General procedure for the synthesis of methyl 3-amino-5-bromo-4-methyl-4-methylbenzoate from methyl 3-bromo-4-methyl-5-nitrobenzoate: Methyl 3-bromo-4-methyl-5-nitrobenzoate (8.50 g, 31.0 mmol), acetic acid (20 mL), and tetrahydrofuran (170 mL) were added to a 500 mL single-necked flask, followed by batchwise addition of iron powder (8.68 g, 155 mmol). The reaction mixture was stirred at 75 °C for 12 hours. Upon completion of the reaction, the mixture was cooled to room temperature, filtered to remove insoluble solids and the filtrate was concentrated under vacuum. Water (500 mL) was added to the concentrated residue and extracted with ethyl acetate (100 mL × 2). The organic phases were combined, washed with saturated brine (100 mL), dried over anhydrous sodium sulfate, filtered and concentrated under vacuum. The residue was purified by silica gel column chromatography with the eluent of ethyl acetate/petroleum ether (v/v = 1/10) to afford methyl 3-amino-5-bromo-4-methylbenzoate as a light yellow solid (5.52 g, 73% yield). Mass spectrum (ESI-API, positive ion mode) m/z: 244.9 [M + 2]+.
