Hydrochloric Acid → 4-(Isopropylthio)-3-methylbenzoic acid

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Butyllithium (16 mL of 1.6 M, 25.6 mmol) was added dropwise to a mixture of 4-bromo-3-methyl-benzoic acid (2.5 g, 11.6 mmol) and THF (63 mL) at −78° C. The reaction mixture was allowed to stir at −78° C. for 30 minutes before a solution of 2-isopropyldisulfanylpropane (1.7 g, 11.6 mmol) in THF (2 mL) was added dropwise. The mixture was allowed to stir at −78° C. for 30 minutes, then 30 minutes at room temperature. The reaction mixture was then diluted with 1M aqueous sodium hydroxide (100 mL). The organic layer was discarded and the aqueous layer was acidified with 4M aqueous hydrochloric acid. The aqueous layer was then extracted 3 times with ethyl acetate. The combined extracts were dried over sodium sulfate and concentrated in vacuo. The crude material was purified by silica gel column chromatography using a gradient of 0-5% MeOH in dichloromethane to give 4-(isopropylthio)-3-methylbenzoic acid (873 mg, 18%). MS m/z calc. 210.3. found 211.2 (M+1)+. Retention time: 2.32 minutes (3 min run).

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