General procedure for the synthesis of 3-amino-4-chlorophenylboronic acid pinacol ester from 2-(4-chloro-3-nitrophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane: Compound 1 (55.0 g, 190 mmol) was placed in a three-necked flask, and ethanol (500 mL), water (100 mL), and ammonium chloride (20.4 g, 390 mmol) were sequentially added. 390 mmol). Iron powder (49 g, 880 mmol) was added slowly with stirring at room temperature. The reaction mixture was heated to 105 °C and refluxed for 2 hours. After completion of the reaction, it was cooled to room temperature and filtered through diatomaceous earth to remove excess iron powder. Ethanol was removed by distillation under reduced pressure and water (100 mL) and saturated aqueous sodium bicarbonate solution (150 mL) were added. Extracted with ethyl acetate (200 mL x 3), the organic phases were combined, washed sequentially with saturated aqueous sodium bicarbonate (150 mL) and saturated brine (150 mL), dried over anhydrous sodium sulfate and filtered. The filtrate was rotary evaporated to dryness to give compound 2 (45.5 g, 179 mmol, 94% yield) in yellow liquid form.
