Ammonium Chloride → Tert-butyl 4-amino-2-fluorobenzoate

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A solution of 1.109 g (20.73 mmol, 10 eq.) of ammonium chloride in 6.25 ml of ethanol and 3.125 ml of water was heated to 95° C., and 500 mg (2.07 mmol) of tert-butyl 2-fluoro-4-nitrobenzoate were added. 347 mg (6.22 mmol, 3 eq.) of iron powder were added in small portions over 1 h. The reaction mixture was then stirred at 95° C. for 30 min, and the hot mixture was then filtered through kieselguhr. The filter cake was washed with ethanol and the filtrate was freed from ethanol under reduced pressure. The aqueous phase was extracted three times with in each case 20 ml of diethyl ether. The combined organic phases were washed with saturated aqueous sodium chloride solution, dried (sodium sulphate), filtered and concentrated under reduced pressure. The crude product was purified by normal phase chromatography (mobile phase: cyclohexane/ethyl acetate 30%-50% mixtures). Yield: 280 mg (51% of theory).

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