3,5-Dinitrobenzoic acid (5.0 g, 23.57 mmol) was added to a mixed solution of lithium methanolate (LiOMe, 3.6 g, 94.28 mmol) and hexamethylphosphorotriamine (HMPA, 100.0 mL) at room temperature. The reaction mixture was stirred at room temperature for 17 hours before being warmed to 80 °C to continue the reaction for 17 hours. Upon completion of the reaction, the mixture was cooled to room temperature and poured into a mixture of 6 M sulfuric acid (H2SO4) and ice water. Extraction was carried out with ether (Et2O) and the organic phase was washed sequentially with 1N hydrochloric acid (HCl) and saturated brine and dried over anhydrous sodium sulfate (Na2SO4). The organic phase was concentrated under reduced pressure to give a yellow solid 3-methoxy-5-nitrobenzoic acid (4.0 g, 86% yield). The product was characterized by 1H-NMR (300 MHz, DMSO-d6): δ13.76 (brs, 1H), 8.21 (m, 1H), 7.95 (t, 1H, J=2.7Hz), 7.82 (dd, 1H, J=2.7,1.1Hz), 3.94 (s, 3H).
