Thionyl Chloride → 2-Bromo-6-[(3-fluoro-4-methoxybenzoyl)amino]-4-methoxyphenyl 3-fluoro-4-methoxybenzoate

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Reaction Steps

A mixture of 3-fluoro-4-methoxybenzoic acid (39.0 g, 229 mmol), thionyl chloride (100 mL), and N,N-dimethylformamide (0.5 mL) was refluxed for 1 h. The volatiles were removed under vacuum. The solids were taken in benzene (twice) and the volatiles were removed under vacuum. The residue was dissolved in CH2Cl2 (100 mL) and added into a cold (0° C.) mixture (mechanically stirred) of 2-amino-6-bromo-4-methoxyphenol (20.0 g, 91.7 mmol) and CH2Cl2 (150 mL). Anhydrous pyridine (37.0 mL, 468.5 mmol) was added dropwise into the new mixture. During the pyridine addition a precipitate was formed. The mixture was stirred for 30 min and then ethyl ether (250 mL) was added. The precipitated solids were filtered off and washed with ethyl ether. The solids were taken in water and stirred for 20 min. The solids were then filtered off and dried to give an off-white solid (46.5 g, 97% yield, m.p. 184-186° C.); MS m/e 520 (M−H)+.

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