[NH2:1][C:2]1[CH:10]=[CH:9][C:5]([C:6]([OH:8])=[O:7])=[CH:4][CH:3]=1.[S-:11][C:12]#[N:13].[NH4+].BrBr.O>CO>[NH2:1][C:2]1[CH:10]=[CH:9][C:5]([C:6]([OH:8])=[O:7])=[CH:4][C:3]=1[S:11][C:12]#[N:13]4-Aminobenzoic acid (13 g) and ammonium thiocyanate (6.9 g) were suspended in methanol (200 ml) and cooled at −15° C. on an ice bath. A methanol solution (40 ml) containing bromine (4.7 ml) was added slowly dropwise thereto. The mixture was warmed to room temperature and stirred for 2 hours, iced water (500 ml) was added thereto, and precipitated crystals were collected by filtration and washed with water and n-hexane. The product was dried under reduced pressure to give 4-amino-3-thiocyanatobenzoic acid (9.4 g, Y.:53%) as white crystals.
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