Hydrochloric Acid → 5-chloro-4-(1-methyl-1H-pyrazol-5-yl)thiophene-2-carboxylic acid

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Reaction Steps

To a 250 mL round-bottomed flask was added methyl 5-chloro-4-(1-methyl-1H-pyrazol-5-yl)-2-thiophenecarboxylate (4.4 g, 17.14 mmol) and sodium hydroxide (28.6 ml, 171 mmol) in tetrahydrofuran (THF) (50 ml) and MeOH (50 mL). The reaction solution was stirred at RT for 12 h and then made acidic (pH ˜2) with 2.5 M HCl and extracted with DCM. The organic layer was separated, dried (Na2SO4) and concentrated to an off-white solid (4.2 g, 94%) which was used directly without further purification: LCMS (ES) m/z 243 (M+H)+.

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