in Organic Chemistry, 2015, vol. 12, # 2, p. 129 - 135
[3] Helvetica Chimica Acta, 1982, vol. 65, # 8, p. 2645 - 2667
[4] Chemical Communications, 2013, vol. 49, # 66, p. 7313 - 7315
[5] Patent: CN108530242, 2018, A. Location in patent: Paragraph 0063-0065
