[NH2:1][C:2]1[S:6][C:5]([SH:7])=[N:4][C:3]=1[C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1.[C:14](O)([CH3:17])([CH3:16])[CH3:15].S(=O)(=O)(O)O.C(=O)(O)[O-].[Na+]>O>[NH2:1][C:2]1[S:6][C:5]([S:7][C:14]([CH3:17])([CH3:16])[CH3:15])=[N:4][C:3]=1[C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1To a suspension of 5-amino-2-mercapto-4-phenylthiazole (210 mg, 1.01 mmol) in water (1.0 ml) and tert-butanol (82 mg, 1.1 mmol) was added concentrated sulfuric acid (3.0 ml) with cooling to ca. 20° C. After 1.5 hr at ambient temperature a further portion of tert-butanol in water (300 μl, 1.0 M, 300 μmol) was added. After 1.5 hr the mixture was poured into excess aqueous sodium bicarbonate and extracted three times into dichloromethane (total 120 ml). The combined organic phases were washed with brine, dried over sodium sulfate, filtered and concentrated in vacuo. Flash chromatography on silica gel (ethyl acetate/hexanes) yielded 5-amino-2-(tert-butylsulfanyl)-4-phenylthiazole (220 mg, 82%).
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