Methanol → Methyl 4-bromo-5-methylthiothiophene-2-carboxylate

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Reaction Steps

To a stirred solution of 4-bromo-5-methylthiothiophene-2-carboxylic acid (87 mmol), prepared according to the procedure of Kleemann, et al., EP 0676395A2, in dry methanol (750 mL) was added thionyl chloride (7 mL, 96 mmol) dropwise. After stirring for 10 min at room temperature, the solution was heated to reflux and stirred 7.5 h. The solution was cooled and the solvents were removed in vacuo. The resulting solid was dissolved in dichloromethane (1500 mL) and washed with saturated sodium bicarbonate (2×300 mL), water (300 mL), saturated brine (300 mL), and dried over anhydrous sodium sulfate. The solvents were removed in vacuo. The resulting solid was recrystallized twice from hexane/ethyl acetate to give methyl 4-bromo-5-methylthiothiophene-2-carboxylate (4.4 g, 19%). 1H-NMR (CDCl3, 400 MHz) δ7.66 (s, 1H), 3.90 (s, 3H), 2.60 (s, 3H).

Provenance & Evidence