Sulfuryl chloride → ethyl 3-tert-butyl-4-chloro-1-methyl-1H-pyrazole-5-carboxylate

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Reaction Steps

To a solution of 5-tert-butyl-2-methyl-pyrazole-3-carboxylic acid ethyl ester (2.10 g, 10.0 mmol) in 25 mL of DCM was added sulfuryl chloride (1.05 mL, 13.0 mmol) slowly under Ar. After stirring at room temperature for 3 h under Ar, the resulting mixture was treated with DCM (30 mL), washed with ice H2O, saturated aqueous NaHCO3 and brine, and dried with Na2SO4. Removal of the solvent under reduced pressure yielded the title compound as a white solid. 1H-NMR (400 MHz, CDCl3) δ: 4.40 (q, J=7.2 Hz, 2H), 4.07 (s, 3H), 1.42 (t, J=7.2 Hz, 3H), 1.40 (s, 9H). Mass Spectrum (LCMS, ESI pos.) Calculated For C11H17ClN2O2: 245.1 (M+H). Measured: 245.1.

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