Boron tribromide → 4-(3-Amino-2-hydroxy-phenyl)-thiophene-2-carboxylic acid hydrobromide
Reaction equation
Br.[NH2:2][C:3]1[C:4]([O:17]C)=[C:5]([C:9]2[CH:10]=[C:11]([C:14]([OH:16])=[O:15])[S:12][CH:13]=2)[CH:6]=[CH:7][CH:8]=1.B(Br)(Br)[Br:20]>ClCCl>[BrH:20].[NH2:2][C:3]1[C:4]([OH:17])=[C:5]([C:9]2[CH:10]=[C:11]([C:14]([OH:16])=[O:15])[S:12][CH:13]=2)[CH:6]=[CH:7][CH:8]=1Participants
4
Procedure
4-(3-Amino-2-methoxy-phenyl)-thiophene-2-carboxylic acid hydrobromide 51b (360 mg, 1.45 mmol) was dissolved in 5 mL of dichloromethane followed by dropwise addition of boron tribromide (2.8 mL, 5.6 mmol). The reaction mixture was reacted at room temperature for 4.5 hours. The reaction was monitored by TLC until the disappearance of the starting materials and quenched with 5 mL of methanol. The mixture was concentrated under reduced pressure. The residue was diluted with 10 mL of ethyl acetate and stirred for 0.5 hours. The mixture was filtered and the filter cake was dried to obtain the title compound 4-(3-amino-2-hydroxy-phenyl)-thiophene-2-carboxylic acid hydrobromide 51c (80 mg, yield 17.5%) as a grey solid.