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General procedure for the synthesis of 1-bromo-2-chloro-4-methyl-5-nitrobenzene from 3-chloro-4-bromotoluene: Concentrated nitric acid (15 mL) was added slowly and dropwise to a solution of 1-bromo-2-chloro-4-methylbenzene (20 g, 100 mmol) in concentrated sulfuric acid (65 mL) at -20°C. The reaction was quenched by stirring for 5 minutes. The reaction mixture was stirred for 5 minutes and then poured into ice water (500 g) to quench the reaction. Subsequently, the mixture was filtered, the solid product was washed with water and dried to give the crude product as a yellow solid (23 g, 95% yield). The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δ 8.27 (s, 1H), 7.46 (s, 1H), 2.56 (s, 3H).

[1] Patent: WO2017/12576, 2017, A1. Location in patent: Page/Page column 332
[2] Patent: WO2009/27746, 2009, A1. Location in patent: Page/Page column 80
[3] Patent: WO2018/137593, 2018, A1. Location in patent: Page/Page column 83