[C:1](=[S:3])=S.[NH2:4][C:5]1[CH:13]=[CH:12][C:8]([C:9]([OH:11])=[O:10])=[CH:7][CH:6]=1.C(N(CC)CC)C.II.Cl.S([O-])([O-])=O.[Na+].[Na+]>C(OCC)(=O)C.O1CCCC1.O>[N:4]([C:5]1[CH:13]=[CH:12][C:8]([C:9]([OH:11])=[O:10])=[CH:7][CH:6]=1)=[C:1]=[S:3]Carbon disulfide (0.66 mL, 11 mmol) was added to a mixture comprising 4-aminobenzoic acid (0.50 g, 3.6 mmol), tetrahydrofuran (2.5 mL), water (2.5 mL) and triethylamine (1.3 mL, 9.1 mmol), followed by stirring at room temperature for 24 hours. To the obtained reaction mixture, a tetrahydrofuran (2.5 mL) solution of iodine (1.0 g, 4.0 mmol) was dropwise added over a period of 5 minutes at 0° C., followed by stirring at 0° C. for further two hours. Thereafter, 1M hydrochloric acid (3.6 mL) and sodium sulfite (91 mg, 0.72 mmol) were added and stirred. Then, ethyl acetate (15 mL) was added, and the organic layer was separated and concentrated under reduced pressure to dryness. To the residue, ethyl acetate (5 mL) and hexane (5 mL) were added and thoroughly mixed, and then, the insoluble matter was collected by filtration to obtain 4-isothiocyanatobenzoic acid as a colorless solid (0.65 g, yield: 100%, HPLC purity: 92%, HPLC retention time: 3.7 min). LC-MS ES-178 (retention time: 4.0 min, condition 1).
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