Methyl p-toluenesulfonate → 2-(Methylsulfanyl)-1,3-benzothiazol-5-ol

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Reaction Steps

To a 250 mL flask was added 2-mercapto-5-methoxybenzothiazole (5.1 g, 26 mmol), MeCN (63 mL), methyl p-toluenesulfonate (4.8 g, 26 mmol) and TEA (4.4 mL, 31 mmol). After stirring 16 h at ambient temperature, the solution was concentrated under reduced pressure. The crude material was diluted with EtOAc (200 mL), washed with water (2×75 mL), dried over Na2SO4, filtered, and concentrated. The resulting viscous oil was dissolved in DCM (40 mL), and transferred to an argon-purged 250 mL flask. The solution was cooled to −78° C. prior to the addition of a 1.0 M BBr3 solution in DCM (64 mL). The reaction suspension was allowed to warm to room temperature. After 16 h the reaction solution was cooled to −78° C. and quenched by addition of MeOH (100 mL). The resulting precipitates were isolated by vacuum filtration to yield 5-hydroxy-2-methylthio-benzothiazole (3.9 g, 76%) as a white solid.

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