Triethylamine → 5-(Ethylthio)carbonyloxy-1-methylpyrazol-4-yl 3-(methoxycarbonyl)-2-methyl-4-(methylsulfonyl)phenyl ketone

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Reaction Steps

5-Hydroxy-1-methylpyrazol-4-yl 3-(methoxycarbonyl)-2-methyl-4-(methylsulfonyl)phenyl ketone (290 mg, 0.82 mmol) was dissolved in dry tetrahydrofuran (15 mL), and triethylamine (166 mg, 1.64 mmol) was added thereto. A solution (4 mL) of 96% S-ethyl chlorothiolformate (107 mg) dissolved in dry tetrahydrofuran was added thereto little by little under cooling with ice water. The reaction mixture was stirred for 90 minutes while the reaction temperature was allowed to warm to room temperature. The reaction solution was poured into ice water, followed by extraction with ethyl acetate. The extract was dried over anhydrous sodium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (n-hexane:ethyl acetate=6:4) to obtain the desired product as an amorphous solid (202 mg, 0.46 mmol) (yield: 56%).

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