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A. Synthesis of 3-nitro-4-methylphenylacetic acid To a dry dichloromethane solution of 4-methylphenylacetic acid (1.50 g, 10.0 mmol) was added dropwise fuming nitric acid (1.5 mL). The reaction mixture was stirred at room temperature for 2 h. The reaction was subsequently quenched with water. The reaction mixture was extracted with ethyl acetate and the organic phase was washed sequentially twice with water and once with brine. The organic layer was dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give 3-nitro-4-methylphenylacetic acid (1.66 g, 85% yield). The product was characterized as follows: 1H NMR (CDCl3) δ 7.91 (d, 1H), 7.42 (dd, 1H), 7.31 (d, 1H), 3.71 (s, 2H), 2.58 (s, 3H); ES-MS m/z 196 [M + H]+.

[1] Patent: US6593322, 2003, B1
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[3] Journal fuer Praktische Chemie (Leipzig), 1891, vol. <2> 44, p. 85
[4] Patent: WO2014/145022, 2014, A1. Location in patent: Page/Page column 52