Methyl 3-amino-2-[(tert-butoxycarbonyl)amino]benzoate → 2,3-Diaminobenzoic acid methyl ester

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Reaction Steps

Methyl 3-amino-2-[(tert-butoxycarbonyl)amino]benzoate (61.8 g, 232 mmol) was added to trifluoroacetic acid (250 mL), and the mixture was stirred at room temperature for 3 hr. Trifluoroacetic acid was evaporated in vacuo, and the resulting solid was suspended in ethyl acetate (200 mL), collected by filtration and washed with ethyl acetate (50 mL). The solid was partitioned between ethyl acetate (300 mL) and saturated aqueous sodium hydrogen carbonate (400 mL), and the aqueous layer was separated and extracted with ethyl acetate (300 mL). The combined organic layer was washed with water (300 mL×2) and concentrated in vacuo to give the title compound (24.6 g, 148 mmol, 64%) as a brown solid. The filtrate described above was concentrated in vacuo, and the resulting solid was collected by filtration and washed with ethyl acetate. The filtrate was concentrated in vacuo, and the resulting solid was collected by filtration and washed with diethyl ether. The combined solid was partitioned between ethyl acetate (100 mL) and saturated aqueous sodium hydrogen carbonate (100 mL), and the aqueous layer was separated and extracted with ethyl, acetate). The combined organic layer was washed with water and brine, dried over anhydrous sodium sulfate and concentrated in vacuo to give the title compound (8.29 g, 49.9 mmol, 22%) as a brown solid. Total amount: 32.9 g, 198 mmol, 85%.

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