Boron tribromide → 5-(3-amino-2-hydroxy-phenyl)-1,2,4-trimethyl-1H-pyrrole-3-carboxylic acid ethyl ester hydrobromide

5-(3-Amino-2-methoxy-phenyl)-1,2,4-trimethyl-1H-pyrrole-3-carboxylic acid ethyl ester 6g (210 mg, 0.69 mmol) was dissolved in 5 mL of dichloromethane followed by addition of boron tribromide (1.39 mL, 2.78 mmol). The reaction mixture was reacted at room temperature for 0.5 hours and monitored by TLC until the disappearance of the starting materials. The reaction was quenched with methanol, and the mixture was concentrated under reduced pressure followed by addition of 50 mL of ethyl acetate and 15 mL of saturated aqueous sodium bicarbonate. The mixture was mixed well and the layers were separated. The organic layer was washed with saturated brine, dried over anhydrous magnesium sulfate, filtered to remove the drying agent and concentrated under reduced pressure to obtain the title compound 5-(3-amino-2-hydroxy-phenyl)-1,2,4-trimethyl-1H-pyrrole-3-carboxylic acid ethyl ester hydrobromide 6h (165 mg, yield 82.5%) as a white solid.