4-Toluenesulfonyl chloride → toluene-4-sulfonic acid 5-[(S)-l-hydroxyethyl]-1H-pyrazol-3-yl ester

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Reaction Steps

To a stirred solution of (S)-3-hydroxy-5-(1-hydroxyethyl)-1H-pyrazole (0.5056 g, 3.95 mmol) in anhydrous dichloromethane (20 ml) under nitrogen was added p-toluenesulfonyl chloride (0.8276 g, 4.34 mmol) then, dropwise, triethylamine (0.66 ml, 4.74 mmol). The mixture was stirred at room temperature for 3 h, then washed with saturated NaCl (15 ml). The aqueous layer was further extracted with dichloromethane (2×25 ml) and the combined organic extracts were dried (NaSO4) and evaporated in vacuo. The residue was purified by flash chromatography (silica gel, 5% MeOH/CH2Cl2) to give 0.8770 g (79%) of the title compound as an orange oil: 1H NMR (400 MHz, DMSO-d6) δ 1.31 (3H, d, J=6.5 Hz), 2.42 (3H, s), 4.67 (1H, m), 5.40 (1H, d, J=5.1 Hz), 5.79 (1H, d, J=2.1 Hz), 7.47 (2H, d, J=8.1 Hz), 7.77 (2H, d, J=8.4 Hz), 12.48 (1H, s); MS (ES+) m/e 283 [M+H]+, 265 [M−OH]+.

Provenance & Evidence