General procedure for the synthesis of methyl 4-amino-2-bromobenzoate from methyl 2-bromo-4-nitrobenzoate: To a solution of methyl 2-bromo-4-nitrobenzoate (4.5 g, 17.0 mmol) in ethyl acetate (100 mL) was added stannous chloride dihydrate (38.3 g, 0.17 mol). The reaction mixture was heated to reflux and stirred for 4 hours. Upon completion of the reaction, the mixture was poured into a mixture of saturated sodium bicarbonate solution (500 mL) and ethyl acetate (370 mL). The organic layer was separated, washed with saturated brine (300 mL) and dried with anhydrous magnesium sulfate. After concentration under reduced pressure, the residue was purified by silica gel column chromatography to afford methyl 4-amino-2-bromobenzoate as a solid (3.68 g, 94.2% yield).1H NMR (400 MHz, CDCl3): δ 7.75 (d, J = 8.5 Hz, 1H), 6.92 (d, J = 2.2 Hz, 1H), 6.57 (dd, J = 8.5,2.2 Hz, 1H), 4.04 (brs, 2H) and 3.86 (s, 3H) ppm; melting point: 96-98 °C.
