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

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A 5-L, four neck round bottom flask equipped with overhead air stirrer, positive pressure nitrogen inlet, thermocouple, and addition funnel was charged with ethyl 3-tert-butyl-1-methyl-1H-pyrazole-5-carboxylate (250 g, 1.19 mol) in dichloromethane (2.5 L). The resulting solution was cooled to 10° C. with a wet-ice bath. Sulfuryl chloride (149 mL, 1.49 mol) was added via addition funnel at such which maintained the temperature between 21-31° C. The resulting mixture was then stirred for 2 h at room temperature. A separate 12-L, four neck flask equipped with overhead air stirrer and thermocouple was charged H2O (3.75 L) and cooled to 10° C. This mixture was then added via addition funnel, while maintaining the temperature below 32° C. and the resulting mixture was stirred for 30 min. The layers were separated, the aqueous layer was extracted with dichloromethane (2×1 L). The organic layer was carefully washed with NaHCO3 (saturated, 2×2 L), brine (1.25 L), dried over Na2SO4, filtered, and evaporated to yield ethyl 3-tert-butyl-4-chloro-1-methyl-1H-pyrazole-5-carboxylate as a white solid. 1H NMR (CHLOROFORM-d) δ: 4.39 (q, J=7.1 Hz, 2H), 4.07 (s, 3H), 1.29-1.49 (m, 12H)

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