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General procedure for the synthesis of 1-chloro-2-fluoro-4-methoxy-5-nitrobenzene from 4-chloro-3-fluoroanisole: To a concentrated mixture of 1-chloro-2-fluoro-4-methoxybenzene (5.00 g, 31.1 mmol), concentrated H2SO4 (30 mL) was slowly added at 0-10 °C. Potassium nitrate (3.78 g, 37.4 mmol) was then added in batches and the reaction mixture was kept stirred at 0 °C for 2 hours. Upon completion of the reaction, the reaction was quenched with ice water and the solid product was collected by filtration. The resulting solid was purified by recrystallization from hexane to afford 4.50 g (70% yield) of the target compound 1-chloro-2-fluoro-4-methoxy-5-nitrobenzene. The structure of the product was confirmed by 1HNMR (400 MHz, DMSO-d6): δ 8.30 (d, J=2.0 Hz, 1H), 7.61 (d, J=2.3 Hz, 1H), 3.96 (s, 3H); ESI-MS (m/z) 205.76 (MH)+.

[1] Patent: WO2014/22349, 2014, A1. Location in patent: Paragraph 00194
[2] Patent: WO2018/20474, 2018, A1. Location in patent: Page/Page column 155